Battery charging question.

[PanhandlePlains]

We are in our 3rd fifth wheel now and have boondocked some. New to us 2016 KZ Durango does not have an onboard generator. Plan to get a 2000-2500 watt portable generator. KZ has only one battery and a WFCO 9865 3 stage converter (I've seen it in 13.6v stage and 13.2 stage haven't had battery down enough to see 14.4 yet). We don't use much electricity. Main draw would be furnace over night set at 65 and may stay out about 5 days. We normally run generator about 1 hour in the morning and 2 hours in the evening (watching a movie). We need a new battery. Of these choices A.) Two 6V GC2, B.) One large 12V deep cycle, C.) ONE AGM - which works best? I'm considering which choice will charge sufficiently in three hours per day to keep us going and not damage batteries from undercharging. Have also considered taking a regular battery charger along to plug into the genny.

[pianotuna]

wopachop wrote:
Ive got 2 GC2 from costco. Will unplug the trailer and run the furnace and things off the battery. How many amp hours should i take out before plugging the trailer in to charge? I only want to drain the batteries enough to determine if my WFCO is charging at 14+v.

I would go with voltage not amp-hours. If voltage is 11.8 under load (furnace, lights, and etc), it is time to charge.

[pianotuna]

PanhandlePlainsman wrote:
I need more explanation on the application of the temperature chart.

Battery charging "charts" are set up for 25C (77f) and most charts list the charging voltage at 13.5. Gassing voltage is 14.34 volts.

The speed of chemical reactions approximately doubles for each 10 degree C (18 f) that the temperature increases.

As the temperature gets higher, the charging voltage should be lower to prevent extra erosion on the positive plates. At 50 C (122 f) charging voltage is just 13.2 and gassing voltage is 13.8

As the temperature gets lower, then charging voltage needs to be higher to "drive" the charging. At -30 c (-22 f) charging voltage ought to be about 16.2. This is a problem for an RV, because the computer boards for the fridge, furnace and other devices may only be rated about 15.4 volts. The battery will still charge at a lower voltage--but it may take a lot more time.

For example, at 12.8 volts, and 25 c (77 f) it may take 168 hours to fully charge a battery.

I hope this "thumbnail" of what may happen helps.

[CA_Traveler]

Harbor has very cheap voltmeters that are adequate. And of course there are better ones available on Amazon, stores, etc.

[CA_Traveler]

wopachop wrote:
Ive got 2 GC2 from costco. Will unplug the trailer and run the furnace and things off the battery. How many amp hours should i take out before plugging the trailer in to charge? I only want to drain the batteries enough to determine if my WFCO is charging at 14+v.

Draw 50% which is about 110Ah depending upon the battery specs. Then turn off all loads and start charging. It should (at least a good 3 stage charger should) start in bulk charging at the max amps raising the voltage to 14.4V. Then hold the voltage in absorb charging tapering the amps down until it enter float charging with both the voltage and amps tapering down to the float mode with about 13.6V and very low amps. Be sure you are measuring at the battery terminals.

I'd keep a log of V, A and time for future reference.

[PanhandlePlains]

The only volt meter I have now is a digital one plugged into a cigarette lighter type plug in the bedroom. That may not be sufficient.

[time2roll]

Wapo,

12.1 to 12.2 volts under load should be close to 50% and easily trigger the need for the converter boost mode.
When you plug in you should see voltage steadily climb above 13.8 volts if WFCO is in the boost mode. With more time you should see 14.xx volts as the battery tops up on charge.
Voltage at the converter will be higher than the battery when charging near the rated amps.

I recommend this test for every RV if you expect a reasonable fast recharge on limited generator time.

[PanhandlePlains]

Sounds like lots of challenges. I'll try to work it out. Thanks again.

I don't need no programable thermostat. When she says to I get up and do it myself. Like a man.

I need more explanation on the application of the temperature chart.

[wopachop]

time2roll wrote:

wopachop wrote:
While the WFCO has a bad reputation i see no reason to replace it. I have the WFCO and it goes into a 14.6v charge mode every few days even with no batteries hooked up. This is while plugged into shore power.

What about when the battery is low and you have a 3 hour generator window and a cold night coming?
PD, IOTA, Boondocker will go to 14.4 every time.

Wow i had no idea the WFCO often fails to charge at 14.4v. Ive tested my stuff and measured amps with a clamp meter. Will have to do it again.

Ive got 2 GC2 from costco. Will unplug the trailer and run the furnace and things off the battery. How many amp hours should i take out before plugging the trailer in to charge? I only want to drain the batteries enough to determine if my WFCO is charging at 14+v.

[pianotuna]

PanhandlePlainsman,

They are inexpensive. The makers wish to save a dime. I've only heard of ONE wfco going into boost mode since 2000.

There is no need to test. Just search the site using google. There are hundreds of reports of "no boost".

Two routes for you.

1. get an inverter/charger with a remote. Mine allows me to charge at 127 amps on a 15 amp circuit. as a bonus it is temperature compensated with a sensor on the battery. I left my PD in place but disconnected.

2. get a better quality converter.

[CA_Traveler]

And yes 2 6's means your generator run time will increase a lot unless you make charging changes.

[CA_Traveler]

PanhandlePlainsman wrote:
It's hard to believe all WFCO's are faulty. I'll try to do some testing.

They are not faulty just a cheap design often with long undersided wiring.

But they serve a purpose - for the salesman to explain that the RV comes complete with a battery charger.

[CA_Traveler]

Update: This chart shows a common variation of float voltage for a charged battery over a range of temperatures. It needs clarification.

Here you go!

[Matt_Colie]

PanhandlePlainsman wrote:
I'll check on 20 amp chargers.

It's hard to believe all WFCO's are faulty. I'll try to do some testing.

thanks again

Pan,

A 20amp stand-alone will take a very long time to recover a pair of GC2s to full density. Most stand-alones do not have the high terminal to get the density up where you need it.

It is not that all WFCO's are faulty, they were just not made with attention to detail that we can count on from a PD or IOTA.

Wire size is often an issue in DC systems because the working voltage window is so small that even small line losses can be a big problem.

Matt

[dieseltruckdriv]

Questions that haven't been asked, how are you at regular maintenance? Are your batteries easy to get to so you can regularly check the water level?

My last fifth wheel had batteries that had to be lifted out to check the water level, so I bought two AGMs that I now have in this 5er. Of course this 5er has slide out trays for the batteries, but now I know I don't have to worry about checking their water level.

We try to boondock most of the time, and with our 420 watts of solar and an inverter, we very very seldom use our Hondas any more. I have to remember to do the monthly check on them most of the time, due to lack of use.

Just one more thing sir, (hehehe) we also put a Honeywell programmable thermostat in our 5er. It is the same one we have at home, and we have it go to 60 at night and then warm up before we get out of bed. That also helps with battery usage.

[wopachop]

If you are away from crowds the little Honda generators would work great. You could even leave the generator running and power an electric heater at night instead of the furnace. Lots of my camping buddies have the honda 2000s and they leave it running the entire camping trip.

You might not even need a new battery yet. Its no big deal to have a weak battery if you know the pull start generator is right there with you. Some of my friends have 5500watt onboard gennys and chose to run the 2000watt instead. Saves on gas money long term. Also less noise. We camp in the desert where its always noisy. Thats why running a generator 24/7 is not frowned upon.