I was being remiss in not saying with the basics, when discussing batteries. To me this is a cardinal error. Forgive me...
Here is a little something I composed last night before my fingers gave out...
SAFE BATTERY CHARGING
There has been so much hyperbole written about “what's safe” and “what's unsafe” regarding battery charging voltage that my head spins. You need to know what voltage level your batteries are at – at rest, when being charged in earnest, or when they are kicking back on a maintenance level voltage. Without a voltmeter reading, you are driving blind. Personally I won't ride alongside a blindfolded driver.
There is no such thing as a “Plug N Play” battery charger or “total hands-off” battery maintenance charging device – plug in, solar, or vehicle alternator. I wish there was one, I would be first in line to buy one.
Most folks go camping when air temperatures are agreeable and not when it's 0 C or 40 C (320F) or (1040F) outside. Batteries are like people. They like hot food to eat when it's cold (higher voltage charging and storage) and a nice chilled salad (lower voltage) when it's sweltering outside. But let's talk about charging voltage and camping. And for crying-out-loud, let's avoid techno babble.
Deep cycle wet acid batteries are similar enough in behavior (oops Canadians “behaviour”) to engine starting batteries, that for charging purposes we can “assume” they will like and appreciate a fairly similar charging diet (voltage). The difference between the two types of batteries is not great enough to be like trying to feed a cat a chef salad. The two types of batteries will love the following charging advice. Remember now, we are talking about charging not float maintenance where the batteries sit in the shade, do nothing but sip cold Coronas for months-on-end.
The point all the so-called experts forget about or miss (intentionally? To make their own advice seem more important than it really is?) is that hundreds of millions of high powered battery chargers have been already proofed out over the last 80-years. A billion flooded lead acid batteries taken care of with these “chargers”? I don't know the exact number but regardless, it adds up to one hell of an impressive number of batteries.
The Secret? Tah-Dah! It's the alternator in your car, pickup, or motorhome. When you start your rig, the alternator and voltage regular supply charging energy right up to the limit of the alternator's amperage rating. Some alternators have impressive charging ability – 130 amperes and even more than that.
What does this mean? Let's use a motorhome as an example. One modern unit with a 130 amp alternator and a pair of group 27 house batteries. When you start the engine the alternator goes to work. From experience I can tell you a group 27 battery will gobble around 45 amperes of power when it's discharged. So the pair will consume 90 amps. In effect when you start the engine the batteries will have as much power on their plate as they can possibly use. Yes batteries can be overcharged. But your car's alternator is throttled by a control device called a voltage regulator. The voltage only goes “so high” and that's it. The alternator stops charging at this limit. To be blunt, that exact limit in numbers is referred to as the Voltage Regulator Set Point.
So what does all this have to do with the price of dates in Qatar? Think about it. You start your engine, and the house batteries get charged right to the set point of the alternator voltage regulator. There is no self-imposed limit to the charging amperage. The batteries are “offered” the voltage at the set point of the voltage regulator and the batteries automatically consume just so-many amperes. As far as cars go, this magic charging process has been around for 90 years or so.
Keep your thinking hat on please. Do alternators cause fires, boiled batteries, flood, famine and disease? No. Start your engine with depleted house batteries and drive for a dozen hours on the interstate. What do you imagine is happening all those miles? In tens or millions of cars? Over a ninety-year period. Yes alternators can fail and cause problems. I can have a heart-attack and that will pretty much screw-up my plans, too.
Automotive alternators are controlled by a voltage regulator, the brains of the outfit. Most “regulators” operate in the 14.0 to 14.4 volt range. Thats four-tenths of a volt variation. Remember, tens of millions of cars, and perhaps a billion batteries have been baby-sitted with this for more than 90 years. Yes, there were 6-volt systems back then and generators and they operated on half the voltage. Sue me. It's exactly the same thing. Each cell of the battery saw the same voltage back when San Francisco shook horses whinnied and buildings burned as they see today, this very second, in tens of millions of motor vehicles running around occasionally smacking into one other.
Can we therefore assume a battery that needs to be charged can have 14.0 to 14.4 volts INSTANTLY applied to its terminals and be a happy camper? Remember we are talking about charging and not float maintenance or equalization. Let's not play Three-Card-Monte word-games here. Yes, we can not only assume we can, we can (and will) take this assumption to the bank!
Yeah you got some discharged batteries and you need to charge them. Why not supply them with 14.0 – 14.4 volts? Instantly? “But I have eight golf car batteries!” you complain. Tough! That's enough of a battery bank to have an ability of accepting a few hundreds of amperes charge rate when the bank is hungry. Want to recharge the batteries as fast as safely possible? Give them 14.0 – 14.4 volts, and stand back. Yes, it's like feeding a 6'6” 16-year old. They'll open the refrigerator door, tilt it and let everything slide into their mouth. Like that sliding food, buying enough charging ability to instantly achieve 14.0 – 14.4 volts ain't cheap. The point here, is 14.0 to 14.4 volts recharging is safe regardless of the amperage. One millionth of an amp – one million amps, it's all the same when the voltage is controlled.
Why is this important? It's important when camping. Generators, generally, are like your unemployed brother-in-law, most of the energy they use does nothing more than empty your bank account. For a generator to be the least useful, when you start it, it should have the ability to immediately bring the voltage of the batteries to 14.0 to 14.4 volts and stay there. Stay there until the batteries are charged. Or mostly charged. That's another subject. A two thousand watt generator should have to ability to achieve 120 amperes of recharging rate if switch-type battery chargers are used.
When you crank up a generator it costs a lot of money. Money for fuel (only available after you burn 10-gallons more fuel to go get it). Do you love wasting time driving to and from a gas station? Or paying four dollars a gallon for generator fuel of which more than ninety percent is normally wasted? Like to listen to the 80 db “purr” of your generator for hours on end? How about changing oil, or shelling out a ton of money to replace a worn-out generator? If you don't present 14.0 to 14.4 volts to your battery bank right off the bat, your generator is laughing while your batteries are chirping to be fed faster. Even a “financially comfortable” RV owner should get quivering knees at the thought of wasting that kind of money on running a generator inefficiently.
Any individual who wishes to argue against the points brought out in this article had better start off by running around the world screaming “You Can't Do That!!” at several billion automotive charging systems, before complaining to the author.
Forget so called “rules” printed by battery manufacturers. Their engineers live in a dream world. Their rules are for batteries that can be recharged at “leisure” connected to an electrical grid. You live in the world of four dollar a gallon fuel that is a long way off. It is ummm.... (is the word “not wise” politically correct enough?) not wise to spend four-hundred dollars plus trying to extract twenty dollars worth of “extra-life” out of a pair of RV batteries by following battery manufacturer's “rules” for achieving “optimum life” out of a battery. If you have time and money to burn to try and meet a worthless goal then go for it.
But if you're smart. When you recharge, you present 14.0 to 14.4 volts to a discharged battery INSTANTLY. The issue is you may have one hell of a large battery bank and need lots of amperage to meet this specification. Multiple chargers needed. Is the generator “Big Enough”?. “Which is worth more to me: Not running the generator or putting in more recharging ability? Do I wilderness camp enough to make this worthwhile?” Those are “smart” questions to ask and arrive at an honest answer.
But needlessly running a generator for hours on end, is dumb, dumb, dumb.
And it's all up to you, now that you know facts...