Dewalt 36V (one way how to repair your blown BMS)

Batteries, Chargers, and Battery Management Systems.
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Doctorbass   100 GW

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Dewalt 36V (one way how to repair your blown BMS)

Post by Doctorbass » Jul 04 2007 6:14pm

I have received my 4 spare BMS and repaired my first dewalt 36V today.

I decided to post some pics that could help people to repair their blown BMS.. at least one way.

After reading many forum on the internet about that famous battery, i found that many people blow their bms and are unable to use it to charge the pack after it happened.

People often use the dewalt connector as + and - output and when they draw more than 15A, "the battery stop working"

This is du to a little 15A surface mount fuse inside the bms.

I found some pics of the inside circuit board and a part of the schematic.

I toke a couple of pics to help you to repair it even if it's possible...
Attachments
Simple repair blown BMS.JPG
Simple repair blown BMS.JPG (67.74 KiB) Viewed 13561 times
Opened BMS pic and real BMS compare.jpg
here is the little 15A fuse
Opened BMS pic and real BMS compare.jpg (68.16 KiB) Viewed 13569 times
Showing the 15A fuse and schematic.jpg
Schematic and real bms compare
Showing the 15A fuse and schematic.jpg (76.17 KiB) Viewed 13576 times
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Post by dermot » Jul 05 2007 7:12am

Here's an X-Ray of a DeWalt controller, just for amusement.
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dewalt-a123-x-ray.jpg
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Post by Doctorbass » Jul 05 2007 7:38am

dermot wrote:Here's an X-Ray of a DeWalt controller, just for amusement.
oh hoooo.!!!.....

Where did you find it?!!

Doc
CURRENT PROJECT: 2WD duo MXUS/Max-E ebike 32kW
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Post by TylerDurden » Jul 05 2007 8:36am

dermot wrote:Here's an X-Ray of a DeWalt controller, just for amusement.
Nice job... much easier than picking out all the potting!

(Exposing for the part numbers might be tricky)


Can we send you other stuff to xray?

8)
Have a Nice Day,

TD

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Post by dermot » Jul 05 2007 1:18pm

Doctorbass wrote:
dermot wrote:Here's an X-Ray of a DeWalt controller, just for amusement.
oh hoooo.!!!.....

Where did you find it?!!

Doc
I did it myself - having X-Ray and CT facilities available is sometimes useful - especially when opening up bits of kit where it is not obvious how to do it without breakage!

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Post by dermot » Jul 05 2007 1:21pm

TylerDurden wrote:
dermot wrote:Here's an X-Ray of a DeWalt controller, just for amusement.
Nice job... much easier than picking out all the potting!

(Exposing for the part numbers might be tricky)


Can we send you other stuff to xray?

8)
Sure, what do you have.... I know I have radiographs of my Heinzmann battery pack somewhere.

I already have electronic copies of the radiograph of my right wrist (fractured triquetral) after I got 'doored' by a stupid motorist a while back.

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Post by Doctorbass » Jul 07 2007 8:29pm

I received 2 used and bad Dewalt pack from my local Dewalt store yesterday.

Now i'm making one good pack with the two broken one by removing the bad cells inside. often, many pack under waranty are returned by customers and the problem is in most of the case that one or more cells inside are deffective. when they try to charge their pack on the DC9000 chager, the 3 led flash rapidly , indicating thios problem.

the rest of the cells are still good at all!.

From the 3 used pack I got for free, one (the 2006 22weeks) had only one cell deffective, the second one (the 2006 16 weeks)had 3 cells around 0.5V, and the last one(the 2006 27weeks) had 7 cells under 1.9V and the 3 last cells war at 2.35V.

These cells have a recomended discharge voltage cuttoff at 2V.

Now, a pics of the rebuilt of one fully fonctionnal pack:
Attachments
P1020151.jpg
the dremel is very usefull to separate the cells without damaging the link between those
P1020151.jpg (49.78 KiB) Viewed 3741 times
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Post by fechter » Jul 07 2007 11:14pm

Is that Flux-Clean stuff legal?

I need to find the free DeWalt battery store around here. :D
"One test is worth a thousand opinions"

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Post by Doctorbass » Jul 08 2007 12:23pm

The flux clean i have is legal here and distributed in Quebec province.

http://www.asalco.com

Doc
CURRENT PROJECT: 2WD duo MXUS/Max-E ebike 32kW
http://endless-sphere.com/forums/viewto ... =3&t=65764
-Fastest speed record 117 km/h on flat
-Fastest 1/4 mile@ 114km/h on flat and 16.316 sec
-Succeded to haul a 19200 pounds schoolbus!
113kmh Gianthttp://www.evalbum.com/3406
Mongoosehttp://www.evalbum.com/1947
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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by mjohnsn » Sep 04 2009 9:33pm

Hey Doc,
Your pictures helped me repair my dewalt battery.
I soldered a 15 amp mini blade fuse to the two poles of the blown BMS fuse.
Battery is now recognized and charges fine. Got a problem though. I run four batteries,two batteries in series for 72 volts, then another set batteries in parallel to the first set.
When I hooked the repaired battery into to the set, the BMS fuses blew in the other three batteries.
Any clues why? Any suggestions?
Thanks
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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by kfong » Sep 04 2009 10:45pm

Sounds like you don't have the batteries "diode isolated". Why not use the BMS like it was originally designed. You can pull 20amps instead of 15amps and the circuit protects itself if you go higher than that. It also shuts down when the batteries get too low. I went with the fused connector when I first started using these batteries. I ended up draining my pack too much and lost a few cells. I decided to use the onboard BMS the way Dewalt intended it to be used. I had to create a circuit board to allow the BMS to think that it's connected to a Power tool. Now you can run the packs without taking them apart and still have the 3-year warranty. http://www.endless-sphere.com/forums/vi ... 14&t=10986

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by momo » Sep 05 2009 6:42pm

hey kfong, I don't see the boards on your website. Do you have them on ebay?

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by kfong » Sep 05 2009 10:04pm

No, just on the link I pointed to. I need to do that. Just been busy with other projects. Just click on this link for all the details http://www.endless-sphere.com/forums/vi ... 14&t=10986
momo wrote:hey kfong, I don't see the boards on your website. Do you have them on ebay?

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by mjohnsn » Sep 06 2009 9:27am

Hey Kfong,
Yes my batteries are not dioded. Isn't dioding for sets in parallel? I hooked up this 'repaired" battery and it blew the battery next to it in series, two in a set parallel to it, but didn't affect a third set in parallel. Why did it blow the battery in series and only one set in parallel and why at all.
May eventually get to using bms, but for now I am just trying to figure out what is going on so I can get back to riding. Repaired this battery so I could go from a 4 pack to a six pack for my 22 mile commute. Now I am 1 up but 3 down and so only have a 2pack. ;-(
Novara Transfer Bike with Frontwheel 5305. 21 mile one way work commute

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by kfong » Sep 06 2009 12:06pm

Diodes act as one way valves. If in parallel, they keep each pack isolated. If in series they provide added protection from reversed contacts. Using them would of prevented your mistakes, since a fully charged pack will dump all it's energy onto an uncharged pack.

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by mjohnsn » Sep 08 2009 4:52pm

All packs were fully charged, I don't see why there was a "dump" from the repaired bms battery, but it sure acted like it. Is there something in the built in BMS fuse that limits current flow?

So do you add diodes between both serial and parallel connections? One diode for each battery? I have two non blown batteries left.
Hope I can keep them intact.
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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by EVnewbie » Sep 10 2009 12:26pm

No two batteries sit at the same potential,
If you take two fully charged batteries and run them in parallel, the stronger one will attempt to equalize the voltage difference between the batteries as fast as it can. Those A123 cells can dump 100+ amps so it overwhelms the BMS and fuses for the instant the packs try to equalize. The diodes will prevent "reverse flow" charging/discharging of the packs to protect your BMS and fuses. I have two blown Dewalt packs myself, need to get off my butt and change the fuses.

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by nineball » Sep 10 2009 10:37pm

Do Bosch packs have a fuse?
48v 1000w Rear Brushless Hub(Cracked Rim)/ Switched to 36v 500w E-Bikekit 28" 9c 9x7 (performs the same)
Keywin 60/72v 45A controller/w CA(smoked big time) Replaced with Methods 100v monster
(8) Bosch 36v Fat packs 72v + 3 12sla 97v Hot off charge
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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by docnjoj » Sep 11 2009 5:12pm

Yep! 60 amps!
otherDoc
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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by nineball » Sep 12 2009 12:00am

Gonna have to open 1 up then, I think I blew one. Thanks
48v 1000w Rear Brushless Hub(Cracked Rim)/ Switched to 36v 500w E-Bikekit 28" 9c 9x7 (performs the same)
Keywin 60/72v 45A controller/w CA(smoked big time) Replaced with Methods 100v monster
(8) Bosch 36v Fat packs 72v + 3 12sla 97v Hot off charge
30-40 mph cruise...has hit 50 (bike & trike)
Trike is done, got over 1200 miles update/2100+ miles studded snows for winter

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by mjohnsn » Sep 15 2009 7:47pm

Well! That didn't work.

When I first bypassed the blown fuses the packs were almost fully charged. I discharged them about 1/2 way on a six mile run and now the charger 'rejects' them. So, now I have four dewalt batteries with blown BMS that will not take a charge. Funniest damn flashing patterns though. One flashes one light slowly, one looks like it is doing the Macarena and two with have the 3 light flashing pattern of death. (think it means SOS).

Any one have a good schematic on how to best connect these 40 orphaned cells into a 76 volt power pack that will charge off one charger that I can take along on my commute?
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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by docnjoj » Sep 16 2009 7:54pm

Don't forget that at worst you still have A123 cells! 40 x3.7 is still 150 volts, or 75 //!
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E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by mjohnsn » Sep 25 2009 6:54am

Looks like I will have to make my own packs now. Haven't decided on 12s or 20s. Would prefer 20s, My 5305 likes the extra juice. Seems to be more charger/BMS solutions for 12s. So what do you use to charge your packs?
Novara Transfer Bike with Frontwheel 5305. 21 mile one way work commute

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by The Mighty Volt » Sep 03 2012 8:08pm

great thread, have been looking for info like this all over the place.

I am trying to rejuvenate some old DeWalt 36v batteries, I get the three-flashing-LED's a lot, what does this mean precisely?

How are people removing the epoxy?

Also, if the fuse is still intact {and therefore not needing to be replaced} how can I test for this? With a Multimeter and test for continuity be enough?

Thanks a lot.

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Re: Dewalt 36V (one way how to repair your blown BMS)

Post by Doctorbass » Sep 04 2012 10:42am

The Mighty Volt wrote:great thread, have been looking for info like this all over the place.

I am trying to rejuvenate some old DeWalt 36v batteries, I get the three-flashing-LED's a lot, what does this mean precisely?

How are people removing the epoxy?

Also, if the fuse is still intact {and therefore not needing to be replaced} how can I test for this? With a Multimeter and test for continuity be enough?

Thanks a lot.

Hello,

Usually it's just that one or more cells are below 2.5V. That's what make the bms to flash the 3 led on the charger. but sometime it's something else like the blown fuse or mosfet or corrosion etc.. but generally it's just a matter of recahrging the individual cell to the same level to the rest and to be at least above 2.5V.. than the pack will charge again .

Doc
CURRENT PROJECT: 2WD duo MXUS/Max-E ebike 32kW
http://endless-sphere.com/forums/viewto ... =3&t=65764
-Fastest speed record 117 km/h on flat
-Fastest 1/4 mile@ 114km/h on flat and 16.316 sec
-Succeded to haul a 19200 pounds schoolbus!
113kmh Gianthttp://www.evalbum.com/3406
Mongoosehttp://www.evalbum.com/1947
YOUTUBE---https://m.youtube.com/user/Doctorbasss
http://twitter.com/DocbassMelancon
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