Battery Charging

[flyfishing48]

My 5th wheel has a pair of 6 volt batteries and a 3 stage inverter/charger.
If I am boondocking and hook up a generator for and hour or so in the morning, would I be better off pluging in a battery charger to recharge the batteries or just let the 3 stage charger do its thing?

[MEXICOWANDERER]

That was for a sense of perspective. Is' s sometimes are a long way from ought-to-be's. I'm spoiled, I manufacture my own ought-to-be's

[jrnymn7]

"Kind of like asking which is the faster car, a red one or a green one."

Without a doubt, the red one!

[NinerBikes]

MEXICOWANDERER wrote:
I'll reiterate this.

The fastest SAFE way to recharge flooded lead acid batteries is to apply amperage however much it takes, to instantly raise battery terminal voltage to 14.8 VDC @ 20C. Fourteen point eight volts is continued until such time as specific gravity raises to 95% of original fully charged density (acid has pronounced lag/overrun characteristics).

Four GC220 batteries (440 ampere hours) can easily accept a 120 ampere charge rate as maximum battery acceptance. This is provided to give you perspective as to what is allowable and to be expected. Forty amp charge rate merely tickles 24 cells and makes them giggle. Great for power post maintenance, crying towel sad for generator charging.

No way a Progressive Dynamics charge controller can or does provide that. 14.4V is all she wrote.

[MEXICOWANDERER]

I'll reiterate this.

The fastest SAFE way to recharge flooded lead acid batteries is to apply amperage however much it takes, to instantly raise battery terminal voltage to 14.8 VDC @ 20C. Fourteen point eight volts is continued until such time as specific gravity raises to 95% of original fully charged density (acid has pronounced lag/overrun characteristics).

Four GC220 batteries (440 ampere hours) can easily accept a 120 ampere charge rate as maximum battery acceptance. This is provided to give you perspective as to what is allowable and to be expected. Forty amp charge rate merely tickles 24 cells and makes them giggle. Great for power post maintenance, crying towel sad for generator charging.

[time2roll]

I do hope the GC2 were tip top 100% charged and disconnected for storage.

[NinerBikes]

flyfishing48 wrote:
My 5th wheel has a pair of 6 volt batteries and a 3 stage inverter/charger.
If I am boondocking and hook up a generator for and hour or so in the morning, would I be better off pluging in a battery charger to recharge the batteries or just let the 3 stage charger do its thing?

Without more information, there is no correct answer. Get back to us when you start camping again and can actually measure what is going on. A trailer in storage for winter with no access, means you don't have access to the information required to answer.

[BFL13]

You can get an idea of the time to recharge your pair of 6s from this ugly graph. This also lets you decide what is "worth it" for getting more amps of charging in terms of cost of the charger, enough generator to run the charger, and the time it takes.

The key thing is the diminishing returns in time saved as you go higher in charging amps. EG useful in deciding if you would be better off with an 80 amper instead of a 60 amper on a pair of 6s compared with on four sixes.

Note- at the same amps, double the battery doubles the time, but on the same battery size, doubling the amps does not halve the time.

[flyfishing48]

I won't be able to do any testing for awhile. Camper is in our storeage building with no power. Once I get my new adapters and can hook up a generator I can do some testing to see what is up.

Maybe next week. In Feburary I'll move the camper over and plug it into the outside receptacle at the house and can do some more checks. Won't be on 50 amps until we hit the road mid Feburary.

With the replies so far I have a good idea what to look for.
My whole concern is to get the most charge out of the generator hours when dry camping.

[BFL13]

Iota drops to 14.2 right after battery gets to 14.6 and PowerMax drops to 13.6 then, so it could be there after three hours.

[NinerBikes]

Unplug from the pedestal for the night... in the morning, put a Digital multi meter on your jars and measure the combined voltage without charging. Plug in to your generator, with the Charge controller turned on, and again measure the voltage at the batteries with the charger on, both at start up of charging, and after 3 hours, measure the voltage at the batteries again, with generator still running.

Report back to us what you find for all three steps to measure at, for voltage at the battery terminals in 12Volts.

We are interested in 3 things.

Battery state of charge first thing in the morning, determined by resting voltage with as much electrical load turned off as possible first thing in the morning.


Voltage received at the battery when you first start charging, are you in bulk charging mode or not, with your existing charge controller. Depends on the brand... WFCO's as noted, fail to engage in bulk charging mode, at 14.4 to 14.8 Volts.

Voltage received at the battery after 3 hours, after the batteries should be out of bulk charging mode, and in absorption or bulk charge mode still. Certainly not in float charging mode yet at 13.4 to 13.6V charge rate.

[time2roll]

WFCO is notorious for not switching to boost mode when expected. You need to verify but I think you will be using the portable along with the WFCO. If spending money replace the WFCO.

+1 for solar.

[pianotuna]

Hi,

Better yet, add 300 watts of solar and forget about charging with the genny.

[CA_Traveler]

rockylarson wrote:
Ok, I'll bite, why can't you do both?:?

Generally if they are closely matched in terms of charging voltage then both can work together. Otherwise one might determine the battery is charged and not contribute any amps.

A rig might have charging from the alternator, charger with the gen and solar and any 2 or 3 can work together.

[rockylarson]

Ok, I'll bite, why can't you do both?:?