Sunday, 13 October 2013

Battery test

I gave my new battery pack it's first proper test today - I don't count the test that was cut short when I hit the tree.

I wore my most solid crash helmet. And, by the way, I've ordered a full-head motorcycling helmet with face plate. You don't need to hit me over the head more than once for me to learn.

I tried the battery pack out on my three different electric bikes; one standard, one with a sensorless motor and one with the motor I got a few months ago from China. They all ran very well.

When I got the battery back, I noticed that one of the plug/sockets was rather loose, and that one pair had been used a lot more than the other (the batteries are two pair in parallel, each pair being in series to give me an 8-cell, 29.6 volt battery pack at 5 AH, and the two of those pairs in parallel making it up to 10 Ah). So I think I was running off only one of the pairs.

If that happens when I'm out, it's not a disaster. It means that one of the pairs will run down and start beeping while the other one is still charged. I'll be able to see that, as soon as I look at the battery pack, because each battery of four cells shows me its voltage, and the voltage of each cell. And what I'll do then, is disconnect the run-down cells, and run on the ones that hadn't been used.

Better, of course, will be to have good connections in the first place!

Since this worked out so well, I'm seriously thinking of getting more of these batteries; enough to make up two more packs. That's 8 batteries at £18.25 each, £146 to add 20 AH to my capacity, for a weight of about 4kg. I'm thinking that changing battery while in the field would take a bit longer than it does now; with my old batteries, I just have to unplug the old one and plug in the new. With my battery pack, I have to unplug the main lead, then unplug the four power leads to the batteries, then unplug the four charge monitors. Then plug all that lot back in with the new battery. Even so, I can't see it taking more than a minute or so, and the way I've designed it, I can't plug anything in the wrong way round. And with the old batteries on the bracket they used to be on, it could take me quite a few minutes to lever the old battery off and ram the new one in; with the new battery packs simply sitting in a pannier, that's no longer relevant.

Another useful purchase would be a large ammo can; they're used a lot in caching as good, strong, watertight containers. One of those would nicely store three of my battery packs, and keep them safe from damage while in transit.

Something that occurs to me for possible future use - previously, I was committed to 24 volt batteries, and if I moved to a 36 or 48 volt motor, those batteries would be wasted. But now, if I want to change to a 36 or 48 volt motor, all I have to do is a bit of reconfiguring; for example, for driving a 36 volt motor, I would make my battery pack out of six of these batteries instead of four. So it's just a different wiring harness!

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