Increased battery capacity

[peerjay56]

I've just got a spare battery pack for my bike, which I have wired in to the controller, so that when the first (main) battery goes flat, I can simply switch it off and switch on the spare with it's key. All seems to work OK.
Now, both batteries are nominal 37v 10Ah, although not necessarily the same cells/chemistry. Would there be any harm in having both batteries on at the same time? Indeed, would that prove a better way to run with the extra battery? I know it would still only be a nominal 37v, but would the theoretical 20Ah provide more 'guts' under load, or would it make not a blind bit of difference?
Interested to hear some considered views. Thanks.

 

[Alan Quay]

It should be ok, assuming they are of similar capacity, and you start with them both in the same state of charge. I'm not sure how the BMS's would behave in other states (it might be ok though).

If your limit is battery current at present, then you will see an increase. Obviously two batts in parallel can supply double the current of one.

 

[Deleted member 4366]

It'll work OK and it'll provide a bit more power like that. Make sure that they're at the same voltage when you connect them, and disconnect them before charging each otherwise one will charge the other through the discharge leads.

 

[peerjay56]

Until I'm happy about the capacities of each, I'm running them individually. It's interesting that when using the original cyclotricity pack, if I get down to one 1 bar on the indicator, I know that battery cutoff is imminent. The new battery yesterday carried on supplying power even after all bars disappeared from the display. I got home before it cut out, and measuring the voltage showed it was at 32.0v. Very different characteristics for each, it would appear. I now have a GT wattmeter, which I need to fit and do some actual measurement.