You could potentially build it yourself. Similarly behaving cells can be connected in parallel. (Before soldering or spot-welding them together, connect them through resistors for a while so their charges/voltages equalize without excess current.) Then they behave as one big cell.
Laptop batteries, which typically have the cells in pairs (sometimes in threes), are done this way.
This is the way to do it. Iāve used 1 Ohm 5 Watt resistors in series with each cell, all in parallel for an hour or two. Check for equal voltage with a volt meter (1 mV resolution or so), then carefully connect the cells in parallel. At this point an inadvertent short can deliver 50 amps or more. (Iāve melted stainless steel tweezers.)
One caution with the pack, go easy on the charge rate with parallel cells.
A typical single 2.5 A-h cell can easily be charged at 1 amp (0.4 C rate).
If you have four of those cells in parallel for a 10 amp-hour total, donāt charge at 4 amps. Two amps should be safe. There will be minor differences in the cells (even if you carefully matched them, they will vary over time) and the current will not distribute exactly equally. Monitor temperature (most charge chips accept a 10 kOhm thermistor).
Similarly if you have fast charging batteries. One cell may charge in 1 hour or less, but ease off with them in parallel.
Iād guesstimate the charge rate should be no more than the maximum charge rate for a single cell times the square root of the number of parallel cells. Something like that.
Wellā¦ your sweat-mileage may vary. In a mildly cruel irony, the more youāve conditioned your body with exercise, the more quickly and profusely you sweat. Watch college or professional basketball players: theyāll be bone-dry at the start of the game and drenched in perspiration a few minutes laterāeven before the game has picked up to the point where theyāre doing more than jogging.
Iām pretty skeptical that e-bikes are the answer here, but if you need to get somewhere in a dress shirt that isnāt pasted to your skin, pedal bikes arenāt the answer in a lot of circumstances.
Thought. Some time ago I made myself a shirt with built-in cooling fans. Could this be a useful approach for immediately evaporating sweat produced during cycling, keeping the bike operator both cool AND dry(ish)?
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