Here we go. It’s 49.6º out this morning, with a nice sunny weekend predicted, and though I swore I wouldn’t go outside until the temp was a solid 50º, I lied, and wanted to get the Spring charging process going. Let’s review, though. The pack was put to sleep last Fall after about 20 miles on it – so it was about half- to 3/4-tapped. Now, these cold days that I couldn’t ride, I could have charged and balanced the cells, right?
Absolutely not. You never want to fully charge any type of lithium cell when it’s cold. Why? Because when it warms up, it will kick into over-voltage. As we know, lithium can’t dissipate heat from over-volting, right? With the CALB cells they get damaged. With RC lipo, they start burning. It’s hard to know the facts, but a lot of these, “my lipo was just sitting on the shelf, and started puffing (or worse)” things you read about on the web, I suspect were related to cold-charging and then overheating.
So my process will be to bulk top-up the pack, and then to run it a few miles to pull some of the charge down. I’ll be watching my cell monitors carefully, which, by the way, are getting kind of nasty looking, with some plasticy sweaty-oozy sticky stuff on them. I have no idea what that’s from, but it’s nasty. Did I say that already, how nasty they are?
Now, I have two modules and yet 3 of these cell logs. (This is them, here.) I’m pretty sure now you can get 6s logs, or maybe even 12s units, so I think I’m going to trash these (or use them for something else), get the ones that are a better fit, and set it up so the monitors are on each pack rather than snaking wires up under the tank. More on that later. I also feel like it might be time to pick up a real charger. The one I have is a 36V cheapy, so I have to charge half the pack at a time. Maybe I might pick up a proper charger… something like the 12A Delta-Q QuiQ 72V Charger. mmmm. Yummy. Except for lithium, of course – that one’s for lead.
So, anyway, back to the plan. Once I tap the pack a little, I’m then going to take my little Turnigy charger ( the Turnigy Accucel-8 150W 7A) and top off each cell individually. This will get everything perfectly balanced, but it will also show me what cells are sucking more amps than others. I don’t do this as often as I should, clearly, but this should show me a lot about the general health of the cells. The shot above is the Turnigy, powered by the hacked X-Box power supply. More on that here.
In the meantime, there she sits. And OH! The temperature just hit 50. It’s a frikkin miracle.