Charging pattern

[anotherkiwi]

I'm buying more r/c Lipo

With Lipo the 80% rule really does increase pack life so a 20 Ah battery provides in reality about 15 Ah usable capacity. Discharge rate of 1C or 2C is well under the 10C available these things make the bike pull like a train on the hills!

For my longer range, on road use the disadvantages of Lipo are lesser than the advantages and as a bonus the packs are so cheap (when bought at sale prices) they are very economical even if they only last 300 or 400 cycles which in my case would be a couple of years. I calculated my pack amortisation for one year only, or 100, cycles, and even then I am at 0.03 € /km!!! With my public transport card it costs 0.06 € a km...

 

[flecc]

With Lipo the 80% rule really does increase pack life so a 20 Ah battery provides in reality about 15 Ah usable capacity. Discharge rate of 1C or 2C is well under the 10C available these things make the bike pull like a train on the hills!

With no BMS to do it, these really do benefit from user limitation of upper charge extreme of course. They're also good for performance as you say, but at the cost of much shorter lives than our regular managed batteries. No r/c lipo will power an e-bike over five full years of use in the way a few of our best systems are capable of.
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[anotherkiwi]

Which is what I said in the second paragraph. I never expected the r/c packs to last more than a year and that was factored into my spreadsheet.

I just went out for a ride and I thought I would test without the max speed limit of the motor and Lipo. The motor works as advertised drawing current up to about 33-34 km/h. The ride was enjoyable comforting me in my idea that on the open road a 35 km/h cut off is a better option than 25 km/h.

On return the wires were warm (35°-40°C warm) coming out of the Watt meter but battery and motor cool. I don't need to touch the controller to know that it is very hot. In the 4S pack I have a cell that is imbalanced by 0.02 V, in the 6S pack all the cells are within 0.01 V.

The unspoken problem with a Lipo pack like mine placed in a pannier bag and the Lipo alarm plugged means that in these troubled times you can't go anywhere near a public place with bag searching going on... It looks like a couple of C4 bricks with detonator.

 

[Hillbilly]

As someone very new to electric bikes I am a bit surprised at the cost and variety of their batteries. Is there a second hand market and any flexibility in interchangeability. Also has any looked at the feasibility of using somehow the modules from scrapped electric cars as I understand these are becoming available at about £10 each. They are about 0.5kWh capacity but at similar weight and volume as my bike battery which I think is just under 0.4 kWh so a bit more efficient and maybe longer lasting. I presume a fair bit of work in creating controllers and adaptors would be needed but there could be a huge supply of these in the next few years. Their spec is shown below
http://www.eco-aesc-lb.com/en/product/liion_ev/

 

[flecc]

As someone very new to electric bikes I am a bit surprised at the cost and variety of their batteries. Is there a second hand market and any flexibility in interchangeability. Also has any looked at the feasibility of using somehow the modules from scrapped electric cars as I understand these are becoming available at about £10 each. They are about 0.5kWh capacity but at similar weight and volume as my bike battery which I think is just under 0.4 kWh so a bit more efficient and maybe longer lasting. I presume a fair bit of work in creating controllers and adaptors would be needed but there could be a huge supply of these in the next few years. Their spec is shown below
http://www.eco-aesc-lb.com/en/product/liion_ev/

E-bike batteries have a tough time due to their size and weight restriction, meaning the cells second hand are often near to or at the end of life. Many only scrape to two years, though the best and most expensive examples can get into a fifth year in moderate demand systems.

The car ones most likely to be appearing about now are from the Nissan Leaf after five years from being the first of this type on the road.
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[Hillbilly]

...
The car ones most likely to be appearing about now are from the Nissan Leaf after five years from being the first of this type on the road.
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Thanks - Yes no point in going to the bother if the module is defunct but I'm talking about all the good quality tested modules becoming available ( maybe off a new crashed car). I suppose I'm wondering whether there is an option of having a spare different battery that could be made to work that might extend the life of the original. If for instance you take this ebike could you remove its original battery when it's flat and devise a method of putting the leaf module on the back with an adaptor/controller that mates with the existing cables and drives the motor.

 

[flecc]

Very tricky. One module at 3.8 kilos is an acceptable weight, but it would only deliver 7.5 volts.

Five modules in series would give a compatible 37.5 volts nominal, but the 19 kilos weight would be crippling.

Breaking the modules down to cells and using 10 in e-bike series fashion for the nominal 36 volts would still weigh 8 kilos, still too heavy.

This long-life car cell technology isn't really suitable. The 18650 cells that we use in the best e-bike batteries and Tesla use in their cars is the best approach.
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[anotherkiwi]

I came in on a tight budget but I didn't try and save on battery cell quality. This meant I had to give up on capacity as a compromise. I don't regret taking that road, there are so many stories of people frustrated with low quality 18650 cells that give neither enough ooomph nor enough range after a very short period of time. The cost "savings" end out to be false, you (almost) always get what you pay for.

Second hand cells from laptops however are a good option for used cells. Computers don't put the same load on cells that bikes or cars do. When a battery pack goes bad it is often a couple of cells dragging the other still good cells down.