A123 Build

[magudaman]

Well this was an old post from the voltage forums but I can't find crap over there so thought I would post how I hooked up to my A123 batteries. They are still working great today with around 2.0 ah of capacity and they were purchased in 2006. Stored at 100% all the time and in the summer they sit in my hot garage when it is well over 80F.

I finally did it: I spent 200 dollars and got 2 Dewalt 36 volt batteries and a charger. I received my package on Friday and have started to make the packs work for my application. I am hoping to eventually buy two more Dewalt batteries to have total of around 8.5 ah of capacity at 33 volts. The packs weighs 2.5 pounds according to a postal scale so my 8.5 ah pack is going to be 10 lbs and will definitely out range my current 21 lbs 10 ah lead acid pack. If you were to pull out the BMS and case with all the balancing probes you probably could shed off a half pound maybe more.

I decided to go ahead and use the stock charger so that I can get the benefit of cell balancing hopefully keep the life of the batteries nice and long. Plus it a pretty fast charger bringing a battery to full in 1 hour (as tested). When I buy the two more batteries I going to get a second charger so I can refill my whole pack in 2 hours. The picture below is the charger and then :

So I am going to parallel all my packs so I had to by pass the BMS for my output to my scooter. All I did was solder directly to the two output tabs of the cells and left the BMS in. You can see below my okay solder job, but it doesn't warm up at all even at 15 amps.

The wire is 12 gauge Dean's "wet noodle" and then I put a 45 amp Powerpole connector on the end. I soldered the Powerpole on too:

So now I had the pack ready for high current so I did some testing. First I ran the pack though on my CBA. Below is the chart with a discharge rate of 3.5 amps down to 28.5 volts. It pretty amazingly flat right up the end around 2.1 ah. This was the first cycle and I'm not sure if it will improve over time. In addition I grabbed the pack almost immediately after it said it was done and I'm not sure if it continues to float in that other 200 ma. UPDATE: I just ran another cycle after it sat on the charger for a while and it put out another 120 mah. I’ll do another test in a month or so and post those up.

In addition to the CBA I also test the battery at higher currents with my Watts up. After removing 1.4 ah from the pack I exposed it to a 13 amp load and it still wasn’t dropping below 31 volts. For my purpose I need it to be above 30 volts to be usable since my controller shuts down at 30.4 volts. I have not exposed my pack to more than 15 amps but it seem to hold it voltage very well. During my test I was sucking almost 500 watts out of the pack but it should be able to handle more since Dewalt claims the drill can out put 750 watts peak. Finished pack photo:

UPDATE: well as you might have seen it has took me a while to get this posted to the forums and I couldn’t resist to try the scooter today. I don’t have my parallel setup wired so I did just a single pack. The results were as expected for a single pack. With a 30.4 amp load a fresh pack drooped down to 29.21 volt. This is a normal drop according to the cell spec sheets for 30 amps. But I was able to ride around and try it out at full speed. I notice the top speed loss but I’ll live with it, and it should only get faster as I add more paralleled packs. My scoot did shut down from low voltage. With 20 pounds removed from the scooter it was easy to get out of my garage. I keep you up to date when I get the paralleled stuff set up.



ADDITION SINCE ORIGINAL POST:

This is my completed pack inside the scooter. All four are paralleled together using powerpoles connectors and 12 gauge wire. They all run through my watt's up (which is way overloaded) then into the controller.

My more current pack:

My newest set up uses my 4 Dewalt packs in 2 series 2 parallel. My cost with 2 charger and 4 packs is around $420 off ebay purchasing the DC900Kl and selling the drill and case. I have a usable 4 ah at 66 v. Weight 11 lbs.

These packs have also been used in an all parallel set up in which I had 33v 8 ah usable and would see peak currents of around 150 amps.

These pack are amazing. They rarely heat up at all and can provide more current that any lead acid I have ever used. In addition I have abused these packs for 10 months with lots of cycles (drained once a day guess average). The pack under test condition have lost no capacity according my CBA. I would recommend these pack to anyone and do believe they will save you money in the long run due to long life.

 

[Lyen]

I really like your setup. It is very easy to attach & detach the batteries for recharge. You have also saved more weight by no using the flashlight holders like I do. I wish there is a way to save more weight by not using the flashlight holders & without any battery modification. Please show us your ebike naked so we can learn more from you. Thanks!

 

[kfong]

Nice setup maguaman. What are you using as a low voltage cutoff? As you see from your graph once you run close to the end of charge. The voltage drops significantly, this can easily reverse charge one of your cells if you continue to push it. My friend lost two batteries this way; even though I tried to convince him he needed some sort of voltage monitor on his scooter or a voltage cutoff device.

Lyen, just use my interface board, on my scooter project http://www.endless-sphere.com/forums/viewtopic.php?f=12&t=12031&start=15 I just have it connected without a carrier. This will give you 20amps per battery and bms protection as well without any mods to the pack. As long as the packs are secure and not moving to much, you could do the same as what maguaman did with my boards and you won't be voiding any warranty.

 

[magudaman]

What are you using as a low voltage cutoff?

Just a cycle Analyst, but I use it like a fuel gauge. When I am running 2s2p I can get around 4.2ah total. While I ride I glace down see where I am at and usually turn back when I'm at around 2.0ah used. It has worked great so far! I also make sure my total pack voltage doesn't drop below 58v min.

My pack from what I can tell have remained very balanced. Each time I charge I leave each pack on for at least 20 minutes after all the lights are solid.

 

[kfong]

Be careful not to go past that, I did what you did at first using just a wattmeter and thought I could just monitor the voltage. The problem is you really can't allow it to get close to the knee, since the voltage drops off like a brick. I lost my first pack this way and decided I wanted a safer approach. Now I just ride till it cuts off, maximizing my distance.

Yeah, I'm quite happy with the Dewalt chargers. They work very well and the packs have gone through many cycles and over 2000 miles. I get very consistent charges and it’s usually under an hour. I have four chargers and my bike is setup for 3 packs at a time. This is very convenient. A quick charge and I’m off to the corner store if needed.

 

[PeteCress]

My newest set up uses my 4 Dewalt packs in 2 series 2 parallel. My cost with 2 charger and 4 packs is around $420 off ebay purchasing the DC900Kl and selling the drill and case.

I just paid $115 each for two packs.

Oops!....

How much did you get when selling the bare drill/case?

 

[PeteCress]

Nice setup maguaman. What are you using as a low voltage cutoff? As you see from your graph once you run close to the end of charge. The voltage drops significantly, this can easily reverse charge one of your cells if you continue to push it. My friend lost two batteries this way; even though I tried to convince him he needed some sort of voltage monitor on his scooter or a voltage cutoff device.

Lyen, just use my interface board, on my scooter project http://www.endless-sphere.com/forums/viewtopic.php?f=12&t=12031&start=15

What is MaguaMan giving up by not using the interface boards on his application? The protection against reverse-charge?

 

[magudaman]

I got maybe $100 for the drill and case, or a least that what it looks like it would go for now anyways.

With my setup I gave up the low voltage cut off. So if I don't watch my total pack voltage carefully while I ride or how many Ah I pulled out of my pack then I risk over discharging my pack and killing cells. I did have one problem early on in my setup where I didn't plug in the parallel pack and I saw the lower voltage but it didn't click. I ended up discharging the batteries too far on one pack and required a charge from a power supply since the dewalt charger wouldn't take it. The pack is still in use and shows now signs of damage but I think I got lucky.

 

[MitchJi]

Hi,

What is MaguaMan giving up by not using the interface boards on his application? The protection against reverse-charge?

I think he also gives up the warranty.

 

[scoot]

Since this thread was resurrected, I have some renewed interest in these. I have been researching what i could find out the charger and these batteries but have had no luck... even the dewault site, but no manuals available. Specifically, I have found some 28v packs for $40 and the charger for $18. happy to provide links if anyone is interested. I want to use these packs with as little modification as possible since I suck at the skills required to bust them appart and re-assemble them like many out here have. I may even try to use that charger for my Headway pack... just dunno yet. :|

But I have a few nagging questions for anyone with some experience with these:

Is the charger a "balancing charger" with contacts for each cell in the pack? Is that how the balancing occurs? Pics of the connection points on the battery and the charger would be most helpful.

What does the BMS inside the battery pack actually accomplish? (Perhaps just LV cuttoff?)

Is the HV cuttoff integral to the charger or the pack?

Basically I am confused about where all of the "BMS" functions occur and how they are integrated. Any guidance you guys could offer would be most appreciated.

 

[PeteCress]

Specifically, I have found some 28v packs for $40 and the charger for $18. happy to provide links if anyone is interested. I want to use these packs with as little modification as possible since I suck at the skills required to bust them appart and re-assemble them like many out here have.

Hopefully somebody who actually knows something (as opposed to Yours Truly) will chime in.

Having said that, the 28v packs were calling out to me too - but somebody talked me out of using them natively bco the apparent speed limitation inherent in 28v.

What puzzled me was that the packs AH rating (2.3) was the same as the 36v packs'.... yet the price was less than half.

 

[scoot]

OK, I waded through propbably 50 posts or more from numerous threads discussing the DC9000 charger & dewault packs. I found out what the charger connections and wiring look like, but the number of wires does not seem to add up for 8s or 10s charging... I'm so confused.

I still cannot not tell if this charger would function as a "balancing charger" on its own for any 8s LiFePO4 pack, or what the the BMS in Dewault packs actually does other than pack and cell by cell LV cuttoff. I sure wish someone knowlegeable could help me out.

I did at some point infer that this charger may not function at all without the handshake from the actual Dewault pack w/BMS, but am not sure i completely understood what i was reading. Anybody know for sure about that?

My biggest hope was that I could swap the insides of a DC9000 charger with the SLA CC/CV charger board that I have inside my E scooter and obtain some balancing & HV control on my 8s headway pack. I already have LV (cell by cell even) covered by using a CellLog8 in conjunction with my controller. thanx ahead of time to any one who can help.

 

[evblazer]

Having said that, the 28v packs were calling out to me too - but somebody talked me out of using them natively bco the apparent speed limitation inherent in 28v.

What puzzled me was that the packs AH rating (2.3) was the same as the 36v packs'.... yet the price was less than half.

28 vs 36 I'm sure is a speed difference but I'm wondering if for some people that would be ok for some applications. Mine persoanlly would just be for help up some hills where speed isnt' the issue but a few packs in parralel might give me the amps.
The price difference I'm guessing is because the 36volt battery is the high end flagship product and they can charge more for it. It might be different but I think is just a making money thing.
I'd really like to go with the 28 volt packs myself if they can be used as is with a few in parallel. I know there is the adapter board out there but that doubles the price of each pack but if you want to push it might be worth it to add on later.