Misread Trojan Battery Manual

MEXICOWANDERER wrote:
The C10 and C20 BCI rate was established for battery backup systems not generator power. When I lectured about this, battery engineers used to reply "Well that's our general doctrine". I asked them if they camp, drove 40 miles to go get gasoline, and put up with generator problems and wear-out.

"What's That Got To Do With It?"

There are probably ten thousand motorhomes out there that have good charging leads to the house batteries. Start the engine and the alternator tries it's best to put 14.4 volts into the batteries. Some of the newer Fords have 220 ampere alternators. The batteries won't die of seeing a higher than C20 rate. They'll die because of over discharge or sulfation.

Many have a fixation with C10 or C20 charge rates. WHEN YOU HAVE A SURPLUS of kWh charging available MOST OF THE TIME, then the percentage rates become valid. Until that point of recharge potential is reached, C10 and C20 is useless. Unless of course you just love to hear the nature-loving purr of a generator. I do not want to fatten the wallets of crude oil speculators and refiners any more than I have to. I have done number crunching (this means intensive, comprehensive analysis) of how much money batteries cost. Dollars per ultimate kWh delivered, total lifespan. People who run a generator at a C10 or C20 rate are kidding themselves. Fine, that's them - but it's another ballgame when they try to convince others that the C10-C20 theory is Holy Writ.

I subscribe to the FIVE PERCENT charge rate when utility power is available. Who cares? Time is not an issue. 24 hours at 5 amps is enough to fully recharge a pair of group 24 batteries.

Reminds me of someone who spends a hundred dollars on D cells, for reading to save two dollars on the electric bill.

yup, I agree

lower charge rates (C/10, C/20 (5%)) etc. usually will give longer cycle life (number of charge discharge cycles) than high charge rates. So, it somewhat depends on what is more important, high cycle life or short charge time. For Trojan 6V, the cycle life is high enough that most RV'rs, will never have cycle life determining battery life, age, sulfation etc. will hit first. Personally when I'm dry camping and using the generator, I hit the batteries with close to C/2 or C/3 charge rate. yes, I'm probably loosing some cycles, but not enough to worry about. Under solar, the charge rate is closer to C/30. My last set of batteries were 10 years old when they went to in-laws and 3 years later are still working fine with SG still up there. Lost some capacity but still highly useful.

Now if I lived off grid year round with solar for charging, I'd size my system for around C/20 for long cycle life.

Decide what's important, and pick your tradeoff. No free lunch.