House Batteries, external and internal, Question

[macstever77]

I have an Airstream Interstate "B" motorhome (built on a Sprinter). We plan to do quite a bit of dry camping and want to up our house battery from 100 amp hours to 300 amp hours by replacing the original house battery that is suspended under the left rear of the chassis in a metal box. There is not room for two batteries at this location.

I plan to put 2 AGM Lifeline 6 volt batteries, 300 amp hours each, in series: a. One in the lengthened original battery box; and, b. One directly above the old battery box, but inside the interior of the van just in front of the left rear door. AGM batteries tend to recombine hydrogen with oxygen inside the battery itself to form water and thus pose so little fire hazard that they are permitted inside airplanes.

My question relates to having one battery inside and one battery outside the vehicle. If there is a temperature differential between the two batteries, will it have a harmful effect when the batteries are being charged or when they are being discharged? I plan to replace the current stock charger-converter with a three stage charger-converter?

Thanks,

Steve

[g1g]

That really is a good question. I really do not know anything about an AGM battery, I didn't even know 6V were available I do know cold temprature can suck power away from regular batteries. Possibly the temp difference may look like a dead cells compared to the other ones and pulling the power down out of the warm ones. This would also cause a different rate for charging although possibly the charging may raise the temp in the battery but it would still be different.
I do think the only time it may make a difference is during large temprature differences.
I think I will be looking forward to see any answer on this.

[markopolo]

Great question. I don't know the answer either. Here's a quote from phred:

TEMPERATURE
Temperature is important when charging any kind of batteries. A really hot battery (EZ to achieve if they're sitting out in a cheap, plastic box) will overcharge well before the voltages listed earlier. Keeping batteries "indoors" helps keep them at about an ideal temperature (of about 68 to 77ºF). Actually, high temperature only becomes a real problem when the battery is being "floated." A 13.8 volt float can easily become a 14+ a-whole-bunch float at 90º. Temp can also be a winter problem as batteries try to freeze and their amp hour capacity is reduced by over 30%.

With "cheap" batteries I probably wouldn't do anything and just replace them more frequently. With Lifelines, it's worth figuring out the best way to do it.

Two 12v batteries would be easier manage separately, either with an A,B,Both switch, a high tech charger (two batt. banks, temp compensated) or a combination of both.

I wouldn't do anything special to compensate in my RV because of where and when I camp. (mostly Pacific Northwest in late Spring, Summer & early Fall). It's not really hot or cold.

[macstever77]

Thanks for your input. I, too, live in the Northwest, so the comments about very hot or cold temperatures seem pertinent.

This evening I addressed my question to the Lifeline Battery website. I will post their response if I receive one.

Thanks again,

Steve

[macstever77]

This is the response to the earlier question that I also posed to Lifeline Batteries:

"What your doing sounds fine. The temperature difference should not matter at all. Keep in mind, when putting a battery inside that all battery chargers have the potential of over charging. In the event that this happens our AGM batteries will vent as a safety feature. Just something to keep in mind.

Justin Godber
Lifeline Batteries"


Thanks to Lifeline Batteries for their quick response and to Class B Forum and those that replied.

Steve