Dewalt DC9360 series/parallel discharge circuit

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slbaker
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I have circuit-board layout program on my PC and I design circuit boards as one of my hobbies.

I would like to collaborate with others interested in designing a circuit board
that would accommodate 3x2 Dewalt DC9360 batteries and work correctly
with the in-pack bms circuits. A built-in charger interface that would allow charging
all 6 batteries in parallel would also be desired, as well as the ability to run
with either 2, 4, or 6 DC9360s.

Let me know what you think.

Thanks,
Scott

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reikiman
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Re: Dewalt DC9360 series/parallel discharge circuit

I've spent a lot of time looking at the innards of those batteries.

I don't think a circuit board is necessary. What's required is

  • For discharge connect the positive-and-negative-most poles of all battery packs in parallel
  • For charging connect the BMS harnesses in parallel, heading to one BMS unit, then drop that one BMS unit into a charger

At least in my case I've been working towards a 5x1 setup rather than the 3x2 you say. I'd think for charging the packs you could go with a 6x1 arrangement to charge it.

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slbaker
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Re: Dewalt DC9360 series/parallel discharge circuit

Hi Dave,

>> For discharge connect the positive-and-negative-most poles of all battery packs in parallel

But if you do that, then you're bypassing the battery-protection circuit in each BMS.

>> For charging connect the BMS harnesses in parallel, heading to one BMS unit,
>> then drop that one BMS unit into a charger

What about balancing? Don't you need the BMS in each Dewalt pack to balance
the individual cells in the pack?

Thanks,
Scott

reikiman
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Re: Dewalt DC9360 series/parallel discharge circuit

Quote:

>> For discharge connect the positive-and-negative-most poles of all battery packs in parallel

But if you do that, then you're bypassing the battery-protection circuit in each BMS.

Maybe I'm misunderstanding what you're planning to do. There are many who have done as I have and bypassed the BMS for discharge.

Quote:

>> For charging connect the BMS harnesses in parallel, heading to one BMS unit,
>> then drop that one BMS unit into a charger

What about balancing? Don't you need the BMS in each Dewalt pack to balance
the individual cells in the pack?

The BMS connects to each cell, so when I wire the BMS harnesses in parallel the BMS is connecting to each parallel'd cell.

__________________

- David Herron, Green Transportation Examiner, Green Transportation Info, The Long Tail Pipe, Electric Race News, davidherron.com, 7gen.com, What is Reiki
- Charger bike (rebuilt), Electrified Electra Townie, 1971 Karmann Ghia

efreak
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Re: Dewalt DC9360 series/parallel discharge circuit

there are a at least two circuits being tested as i understand in the endless-sphere forum and they are mainly to protect the cells via the lvc .

that is by far the biggest concern with this chemistery.

the over dischrge of not properly balanced cells.

http://endless-sphere.com/forums/index.php

hope that helps

efreak

slbaker
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Re: Dewalt DC9360 series/parallel discharge circuit

Thanks for the link.
There is an awesome post there on "The care and feeding of a123-based packs..."
Just what I was looking for.

Regards,
Scott

spinningmagnets
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Re: Dewalt DC9360 series/parallel discharge circuit

Dear slbaker, I am new at this, and I'm doing my home work now before I start spending. I am leaning towards converting a bike to electric with 12V SLA's, and once those batteries finally wear out, upgrading the batteries to something better.

From what I've gathered, more volts will give me higher speed, and more hill power. Adding an additional battery string adds range. The idea occurred to me that if I had a pair of two 12V battery sets in side luggage bags (panniers?), I could use 24-volts in parallel for range, and switch to 48V in series for the hills.

Would this work? Is this similar to what you're talking about (using 2,4,6 DeWalt batteries)?

If yes, what controller, or do I need a custom unit?

I am very mechanical, but I'm just learning electrics. I once tried to fix a computer with a sledgehammer, but it just made it worse...

"If at first you don't succeed, don't try skydiving" -Henny Youngman

slbaker
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Re: Dewalt DC9360 series/parallel discharge circuit

The total amount of energy (charge) stored in the 4 SLA batteries of your proposed system does not change whether you configure them for 24V or 48V. So it seems to me that you should be able to get similar range for either the 24V or the 48V system. The 48V system would be capable of supplying more power (energy/time) which can be helpful for hills, etc. so, if I were you, I would just build the 48V system. Things that will affect your range would be the efficiency of your motor/controller and how fast you ride, how much starting and stopping, how much weight you're hauling around, your tires and tire pressure, etc.

In the configuration that I was thinking of (2,4,or 6 DeWalt packs), it would always be a 66V system.

Frying Pigeon
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Re: Dewalt DC9360 series/parallel discharge circuit

I just built something like what you are talking about. I made a printed circuit board (I used a sharpie pen rather than a computer, a la some guy on YouTube--very easy) that treats the batteries as two separate banks and uses three dpdt relays to switch between series and parallel. One relay takes battery bank A's neg and connects it to battery bank B's neg, except when the relay is on, in which case A neg connects to B pos. The second relay connects B pos to A pos, until the relay clicks on. Then B pos connects to A neg. The third relay takes B neg and normally routes it to the controller's bat neg , but when the relay is on, it connects directly to motor neg. A pos is the pos terminal for both motor controller and motor pos.

I did this because I could find relatively inexpensive 36v pwm controllers on ebay, but nothing that could handle 72 volts. The switcher lets me start on 36 v through the controller, but then lets me shoot 72 volts directly to the motor once the controller tops out. This is on a brushed motor rated for 350 watts at 36v, by the way. It ain't purty, but it works.

The relays are Bosch-type 12v automotive relays, probably 30 or 40 amps, wired in series to draw 36v. There is probably a better way to do this with a 3pdt relay, but I haven't found a cheap one that can take more than 10 amps. If one of my 12v relays fuses in the on position, sparks will fly, I think. Hence, each battery has a fuse as does the controller. I should put one on the motor too.

I charge the DeWalt batteries through the bms, and bypass for discharge.

GA Joe
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Re: Dewalt DC9360 series/parallel discharge circuit

The scheme with the 3 relays to provide a turbo boost is very clever.

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