Charging house batteries

DryCamper11 wrote:

westend wrote:
Trojan recommends a 10-13%C charge rate for absorption cycle.

FYI:
I spoke to Trojan's tech support and we discussed this recommendation. I was interested in maximizing charge rate to minimize gen run time and was considering AGM at the time. He said that 20%C charge rate for FLA deep cycle batteries would have no significant effect on life when used in an RV application. If I could live with that rate, he suggested that I not go AGM. I went with 17%C.

Yes, that's consistent with what I know about charging 6V's and fits the application. I would assume that the 10%-13% that's listed in the owners manual is part CYA and part good advice.

I'm trying to remember what they used in the cart barn at the Golf Course where I worked. It was actually one large transformer and multiple terminals for each cart. The cart barn wasn't my purveyance so I tried to stay out of there. Trojans were used, exclusively. My own cart had some old funky 36v charger that hummed along at about 39v.

RJsfishin wrote:

smkettner wrote:
Post the converter model for best replacement options.
Even if the OEM converter works... you still want a new replacement with those batteries.

Why ?

With close to 500 amp/hrs I assume the OP would like to charge in a reasonable amount of time.
And you are correct that OP may already have 80+ amps multistage converter. I have doubts.

BFL13IMO wrote:
there is a mix up there in the charging rate numbers. 10% on a 100AH battery would be 10 amps, so that would be 46 amps on a 460 AH bank. Using 100a on the 460 would be a 22% rate

However, that 10% is for max battery life, being "gentle" and not for RVing where you want a shorter generator run to do the recharge. So now you have a trade off.

Yes. As I said, even Trojan's tech support felt that up to 20% would be OK. The 10-13% number was chosen as it was gentle and would allow a full recharge in the overnight charge time that most users had available. They hadn't done much work in determining the fastest charge rate possible, as faster chargers were more expensive and most customers wanted the longest life with the least expensive chargers to recharge the maximum number of batteries in the typical overnight charge time they had available.

Beyond 20% he thought you'd probably begin cutting into battery life somewhat, but not drastically. He didn't seem to have any test data for any of this, but perhaps there isn't any.

westend wrote:
Trojan Battery user's guide (I had to find it to see what Trojan recommends). Trojan recommends a 10-13%C charge rate for absorption cycle. For one battery, this would be around 25 amps at 7.2 V (or so).
You have four, depending on how much time you wish to run the generator, a charger of 80-100 amp output rating would seem appropriate. There is much more to the charge cycle than just the simple math above so a call to bestconverters.com would be worthwhile.

IMO there is a mix up there in the charging rate numbers. 10% on a 100AH battery would be 10 amps, so that would be 46 amps on a 460 AH bank. Using 100a on the 460 would be a 22% rate

However, that 10% is for max battery life, being "gentle" and not for RVing where you want a shorter generator run to do the recharge. So now you have a trade off.

There is not much penalty in using a higher charge rate anyway, since you won't get near the batteries' deep cycle limit in the years of ownership unless you are like Mr Wiz doing a deep cycle every day all year.

You can kick off with 30% charging rate and it all works fine. Higher than that, you get to where voltage spikes so soon that there is no constant amps stage, it tapers right away. this still works but you don't save much gen time by going from 30 to 40 like you do going from 20 to 30, as it is not linear.

westend wrote:
Trojan recommends a 10-13%C charge rate for absorption cycle.

FYI:
I spoke to Trojan's tech support and we discussed this recommendation. I was interested in maximizing charge rate to minimize gen run time and was considering AGM at the time. He said that 20%C charge rate for FLA deep cycle batteries would have no significant effect on life when used in an RV application. If I could live with that rate, he suggested that I not go AGM. I went with 17%C.

RJsfishin wrote:

smkettner wrote:
Post the converter model for best replacement options.
Even if the OEM converter works... you still want a new replacement with those batteries.

Why ?

Two reasons:

1. Smart chargers/smart converters are a lot better at charging (faster) AND don't overcharge once batteries fully charged. Said another way, they charge at higher voltage during bulk and absorption and lower voltage during float stage.

2. If speed of charging is an issue (dry camping and running generator to charge batteries) in addition to #1, a higher amp converter may save a lot of fuel.

Note: Some "stupid" converters have an optional controller that turns them into smart converters-- just a plug and play. So the upgrade may be very cost effective.

Except for running out of time, no such thing as charging batteries too slowly.
I thinking,... what if wanting to charge w/ a quieter 1000 or even a 2000 watt gen.
What if he threw in a couple hundred watts of solar in w/ a quiet generator.
If I went to 4 batteries, I wouldn't part w/ my 45 amp converter/1000 watt gen.

Now just adding a 100 amp charger, I'll buy that.

Trojan Battery user's guide (I had to find it to see what Trojan recommends). Trojan recommends a 10-13%C charge rate for absorption cycle. For one battery, this would be around 25 amps at 7.2 V (or so).
You have four, depending on how much time you wish to run the generator, a charger of 80-100 amp output rating would seem appropriate. There is much more to the charge cycle than just the simple math above so a call to bestconverters.com would be worthwhile.

smkettner wrote:
Post the converter model for best replacement options.
Even if the OEM converter works... you still want a new replacement with those batteries.

Why ?

Thanks again
I will get the make of the inverter tomorrow. I do not think I disconnected the convertor but will also check that. The invertor that I have in my fiver has a built in charger so should have gotten one of that type for the little motorhome.
I will check things out and get back to you.
Thanks again for all the help.
Pam