Poe power supply

21

Hi Patrick

Don’t forget to factor in conversion efficiency. If flying a bit close to the wind this has ben known to make or break an idea. Could be anywhere between 85% and 95% and should be published. about 85% seems fairly common.

Also the mAHr numbers will be AT THE BATTERY. You will have to calculate the figure at 24V after conversion efficiency has been considered. Convert to watts to do this. Convert to watts for all calculations of this nature and you won’t go wrong.
Cheers Bob

1 Like
22

So the power supply questions continue and I appreciate the responses so far. It seems though that I can’t find a single unit that will do what I want.
I have a 24v lithium battery pack made up of 6 x 18650 batteries with wired in bms.
My circuit requires both 5v and 15v constant voltage for minimal time period (2min every hour)
I want to keep the battery charged with solar.
Essentially I have been looking for a solar charging circuit that will keep my battery charged but not attempt to drive the circuit direct. Obviously I also don’t want the battery to attempt to power the panel.
I know there are many build your own power path circuits shown on the web but I can’t seem to locate a product that will do this task.
I have an old 230w panel that outputs about 40V +/- 3v
Can I just place a dc/dc step down converter in line with this panel and provide the required nominal 27v to charge my 24v pack?

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23

Hi Patrick,

Could you elaborate on what your BMS does? Some just act as protection, others manage charging and balancing, so the complexity of your BMS decides what else you have to “fill in” with your own hardware.

It could end up being as simple as a DC-DC converter if your BMS is complex enough to keep your cells charge, protected, and balanced properly:

-James

24

james,
yes the BMS that I have does protection, charging and balancing. It is this module HX 6S 12A
Running my circuit direct from the battery terminals of this board is correct? Do i run into a problem of always bypassing the charging circuit during the day by doing so?
Patrick