SSR testing

[Craig]

Hopefully tonight I will be able to test my SSR's I have 250 Amp and 500 Amp ones. Obviously the first test is weather or not they work. I was also going to run them under load and check temperature often to see how they heat up with and without a heat sink. Does anybody have any other tests they would like to see.
also i will test the current draw from the load source like the Chargery

 

[BiduleOhm]

Yep, if you can mesure the Vdrop and the current so we can calculate the power losses it would be great

 

[Craig]

Ok so test 1 with 200 Amp SSR . I was able to run 60 Amps at 24 volts just fine I did this for about 15 minutes.

• The current draw from the control side at 12V was .1 amp so 1.2 watts.
• Voltage drop at 60 amps across relay was .9V (seems way high to me but i do not know what to expect) battery was at 30.0v load side of SSR 29.1v
• For this test I used no heat sink as I couldnt find one. the relay got to 160 Degrees F (not at all sustainable IMO)

I ordered some heat sinks and have a 240A and a 500A relay on order thought those were the ones I was getting but they are still coming.

Should I be cycling the relay under load as well to see what happens?

 

[tim0shel]

Sounds like some interesting testing going on. Thanks for posting your results. Provide some photos and what SSR you are testing. How do you plan to heat sink them?

 

[Steve_S]

Craig, the 20oA relay hit 160F with 60A flowing through it ? is that right ?? sheesh, scratching head
That doesn't seem right to me.

What relays are you tinkering with ? Someone in another thread yesterday mention the Blue Sea L & ML Relays but they are MSRP $230+/- a pop (not an option imo) as it seems a tad over the top on pricing.

 

[tim0shel]

Craig, the 20oA relay hit 160F with 60A flowing through it ? is that right ?? sheesh, scratching head
That doesn't seem right to me.

What relays are you tinkering with ? Someone in another thread yesterday mention the Blue Sea L & ML Relays but they are MSRP $230+/- a pop (not an option imo) as it seems a tad over the top on pricing.

Yeah that heat is pretty high but is a good bit of amps for 15min. I mention the Blue Sea ones but mostly as a reference to the Alibaba ones someone had posted. Thinking those they posted was pretty much the same but at $5x.

 

[BiduleOhm]

Craig, the 20oA relay hit 160F with 60A flowing through it ? is that right ?? sheesh, scratching head
That doesn't seem right to me.

That doesn't surprise me too much. Chinese relay (so high Rdson mosfets because less $) + no heatsink = high temp. Also the Rdson rises with temperature (that's why mosfets are subject to thermal runaway) so the Vdrop should be a bit lower (0.7 V maybe?) with a heatsink.

What might be interesting cost-wise is to buy a cheap SSR like this one and replace the mosfet(s) with better one(s).

 

[Steve_S]

I would not want to buy anything that needs to be modded off the shelf... that's a bodge isn't it... I believe Craig mentioned that he's playing with US made ones in another thread. Hopefully he'll enlighten us as to what brand / type he's tinkering with.

 

[BiduleOhm]

Well, you can see it like that or you can see it like you buy a base that as everything you need and you improve the weak link. The other solutions are to buy a proper but expensive SSR, or to design it from scratch. That's why I think it's a good solution.

If it's a US made SSR then it's a very very crappy one because 54 W lost at barely 1/3 of the current rating is not acceptable. It'll dissipate more than half a kW at 200 A (I²R...) so unless you watercool it it'll just go nuclear...

 

[Craig]

No these are Chinese relays I have ordered samples from 2 manufacturers. After i make proper tests and know more about what I am doing I have about 10 more manufacturers to check out.
At what price range would you all find acceptable for a SSR vs a regular relay like chargery sells. I was hoping for somethng equal in price but that may not be possible.

 

[tim0shel]

I think at that price range 55 ish or so would be awesome. I had found something while back I was watching on ebay that was around 79 If I recall correctly.

 

[BiduleOhm]

You can definitely make a correct 200 A 80 V SSR (i.e. less than 20 W dissipation (< 0.1 V of Vdrop) @ 200 A) for far less than 55 USD (and even cheaper if the voltage you handle is lower than that), especially if you make them in high volumes.

 

[Craig]

Just got these inn mail today I am very impressed so far the heat sinks are massive and the relays feel substantially heavier than others I have tested.




the Heat sink on left I ordered from Amazon the ones under the SSR's are what came with the 240A and 500A SSR's

 

[Steve_S]

Yumpin Yiminies !
So let the screeching cat out of the bag... how much were those beastly creatures ?
BTW, it would be good to see pics of the different relay's your playing with, any spec info too.

 

[BiduleOhm]

Nice heatsinks

But 500 A on those terminals? Hmm... I'd be very hesitant to pass that much current (even half that actually) in those.

 

[Craig]

Well I think we may have a winner!

Tested this




After 15 minutes at 50 Amps Temperature was only 71 Degrees F. Voltage drop was 0.1 V and Controll load draw at 12Volts was 0.34 Amp

This 240 Amp relay will be about $40.00 including the beefy heat sink ($6.00)
The 500 Amp relay I will test Tomorrow but It is quite a bit more expensive $100 including heat Sink. It has max voltage of 75Volts

I do not have a spec sheet as this is what distributor recommended and sent me to try.

 

[Craig]

Its obvious by the lack of Voltage drop across the relay that these would produce much less heat in fact when I was running just lights and a nominal 6A load the relay was at ambient Temp.

 

[BiduleOhm]

Nice ?

The temp was with or without the heatsink?

Any chance to open it to see what's inside?

 

[Craig]

With the heatsink but no heat paste. The mfg did tell me to add heat paste but I wanted to see if it made a difference.



This also shows how I attached the cables.

 

[Craig]