Power output limited by battery?

[pn_day]

Hi all
I had my first long run on the conversion today to work and back (39 mile round trip, lots of hills). It went great, but I'm still seeing less power output than d8veh suggested I should

500W CST kit with S12S with soldered shunt and 20 Ah 36V shrink wrap battery from BMS battery.
Currently I'm only seeing a max power output of approx 850 W.

Could it be my battery being unable to supply any more current?
Battery is this one http://www.bmsbattery.com/36v/445-36v-15ah-lithium-ion-electric-bicycle-battery-pack.html

Are there any other things I should check?

Thanks
Phil

 

[Deleted member 4366]

No. If you draw too much current, the BMS will shut off completely. 850W is about 21 amps, so it's in the right ball-park for the S12S, which is supposed to be 23 amps. What are you measuring with?

You could try a couple of blobs of solder on the controller's shunt to increase the current a bit, although if your using the LCD to display power, you won't see any more because it uses the shunt's resistance to calculate the power. The shunt sits nicely behind the end-plate - ready for soldering.

If you have the LCD3, you might be able to change the current in the advanced setting parameters. You can set it anywhere up to +/- 5 amps as long as the S12S has the software to understand the command.

Did you have enough torque or do you need more?

 

[pn_day]

That's very interesting d8veh - I was reading the power using the LCD3 which would explain why the values were lower than I was expecting. I've already soldered the shunt that's why I was expecting to see more. If the LCD uses the shunt resistance prior to me adding more solder that would explain why the value has not gone up.

I'll delve into the advanced settings of the LCD3 to see what can be done.

The level of torque was fine - I was more concerned with power levels being lower than expected in case I was either demanding too much of the battery or losing power in some dodgy wiring.
Thanks again for the tips,
Phil

 

[Deleted member 4366]

Don't change anything else. You need to get an external wattmeter to check how much current you actually have. They only cost about £10. You connect it between the battery and controller. Lift the wheel off the ground and give it full throttle. Keeping the throttle on full, apply the back brake to slow the wheel down to nearly stalling. You'll see the current go up to its max as the wheel slows down.

 

[pn_day]

Thanks d8veh. I did actually order a wattmeter before I realised that the LCD3 shows power so never bothered connecting it in.
I'm now regretting having soldered all connections and covered with heat shrink. Ho hum. Out with the cable snips and solder sucker!

 

[Deleted member 4366]

You only have to put the same connectors on the wattmeter as you have on the battery to controller. Then you can have the wattmeter in or out of the circuit. That's why I standardise on Deans connectors. I always have a box-full.