How long can a Rad battery last? A long time.

[DickB]

I tested the Standard Battery on my Rover 5 when it was new, and now again after 5+ years and about 5000 miles on this battery. (I have 8700 miles on the bike, but have two batteries which I occasionally swap.) The battery has not noticeably degraded.

The test consists of my riding the bike throttle only fully open on level roads until it virtually quits. I stop every two miles and measure the battery voltage after 60 seconds. The battery is still performing like new, except for the last few miles.

I ride 12 miles most every day, and charge to 80% after every ride. The bike lives in my garage in Florida, so it is subject to 80+ degrees (often 90+) nearly all year. I have a meter on my charger that shows that the charger adds about 110 Ah on a charge, which is about 1/6th capacity. So I'm doing the equivalent of one full charge every 6 days. That works out to about 335 full charge cycles. Rad advertised 800 cycles on the battery when I bought the bike; the cell manufacturers say 500 cycles.

[DickB]

Regarding charging to 80% vs 100%, here is the best data that I have.

I bought a used second battery some time ago. The power connector had overheated and melted. The owner couldn't repair it; so I bought it as a spare and replaced the bad connector. The owner said she had put about 4000 miles on it, which I estimate to be no more than 150 cycles, maybe less. I just tested that battery today.

In the chart, blue is my original battery new, and green is that battery after over 300 charge cycles to 80%. Red is the second-hand battery that was charged maybe 100 - 150 cycles to 100%. Remember we are talking about complete charge cycles.

Most consider the battery to be discharged at 42V, where power drops off. We can see that at 42V the 100% charged battery has lost about 2 miles in distance capability, or about 10%. Not huge, but measurable. It will likely degrade more with additional charge cycles to 100%. I would guess at 300 cycles the loss might be about 20%.

Remember this test is at full throttle with a maximum distance of 20 miles. If you use PAS and pedal 40 miles on a charge, you would likely lose 4 miles.

It is noteworthy that power is not reduced, only capacity or distance. If you don't take long rides, you would never notice the difference.

[Ddaybc]

That's excellent DickB. Good data.
Thank you.