Help with Schwinn Ecotour 2009.

[Burton339]

Hi there, after scouring the web I saw a post from 2010 on this message board. Controller and Battery compatibility question.

Technology has advanced obviously so I am seeing what my options are (and thank you for even reading this!). My wife recently purchased this bike at an estate, only to find out that both batteries (and cases) are missing, The original batteries were 24V 8Ah NiCad batteries. The original battery packs had brass contacts on the bottom side of the case, which connected to a tension button-style terminal. The controller unit is a 24v 35A, and the motor is (I'm guessing) a 24volt 450-watt motor. I see online shops offering replacement units, but they are expensive and the shipping will be crazy to Canada. Can I go a different route with Lithium?

Many thanks!

 

[amberwolf]

I can't think of a reason it wouldn't work with a Lithium battery instead of NiCd, as long as you use the charger that comes with the new battery, and not any charger that might have come with the bikes.

Before you go buy one, I recommend testing the bikes to at least see if they turn on and run the motor with the wheel off the ground, using a couple of 12v lead-acid batteries (like the starter batteries in cars) in series.



The battery will need to be capable of >40A at least for short bursts, as a 35A controller could "ask" for more than that 35A during initial motor start under load--some of the brushed motor controllers may draw more than twice that for a moment at start.

NiCd could take that momentarily though it would sag greatly in voltage, but since Lithium usually has a BMS (recommended) that has electronics with limitations on what they can handle without failing, they have to be built and specified to handle that kind of short term current, and longer if possible.

The battery will also need to be in the same voltage range from full to empty as the NiCd would've been. Nicd would be 20s (20 series cells) of 1.2v nominal to get 24v. Usually empty is around 1v/cell, or 20v for the pack, and full is around 1.4v/cell, or 28v. That's about the same range as most other 24v packs, including lead (SLA) and lithium of various types.

You're probably better off with a Li-Ion / Li-Po pack vs LFP / LiFePO4, as the latter often has lower C-rate cells (lower current capability), but it depends on the specific cells used in any particular pack.

Cheap packs are...cheap. Ebay, Amazon, Aliexpress, Alibaba, etc., are usually poor places to buy such things, as most of what you find there is not very good, and some of it is literal recycled garbage, but the ads may look good. If it seems too cheap to be true, well, it probably is. If you see the "same" pack for $500 vs $100, the $100 pack is probably a bad deal.


You might be able to find empty casings for the original batteries on ebay and the like (or even old dead batteries you can strip for the casing/connector), but it is probably easier just to bypass the original connection and put a matching connector for whatever battery you end up buying on there.