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General Discussion / Re: Questions - Charging 2 x 48V Battery Packs
« on: October 13, 2009, 09:07:49 AM »
I am new to the Forum and looks like this thread has a battery expert..so maybe you can provide me some guidance.
My e-Bike uses 4 x 12V 20ah SLA batteries in series to provide 48V to a 500 watt motor. Charging is with one 48V charger. Some of us were looking at (and have done some testing) on adding an additional battery pack of 4 x 12V 9ah batteries. (We have physical room for these under the seat) connected in parallel with the larger 20ah pack. Preliminary testing indicates a more stable delivery of amps to the motor plus longer range before recharging.
One of our group thinks that:
•When the bike is not being used (and the batts are partly discharged), the 2 packs should not remain inter-connected as the larger one will discharge into the smaller one at an uncontrolled rate, potentially damaging the smaller pack. For this reason, he is planning to install some 25A diodes between the two packs to prevent this.
•The two packs need to be disconnected from each other and charged (using the 48V charger) separately and independently as charging through the main pack with both connected will cause the charger to prematurely detect full voltage and shut down early, or perhaps overcharge the smaller pack.
I personally am not convinced either of these concerns is valid, but don't want to destroy any SLA battery packs testing it. Would anyone have an opinion/experience on this?
My e-Bike uses 4 x 12V 20ah SLA batteries in series to provide 48V to a 500 watt motor. Charging is with one 48V charger. Some of us were looking at (and have done some testing) on adding an additional battery pack of 4 x 12V 9ah batteries. (We have physical room for these under the seat) connected in parallel with the larger 20ah pack. Preliminary testing indicates a more stable delivery of amps to the motor plus longer range before recharging.
One of our group thinks that:
•When the bike is not being used (and the batts are partly discharged), the 2 packs should not remain inter-connected as the larger one will discharge into the smaller one at an uncontrolled rate, potentially damaging the smaller pack. For this reason, he is planning to install some 25A diodes between the two packs to prevent this.
•The two packs need to be disconnected from each other and charged (using the 48V charger) separately and independently as charging through the main pack with both connected will cause the charger to prematurely detect full voltage and shut down early, or perhaps overcharge the smaller pack.
I personally am not convinced either of these concerns is valid, but don't want to destroy any SLA battery packs testing it. Would anyone have an opinion/experience on this?