This is an interesting idea... a primary + buddy pack with these sticks would give you 20ah * 144v ~ 2.8kw pack...
Sam
Interesting but not that simple or very safe as we saw recently with parallel nimh packs.
As the cells have different charcteristics to the stock pack that would add extra complications for a simple parallel setup. It could perhaps be done with seperate grid chargers for each pack, a contactor to keep them seperated, full time temp sensing in both packs with some sort of alarm/safeties etc etc The fully charged resting voltage is probably not the same as well,so when first joined when the contactor engages serious current could flow between them. Lot's to consider.
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OBDIIC&C $50 inc software, pcb, switch and obdii plug.
IMAC&C HCH1 $50 inc software and pcb.
Thanks for posting that graph and doing the initial testing.
When I was testing some cells with Ron to determine what would work we looked at many 10AH cells that worked pretty good for several cycles, and then took a dive in performance and then failure after only 20 or so cycles. the problem was mainly due to the internal construction, so I will start my examination of the cells by discharging one, and cutting open the case to look at the construction. Some cells were made with a plastic mesh that had conductive powder, and very poor connections to the cell terminals, the MAXIMA, and stock cells have metal foil and multiple welds to each wrap on both the top and bottom.
I want to make up a 6 cell stick with the 2 MAXIMA cells, 2 KingKong cells, and 2 from another vendor and trace all of them at different charge discharge rates.
Yeah, getting cycle life data is pretty important. It's not difficult overall to make a cell that will take the current(and not vent), but it's another thing for the cell to take the current and still be usable after 500 cycles.
Sucre, Mike's analysis of the internal construction should tell us what we need to know, but maybe you can help. These cells are hand made, correct?
In that case, unfortunately they will never be suitable for use in a car, even if you get the IR down. Consistency is king.
Two cells, one with 0.002 ohms of IR and one with 0.003 ohms of IR. After a 50 mile drive cycle pushing +/- 1.5kWh, these two cells are 0.7Wh out of balance just from the drive alone. When you factor in self discharge etc, things get pretty complicated, but it illustrates the problem nicely.
0.7Wh isn't much, but that's only 50 miles. Times that by 2000 for 100,000 miles, and you've got an IMA light.
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Bumblebee Batteries, LLC - Helping your hybrid get from point A to point Bee!
Yeah, getting cycle life data is pretty important. It's not difficult overall to make a cell that will take the current(and not vent), but it's another thing for the cell to take the current and still be usable after 500 cycles.
Sucre, Mike's analysis of the internal construction should tell us what we need to know, but maybe you can help. These cells are hand made, correct?
In that case, unfortunately they will never be suitable for use in a car, even if you get the IR down. Consistency is king.
Two cells, one with 0.002 ohms of IR and one with 0.003 ohms of IR. After a 50 mile drive cycle pushing +/- 1.5kWh, these two cells are 0.7Wh out of balance just from the drive alone. When you factor in self discharge etc, things get pretty complicated, but it illustrates the problem nicely.
0.7Wh isn't much, but that's only 50 miles. Times that by 2000 for 100,000 miles, and you've got an IMA light.
Hello Eli, Thanks for all your information. I just came back to the office from the holiday today.
The IR of our 10000mah cell is 4mΩ, it is right. longevity is always sacrificed for capacity, It is also true.. with the 10000mah capacity, of course the life span of our cells can't be so long as the stock cell, but that doesn't mean the cycle life of our cell is too low to be accepted.
As you mentioned"It's not difficult overall to make a cell that will take the current(and not vent), but it's another thing for the cell to take the current and still be usable after 500 cycles",
I have to say, according to noramal use by the hybrid car, the cycle life of our cells can be 800 times, as I stated in my thread, life span of our stick is above 4 years.
Of course, these cells are not hand made we may try to improve the IR and Internal construction in the future, but we also have to consider the cost. Anyway, at least I still think our current cells is enough for HEVs.
Hello Eli, Thanks for all your information. I just came back to the office from the holiday today.
The IR of our 10000mah cell is 4mΩ, it is right. longevity is always sacrificed for capacity, It is also true.. with the 10000mah capacity, of course the life span of our cells can't be so long as the stock cell, but that doesn't mean the cycle life of our cell is too low to be accepted.
As you mentioned"It's not difficult overall to make a cell that will take the current(and not vent), but it's another thing for the cell to take the current and still be usable after 500 cycles",
I have to say, according to noramal use by the hybrid car, the cycle life of our cells can be 800 times, as I stated in my thread, life span of our stick is above 4 years.
Of course, these cells are not hand made we may try to improve the IR and Internal construction in the future, but we also have to consider the cost. Anyway, at least I still think our current cells is enough for HEVs.
you will see its workshop photos, lots of workers sitting and making battery.
photos workhop2, workshop3 and workshop4.
workhop1 is test machine.
Hand made cells have big range in quality, you can selete good cells for sample purpose, but for real production, how you control it? You test every single cell?
In an unrestricted car with normal IMA function I agree they won't last that long, the IR is too high, but the actual stick/internal cell construction is also very important for longevity and ability to handle the current. Be interesting to see what Mike finds with his examination.
The Capacity is good though, so for use at more modest drains say 10A of assist you might get an hour out of them in a light phev mode. That's a potential big increase in mpg on a shortish commute.
The option to use an updated MIMA or IMAC&C to manage the ecm IMA requests and limit them to lower current levels is also a possibility for working with less capable cells. Perhaps we need a volunteer with an HCH1 to test them in a reduced current setup.
It won't make replacement packs cheaper, as most of the cost is in the time to assemble/dissasemble/test & charge the packs, plus you will have to factor in the cost of the IMA device and instalation. Anyway that's for discussion on a seperate thread if someone is interested they can start one.
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OBDIIC&C $50 inc software, pcb, switch and obdii plug.
IMAC&C HCH1 $50 inc software and pcb.
you will see its workshop photos, lots of workers sitting and making battery.
photos workhop2, workshop3 and workshop4.
workhop1 is test machine.
Hand made cells have big range in quality, you can selete good cells for sample purpose, but for real production, how you control it? You test every single cell?
Workers sitting and making battery? NIMH batteries can't be so easily produced like that... they are not making batteries, they are doing processing, packing, sample checking jobs..etc
We summit samples for test, that means we can ensure of the quality of mass production, what 's more, we offer one year warranty for our cells, if they are defectifve, they can be returned to us full at our expense, so please don't worry about that.
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we may try to improve the IR and Internal construction in the future, but we also have to consider the cost. Anyway, at least I still think our current cells is enough for HEVs.
