DeWalt pack w. builtin BMS: Long term experience?

jag

10 kW
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Feb 16, 2009
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I'm looking to use two or four DeWalt 28V packs "off the shelf" to power a small front hub motor like the Cute. I'm hoping to put together a newbie friendly plug-and-play package for my wife using the packs and original DeWalt charger.

In some early 2007 posts in the "A123" thread ggoodrum reported that cells weren't balanced when he took them off the DeWalt charger. Is that a problem others have noticed? Seems like in that thread people use the cells, but ditch the built in BMS.

kfong on the other hand built an interface board that plugs directly into the cells. Probably ES members have tried to use this and other solutions to just tap into the original packs. Any long term experience with this setup?

I'm also wondering if there is some quality problem with the DeWalt packs? Why otherwise do people like drbass get loads of pack with broken BMS? Could poor quality/many customer returns be a part reason why DeWalt is pulling them off the market? Maybe this is more a problem for people who use them with power tools, than on an ebike?

Any insights would be valuable.
 
A related question: In the DeWalt system, are the chargers special in any way? Ie only work to charge DeWalt packs? Can only charge one pack at a time?

Or are they just constant current then constant voltage like a normal charger?
Has anyone measured the actual top output voltage of a DeWALT DC9000?
Or even better the charge voltage/amps curve?
 
jag said:
I'm looking to use two or four DeWalt 28V packs "off the shelf" to power a small front hub motor like the Cute. I'm hoping to put together a newbie friendly plug-and-play package for my wife using the packs and original DeWalt charger.

In some early 2007 posts in the "A123" thread ggoodrum reported that cells weren't balanced when he took them off the DeWalt charger. Is that a problem others have noticed? Seems like in that thread people use the cells, but ditch the built in BMS.

kfong on the other hand built an interface board that plugs directly into the cells. Probably ES members have tried to use this and other solutions to just tap into the original packs. Any long term experience with this setup?

I'm also wondering if there is some quality problem with the DeWalt packs? Why otherwise do people like drbass get loads of pack with broken BMS? Could poor quality/many customer returns be a part reason why DeWalt is pulling them off the market? Maybe this is more a problem for people who use them with power tools, than on an ebike?

Any insights would be valuable.
I've been using four of the DC9360s in a series parallel discharge circuit, as described here:
http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=19322


Well over 200 cycles and 2000 miles without any problems. Batteries are over 3 years old, according to date code. I often leave the batteries in the DC9000 charger overnight, since it is alleged to improve balance. I will not open the packs to check cell voltages until a decrease in capacity appears. Dewalt still provides a 2 to 3 year warranty on their system, and my discharge circuit mimics a power tool.
 
CyclemotorEngineer said:
jag said:
I'm looking to use two or four DeWalt 28V packs "off the shelf" to power a small front hub motor
I've been using four of the DC9360s in a series parallel discharge circuit, as described here:
http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=19322


Well over 200 cycles and 2000 miles without any problems. Batteries are over 3 years old, according to date code. I often leave the batteries in the DC9000 charger overnight, since it is alleged to improve balance. I will not open the packs to check cell voltages until a decrease in capacity appears. Dewalt still provides a 2 to 3 year warranty on their system, and my discharge circuit mimics a power tool.

Thanks for the update and article link. (I also liked your knol article in the signature.)
Am I guessing right that your 200 cycles in for the 4 36V battery system on cyclomotor detachable front motor setup in your image icon?

Anyone else has experiences to report after using the DeWalt packs?
 
jag said:
Thanks for the update and article link. (I also liked your knol article in the signature.)
Am I guessing right that your 200 cycles in for the 4 36V battery system on cyclomotor detachable front motor setup in your image icon?

Glad to read that you liked the Knol. Yes, the drive setup is still as pictured, although I went to a more powerful motor and stronger bicycle frame, manufactured by Surly.
 
The two ways people posted using the DeWalt packs seem to be
1. Just harvest the cells, replace BMS
2. Use the complete toolpack with enclosure and everything.

Did anyone try:
3. Dissassemble toolpack, discard plastic enclosures, but keep BMS. Wire together into larger pack with a charging interface? Advantages for me would be:
+ Lighter weight and more compact. I'm planning to built a 2s2p from 4 28V toolpacks and put in a triangle framebag.
+ Can charge with a cable on bike instead of removing individual tool packs and putting in DeWalt charger
(How many connections does the DeWalt charger make to the pack? 2 or 3? )
+ Easy to occasionally check individual cell voltage manually to spot if DeWalt BMS appear to be failing.
(If the DeWalt BMS fails, but I spot it in time I can buy a separate BMS to replace it)

Experiences, observations or thoughts?

B.t.w. did anyone order from Toolking and ship to Canada? Any hickups?
The other place I can buy is from ebay seller "jeanclaudecayerent" in Ontario. Anyone has experiences with him? Looks like he has a power tools business.
 
jag said:
The two ways people posted using the DeWalt packs seem to be
1. Just harvest the cells, replace BMS
2. Use the complete toolpack with enclosure and everything.

Did anyone try:
3. Dissassemble toolpack, discard plastic enclosures, but keep BMS. Wire together into larger pack with a charging interface? Advantages for me would be:
+ Lighter weight and more compact. I'm planning to built a 2s2p from 4 28V toolpacks and put in a triangle framebag.
+ Can charge with a cable on bike instead of removing individual tool packs and putting in DeWalt charger
(How many connections does the DeWalt charger make to the pack? 2 or 3? )
+ Easy to occasionally check individual cell voltage manually to spot if DeWalt BMS appear to be failing.
(If the DeWalt BMS fails, but I spot it in time I can buy a separate BMS to replace it)

Experiences, observations or thoughts?

B.t.w. did anyone order from Toolking and ship to Canada? Any hickups?
The other place I can buy is from ebay seller "jeanclaudecayerent" in Ontario. Anyone has experiences with him? Looks like he has a power tools business.

Ok, I can be of some limited assistance here, I am about to do virtually the same set-up your describing with an Amped Bikes geared rear hub motor kit, but with 2s3p using six 28volt dewalt batteries in a triangle bag. I am also going to use kfong's interface boards as I have used with my dad's E-bike set-up which is a DD Amped Bikes rear hub motor kit. Dad's set-up is currently three 36volt dewalt batteries in parallel, and he has a fourth battery on the way. We have had good results with this set-up, but there have been several technicalities to work out along the way.

Are you using a kit that normally operates at 36volts? By running 2s 2p your true voltage should be 52.8 volts, so in my mind it makes a "sag resistant" 48volt set-up for years later when the batteries are operating at 80%. I am using a geared kit because I am wanting light weight over brute force, and hill climbing is 99% of what my hub motor will do, otherwise I will just be human powered, so I am wanting to keep the weight to a minimum.

I think you will find unless your doing around a 5 or less mile commute, that just four 28volt packs won't pack that much of a punch, depending on what your wanting.

If your wanting something pedal free for short distances, with a quick recharge time (you WILL however need one charger per battery to achieve this) of 30-60 min, then this will be fine, but it won't be a rocket, just a good steady short range power source.

If your going to be pedaling, I think you could easily double that range with out sacrificing top speed, but this will be a work-out, not just a joy ride :)

I think to get about 20 mph on the flats, you can expect 10-15 miles range with this set-up with most kits, maybe more with geared kits (remains to be seen at least in my personal experience) but if your going to be climbing a lot of hills, or wanting to max the speed, I think this amount of batteries might prove inadequate for anything faster/longer distance between charges.

I suspect for my own build that I will eventually be going for something in the neighborhood of 8-12 packs, 8 packs provided they are the same series/parallel set-up, will only make for a 7.2 AH battery, 12 packs a 10.8 AH battery.

IMHO, this is a great way to go, even if I end up going with something in the neighborhood of 16 packs since I can get the BMS + A123 cells at less than $5 per cell (on a good ebay deal) and in the end, I might end up trying something like you mentioned, making larger packs to go with the BMS and build them to the desired shape to keep compact and light weight.

I think best of all is the superior amount of recharge cycles the A123 batteries have. That is their main selling point to me.

I am also interested about other people's ideas for charging/building these cells into different sized packs, I am trying to keep everything at minimum cost, but also fastest recharge time possible, would want to stay under 2hr charging time to keep it feasible as a commuter.

Also, so far the only real problems with the dewalt BMS I have seen are the 15amp fuse (used only while charging) blowing on one of our older packs (2006 manufacture date, very easy to fix) also of note is the batteries only have a TWO YEAR warranty, where as the TOOLS have a three year, so it might make a difference which battery to buy on ebay if one's a 2006 and the other manufactured later.

Oh on another note, I don't have any personal experience with "jeanclaudecayerent" on ebay, however I have seen where he sells the DC9000 chargers for cheap, then charges about 3x the price of the item in shipping :shock: , so just look closely at what your considering to bid on.

You can get good reasonable priced 28 volt packs on ebay, just have to watch for the better deals.
 
LI-ghtcycle said:
I think you will find unless your doing around a 5 or less mile commute, that just four 28volt packs won't pack that much of a punch, depending on what your wanting.

I'm planning to pair the 2s2p 28V DeWalt with a 250W, 48V "Cute" motor for a very lightweight (1.6kg motor + 2.4kg batteries) setup. Range is likely about 20km unassisted, but can easily be doubled with pedalling. This is for the wife who will not want anything heaver added to her bike.
 
As I started to dig up some ref for you I noticed that they already posted.I also noticed you were mixing apples and oranges.Drbass never sold faulty dewalt pks.anywhere.period.
 
LI-ghtcycle said:
I suspect for my own build that I will eventually be going for something in the neighborhood of 8-12 packs, 8 packs provided they are the same series/parallel set-up, will only make for a 7.2 AH battery, 12 packs a 10.8 AH battery.
The current build will be lightweight for the wife. I'm also tempted to do one for myself and then I'm likely to use 3s3p or 3s4p combined with a BMC V2T, but that would have to be later. (I have no immediate reason to complain about my 72V 9C setup with NiCd)

LI-ghtcycle said:
[
IMHO, this is a great way to go, even if I end up going with something in the neighborhood of 16 packs since I can get the BMS + A123 cells at less than $5 per cell (on a good ebay deal) and in the end, I might end up trying something like you mentioned, making larger packs to go with the BMS and build them to the desired shape to keep compact and light weight.

Now DeWalt lists each pack as weighing 2lbs, but the cells inside weigh only 8*70g=560g, or 1.2lbs, so dropping the plastic shell can mean a significant weigh savings. If you combine 16 packs that would be a 15kg battery if you keep the housings, but the cells inside total up to only 9kg. (My current 72V, 8Ah NiCd is 12kg and I think that is on the heavy side)
 
gilnet said:
As I started to dig up some ref for you I noticed that they already posted.

Thanks for looking. I've found the stickified thread ggoodrum started in 2007 on how to harvest and use the cells from DeWalt packs. I also found kfong's thread on how to make an connector/adapter to plug into the unmodified DeWalt pack. Most threads report during the design and building phase. Few regularly report on long term performance and reliablility. Before I get into the DeWalt/A123 building I was hoping to hear from more people who have been using these cells. There must be a fair bit of experience accumulated since the 2007 thread started, and many ES members started using A123 batts. Cyclomotorengineers report of 200 cycles w/o noticable performance loss is of course a good start. Anyone got more than that? With tyhe oriog DeWalt BMS?

gilnet said:
I also noticed you were mixing apples and oranges.Drbass never sold faulty dewalt pks.anywhere.period.

I don't get the "applies and oranges" thing?

My understanding is that drbass somehow gets customer return packs which are presumably defective in some way. Some have a defective BMS, a defective cell or two. I recall he usually states you can expect to harvest 8 good condition cells from the 10 cell 36V packs. I've not bought anything from him personally though, so I have no direct experience.
 
I've had them for over 2 seasons and have ridded over 2000 miles on my Cyclone build. I've been using the packs with my battery interface without any issues. The batteries are very consistent and I see no problem with them lasting many seasons more. I like the convenience of having them charged in under an hour using the Dewalt chargers. And having spares packs available when I need them.
 
I've also been using my Dewalt DC9360 packs at 1S4P setup doing 10 miles rides to work and another 10 miles back home since 2007. I have noticed when the batteries are not fully balanced I get about 1A less out of a total of 4 packs so I had to pedal about a couple of blocks to work or go back home. But this is a very realistic figure since 4 packs just barely make it 10 miles on the San Francisco hilly area with stop & go traffic. :)
 
BTW, I figured another way to save space while finding a good place to put and hold my batteries. See below:

dewaltbatteryholderrack.jpg
 
Been using my 4x 36v (33v) dewalt packs since mid-2006 with a by-pass on output and through the dewalt BMS while charging. This let me bypass the 15/35 amp limits but I don't get cell shut down. I watch my Cycle Analyst very carefully and test my packs every 8 months or so for capacity to update my total amp hours available. Check out my build I re-posted here:

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=15253&p=226587#p226587
 
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