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I have an 18v 2000mAh black and decker drill battery that I want to charge and use in the mean time while I wait for a proper charger to arrive.

I have a DROK Voltage Regulator/Buck converter (https://www.amazon.com/gp/product/B078Q1624B) that has a constant current mode and from what I understand should be sufficient in charging it but I wanted to confirm.

From what I've figured the charging voltage should be around 21v and the charging current should be Current/10 so 400mA constant charging current although the official charger states to output 500mA.

So with the Regulator set to output 21v and 400mA in constant current mode, this should charge the battery just fine without risk of overcharging or damaging the battery right?

If there is anything I'm misunderstanding or missing please let me know, thank you ;)

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  • \$\begingroup\$ It's not a good idea to fast charge batteries without thermal protection. Charge them at half the rate you think they can tolerate and monitor the temperature to make sure they don't overheat. Ni-Cd batteries should have a maximum float voltage of 1.55V per cell. If you have a battery that is rated for 18V, it's possible that you have 15 cells in the pack since the rated output voltage for Ni-Cd is 1.2V. In the case of a 21V supply, your final float voltage for each cell is 1.4V per cell. This should be safe but there are some arguments for battery life that you should not exceed 1.3V. \$\endgroup\$ – ScienceGeyser Feb 22 at 16:54
  • \$\begingroup\$ Thank you very much for the quick reply, I realized that 400mA was the fast charge rate when typing that but didn't think to much off it but I'm glad you also mentioned it, I will definitely be charging it at a slower rate and also plan to monitor the temp. So for 1.3v per cell then 19.5v would be a good charging voltage right? \$\endgroup\$ – Dark Dragoon Feb 22 at 18:24
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    \$\begingroup\$ 19.5V will be safe, it's just going to take a long time to charge. I have charged many batteries with bench power supplies but you have to keep an eye on the battery to make sure it's not getting hot. \$\endgroup\$ – ScienceGeyser Feb 22 at 18:29

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