Connecting Batteries In Series & Parallel

[jdbauman]

I was wondering if I am doing this correctly. I want to hook up two 36Volt Dewalt batteries in Series to get 72 Volts.

I then want to hook some up in parallel to increase the capacity.

My drawing shows how I think I would hook up the batteries in Series to the Controller. On the right I show two additional batteries hooked to each other in parallel. My question is, how would I attache these "parallel" batteries" into the Series hookup to allow me 72 Volts at 6.6 AH.

Thanks....

Okay, where did my drawing go? I drew it on paper and scanned it to a file, the I attached the file to the post...

JD

[/img]

 

[fechter]

Oops, no picture. Below the text box where you post, there's a browse and attach button. Use those. The img tags only work for URL's that are on the web somewhere.

I understand your question. It would be best answered with a picture.
I'll try to post one later.

 

[Lessss]

top row in series as one 72 pack

bottom row as one 72 pack

both together as two packs in parallel at 72




Or if you could parallel each 12V battery.

 

[fechter]

Thanks Lessss,

If the drill packs are kept intact with the BMS, then I think you could hook them up in either configuration, whichever is more convenient.

Lithium and lead-acid are OK in parallel. Nimh and Nicd are not recommended for charging in parallel.

Here's a picture of a series-parallel configuration that is like Lessss's lower one, called buddy pairing. Buddy pairing tends to keep the cells more equalized, but if you have a good BMS, that takes care of the balance anyway, so the middle jumper is optional.

 

[jdbauman]

Thanks for all the help guys... It makes sense to me now!!!

JD

 

[xyster]

I was wondering if I am doing this correctly. I want to hook up two 36Volt Dewalt batteries in Series to get 72 Volts.

Are you planning to bypass the dewalt BMS? Others who have done this, such as Magudaman over at visforvoltage.org, have found it necessary else the BMS fries.

 

[jdbauman]

Xyster, I was not planning on bypassing the BMS. I found this video from "biodiversivist" up in Seattle showing his ebike. I posted a message to him about bypassing the BMS and he states that it works fine without bypassing it. Here's my question to him and his reply...

My Question to Him:
Great Video... That is very impressive performance!
1. Are you bypassing the built-in BMS when attaching the batteries in Series and to the bike?
2. Do you use the standard DeWalt chargers?
3. Could you possibly show some pictures and explain how you hook up the batteries?
I am very impressed with your bike and would like to built one like it. Also there is a great Ebike forum called endless-sphere Would love to see you over there if you are not already a member... JD

Hi Reply:
1) Nope. Works great as is.
2) Definitely.
3) Will do so at "visforvoltage" when I get time.

I'll check out endless sphere. Thanks.


You can also see his video at this link:
http://video.google.com/videoplay?docid=-7683697561010759176&q=electric+bicycle&total=816&start=20&num=10&so=1&type=search&plindex=7

Xystem, I am a little confused as to whether this is a safe thing to do or not. If I don't want to bypass the BMS, would there be an advantage to using the Emoli V28's versus the DeWalt Batts?

JD

 

[Instant Karma]

I have been pondering going the Dewalt or Milwaukee tool battery route myself lately. I'd like to do it with cases intact for battery safety reasons mainly and warranty issues. I wonder when connecting the Dewalt in series with BMS installed if it matters if if the batteries are not paralled yet or are paralled. i.e. 36+36+36+ in parallel then connect to the other 3 parallel in series 36+36+36 or go 36 to 36 series then connect the paralleld batteries 3 or 4 whichever AHr you want. If the BMS fry in either Dewalt or Milwaukee while trying this stuff you can always open the cases up and remove the batteries and solder the packs yourself or send them off to be done for you. Actually Dewalt is closer to 33 volts in actual use so if you just use them in parallel for 36 Volt motors you'll be disappointed probably.

 

[xyster]

Xystem, I am a little confused as to whether this is a safe thing to do or not. If I don't want to bypass the BMS, would there be an advantage to using the Emoli V28's versus the DeWalt Batts?

I haven't studied the issue as much as you have. But I distinctly remember a thread from the old v forum where somebody fried their dewalt BMS after either wiring in parallel, series, or both like you want to do. Magudaman, who's now over at the new V -- visforvoltage.org -- tapped in to each pack's main power leads beneath the BMS's and then wired those leads together to make his pack. This way the BMS was bypassed on discharge, but still used during charging and for cell balancing. Jondoh and Maytag here know all about the V28 packs and their BMS's. If it was me, I'd contact Magudaman about his Dewalt pack scooter, and look at Jondoh's and Maytag's V28 threads here. Or I'd just play it safe and tap in beneath the dewalt BMS.

 

[jdbauman]

Lessss, I have been doing some experiments hooking up some home variety 9V batteries in the configurations you described. When I hook these things in Parallel, they really heat up. When I hook them in Series, I do not notice them heating up at all. Is this normal?

Also, when attaching batteries in the "buddy pairing" System, can I buddy as many batteries as I want? Could I add a third row (i.e. an extra battery) to each buddy pair without damaging anything? I guess a battery menage a trois of sorts...

JD

 

[Rassy]

fechter, in your "buddy pairs" diagram I think it is easier to follow if the "pairs" are directly connected, + to + and - to -, to build the individual 24V pairs, and then making a single - to + between each set of buddy pairs. Then it is easier for a novice to see how to expand to more voltage (buddy tripples?) or more AH with additional buddy sets. So my actual question is, is there any reason for the cables being shown the way they are in the diagram?

 

[fechter]

You're right, I should re-draw that one to make it more clear.
It doesn't really make any difference electrically.

 

[Lessss]

you are putting - to - and + to + on the buddy pair?

 

[Rassy]

Thanks fechter. I just went through your "Series and Parallel" thread in your new EV Basics section and you made a real good and clear presentation there that everyone should take a look at if they still have questions in this area.

 

[oatnet]

JD

Oh no, another JD! :lol:

-JD

 

[op337]

Do you run your packs lets say your 14s 58v x 3 paralleld for 15ah balanced acorss the taps or not benefits/drawbacks.
sorry if its a common question just couldnt spend more time searching the forums.

thanks .

 

[Gregory]

Does this help? http://endless-sphere.com/forums/viewtopic.php?f=14&t=57502

Personally I parallel at the balance connectors.

 

[mark5]

Ykick, psycholist, & dogman on paralleling balance leads
http://endless-sphere.com/forums/viewtopic.php?f=2&t=32436&start=0#p471103
http://endless-sphere.com/forums/viewtopic.php?f=2&t=32436&start=0#p471485
http://endless-sphere.com/forums/viewtopic.php?f=14&t=41462&p=857947#p857883
http://endless-sphere.com/forums/viewtopic.php?f=14&t=41462&p=857947#p857947
http://endless-sphere.com/forums/viewtopic.php?f=4&t=32096&hilit=Opinons+vary#p464943