Am I misreading those batteries or do you have them in Parallel and series as one large 31 amp hour 7.4V battery?
Xyster, on the side of the battery pack where the cells are jumpered to put them in series, the wires running parallel, will theoretically carry no current, and are therefore unnecessary, at least from a power standpoint.
it might be a good safety feature if the individual series strings each had their own fuseable link to protect against a single cell shorting.
Now that I think about it, the low current wires will help balance the cells, but since the current is very low, you could use much skinnier wire, which might be easier to deal with.
I guess I was thinking some of the jumpers (ones that say "most current") could be replaced with fuse wires. Of couse, too late now for that one.
I just keep remembering that Valence video of the lithium battery that has a fairly spectacular "thermal event" after being hit. Having a few cells go off would be better than the whole pack. See the video here:
You really are not running ANY kind of protection with your battery pack?
The only "meltdown" was when you allowed the voltage to drop below the safety zone and it burned out about 25% of your batteries. (as you were riding?)
Did the fire occur in such a way that you could smell it or feel the heat as you road?
Do you use any protection in your charging or are you simply dividing things up into small units and then praying each one is okay?
It's safer and better than the rather goofy way that I soldered my 12s8p pack.
What protection would I use? Each subpack is charged individually by a single cell 1.5 amp charger -- which is a very low charge rate. Each and every single cell is balanced with every charge this way. The chargers themselves only have one voltage setting: 4.2V. It seems virtually impossible to overcharge the batteries because as 4.2V is approached, the current trickles down to zilch.
1. You charge your pack(s) with a SINGLE CELL charger? How could this be, since many 4.2v constitute more volts, there for the charger will detect LOTS more volts, and not even begin to charge.
2. Your pack(s) don't have a charge-discharge electronic board, so how do you know when the batt pack has reched it's discharge limits?
If that thing bursts into flames, look what gets roasted.
Got Nomex underwear?
I didn't see any PTC's. Was that a previous pack? Those work like a fuse, but suck at high currents.
They do make much more stylish duct tape. I use black.
I used to have a roll of camoflage duct tape, great for that "military grade" look.
Your total disregard for the conventions of "safety" is having an effect. Rather than me being worried about Lithium batteries the lack of fear you demonstrate tends to make me also want to "risk it" and build a pack without all the PCB's and crap that makes the things overly expensive and complicated.
Do me a favor and create a new "technical thread" and just walk through category, by category all the areas that you need to watch out for and also what is "overhyped" as a fear. (when you are done with your ride of course)
What about, a dum-charger? (Dum= no automatic cut off, no lights, just DC current).
One that would mimic a fully charged battery. One that would give constant 4.2v from the beginning, until you unplug it, like a fully charged battery that never runs out of juice.
Would it charge the other batteries, therefore the whole pack?
Because, if one battery has more juice than the others in a pack, it will give its juice to the others, right?
That bike needs a wash!! check your shock absorber on the rear ha ha, does it move?
I want to know how the batteries are charged,one by one ? no BMS contol it when the batteries charged
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