Battery health indicator

[Chuck E. Cheese]

I'm planning a long trip this fall on my ST2 and wanted a second battery. A friend who is a grad student in the engineering department at a local university has built dozens of ebike batteries and has experience with and access to access to their battery welding and assembly equipment. I bought a used "broken or for parts" 814Wh Stromer battery on ebay for $175 with the idea of having my friend rebuild it. As it turns out, it does work! It certainly isn't fresh, but I spent a half hour or so with the new battery riding with all the lights on at the highest assist, keeping speed up at 28-30 MPH as much as posssible. I got 11.9 miles at the 50% mark. By my reckoning, at around 22Wh/mile the "new" ebay battery has about 65% of the capacity of the one that came with the bike new. According to the Omni app, it's in "Very Good" condition. That's the same term it uses for the one that's only 6 weeks old. Is there a way to accurately gauge the health of the battery? When a battery drops as low as the ebay one should I expect it to die altogether soon, or can I trust it for my upcoming trip? We plan to ride ~70 miles/ day, and unless the ebay battery totally craps out, I should be able to achieve that through judicious use of assistance. Or should I just order new cells and have my friend rebuild it? He's never rebuilt a Stromer battery before, and even though the technology is similar among all brands, he suggested I ask here if anyone has any recommendations. Thanks in advance!

 

[opimax]

I didnt see this, i dont have an answer. I do have plenty of cases for Stromer batteries but nothing local in DC area I know of that can work on these. I also have the same thought of the battery condition, a little more actual info would be useful, number of charges would be nice too.

I would beat the battery a little (use it hard) and see how it performs, then decide if you like the range and reliability then make the decision.

if this is too late and you went on your trip , what did you do?

 

[Chuck E. Cheese]

I didnt see this, i dont have an answer. I do have plenty of cases for Stromer batteries but nothing local in DC area I know of that can work on these. I also have the same thought of the battery condition, a little more actual info would be useful, number of charges would be nice too.

I would beat the battery a little (use it hard) and see how it performs, then decide if you like the range and reliability then make the decision.

if this is too late and you went on your trip , what did you do?

I haven't done the trip yet. A friend and I are riding from Northern Vermont to Portland, Me. in September.

I put the Ebay battery in to regular rotation with the battery that came with the bike. It definitely doesn't have the range of the new one, but it's better than I first assessed. It's closer to about 75-80% of the new one. For $175 plus $29 for a new battery case handle from Stromer (the original was broken which kept the battery door on the bike from locking) it was a helluva deal. It will help the new one last that much longer and should be perfect for the trip to Maine.

 

[opimax]

I hope it is a great trip. Where is the person located willing to refresh Stromer batteries? I am in Dc area may be worth the drive...

 

[Chuck E. Cheese]

The friend who has offered to help me is a graduate student at the University of Vermont. While he has access to the lab it's not something he offers as a public service. He needs permission from the Dean and his advisor. Here is a company that offers the service commercially who you might contact: https://ebikemarketplace.com/products/stromer-batteries