a123 developer packs

Oops! I mis-spoke - I'll send twenty 5-pin connectors + 200 crimping pins for $10 plus shipping. The minimum pin purchase was double the number of pins needed, and I'm happy :) to pass on the extra pins for crimping practice...

Brian, nice job on these connections.
I just got 2 dewalt 36's and am getting 6 more for a 72 volt (+ -) system for my home built ebike with crystalyte 407 front motor and 72 volt controller. I'm planning on using the batteries in 2 parallel sets of 4, connectedconnected in series, with 2 dewalt chargers and I'd like to keep the batteries intact and use the existing connectors. I'll have to make the 14 contact connector for charging unless I can find some that I can buy.
Have you any idea where I can find those? I looked all over the net without any luck.
Does the bms cutoff power from the batteries automatically at low voltage or is it something in the power tool that stops it? is that protection still there in a bike application, is what I wonder.
Thanks for al the great information you've been sharing, I've learned an incredible amount reading your posts and some of the others.

Wattsup

Hi Wattsup,

The only discussion I've found which shows where to get these connectors is in the following thread where they mention you can get them from Dewalt and what the part numbers are. This thread also answers your question about the overdischarge prevention built into the electronic module, and other features built into the electronic module. They seem to know what they are talking about:

http://www.rcgroups.com/forums/showthread.php?t=587041&highlight=a123+dewalt+circuit+fuse

Unfortunately, the 14 pin connector parts you want may be pretty expensive to buy from Dewalt. If you only need two of them, you could also get them by buying the 36V Dewalt Flood lights on Ebay and removing them from the light. You might get a good deal on these, and possibly get a spare light as well.

Their analysis indicates that the overdischarge protection is built into each pack. They also indicate a max 15A output from each pack.

I hope that helps.

Best Regards,

Brian

H Brian, thanks for this info, it does help me to understand

[[Their analysis indicates that the overdischarge protection is built into each pack]]
In your set up, do you not risk overdischarge on the packs from which you removed the bms? how do you prevent this from occurring?

[[They also indicate a max 15A output from each pack.]]
I guess this is why you bypass the dewalt connectors and put in heavier wires to connec the batteries together?

I don't know enough about this yet to know how many amps I'll be drawing per battery.
Does the amperage that gets used get divided up among the 8 batteries equally?
So many questions... Thanks for your time,
wattsup

{[[Their analysis indicates that the overdischarge protection is built into each pack]]
In your set up, do you not risk overdischarge on the packs from which you removed the bms? how do you prevent this from occurring?}

I will avoid overdischarge in two ways: The main motor controller for the Aerorider will be cutting out at around 27 volts. I will also be using a Watts Up Meter to monitor the pack myself.

{[[They also indicate a max 15A output from each pack.]]
I guess this is why you bypass the dewalt connectors and put in heavier wires to connect the batteries together?}

Yes - also to allow the regenerative braking to feed current back into the batteries without running the risk of harming the electronic module. If needbe, I will disconnect the electronic module during operation, and reconnect it during charging. (I have also considered using the high power output of the electronic module itself to trigger some custom circuit to run a FET to disconnect the battery if it gets to low or too hot during operation.)

{I don't know enough about this yet to know how many amps I'll be drawing per battery.
Does the amperage that gets used get divided up among the 8 batteries equally?}

I believe "Yes" to a great degree, but I have not tested this: There may be some minor differences in battery currents because of internal battery resistance variation and wire length differences to the batteries.

One might think that if the packs are sending out slightly different currents, that one pack might discharge way before the others, however I believe they will also be balancing charges against each other as they go along (This balancing can be enhanced to individual cell balancing by tying all the bms connectors together in parallel during use as recommended by A123, which is what I do.)

Wattsup and Whoever is interested:

Here is another Dewalt A123 reverse engineering discussion over at the Tidalforce Forum talking about what the Dewalt 36V electronic module does. Especially note the discussions starting March 7 with an X-Ray of the module:

http://tinyurl.com/24nf6a

Brian

Hi Brian,
Your 5 pin connectors work great. They fit exactly on the Male connector of the Dewalt pack.
While removing the power wires on the pack, I accidentally shorted it and there was a bright spark and a pretty loud zapping sound. I checked the voltage of each cells, all of them have 3.6v except 2 cells which are 3.3v. These 2 cells are where the terminals are attached to. I have not recharge them yet after the short. After 48 hours, I checked the voltage of the cells and they haven't change.
You think I may have damage the 2 cells?

thank you,

Jojo

Hi Jojo,

I have accidently shorted batteries temporarily and generated sparks several times, with no noticeable bad effects to the batteries. I would guess that your battery is fine. Perhaps their life has been reduced a little.

Overnight charging and balancing with the Dewalt charger should get the battery voltages equalized better.

Brian

I am curious as to where you found the case for your battery pack. i am looking for one too.

Boodydarn

Hi Boodydarn,

For my 5 Dewalt-pack system, I just planning on tying it all together with aluminum bars and polypropylene tape to seal up the seams between packs, and with some kind of handle tied to the aluminum bars to carry it. Since I will be using it in my Aerorider which is weather-proof and has some nice big slots next to the seat for batteries, a case is not absolutely necessary.

However I am looking for some kind of perfect sized pack to stow it in when carrying it into the building where I work. I have an old bike rack pack stored away somewhere made for a standard bike rack that might be long enough. I'll let you know here if I find a good one.

Thanks,

Brian

Hi Brian,

Do you have any more connector packs available? I'd like to buy some from you if you do. Please e-mail me (ericcATxenopiDOTcom) since I don't check this forum too regularly.

Eric

Hi Eric,

I still have plenty left. I will send you an email.

If anyone else wants some, probably the best way to contact me, without tying up this forum with commerce, is to send me a private message and your email address using the "Send private message" command located at the bottom right hand corner of this forum page.

Best Regards,

Brian

Hello Brian,
Are there better chargers than the Dewalt that can charge multiple Dewalt packs in one shot? I am presently running 8 packs using 2 charges and when bike is complete, it will be a total of 16 or 18 Dewalt packs.
And it can still use BMS like the ones in the Dewalt chargers.

Best Regards,

Jojo

Hi Jojo,

Glad to hear that things are moving along with your pack system. Are you able to crimp pins and make your own parallel bms connections for your Dewalt packs using those 5 pin connectors I sold you?

There are other charging systems that are used by the RC groups that can charge what they call a 10S pack (for 10 cells in series) of A123 batteries and also balance them. See the RC forums.

They are very expensive compared to the Dewalt chargers, especially the ones that also have the balancing features. I recall them being around $150 to $200.

One reasonable approach would be to have a fast charger that does not balance for those times when you want a quick charge, then to also slow charge and balance using Dewalt chargers.

Someone in one of the forums said that you could sometimes buy a large adjustable 48V high current (20A plus) power supply on eBay that is used for old computer systems for prices starting around $40. One of these might do the trick if used right. When I get a chance, I will see if I can find the link.

Best Regards,

Brian

:) Brian,

I'm new to this forum and am building an a123 battery pack for my ebike. This form page does not have a place for PMs. How can I reach you to purchase some Dewalt battery connectors?

Thanks

Wesley

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Hi Brian,
Your connectors are awesome. I managed to crimp and connect the wires for the connectors/batteries and they are charging good. I still haven't parallel the bms yet. While checking the RC forum, it looks like using a big power supply is the way to go to charge large packs. When completed, I'll be using 2 groups of packs that consist of 8 dewalts connected in parallel and then in series, giving a total of 66v 18.4 Ah. Have to find which of these Power supplies is suitable for the task...
Sorry for the delay in my response, I was not able to check this forum for a week because my internet is down.

Best Regards,

Jojo

Hi Jojo,

I'm glad the parallel connectors are working out for you. I'd like to see a picture of your pack system when it is all assembled. Take care to avoid mis-connections to avoid sparks!

Best Regards,

Brian

Hello all, will I use a SPDT or DPDT switch for charging A123 batteries at 36v. Tbey are wired as 4 parallel and 1 series packs... thank you, Jojo

Has any one used the actual A123 Developer packs purchased from A123?

How do I get some of those connectors for the DeWalt batteries?

Hi, I have read this thread and want to end up doing the 5 packs charged with one charger. Currently (sorry for pun) I am having problems. I have three packs and one charger. After testing on the motorcycle (Etek with Alltrax set back on amps) I have placed two packs in parallel and rode it. It was good and the end pack voltage was around 27 volts. I put the packs in the charger and got the bad battery indication. After many millions of trying things, I finally measured all the cells and found one bad cell per pack! I then used a good cell from another pack and put it in the charger and it still says bad indication though I have measured 3.4 volts on all cells! I am beginning to wonder if I have a bad charger? By the way, I have wired the two thick output wires, tapping them before the power controller module. I am getting worried that I am wastingh lots of time and money so please give me some suggestions. Thanks,
Jeff

Hi Jeff,

Sorry to hear about your trouble with the Dewalt Packs, and possibly your charger.

I have a lot of questions for you to help see if we can get to the bottom of this...

The fact that the two packs that were discharged to 27 volts did not charge when each had a bad cell is not that surprising since the charger probably checks each cell voltage before beginning.

Any clues as to whether the pack came to you with the bad cells? I have read about packs coming with bad cells from ebay purchases on the R/C Airplane Battery forum.

Did you successfully use the Dewalt charger before your ride? Were the packs at 36V or greater when you started?

You say that one cell in each pack is dead. What is the voltage reading from your bad cell? Is it the same cell in each pack?

People in the R/C airplane forum have described a way to fix an individual cell that has been overdischarged by tying it to a charged cell through a high power resistor until it gets to a voltage that the charger can handle - I am not sure what voltage this would be for the Dewalt - perhaps just a volt or so - perhaps higher. This might then allow it to be charged correctly with your charger.

What is really strange is that this third pack does not want to charge either.

Have you measured the battery voltage on the third pack? Is it above 32 volts?

Were these new or used packs when you got them?

Can you describe how you have been running these two packs in parallel?
Are you just tying the main positive and negative power lines together?

Anyone else have any ideas/things to try?

Best Regards,

Brian

Thanks for helping Brian, I will attempt to answer your questions to get to the bottom of all this mess I am in...
1. is there some voltage level that the Dewalt charger cannot deal with? In other words what is the lowest I can discharge a pack to? I understand about the mismatched cell values being checked from the pack. 2. I got all the packs from different e-bay sellers-all as-new. They all accepted charge to third lite as I expected. Packs were around 36 when charged. 3. The dead cells are 0 volts and I tried the idea of charging them from another cell (in this case an 8AH 2v cell). But they act like dead short--well maybe not full short but they do drain the other cell trying to charge it. They also get warm during this. The pack will power things with dead cell in. I don't know if the resistor method can save these. 4. I repaired a pack and checked all voltages at each cell (3.4 volts) then put it in charger. Got first lite then BAD BATTERY indication flashing. This is killing me! Maybe it is a bad charger. I have another one coming soon so I can check that. The pack was not hot either during this charge attempt. 5. I am running them in parallel by connecting the + and minus from beneath the Dewalt BMS device. Also, I ran a small motor from the top connections of the BMS and it worked fine.
6. General questions and assumptions. When I rode the bike the first time I went pretty low voltage-perhaps one cell was way lower and bottomed out. Is this a death-of-cell method? Charging: I read the A123 charging infos and it looks like you could "trickle" charge these by using a solid, regulated 3.6 volt source, correct? How do you know when fully charged and then you can float voltage at 3.45? Or does the 3.6 not matter if it stays on (like a multi-pack, meaning bike's parallel pack would) since the pack is no longer drawing current? I can live with the 5 hour charge of 5 packs as described earlier in thread but wonder if the paralleled cells (on BMS wires) will charge okay individually? Thanks for replies here or my e-mail- jeffreyk@charterDOTnet.

I purchased one DeWalt pack on EBay and three from ToolKing.com.

The eBay pack has performed flawlessly. I discharge it with halogen lightbulbs that draw 4.5 A at 36 V, producing a chart with an EagleTree micropower logger. It yields 2200 mAh before I stop the test when it reaches 30 V under load. I have broken it up into cells and put them back together in various configurations. Currently it is a 4S2P pack which I charge on an Hyperion EOS 5i dp charger with an LBA10 balancer. This system displays the voltage of each cell throughout the charge process. At the end of the charge, the time needed to charge and the mAh put into the pack are displayed, and I can also see the voltage of each cell. This gives me an assurance that the battery pack is well balanced and has a full charge, such that I can rely upon it to provide at least 4 Ah as the voltage under a 5-10 A load drops from 33 to 30 V.

The three packs from ToolKing were in sealed plastic packaging and came with a Dewalt charger. Two had one cell which dropped the pack voltage below 29 V at around 1000 mAh, the third had two cells which were yielding much less than the rated capacity of 2300 mAh. A post on an RC forum stated that, rather surprisingly, the DeWalt BMS can unbalance the packs if they are left to sit on the shelf for several months or more.

The Dewalt charger is very crude compared to the Hyperion (or several other similar brands). One pack was left on the Dewalt charger for 11 hours and was still seriously out of balance and produced less than 2/3 of the normal capacity when tested. It does not show any indication that balancing is in progress. Balance charging of a single cell can take a long time on the Hyperion, even 5-10 hours if it is seriously low. The Dewalt charger would probably take at least that long. Balancing several parallel packs could take a very long time.

Two of the ToolKing packs displayed the "bad battery" indication on the Dewalt charger after being discharged to 29 V under load. I charged them from a 36 V battery until they were around 32 V resting and then the Dewalt charger accepted them. This may not always work to solve "bad battery" conditions, however, as other things could be wrong as was mentioned above.

My questions for the forum are-

How many mAh are you getting from your packs which have been charged with the Dewalt charger?

What is the low resting voltage limit for the Dewalt charger? I believe it to be around 31 V, but that is conjecture with only a little experience to back it up. The Hyperion has a limit of 3.0 V per A123 cell, but it will trickle charge them for 5 minutes at a time to bring them up to that limit and then go into full speed charge mode. I prefer this as it gives me more flexibility.

How closely balanced are the cells after 8 hours on the Dewalt charger? I think it is probably suited to maintain balance in packs that are already fairly closely balanced, but may not be effective at restoring balance if cells differ by more than .1 volt, as they did in all three of my packs from ToolKing. Perhaps if I had put them on the Dewalt charger for 3-4 days they would have been alright.

What voltage do the packs have fresh off the charger?

I have sent my pack and charger in to a Dewalt service center. Perhaps they will replace them with fresher, new stock. It is much simpler to work with a new and closely balanced pack. It appeared that the batteries in the ToolKing pack I openned were made in Feb of 06, so they may have had more than a year on the shelf. This may be why ToolKing sells them at a discount.

I may also buy the Hyperion 1210i charger in the future as well as a second LBA10 balancer in order to charge a 10S3P pack which I will build next.

The A123 batteries have many positive attributes, but I am not certain that using the $50 Dewalt charger (eBay price) is appropriate for charging and maintaining a $300-500 battery pack. Especially if you rely on it to get you around on your ebike and don't want to spend extra time manually checking on your battery pack.

Hi Jeff:

I'll do my best to answer your questions:
1. is there some voltage level that the Dewalt charger cannot deal with? In other words what is the lowest I can discharge a pack to? I understand about the mismatched cell values being checked from the pack.

I don't know what the minimum voltage it will handle. My drill has discharged the pack to about 28 volts and then recharged just fine from there

2. I got all the packs from different e-bay sellers-all as-new. They all accepted charge to third lite as I expected. Packs were around 36 when charged.

This is good. Did you let the charger balance the packs overnight before using them? The reason I ask is that the quick charge can leave them unbalanced, and may have accounted for why you fell too low on one cell during use.

3. The dead cells are 0 volts and I tried the idea of charging them from another cell (in this case an 8AH 2v cell). But they act like dead short--well maybe not full short but they do drain the other cell trying to charge it. They also get warm during this. The pack will power things with dead cell in. I don't know if the resistor method can save these.

Did you attempt this cell recharge with the battery control module attached to the cells? It is possible that this shouldn't be done with the circuitry hooked up.

4. I repaired a pack and checked all voltages at each cell (3.4 volts) then put it in charger. Got first lite then BAD BATTERY indication flashing. This is killing me! Maybe it is a bad charger. I have another one coming soon so I can check that. The pack was not hot either during this charge attempt.

How did you repair the pack? Did you disassemble it and replace the bad cell? If so, is there any chance that you harmed the battery control module by having the balancing plugs connected without the main power lines hooked up?

5. I am running them in parallel by connecting the + and minus from beneath the Dewalt BMS device. Also, I ran a small motor from the top connections of the BMS and it worked fine.

My understanding is that this is OK as long as the batteries are clearly balanced well before doing this, and when the batteries are still good. In my approach I have the balancing ports all tied together during discharge. I think this makes it less likely that a given weak cell will overdischarge since the other 4 parallel cells help protect it.

6. General questions and assumptions. When I rode the bike the first time I went pretty low voltage-perhaps one cell was way lower and bottomed out. Is this a death-of-cell method?

I believe so... this is how a cell can get overdischarged to the point that the charger can't deal with it. A battery controller would check all the cells during discharge and make sure they don't overdischarge. This is the risk you take when running open loop like this. I believe careful balancing before discharge may help avoid this. A quick constant current charge of all the cells in series might not properly charge any individual cell, and my understanding is that balancing takes care of this.

Charging: I read the A123 charging infos and it looks like you could "trickle" charge these by using a solid, regulated 3.6 volt source, correct?

Yes.

How do you know when fully charged and then you can float voltage at 3.45?

It should be charged when it stops drawing current through the charging resistor.

Or does the 3.6 not matter if it stays on (like a multi-pack, meaning bike's parallel pack would) since the pack is no longer drawing current?

Shouldn't matter - just like you said.

I can live with the 5 hour charge of 5 packs as described earlier in thread but wonder if the paralleled cells (on BMS wires) will charge okay individually?

My experience with my 5 pack is that it charges nicely in 5 hours using the Dewalt charger. I am still not sure how long it takes to balance the whole 5 pack. I believe they get less out of balance in the first place since the individual cells in parallel through the balancing ports may balance each other out. I am hoping that does the trick and that even 8 hours of balancing will still work on 5 cells in parallel. I won't really know until I can do day to day testing when my Aerorider arrives

I hope that helps.

Best Regards,

Brian

Brian, Thanks for those thoughts. I agree with them all. At the time of getting the packs, I was unaware of the importance of the overnite charge. Live and learn. Yes, I repaired it by replacing the cell, most likely with the BMS in circuit. I also did the attempt at charging the single cell with it on so perhaps killed the BMS. I now see/understand the module is always trying to do something. I thought it only controlled the output to the drill and balanced during charging. In any case, in your 5-system method, I will only need one good BMS and will now be more careful with them. I am gaining confidence with the cells. I also agree with the person that responded to the thread with the idea to use a more robust charger/management system. I have decided I really do not like the Dewalt pack case so I am trying a tubular design that so far looks really promising. I will post info on it later this month.
Regards,
Jeff

Custom pack for Ebike.
Using existing Dewalt endcaps plus kapton tape, Powerpole 45 amp contacts, Powerpole connectors, Molex connectors, 12 awg power wires, multi-colored balancer wires, and the very useful 5pin connectors of Brian.

Can someone share a wiring diagram for a DPDT switch that disconnects 2 groups of 4 Dewalts connected in series and using 2 chargers to charge the packs in parallel. thank you... Jojo

I think this will do the trick:

Note that you won't want the chargers hooked up while in 72 volt mode because you could be charging one of the 36V battery packs while running your motor.

There are probably many other ways that this could be done.

I've actually never done this in practice, so I'd appreciate if someone else could check this out...

Brian

Here is the way I wired a friends bike for 72-volts using 2 36-volt chargers.

When the switch is in the charge position no current can flow to the controller so it also acts as an off/on switch for the bike.

Chas S.
My Bicycle Pages