mixed chemistry question

[tftrike]

I need some technical help.
I carry 2 battery packs on my trike. I am a redundancy freak and many times I cannot depend on breakdown help and am disabled and can't walk very far. I have a 12ah sla and a 10 ah nihyd onboard.For 95% of my riding, I have found 36 volts to be adequate. However, on one trip that I ride on there is about a mile of steep hills that bog my trike down. It is possible that going to 48 volts might solve my problem. My question is, can I connect just 1 of the 12 volt sla cells with a switch to my nimyd to obtain the 48 volts. Or in the interests of cell balancing should I parallel all three cells and put a switch on that? If the single brick idea will work ,should I recharge the brick by itself or in series with the rest of pack after use? I don't think that my controller would take 72 volts so I don't want to series connect the two packs. Thanks

[fechter]

Putting the 3 SLA in parallel will prevent any balance problems, but that's a lot of wiring (more prone to problems).

The single brick should work, but you would not want to just put it back in series with the others for charging.

If you use the single brick, you should charge it with a separate 12v charger.