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The eBike thread
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So I hooked up a single 4Ah battery pack after I charged it. Only went to 40.2V (for those of you who don't know a 10S pack of 3.7V nominal 18650 cells should be at about 42V when fully charged) which is a bit strange but might be related to the fact the pack was at a low SOC for several weeks. The charger outputs 42.1V which is perfect. Why would the charger show the green light though, indicating that the battery is fully charged?
Anyway, off I went yesterday. Bike tyres are quite soft. Brake pads are slightly hitting the rims. Bike is old and heavy and my 100kg doesn't help either. And it was quite stormy. With one pack the controller cut power after about 20s at full throttle. Must be the load temporarily lowering the pack voltage below the threshold. Still max speed with the wind was about 35km/h. With half throttle or throttle on / off (a bit like pulse and glide) I managed 5km range. Bike struggled up any small hill. Battery was 34V when I came home, had to pedal the last few hundred meters as the battery was dead, didn't pedal at all up to then
Today I parallelled both little packs (under €45 each shipped
), pumped up the tyres to 30PSI and it was a completely different ballgame. Started again at 40.2V. Did the full 5km circuit at almost constant max throttle and with no wind the bike manages a constant top speed of a bit over 30km/h. No issues at all and came home with a battery just under 39V, didn't pedal at all
So if I can get the pack back to charging to full, it should be able to do my 10km commute no bother flying along at full throttle 30km/h. It probably even can do that if the battery doesn't go up again0 -
So I hooked up a single 4Ah battery pack after I charged it. Only went to 40.2V (for those of you who don't know a 10S pack of 3.7V nominal 18650 cells should be at about 42V when fully charged) which is a bit strange but might be related to the fact the pack was at a low SOC for several weeks. The charger outputs 42.1V which is perfect. Why would the charger show the green light though, indicating that the battery is fully charged?/QUOTE]
Those packs have BMS ? could be that they didn't fully balance. Usually the bleed current for the BMS is quite low and can take a very long time to balance depending on how off they are.
IF you can manage not to get the packs too low then they should not get much out of balance.
Today I parallelled both little packs (under €45 each shipped), pumped up the tyres to 30PSI and it was a completely different ballgame. Started again at 40.2V. Did the full 5km circuit at almost constant max throttle and with no wind the bike manages a constant top speed of a bit over 30km/h. No issues at all and came home with a battery just under 39V, didn't pedal at all
So if I can get the pack back to charging to full, it should be able to do my 10km commute no bother flying along at full throttle 30km/h. It probably even can do that if the battery doesn't go up again
Hard tyres make a difference, I remember when I ditched the nountain bike tyres and got Continental sport contacts and pumped them to 90 Psi the difference was amazing, the peddling efficiency was amazing, of course on country roads you need a decent saddle with that kind of tyre pressure.......
You should sell that motor when you want to upgrade and get an 8T Mac kit.
Don't forget that it's often the case that battery C rates are over rates so if your pack is getting very warm and you notice lots of voltage sag then it's definitely not a 3 C battery.
And the cold will also make it sluggish in winter if stored in the shed, get an electric blanket and keep them wrapped up at night !
I reckon that battery will have a very short life.......0 -
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Deleted User wrote: »Those packs have BMS ? could be that they didn't fully balance. Usually the bleed current for the BMS is quite low and can take a very long time to balance depending on how off they are.
IF you can manage not to get the packs too low then they should not get much out of balance.
Don't forget that it's often the case that battery C rates are over rates so if your pack is getting very warm and you notice lots of voltage sag then it's definitely not a 3 C battery.
Yes they have a BMS:
Linky
If you think about it, one pack just didn't make sense. The motor is 500W and the battery pack size = 4Ah
Pack voltage is say 40V. That means the current at max motor settings is 12.5A so you are talking well over 3C. I'm actually surprised that tiny battery gave that to me (for about 20-30s)
Much better off with the two packs in parallel, which brings the max C rating to well under 2C. It could provide this constantly for my 5km loop
Hope they recover though, at their current 40.3V, they are only at about 80% SOC. That said I actually don't know if they would go all the way up to 42V as I have never tested this and they arrived only 60% or so charged...
But maybe that's a good thing. I shouldn't run them down again like I did though.
Why do you think they will have a short life? Because they were cheap?
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I reckon that must be it Joe. Probably my own fault in hooking the single packs up and discharging them too quickly (leading to some cells voltages going below others)
Still with 40.3V and the packs now in parallel (8Ah) it is more than plenty for my range needs. And unlike an EV, should the batteries be completely depleted I can still peddle home 0 -
I reckon that must be it Joe. Probably my own fault in hooking the single packs up and discharging them too quickly (leading to some cells voltages going below others)
Still with 40.3V and the packs now in parallel (8Ah) it is more than plenty for my range needs. And unlike an EV, should the batteries be completely depleted I can still peddle home
It may not be your fault. Sometime batteries that are on offer (cheap) have been in storage for a while and may already be out of balance when sold. Batteries are best fresh.
A battery that is cutting off at 40.3 will have a substantial loss of capacity. Under normal circumstances, the 36v battery is charged at constant current (e.g 2amps) until it reaches 42 v. The battery continues to be charged at 42v until the charging current drops to a fraction of an amp. This is often called the constant voltage or saturation phase. A battery which terminates its charge at 40.3V due to BMS shut off will not reach the constant voltage/saturation stage and will lose a lot of capacity.0 -
I wouldn't call it a substantial loss of capacity though. Roughly still at 80%
Not too bad for a 36V 8Ah pack that I bought for €90 including shipping
You're right that the batteries more than likely have been sitting in storage for some time. These are the packs that went into the hoverboards / electric scooters that were the big Christmas present hit last year and the year before. It's (just) more profitable to sell these overstock packs as is than to dismantle them and sell individual cells I guess.0 -
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I had a look at the prices on his website. He knows how to charge.
My packs are fine for my needs. Cheap and cheerful!
They all know how to charge and you get what you pay for and his reputation on endless sphere is excellent.
You pay for good quality or a bit less for not so good quality.
Besides, once you get your head around using LiPo, you'll never look back.
https://hobbyking.com/en_us/turnigy-5000mah-6s-20c-lipo-pack-w-xt-90.html
4 of these for 44v and 10 ah would cost 173 euro's ex shipping.
20 C discharge 2 C charge, charge it at 20 amps in 30 mins lol
Bunch of 30 amp anderson connectors for dead easy connecting.0 -
Update: for the craic I put a power meter between battery and controller. Turns out my 500W motor actually produces nearly 1kW :eek:
No wonder that tiny battery pack could only hack that for 15-20s, that was discharging at 23A or nearly 6C :eek: :eek: :eek:
Bike is great for taking the dog out for some serious exercise. She's lost some weight and she is well fit now (I'm not) 0 -
Update: for the craic I put a power meter between battery and controller. Turns out my 500W motor actually produces nearly 1kW :eek:
No wonder that tiny battery pack could only hack that for 15-20s, that was discharging at 23A or nearly 6C :eek: :eek: :eek:
Bike is great for taking the dog out for some serious exercise. She's lost some weight and she is well fit now (I'm not)
No way you don't take the dog for a walk with you on the bike ? :eek:
The motor isn't producing 1 Kw , that's what's being pulled from the battery. The motor simulator is the place to go to find out what maybe going to the motor.
Now imagine 5 Kw ? :eek: 0 -
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Deleted User wrote: »No way you don't take the dog for a walk with you on the bike ? :eek:
Dog off the lead by the canal or in the park.Deleted User wrote: »The motor isn't producing 1 Kw , that's what's being pulled from the battery.
So where is that 1kW going then if not to the motor?
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Dog off the lead by the canal or in the park.
So where is that 1kW going then if not to the motor?
You're probably loosing about 30% due to inefficiency. But go to the ebikes.ca motor simulator, it's pretty cool to mess around with.
Actually I'll play around with it, so your setup is what 20 amp controller and 36 Volts ?0 -
Crap, I can't remember what wind that motor is, so many motors these days but I remember the Chaps on endless-sphere knew the motor specs and compared it to a nine-continent and I can't remember which one.
But that's actually about 828 watts, 36V x 23 amps 0 -
Deleted User wrote: »You're probably loosing about 30% due to inefficiency. But go to the ebikes.ca motor simulator, it's pretty cool to mess around with.
Actually I'll play around with it, so your setup is what 20 amp controller and 36 Volts ?
I very much doubt there is 30% loss to inefficiency. But let's say 20% loss (I put a few figures into that site you mention and all combos I tried had 80% or higher efficiency). I saw 930W, so that effectively means 750W which is less than 20A controller * 40V battery, so well in spec.
Interestingly that is enough to give me a Vmax on the flat of 30-35km/h but it would not propel me up a long steep hill. I guess you would need 2-3kW for that 0 -
I very much doubt there is 30% loss to inefficiency. But let's say 20% loss (I put a few figures into that site you mention and all combos I tried had 80% or higher efficiency). I saw 930W, so that effectively means 750W which is less than 20A controller * 40V battery, so well in spec.
Interestingly that is enough to give me a Vmax on the flat of 30-35km/h but it would not propel me up a long steep hill. I guess you would need 2-3kW for that
Well it's not going to be accurate because we need to know the actual motor specs, lots of the Chinese motors are clones but we need to know the windings etc but yes you could loose 30 % depending on terrain too , geared hubs are more efficient but on hills you could loose much more than 30%.0 -
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