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Old 11-20-2012, 10:52 AM   #1
can0n4
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Electrical Wizards we need your help

I'm an engineering/technology teacher at a high school in NY. One of the projects my students and I are working on is an electric motorcycle conversion. We've converted an 89 Ninja into a 48 volt electric bike.

Currently we've got a situation regarding charging. We have four 12V batteries wired in series. However, we would like to charge them with a 12v charger instead of a 48v charger in series. Can we leave the batteries hooked up in series and still charge each battery individually with the 12V charger?? Is this making sense??

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Old 11-20-2012, 11:01 AM   #2
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That should work. I would imagine the charge would evenly distribute across all 4 batteries. I know there are a few EEs on here so correct me if I'm wrong, but I think 12v vs 48v at the same amperage should only be a matter of charging time, correct? You're charging at 1/4 the required voltage so it will take 4x longer for a complete charge.
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Old 11-20-2012, 11:03 AM   #3
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you could but you'd have to disconnect the +side every time you recharge each batt
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Old 11-20-2012, 11:05 AM   #4
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you could but you'd have to disconnect the +side every time you recharge each batt
So you're saying disconnect and charge each one separately?
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Old 11-20-2012, 11:06 AM   #5
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That should work. I would imagine the charge would evenly distribute across all 4 batteries. I know there are a few EEs on here so correct me if I'm wrong, but I think 12v vs 48v at the same amperage should only be a matter of charging time, correct?
12v charger can only charge 1 12v batt at a time, he can use the 12v charger but it will take him 4 times more to charge all 4 batts.

Is better to get a custom made charger for 48v
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Old 11-20-2012, 11:09 AM   #6
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So you're saying disconnect and charge each one separately?
not necessarily disconnect each batt, just the +side of the batt pack source (I think it goes to his dc motor regulator)..
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Old 11-20-2012, 11:10 AM   #7
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Old 11-20-2012, 11:18 AM   #8
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Unless you want to rewire them in parallel when it needs charged, you would have to charge them separately. Elliott is correct.

I see no issue with charging them separately while still wired in series, but you want to disconnect the positive lead from the last battery in the chain.
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Old 11-20-2012, 11:19 AM   #9
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We have a keyed switch inline with the "+" terminal so we can disconnect the + end of the system from the motor controller. Our ultimate plan was to use four small 1 amp 12v chargers in the gas tank and wire each one individually to each battery. I guess we'll plug in and see what happens...


Thanks for the help guys. Its one of those situations where I'd hate to see something go horribly wrong and cause an injury/burn for one of my students. Its scary enough riding this thing as it is. I appreciate the support you've already given.

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Old 11-20-2012, 11:28 AM   #10
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We have a keyed switch inline with the "+" terminal so we can disconnect the + end of the system from the motor controller. Our ultimate plan was to use four small 1 amp 12v chargers in the gas tank and wire each one individually to each battery. I guess we'll plug in and see what happens...


Thanks for the help guys. Its one of those situations where I'd hate to see something go horribly wrong and cause an injury/burn for one of my students. Its scary enough riding this thing as it is. I appreciate the support you've already given.
That's a bit different. If your four chargers share a ground you'll be creating a direct short.

If you need to charge them simultaneously, you'll need to get a 48V charger.


Cool project by the way!
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Old 11-20-2012, 01:38 PM   #11
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Why do you have to use a 12V charger? There are plenty of 48V chargers out there for golf carts and whatnot.
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Old 11-20-2012, 08:30 PM   #12
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we'd like to fit them all inside of the gas tank, 48v might be a better option, but as of right now we've got the 12v chargers

so today we individually charged them with one 12v charger, one battery at a time, but from what i've read thus far, using more than one charger on each battery if they are all connected to the same power source may cause a short. We were going to run all four 12v chargers to one outlet. This guy linked below, did exactly that and says it works..... https://sites.google.com/site/lennon...2/emoto_step10
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Old 11-22-2012, 11:01 AM   #13
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I think it will only get the four batteries to a total of 12 volts....that is what you are putting in. Now, if you can get a relay/contactor setup, you could charge all four at a time with four chargers. You would need the contactors to be rated to the current you need to supply on the bikes side though.. (all batts will be disconnected by the contactor and can then be charged seperately) -you would have to make one of the batteries work the coil to the contactor/s.
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Old 11-22-2012, 05:24 PM   #14
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Quote:
Originally Posted by can0n4 View Post
I'm an engineering/technology teacher at a high school in NY. One of the projects my students and I are working on is an electric motorcycle conversion. We've converted an 89 Ninja into a 48 volt electric bike.

Currently we've got a situation regarding charging. We have four 12V batteries wired in series. However, we would like to charge them with a 12v charger instead of a 48v charger in series. Can we leave the batteries hooked up in series and still charge each battery individually with the 12V charger?? Is this making sense??

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No.

Charge each battery seperate at 12 volts.

Either quick disconnect or whatever.

Or buy 48 volt charger.
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