HiLetgo 250W DC-DC Module 10-40V to 10-50V 6A Adjustable Step-Up Power Supply Module 250W DC Booster Constant Voltage Constant Current Power Converter Module

Works great

After seeing some Youtube videos, I got this to try to revive a Ryobi 40v battery that would no longer charge. It came with zero instructions so you do have to figure things out on your own. There's no indicators for the output either so you'll need a multimeter so you can see the actual output while making adjustments.I had to connected to an old laptop power brick (19v 4.5A), had to try a few times before the output would actually adjust up to 40v. When charging is taking place, there is a faint clicking sound which is useful to know that it is working. Took nearly an hour to get the battery from 16v to 31v, and it is back to life. Now the Ryobi charger could charge it normally again.Product description said to add heat dispersion if output is >4A. In my case, output would be around 2A @ 40v. I did place the module on top of a small metal box to help disperse heat, but the whole unit is hot (not just warm) to touch after an hour. So definitely be mindful of heat build up if using for extended period of time.

Constant values hold nicely as long as power-in is sufficient. I initially tried to adjust CC with no load on device. Just 10 amp DC range on VOM. For the short duration I put the meter across power-out (less than a second) it appeared that I was drawing max current well above 10 amp. The device survived that mistake so it has good short circuit protetion. Once I loaded the output both CV and CC were easily adjusted and accurate. Very little if any drift as long as power demand stays within reasonabe limits

Good. Good. Good and then some extra good.

Does output the rated power. BE CARFUL using power supplies and high cell batteries. If you do not resist the input flow of current the current ripple will blow them up violently. If using a power supply turn your amps down and bring them up slowly. If using high output batteries use a resistor or anti spark connectors. lipos will blow them with no current protection. Hear my warning.