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# Wiring batteries help

#1
09-18-13, 08:51 AM
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Join Date: Sep 2013
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Wiring batteries help

I'm looking to add lighting to an enclosed trailer of mine and I'll be using a solar panel on top connected to a battery inside. I'd like to be able to use the lights while the vehicle isn't attached, that's why I went with the battery/solar panel.

But basically I have 3 12V 7ah batteries I took out of an old go kart. The batteries right now are connected in series and the voltage measurement from one end all the way to the other reads around 30V or so after being charged overnight (they were completely dead before). After measuring each battery individually, the two on the edges read ~9.5 and the one in the middle read ~11.25. Can someone help me interpret this?

Also, I'm looking to wire these to some LED strip lights that are 12V specified. Is there a way I could wire all 3 batteries to put out a total of 12V, but have triple the battery life?

And lastly, the charger puts out about 43V. Is that ok for charging these batteries or do I need a 12V charger?

I'm pretty new to battery electrical stuff so any help is much appreciated! Thanks!

#2
09-18-13, 09:16 AM
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Batteries can be wired 2 ways, series or parallel. Series is + to - to + to - to + to -. That would give you over 36VDC if your batteries were all fully charged and functional (which apparently they aren't based on your voltage readings.) Actually it would be about 40V. The batteries won't last any longer than the capacity of each individual battery.

The other way is parallel where the +'s are all connected together as are the -'s. This gives you just over 13VDC (fully charged) and they will supply power for 3 times as long as a single battery.

All this assumes the batteries are completely equal in capacity and condition. Unlikely they are.

You can't use that charger if you wire the batteries to supply 12V to the LEDs.

Typical LEDs use so little juice, I would think one good battery could probably run them all night unless you have a real disco setup in there.

You'd probably be better off ditching the used batteries and buying a cheap car battery (deep cycle marine type would be best, but more \$\$\$).

#3
09-18-13, 09:17 AM
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You need to hook them up in parallel. Then it will be 12 volts with 3 times the amps.

the two on the edges read ~9.5 and the one in the middle read ~11.25. Can someone help me interpret this?
The batterys are dead. You can try to bulk charge each one to burn off the sulfer and see how they make out. The only true what to test that is best is with a hydrometer.

If you have a bad cell in any of the batterys after bulk charge to burn the sulfer off then the batterys are garbage. Recycle them...

Your best option when you get new batterys is to get 6 volt deep cycle golf cart batterys. You wire them different, but these are meant to drain down low and recharged.

see how 6 volt is wired different.

Additionally if you do not want to damage those new batterys from overcharging with the solar you need a good 3 or 4 stage charge controller. 4 stage will bulk, absorption, float, equalize . 3 stage leaves off the equilize part that will burn off the sulfur every so many hours.

Something like this will run \$150 bucks or so.

And lastly, the charger puts out about 43V. Is that ok for charging these batteries or do I need a 12V charger?
You need 12 volt panels... Do you have them wired wrong too?

You want all 12v lighting and such is your goal....and appliances if you can...This will be a 12v system just like an RV....

But you can also use an inverter for some low wattage 120v stuff..

#4
09-18-13, 09:28 AM
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If you are using old batteries... that were previously dead... and only come back to 9.5 or 11.25 volts after a overnight charging then the batteries are shot. You may be able to get a exchange credit for them when you buy a new battery or at the minimum take them to a recycling center.

What does your charge say is it's output voltage? Basically "no" a 43 volt charger can not be used to charge a 12 volt battery. That charger was probably used for a golf cart that had multiple batteries in series creating a 36 volt system or the charger is bad or your reading is incorrect. You need a charger intended for a 12 volt battery to charge a 12 volt battery. If you had a series of good batteries wired together then a charger intended for 36 or 48 volts could be used, but that's not helpful for your desired 12 volt lighting system.

#5
09-18-13, 10:06 AM
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Join Date: Sep 2013
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I bought a set of 36 6x6 cells with the tape and stuff off ebay. I haven't wired it yet. I'm not even sure how to wire it but I know there's lots of info out there! Or I can just come back here when I get around to it.

And the batteries are connected in series so that makes sense why it came with a 43V charger or whatever it's rated at.

So when you say these batteries are dead, does that mean they just don't hold as much charge? I mean they are LED's so 3 of these batteries in parallel should still be plenty, even with them being "shot", right?

#6
09-18-13, 10:21 AM
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I guess I don't understand the term "set of 36 6x6 cells with the tape and stuff"?? Per your first post you have 3 batteries (whether they be sealed units or battery packs), all three of which are reading lower than the rated 12+VDC.

If you put one bad battery in circuit (parallel or series) it will degrade the entire setup. Basically that one bad battery (or bad cell in a sealed battery) will drag the rest of them down with it. Imagine a team of 12 sled dogs. One dies and has to be dragged by the others...they won't be as fast or be able to run as long with the dead weight. Sorry for the visual it's just what came to mind.

Wired in parallel, your voltage will probably be in the 9.75-10.25 range...but will go down pretty quickly once a load is applied. Maybe your LEDs will light, maybe they won't....but they won't be operating properly and as explained, you'll have a charging problem.

#7
09-18-13, 10:24 AM
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What are 36 6x6 cells? Are you talking about batteries or LED modules?

If your batteries were in good condition then having 9 or 11 volts would mean they are dead as in need charging. Since you charged them overnight and only got up to 9 or 11 volts dead means time to buy new batteries. If you want to try using them I would pick the best one. Probably the one that got up to 11 volts and use it to power your lights. The big problem will be that the batteries are shot, dead, garbage... and have lost most of their ability to store a charge at any voltage.

Charge up your 11 volt battery using an 12 volt battery charger. Then let it sit for a day or two and check it's voltage, then check it a week later. This will give you some idea how well and how long it can hold a charge. A good battery, fully charged would be about 12.6 volts.

#8
09-18-13, 12:28 PM
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Join Date: Sep 2013
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Sorry, the 36 cells comment was in response to lawrosa about the solar panels being wired wrong. I have 36 6x6 solar panels.

#9
09-18-13, 02:19 PM
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So you need to put the cells togther and make one big panel correct? PITA... Should have just bout the premade panel..... Just my opinion...

You need to wire batterys for a 12v system.

After your panel is togther how many watts will it produce?

What LED lights do you want to use?

List the make and model of the charge controler you have...

As dane stated this set up you got was probably for a higher voltage golf cart system or something with a higher voltage... You need to start thinking in 12 volt terms like a RV runs on.

The 12 v fuse panel will be for any 12v lighting or appliances you want...Such as LED,s, 12 v lights such as for RV's which use automotive bulbs...etc...

You could add an invertor as shown and put an outlet in the trailer you have...

#10
09-18-13, 02:20 PM
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You want to save time and money and only looking for a light? Get a hand crank lantern. Crank it and it charges....

#11
09-19-13, 08:23 AM
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Join Date: Sep 2013
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The cells are 6x6 I think 4w each. I'm pretty sure they were rated at .5v each as well. I do not have the charge controller yet. And the batteries I have came off an old go kart.

I already have the LED's, solar panel kit, and a switch for the lights (yes it's a 12v switch). I just need the charge controller and now the batteries.

And the trailer is going to be used as a mobile work station for job sites so I want to have something professional looking.

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