- This topic has 10 replies, 6 voices, and was last updated 2 years ago by Anonymous.
- November 22, 2020 at 18:18 #46430
TallGuy, aka Gary Frens here. Just joined and am hoping to learn a lot of stuff! My wife and I just sold our motorhome and tow’d and have gotten the truck (2020 GMC 3500 dually diesel) part of our truck camper purchased. The camper part is ordered (Northstar Igloo 9.5). I have some leeway in the electrical system I’d like some input on. Two 6 volt batteries or two 12 volt batteries? The motorhome had two 6’s and my cpap and a fan would drop the 225 amp hour batteries to about 84% that’sabout all we used them for overnight. Solar power, portable, fixed, or a combination? Not real fired up to have any more holes in the food than necessary. And last what size inverter and should it be hardwired or one of those cigarette lighter type plugs?
Thanks a bunch for your help! I hope to make several friends here!
- November 22, 2020 at 18:58 #46432GeorgeParticipant
If you can stick with 6 volts I would do that. It seems you get a few more AH for a similar sized battery. We had twin 6 volts with a total of 220 AH in our former travel trailer. But we couldn’t fit the same batteries in our new Arctic Fox TC so we went with two 12 volts and still have 200 AH. I can’t remember how each pair were wired but I think the 6 volts were wired in parallel and the 12 volts are in series – or maybe it’s the other way around! Anyway – lots of info available on the web.
- November 22, 2020 at 19:25 #46433AnonymousInactive
Welcome to camper paradise Gary 🙂 !!
Questions to you Sir:
When you say 84%, does this mean 84% of 225a/hrs (e.g. 189a/hrs consumed), or something different?
Does your CPAC run off 12vdc or from a 120v inverter?
Would Lithium be an option for you?
Just trying to think outside the box here – lol …BTW, for clarity only 6v’s are wired in series, while 12v’s are wired in parallel…
- November 22, 2020 at 19:48 #46434
Thanks for the welcome!
With my CPAP and a fan we used about 16% of available power leaving 84% to build on throughout the day with our solar panels. My CPAP runs off a 120v inverter. I can’t keep the terminology straight either: series vs parallel. The motorhome had two 6v batteries wired for one gigantic 12 v battery.
- November 22, 2020 at 21:19 #46435AnonymousInactive
Typically with Wet cell batteries, the best practice is to set a DOD (depth of discharge) floor of about 50% which would roughly equate to around 100 or so (< >) ‘usable’ amp/hrs…It’s in this regard that I’m not too sure what you mean by 16% + 84% = 100%; e.g. 100% of what usable amp/hr amount??
Also, by what method are you measuring this SOC (state of charge) percentage (type of metering?)…
Thx, Just curious…
- November 23, 2020 at 07:19 #46443
The 16% used was measured by the Bogart Engineering battery monitor that was installed in the motorhome. The 16% used left 34% before I hit the depth of discharge floor of 50%.
- November 23, 2020 at 07:59 #46452Joel GambinoParticipant
As a data point, here’s what I did for my solar power install:
Since that write up, I added another 165 Watt panel to handle the additional load of the compressor refrigerator.
I also plan to add a portable foldable panel made from 2 50W panels hinged along the edge. I’ll provide a write up on that when I finish.
I’m happy to answer any questions you might have. Good luck!
- November 23, 2020 at 09:09 #46454Harvey ShawParticipant
First I’ll point out we are super low energy users. No micro, tv, have led lights usually only a couple of this are ever on. We have one 160W roof mounted solar panel. We are boondockers and even in a Nat Park site we don’t use a hookup.
At home our camper is under a CalMark cover which is fantastic by the way. Apparently we keep a charge even under the cover (we’re in norther AZ).
We’ve never had a power problem with this setup (2 Lifeline GPL-4CT batteries). I had an extra “portable” zamp panel, but never used it and sold it. Hope this is some help in some way.
- November 23, 2020 at 10:03 #46455Joel GambinoParticipant
My power needs are perhaps a little higher than others due to the compressor fridge. I also like to operate the ham radio which draws some power.
The only reason I want the portable panel is for when I park in the shade.
- November 23, 2020 at 13:17 #46479AnonymousInactive
Welcome to TCs! We also full-time RVed (for about 12 years) but finally sold it and made the move to a truck and camper. Now we no longer drive past those little roads with the remark, “I wonder where that goes?”. Now it’s, “Let’s find out!” You’ll love it!
Don’t know if this will help, but here goes. Our set-up is pretty minimal. We have a Lance 650 on a Ram 3500 (SRW/short bed/crew cab). Has only the single stock battery. We have a 160-watt Zamp portable panel and nothing on the roof. Logic for the portable was we can — using a 20-ft. extension — move it as needed to catch sun when parked in shady areas. It has worked out pretty well so far. We’ve never had a power crunch yet.
For CPAP I just got a Goal Zero Yeti-150 battery pack (150Wh, 14Ah (12V) but have yet to test it. Guess I’ll move that up on the ‘to-do’ list.
Enjoy your new rig!
- November 23, 2020 at 13:33 #46480AnonymousInactive
Well, back to your original question regarding 6v vs 12v batteries…If wet cells have been working well for you I’d suggest going with two 6v batteries (connected in series) mostly because they are more tolerant at frequent and somewhat deeper discharges without adverse effects, though they are about 3/4” taller (at the post) than a comparable 12v battery…Thus, it may pay to consider adding an automatic battery watering set-up…Having said that, with a CPAC machine, voltage drop-off (during the course of any normal discharge cycle) could be of concern because some inverters will alarm and/or even shutdown at about 12.x volts… To illustrate, here’s a handy googled link to a SOC/voltage chart:
FWIW, holes in the roof for solar panels IF caulked properly and inspected annually should be of little if any concern whatsoever – JMO…I have 6 panels (440w) totaling 24 screw brackets with no issues over an 11 year period…
Sounds like your inverter use is primarily for the CPAC, but I’d go with a pure-sine model simply because they are more efficient (less waste heat produced – a pf thingy) and because (as with solar per watt) prices have dropped dramatically…
The only leak ever experienced was a slight leak around a bathroom skylight surround caused by a leak beneath Eternabond – go figure, eh!! … Caulking around the eternabond edges eliminated the leak – finding the actual leak source was the hardest part because (dummy me Ugg !!) I had mentally dismissed the eternabond tape as a possible cause – WRONG lol!!
BTW, if you get another SOC meter, (first-hand ‘re-work’ $$ experience speaking here!!…) consider one that is also Lithium (i.e. LiFePo4) compatible, this in the event of a present or future Lithium upgrade…Victron’s excellent BMV 712 (with smart phone bluetooth) immediately comes to mind – just saying…
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