5a lithium charger modules

[vinceroger69]

Re: 5a lithium charger modules

just been going through some of my old purchases from aliexpress i have one of these can i use it to charge lithium batteries?
https://www.aliexpress.com/item/LM25...72e6cd557ef8dc

[vinceroger69]

Re: 5a lithium charger modules

Those modules use XL4015 buck-converter (step down) IC, rated 5A but those are chinese amps... so derate by 1/2 for actual use Some of these modules have tiny diodes, others have large heatsinks.

Charging a battery, you get backfeed into the IC if input power is removed.
It has a P-ch MOSFET inside so it should have a built-in substrate diode and not blow up if connected to a battery.
There is a current spike when you connect only a battery at the output of the buck converter (with no input power).
The input capacitors get charged, and maybe this is what damages the IC.

You can add a series Schottky blocking diode at the output. Like SS54, SB540, or junkbox parts from a PC power supply.
That diode will also make heat, several watts worth (5A*0.4V=2W) and best to have some heatsink if you are going for 5A.

The diode will make the exact charging voltage mushy due to its voltage drop, so the IC feedback trimpot might be moved to monitor battery voltage after the new diode.

TI Design Trade-offs for Switch-Mode Battery Chargers fig. 17-19 show the situation.

Hi just tried this unit out unmodified using a 19v 4.7 amp laptop charger as a supply i was going to charge a 3.7v lithium battery so set output voltage too 4.2v i then tried too set the amps i cant seem too get a ready when trying too set it so i tried it on a higher output voltage 12v and could amp reading ok its just at lower voltages it dosnt seem too be able to set the amps, this module also gets hot the whole units capacitors and ic even with added heat sink maybe because im trying too lower 19v 4.7 amps down to say 4.2v 1 amp

[sam_sam_sam]

Re: 5a lithium charger modules

You need to have the power supply a few volts higher than voltage that you want to use to keep from wasting the extra voltage up in heat

This would be the way I would approach this

Another were if you are going to use 4.2 volts as your set point then use something like this 5.5 to 7.5 or something close to it

Or you could use something like this

https://www.ebay.com/itm/DC-DC-5-36V...cAAOSwIIFbT2eZ


I have used a version of this that does not have the meters on it

You can load it up to about 4 amps and it only runs warm on the heat sink