Does anyone know anything about these batteries? They sound impressive.
"Typically half the weight of lead acid with several times the lifespan, BMI cells and batteries are a superior performing substitute for lead acid batteries. While many of the Chinese cell manufacturers will quote you a life of 1000 cycles, BMI cells have been independantly laboratory tested and proven to have a working life in excess of 8000 cycles.
These cells on offer are rated at 3.3V10Ah. Rated discharge is 200 amps peak (20C) and 120 amps continuous discharge rating (12C). 10Ah is a genuine minimum capacity and independant testing recently showed these cells will measure an actual capacity of more than 10Ah. These cells have M6 threaded terminals so they are easy to bolt together to form battery packs of any voltage or capacity (no need for a battery tab spot welder). Simply bolt them together with copper link bars (available separately) or eye terminals and wire".
A 36 volt 10 Ah pack that I'm thinking would work for me would be like $430.00, would still need a BMS and charger. With the PingPing batteries, I would have to go with the 36 volt 20 Ah pack which would probably be like $600.00 which includes BMS, not sure if he still provides a charger in the deal.
Deron.
sounds good , can you post a link to the webiste?
The cells are on e-bay, here is the auction.
http://cgi.ebay.com/Electric-Bike-Bicycle-Scooter-LiFePO4-e-bike-cells_W0QQitemZ280260876823QQihZ018QQcategoryZ19025QQssPageName...
Deron.
They do sound good. For your setup they may well be great. However, for larger pack 40Ah/60V I'm not sure how the size and weight compare to the TS equivalents. They certainly have better power capabilities.
One thing that got me thinking though is the economies over the life of the batteries. These batteries are more expensive than the TS cells. In terms of dollars per cycles they're actually cheaper. However, this is where one has to decide how long do they need to last?
A 60V/40Ah pack of TS cells in an XM-3500Li should last around 60,000 miles (40 miles per charge * 1500 charges). For a bike in this class that could easily represent 10 years. A similar pack built from these BMI cells would last 320,000 miles (40 miles * 8000 cycles) which is certainly way beyond the life expectancy of the bike. So, in this example you are getting better cells but from my point of view they're over specified for the job.
I know you're looking at putting a smaller pack on an e-bike - but it might be worth doing a similar sort of "back of an envelope" cost per cycle vs. cycles needed analysis to figure if you need to spend this amount of money.
Just a thought - they do look like good cells and in a 10Ah pack I assume the higher discharge capability is much more important.
John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.
The bmi cells are supposed to be very good, especially for high rate of discharge and rapid recharging. Ordinary ebikes need no more than duct tape batteries, but the larger sise needs to be bought to provide enough amps. But if you don't need so much range, or you do need a lot of amps, these are the cells to use. Used conservatively, they should go a lot of cycles, though I hadn't heard of 8000. As for them outlasting the bike, my Ping pack has outlasted one bike and one motor, just this summer. I figure for cheap bikes, possibly two a year. Some stuff on them from a guy who just got his on endless sphere, in the battery section. These are the cells I want for a motorcycle some day. Fast charging is very cool when outlets aren't locked.
Be the pack leader.
36 volt sla schwinn beach cruiser
36 volt lifepo4 mongoose mtb
24 volt sla + nicad EV Global
I have a Pedelec with 24V 20AH PingPing batteries in it right now. The pack is overkill in the way of range for me. Right now I'm building a Pedelec that uses the same drive as my first Pedelec, only I upping the voltage to 36. I'm thinking the BMI batteries would be a better choice in that I would not have to carry the extra Ah's that you have to with the lower discharge rate of the Ping's. I even had to mod the 24V 20Ah Ping BMS to keep it from cutting out on my 400 watt motor. I'm thinking I might have the same problem with a 36V 20Ah Ping battery pack. A 36V 10Ah BMI would have no problem supplying all the amps I would need. I'm also thinking that I would probably get over 20 miles out of the BMI which would be plenty for the riding I do.
Deron.
Maybe the 36v would be enough, I've had no cutouts with mine. With only 24v though, the amps need to be more to get the same watts, so maybe that explains the cutouts. Usually that problem is found on 10ah batteries, or 1000+ watt motors. In any case, the BMI's will do the trick. 10 c or whatever they are, is a lot more than 1c. Fortunately for me the 36v 20 ah I have exactly fits my motor and my ride. Now I just need to find a motor that can handle riding in hell.
Be the pack leader.
36 volt sla schwinn beach cruiser
36 volt lifepo4 mongoose mtb
24 volt sla + nicad EV Global
I have been in touch with BMI and got some information and prices.
"If you are looking at a 36 volt pack with VMS i would suggest you buy a "designers prototype pack". This is just a regular factory pack with VMS fitted but there are no screws used since the battery is temporarily held together with electrical tape. This is done so you can re-build the pack into a different shape, remove cells etc. There are 3 VMS boards fitted since each one is used for 4 cells.
The 36V10Ah designers pack which includes VMS is US$675
The red 36V charger as in the attached photo is US$205
Shipping for the battery and charger is US$159 by airmail and US$87 by seamail."
This is way to much for my taste, $1,039.00. The individual cells are only supposed to be $39.00 each, I figure 11 3.3 cells volt for a 36 volt pack, I do not see how it ends up being $675.00, that means they are charging $250.00 for the 3-VMS's. They have a nice 8 amp charger, but I do not need that nice of a charger, a PingPing charger which comes with the battery pack does the job just fine. Ping has a better deal on shipping too.
Deron.