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YODA · 03-11-2018, 09:35 PM

OK folks I need some experts to set me straight

In my old fiver that I had for 18 years I had a high powered (high priced) solar panel (35 watts

) installed. It was a state of the art Simmons.

At time of purchase I had two batteries installed by the dealer to go with the solar. With two kid leaving lights on I quickly learned I needed more storage power. (also bought 2- 2000i generators)

We had a local Hastings dealer that had worked with me in the past who set me up with a neat vented storage box and two 6V golf cart deep cycle batteries set up in series by them, along with the proper cables and fittings and disconnect set up. I tied them in parallel with the two 12 volt and all was well.

Fast forward to my new 220RK that also has dual batteries installed by the dealer along with a Go Power 160W solar set up. I mentioned to the service folks that I was thinking of getting another 6V set up as I had before for more storage (boon-docking and possible inverter). I was told it would not work as all the batteries had to be the same.

I was going to isolate the 2-6V with a disconnect too, so I could keep them isolated when possibly using the inverter that I am still thinking about.

As the output of the series 6V batteries is 12 V as far as the system sees I don't see a problem. It worked for me before. Whats the real story?

BTW those 2-6V batteries were still going strong after 14 years and I had to replace the 12V deep cycle twice.

Thanks for your thoughts - Keith

jelag · 03-12-2018, 04:09 AM

each lead acid battery as it ages changes internal resistance based on how much crud migrates off the cells and drifts to the bottom of the battery case and eventually starts to short out the cell... also as the chemicals move off the plates, this means that each plate and cell has less capacity.. so a new battery will eventually fail with age... AGM batteries are made in a way to limit the chemical change and other chemicals have been added to the plate material to slow the charge process down to prevent overheating and plate damage....

That said... its good to replace all the batteries at the same time.. we often will spend days off of shore power... we have (6) 6 volt batteries, in series and parallel to make up our battery bank.. I replaced them last summer after 2 of the batteries started to gas off excessively during use and charge... this gassing off was evident by moisture on the top of the two batteries where the rest were fine..

These 2 batteries limited the ability of all the batteries to take on a full charge..

In your case I would have changed all the batteries, and would have made them all the same brand and part #, so that through time they had the same wear pattern so to speak..

I also have (2) 2000 watt gen sets and try to use only one most of the time, starting the second one to power up during the time the wife wishes to run both the blow drier and the curling iron at the same time.. or some of the stuff in the kitchen....

I have acquired (4) 90 W, Samsung panels off a project that was d-commissioned but have yet to install them.. waiting to see if the wife wants to trade 5ers first...

hope this helps some in answering your questions

twinboat · 03-12-2018, 05:26 AM

I have been using 1, 12 volt tied to 2, 6 volt batteries for over 3 years now.
The under step compartment only fits one battery so the pair of 6 volt series batteries are in another bay close to a 1000 watt inverter I installed.

With no switching between batteries, I have been discharging and charging all three together with my 55 amp converter, 300 watts of solar and/or the MH alternator.

The original 12 volt battery did die last summer, and was going along for the ride, but I don't know how old it was. It didn't seem to be dragging the others down, as it wasn't shorted internally.

Although with one dead, I still had enough capacity to make it thru the night with lights, pumps, Satellite TV and occasionally some heat. I only discovered it being bad when I disconnected it from the 2, 6 volt ones and it's voltage dropped off quickly.

I swapped in another " good " 12 volt battery and are still running it that way.

My setup doesn't fit most of the rules, but since I'm not in the middle of the ocean or up in space, it works for me.

I say, give it a try, it worked for you before, it should work again.

**Spdracr39** · 03-18-2018, 07:53 AM

It will work but you do not get the most out of your batteries unless they are all equal age and capacity. So not perfect but it will work and unless you are keeping a spreadsheet on performance of each and comparing you probably won't notice a difference.