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]

PanhandlePlainsman wrote:
I'm still reading all of your posts. All are appreciated. Too cold here this week to do any work on it. Many thanks!

I will need to price some of these upgrades out to see what works best for me. I do plan to get some brand of 2000-2500 watt generator. I would plan to run it 2-3 hours per day as needed when boondocking occasionally. Looking for best battery and converter choices for the money.

Hi PanhandlePlainsman,

For Battery charging a 1000 watt generator will be fine (with lead acid). 2000 watts is an 'inconvenient' size. I.E. on the edge of not being able to run a microwave when the batteries are being charged.

The best fit, in my opinion, is a 3000 watt or larger genny. I would buy the Champion 3400 with remote electric start in a flash. They are priced to sell, and if my Yamaha dies that is what I will purchase.

[PanhandlePlains]

I'm still reading all of your posts. All are appreciated. Too cold here this week to do any work on it. Many thanks!

I will need to price some of these upgrades out to see what works best for me. I do plan to get some brand of 2000-2500 watt generator. I would plan to run it 2-3 hours per day as needed when boondocking occasionally. Looking for best battery and converter choices for the money.

[wopachop]

My WFCO went into boost mode this morning for 30 mins. I noticed my voltage display said 14.7v. Ran outside to measure charge amps. What weird is that 1amp was leaving the battery. So i must have gone outside right when the charge had stopped.

I also had my solar hooked up. At the time it was giving 2amps to the batteries. I think that is what must have kept the batteries above 14v when i ran outside and measure charge amps from the converter.

Was worried for a second!! Had just got done reading about the converter getting stuck at 14.4v.

[Matt_Colie]

Panhandle and Wopachop,

Please do not mislabel yourselves. There is no fault in being uneducated to some very specific subjects. I lucked out here. I sailed a number of long quiet watches with a man that survived WWII in submarines. In that situation, batteries were their life. I learned a lot from him and probably missed 15~20% of what he tried to pass along.

One thing that I did have to learn on my own to cure my own issues with charging the house bank was the wire size is really important and none of the tables work. Those tables are all for a 3% voltage drop. At 14V, that is about 0.4V. With the entire life of a lead/acid battery being between 11.9 and 12.6 volts, you can't take a hit like that. The difference in recovery time for a pair of GC2s being charged at only 14.0V verses 14.4 is real close to forever.

Matt

[time2roll]

I believe the trick is to get the converter voltage to sag to 13.0 or lower during initial charging. This is actually very difficult even with #2 wire connecting the battery. BTDT. The battery voltage actually pops up fairly quick at 60 to 70 amps plus the voltage drop in the wire and the WFCO is doomed.

If I fire up the inverter/MW pulling 160+ amps while the WFCO is charging it will shift right into boost mode.

Yes I believe the WFCO is supposed to give about 15 minutes of boost mode about every 24 hours and is probably what you were seeing. And that brings me to another story of getting stuck overnight at 14.4 volts boiling my batteries away. Did this more than once. I had to give up at that point.

[pianotuna]

wopachop,

Don't feel dumb. We all learn here. And you are doing a service to the OP, too!

So thanks for checking it out for all of us.

[wopachop]

You guys were right. I cant believe it. I took about 50ah from my 210ah pack. Plug in the trailer and run out to measure amps. I think it was at 28amps and dropping. It kept lowering charge amps and never got above 13.5v.

I'm positive my voltage display shows 14.4 at times. This is with the batteries completely removed from the trailer. Always thought it was some type of timed equalizing charge.

I feel dumb. Cant believe I never noticed. I always heard negative comments on the WFCO. I thought the problem was the WFCO had too high of a float charge and would boil batteries when left on shore power for extended periods.

Hope this info helps the OP as much as it has me.

[pianotuna]

Time2roll,

Yes it is float voltage. Gassing voltage is higher. At 25C (77 f) float is 13.5 and gassing is 14.34 volts.

[time2roll]

I don't need a new chart. And unless the OP has a variable voltage charger I doubt he does either.
It is a good illustration to understand the changes.

[CA_Traveler]

OK about the chart. It's intended to show the variation across the temperature range for common temperature compensation. As such it shows 13.56V float at 77F and 13.0V at 110V. Float voltage is for a charged battery and not the charging voltage for discharged battery.

I'll look into clarifying the chart - Perhaps just show the float variation.

[time2roll]

CA Traveler wrote:
Here you go!

Looks a bit low to me. Must be a float voltage.

[PanhandlePlains]

pianotuna wrote:

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.

So are you saying at 75 degrees F that 13.6 volts is what I should be charging at to not harm the plates? (if following the red line on the chart)

[time2roll]

PanhandlePlainsman wrote:
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.

All I have. Works fine.

See my solar link in signature.

[pianotuna]

PanhandlePlainsman wrote:
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.

Check it against a good volt meter. It may be just fine.