I added a fourth battery to my 36V setup, but now need a bigger charger, so I now want to wire extra battery in parallel to one.

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dudemanaroo
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I added a fourth battery to my 36V setup, but now need a bigger charger, so I now want to wire extra battery in parallel to one.

... Is this possible? how would I wire one 12V battery to a series of three 12V batteries? Is there a relay circuit or some kinda switch setup I can install so that I can charge the 3 batteries with the old charger I have (36V) and then have an independent charger for the extra 12V battery??? maybe that is more complicated that just getting a 48V charger, ... or building one myself, is there a way I can modify a computer power supply to make a charger?

Main question I need answered... ---> How can I add one battery in parallel to one of the batteries that are in series with 2 other ones? I guess with diodes? Please help!!!

Thanks!

mf70
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Re: I added a fourth battery to my 36V setup, but now need a ...

You asked:

How can I add one battery in parallel to one of the batteries that are in series with 2 other ones?

The answer is, it's simple, but NOT recommended. The result will be a pack that is no better than what you started with. A pack is no better than its weakest link. By paralleling one battery, you are merely loading the other two batteries in the series chain more heavily. On charge, the weakest battery will end up being cooked while the charger is trying to fill up that paralleled pair. (if you were fooling around with scrap batteries, this would be a way to make a "composite" battery out of two low capacity deaders.)

If you want to upgrade to a 48V pack, you CAN add a fourth battery in the series string. You will get MUCH better power, and your existing control and motor will ~probably~ withstand the extra voltage (though remember that a fully charged "48V" pack can be around 53.2V).

Yes, your 36V charger wont work. If you are rewiring, I would recommend running all four batteries out to a common (Anderson PowerPole) plug and changing them in parallel at 12V using a common high grade 12V charger. To ride, you replace the charger plug with a jumper plug that rewires the batteries to series. I've used such a system for several years.

Mark

dudemanaroo
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Re: I added a fourth battery to my 36V setup, but now need a ...

Dude, that's GENIUS! No really, it is, no need for relays or crap like that, ... I thought of having my fourth battery have an independent charger, and then connecting it in series from the plug from the battery pack, in between where it plugs into the bike, but.... no need to do that now, cause of your amazing suggestion, thanks!

- The only problem here, is that I don't have a 12 V charger, can i make one? - Needs to cut off when charged of course. - Or could I modify my 36 V charger?

mf70
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Re: I added a fourth battery to my 36V setup, but now need a ...

Buy a good 12V charger. I've been very happy with the Vector 2/6/10 charger. It's now re-branded as Black & Decker, and about double the price I paid(???).

http://www.amazon.com/Black-Decker-VEC1087CBD-Battery-Charger/dp/B000EJTI4G

Shumacher also has comparable units. I find the Voltage reading very helpful.

When you are wiring the parallel plug, lead in the + power from the right, and the - power from the left. This makes sure the potential across each battery is comparable. Extremely small differences between the resistance of the leads can cause imbalances between batteries since each battery always is connected in the same way.

MF

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