CG Solid State Relay SSR-100DD DC to DC Input 3-32VDC to Output 5-240VDC 100A Single Phase Plastic Cover…

Purchased this after my first relay blew. This one is doing the job well and as an added safety measure I'm using smart plugs to kill the printer in case this one fails.

Can't handle 100amp and allows current to flow in reverse when unpowered. Tested with 2 100ah batteries and a 100amp PSU. With the power supply off and the relay unpowered, the batteries fed power to the PSU, causing an LED to remain powered. I also put a 6ohm resistor on the PSU output and it allowed more current to pass with only a slightly increased voltage drop across the relay. In normal operation with 100amps flowing, the switch immediately started to increase its voltage drop and failed within 30 seconds.

I just got this connected and working so can’t say anything about longevity though the reviews talking about excessive heat worry me. There’s a diagram on Amazon along with a statement below it totally backwards from the drawing. I got a 2”x4” paper in the box with a similar but different drawing than the one on Amazon but with the same statement below it. All of these are wrong! It took me a while to troubleshoot and get working. Just looking at reviews and “Jon” has a great one star review with his own diagram and it will only work if you wire it like his diagram and ignore their worthless documentation. Wish I’d seen his review before all my troubleshooting effort.

I bought the 100A version assuming it would be way overkill for my 60A purely resistive load. I'm using a PWM controller at 50hz. My sample has the load terminals marked (-) and (+) which is different than the photo posted in the description which has terminals marked (1) and (2). If I use their example circuit, the polarity would be backwards for the load wiring. Their example has positive voltage entering terminal marked (1) which is (-) on my relay. This is assuming Live and Neutral from their "DC Power" means (+) and (-). I wired the relay per the (+) and (-) terminals for voltage, it worked for about 5 minutes. When it failed, it failed as a short circuit, not ideal for a resistive heater. The LED indicator also stopped lighting up. I was originally feeding it 3.5v PWM, which was not enough to get it to turn on, I had to switch to a 15v PWM, even though its rated 3-32v dc input.

This relay does what it says. I ran a 30 amp 24v load through this for 12 hours with a medium sized heatsink and a fan. It would require a very large heat sink and fan to even consider running a 100 amp load, but for the price, it does what I needed it to do.

100 amp SSR: I measured an internal resistance of 0.25 ohm with a 5 amp load current. For small currents, the resistance is approximately linear. If I tried to run 10 amps through it, it would dissipate 25 watts and drop 2.5 volts (if the resistance stays linear). A good heat sink is required. If I tried to use it with a 50 amp load current, it would either melt or burn up trying to dissipate over 600 watts. This SSR is only useable at 10% of its load rating. Observe the polarity markings. Current must flow from + to - within the relay. Warning: It's a short circuit if wired backwards. The device will not operate properly with an AC load; it acts like a diode. I've tested a dozen of the 25A relays, and they all have the same internal resistance characteristic as this 100A unit.

I had these set up as switching relays for DC solar diversion loads, load and control side volts and amps well within specified range. Each unit worked briefly, but both failed within an hour of use, and will allow current to flow through the load side with little resistance even when the control side is completely disconnected. Not recommended for any serious use.

According to my amp clamp, these things burned up immediately at 25-30 amps. I had an 80 amp breaker hooked in series with them, thinking that would protect them. But I literally hit the switch and thick smoke arose. Don’t be fooled by the positive reviews, these are trash. Unless your trying to control maybe 3 amps, I’m sure they would work fine for that. But don’t look at that 100 amp max and pretend it means something, because it doesn’t. Propaganda