trialspower2
100 W
- Joined
- Dec 31, 2016
- Messages
- 108
I have been building an electric trials bike for the last couple of years with my own controller. Now I have it up and running I am looking at getting all the final setup sorted so I can finish it.
Here in the UK a normal competition event will cover well under 10 miles with around 40 sections. I believe a 1.200kwh battery will be suitable. I want peak current of around 350A at 75v, without to much performance loss over the discharge of the battery. Looking around, I feel lipo is the only option for this as weight is critical.
There are also some long distance events, where the petrol bikes stop to fill up with fuel. I want to be the first to finish such events on electric power. An example of this is the scott trial @ 80 miles.
I thought an additional li-ion battery pack might be the best solution which can be charged at fuel stops. But as these batteries are more suited to low discharge rates and have a large voltage drop over the discharge cycle I was thinking how to get the best out of them. So I came up with this;
Connect enough in series so when at 2.5 volts they still make 75v.
Build a step down converter/ charger device which pumps say 20A charge into the main lipo pack constantly. This will cut off when the lipos are say 4.1v per cell. But when the lipos are under this supply 20A to the system constantly. If the bikes using over 20A, the lipos will be getting flatter, under 20a the lipo's will be charging. I would have this pack weigh around 10kg. This will allow me to use 3.5Ah 18650 batteries and discharge them under 1C getting the maximum power out of them.
There will be losses in the step down, but I dont think these will be much. The lipos might not like it, but its only for the odd event. As long as they are balance charged after and they probabily wont charge much over 1C at 20a on the bike. I am technically carrying more batteries this way, but it gives me extra range in the event I need it. The two packs will give at least 3.5kwh, thats got to be good for 30-40 I think. On the road the bike uses around 2.4kw @ 30 mph and 4kw @ 40mph.
Thoughts?
Here in the UK a normal competition event will cover well under 10 miles with around 40 sections. I believe a 1.200kwh battery will be suitable. I want peak current of around 350A at 75v, without to much performance loss over the discharge of the battery. Looking around, I feel lipo is the only option for this as weight is critical.
There are also some long distance events, where the petrol bikes stop to fill up with fuel. I want to be the first to finish such events on electric power. An example of this is the scott trial @ 80 miles.
I thought an additional li-ion battery pack might be the best solution which can be charged at fuel stops. But as these batteries are more suited to low discharge rates and have a large voltage drop over the discharge cycle I was thinking how to get the best out of them. So I came up with this;
Connect enough in series so when at 2.5 volts they still make 75v.
Build a step down converter/ charger device which pumps say 20A charge into the main lipo pack constantly. This will cut off when the lipos are say 4.1v per cell. But when the lipos are under this supply 20A to the system constantly. If the bikes using over 20A, the lipos will be getting flatter, under 20a the lipo's will be charging. I would have this pack weigh around 10kg. This will allow me to use 3.5Ah 18650 batteries and discharge them under 1C getting the maximum power out of them.
There will be losses in the step down, but I dont think these will be much. The lipos might not like it, but its only for the odd event. As long as they are balance charged after and they probabily wont charge much over 1C at 20a on the bike. I am technically carrying more batteries this way, but it gives me extra range in the event I need it. The two packs will give at least 3.5kwh, thats got to be good for 30-40 I think. On the road the bike uses around 2.4kw @ 30 mph and 4kw @ 40mph.
Thoughts?
