SSR testing

[Steve_S]

Then isn't that a BMS's function?

The SCC & Inverter read the "Whole" battery bank voltage, they generally do not have a way to interact wit the BMS nor do they now what each pack and what each cell within a pack is doing internally. Most of the time this is no problem and everything just ticks along. BUT should one or more cells trigger a fault condition in the BMS (under/over volt or temp etc) the BMS has the job of being the Gatekeeper and will shut off the pack. Guard Dog duty if you will and it is the last stop if something happens.

Some SCC's & Inverters CAN interact with a BMS. Depending on the device & BMS different actions can occur. For example Victron can communicate with a BMS through it's interface. If using Victron Batteries then I gets the rich data and acts accordingly BUT if the BMS is not supported then it as limitations.

 

[tim0shel]

UPDATE ~ Sorta !
Jason & I have been exchanging detailed email's in regards to the documentation I am reworking. Of course the Relays & the Delay board came up and with some back & forth, I lit a fire under him. Starting next week they will be doing their own testing on SSR's from a couple of companies, as well as Energy Saver Contactors as well. I've provided connections to a couple of manufacturers to him that seem to suit the needs.

Some background. Until Jan.2019 the Delay board did not exist, it was created to fill the need (use case) for EV applications. The fellow at AZLithium (who did the YT Video with the Nissan cells & the BMS16T) is the one who instigated it. Until that time, Chargery only recommended Relays and did not offer them as "additional optional components" but client demand had to be filled, so they went with Known Good reliable contactors that do the job, to address the need quickly. At that time SSR's were extremely expensive (still are in many cases) but that picture has changed considerably over the past year.

The Chargery BMS' are designed to meet all kinds of loads, Inductive, Capacitive and Resistive or others. As a result, it is difficult, even impossible to provide one or two solutions (use cases) to meet all of the varied requirements. The Delay Board is optional and may be helpful for pre-charging an Inverter depending upon the Inverter. The Delay board option is not an essential component, it's "need" is determined by the customer, although customers maybe don't know this, they have to consult their Inverter Documentation and/or other "load" devices to make this determination. The delay board was designed more for EV Support as the loading and operations are considerably different than for non-EV use.

-- Side Note... I am in contact with OEMS in regards to the SSR's and the Energy Saving Contactors and it will be a few days of back & forth before I have much information to share (also passing info up to Craig to help him in his testing too). The legwork is underway.

In closing a ponderance for folks. FAN's a big deal ? Seriously ! take 12VDC 100CFM box fan @ 0.015A (like those used in computers) the power draw is minimal. How many people leave an LED lightbulb on all day ? No matter what you do, there will always be some overhead with whatever gear you are using. For $3 a thermostatic control can be added so the fan only runs on set thresholds. We are not talking about 100W or even 10W LED Lights use between 3W-12W @ 120VAC. Don't get overly distracted with Minutia, you'll lose sight of the bigger picture. BTW, If you fear a relay draining your system will be the end of the universe, then maybe a rethink of what you are doing and how you are doing is warranted. Overhead Cost has to be built into the design of your solar system. If one has to nitpick, consider the Inverters at 85% efficiency versus those with 92% or higher efficiency, the less efficient inverters waste far more than any lame relay ! Pick you battle carefully and with wisdom.

I might be wrong here but was looking forward to using delay board to have external switch to turn the main power off as it seems to have that option. Instead of using the display and turning off. Maybe I'm not sure how this works and can use the board for this and with small delay.

 

[Craig]

Then isn't that a BMS's function?

Yes exactly but the Chargery allows for external relays so you have unlimited current potential.

 

[Craig]

UPDATE.
i was able to put together a 140 Amp load for about 10 minutes. The terminal where the load cable leads the relay heated up to about 170F.
The relay itself stayed about 50 degrees cooler. Next test i will try and record all the portions of the relay with the thermometer. This is the 240Amp relay.

Im thinking the terminal heat would be the same on the larger 500 amp relay.

Wondering if i could put on a larger connector to help disperse heat.

Also would same heat be created with an automotive style relay?

Thermometer video

 

[BiduleOhm]

Well, it doesn't surprise me alot, I said what I thought about those terminals on the first page...

But that's a shame because those SSR seems pretty good on the silicon side, beeing limited by the terminals is a big bummer.

 

[Craig]

Well, it doesn't surprise me alot, I said what I thought about those terminals on the first page...

But that's a shame because those SSR seems pretty good on the silicon side, beeing limited by the terminals is a big bummer.

Yes you did! I'm wondering if I can get a terminal with a heat sink made.

 

[BiduleOhm]

You can, but the right thing to have would be a proper terminal on the SSR because here you lose a lot of power (which we want to avoid by using a SSR, so that's kind of counter productive...), well at least it's proportional to the current squared instead of a constant loss...

In the mean time you can use a copper busbar if you have one on hand, it should act as a passable heatsink.

 

[Craig]

You can, but the right thing to have would be a proper terminal on the SSR because here you lose a lot of power (which we want to avoid by using a SSR, so that's kind of counter productive...), well at least it's proportional to the current squared instead of a constant loss...

In the mean time you can use a copper busbar if you have one on hand, it should act as a passable heatsink.

Yes I guess any heat would be a loss of energy. I will talk to manufacture about enlarging connections.

Would a standard relay have same problem?

 

[BiduleOhm]

As far as I saw they have a lot beefier terminals (even the cheap ones) so that shouldn't be a problem on those.

Also, I forgot to mention it earlier but soldered connections and heat cycling don't go together very well, so even if you heatsink the external terminal the internal connection will likely still be a problem.

 

[Steve_S]

@Craig I'd like to suggest you put this Thread into your Signature, it's pretty important IMO.

 

[boondox]

UPDATE.
i was able to put together a 140 Amp load for about 10 minutes. The terminal where the load cable leads the relay heated up to about 170F.
The relay itself stayed about 50 degrees cooler. Next test i will try and record all the portions of the relay with the thermometer. This is the 240Amp relay.
Im thinking the terminal heat would be the same on the larger 500 amp relay.
Thermometer video

That is disappointing. As you were just over 1/2 of its rating and only for ten minutes. If all of your connections were tight and right that relay is pretty much a failure IMO.

 

[Craig]

That is disappointing. As you were just over 1/2 of its rating and only for ten minutes. If all of your connections were tight and right that relay is pretty much a failure IMO.

I'm not sure it is a failure yet the manufacturer is going to make me new ones with larger terminals. I also am going to try a different connection. The relay itself actually worked well. We figured early on that we would need a relay rated at 2x the max load that you would generally be using.

 

[Craig]

I think i have a standard solenoid relay i will try as well to see what heat it generates at high amps.

I'm not saying these are ready for prime time yet dont get me wrong.

Im just more of the glass is half full and its darn good whiskey inside.

 

[boondox]

I think i have a standard solenoid relay i will try as well to see what heat it generates at high amps.

I'm not saying these are ready for prime time yet dont get me wrong.

Im just more of the glass is half full and its darn good whiskey inside.

Well, I do like a half glass of darn good whiskey...

Lets us know how it turns out. Hard to come up with a big load that you can run for long periods. I'd like to see the temperature after an hour of run. Wish I hadn't already recycled my last battery bank, I could pour power at them for as long as I liked.

 

[Craig]

Well, I do like a half glass of darn good whiskey...

Lets us know how it turns out. Hard to come up with a big load that you can run for long periods. I'd like to see the temperature after an hour of run. Wish I hadn't already recycled my last battery bank, I could pour power at them for as long as I liked.

LOL yes it is hard and running 150 Amps for an hour kills batteries in a hurry But today there is good sun so I will try and make some smoke.

 

[BiduleOhm]

There's no point to run it for hours if the steady state is attained after 15 min for example. You can measure the temp every 5 min and when the last two values are only a few °C appart then you're at steady state so you can stop here.

We figured early on that we would need a relay rated at 2x the max load that you would generally be using.

Yeah but that's not normal. If you buy a x A relay you should be able to use it at x A without any failures (NB: it's not a good design practice to do that as you should leave some margin).

 

[boondox]

There's no point to run it for hours if the steady state is attained after 15 min for example. You can measure the temp every 5 min and when the last two values are only a few °C appart then you're at steady state so you can stop here.
Yeah but that's not normal. If you buy a x A relay you should be able to use it at x A without any failures (NB: it's not a good design practice to do that as you should leave some margin).

It is probably true that it will reach max temperature in 15 minutes but I do wonder about a slow avalanche. The resistance gets a little higher, the part gets a little warmer so the resistance gets a little higher... It is also about reliability testing so one gets a better idea of how much de-rating is wise. Plus I always like an opportunity to push something until it either lets out the smoke or proves itself to be a champ.

 

[Craig]

There's no point to run it for hours if the steady state is attained after 15 min for example. You can measure the temp every 5 min and when the last two values are only a few °C appart then you're at steady state so you can stop here.



Yeah but that's not normal. If you buy a x A relay you should be able to use it at x A without any failures (NB: it's not a good design practice to do that as you should leave some margin).

I am doing this knowing that a SSR relay is not necessarily made for our use case so I am willing to give some leeway. I have spoken with manufacturer and they are going to see about making ones with larger terminals. They seem to be interested as they keep asking for my test results.

 

[BiduleOhm]

It is probably true that it will reach max temperature in 15 minutes but I do wonder about a slow avalanche. The resistance gets a little higher, the part gets a little warmer so the resistance gets a little higher... It is also about reliability testing so one gets a better idea of how much de-rating is wise. Plus I always like an opportunity to push something until it either lets out the smoke or proves itself to be a champ.

If thermal runaway would happen, then it would in seconds once the critical temp is reached.

Yes, it's always a good idea to test it fully, but right now it struggle to pass a short test so there's no point in him wasting energy to test it for hours until he get a newer version with better terminals.

I am doing this knowing that a SSR relay is not necessarily made for our use case so I am willing to give some law at.

Huh? anything within the voltage and current specs of the relay is a proper use case of the relay, and our usage qualifies for that.

 

[Craig]

If thermal runaway would happen, then it would in seconds once the critical temp is reached.

Yes, it's always a good idea to test it fully, but right now it struggle to pass a short test so there's no point in him wasting energy to test it for hours until he get a newer version with better terminals.



Huh? anything within the voltage and current specs of the relay is a proper use case of the relay, and our usage qualifies for that.

I thought the reason SSR were not recommended is they are made for rapid switching and not long continuous current .

But yes they should conform to their specifications I do agree.

 

[BiduleOhm]

That's just an inherent advantage of their design. Compared to a mechanical relay they are a lot faster to switch, handle an nearly infinite amount of cycles and are silent when switching, but they are not made specifically like that, it's just how they work.

 

[Craig]

One other thing is how many of us will ever have a 180 Amp load for 20 minutes in real life. even with a 300Ah battery that would be pretty stressful.

Does anybody have thoughts on what a "Normal" continuous draw rate would be for most 24V systems.

I mean i found it very hard to muster 180 amps unless i hooked up 3 Water heating elements. To 2 different Inverters.

I do want to know the devices limits I'm just wondering what real life usage will be.

 

[BiduleOhm]

Well my peak usage (which can last for a few dozens of minutes) would be something like 8 kW but in 48 V so that's 167 A.

180 A isn't unrealistic, especially with 24 V as that's only 4.3 kW.

And you need to add at least 10 % losses in the inverter on top of that.

 

[Steve_S]

One other thing is how many of us will ever have a 180 Amp load for 20 minutes in real life. even with a 300Ah battery that would be pretty stressful.

Does anybody have thoughts on what a "Normal" continuous draw rate would be for most 24V systems.

I mean i found it very hard to muster 180 amps unless i hooked up 3 Water heating elements. To 2 different Inverters.

I do want to know the devices limits I'm just wondering what real life usage will be.

First, I would like to say THANKS for the hard work.
Second, I would say you are, as a byproduct, also stress testing your new cells and packs so you might as well monitor them as well. Two Testing processes with one stone...

Normal Load on a 24V system, oh that's precious (meant ironically), we ALL have differences there. I am 24VDC based with a 4Kw Inverter, so nothing crazy or outrageous and likely pretty close to a larger portion of the average solar users & offgridders… BUT, even as I sit here right now I am using about 6.5A off the battery, if the fridge kicks on 10.2A. Now if I turn on the Coffee Maker I'm pulling 60A off the batteries, another 85A if I turn on the 1200W Inverter Microwave. Now I built this place and planned for overall low power consumption, even my deep well pump (Grundfos SQ-5 120V Soft Start) maxes out at 1100W (read from Inverter Display) when it reaches 45-PSI cutoff, and it's pushing up 260 feet and filling a 50 gal pressure tank and then pushing another 75' to Cabin.

I have seen higher when I plug in the Air Compressor (20 gal 2 stage it's mean @ 120V/20A) but I don't recall the actual Amps but it varies if tank is low pressure or if there is air in the tank which pushes the start amps way up. I don't put the compressor on my Solar if I need it for actual real work for hours, then I run it with a Generator I have, same with the Mig Welder, I would NEVER put that monster on my solar system, not even as a test ! I suspect the Mig might push the numbers pretty high and my Inverter Can handle it but I don't feel abusive towards my equipment so, I'll never know.

So what is average ? I think it is quite relative to the individual and what / how they use their power. As an off gridder I am very aware of every light, every watt and every amp, never leave lights on, power bars to prevent energy vampires which get turned off when not needed and so on.

 

[Craig]

Yes I figured that would be the case. That everyone is different.

Ok so I need to compare relays at about 200 amps I think I can do that.

My LTO bank is 70Ah so not only will I be testing realys I will be testing the Cells at a 3C rate. Problem is that only gives me 20 minutes. But I think it's enough until my machinist gets me my new bus bars for my 120Ah system. Giving me a total of 190 Ah.