Daly bms junk


Solar Enthusiast
May 27, 2021

Although I've not had any problems with my two FET BMS''s, one being a Daly, I am in the process of replacing them both with contactor based units believing that they are inherently safer due to not having an electronic connection that can fail in an unsafe condition, I do have a Chargery which will replace the Daly. The other will either be a Chargery or a 500A relay based smart BMS I've sourced, seems the majority of failures is related to FET failure of some sort or not using one at all.
Another option is to use a smart BMS to drive a contactor, this would mean the only current the FET-s would carry is the 3A pickup and 20mA holding of the coil, some features would be lost, over current and short circuit protection, but the important cell voltage protection would still function normally.

Not being critical but rather pointing out something you may want to consider changing the SPD ground wires, they should be as straight as possible going directly to the ground rod, as opposed to being connected to a common ground bus, having them indoors is considered bad practice as it's inviting potential lightning into the home, I mounted mine in a weather proof enclosure outside above the ground rod, the breaker are indoors for convenience, the remote array has local disconnects for service purposes.

Can't see due to resolution what the Uc voltage is on the SPD's, but they should be only slightly higher than the SCC operating voltage, many are designed for grid tied higher voltage string arrays 600-1000V, these won't offer much protection to a system operating at 150V max, for example.
Yeah spd is to big but that’s exactly what they have in the combiner boxes so that’s why I ended up with it. As far as the ground wires the spd has to be right on the line it’s protecting so it was the best spot for them. The line goes through the brick and then underground.