I'm new to the forum and have been doing a lot of reading on A123 batteries. I have purchased 40 of the batteries, whether in Dewalt battery packs or developer kits. My question comes down to the best configuration for my e-bike that I purchased earlier this year. I have the 36v, 600 watt hub motor from we r electrified (bd36kit brushed). It came with 3 - 12 volt, 12 amp/hr batteries and a 20 amp controller. It also came with a 36V 2 amp Soneil smart charger. I way that I figure it, each Dewalt pack is 36v, 2.3 Ah. Therefore I would need 4 packs connected in a parallel configuration. Is there a better way? I'm kind of getting lost in my thoughts and have decided it's better to ask the experts than struggle and get confused.
Dewalt configuration help
- Thread starter auddog007
- Start date
catalystTGJ
1 mW
You'll want to go parallel, if you do not intend to increase voltage. This will give the benefit of increased amp hours. So 2.3 X 4 is 9.2 AH total. You'll be able to go farther than if you only used one dewalt.
Your AH consumption will depend on the efficiency of your system against the type of riding, and your usage of the system. Pedal a lot and save AH. Pedal very little and waste AH especially on starts. Lots of hills = more AH usage.
Series would increase your voltage, but that would mean more research on the controller. You might need to replace the controller to overvolt. You might be able to slightly overvolt if the controller's internals can handle it.
Combo, series plus parallel gives the best of both worlds, more volts and more AH, but split, so for example 2 series + 2 parallel would yield 72v @ 4.6AH.
One more thing... From what I've read the dewalts are more like 33 volts. Keep that in mind as well. You may lose a little top end speed, but the discharge will be more even across the full extent of the pack, compared to SLAs. SLAs tend to drop off in the middle of the discharge. On my set up, right now I'm just using 7AH SLA's 6 of them in series, so i have 72volts, but... with the controller I'm using plus the weight of the bike, batteries, cargo, including myself.. I'm getting about 5 miles range before I notice a significant drop off in performance. Not that great, so I too am looking at moving to A123 cells. I may start with 5 packs, and actually break down one of those 5 packs to increase cells for each of the other 4 packs. I'll likely add two cells to each, so that will boost the voltage to 39.6 per pack, but I'll run 2 series X 2 parallel, so that will actually work out to be (33v[10 cells] + 6.6v[2 added cells]=39.6v) * 2[packs in series] = 79.2 volts total then times 2 parallel, so the AH will move from 2.3 to 4.6.
Right now, I'm consuming about .5AH per mile. I can hit 32mph on a down hill with pedaling. On a flat i'm getting about 28-30mph, with or without pedaling respectively. When i go A123, I expect to drop about 15 pounds of weight, and end up at around 9.2AH, but that's going to take 8-10 batteries total.
Good luck!
Your AH consumption will depend on the efficiency of your system against the type of riding, and your usage of the system. Pedal a lot and save AH. Pedal very little and waste AH especially on starts. Lots of hills = more AH usage.
Series would increase your voltage, but that would mean more research on the controller. You might need to replace the controller to overvolt. You might be able to slightly overvolt if the controller's internals can handle it.
Combo, series plus parallel gives the best of both worlds, more volts and more AH, but split, so for example 2 series + 2 parallel would yield 72v @ 4.6AH.
One more thing... From what I've read the dewalts are more like 33 volts. Keep that in mind as well. You may lose a little top end speed, but the discharge will be more even across the full extent of the pack, compared to SLAs. SLAs tend to drop off in the middle of the discharge. On my set up, right now I'm just using 7AH SLA's 6 of them in series, so i have 72volts, but... with the controller I'm using plus the weight of the bike, batteries, cargo, including myself.. I'm getting about 5 miles range before I notice a significant drop off in performance. Not that great, so I too am looking at moving to A123 cells. I may start with 5 packs, and actually break down one of those 5 packs to increase cells for each of the other 4 packs. I'll likely add two cells to each, so that will boost the voltage to 39.6 per pack, but I'll run 2 series X 2 parallel, so that will actually work out to be (33v[10 cells] + 6.6v[2 added cells]=39.6v) * 2[packs in series] = 79.2 volts total then times 2 parallel, so the AH will move from 2.3 to 4.6.
Right now, I'm consuming about .5AH per mile. I can hit 32mph on a down hill with pedaling. On a flat i'm getting about 28-30mph, with or without pedaling respectively. When i go A123, I expect to drop about 15 pounds of weight, and end up at around 9.2AH, but that's going to take 8-10 batteries total.
Good luck!
Beagle123
10 kW
You should decide on a battery set-up and charging set-up together because they are interconnected. You should be able to use the controller, but you can't use the lead-acid charger on your a123 batteries. You need to find another way to charge your batteries.
This issue is a bit tricky, so I'd suggest that you research it for a while so you know what youre getting into.
As far as you battery configuration goes, you could buy 4 more cells then make 11 sub-packs of 4 cells in parallel. That means that you package 4 cells together to make one 3.3v, 9.2ah sub pack. Then connect all of these sub-packs in series to make a 36.1v, 9.2ah pack. You should get good performance from that battery.
Your batteries are excellent. a123s are capable of very fast discharge rates, and they are safe. Your 20 amp controller will be the bottleneck. You could go faster with a bigger controller, but I think the 20 amp one is a good choice because you will have a better range.
Another consideration is how you plan to solder/weld your cells together. The body of a123s are made of aluminum, so you can't solder onto them. You may need to find someone to spot-weld the sub-packs together.
But before you make your packs, you need to decide how you're going to charge the packs. I would suggest using either single cell chargers, or using a power supply to charge all the cells. Personally, I prefer charging the cells individually over charging them in series using a single 36v charger. I've read of too many people having problems with charging in series. THe single-cell charging is more simple.
I suggest a charging system for ypedal in this post:
http://endless-sphere.com/forums/viewtopic.php?t=2557
I posted a diagram with the configuration that I prefer.
Here is another post for the single-cell-chargers:
http://endless-sphere.com/forums/viewtopic.php?t=2586
xyxter knows a lot about this. I'm sure he'll be advising you soon.
I have been reading about making battery pack from the a123's. I'm sure you've seen this url before - http://www.terrorhurtz.com/a123/build.aspx - is this the correct way to make these packs, but only use 4 cells as per Beagle123 advise. I will review the notes on charging the packs. So far I'm understanding the basics to packs - thanks for the help.
Beagle123
10 kW
No, I hadn't seen that particular link. I didn't know that the ends were steel. That makes it easier to do. He's illustrating connecting batteries in series. The set-up that I'm suggesting involves connecting 4 batteries in parallel for each pack. You could use his techniques to make the sub-packs, just remember that the +'s all go together on your packs.
Also, notice how he's using a heavy duty soldering tool. Aparently you need lots of heat quickly to solder to the end off a battery. You want to heat it up quickly, solder it, and cool it before damaging the insides of the battery. You may be able to use a pencil torch, or butane soldering tool. I haven't used either yet, but others can advise you.
GGoodrum
1 MW
I used to sell a 10-cell a123 construction kit on my RC site. Here are the instructions: 10-Cell a123 Construction Kit. We would leave the tabs on and connected. In some of the higher powered helicopters powered by these packs, it is not uncommon to hit 90-100A peaks, albeit for only a few seconds at a time. The average discharge was about 30-40A. In any case, leaving the tabs on is not an issue.
If you are replacing a 36V SLA setup, you really want to use a 12s configuration. If you do, you can then use your 36V Soneil charger. With a 36V SLA setup, the charger will use a constant current mode up to a cutoff voltage of about 44V. At that point the charger switches to a constant voltage mode, and the current starts tapering off. When it gets down to about 10% of the max charge current, the charging stops. a123 cells, and other LiFePO4-based cells like the LiFeBatts, use the same sort of CC/CV charging profile, but with an optimum cutoff of 3.65V per cell. With a 44V cutoff, if you divide that by 12 you get about 3.67V per cell as the cutoff, which is extremely close.
The only problem is that bulk chargers like what you have don't balance the cells, so you need to either use an external balancer like the RC guys do, or you can get even one of the 2A single cell chargers from VoltPhreaks, and periodically charge each block of cells individually.
We did a whole thread, that is now a "sticky" at the top of this forum, on the "care and feeding" of a123-based packs. You should read that and you will have a better idea what we are all doing with these.
-- Gary
If you are replacing a 36V SLA setup, you really want to use a 12s configuration. If you do, you can then use your 36V Soneil charger. With a 36V SLA setup, the charger will use a constant current mode up to a cutoff voltage of about 44V. At that point the charger switches to a constant voltage mode, and the current starts tapering off. When it gets down to about 10% of the max charge current, the charging stops. a123 cells, and other LiFePO4-based cells like the LiFeBatts, use the same sort of CC/CV charging profile, but with an optimum cutoff of 3.65V per cell. With a 44V cutoff, if you divide that by 12 you get about 3.67V per cell as the cutoff, which is extremely close.
The only problem is that bulk chargers like what you have don't balance the cells, so you need to either use an external balancer like the RC guys do, or you can get even one of the 2A single cell chargers from VoltPhreaks, and periodically charge each block of cells individually.
We did a whole thread, that is now a "sticky" at the top of this forum, on the "care and feeding" of a123-based packs. You should read that and you will have a better idea what we are all doing with these.
-- Gary
auddog007 said:
My suggestion: Do NOT follow those instructions. A123 Systems warns against soldering to cell cases time and again. Others have reported trying and destroying cells. Do not remove the tabs. Solder to them -- quickly and carefully. The difference in power handling is relatively minor.
This link is better:
http://www.rcgroups.com/forums/showthread.php?t=599316
If you need to cut tabs use a pair of tin snips. Too easy to make a mistake with the Dremel tool. Remind yourself every step that the cells are always live and waiting to ruin tools that touch the wrong places. Use masking tape or other protection to cover adjacent surfaces when cutting, soldiering or whatever. Be fastidious or you'll have an accident.
Richard
GGoodrum
1 MW
auddog007 said:
This means 12 cells in series, not 10. The nominal voltage of these cells is 3.3V per cell, so 10 of them are really only 33V, not 36V, as DeWalt would have you believe. Call it marketing hype. Anyway, SLAs have 6 cells and a rated nominal voltage of 2V per cell, but are charged to about 2.4-2.5V per cell. The "resting voltage of a fully charged SLA battery is about 13.5-13.8V, or 2.3V per cell. With 3 of these in series, the fully charged voltage is about 40-41V.
So, with 3 SLA's in series, you have a nominal voltage of 36V, a fully charged voltage of 40V and a charger cutoff of 44V. To match a SLA setup with a123s, you need to look at the fully charged "resting" voltage, and the charger cutoff. Nominal voltages, which seem to be more subjective, don't compare well across chemistries. A fully charged a123 cell has a resting voltage around 3.5V and an optimal charger cutoff of 3.65V, so using 12 in series translates to 42V and 43.8V respectively.
Your 36V motor and controller setup has to be able to handle a max voltage around 45V so even though a 12s a123 setup has a bit higher "resting" voltage, it should work just fine. You will a bit more power, especially farther into the duration.
-- Gary
In looking over my options, I came across this website for a 12 cell pack - http://www.tppacks.com/proddetail.asp?prod=Battery%2DPack%2DKit - Has anyone worked with or would recommended this type of setup. I've looked at this several times as it appears to be an easy way to make a pack.
EMF
100 kW
auddog007 said:
I think Gary Goodrum has. :wink: There are posts about the kit in the care and feeding of A123 thread I believe. He supplies the kits and that is his website. It was a good idea and he tells about the pros and cons.
GGoodrum
1 MW
EMF said:
Yes, I think I have seen that...
I originally did that 12-cell kit for use in some of the RC helicopters that the normal styled packs wouldn't fi in, but I have used it recently to build some packs for the folding bike shown in my avatar. I started by doing to 16s versions and then sticking them side-by-side. Here's what they look like:
I now have some extra-wide 9-1/4" heavy duty shrink wrap so now three of these 16 cell "sticks" can fit side-by-side. Here's a shot of my folder with one of these 48-cell packs, with a 32-cell version on top:
These are simply five 16s strings that I connect together in parallel, for a 16s5p configuration. These have no balancer wires brought out, just the individual main leads for all five strings. For the most part, I just charge them all together, as one big pack, but occasionally, I check the voltage level of each string, and will sometimes charge each of the strings separately. For the most part, they all remain pretty well balanced and all have fully charged "resting" voltages of around 57.5-58.0V. Originally I had two 16s2p packs and one lone 16s1p "stick" that I used as an extra, for longer range. I noticed one of the strings had a resting voltage that had dropped to about 55.5V, so I opened up the pack and checked. I had one block of four cells that were at 3.35-3.50V, and the rest were up over 3.6V. I balanced all the cells and did a few cycles on the whole string, to make sure the cells were okay and then I built the the 3-string pack shown in the picture.
This is all temporary, so I keep my eye on the overall voltages, and try not to run this setup down too far. Usually my wife rides this bike and I usually don't have to put more than about 4-5 Ah back in after one of our typical 8-10 mile rides.
It has been my intention to do an ebike-specific a123 kit, or series of kits, but I've been struggling with trying to find the best format that doesn't take a week to build. My first atempt was here:
This used four 10-cell packs, pretty much just how they come out of the DeWalt packs, stuck together. There was a hand-wired balancing harness that brught out the connections which could be used with a standard RC-typ balancer, like the TP-210V shown. These connections could also be used with the 10-cell LVC protection boards.
The wiring harness took forever to make, so I know this wouldn't wrk as a "kit", so I did a new board that combined the wiring crossover connections with the LVC circuits, which simplified everything quite a bit, and got it all into the pack:
Two of the boards are used, but only one needs to be populated with the LVC parts. The balancer plugs from the DeWalt electronics module are cutoff and soldered onto the boards. Besides the main power leads, the balancer plugs are brought out as is a small two-wire JST plug for the brake inhibit signal.
I'm now using two of these 10s4p packs in series on my other folding bike, shown here in the middle:
Although I'm pretty happy with the 20s4p setup, I'm still not crazy about how this would do as a kit. I'm also not so crazy about the form factor, and about having to use the plastic end cases from the DeWalt packs which simply add bulk and weight, and don't really save all that much in assembly time. Plus, the packs are a bit "lumpier" than the clean-looking "stick" packs.
Instead, what I've decided to do is to go back to the inline format and make new boards for between the cells that will serve multiple purposes. They will have contacts for the cells, all the required interconnects, and the LVC circuits built-in. I'm think of doing two configurations, one that is 12s4p (40V/9.2Ah...), that can be used in existing 36V and 72V setups, and a 16s3p configuration that will be good for 48V setups.
More on all this later...
-- Gary
