keno wrote: Suspect a 'Gold Rush' phenomenon will occur once the revisions are confirmed
Sutho wrote:Although.....I'm not liking Jack Rickards comment about the modules not being new. I had assurances in numerous emails that the ones I will receive are 100% new.
deVries wrote:The 28s3p "bare" module weight *not* counting the cells is just under 18-lbs.
Cell weight is just below 89-lbs. 84 cells x 480g.
Total module weight is 106-lbs. EDIT: 106-lbs is only referenced verbally on video from Jack Rickard's 28s3p module. So, all numbers depend on the accuracy of his measurement. The weights below should *not* be on the low-side or underestimated, imo, so actual weights may be very slightly less than what is predicted below.
7s3p packs are therefore going to weigh about 1/4 the above numbers:
The 7s3p "bare" module weight *not* counting the cells is just under 4.5-lbs for module only.
21 cells add about 22.5 lbs, so total weight for a 7s3p module will be about 27-lbs or slightly less.
cwah wrote:I'm trying not to go over 11 lbs for batteries
Wondering if it would be cheaper without module.
silentflight wrote:FYI guys,
Jack Rickard discusses the A123 module he ordered from China in this week's video starting at 24' 25"
zEEz wrote:I'm putting a HUGE effort in NOT trying to order at least a single 7s3p pack to
rewire as a 18s1p for my e-pocketbike that would really shine with 20Ah and 68v.
njloof wrote:I'll let you know how it goes
It sounds like he is comparing them to some other product he is using/promoting (green energy 12v?).
If done correctly there is no reason it should be bad, just as if done correctly top balancing should not be bad. Remember, "top balancing" means you are unbalanced at the bottom. I've run my pack of 100ah CALB cells bottom balanced with no BMS for the last three years, including driving my car till it stopped once, with no issues. In that case bottom balancing saved my cells.I was suprised to see this guy "bottom balancing" since it is widely regarded as ineffective and bad for cells.
10C on a 3P pack is 600 amps, how long do you think you'll be pulling that type of current? 180 amps is only 3C for a 3P pack, I wouldn't expect a reasonably efficient vehicle to pull much more than that on average. Jack's cars are small Porsche kit cars so they are fairly efficient.
He keeps talking about how the cells run cool at a 45a, but this is only a 0.75c discharge so I don't see that as a relevant data point; I already know that in small ebike packs at 6c I don't have a heat issue, but I am curious how this will hold up at 10c in a 300 cell pack. He also mentions how the typical Electric car pulls 100a-150a - which strikes me as odd, I see higher continous discharge at 165v on my 480lb Vectrix motorcycle and my VW bus conversion. Maybe he is talking about slow speeds, or high voltage with 384v AC systems, KW would have been a more useful metric.
oatnet wrote:I think it will be pretty easy to dremel off the "Buss Bars", open the case, and extract the cells, but I had a tough time working with the short tabs, maybe you will do better. ... Yes, one cannot solder the tabs of these cells, and tig would heat-damage the cells, but I have posted a thread on spot-welding the tabs that is effective.
oatnet wrote:I didn't realize that folks here were planning on harvesting the cells from them instead of using them intact in the modules.
liveforphysics wrote:It has 30s 45c nanos now.
I got new special firmware that allows 120v.
deVries wrote:though maybe cutting out three 7s1p strings would work & still be very useful to do that. For instance, make a 21s1p battery from one module. But, we don't know if that can be done yet.
If done correctly there is no reason it should be bad, just as if done correctly top balancing should not be bad. Remember, "top balancing" means you are unbalanced at the bottom. I've run my pack of 100ah CALB cells bottom balanced with no BMS for the last three years, including driving my car till it stopped once, with no issues. In that case bottom balancing saved my cells.
I think that's just a reference to some experimenting he's been doing on A123 pouch cells, casting them in a plastic block.
I think you meant higher SOC, but that does not have "less" impact on the cells. Holding a cell at a higher voltage for longer periods can cause the electrolyte to breakdown faster, that's why when storing cells it's recommended to do so around 50% SOC or less. Higher voltages cause electrolyte instability. Ideally cells would be cycled in their middle SOC range, A123 testing has shown cycling in the tens of thousands when cycled between the middle range of SOC.oatnet wrote:
Whether you top or bottom balance, the weakest cell determines how much capacity you can take out of the pack. However, the lower the DOD, the more impact to the cell's cycle life. Top balancing runs to a higher DOD, so the cells are less impacted.
Who says it's a regular occurrence? Since the initial bottom balance when assembling the pack I've only done it one other time in three years just as a check, it didn't really need it.Regularly discharging the cells to a bottom balance means you are regularly reducing cycle life.
Indeed, and not only do I rarely hit 80% DOD I also avoid charging above 90% or so most of the time, prolonging cell life.In addition, a properly sized automotive pack should have headroom that you rarely, if ever, hit that 80%DOD mark.
Yes.When you say "driving my car till it stopped", I assume you are saying that you discharged your pack far enough to hit your controller's LVC, and it was easier to trip because all of your cells were low.
As described above I don't think I've reduced my pack life, and by spending less time at a high SOC I'm probably extending it.The exact same effect could be achieved with top balancing, and setting a higher LVC, without reducing your pack's cycle life, and catch the weak cell even earlier.
No loss of focus, I wanted to see what happened, and knew with a bottom balanced pack I would not be driving any single cell to zero. As I said, I've gone three years with no BMS and no problems.However, the fact that you lost focus long enough to let the pack discharge that low indicates you may be a good candidate for using a BMS.
At first blush that sounds like a heavy, cell-killing heat trap but maybe they are liquid cooled... I'll have to go read more.
JRP3 wrote:Who says it's a regular occurrence? Since the initial bottom balance when assembling the pack I've only done it one other time in three years just as a check, it didn't really need it.oatnet wrote:Regularly discharging the cells to a bottom balance means you are regularly reducing cycle life.
oatnet wrote:edit: HumboldtRc, PICS PICS PICS please
HumboldtRc wrote:I just got my 2 7s3p A123 modules!
They are clearly used/rejects. The 2 I got are different. One is off-white and one is black. They both read 23.11 volts at the terminals. There is a big dent in the black one, also the heat-sink plates looks thiner on the black one. The white one is not square, it was put together wrong, the whole pack leans.
HumboldtRc wrote:How do I make the pictures smaller?
Here is the link to my fackbook album.
http://m.facebook.com/?_rdr#!/media/set ... 1256001296