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1.7amp charge rate 18650 in a 1amp charge rate....
so if i replaced some old cells with an unknown charge rate will i kill the charger if the new cells charge at a rate of 1.7Amp? or is it just like power supplies? the batteries are CAPABLE of ACCEPTING 1.7amp but, can charge at 1amp? i wonder if they would charge way slower?
What the cell manufacturer usually state in the spec sheet are:
* recommended charge rate (ie. to keep the cell cool and healthy for extended periods)
* maximum charge rate (ie. still safe, but will likely need cooling and may affect lifespan)

The cells themselves do not have any circuitry to limit the current, and will very likely suck up at much higher rates, with possibly fatal results. It is entirely up to the charger to limit the charge rate.
Setting the charger to charge a cell at a slower rate is not a problem at all, in fact will keep the cell cooler and extend its lifespan. Typical rates for DIY Powerwall usage is about 0.2~0.5Amps.

How long charging takes is a function of cell capacity and charge rate. If you have a 2000mAh cell and charge at 500mA, then charge time will be around (2000mAh)/(500mA) = 4h. Though in actuality it will take longer, as the charge rates tapers off towards the last ~20%.
Modular PowerShelf using 3D printed packs.  60kWh and growing.
The charger is going to charge at what the charger hardware is capable of doing. If the charge rate is 1 amp, why would it be any slower or faster than before. It's like asking which travels at a faster speed? 60 MPH in a Prius, or 60 MPH in a Tesla?

The battery is just going to sit there and take it. Batteries don't tell charges what to do.

If its within specs, you are being nice to the cells. If out of spec... well, its out of spec. Might make heat, might not, might decrease life, might not.
OffGridInTheCity and Korishan like this post
+1 to above points.
Chargers are normally designed to put out a certain current ("constant current"), so the charger doesn't usually care.
It's the cells not the charger that could be damaged.
The key is for the max output current of the charger should be LESS than the specified charge rate of the cells.
Lower rates are harmless.
Higher rates may cause cell heating, damage, venting & much higher rates possibly fire or bursting.
Some cell chemistry & constructions are better at taking higher currents, some not so much.
OffGridInTheCity likes this post
Running off solar, DIY & electronics fan :-)

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