Can a 12 Volt Battery Be Bad if It Reads Over 12 Volts?

THE BASICS ON BATTERIES
*Important Items Highlighted/ Colored

Starting time things first. A 12-volt bombardment is not a 12-volt battery. Twelve volts is just a nominal, convenient term used to distinguish 1 battery from another. A fully-charged 12-volt battery, allowed to "rest" for a few hours (or days) with no load existence fatigued from it (or charge going to it), will rest out its charge and measure about 12.6 volts between terminals.

When a bombardment reads merely 12 volts under the above weather condition, it's almost fully depleted. Actually, if a battery'southward resting voltage is only 12.0 to 12.ane it means only 20 to 25% of its useful energy remains. It's either a goner or it has been deep cycled, and a battery can simply be deep-cycled a express number of times before it is indeed dead.

12-volt batteries supply useful energy only through a limited range — from over 14 volts (when fully charged and unrested) downwards to 10.5 volts in apply/under load (when lights dim, pumps groan and TV pictures get pocket-sized). No 12-volt battery will remain at over 14 volts for more than than seconds unless it's being charged. The lowest limit is 10.v volts (used in testing) and obviously unsatisfactory in applied use. Experienced RVers attempt to use no more than than 20% to 50% of the energy available in a battery before recharging. That ways they never let resting voltage get below 12.5. They never use more than than 50% before recharging (resting volts of 12.3) except in an emergency. They know that, if resting voltage ever reaches 12.one, they have deep-discharged one cycle and that a battery is good for merely so many cycles (from as depression as 20 in an automotive bombardment to 180 in a golf cart bombardment, with the typical RV/marine battery practiced for no more than 30).

Watts = Volts ten Amps example: 60W = 12V x A and 60 ÷ 12 = v amps

BATTERY CHARGING VOLTAGE
Charging voltage is unlike. Some more basics: If you read articles on how electricity flows, y'all come across comparisons every bit to how water flows. This is okay up to a bespeak, but water also flows by gravity. Electricity doesn't, information technology has to be "pushed" (just as water has to sometimes be pumped).

Yous have to have more "juice" at one terminate of a wire than you need at the output or electricity won't flow. The wire you pump electricity through and the connections in the lines resist the flow. Yous have to overpower it. Similarly, batteries have an inherent resistance to take a charge because of their chemical makeup. Yous take to force more electricity into a battery than it would like to accept or it won't be fully charged. To charge a standard 12-volt battery, you have to bring it up to in a higher place fourteen volts (amount varies with the type of bombardment).

When checking the batteries, (at rest) utilise these "Voltage Landmarks".

12.6 volts = 100%
12.5 volts = 70%
12.3 volts = 50%
eleven.iv volts = 20%

The typical moisture-cell battery (lead plates in a mixture of sulfuric acid and water) needs to exist charged upward to about fourteen.+ volts in order to adequately distribute those funny little things chosen electrons through the plates. One time that'due south washed, the battery can rest. As it does, the electrons distribute themselves and eventually balance out at 12.6 volts (more or less, depending on the blazon bombardment and its condition). This is your starting point.

MORE AMPS AND VOLTS
Equally mentioned before, you should only describe a bombardment downward to most 12.3 volts before recharging . Obviously, there'southward more to it than that. Amperes are the measure of bodily power available. They're usually converted to amp(ere) hours (AH). Think of information technology every bit the amount of (nominal) 12-volt power you can draw out of a bombardment for a sure amount of time. It's not simply 3-tenths of a volt. It's 12 (nominal) volts for a sure amount of time. The three-tenths stuff is nix more than a difference in measurement — like the departure between 3-fourths of a tank of gas and a half tank.

Await at voltage every bit two things: First, a force that pushes electrons — Second, every bit a handy measurement.

Wait at amperes equally two things: First, a quantity of energy (similar y'all would a gallon of gas) — 2nd, as a handy measurement. From a (nominal again, don't forget) 12-volt tub of energy, you tin extract simply so many amperes of power.

Proceed in mind that the laws of physics preclude y'all from getting more out of something than y'all put into it! Go on in mind that waste (those wires, battery contents and such) prevents y'all from taking out as much as yous put in. Keep in heed that y'all're going to take to put in most x% more electrical power than you use (loftier school physics). A battery bank is similar a "money" bank or checking business relationship — if yous repeatedly take more than out than you put in, you'll eventually be in problem.

More ON Bombardment CHARGING
Not all batteries are the same. Standard wet-jail cell batteries tin can be charged to xiv.+ volts (usually 14.3 only depends on the manufacturer). Gel-jail cell batteries and other sealed batteries should never be charged to more than than almost 14.1 volts (again, may vary depending on manufacturer). And these figures simply pertain when the charger will be asunder as those levels are reached (as with a generator, solar system, portable charger, or engine alternator). As the volts drib (ordinarily downward to near 12.six to 13.3), charging begins again, either manually or through an automated regulator. Note likewise: The maximum charging voltage quoted for gels by the manufacturer is as a sustained voltage, not an intermittent 1. That ways brief over-voltages earlier a regulator shuts off are OK.

Sustained charging, where the batteries are "floated" at a abiding charge (as in the RV converter or with an automatic portable charger) should not be done at more than than xiii.8 volts (and 13.65 makes batteries final longer). It'south supposed to keep the batteries "up" to a reasonable level without undercharging or overcharging them (the assumption being you'll "pinnacle them off" by driving). Unfortunately, many cheap chargers and RV converters don't regulate very well. Overcharging destroys batteries apace. Undercharging destroys batteries as well, but more than subtly equally the bombardment stratifies and volition no longer maintain a charge. In effect, the 100 amp/hour RV battery becomes a 10 amp/60 minutes battery after consistent undercharge. It will read full voltage, just equally soon every bit a minor load is placed on it, it drops to aught. RVers who remain plugged into commercial ability for long periods ofttimes never know this has happened until they unplug, because the converter'due south transformer also supplies ability direct to the RV circuits while information technology's charging the battery — or trying to.

Bombardment EQUALIZING
Sometimes an equalizing charge can correct the higher up state of affairs. Just, don't e'er endeavour to equalize a really sealed wet battery or gel-celled or AGM battery! You've got to be really conscientious when doing this! The bombardment is going to "gas" (bubbling in the cells, hydrogen gas escaping). Information technology shouldn't exist vehement, spewing acid an over the place, just gentle to rapid bubbling but it requires caution. Information technology's normally done by hooking up a manual charger, and so bringing the voltage upward to 14.ane or 14.iii and, instead of stopping as usual, keeping it there, at almost a v-amp charge, for iii to half-dozen hours (until voltage reaches 14.5 to 15). Exercise this with the caps off of a standard battery so you can encounter what'south going on. About three hours is unremarkably normal for one of these equalizing charges.

Follow safety precautions, use safety goggles, plenty of ventilation, etc.

Some battery people recommend equalizing in this fashion every three months (or afterwards five deep cycles). I think the wear and tear on a 12V bombardment from equalizing this often does more than damage than information technology's worth.

Batteries held at 13.8 or so for long periods get lazy and like it there. They need some "equalizing" also. Not as drastic as above, fortunately. If yous bulldoze occasionally, your engine alternator should do information technology (assuming the regulator is prepare properly). So volition a solar electric system or a good, well-regulated independent battery charger. If goose egg else, use the transmission charger once in a while when parked and plugged in, but just bring volts up to fourteen.+ (whatever'south appropriate) and stop there.

Golf Cart Battery
Six volt heavy-duty batteries (like golf carts, etc.) differ. Their heavy plates and other structure features permit periodic equalizing. I recommend the same five amp charge rate, for three to half-dozen hours (until voltage reaches a maximum of sixteen.5) every six months or so. It varies, with some people doing it monthly (which might mean another problem).

BATTERY CHARGE/DISCHARGE RATE
You'll see references in battery books to the proper charge rate. C/10, C/20, etc. Sometimes it can be disruptive. What you need to know is that it means the "fourth dimension" it takes to fully charge a "dead" bombardment at a certain amp rate. For case: A 105AH battery will fully recharge (from dead) in most x hours at about 10 amps of charge (C/x) or about 20 hours at 5 amps of charge (C/20). Faster charge rates, like C/5 or C/8 shouldn't be used with most batteries because the high amperage required for such a fast accuse damages the battery. C/5 on a dead 105 AH battery requires pounding in over twenty amps. (This is sufficient reason to stay away from fast-chargers in service stations where a gigantic amount of amps are pummeling your battery when they "charge" (destroy) it in 20 minutes. And when y'all buy a battery off the shelf, don't let the guy "put information technology on a charger for merely a few minutes" or it will exist damaged earlier y'all ever use information technology.

BATTERY TROUBLESHOOTING AND Battery TESTING
Don't just replace batteries and keep on trucking! Notice out what went wrong outset. Is the converter working? Voltage too high? As well low? Is it connected to the battery? Fuse blown? Wire broken? Contacts cruddy? Kill switch on motor domicile on or off (whichever is appropriate — and the wrong position a common fault amongst motor homers)? How many times take you deep-cycled? Curt in the system? Been hooked up a long time? Automotive regulator/alternator OK? (More later.)

Measuring, metering, testing and troubleshooting require only a few tools and basic knowledge. Much of it is common sense, requiring no tools. Practise non ever depend on the red/xanthous/green idiot meter installed in most RV's. Become a digital meter. You demand a digital meter to accurately read battery voltage to tenths of a volt. Y'all should have an Analog (needle face) meter also. You can't tell the deviation between bombardment voltages with an analog with great accuracy, but they are better in some ways (because information technology'southward easier to encounter rapid changes) than digital meters for reading fluctuations. (Much more than later.)

Get a 12-volt troubleshooting light/examination lamp from any auto store cheap or brand your own. (Meters will indicate voltage even if at that place's simply one strand left in a wire. Examination lamps won't light if in that location's not enough wire to carry the load.)

Go a decent hydrometer if you lot have moisture-cell batteries and tin can remove the caps. Don't become a cheapie with colored, floating balls. Learn how to read a hydrometer.

Battery Testing
Tin can exist washed in more than one way: The most authentic method of measurement is using a hydrometer to measure specific gravity and using a D.C. voltmeter to get the battery voltage.
A quality load tester may exist a practiced purchase if you lot demand to examination sealed12 volt batteries.
For any of these methods, you must first fully accuse the battery and then remove the surface charge. If the battery has been sitting at to the lowest degree several hours (I prefer at to the lowest degree 12 hours) you may brainstorm testing. To remove surface charge the battery must be discharged for several minutes. Using a headlight (loftier axle) will exercise the play a joke on. After turning off the calorie-free you are ready to examination the battery.

State of Accuse	Specific Gravity	Voltage
		12V	6V
100%	1.265	12.vii	half dozen.3
75%	i.225	12.4	6.2
50%	ane.190	12.ii	half dozen.1
25%	1.155	12.0	6.0
Discharged	ane.120	eleven.9	6.0

Specific Gravity: Full charge SG will run from near 1.260 in an auto battery to nearly one.275 in a golf cart. Loftier SG (more than acid) allows more juice (current) to be drawn–but only upwardly to a point; then the battery deteriorates–fast. Golf game cart plates are made to handle this, RV/Marine somewhat, automotive not at all. Don't try to get more AH by adding acrid (or vinegar instead of distilled water), the bombardment will just dice sooner.

MORE ON SPECIFIC GRAVITY–and checking resting voltage
If you accept standard batteries, get a good hydrometer (not i with colored floating balls in it). Information technology must have a tube inside with SG increments clearly marked and a built in thermometer with a temperature correction chart. It'south unlikely that a new battery, even freshly charged, volition give more 80% of its rated output. You'll get more than after it's been used and recharged a few times–unless it'due south faulty. Check SG anyway to found a "baseline" reading.

Await especially for differences between cells. A variation of .050 between whatever means a possible problem. This is afterwards it's charged and bubbled a scrap to mix chemicals thoroughly. If it's a new battery and this happens, take information technology back. If sometime, plan on replacing it soon. It probably has a stratified/shorted cell. Initially, in that location's no demand in checking SG until a bombardment reaches about seventy% of full charge and is bubbling/gassing slightly (not boiling like a coffee pot). So, have readings once each hour and write them downwardly. When three successive readings are alike, the battery is every bit charged as it will get. Record readings for each cell and battery. Disconnect battery from any accuse or load and leave information technology overnight (24 hours is better). Check SG once again. Readings may be a bit lower, merely should be consistent. Record these equally your new baseline: your normal, total charge, resting values.

Do this once more later on two weeks or a month of use. Readings may exist slightly higher, but again, should be consistent. If the batteries have been constantly overcharged or undercharged, it will show upward here. Y'all should have checked that your battery charger was set properly before starting all this, but if you get abnormal readings bank check that your charger is regulating properly (see later). If you lot take to add water this soon, you lot are nearly definitely overcharging. Once you lot've done the above tests, you shouldn't take to do it more twice a year unless yous detect a problem. Y'all should check water level almost once a month. Ideally, you lot shouldn't accept to add together water more than two to four times a year. More than that probably indicates overcharging.

Using a Hydrometer Without Making a Mess

Stick it in a cell until it simply rests on summit of the plates. Eject in and out a few times–gently, don't splatter. And then fill until the inner tube floats. Too petty and it volition rest on bottom of hydrometer. Also much and it volition striking the height. In either case, you'll get simulated readings. Don't remove the matter from the jail cell to read it, yous'll only drip acrid all over. Take your reading and write it downwards. Read at the fluid level, non at the slight curvature where the fluid touches the inner tube. (Before moving to the next cell, don't forget to squirt the acrid dorsum in.) Notation temperature on thermometer and correct reading as indicated. Note, again, that all readings for a battery should be inside .050 of each other. Proceed in mind you might have a cheap or faulty hydrometer. El cheapos take a paper SG scale in the tube that slips up and downwards.

Load testing is withal another way of testing a bombardment. Load exam removes amps from a battery much similar starting an engine would. A load tester tin be purchased at near machine parts stores. Some battery companies label their battery with the amp load for testing. This number is usually 1/2 of the CCA rating. For example, a 500CCA battery would load test at 250 amps for xv seconds. A load examination can just be performed if the battery is near or at full accuse.

Hydrometer readings should not vary more than .05 differences betwixt cells.

Digital Voltmeters should read equally the voltage is shown in this document. The sealed AGM and Gel-Cell bombardment voltage (full charged) will be slightly college in the 12.8 to 12.9 ranges. If you have voltage readings in the x.5 volts range on a charged battery, that typically indicates a shorted cell.

If you take a maintenance free wet jail cell, the only ways to examination are voltmeter and load test. Whatsoever of the maintenance complimentary type batteries that have a built in hydrometer(black/dark-green window) will tell you the condition of 1 cell of 6. Y'all may go a good reading from 1 cell but have a problem with other cells in the battery.

MAINTENANCE

Maintenance is earth-shaking. Crud on top of a bombardment provides a path between poles. It'due south a "short." Ane most people never notice, but information technology uses energy constantly.You don't need to slop baking soda all over. Oft but a spray 'n wipe with household cleaner is all that'southward needed.

• Corrosion will build up. Some-times y'all can't even see it. Take contacts apart and clean them. (Now is when you might use blistering soda, but don't let information technology get in the cells.) Done in one case or twice a twelvemonth, it's fast and like shooting fish in a barrel.
• Earlier putting things back together, glaze all surfaces (thinly) with silicone dielectric grease. That'due south before, non subsequently. Yous won't accomplish a thing by smearing grease on top of corrosion.
• Never use red battery spray. It but makes things worse. The ruby/green felt, noncorrosive washers are okay.
• Label or colour-code cable and wire ends. Make a diagram. If you lot don't, you'll just hook things up wrong.

MORE DETAILS ON BATTERIES (More often than not GEL CELLS and AGM)
Much of the aforementioned material applies: All batteries need to exist maintained. All batteries need to be kept charged — only not overcharged or undercharged. All need clean connections and skilful, stout cablevision and wire of the proper size. No battery should be routinely deep-cycled. Of most importance, charging needs to be well regulated.

And here'due south where the difference between gels, AGMs and regular, moisture-cell batteries starts to show up seriously.

• Wet jail cell (flooded) batteries: Suspended plates, usually with some grade of separators (then plates don't bear upon each other) are immersed in liquid electrolyte. These may be charged, merely as a starter battery, which makes things a lot simpler.
• Gel batteries: Plates are suspended in a thick gelled electrolyte that insures stability and eliminates voids or "air pockets" at the plates. The best gels are those by "East Penn Mfg." (under "SeaGel," Prevailer" and other labels — simply the East Penn proper noun will appear somewhere). Competitors are lite weights. Gels are seldom charged to more than xiv.1 volts initial (bulk) charge and 13.eight (thirteen.65 is better) as a "float" charge (see later).
• AGM (Absorbed Drinking glass Mat) batteries: A dense fiber matting between the plates and a liquid electrolyte provide
  similar features to gel batteries simply are much more than rugged since they were designed for employ in aircraft and rough terrain vehicles. The best AGMs are those made past "Concorde" (ordinarily under the "Lifeline" characterization merely Concorde will appear somewhere). AGMs (similar gels) are very sensitive to overcharge. 14.38 volts is recommended for the initial (bulk) charge and 13.38 every bit a "float" accuse.

Pros and Cons:

Standard, erstwhile-timey flooded batteries are cheap (initially). They'll do the chore (golf carts or similar better than RV/Marine stuff). See remarks elsewhere. They volition vent gas and fluid, merely it can be replenished with distilled h2o. They require a lot of care.

Gells and AGMs tin do a meliorate job and last longer, Simply also require special intendance. They're rather expensive initially (but my six gels are in their tenth twelvemonth, equally good as new, and the toll nets out to less than standard batteries). However, they are very carefully charged and that requires an expensive charger/regulator. Gels and AGMs don't need a lot of maintenance and cleaning (other than a quick spray and wipe from a household cleaner) UNLESS you do something stupid and overcharge them. They won't spill acid, are very shock resistant, don't pass gas (pun intended) unless seriously overcharged, accept a VERY low self-discharge rate (nice when the RV is in storage) and have a very long bike life.

I've used golf cart batteries, regular batteries and gels. Equally I'll repeat with more item elsewhere, golf carts and similar batteries are, all things considered, the best solution. Were I to take to supersede my batteries today (they're in the living compartment in a small-scale RV), I'd get with AGM. In a bigger RV, I'd go with golf cart or fork lift batteries.

You should never charge a gel battery to more than than xiv.1 volts (or to more than the voltage specified past the manufacturer) before the regulator shuts off the charger except for very brief periods. Then, every bit a battery is "floated" (kept on the charger with a accuse practical to keep it up to a reasonable level), information technology should never exceed 13.8 volts (better, for long life is a maximum of 13.65 volts). Again, though, yous don't float the battery permanently. You occasionally bring it up to 14.+ (this is EZ with a solar regulator or meliorate quality battery charger that will perform regulating tasks often and automatically. (more later.)AGMs are charged similarly, just with different voltages.

Actually, y'all'd exist foolish to go on (float) any battery at a sustained charge of over 14 volts. You'd simply wear it out prematurely and it would be spewing acid all the time, making a mess. Only with a regular, moisture-cell battery with removable caps, you can add water and make clean up the corrosion. With a gel, or any other (really) sealed battery, yous can't add water. All yous can do is watch the bombardment deteriorate.

Gel batteries and AGMs do have caps, simply don't ever try to remove them. First, you'll violate the warranty. 2d, you'll contaminate the inside. When it dies early, the dealer/factory will know yous did this and will void the warranty. As well, if you overcharge a gel or AGM battery, the factory tin find that, besides. Again, no more warranty.

TEMPERATURE
Temperature is important when charging whatever kind of batteries. A actually hot bombardment (EZ to accomplish if they're sitting out in a cheap, plastic box) will overcharge well earlier the voltages listed before. Keeping batteries "indoors" helps keep them at about an ideal temperature (of nearly 68 to 77ºF). Really, high temperature but becomes a existent problem when the battery is beingness "floated." A 13.8 volt float can hands go a fourteen+ a-whole-bunch bladder at 90º. Temp can also exist a winter problem as batteries try to freeze and their amp hour capacity is reduced by over thirty%.

More ON REGULATING CHARGE
There are only a few RV converter/combination battery chargers that are worth having. Nigh practise an absolutely lousy job and y'all haven't the faintest idea what wild voltage (or lack of) is going to your batteries. Some converter/chargers do work. Cheque yours no affair what kind of battery you use. With the thing operating, and the battery reasonably-well charged, and not much more load on the bombardment than the TV antenna amplifier and reefer brain (RV reefers with a circuit board use 12 volts all the time, just to operate the board), put a digital volt meter across the "firm" battery terminals. Go out it at that place awhile and see if it's holding the batteries to around thirteen.8 volts. (Or is it charging them upwardly to something ridiculous?) (Or is it charging at all?) Some, even fewer, RVs use a separate battery charger (not equally function of a converter). Generally, these are pretty good (and expensive). But check them the same way. It's non at all uncommon to find stock RV battery chargers floating batteries at 14.3 volts or higher. The best chargers regulate in two, three or four stages. First, someday there's sufficient demand, they total charge to 14.+ volts (adjustable by you). Second, they revert to a "bladder" charge of about thirteen.viii (which in proficient chargers is adjustable again). Some have a third, "equalizing" phase, automatic or manual, that should besides be adjustable. (There are some four-stage chargers besides.)

If yous desire to use gel or AGM batteries, you lot must have a good, reliable, user-adaptable regulator and charger. The best way to charge batteries is with a solar electric organization. (Once more, cheque first and concluding with "RV Solar Electric" higher up.) A solar system (if it has a user-adjustable regulator) will let you lot ready the charge cut-off at desired volts. Usually, anytime the solar arrangement achieves that, it will cut off and drop to about 13.1 volts before resuming (some solar regs will back off to a bladder voltage). This gives the batteries a "rest" and keeps them from overcharging. (And, of course, at night, solar systems don't practise anything, and then there'southward a good rest, as well.) For a backup, you can use a generator or commercial power. Make certain your generator (if it has a direct DC 12 volt charging outlet) is gear up to regulate at proper volts! If information technology simply charges through your converter, you'll have checked that to a higher place, merely recheck it with the generator running. Exercise the aforementioned with an independent charger. Many others are bachelor.

Deep Cycling
Permit'south consider something here: One does not deep cycle a battery daily every bit a thing of course. If ane did, then the maximum life of any battery would equal the available number of cycles and no battery would terminal more than vi to 9 months. Ideally, what you need is a battery (batteries) that will provide the power y'all crave without existence cycled (depleted from resting full accuse) past more than twenty to fifty% before being recharged. (If you have a 100AH battery and take no more than 20AH from it before recharging, information technology might last longer than you will.) Unfortunately, this isn't realistic, but you can have up to l% from a battery earlier recharging and still get long life. Unproblematic arithmetic–how many AH used versus how many AH available will tell you how many batteries are needed. Go on in mind that you shouldn't expect but 80% of the manufacturer'south rating. Then a 105AH battery is actually about 84AH. MAX! No battery will give you its rated output in existent life! They're rated down to an end betoken of ten.5 volts. By and then, lights become dim and Telly motion picture small. A Specific Gravity of about one.200 or a voltage of 12.25 to 12.3 means the battery is about 50% discharged. Past the time information technology'south down to xi.8 or 12 volts, it's nearly dead.

AMP Hours and Battery Capacity
What are "Amp Hours"? Amp hours is the amount of current in "Amps" times the number of hours it can evangelize that current.
Example: A 100 amp-hr battery tin evangelize ten amps for 10 hours or 20 amps for 5 hours.
One amp for 100 hours, or any combination, should permit you to charge per unit batteries, simply information technology doesn't work like that. (It's a logarithmic, not a linear, progression.) Farther, chapters, in AH, depends on several things: size, amount/blazon electrolyte, plate thickness, etc. You don't want to investigate all that crap. Of cardinal interest to us are:

Charge per unit of Discharge: Generally 20 hours for automotive, 6 for golf cart and viii for RV/Marine. A 180AH golf cart will, technically, requite you 30 amps for its rated 6 hours, but it will not give threescore amps for three hours. (Has to do with things like heat at this higher rate due to farthermost chemical activity demanded–stuff you don't want to fool with.) It will requite one amp for about 105 hours, though, which is nice to know. Don't just read AH. Read the charts when comparing batteries.

Specific Gravity: Total accuse SG will run from well-nigh 1.260 in an auto battery to about 1.275 in a golf cart. High SG (more acrid) allows more than juice (current) to be fatigued–but but up to a point; then the battery deteriorates–fast. Golf cart plates are fabricated to handle this, RV/Marine somewhat, automotive not at all. Don't try to get more AH by adding acid (or vinegar instead of distilled water), the battery volition just die sooner.

Temperature: Batteries are made to perform best at 77°F. At college temps, they put out more, but die sooner. At lower temps, they put out less, but last longer (unless you lot let them freeze).

CABLES AND CONNECTIONS

Tying the system together is important. No betoken spending a lot of money on batteries and chargers and wiring it up with skimpy junk. Large battery cables can be purchased from San Diego Battery Wholesale. Custom-made cable to your lengths with terminals that match your vehicle is also available.

METERING BATTERIES
If you have maintenance free (maintenance prohibitive) batteries, you can't have fun with a hydrometer. Even if you can use a hydrometer, you don't need to (or want to) exercise information technology more than a couple of times a year. Use the nautical chart (see later on) to go on an accurate check on state of accuse. When taking SG readings, mensurate voltage at the same time. Keep in mind that if a bombardment is charging, voltage will read about ½ to ane volt higher than bodily. Notation that chart voltages (later) are every bit piddling every bit .05 apart. You tin't read that accurately on an analog (punch/needle-faced) meter. You need a digital meter. You don't need to spend over $200 for a professional person model. Meet ads in electronics magazines for reasonably priced meters. Y'all demand a three½ digit" meter (reads to two decimal places) and go ane with at least a 10 amp current measure (20 is meliorate). At present, the all-time deal is a Metex brand #M3800 3½ digit at xx amp capacity for $40 from: JAMECO. (See Sources.) All RVers need one of these anyhow.

When checking the batteries, (at rest) use these "Voltage Landmarks".

12.6 volts = 100%
12.v volts = lxx%
12.3 volts = 50%
xi.iv volts = 20%

More ON UNDERCHARGE AND OVERCHARGE
"Under" results in stratification. "Over" simply eats the plates. Use a regulator to preclude overcharge. When you think a battery is charged, too high a SG means over. Too depression means under. Compare with an authentic voltage check. You should just need to add water a few times a year. More ways bombardment's gassing besides much. You can't tell past feeling the heat of the battery instance any more (better plastics). You lot must put about 10% more energy into a battery than y'all take out (more high school physics–someday free energy is transformed, there must be some loss). An "old" battery can require more. Compare how much yous're putting in versus what you take out and size your system accordingly.

CONNECTING BATTERIES IN PARALLEL, SERIES and Serial-PARALLEL

This is actually simple, just it's amazing how many RVers screw information technology all up!

In serial, volts increase; amps remain the same.
In parallel, amps increase; volts remain the same.

In Parallel: you connect the (+) of one 12vbat to the (+) of the other. Connect (-) of 1 to the (-) of the other. You will so accept yet have a 12volt bat, simply with greater amp hour capacity. This is now an ordinary 12V bat, except that instead of beingness in one "box," it is in two boxes.

In Series: If you were to hook two 12 volt batteries in serial, you'd have 24 volts. Clearly non the matter to practice unless you take a double-decker conversion or custom rig that uses 24Volts. All the same, many RVers employ vi volt (commonly golf cart) batteries. Eastward.Thou., 2 105AH 6v in series would notwithstanding = nigh 105AH but @ a nominal 12V.

Wiring in Serial:
To visualize information technology easier. Start with a simple cake diagram. Two 6V batteries.
On left bat, place (-) at left end, identify (+) on correct stop.
On right bat, place (-) on left terminate, place (+) on correct end.
Describe a line from (+) on left bat to adjacent (-) on right bat.

This is now an ordinary 12V bat, except that instead of being in i "box" with cells all connected in series on the interior, it is in two boxes joined with a cablevision. It'southward however a single 12 volt bat, electrically, then START THINKING OF IT THIS WAY and don't confuse yourself by thinking of it as bat 1 and bat two.

At this point, you've got two unused bat posts — merely like an ordinary 12 volt bat; i neg that goes to chassis ground and ane pos that goes to normal 12V isolator/supply/etc.

Series/Parallel:
Merely echo the serial step to a higher place with two more vi volt bats and yous end upward with two 12V bats. Call up of information technology this manner instead of equally four 6V bats! You now take two (-) unused posts. Connect them together (merely as you would when connecting two ordinary 12V bats in parallel). Repeat for the two unused (+) posts.

It's really quite uncomplicated. The problem many people have is in thinking that this is very complicated. Information technology's not.

The merely time you think of the bats as four 6V bats is when you disconnect them for maintenance and cleaning. And so, only to make absolutely certain that you don't screw up when putting them dorsum together.
Toward this end, information technology's essential that you clearly label posts and cable ends!

% Of Charge	Standard Bombardment Typical Specific Gravity (Subsequently Temperature Correction)	Standard Bombardment Equivalent Resting Volts	Gel-Cell Bombardment Equivalent Resting Volts
100%	1.260 (auto) to 1.280 (industrial)	12.lx-12.75	12.90-13.00
95%	1.255	12.threescore-12.70	12.80
xc%	1.250 (Resting S.G. for standard RV battery.)	12.60-12.65	12.70
85%	i.245 (Aforementioned as in a higher place. No bespeak beingness too picky.)	12.60
lxxx%	1.235-i.240 (We attempt not to belch below this point.)	12.50-12.55	12.60
75%	i.225-1.230 (1.230=minimum SG for a charged battery.)	12.50
70%	1.220 (Annihilation below 1.220 is "poorly" charged.)	12.45	12.l
65%	i.215	12.40
sixty%	1.205	12.35	12.40
55%	1.200	12.thirty
50%	1.190-1.195 (Endeavor to never belch below this point.)	12.25	12.35
45%	i.185	12.xx
twoscore%	1.180	12.xv-12.20	12.25
25%	1.160-one.170 (Dangerously low; battery beingness damaged.)	12.10-12.xv
20%	ane.150 (Cells die soon at this betoken. Farewell-bye battery.)	11.lxxx-12.00	12.15

TROUBLESHOOTING

House Battery: The intent hither is to determine if the bombardment itself is expert, and, in its role as a "business firm" battery, how you can examination information technology, the business firm wiring and charging circuit.

State of affairs: Y'all're charging the battery from any 1 of several sources. Everything has been working fine; simply for no apparent reason and all of a sudden, in that location's no electricity. Don't just beginning taking everything apart! Look around for the obvious. Is the battery still there? Is everything in 1 piece? (A nearby lightning strike can accident the top off.) Are the cables continued? I once spent an hr roaming around with a volt meter only to find I'd but left the negative cablevision off.

Steps:
Connect a volt meter across the battery. It should read some, reasonable voltage even if well discharged (unless it'due south dead). If voltage is acceptable, and assuming things are normal, endeavor moving/twisting the principal cable clamps at the battery. Often, fifty-fifty on a clean-appearing battery, a thin flick of corrosion builds up between post and connector (that you can't see). While the corrosion builds up very gradually, its effect can happen of a sudden.

• Side by side, especially if the connections are unsightly, place the tip of an upright, flat-bladed screwdriver on summit at the circular junction of post and clench and give it a proficient sock with your fist (not a hammer).
• Practice the same with the other post. If bad connections are the problem, the above should allow at least some electricity to menstruation–enough to signal the problem. If the above helps at all, have things apart and clean them.
• If the above doesn't help, beginning disconnect the charging source then disconnect the battery (you might as well go ahead and remove information technology). Earlier you start phiddling with the battery, attach a pair of jumper cables from a known, skillful battery to the RV cables.
• Adhere the (+) cable first. If yous don't let the loose end touch something, there should exist no sparks because there'due south no place for electricity to get (notwithstanding).
• So attach the (-) cable to the "good" battery. (Again, at that place should be no sparks if you don't spiral up.)
• Finally, adhere the terminal (-) finish to the RV cablevision (If the bad battery was removed, sparks at this last connection shouldn't hurt annihilation. This seems like a roundabout manner to practice all this merely in that location'due south a reason for it.
• If there's now electricity in your house, you know you had a discharged battery. Perhaps a bad battery, but not necessarily. Again, earlier you start phiddling with the "bad" battery, you demand to check the charging organisation. The idea here is find out why the battery discharged.
• Run a load (lamp or whatever) to remove the surface charge from your "good" temporary battery. Depending on what kind of battery charger yous have, you lot may need to run the battery down to near 13V or less to become the regulator to allow charging to resume. Keep measuring voltage. When charging resumes, information technology will increase.
• If the voltage doesn't increment, it'south possible that your charging source (converter, generator, solar system) isn't working or the flow is interrupted.

Make the dumb checks starting time:

• Is the converter working? Is the "kill" switch on or off on some motor homes? It's unlikely, because then you should take had a gradual loss, not a sudden one. It is possible though.
• And information technology's possible you have a bad battery AND a bad charging system. RV converters with born bombardment chargers can really confuse you. At that place are two outputs to these things: 1 furnishes 12V direct from the transformer to most firm circuits. The other goes from bombardment charger portion to battery. If you've been plugged into commercial power, the master transformer may have been running everything while the battery charger was not working. Also, the "kill" switch may have been off or fuse from charger blown. (Check the dumb things commencement.)
• Put a volt meter at the battery cease while y'all're doing it. Quite often, a fiddling manipulating will clear things correct up. If not, go back to the source of the charging system with your volt meter. Is in that location ability at the charger output? At the output to battery concluding at solar panels or solar regulator?
• Again, check fuses carefully. You can't tell if a fuse is bad by looking at it, you lot need to measure it with a examination lamp. Call back that a meter can indicate "good" if there's only a slight contact simply a exam lamp won't work if at that place's not enough to carry the load.
• If this also fails, you lot may have to check at the charging source with no battery attached. Information technology's easy with an RV converter, but if you use a solar system or current of air generator you lot may not be able to (some tin exist severely damaged if run without a load). RTFM (Read The F****** Manual)! Our purpose in checking at the source (with or without battery continued) is to see if there's anything in that location.

If there'due south still no voltage, at present starts the onerous process of checking the whole system.

• Practise it logically. Go all the manner to the source first. Disconnect generator, solar panels, whatsoever, from the system. You tin now measure them in functioning without damaging anything (except some wind chargers). If the charger works, you know that you have two long pieces of wire (+) and (-) with a problem somewhere. Don't ignore the (-) wire. It is every bit every bit necessary as the (+). Reconnect charger and battery if necessary.
• Go to some logical halfway point with your volt meter. One way or the other, you'll get voltage (unless you lot missed something at the source). Continue in this manner, roughly going halfway (each time on the dead side). Unless you screw up, yous'll shortly isolate the problem to just a few anxiety of wire. If something hasn't been left unconnected or the wire been cut, you'll usually isolate the problem to a connexion or fuse.
• Look at things, pull on wires to make sure they're really fastened. This is where bad crimped connections show upwards. (I spent an hour helping someone track down a solar organization this way. Every crimped concluding fell autonomously in my hands. He'd crimped them with normal pliers.) Look for corrosion at terminals, simply as at battery cables. Retrieve that just because a converter is buzzing, it doesn't mean the battery charger is working. If working with a solar system, never attempt to put a jumper across the solar (+) and battery (+) to bypass the regulator–you lot'll fry it. However, if you disconnect those wires from the regulator, and then you tin can put them together.

All the to a higher place tin be done with a volt meter or exam lamp. In fact, a test lamp works better at continuity checks, because a volt meter might point power if only one strand of wire is nonetheless connected while a exam lamp won't light if it doesn't accept a excursion heavy enough for the load.

TO CHECK THE Bombardment ITSELF–More ON RESTING VOLTAGE

It tin exist checked with a hydrometer, but a battery can read OK and notwithstanding exist faulty. Here's a good way to check a bombardment. It takes time, but information technology'southward worth it:

• Accuse it fully, preferably with a proficient battery charger or an independent, transmission, automotive charger (you demand one anyway for emergencies). This can have awhile if it's been deep discharged (dead).
• Mensurate voltage. It should be quite high–over 13 volts and fourteen.+ is better. Disconnect the charger. Leave the battery (with nothing connected to it) at least half dozen hours. Overnight or 24 hours is amend.
• Measure voltage again. It should be 12.half dozen volts. If not, even if it's 12.5, it'due south a goner or information technology'south going. If it reads 12.6, it yet might be bad.
• A commercial battery store can check this with a variable load tester. And then tin can you. If the battery is at least a so-called l00AH RV/Marine blazon, information technology should start nearly engines in decent atmospheric condition. Connect a volt meter beyond it. If it doesn't start, leap start it. Run the engine at a nice, fast idle (ane,500 to 2,000 rpm).
• If the voltage rises to over 14 volts in only 4 or 5 minutes, you have a bad bombardment. Due to things we won't dwell on here, the AH chapters has been severely reduced (stratification, deep discharges, etc.). What y'all have is a bombardment that has about a l0AH capacity instead of l00AH. Information technology tests OK considering it has some capacity (might run a lamp a few hours), just not enough. This common problem often drives people basics. Information technology tests OK, it only won't terminal long.
• The same examination works on automobile batteries. They test OK but won't get-go an engine.

BATTERY ISOLATORS

Almost everybody has one. Nigh people never pay attending to them. I do. And I've got mine remoted to a switch on the dash to avoid the [many] problems they can cause. About isolators transport a charge to the batteries automatically. I don't desire to do that. Normally, my solar system keeps the "house" batteries charged but fine. There are times, in bad weather, when I demand to boost the batteries, so when on the road I hit the switch that goes to the charge line to house batteries and the engine alternator charges them in the normal fashion. A cheap, voltmeter on the dash keeps me informed when to shut charging off.

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Source: https://deepcyclebatterystore.com/how-to-maintain-batteries/

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