Community Forums

RGulley · 01-21-2019, 07:13 PM

Good evening!
I have added a battery bank in my DRV. The original setup was a single battery setup, with a residential fridge. Found out the fridge runs down the battery fast, which in turn makes it hard to start generator when battery is dead. lol

I added 3-8D AGM battery in the coach and kept the single battery for generator only. I now have 750AH total with 375AH usable at a 20AH rating. Will add solar down the road. Currently have Xantrex HFS 1000 inverter with 55 Amps total charging power.

My Questions:
largest amp charge a single battery will take is 72 Amps. I have 3 batteries. Does this mean I can send 219 total charging amps to the battery bank? Looking to charge batteries as fast and efficient as I can from the generator.

Can I add another charger to same battery bank instead of replacing the existing Xantrex? Might do it anyway to make everything compatible with auto gen start.

bigchick · 01-21-2019, 08:21 PM

so you have a separate dedicated battery for the generator? how are you charging it?

Bob_C · 01-21-2019, 09:24 PM

Some have added a cable from the chassis batteries....

twinboat · 01-22-2019, 05:04 AM

Quote:

Originally Posted by bob caldwell

Some have added a cable from the chassis batteries....

The OP had a 5th wheel.

**Spdracr39** · 01-22-2019, 05:15 AM

Heavy fast charging can boil the batteries and damage them. They will also not get a "deep" charge and will not last as long as if you use a 3 or 4 stage 55 amp charger over a longer period of time. More is not always better. You could use three 55 amp three stage chargers but you would have to isolate each battery from the others while they were charging. "Smart chargers" may detect the incoming amps from the other chargers and may not work well together if not isolated.

twinboat · 01-22-2019, 05:15 AM

Sure you can add chargers to the system as long as you have the power to run them.

All smart chargers charge based on voltage. That means as the voltage climbs, they will cut back on the amp output.

Make sure you use chargers that output AGM voltages.

As far as the standalone generator battery, many generators don't have charging systems and depend on the RV charging system to keep the batteries up.

If yours is like that, your generator battery may run down. A simple fix is to add a small ( 10 amp ) charger, running off the generator or a voltage sensing battery combiner ( Cyrix 100 ) between the big battery bank and the dedicated generator battery.

**Spdracr39** · 01-22-2019, 05:22 AM

Quote:

Originally Posted by bigchick

so you have a separate dedicated battery for the generator? how are you charging it?

An electric start generator may have its own charging circuit and charges its start battery while it is running.

Edit I'll change this to May charge its own battery. I have never seen one that doesn't in the non rv world but I will concede to Twinboats vast knowledge on this one.

Finance · 01-22-2019, 06:02 AM

Check with your battery manufacturer for specific charging recommendations and follow them if you don't want an expensive lesson on how AGM differ from conventional wet cells. LifeLine, for example recommends no LESS than 20% of capacity or 150 amps in your case.

Getting them to 100% SOC requires monitoring voltage and charge current. obviously you can't use a hydrometer and a current tracking device with a shunt is inadequate because recharging current is more than discharge current. It's easy to undercharge them by a fraction each cycle and gradually walk down the SOC without realizing the batteries are losing capacity.

You can use multiple chargers in parallel.

bigchick · 01-22-2019, 06:25 AM

if the generator had its own battery and battery charging circuit why would you need to dedicate the original house battery to the generator?

we have an onan 5500 generator in our 5th wheel. i know that it requires an external battery to both start it and to run it. once it starts the generator this battery must be connected to a converter / charger or else it will eventually run down as it supplies power to the generator to keep it running. the generator does not generate its own 12 vdc power. it needs external 12 vdc power to run. if it is isolated from the new house batteries and their charger the generator battery is going to need its own charger. it could probably be a smaller standalone unit, but it is going to need something.

i'm not familiar with these but i know there are battery to battery chargers available. perhaps one of these connected between the new house batteries and the generator battery would work.