It’s been a while since I’ve tested the full capacity of my pack – 3 years to be precise. I’m interested in how bad the pack has degraded since then.
As I’ve been travelling a lot and my TWIKE has been in ‘daily’ mode since then and I noticed some weird drops during my last TWIKE adventure to Italy, I’ve been keen on testing how much exactly the pack has changed since the last test.
For this I need to take out my balancing rig and start balancing all the cells before taking the TWIKE back out to a full test.
Warning: Never take off the battery cover and interact with the batteries without knowing what you’re doing. 400V+ kills silently and efficiently.
With this warning out of the way, I start with the usual – starting up my laptop and bringing my balancing chargers into place.
Good news: most of the pack is absolutely fine. Some cells are some thousandths of a volt out of shape – this is to be expected and not a problem at all.
Whilst my TWIKE’s energy/battery related components are fully exposed, it is always interesting to see how my TWIKE distributes energy – the so-called AK-Rail is responsible for this. -> if anything goes wrong here you might be experiencing problems like this one.
My pack has 42 battery connectors with 8 cells each. Balancing such an amount of cells with a single charger will take forever. This is why it makes sense to have multiple chargers working at the same time. I have multiple cables for balancing and controlling them via my laptop.
As mentioned, most stacks are fine. If I balance such as stack, things look as below.
Some stacks, however, are not OK and need about 3-4x the time to finish. This is because the charger attempts to bring all voltages back in-line. To do so, it removes any charge to the other cells until the lagging cells are back in-place.
Unfortunately, some cells are lagging so much behind that a normal charge with a balancer doesn’t fix the problem. For such cells, a charge needs to target one cell at a time. See below, how such a charge looks like:
After much longer than I thought, the pack is back to nominal and all cells are back to the expected voltages.
It’s a lot of work – but it pays off. My pack initially cost me 18k CHF. At this price, any investment in keeping the cells balanced will pay off in the long run.
I’m very curious to see how the pack performs now. I’ve got a pack capacity test lined-up for the next weekend. Check out that post to learn how the pack faired!
When I’m done, it’s time to put everything back how it was – the video below shows you how this works!
As always – keeping your pack healthy is a good investment in its future!