Putting old batteries to use

Steven Lake · March 2012

Ok, I've got a question. I've got a couple of random stray batteries salvaged from old UPS's laying around the house (they're still in great shape, so I figured to use them wherever I could) that I want to put back into circulation. One is a 12ah 12v battery, plus I have two 7ah's and a 9ah I intend to use for some random projects. What would be the absolute minimum panel needed to charge these? I'm thinking of raw size here, not watts. The smaller the footprint, the better.

For example, would one of these work: Solartech SPM005P-R: 5 Watt 12 Volt Solar Electric Module

It doesn't need to fully charge the battery all that fast, but it does need to have a small footprint.

EDIT: PS, just to refresh my memory, all I should need for this setup is the panel, right? If it's just 5 watts it shouldn't need the charge controller, correct? Also, doesn't the panel come with its own blocking diode, or do I need to add that to the setup too? Just trying to make sure I keep this as small and minimalistic as possible.

westbranch · March 2012

Re: Putting old batteries to use

Dealing with the rule of thumb, , of 5% of the large battery's (12A) amp rating supplied by the panel 12A x 5% = .6Amps needed.. that panel supplies ~0.3 Amps so you would need 2 panels or 1 10 watt panels roughly...

techntrek · March 2012

Re: Putting old batteries to use

They are sealed gell cell so you need to be careful to use a charge controller with the proper voltage settings. If they vent, they are toast. How long have they been sitting uncharged? They may be bad...

Steven Lake · March 2012

Re: Putting old batteries to use

westbranch wrote: »

Dealing with the rule of thumb, , of 5% of the large battery's (12A) amp rating supplied by the panel 12A x 5% = .6Amps needed.. that panel supplies ~0.3 Amps so you would need 2 panels or 1 10 watt panels roughly...

Ok, that's what I wanted to verify. One 10watt panel minimum. Got it.

techntrek wrote: »

They are sealed gell cell so you need to be careful to use a charge controller with the proper voltage settings. If they vent, they are toast. How long have they been sitting uncharged? They may be bad...

Yeah, they're all AGM. The 12ah is the most recent addition to the stash so it's been used as recently as today as that's when I retired the UPS it was in. The other three haven't seen any action in a few months, so I plan to drop them on a charger sometime soon to top them off again. As for the charge controller, would this be enough: SunGuard 4.5 Amp 12 Volt Solar Charge Controller

Also, is that all I'll need? Just the charge controller and the panel? I've got the wires and the ends to link all this together, so I won't need those. The only other thing I can think of I *might* need is a blocking diode. But if the charge controller already has that, or even the panel, then I'm golden.

BB. · March 2012

Re: Putting old batteries to use

Yep--A good start... You really do not even need a blocking diode--First the charge controller will block. Second the resistance of a 12 volt solar panel is high enough that it will not significantly discharge your battery bank.

-Bill

Jim45D · March 2012

Re: Putting old batteries to use

Steven Lake wrote: »

PS, just to refresh my memory, all I should need for this setup is the panel, right? If it's just 5 watts it shouldn't need the charge controller, correct? Also, doesn't the panel come with its own blocking diode, or do I need to add that to the setup too? Just trying to make sure I keep this as small and minimalistic as possible.

FYI: If it's any consolation to you. I have a Concorde PVX 1040T (104 amp. hr.) battery on a 10.2 watt, 12 V. Siemens panel putting out around .6 amps. The panel is hanging from my RV ladder by "S" hooks at a 70° angle, west facing. At this time of year, mabey it get's 3 hours of sun in the mid to late afternoon. It has been there for over two (2) years. Rain, shine...summer and winter. I just checked the voltage at 11: pm. The voltage is steady at 13.7 volts. The sun has been down for over 5 hours. I had considered using a cheap Morningside Sunguard 4.5 amp controller, (which I have) but never did. It seems to be fine just like it is. The battery is 7 years old, The panel, made in India is about the same age, bought from someone on E-Bay for $65. Experimentation is not cheap, but it may save a few dollars in the long run. You'll learn a lot by yourself that isn't hype.

If I had listened to a salesman, instead of trying it myself. I would have never tried it with a 10 watter without a controller. A AGM such as the Concorde, (according to their site) can handle a lot longer charge at 14.8 volts. That's why it is west facing. The most it could ever get at that position and angle is around 3 plus hours, if that. I just hung it there, and let come what may. Mabey it get's a little more. Depending on the AGM, it won't gas until around somewhere in the vicinity of 15.2 volts, and up. I was told it never needed equalization, and it hasn't been. Simply keep it properly charged. Go figure.

westbranch · March 2012

Re: Putting old batteries to use

Jim I think the main difference in results is that your setup is at 1/10 th what Steven's is, ie your battery is ~ 10 X the size of Steven's.
A 10 W panel will have him in the 5% charge range for those small batteries

Putting old batteries to use

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