Using a MPPT as a battery charger?

[Vigo]

Why, it would just adjust the duty cycle to limit the current the charger can handle.

The problem is the controller doesn't know anything until AFTER the first 'pulse', and if there is very much voltage difference between input and output, and the input is a battery capable of supplying hundreds, perhaps into the 1000a range, that first pulse = you let the smoke out. I've verified this personally..lol

If you think about a 12v typical car battery, hooked up to something with 12 less volts.. almost a dead short.. lots of them will touch 1000a in that scenario. Some bigger ones will do 2000, some bigger AGM claim 3000+a. How many microseconds of that does it take to flash boil the metal in the transistor trying to flow that current? One. 1 microsecond. 36v into 24v, same deal, doesn't matter. You've got a source with huge ampacity hooked to something with much lower volts and very low resistance in the circuit = instant excitement.

It can be made to work with much finicky bs. It would be easier to skip the bs and buy an mppt controller with current limit settings, as they 'ramp up' versus simply shorting the input to the output.

 

[Pappion]

Aright I just tried it with this 10a 48v psu. Still drags the voltage down. I see what it's doing now, it's searching for MPP all the way down to the battery voltage, once it directly connects to the battery it releases. Now on this PSU it only did it once, but I think that's because the battery is fully charged. I'll let it drain, and get some video next.

View attachment 98800

Many solar controllers are positive ground, which means the positives are shorted together. Regulation is done between the negative connections. If your using a non-isolated negative ground supply/battery as a substitute source, prepare for smoke. You just shorted the negatives.
Negative ground is an advertised feature. If they don't say it is, then its not. Except for my Victron. Use an ohm meter.

 

[Pappion]

what if a PWM solar chager contoller was used?

PWM are typically Positive Ground controllers using the robust and cheaper NMOS fets vs. the PMOS fets.
Many solar controllers are positive ground, which means the positives are shorted together. Regulation is done between the negative connection. If your using a non-isolated negative ground supply/battery as a substitute source, prepare for smoke. You just shorted the negatives.

 

[Pappion]

Who let the smoke out?
Who, who, who, who, who?

 

[cs1234]

You guys sure do make me realize how little I know about the complex inner workings of electronics.