Dual charge scenario

2 Posts
Aug 5, 2009 01:07 pm
Dual charge scenario

All, I have a current 12 volt solar setup on some property.

4x Trojan T-105's (flooded lead acid)
Xantrex c35 charge controller (overkill for now, yes)
Kyocera KC85T (5 amp, 12volt) panel

I was given 2 AGM batteries that are about 5 years old. Naturally, putting AGM's in with plain lead acid batteries isn't a good idea. Not to mention the age of the AGM's (the Trojan's are less than 1 year old).

Any suggestions on how to implement those into my system? I've been reading up on isolators but it doesn't sound like a good idea, mainly because of the precious resources used by the isolator itself.

I've seen dual charge controllers out there (not sure at this point if they have dual voltage output levels as well?) , but what I am wondering is what would be the logical way to switch the DC output between battery banks, for AC inverter's sake?

Assuming a dual charge controller would work, I guess I would sell my current Xantrex controller. Also if there is no "automatic" way to switch between battery banks, I could use the 2 AGM's for 12 volt usage (ie, a DC fan or electric cooler).

578 Posts
Aug 5, 2009 05:48 pm
Re: Dual charge scenario


this may do the job for you.  both battery banks must be 12v, and the array must be 12v nominal


it can charge two banks from one array, and the battery banks can be set independently for flooded or sealed.

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184 Posts
Aug 6, 2009 08:48 am
Re: Dual charge scenario

I was faced with a similar problem last year.  I wanted a solution that gave top priority to charging my main battery bank, and use excess energy to keep the spare bank charged.  Like you, I wanted to automate the process.  I've posted my solution here:  http://solarjohn.blogspot.com/2008/10/system-automation-for-spare-battery.html
I hope this helps. Let me know.

2 Posts
Aug 6, 2009 11:00 am
Re: Dual charge scenario

James. Thanks for pointing out the Morningstar controller .. I couldn't find any other ones out there. I guess there aren't any?

John, that looks like a really nice setup. I didn't realize the Morningstar's had all that functionality. I don't think my Xantrex can do that. Do those relays' consume alot of power? On your setup that's not a big deal, I've only got one 5amp panel for now though.

at this point I'm thinking of skipping the gifted batteries, need a better inverter and more panels. They're only 65ah each anyway, not a whole lot to work with when compared to the Trojan batts.

If I did move forward, I would do the battery selector switch and use the AGM's as backup power like yours. I can see the serious downside though if it was left switched to 'both' for an extended period of time.

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