Current Sharing Between Parallel 12V Power Supplies With Different Amp Ratings

When you have a 12v dc power supply capable of 1a  output and in parallel another 12v dc power supply but capable of 3a output and a load in series drawing 2 amps how many amps are being drawn from each power supply? Same? One more than other? I know that by putting them in parallel inceases amperage to 4a, but is the ratio 3:1 coorisponding to their maximuim amperage output?

In reality im building a tethered drone with a ground power supply(15v at 25a max) which is going in parallel to the drone with a small, lightweight, high discharge, emergeny, lipo battery(15v at 100a max) . This battery will act as a capasitor by handelling the high amerage usage of the drone that the tether cannot produce without damaging itself. My question is will the battery assist the ground power supply when drawing more than 25a?

Hi Austin,

Theoretically, when you have those same potential that would be the same force delivering the same, however, considering the current output capability that matters to power source then this with greater output current can deliver more power, but case may differ.
Some of it has greater energy storage that's why it can output greater current with its design, or another case it is designed to deliver with that rating to drive a device or equipment requiring that current rating.

Hope it helps.

Best,
Neil

Since your ground power supply is much further from the load than the battery, there will be significant power loss in the cable during high current draw. This will cause more current to be taken from the battery. You do need to make sure that during normal current draw, you don't have too much drop in the cable so your battery will be recharged.

Be very careful in paralleling power supplies. No two are at the identical voltage. Let's assume your battery is at 15.1V and the round power supply is 15.0V. The battery is going to try and charge the power supply. If the relative voltages are reversed the supply will try and charge the (non-rechargeable?) battery. Now the resistance of the long lines are going to provide some protection by way of current limiting, but you need to exercise caution. One option is to use 2 diodes with the common cathode connected to the load. Another is to use a load share IC.

You may want to read this article (no doubt there are many more) -
Properly Configure Parallel Power Supplies to Share Load Current or Risk System Failure

https://www.digikey.ca/en/articles/techzone/2...Hz4oSHw0icKTb4Qq_WZq89oNKzECfl2EaAgzREALw_wcB

Thanks for the reminder on that, Aubrey.

One easy way to avoid any problems with the battery trying to feed the power supply is to always use the ground power supply to charge the battery. That way the battery voltage will always be at or slightly less than the power supply.

One other consideration is to make sure that you are not overcharging the battery. Lithium batteries are prone to fail in highly spectacular ways when abused.

drawing more currents matters to the load if it requires more, and yes, it needs diodes between sources ensuring the supply will be flowing to the load.