Widewheel battery durability testing (revisited)

 I enjoy riding up and down the local mountain road. Its not only a very pleasant escape but its an excellent opportunity to test the battery and how its shaping up.

Now its worth while remembering that I bought this scoot in July 2019, which means its nearly 2 years old. In that time I have followed the following principles of battery handling

1. always fully charge it (some minor exceptions exist)
2. use the scoot soon (within a day) after charging
3. do not recharge if I know there is sufficient charge to make the trips I'm intending (frequently I do three or four 3km trips in a day)
4. it has been charged at 4Amps since I bought the fast charger in Jan 2020

So over the last (nearly) 2 years this equates to about 312 full charge cycles in its use.

The Test

Load testing of batteries is the best way to determine their health and their current capacity. Usually load testing is done on a bench with tools to map out the battery performance (represented by voltage) under a stated load. Since people are often confused by data that's about each cell (the 18650 cell) that comprises our packs I've annotated this graph with the voltage that a pack of 13 cells in series would show if tested this way

So yes, its normal for voltage to drop over the discharge of it. Importantly this is for a single cell, and discharged at 2Amps; as my pack has 6 cells in parallel for each cell to get 2A sucked from it the motors would need to be sucking 12A out of the pack (cos 2 x 6 = 12 right?). At 48V that would amount to something like 500W on the flats to do 25kmh. which is a pretty reasonable estimate of the power . Then given an 8% grade which my parameters indicate that to keep average 23kmh up an average 8% grade will need 743W. Suggesting that on the climbs I drew more like 2.7Amps per cell.

So its ball park and a good actual real world test

To refresh you with the course the distance and elevations are:

Basically I did that route again. 

Rather than record the whole trip again I decided to record just the most important parts: the slug up the hill from the bottom of the steep climb up to the top.

This clarifies the grade of the climb, the length and that the scooter just hauled up with almost no change in speed. Impressive on a 2 year old battery. 

The return voltage was 46.4V which is almost exactly what I'd got in the past and charge required 406Wh to refill which is almost exactly what I've got in the past.  This means that over 26km I consumed 406Wh which is 1.6kWh/100km or almost exactly what it normally uses (no surprise there either).

Points to consider on this I went up to Johns (adding a couple of km of uphill) and on the way up to Queen Mary I had a tail wind (which would have assisted somewhat). On the way down (of course) I had a head wind, but for the steepest parts the speeds were still sufficiently high that back EMF would almost fully negate any additional power demands for that.

Previous results

This test was pretty much a repeat of many tests and probably the best reference is this one from May last year, back then I determined there was no appreciable loss. Another test run worth a look at was this one (where I dug into more figures)

Conclusions

So given that this scooter is two years old, and has been (as mentioned above) fully charged when cycled (but usually no less than 40% before recharge) and is still performing within all practical intents as new. This is not unexpected and something which I explain in this blog post here. I've got further discussion here and here.

So the next time your on Reddit and some pack of fully ignorant-kiddie-wankers go on about killing your battery by charging it fully (NB using it as designed) ... just ignore it ... there is no evidence other than the clear evidence that they're idiots.