for
3,3Ah - 4,2Ah, a single cell weights 62g - 66g
and a single cell costs 8Euro - 10Euro
so, why do they only hold for 50-100cycles..
because we stress the cells A LOT in our models.. (in the most hard case (hotliners) we empty a NiMh cell in less than 80 seconds !!
(5 second bursts of 250A current out of a 3,3Ah NIMH-cell !!)
thats also the only case were Lipos and LiIon can NOT keep up... emptying in 80seconds would ruin that cells
so, for my experience an electric bike is a "low power" application..
in a e-bike you want some runtime
so the cells are not emptied in less than 30min which is "low power" in our rc-use minde..
again my nice diagramm i made last weekend
use of FePO4
thats similar to the power-use in a E-bike...
800Watt Peak
245Watt average power
BUT with the difference, that this battery was not a 4kg heavy battery, but only 0.295kg light (295g) battery !
i spoke with an tech-engineer from A123-racing (they make the A123 FePO4-cells) and showd him this diagramm - he told me, within that kind of use, i can not expect 1000cycles with the FePO4, but more like around 300cycles
in a E-bike you use about the same power.. but you will also use a battery with about 10-15times as much weight/size/capacity
==> for that, the battery will have to deliver about 10-15times lower current than in my application
so - flecc - you realy don´t have to worry, that the batteries can not give you substain current..
(yes, the peaks in my diagramm are only about 1sec. long
but in your bike with a 4kg heavy battery your 1000Watt substain (lets say 5min ?) peak will only be 6A !!! for each cell...
when you look at my diagramm: the lowest current during discharge i had was 12A... the higest 90A) 6A is like nothing for the cells..
in a car/bike you will at least want 30min+ runtime..
so high current (for the single cell) i think rc-applications are lot more stress
(discharge: in less than 80sec. for the extreme freaks
discharge: in less than 3min for power-flying
discharge in less than 6min for normal sport-flying
discharge in 10min+ for the old-age pensioner-style flying
so - i have nothing against NiMh... for your application (no balancer needed, compatible charger already in ownership, batts fit perfect in the case from the bike-battery-mount, ...) its for now maybe the best solution
i have also used the best-quality NiMh around (as said: 10 Euro a single 3,3Ah-cell ==> a bike-battery with 10Ah and 36Volt would cost 900Euro when made from this cells)
so i know, what VERY good NiMh cells can do !
(a 16cell 4200mAh NIMh competition-pack worth 220Euro and weighing
1100g can put out 4000Watt for 5sec-burst !!!
after use, it is around 100°C hot !! and you have to remove it from your model with a pincer and imidiatly cool it with fan otherwise the cells can explode !) so - i know a little bit about high current and stressing batteries *lol*
the NiMh we use in our helis (which fail after 50-100cycles) haveEdit: I just visited Lidl-shop. They had 4,5 AH NiMh cells 2 euro/piece
3,3Ah - 4,2Ah, a single cell weights 62g - 66g
and a single cell costs 8Euro - 10Euro
so, why do they only hold for 50-100cycles..
because we stress the cells A LOT in our models.. (in the most hard case (hotliners) we empty a NiMh cell in less than 80 seconds !!
(5 second bursts of 250A current out of a 3,3Ah NIMH-cell !!)
thats also the only case were Lipos and LiIon can NOT keep up... emptying in 80seconds would ruin that cells
so, for my experience an electric bike is a "low power" application..
in a e-bike you want some runtime
so the cells are not emptied in less than 30min which is "low power" in our rc-use minde..
again my nice diagramm i made last weekend
use of FePO4
thats similar to the power-use in a E-bike...
800Watt Peak
245Watt average power
BUT with the difference, that this battery was not a 4kg heavy battery, but only 0.295kg light (295g) battery !
i spoke with an tech-engineer from A123-racing (they make the A123 FePO4-cells) and showd him this diagramm - he told me, within that kind of use, i can not expect 1000cycles with the FePO4, but more like around 300cycles
in a E-bike you use about the same power.. but you will also use a battery with about 10-15times as much weight/size/capacity
==> for that, the battery will have to deliver about 10-15times lower current than in my application
so - flecc - you realy don´t have to worry, that the batteries can not give you substain current..
(yes, the peaks in my diagramm are only about 1sec. long
but in your bike with a 4kg heavy battery your 1000Watt substain (lets say 5min ?) peak will only be 6A !!! for each cell...
when you look at my diagramm: the lowest current during discharge i had was 12A... the higest 90A) 6A is like nothing for the cells..
i don´t think so (When it comes to high-current)high current capacity batteries. Hence vehicles being at the top of that stack
in a car/bike you will at least want 30min+ runtime..
so high current (for the single cell) i think rc-applications are lot more stress
(discharge: in less than 80sec. for the extreme freaks
discharge: in less than 3min for power-flying
discharge in less than 6min for normal sport-flying
discharge in 10min+ for the old-age pensioner-style flying
so - i have nothing against NiMh... for your application (no balancer needed, compatible charger already in ownership, batts fit perfect in the case from the bike-battery-mount, ...) its for now maybe the best solution
i have also used the best-quality NiMh around (as said: 10 Euro a single 3,3Ah-cell ==> a bike-battery with 10Ah and 36Volt would cost 900Euro when made from this cells)
so i know, what VERY good NiMh cells can do !
(a 16cell 4200mAh NIMh competition-pack worth 220Euro and weighing
1100g can put out 4000Watt for 5sec-burst !!!
after use, it is around 100°C hot !! and you have to remove it from your model with a pincer and imidiatly cool it with fan otherwise the cells can explode !) so - i know a little bit about high current and stressing batteries *lol*