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GlueGuy View Drop Down
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Posts: 2629 		Direct Link To This Post Topic: 1 or 2 new batteries?
    Posted: 31 May 2017 at 10:08am
Our R-179 came with two boxes, and two batteries. Separate tie-down strap for each one.
bp
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Posts: 347 		Direct Link To This Post Posted: 31 May 2017 at 9:38am
Originally posted by Tars Tarkas

I've thought about going with two batteries but I get tripped up trying to find a box to put them in.  Do folks just use two boxes?  Inches really matter on the tongue.  I'd like to find one box for both batteries.  Easier to wire together that way too.  Anyone have any recommendations?

TT


I bought a battery box from http://www.rvlockbox.com/

You can see my post on installing it here:  http://www.rpod-owners.com/forum_posts.asp?TID=9728&KW=&title=rpod-177-battery-box-mod
2021 Winnebago Micro Minnie 1708FB
2017 R-Pod 177 (Blue) HRE SOLD
2004 Outfitter Apex 8 camper
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StephenH View Drop Down
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Posts: 6288 		Direct Link To This Post Posted: 30 May 2017 at 9:59pm
The difference then would be whether the batteries are true deep-cycle batteries that can be drained down below 50% without affecting their lives.

The ones I see on Batteries + Bulbs is a Duracell SLI24MDC Ultra with 75 (20 hour rate) AH. That would be 900 watt-hours. Two in parallel then would yield 1800 watt-hours. There is also a group 31 battery, SLI21MDC Duracell Ultra with 105 (20 hour rate) AH or 1260 watt-hours. Double that for 2520 watt-hours for the pair. The cost of the group 31 battery is significantly higher than the GC2 batteries I bought.

This has been an interesting and informative discussion. I plan to stick with my GC2 batteries until there is a viable alternative.
StephenH
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ouR escaPOD mods
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GlueGuy View Drop Down
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Posts: 2629 		Direct Link To This Post Posted: 30 May 2017 at 8:18pm
Originally posted by StephenH

How do you do the conversion from amp-hours to watt-hours? It looks like you multiply the amp-hours x the voltage. When using 6V batteries wired in series, would one multiply the AH x 6 or x 12?

215 AH (20 hour rate) x 6V = 1290 watt-hours
215 AH (20 hour rate) x 12V = 2580 watt-hours

In other topics, I have read that series adds voltage, but amperage remains the same. Parallel adds amperage but voltage remains the same.
Exactly right. Multiply volts X amp-hours to get watt hours PER BATTERY. Then you can treat each battery as a bucket of watt-hours, and series versus parallel doesn't matter any more. Just add them up.

So two 215 AH 6 volt batteries is 1290 watt-hours. You have two of them, you've got 2580 watt-hours.

A rough equivalent in 12V would be two 110 AH batteries. 12 X 110 = 1320 watt-hours. You strap in two of them, you've got 2640 watt-hours. 

And it works just as you describe, parallel gets you the same volts, but doubles the current. In series, you double the voltage, but keep the same current. 

Potato versus potahto.
bp
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StephenH View Drop Down
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Posts: 6288 		Direct Link To This Post Posted: 30 May 2017 at 6:07pm
How do you do the conversion from amp-hours to watt-hours? It looks like you multiply the amp-hours x the voltage. When using 6V batteries wired in series, would one multiply the AH x 6 or x 12?

215 AH (20 hour rate) x 6V = 1290 watt-hours
215 AH (20 hour rate) x 12V = 2580 watt-hours

In other topics, I have read that series adds voltage, but amperage remains the same. Parallel adds amperage but voltage remains the same.
StephenH
Happy is the man that findeth wisdom,...

ouR escaPOD mods
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GlueGuy View Drop Down
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Posts: 2629 		Direct Link To This Post Posted: 30 May 2017 at 5:53pm
Two batteries the same size & weight should have the same amount of energy (measured in watt-hours) regardless of voltage.

Many of the 12V batteries available don't have a huge amount of energy. Most of the 12V batteries in the desired size range are around 75-85 amp-hours (20 hour measure), which is only 900-1020 watt-hours. Convert any battery you're looking at to watt-hours in order to get an apples-apples comparison.
bp
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Posts: 29 		Direct Link To This Post Posted: 30 May 2017 at 5:25pm
I have 2 12v batteries.   With a full charge, I can run the heat at night with the thermostat set at 60, run the refrigerator on propane, shower each day, use the stove, and use the lights when needed for 4 days/3 nights before needing to charge the batteries.   
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Posts: 2629 		Direct Link To This Post Posted: 30 May 2017 at 2:20pm
Originally posted by TheBum

I've heard that AGM batteries don't get along with the converter in the Pods. It has to do with the charging algorithm the converter uses, which is optimized for lead-acid.
AGM are still lead acid. They just don't have "liquid" (the liquid has been absorbed into a special matt material. You can still charge them with standard charge controllers, although the various set points will be slightly different (bulk, absorb, float, idle).

Good quality batteries usually have very specific set points, regardless of them being wet, dry, or whatever. Even wet batteries from different manufacturers will have slightly different set points. So unless your charge controller is programmable, you will probably never be exactly on the specifications for a particular manufacturer.

There will be specific, and generic set points. A non-programmable charge controller will be set to some generis set points that will be "safe", even though it may not be "exact".
bp
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Posts: 1407 		Direct Link To This Post Posted: 30 May 2017 at 2:02pm
I've heard that AGM batteries don't get along with the converter in the Pods. It has to do with the charging algorithm the converter uses, which is optimized for lead-acid.
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StephenH View Drop Down
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Posts: 6288 		Direct Link To This Post Posted: 30 May 2017 at 10:53am
It depends on how many nights and whether you have shore power or a generator available. While the furnace uses power, dual 6V batteries have the ability to run the furnace multiple days, especially if you don't have the thermostat set to 72 degrees. I usually lower ours to 60 when we go to bed. If you are planning on an extended trip, then you could bring the Buddy heater. If you use it, be sure to have adequate ventilation with the vent and a window. They don't have to be open far. I think for the smallest one, 4 square inches was what the manual specified. For the Portable Buddy, a little more is needed.

If you have a generator, you can run it to charge the batteries during the day. I don't think you will have any problems.
StephenH
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ouR escaPOD mods
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