Can a CNC PSU be used to charge a lithium pack via a BMS?

lionman

100 W
Joined
Jun 7, 2018
Messages
182
I am planning a build of a 14S6P pack with a 45A BMS.

Can I hook a PSU up to the charge leads of the BMS or is there some other circuitry required to go between them?

I was thinking something like this https://www.aliexpress.com/item/400W-60V-6-7A-Single-Output-Switching-power-supply-AC-to-DC-SMPS-CNC/1667637251.html?spm=a2g0s.9042311.0.0.73814c4dDAlFcS

If I do need CCCV circuitry, is there something available that would work with the PSU above?

Cheers.
 
Couldn't say for that PSU or not, but there's been a lot of discussions about PSUs as chargers, and the things to look for or modify or add.

Some of these threads are relevant (not all are) and may help you find a model of PSU that will do what you want.
https://endless-sphere.com/forums/search.php?keywords=psu+charge*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

This list is about specific ones:
https://endless-sphere.com/forums/search.php?keywords=meanwell*+charge*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
 
Thanks for the search tips. So much to read!

What I don't understand is why if a PSU is adjusted to put out a constant voltage why it can't be directly hooked up to the battery or BMS?

Once the battery reaches the same voltage as the PSU there won't be any potential difference between the two so no more current will flow.

The PSU can only deliver 6.7A so in a 6P pack that's a little over 1A per cell which is a modest charge rate.

My plan was to dial the PSU in to 57.4V which should get each of the 14 cell groups to 4.1v which should extend the life of the pack.

Is there really any need for additional current regulation? The PSU says it has load regulation but I guess it depends on how good that circuitry is?
 
lionman said:
What I don't understand is why if a PSU is adjusted to put out a constant voltage why it can't be directly hooked up to the battery or BMS?
It can, as long as it also limits current in a non-hiccuping way. If there si no current limiting, then either the battery will be damaged (if the PSU can supply high enough current) or the PSU will be damaged (if the current demand from the battery is high enough). And/or the wiring itself could be damaged.


Once the battery reaches the same voltage as the PSU there won't be any potential difference between the two so no more current will flow.
That's correct.

The problem is at the other end of things, when the battery is drained, and the PSU is pushed to it's limit. What happens then depends on it's design. Most psus are not made to deal with this in a way useful to charging batteries.



Is there really any need for additional current regulation? The PSU says it has load regulation but I guess it depends on how good that circuitry is?
And how it works. If it is not designed for constant current, non-huccup-limiting (whcih shuts the whole thing off, then back on, then off, then on, trying to recover from a "short circuit"), then the PSU can be used as a charger. Otherwise you have to do one of the various things as shown in the assorted discussion threads about using PSUs as chargers.

It's easier to just make sure you get a PSU that already does it the right way. ;)
 
Back
Top