I have 2 posts in e-bikes tech. about the design i'm working on, but what I'm asking here is where in the world I find cells or a pack of NiCd, NiZn if available, or LiPO4 with BMS that totals 55Ah@72v nom.,thats about 4KW right?, for the best price.(order contact?) I'm open to any chemistry that can work below 0 C deg. without an extreme power loss (oversize pack so % loss can be ok). Charging at a high rate is also very helpful, so info. on such a high amp output 120v ac input, 72v+ dc on-board charge system would be cool. Avg. temp here is rarely above 60 F deg. and avg. pack temp will often be in the 40's F. It is also a marine environment and the few steep hills require a high discharge rate. AGM's was a thought due only to economy and C rate but the colder temps., and the extra wt.(on trike) seem to pose issues. All info. can be helpful...Thanks...
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NiCd/NiZn?/LiPO4 cold temp. operation best price 55Ah@72v ??
- Thread starter northstar
- Start date
dnmun
1 PW
i think headway will build you a 72V40Ah pack, maybe they can do 60Ah under the same BMS. i think shunt current is about 140mA so you can figure how much variation in balance you could tolerate.
Gregory
100 kW
If you're in the US, evcomponents.com is selling Thundersky lifepo4 60Ah for $66. He may be able to recommend a BMS.
They can only discharge 2-3C, and how fast can you realistically charge a 60Ah pack anyway?
But they seem cheap!
They can only discharge 2-3C, and how fast can you realistically charge a 60Ah pack anyway?
But they seem cheap!
rkosiorek
100 kW
SLA or AGM 12V 55Ah batteries (like the ones i use in my wheelchair) hold 350 to 400Wh each when used at realistic drain levels and at 75F temperatures. the advertised rating is a 20hr rating at a very low current drain. my experience is that they will only deliver 50 to 70 (75% DOD) cycles at this performance level. the performance level and capacity will then decline gradually until you reach 200 or 250 cycles. at that point the performance will be about half of what it was originally.
as far as low temperature performance goes. at freezing the range is only half of what it would be at room temperature. at 0F i'l be lucky to make a couple of blocks.
NiCad or LiFePO4 packs will hold their Wh rating much more constant, their Ah rating does not drop as radically as the current is increased. so a NiCad or LiFePO4 pack can be rated lower in Ah but still deliver the same Wh. also the cells will go through many more cycles before the performance starts to decline.
I don't have any lab style measurements to back me up. but i have used a 20Ah 24V pack of PSI/BMI/LifeBatt cells on the wheelchair. these packs have gone through approx. 150 cycles but only 40 or 50 of them on the wheelchair. at 20Ah you would expect only half of the range. in practice it is about 2/3rd the range.
where i was getting 18 to 20Km range with the AGM (approx 100cycles old) I was getting 12 to 15Km range with the LiFePO4. as a bonus the performance of the lithium did not sag as poorly as the AGM during the discharge. partially discharged AGM have a lot less omph than they do fresh off of the charger. at freezing temperatures i would get 9 to 12Km with the AGM and 8 to 10Km for the LiFePO4. YES - I was getting pretty much the same range frome the 20Ah Li pack as i was from the 55Ah AGM at freezing.
I expect that the performance will decline as the temperature drops. but i think that the range will still be acceptable at 0F for LiFePO4. the performance envelope for the LiFePO4 is roughly from -10F to 120F. at -10F they should have about 50% capacity. also i expect to get 800 to 1000 cycles from the LiFePO4 as opposed to 250 to 300 from AGM. initially they are higher cost but over the long haul they will end up being cheaper.
in both cases the batteries are high end packs. OPTIMA D34 "Yellow Top" for the AGM (approx $400 cost). and 16 X 40138F1 LiFeBatt green cells for the LiFePO4. i am using a modified BMS from Batteryspace and a modified Soneil charger. total cost for the LiFePO4 would be about $850.00. but since i expect the pack to last at least 3X as long it will end up being cheaper.
given my experience i expect a 30Ah LiFePO4 will equal the range of the 55Ah AGM. the performange gap will widen as the temperature drops. at freezing the performance will be greater. or a 40Ah LiFePO4 pack will easily exceed the performance at any point.
i have no experience with the less expensive "Duct Tape" packs available on eBay. i don't know if they will perform as well. i know that they will not handle the high discharge rates as well as the cells i am using.
looking at prices for high rate NiCd - they are no longer competitive in price. NiCd will have to be made up from a couple of hundred individual cells spot welded together. so you would have to add assembly costs.
for sources look at:
http://www.batteryspace.com
check out thier "battery univeristy links" and general info on batteries. i am using 2 BMS bought from them in 2 of my packs.
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4060
these are sources for the PSI/BMI/LifeBatt cells.
http://www.lifebatt.com
rechargeablelithiumpower.com
rick
as a bonus the LiFePO4 packs weigh a lot less
as far as low temperature performance goes. at freezing the range is only half of what it would be at room temperature. at 0F i'l be lucky to make a couple of blocks.
NiCad or LiFePO4 packs will hold their Wh rating much more constant, their Ah rating does not drop as radically as the current is increased. so a NiCad or LiFePO4 pack can be rated lower in Ah but still deliver the same Wh. also the cells will go through many more cycles before the performance starts to decline.
I don't have any lab style measurements to back me up. but i have used a 20Ah 24V pack of PSI/BMI/LifeBatt cells on the wheelchair. these packs have gone through approx. 150 cycles but only 40 or 50 of them on the wheelchair. at 20Ah you would expect only half of the range. in practice it is about 2/3rd the range.
where i was getting 18 to 20Km range with the AGM (approx 100cycles old) I was getting 12 to 15Km range with the LiFePO4. as a bonus the performance of the lithium did not sag as poorly as the AGM during the discharge. partially discharged AGM have a lot less omph than they do fresh off of the charger. at freezing temperatures i would get 9 to 12Km with the AGM and 8 to 10Km for the LiFePO4. YES - I was getting pretty much the same range frome the 20Ah Li pack as i was from the 55Ah AGM at freezing.
I expect that the performance will decline as the temperature drops. but i think that the range will still be acceptable at 0F for LiFePO4. the performance envelope for the LiFePO4 is roughly from -10F to 120F. at -10F they should have about 50% capacity. also i expect to get 800 to 1000 cycles from the LiFePO4 as opposed to 250 to 300 from AGM. initially they are higher cost but over the long haul they will end up being cheaper.
in both cases the batteries are high end packs. OPTIMA D34 "Yellow Top" for the AGM (approx $400 cost). and 16 X 40138F1 LiFeBatt green cells for the LiFePO4. i am using a modified BMS from Batteryspace and a modified Soneil charger. total cost for the LiFePO4 would be about $850.00. but since i expect the pack to last at least 3X as long it will end up being cheaper.
given my experience i expect a 30Ah LiFePO4 will equal the range of the 55Ah AGM. the performange gap will widen as the temperature drops. at freezing the performance will be greater. or a 40Ah LiFePO4 pack will easily exceed the performance at any point.
i have no experience with the less expensive "Duct Tape" packs available on eBay. i don't know if they will perform as well. i know that they will not handle the high discharge rates as well as the cells i am using.
looking at prices for high rate NiCd - they are no longer competitive in price. NiCd will have to be made up from a couple of hundred individual cells spot welded together. so you would have to add assembly costs.
for sources look at:
http://www.batteryspace.com
check out thier "battery univeristy links" and general info on batteries. i am using 2 BMS bought from them in 2 of my packs.
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4060
these are sources for the PSI/BMI/LifeBatt cells.
http://www.lifebatt.com
rechargeablelithiumpower.com
rick
as a bonus the LiFePO4 packs weigh a lot less
