Electric Bikes - Can I "Y" a Lifpo4 and a SLA battery together

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seanreit
09-07-08, 05:45 PM
And charge them together?

I have two 36v 15ah batteries, and since they are the same voltage I was considering Ying them together and running them on my Shwinn Scooter.

Thanks in advance for replies.

wernmax
09-07-08, 06:47 PM
Sure. Not to be a wiseass, but you "can" do anything, but it may be hard to assess the impact one may have on the other, in terms of charge/discharge cycles and overall life of each type of battery, being parallel and charged together.

One may suffer.
lfairban
09-07-08, 11:08 PM
Did you check the voltage of the two battery packs with a volt meter when fully charged? I thing 24V Li batteries are typically 27 V.

You might want to isolate the two battery pack by putting a diode on each when you use them to power the bike. The current flow will then only run out, not in. That will keep one battery from charging the other while you are using them.

As for charging, I would definitely recommend doing them separately. The charging requirements are different for the two types of batteries, IIRC.

cerewa
09-08-08, 08:08 AM
With a diode, it's fine to connect them (make sure you connect in parallel not series!).

Don't try to charge em together.

It's possible to wire them together for discharging without a diode but its ONLY safe if the voltages are within something like 0.03 volts.
wernmax
09-08-08, 05:13 PM
You might want to isolate the two battery pack by putting a diode on each when you use them to power the bike. The current flow will then only run out, not in. That will keep one battery from charging the other while you are using them.

As for charging, I would definitely recommend doing them separately. The charging requirements are different for the two types of batteries, IIRC.

Yes. What he says. ^^^

Diodes are like one way valves for electricity. You would put one on each battery, anode to positive, or I'd put one on the pack with the lowest "resting" voltage, to feed it's current into the circuit when the overall voltage sags.

You'd also have to "size" the diode to what your controller/motor can pull in amps, probably 30amps or so. The diode could even run hot, so beware, or get one with a heatsink on it.