Dewalt A123 28V Packs & Charger Questions

[LI-ghtcycle]

Ok, I have done a lot of searching and reading the last week or so, and I just want to run a few ideas by you folks. I think I understand about %75 of what I have read, so before I take the plunge, I just want to know I'm not about to break my neck in too shallow of intellectual water! :lol:

Question #1)

First off, I have been less than delighted with the Dewalt charger, it works, I guess ... if it HAS too ... Reminds me a lot of the "man's prayer" from Red Green.

I learned from my reading that it's generally accepted that 3.6V per cell of A123 batteries is a solid charge, and since the Dewalt charger isn't very consistant at balancing, short of opening up a pack of 8 (28v DC9280) cells and testing each one, would it be safe to say that if I have a total voltage of approximately 28.8+ on the pack (I can usually get each pack to show at least 29v, some as high as 29.7) by simply "re-charging" again after the first "charge" when all the LED's Stay solid.

It would seem that the charger goes Idle once all 3 lights are solid, so I don't think leaving it in the charger longer makes a bit of difference, UNTIL you take them out again, and put them in again for another 5 mins. or so. Using this method, I have been able to get most of the packs to hit about 27.6-27.9 on the initial charge, and then reach high 28's- low 29's on subsequent 5 min. "top-up charges". Almost all the batteries (I have 8) take 2 top-up charges, but some take 3-4 short top-up charges to reach this level.

Is it safe to say if I have 29v+ on an 8cell A123 pack that they are going to be at or really close to 3.6v?

Question #2)

I have confirmed with kfong that I can use the charging terminal (unused in the normal use of his Dewalt Interface PCB) to charge the batteries, he recommends I use a 15Amp In-line fuse to prevent high packs draining to low packs, and if I understand correctly, if I am using 16 cell groups, (two 8 cell DC9280 Dewalt packs in series) that I should charge at 59.2v and if I want this done in about 1 hr, I need to do so at 9-10 amps, would a "smart" SLA CC/CV charger for 59.2v (a nominal 48v charger) running at 10 Amps be acceptable to do this?

I know that the Dewalt BMS isn't the best, but I am hoping I can use it and maybe just throw the batteries on the Dewalt charger individually every so often to make sure they are reasonably balanced, say once a month?

Sorry if all these questions are elsewhere, but in all my reading, I only found fragments of the answers, and I just want to be sure before I do something that will damage my A123's.

Thanks!

 

[jag]

Some thoughts on your questions. Hoping others with long real term experience will chime in though.

Question 1: The batteries might have arrived with individual cells at different state of charge. A good BMS is meant to correct this. With luck the DeWalt charger and BMS will get the cells better balanced after some/several cycles.

Question 2: You can for sure charge through the fused "3rd" terminal, but to me it is unclear how the DeWalt BMS will react to this, if at all. Also you suggest a high amp charger. If the cells have trouble getting balanced even with the 2A from the DeWalt charger, it will likely be worse at 10A.

Now I would also like to find an inexpensive, good way to use the DeWalt cells+BMS as a package but with a minimal interface to the DeWalt charger (I want to use a connector and wire between charger and pack), or possibly an aftermarket charger. I haven't seen any sure solutions to that here. Worst case it might be too difficult ant the best solution is to buy a separate BMS.

 

[biohazardman]

Ok, I have done a lot of searching and reading the last week or so, and I just want to run a few ideas by you folks. I think I understand about %75 of what I have read, so before I take the plunge, I just want to know I'm not about to break my neck in too shallow of intellectual water! :lol:

Question #1)

First off, I have been less than delighted with the Dewalt charger, it works, I guess ... if it HAS too ... Reminds me a lot of the "man's prayer" from Red Green.

"I learned from my reading that it's generally accepted that 3.6V per cell of A123 batteries is a solid charge, and since the Dewalt charger isn't very consistant at balancing, short of opening up a pack of 8 (28v DC9280) cells and testing each one, would it be safe to say that if I have a total voltage of approximately 28.8+ on the pack (I can usually get each pack to show at least 29v, some as high as 29.7) by simply "re-charging" again after the first "charge" when all the LED's Stay solid.".


“It would seem that the charger goes Idle once all 3 lights are solid, so I don't think leaving it in the charger longer makes a bit of difference, UNTIL you take them out again, and put them in again for another 5 mins. or so. Using this method, I have been able to get most of the packs to hit about 27.6-27.9 on the initial charge, and then reach high 28's- low 29's on subsequent 5 min. "top-up charges". Almost all the batteries (I have 8) take 2 top-up charges, but some take 3-4 short top-up charges to reach this level.

Is it safe to say if I have 29v+ on an 8cell A123 pack that they are going to be at or really close to 3.6v? ”


Answer #1
The charger does no balancing at all. The BMS in the pack handles all of it and does only so-so job from what I have seen.
It would be nice to be able to trust the system enough to make that assumption I would not myself. You are measuring an average voltage. Some cells could be high and others low. So, I would say no it is not safe to assume such a thing.

Question #2)

I have confirmed with kfong that I can use the charging terminal (unused in the normal use of his Dewalt Interface PCB) to charge the batteries, he recommends I use a 15Amp In-line fuse to prevent high packs draining to low packs, and if I understand correctly, if I am using 16 cell groups, (two 8 cell DC9280 Dewalt packs in series) that I should charge at 59.2v and if I want this done in about 1 hr, I need to do so at 9-10 amps, would a "smart" SLA CC/CV charger for 59.2v (a nominal 48v charger) running at 10 Amps be acceptable to do this?


Aswer#2
A fuse will not prevent electricity from flowing in either direction but a diode will. Your packs should all be the same voltage so you should not need one.
Some chargers can be turned up 5 to 10% above their nominal voltage others are lucky to reach their specified voltage. I run a 2p14S for my 48V system, which has a full charge voltage of 52 volts. I use the 14s because 14 x 3.65 is just under the 54v maximum voltage range of my 48v charging system voltage
You stated the packs voltage but not it’s AH. The Dewalts are usually near 2.3AH if you have a parallel group the AH will double. Not doing the math and guessing on a 2p pack, I would think they should charge in near the hour you wish them to.
.

I know that the Dewalt BMS isn't the best, but I am hoping I can use it and maybe just throw the batteries on the Dewalt charger individually every so often to make sure they are reasonably balanced, say once a month?

Answer #2.5 ;^)
How often they need balanced will depend on their original balance state, how deeply you discharge them and the strength of the individual cells to start with. The deeper the pack is discharged the greater the chance of larger imbalances.

Sorry if all these questions are elsewhere, but in all my reading, I only found fragments of the answers, and I just want to be sure before I do something that will damage my A123's.

Thanks!

I read these

http://endless-sphere.com/forums/viewtopic.php?f=14&t=2498

http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416

and much more and then proceeded to mistreat my packs by overcharging them as I had not yet finished wiring my BMS. They are resilient batteries and I seem to have done very little if any harm with my overcharging them.

Good luck

 

[LI-ghtcycle]

I read these

http://endless-sphere.com/forums/viewtopic.php?f=14&t=2498

http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416

and much more and then proceeded to mistreat my packs by overcharging them as I had not yet finished wiring my BMS. They are resilient batteries and I seem to have done very little if any harm with my overcharging them.

Good luck

Thanks for the info, Bio, can you be a little more specific? What voltage and amperage did you charge at and was this with 10S?

I read through those posts too, but I could spend a month reading them and still not understand it all. :wink:

I'm really curious to know exactly what voltage the Dewalt charger uses since it will charge both 28 and 36V Dewalt batteries, so I'm thinking it's actually charging at the minimal rate for the 36V (my father's 36V batteries are rarely charged to over 35-36V, but he's not kept track, and maybe that is just a product of his not checking them after the charge and just using them as is) and if I charge my 28's for even just a few minutes again after it has already had 3 solid lights once before, it brings them up to an average of 28.9V from an average of 27.4V from the initial charge.

If I had a timer that could sense when the third light would become solid, and then went into a cycle of 5 mins on, 1 min off, 5 min on for about 2 cycles, that would just about guarantee that all my 28's would be in the high 28 to low 29 range.

 

[LI-ghtcycle]

Well, I just heard back from Mr. Ping, and he will make me a 9A CC/CV charger at 59.2V For a grand total of $150 ($105 + $45 shipping).

Correct me if I'm wrong, but if I decide later to use a balancing PCB later on, this charger can still be used as the power source.

Can hardly wait till the 1st when I get my disability!

Now if I can just get the LBS owner to let me help him more selling his electric bikes! He's not very computer friendly

Gotta get him on the computer more often .. found some great deals on good bikes for sale at the local Goodwill ... they have no idea what they are giving away sometimes! (shhhh don't tell them hehe)

 

[biohazardman]

I read these

http://endless-sphere.com/forums/viewtopic.php?f=14&t=2498

http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416

and much more and then proceeded to mistreat my packs by overcharging them as I had not yet finished wiring my BMS. They are resilient batteries and I seem to have done very little if any harm with my overcharging them.

Good luck

Thanks for the info, Bio, can you be a little more specific? What voltage and amperage did you charge at and was this with 10S?
.

I am running a 48V system but 2P14S packs instead of the normal 16S as my 48V power supply/charger will only go to 54V so charge at 52V and 6+A. The battery packs were broken down to bare cells although I left them tabbed together. Used three 36V packs and split a 28V pack for the 48V 2p14s total. I bought three but built only one of the early TPpacks BMS units and use it exclusively for charging and ballancing. Yes you can use the Ping charger later and charge through a BMS. Much bettter than trying to use the stock Dewalt chargers and BMS stuff although there are a few around that have done so.

 

[LI-ghtcycle]

Kewl, on another note, I have to say I love what you have done with the Trance, Bio, I can hardly see a wire on that thing! Did you sneak the wires through some of the same places the cables go through the frame? Very clean, and I like what you have done with your battery, I'm hoping to access the Dewalt BMS while charging too, but I have a sneaking suspicion that the BMS has a lot more to do with the discharging than the charging with the Dewalts.

 

[biohazardman]

Giant must have known we were going to convert these to electric, as there are holes in the right places at the rear of the triangles that come out near the front of them. A picture is worth a thousand words. I took a five-mile ride down to the river to have a nice backdrop for the pics. Pulled out the camera and turned it on only to see an error message I had left my XD card at home. So ABS and CF for the background. You can see the wires come up just at the bottom of the fender. They go up the back of the seat tube to the controller. From the controller wires run up and into the rear bag and are wrapped in a sheath but plain to see for the short run. When I upgrade the batts I will take care of that also. The cable operated throttle removes a few visible wires also. The light wires are temporary but show at the moment. Think I will run a couple small wires through a brake cable for that soon. The reed switch brake wires come out in the top tube you can just see them, in the bottom pic, tied to the brake cable for about an inch.

holes in back of triangle above axle nut right

wires through holes in triangle left

motor wiring L rear

The Dewalt BMS does all the balancing for the pack and limits the output to keep it safe. They are the weak spot and the main reason for failure in the packs.

 

[LI-ghtcycle]

Nice work Bio! 8)

What year is your trance, and any idea how many years use that style of frame with the wire hiding tunnels?

Looks like I might have to wait on the Ping charger till next month after all, unless I am able to sell a bike or something, looks like my money is going to be about $93 tighter this month, maybe I will just get the whole dash with the Digital MX Speedo this month, and the charger next.

Yeah, I know the Dewalt BMS isn't the best, but it's all I can afford atm, too bad I can't just use my father's "smart" 36V SLA charger and charge the 28's in parallel, it's a low amp charger too, so it would probably take all night anyway lol! :wink:

 

[biohazardman]

Bought it last year but think it is a 2007? 2009 units did not have the shock through the frame. Checked wiht the Giant website and looks liekhte frame is the sam from 2005-2007. Good chance that the holes are there in those. Saved up, looked for a year to find/get most of what I wanted. Motor could use a bit more torque, I got the speed model, I can pedal to 30 and the motor matches that and was built to give me it's best economy there also. Makes a great commuter. I did not drive my car for over a month and have only put about ten miles on it in the last week or so.
Use what you have for now. Take your time at getting the rest together and do it the way that you want. Hard to be patient but good things happen when you are.

 

[LI-ghtcycle]

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Hmmm this is interesting, a plug for a diesel manufacturing company in Chinese? :lol: :lol: :lol:

I'm wondering what purpose our friend here thinks they are serving by posting spam in a language that the vast majority of users on this board don't even understand. :wink:

 

[LI-ghtcycle]

Bought it last year but think it is a 2007? 2009 units did not have the shock through the frame. Checked wiht the Giant website and looks liekhte frame is the sam from 2005-2007. Good chance that the holes are there in those. Saved up, looked for a year to find/get most of what I wanted. Motor could use a bit more torque, I got the speed model, I can pedal to 30 and the motor matches that and was built to give me it's best economy there also. Makes a great commuter. I did not drive my car for over a month and have only put about ten miles on it in the last week or so.
Use what you have for now. Take your time at getting the rest together and do it the way that you want. Hard to be patient but good things happen when you are.

Very good advice, and like most good advice, hard to follow. :wink:

I agree, better to save up and wait, I'm also buying and selling bikes atm, been pretty successful thus far, but deals are few and far between.