ebent
10 kW
How does a123 compare to all the rest. Regardless of price, which are the best. And considering price, which is the best value?
Thanks,
ebent
Thanks,
ebent
Battery comparison
- Thread starter ebent
- Start date
dogman dan
1 PW
Of lifepo4, A123 is the best. Some of the new lipo blows it away for c rate and price, but lifepo4 has much better lifespan. Enough A123's to go 30 miles, and you aren't worried about c rates anymore.
cell_man
100 kW
You don't need more C rate than an A123 cell can deliver for an ebike. The main advantage with LiPo is the higher energy density. If you figure in the lifecycle, safety and ability to accept abuse, A123 cells are very good value. When you also figure in the additional balance chargers, not using the full capacity of the pack, and various other bits of equipment that is used to keep LiPo safe, the difference in cost becomes smaller, in fact you might well find it works out more expensive to go LiPo, even in the short term.
A terminated 14S (46.2V nominal) 20Ah block of A123 20Ah pouch cells weighs about 7kg (including mechanical termination, a little over 6.5kg bare cells) and has approximately 924Whrs. This is approximately equivalent to a 12S LiPo pack (44.4V nominal) with regards to voltage. The difference in energy density is not so significant between the best LiFePO4 and LiPo. The prices that A123 cells are available for are approximately 50% higher than LiPo from HC.
A terminated 14S (46.2V nominal) 20Ah block of A123 20Ah pouch cells weighs about 7kg (including mechanical termination, a little over 6.5kg bare cells) and has approximately 924Whrs. This is approximately equivalent to a 12S LiPo pack (44.4V nominal) with regards to voltage. The difference in energy density is not so significant between the best LiFePO4 and LiPo. The prices that A123 cells are available for are approximately 50% higher than LiPo from HC.
dogman dan
1 PW
Amen to that dude. The lipo advantage is ONLY for carrying really small ah size packs that series enough to go to really high volts in my opinion.
I fail to understand why people are going to lipo when all they want is 30 amps or so of 48v. Sooo much easier to use lifepo4 with a bms for 99% of ebikes.
But racing is another story, and why I'm currently buying into lipo. I just can't afford to buy a race pack in A123's. Unless somebody wanted to sponsor a rider perhaps? Even then, 20 ah 72v would be a bit heavy to throw into the corners, and hard to place properly on the frame.
I'm a huge proponent for the right tool for the job at hand. Years in constrution taught me that, and at play the same thing applies. When I skiied, I had 6 pairs of skis. Now I'm into bikes, and have 6 kinds of bikes.
For most of my Ebike riding though, I would LOVE to have an A123, 48v 20 ah pack, split into two blocks for panniers, and a reliable 60 amp discharge-10 amp charge bms. A good 24v pack with bms would work fine, and charge both at the same time with 5 amp chargers. It would get you into pretty short charge times. Build it and we will come.
I fail to understand why people are going to lipo when all they want is 30 amps or so of 48v. Sooo much easier to use lifepo4 with a bms for 99% of ebikes.
But racing is another story, and why I'm currently buying into lipo. I just can't afford to buy a race pack in A123's. Unless somebody wanted to sponsor a rider perhaps? Even then, 20 ah 72v would be a bit heavy to throw into the corners, and hard to place properly on the frame.
I'm a huge proponent for the right tool for the job at hand. Years in constrution taught me that, and at play the same thing applies. When I skiied, I had 6 pairs of skis. Now I'm into bikes, and have 6 kinds of bikes.
For most of my Ebike riding though, I would LOVE to have an A123, 48v 20 ah pack, split into two blocks for panniers, and a reliable 60 amp discharge-10 amp charge bms. A good 24v pack with bms would work fine, and charge both at the same time with 5 amp chargers. It would get you into pretty short charge times. Build it and we will come.
cell_man
100 kW
Thanks Dogman 
I'll have some rather special 2.3Ah 26650 cells arriving soon and I'm getting fixed up with a spot welder this week so there will be some built to order LiFePO4 packs coming soon and at very competitive prices. 30C and ready to go, with or without BMS as requested. Much easier to assemble and you're not tied to big Ah packs like the big pouch cells. Hopefully can get a few more of those as well soon, and I still have a few of the 15Ah cells remaining.
How long is the race? 72V, 20Ah is a pretty big pack.
I'll have some rather special 2.3Ah 26650 cells arriving soon and I'm getting fixed up with a spot welder this week so there will be some built to order LiFePO4 packs coming soon and at very competitive prices. 30C and ready to go, with or without BMS as requested. Much easier to assemble and you're not tied to big Ah packs like the big pouch cells. Hopefully can get a few more of those as well soon, and I still have a few of the 15Ah cells remaining.
How long is the race? 72V, 20Ah is a pretty big pack.
dogman dan
1 PW
About 10 miles of racing in the heat last year, 12 laps, plus the pre lap, and finish lap to get back to the pits. I think 72v 10 ah will be plenty, but 72v 5 ah pretty tight. Till I get the bike back on that track at 72v, I won't know for sure how many watthours per lap I need. I only have some data from 48v speeds.
At 48v, I used about 6 ah in the race last time. Less wind resistance slow, so I don't think 5 ah of 72v will do it.
It will be really nice to have A123 in bike size packs with a good bms. Any chance you will use the Fetcher Goodrum design?
At 48v, I used about 6 ah in the race last time. Less wind resistance slow, so I don't think 5 ah of 72v will do it.
It will be really nice to have A123 in bike size packs with a good bms. Any chance you will use the Fetcher Goodrum design?
cell_man
100 kW
I was trying to source some of the Ggoodrum BMS some time back but they were out of stock at the time. I can't see why I can't in the future if there is a demand. The bigger BMS I've been selling with 80A constant rating are pretty good though. They don't trip with peak currents of well over 100A so more than enough for the vast majority of users. Fitted with 8pcs of genuine IRFB4310 Fets for the discharge, so they are well up to the job.
I found there was a big jump in Whrs used when the speed increased with different motor windings, but some of that may be down to the efficiency at the load point the respective windings were operating in. Typically, my bike is now using up to 35Whrs/km but more typically closer to 30Whrs/km with the lower speed windings, topping out at 58kph, but gets to 55kph quite quickly. With the higher speed windings it was up around 45Whrs/km for an extra 10kph, so 68kph max. The high speed setup would pull almost 3000W to maintain 68kph, whereas the lower speed setup is pulling just over half that to maintain 58kph. What sort of Whrs were using per mile/km when you raced last time?
Also, after having a play with using a single front motor, the front wheel spin is pretty much no problem. It seems like the front wheel spin I see on my bike is due to fact there are dual motors on a full suspension bike (fairly cheap) with a seat pole mounted rack which causes the front wheel to get unloaded under acceleration. Getting some batteries in the frame should help this situation. I've got 64 26650s (just under 5kg of cells) lined up which will give me 48V and about 9Ah which I intend to fit in the triangle and should be enough for most of my journeys.
I found there was a big jump in Whrs used when the speed increased with different motor windings, but some of that may be down to the efficiency at the load point the respective windings were operating in. Typically, my bike is now using up to 35Whrs/km but more typically closer to 30Whrs/km with the lower speed windings, topping out at 58kph, but gets to 55kph quite quickly. With the higher speed windings it was up around 45Whrs/km for an extra 10kph, so 68kph max. The high speed setup would pull almost 3000W to maintain 68kph, whereas the lower speed setup is pulling just over half that to maintain 58kph. What sort of Whrs were using per mile/km when you raced last time?
Also, after having a play with using a single front motor, the front wheel spin is pretty much no problem. It seems like the front wheel spin I see on my bike is due to fact there are dual motors on a full suspension bike (fairly cheap) with a seat pole mounted rack which causes the front wheel to get unloaded under acceleration. Getting some batteries in the frame should help this situation. I've got 64 26650s (just under 5kg of cells) lined up which will give me 48V and about 9Ah which I intend to fit in the triangle and should be enough for most of my journeys.
dogman dan
1 PW
A bms good for 80 amps oughta be enough for bikes.
My cycleanalyst arrived the day after the race, so I don't have any accurate readings.
Using a pingbattery, I thought I had used it up towards the end of the race because I started to really slow down. But when I charged, I found I'd used about 5-6 ah of the 48v 15 ah battery. Hammering the throttle every turn really hit it hard. Every 20 seconds another amp spike. The 2c cells didn't like it.
Once my lipo gets here, any day now, I'll go out and do some similar riding to the track in a parking lot and see how far I get on a 5ah 20s setup. I see no reason why I'd need more than 10 ah for 15 laps on that track, .8 miles per lap.
Now that I think about it, a two motor bike might be more likely to have front wheel spin. The back wheel will tend to lift the front up when starting.
I figured if I ever did a two wheel motors bike I'd want two throttles. Then maybe you could hit the front throttle first.
My cycleanalyst arrived the day after the race, so I don't have any accurate readings.
Using a pingbattery, I thought I had used it up towards the end of the race because I started to really slow down. But when I charged, I found I'd used about 5-6 ah of the 48v 15 ah battery. Hammering the throttle every turn really hit it hard. Every 20 seconds another amp spike. The 2c cells didn't like it.
Once my lipo gets here, any day now, I'll go out and do some similar riding to the track in a parking lot and see how far I get on a 5ah 20s setup. I see no reason why I'd need more than 10 ah for 15 laps on that track, .8 miles per lap.
Now that I think about it, a two motor bike might be more likely to have front wheel spin. The back wheel will tend to lift the front up when starting.
I figured if I ever did a two wheel motors bike I'd want two throttles. Then maybe you could hit the front throttle first.
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