Hyena
10 GW
Hey guys,
I thought I'd write up a quick review about the cheap ebay lipo battery packs.
I've seen several people asking about them, including those wanting to know about how they hold up long term. While my use with them so far couldn't be regarded as long term, I have put them through about 60 cycles and 1000km and they're not showing any signs of losing capacity yet. I'll update again when I get to 100 cycles (which some believe is about all you'll get from these) or if they start to die in the mean time.
These are the ones I'm talking about, from ebay seller TopRacing2007
I have 4 of the above 6S packs wired as 2S2P (which is actually 12S2P for the actual cells) for a 44.4v 8ah pack.
Most of my riding is to and from work, 4 days a week. It's about 15km with a few big hills, and I use around 5ah for the trip with moderate pedalling on the hills and little or no pedalling on the flats. I recharge at work for the ride home, so they're getting 2 cycles a day.
It's probably worth mentioning that I charge with a home made charger, after blowing up 2 hobby RC chargers I charge the 4 6S packs in parallel through a balancer at 9amps (so each pack is being charged at just over 1/2C)
The obvious attraction to these packs is they're cheap - $37 USD delivered is certainly a bargain for a 15C pack. And that's the first problem, they're not really 15C. They're rated for 15C max, 10C constant, but in my testing the max you can get from them is 8C, and which point they sag from a full charge of 4.2v/cell to the minimum recommended voltage of 3v/cell. Ouch. That's where these little guys fall down, they sag more than yo grandma's titties
In another thread liveforphysics quoted the internal resistance of similar 5ah cells to be around 15-20mOhm, dropping around 0.5v/cell @ around 25amps (so around 6v on a 12S pack, for a voltage of 44v) Based on my tests I've found these cells to be around the same, if not a bit worse. Running 2 of the 4ah packs in series for an 8ah pack they sag from 50.4v hot off the charge to around 42-44v when pulling around 20-25a, and then hover around 40v until you've used around 50% of their capacity. Towards the end the voltage starts to drop lower and lower and will hit 36v (3v/cell) pulling 20 amps after around 7.5ah has been used - so fairly close to their rated capacity.
Crusing along the flat at 30-40km/hr my 500w GM draws around 10-15a, which these batteries quite happily deliver with a lesser amount of sag (although still significant). They're usually warm after a 15km ride, but if you drain them much quicker pulling a constant 20-30amps until flat they get really hot. Not "oh no they're about to go thermonuclear" hot, but similar to holding a hot cup of coffee in a styrofoam cup.
So, would I recommend these to others ?
Yes and no.
If you want to pull 60 amps from them as they're supposedly capable of doing, you're going to be disappointed because they flatly won't do it. If you DO want to pull high current from them, or >5C without significant sag, hobbycity zippy packs or more expensive ones are the way to go. Zippy's come highly recommended, and I'll probably get a couple when this lot wear out , but they are more than twice the price.
Who I DO recommend these batteries to are people with fairly low powered controllers. If your controller is rated at 20-25a, you don't mind a little sag and don't need them to last 20 zillion cycles like LiFePO4, these are a great alternative to the likes of SLAs. I originally had 3 12ah SLAs weighing a metric kilotonne and these lipos are like stolen alien technology in comparison
Individually the 4ah packs wont last long in and ebike application (unless you've only got a 15a controller and dont need to go more than 10km), but run 2 in parallel for 8ah pack and they're fine for up to 30 amps (happier around 20). Better still if you ran them 3P to make a 12ah pack there would be much less sag as they'd only be working around 2-3C and you'll get the extra range.
I thought I'd write up a quick review about the cheap ebay lipo battery packs.
I've seen several people asking about them, including those wanting to know about how they hold up long term. While my use with them so far couldn't be regarded as long term, I have put them through about 60 cycles and 1000km and they're not showing any signs of losing capacity yet. I'll update again when I get to 100 cycles (which some believe is about all you'll get from these) or if they start to die in the mean time.
These are the ones I'm talking about, from ebay seller TopRacing2007
I have 4 of the above 6S packs wired as 2S2P (which is actually 12S2P for the actual cells) for a 44.4v 8ah pack.
Most of my riding is to and from work, 4 days a week. It's about 15km with a few big hills, and I use around 5ah for the trip with moderate pedalling on the hills and little or no pedalling on the flats. I recharge at work for the ride home, so they're getting 2 cycles a day.
It's probably worth mentioning that I charge with a home made charger, after blowing up 2 hobby RC chargers I charge the 4 6S packs in parallel through a balancer at 9amps (so each pack is being charged at just over 1/2C)
The obvious attraction to these packs is they're cheap - $37 USD delivered is certainly a bargain for a 15C pack. And that's the first problem, they're not really 15C. They're rated for 15C max, 10C constant, but in my testing the max you can get from them is 8C, and which point they sag from a full charge of 4.2v/cell to the minimum recommended voltage of 3v/cell. Ouch. That's where these little guys fall down, they sag more than yo grandma's titties
In another thread liveforphysics quoted the internal resistance of similar 5ah cells to be around 15-20mOhm, dropping around 0.5v/cell @ around 25amps (so around 6v on a 12S pack, for a voltage of 44v) Based on my tests I've found these cells to be around the same, if not a bit worse. Running 2 of the 4ah packs in series for an 8ah pack they sag from 50.4v hot off the charge to around 42-44v when pulling around 20-25a, and then hover around 40v until you've used around 50% of their capacity. Towards the end the voltage starts to drop lower and lower and will hit 36v (3v/cell) pulling 20 amps after around 7.5ah has been used - so fairly close to their rated capacity.
Crusing along the flat at 30-40km/hr my 500w GM draws around 10-15a, which these batteries quite happily deliver with a lesser amount of sag (although still significant). They're usually warm after a 15km ride, but if you drain them much quicker pulling a constant 20-30amps until flat they get really hot. Not "oh no they're about to go thermonuclear" hot, but similar to holding a hot cup of coffee in a styrofoam cup.
So, would I recommend these to others ?
Yes and no.
If you want to pull 60 amps from them as they're supposedly capable of doing, you're going to be disappointed because they flatly won't do it. If you DO want to pull high current from them, or >5C without significant sag, hobbycity zippy packs or more expensive ones are the way to go. Zippy's come highly recommended, and I'll probably get a couple when this lot wear out , but they are more than twice the price.
Who I DO recommend these batteries to are people with fairly low powered controllers. If your controller is rated at 20-25a, you don't mind a little sag and don't need them to last 20 zillion cycles like LiFePO4, these are a great alternative to the likes of SLAs. I originally had 3 12ah SLAs weighing a metric kilotonne and these lipos are like stolen alien technology in comparison
Individually the 4ah packs wont last long in and ebike application (unless you've only got a 15a controller and dont need to go more than 10km), but run 2 in parallel for 8ah pack and they're fine for up to 30 amps (happier around 20). Better still if you ran them 3P to make a 12ah pack there would be much less sag as they'd only be working around 2-3C and you'll get the extra range.