Solar panels

[glalt]

The smart pump checks the voltage every ten minutes and then the pump tries to start. Once it does start running, it keeps running. As suspected, the too small buck converter simply isn't big enough to handle the start surge, close but just not quite enough. The pump does start when there is no load but that's not good enough. I hate to order a more powerful converter because of the time involved. Lazada has none available here in Thailand, all come from overseas.

[glalt]

I wasn't able to find a suitable converter here in Thailand. I went ahead and ordered one from China that looks like it will do the job. I didn't want to wait but I had no choice.

https://www.lazada.co.th//products/i194 ... lFlag=true

[fhorst]

When I read the first part...
Jeah... Funny Chinese.
Max wattage on normal size solar panels is 390 watt.
The panels that do +400 are larger in size, have more cells (standard 72) and have higher voltage.

How to get more water in a liter bottle?
Just make it 1.2L 555 ...

For the pump..
Your pwm/MPPT solar controller usually can handle 45v and more.
If it is an automatic 12/24/48v model, it will need some battery.

Replace it with a 12A buck converter, 24*12= 288W.... Not enough to start

The pump might need a battery.
Starting power can be up to 3 times rated wattage.(= 3*200, 600 Watt)
So the pump simply doesn't get enough juise.

You can use 2 old (almost dead) batteries.
While they're not capable of really holding the charge, they will charge up enough to get the pump started.

"Any" solar charge controller that can out 24v should be able to keep the pump running.
Starting... That probably needs a battery to give the fist kick.