Should I be surprised?

[peterjd]

Just as an experiment I connected up my nominal 28.8 V (10S2P) battery to my modified Swytch Mk1 bike which I usually run on variety of nominal 36V batteries (Yose 10.8Ah and Bosch tool 2.6Ah). The display came on showing as expected a low battery voltage. What surprised me was the motor functioned quite well on 'walk-assist'? Since it was only a 'lash-up', I didn't try any of the cycling levels (and I don't really want to). But in my quest for ever lighter, just enough, assistance on my old touring bike, I am going to disconnect my Swytch front wheel and refit the lightweight original wheel and put the simple friction drive (3 phase motor) I have on the rear wheel but using the Swytch controller and the 28.8V battery. What my ideal for summer fine weather short distance cycling is to just have enough low weight assistance to enjoy local and utility cycling. I'll let you know in due course how it works out. Peter

 

[lenny]

But in my quest for ever lighter

 

[saneagle]

Just as an experiment I connected up my nominal 28.8 V (10S2P) battery to my modified Swytch Mk1 bike which I usually run on variety of nominal 36V batteries (Yose 10.8Ah and Bosch tool 2.6Ah). The display came on showing as expected a low battery voltage. What surprised me was the motor functioned quite well on 'walk-assist'? Since it was only a 'lash-up', I didn't try any of the cycling levels (and I don't really want to). But in my quest for ever lighter, just enough, assistance on my old touring bike, I am going to disconnect my Swytch front wheel and refit the lightweight original wheel and put the simple friction drive (3 phase motor) I have on the rear wheel but using the Swytch controller and the 28.8V battery. What my ideal for summer fine weather short distance cycling is to just have enough low weight assistance to enjoy local and utility cycling. I'll let you know in due course how it works out. Peter

10s2p is 36v, not 28.8v unless you have lithium titanate cells.

 

[peterjd]

More sad evidence of aging methinks. 8s2p of course. Lithium titanate sounds expensive - I'm a cheapskate using mostly recovered 18650 2500mA cells. Thanks Peter

 

[saneagle]

More sad evidence of aging methinks. 8s2p of course. Lithium titanate sounds expensive - I'm a cheapskate using mostly recovered 18650 2500mA cells. Thanks Peter

8S2P of recycled cells will most likely be terrible. It would be bad enough with top spec new cells.

 

[peterjd]

I'll let you know - I am looking for some but quite minimal assistance on a pretty light bike. Peter
PS The said recovered batteries seem in pretty good nick in terms of tested capacity

 

[saneagle]

I'll let you know - I am looking for some but quite minimal assistance on a pretty light bike. Peter
PS The said recovered batteries seem in pretty good nick in terms of tested capacity

What does that mean?
What cells are they?
What current can they give?
What's their internal resistance?

 

[peterjd]

I fear we are different 'animals' saneagle. I love experimenting but with no engineering background, that tends to be empirical. I also get enjoyment from prolonging the life of bits of technology which often these days has obsolescence built in. In this case it might also have the additional benefit of prolonging the life /'marbles' of this obsolescent user?

 

[saneagle]

I fear we are different 'animals' saneagle. I love experimenting but with no engineering background, that tends to be empirical. I also get enjoyment from prolonging the life of bits of technology which often these days has obsolescence built in. In this case it might also have the additional benefit of prolonging the life /'marbles' of this obsolescent user?

Try it by all means, but, generally, recycled batteries only work in large packs, where each cell only has to give small current. With only 2P, there are only 2 cells to share the current, so they're driven twice as hard as in a 4P pack. Used cells have high internal resistance, which makes them very saggy. Put the two together, and you get a saggy pack that can't deliver much power. Also, with a 7S pack you need 42% more current for the same power as a 10S, and nearly double the current of a 13S one. If I wanted to make a pack out of recycled cells, i'd go for 48v to keep the current low.

I'm speaking gnerally. Maybe your cells are top quality ones and hardly used.