Discussion: Unattended Battery Charging

Leaving a battery charging unattended? Some types of batteries, sure, but any batteries?

If you are going to charge a battery on the Electronics Bench’s power supplies, you should be attending it in some form. The power supplies on the electronics bench have no battery protection/charging circuits and if a battery starts to run away they will happily supply as much current as they can.

Charging on a dedicated battery charger is nowhere near as dangerous as these will have protections in place, but you probably shouldn’t be leaving these alone either.

Nog, I’m not trying to be a pain here, but all standard benchtop power-supply have both voltage AND current limiting, which are designed specifically for this purpose. They are safety features designed to prevent “run away”, and they most definitely will NOT “supply as much current as they can” if used correctly.
Please stop insisting people don’t use a bench-top supply for exactly it’s intended purpose.

With regard to leaving them “alone”, well, that’s another matter entirely, and depends on the circumstances, and perhaps the chemistry of the battery, and the general consensus on what is safe. For example, lead-acid gel-cells are super safe to do this with, but LiPo “pouch” batteries are generally not considered safe to do this with unless they are in a protective metal box, or “battery bag”, or “outside”.

Buzz, you are correct in that if the current limiting is set correctly this is less of an issue.

However every time I’ve come across a battery left charging unattended the current limiting was not being used and the current knob was wound all the way up.

The batteries I’ve found left unattended have been 18650s every time, which as you know the recycled ones we use can be duds that get hot and/or catch fire.

18650 batteries have a Lithium charging chemistry that means they need to have a hard voltage limit ( 4.2 volts) , and will generally accept as much current as you can push into them within the limits of the benchtop supply AND 4.2volt cap. ( that’s 4.2v per cell, so for series cells the number is higher but still relevant ).

For example, my 18650 cells can be charged at up-to 60Amps, by design. The benchtop supplies can only do 3A or 5A or similar ( internal supply limit, being much smaller than the batteries actual limit ) … so to charge these cells even “slowly”, the current limiter really does need to be cranked “all the way up” on these benchtop units. I see no problem here, as they are being used within spec, and are charging the batteries much, much slower than the batteries are actually capable of, AND the voltage and current limiter/s are still in effect, even if the “current limit” knob is tuned “all the way up”.


The fact of the matter though is that we have a dedicated 18650 charger in the greenroom corner that is accessible to everyone, there is no need to use the benchtop supplies.

The dedicated chargers don’t have any way for you to bump the voltage to the wrong value and cause issues with the charging.

I plan to set up a proper charge station as soon as we reconfigure the electronics bench to avoid this problem in future.

Edit: Though I’m not against people using the power supplies to get a lead-acid battery back up to charging levels where you can use a charger on it.