We had an older pop-up, but never had a battery on it. We recently upgraded to a 31' Bullet Premiere 31bhpr. SOOOOO HAPPY RIGHT NOW! haha.. ok, onto my questions about charging/maintaining:The new TT needed a new battery, so I ended up purchasing two deep-cycle RV/marine batteries to install in parallel. I haven't hooked up the batteries yet, but will shortly.1. I have a 12v battery charger/maintainer at home. Is it possible to hook the two batteries up in parallel in my garage and charge/maintain the batteries like that? Or should I just go buy a second charger/maintainer?2. For while camping, I bought 2x40W Coleman solar panels (80W total). I need to find a iMob 4-in-1 connector so I can add both 40W panels together before the 7A charge controller - does anyone know where I should look? I've found them for $7 online, but they want $25 shipping to Canada.3. Since the batteries will be in parallel while connected to the trailer, is it ok for the solar panels / charge controller to be connected to the parallel batteries, or should I disconnect one at a time and charge them? Alternatively, I could disconnect them from parallel and use a panel and charge controller (since I have two of each) on each battery. Just wasn't sure what the proper charging technique is.Thanks!

There's no problem with charging batteries in parallel, especially identical batteries. Obviously it takes about twice as long as charging one battery, since you have twice the battery capacity, assuming the same state of charge.If you have power where you store the trailer, you can simply plug it in and let the converter keep the batteries charged, which would be easier than toting them to the garage and hooking them up to the maintainer (and eliminate any possibility of hooking something up incorrectly sometime). You could also just hook up the maintainer in the trailer if you didn't care to have the converter and other parts of the trailer electric system live all the time for some reason.

There is no power available where I keep the trailer parked, unfortunately, so my only option at the moment is removing the batteries and keeping them at home.So while connected in parallel in my garage, I'd have the batteries connected positive to positive, and negative to negative, and then connect my charger/maintainer to the negative on one battery and positive on the other battery?When connected in parallel on my trailer, just connect the charge controller in the same way? It doesn't mess with any electronics or the converter in the trailer? (sorry, probably dumb question, but I'm new at this).I don't believe the trailer has a battery disconnect switch either - do you recommend installing one for while the trailer is parked for a couple weeks at a time between camping trips?

I would return the Canadian Tire panels if you can, much better deals can be had from Amazon.ca.if you keep them I believe you just need an SAE combiner but check polarity. Available on Amazon.https://www.amazon.ca/NOCO-ISCC2-5-Way-Adapter-Connector/dp/B003L643KS/ref=sr_1_2?ie=UTF8&qid=1490794558&sr=8-2&keywords=sae+splitterWhy don't you set the solar panels up in storage to maintain the batteries?

I have found with my parallel wired 12V battery bank the multiple batteries in parallel will charge in the same amount of time as a single battery if all batteries are wired properly using the same lengths of cabling paths but you have to have a smart mode converter/charger unit that can produce 17-20AMPS of DC current per battery. In the case of two batteries the size of the converter/charger unit should be a minimum of 45AMP DC output. Most of the single battery trailers usually have a 55 DC Output rated converter/charger.Please post the brand and model of the converter/charger unit and the folks on here can tell you if that needs replaced if you want to re-charge the batteries from a 50% charge state to a 90% charge in around a three hour time frame. To get them to a 100% charge rate it will normally take around 12 hours of charge rate if the converter/charger is rated at 45AMPS or 55Amps. The camping off-grid idea is to start out with a 100% charge state battery bank and when the batteries drop to around the 50% charge state you will want to charge them back up to at least the 90% charge state which will take around three hours time. Then you can get almost full performance out of the batteries the next day/night run off the the two batteries again. You can do a good 12-14 of these 50% to 90% charge state before you must do a full 100% charge state. This of course will take a good 12hours of charging to get to a good 100% charge state. This is all battery science when using the stated standard DC VOLTAGEs that are picked by the battery folks designed to not boil out your battery fluids over the best timing they can do getting to the full 100% charge state. If your converter/charger is only one of those smaller 30A DC OUTPUT units then it will take much longer to recharge the batteries.Another issue might be to increase the wiring size from the converter/charger if it is small to a larger AWG size. I would suggest to use a 4AWG size wiring cable going from the converter/charger unit to the battery terminals. This is also a great time to change out your internal lights from the incandescent type to LED type. This is a hugh savings in power consumption and getting the same amount of light. A typical incandescent automotive type light bulb will draw around 1AMP of DC current. The LED replacement unit for this light will only draw around .2 AMPS DC current. When you have some 12-14 of these lamp bulbs in the ceiling of your trailer this adds up big time...Just food for thought - Confirm all of this with battery experts on here... I am just a self trained battery user with no formal battery training expertise and all of this is based on my personal experience using my 12V battery bank in my off-road camping conditions...I have been using my three standard issue 85AH 12V Interstate batteries wired in parallel since 2009 and two of these batteries has finally got to the point of hold their good performance just last season.Roy's imageThese three batteries are wired in this fashion. Was originally four GP24 85AH batteries but I lost one due to over charging in the first month and the battery fluids boiled out.Roy's imageMy new battery bank in the planning stage now will look something like this drawing..Roy's imageThe new batteries will be mounted across the same trailer tongue position but will be using one of those Torklift battery boxes with slide off metal top.Roy Ken

I paid $180 CDN + tax (on sale) for the two 40W panels. I hadn't done much research before now. I liked the idea of having the two 40W panels as they're about 14" wide and when traveling I can put them face to face (maybe with a soft cloth between) and strap them together - easy to transport around. I want to keep them portable instead of mounting, or else I would have looked into larger options for roof mounting.I hadn't thought of the solar panel idea of maintaining the batteries while in storage. With them sitting in my garage I would have to figure out a way to mount the panels outside. I don't mind keeping the trickle charger connected inside the garage though.Thanks for the link. I may also look for a similar connector to leave permanently connected to the battery and leave one end of the SAE connector (capped) dangling outside the battery box so I don't have to unstrap the boxes every time I want to charge the batteries with the solar charge controller.

Can I charge/maintain 12V batteries in parallel?

13 Replies

hedge
Explorer
Mar 29, 2017
I would return the Canadian Tire panels if you can, much better deals can be had from Amazon.ca.

if you keep them I believe you just need an SAE combiner but check polarity. Available on Amazon.

https://www.amazon.ca/NOCO-ISCC2-5-Way-Adapter-Connector/dp/B003L643KS/ref=sr_1_2?ie=UTF8&qid=1490794558&sr=8-2&keywords=sae+splitter

Why don't you set the solar panels up in storage to maintain the batteries?
ShoelaceExpress
Explorer
Mar 29, 2017
There is no power available where I keep the trailer parked, unfortunately, so my only option at the moment is removing the batteries and keeping them at home.

So while connected in parallel in my garage, I'd have the batteries connected positive to positive, and negative to negative, and then connect my charger/maintainer to the negative on one battery and positive on the other battery?

When connected in parallel on my trailer, just connect the charge controller in the same way? It doesn't mess with any electronics or the converter in the trailer? (sorry, probably dumb question, but I'm new at this).

I don't believe the trailer has a battery disconnect switch either - do you recommend installing one for while the trailer is parked for a couple weeks at a time between camping trips?
DrewE
Explorer II
Mar 29, 2017
There's no problem with charging batteries in parallel, especially identical batteries. Obviously it takes about twice as long as charging one battery, since you have twice the battery capacity, assuming the same state of charge.

If you have power where you store the trailer, you can simply plug it in and let the converter keep the batteries charged, which would be easier than toting them to the garage and hooking them up to the maintainer (and eliminate any possibility of hooking something up incorrectly sometime). You could also just hook up the maintainer in the trailer if you didn't care to have the converter and other parts of the trailer electric system live all the time for some reason.

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Can I charge/maintain 12V batteries in parallel?

13 Replies

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