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Cutoff Solenoids - what works and what doesn't.

willo

Solar Enthusiast
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Apr 8, 2020
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I've gone through a pile of solenoids in my safety cutoff quests. Here's my list of successes and failures.
Specifically, I've been working with Victron Multiplus and Quattro Inverters on 24v LifePO4 packs.
On the BMS side, I've been using an Electrodacus SBMS0 and an OrionJR 2 BMS.

The average fet based BMS takes care of disconnects, so if you're using those, this isn't even a thing unless you wanted an extra remote cutoff.

What works?
The Tyco Electronics EV200AAANA. (Right now Battery Hookup has these for $30 which is a stellar price.) New these are like $150 parts.
You can get these new from shops like Mouser or Digi-key.
This must be the version with the Economizer. If you buy them from BH, bench test for your own sanity and safety. I bought four and all bench tested fine.
With the Economizer, there's a very short surge to energize the coil and then the load drops to around 2 Watts or less.
Considering the switching involved, that's a fantastic number.
The Economizer is a big deal on these things. When I used the same contactor without the economizer, it caused my precharge controller to start smoking.
I didn't think to verify the load of the thing at the time...

There are SEVERAL models of the tyco contactors. Aside from matching your voltage application, you really, really, really want the 'economizer'. You can tell by looking at the backside. There will be a small backpack containing it. If there are just a couple of mounting posts, it doesn't have it and you want to avoid those. Example:
1668603858593.png
This one has the economizer.

Pre-charging:
Pre-charge is the deal where Wil grabs a resistor and pre-charges the capacitors in his inverter before connecting the leads. This is to avoid the pretty sparks and contact welding. If that happens inside a contactor, it'll either damage it enough inside to prevent contact... or it'll weld closed.
I shorted that explanation - there's a huge inrush surge as those capacitors suck up enough juice the charge, kind of like when a dry sponge finally starts soaking up water. That surge results in a high amperage flow which creates the sparks/welding current.

If you have a BMS that supports pre-charge, great. If not, you can either home brew one using an arduino and some relays or just buy a
REC BMS Pre-Charge controller. I did the latter for my marine build and once I got the right contactor for the job, this tested great.
Price is a little high for the REC but this is to protect a significant investment - my boat and my batteries.
You could also build a simple R/C circuit if you prefer old school timer circuits...
The REC controller looks for a positive input, so if your BMS can be adjusted to do so, it's easy. Otherwise you'll want to stack an optoisolator in front of it.
It appears that REC has released a new 3.0 version that's designed to deal with latching contactors. It's more money than the 2.0 version I've been using.

What didn't work:
EV200A1ANA
Basically the same contactor as above but without the economizer. It drew too much power and after it tried to smoke the pre-charge controller I managed to weld the contacts in four test cycles. It was a sad day as I'd bought that one brand new. I was surprised at how fast it managed to weld shut. I bought this before learning about the economizer bits.

GX14-PA3
Gigavac 12/24v constant duty contactors. These can be had cheap as forklift maintenance pulls. They get replaced in lots of four after so many hours of usage in a given fork lift. These work but they pull a lot of current. They pull nearly 100w when cranked up and then sort of fall off on the load. They also start getting hot to the touch over time. Enough so that while they didn't fail, I did remove them. I think these are better suited for temporary load switching based on the heat, rather than an on 24x7 role. Enable a high current winch line for half an hour? Sure. These were ok with the pre-charge controller but still pull more power than I'd like. The one on my bench right now just settled into a 50w draw and it's already uncomfortable to the touch after ten minutes just from the actuator coil.

What I didn't test:
The holy grail here is a latching contactor. Those only require power for switching and then stop drawing power. However your controller must be aware of this. Looks like the new 3.0 REC pre-charge controllers do support these, which is cool.

Hope this helps!
 
Im pretty annoyed at Evolve and the "package" they sold me for my Orion BMS2Jr. Now based on what I've seen so far the Orion itself is great, but Evolve's "package" itself just isnt complete. They shipped a gigavac contactor and that thing just cannot be connected directly to the Orion as the max current draw it can support on its contactor enable output is 175ma. The good thing about the contactor they shipped (GX23B) is that it has an excellent built in economizer and also built in coil suppression (no external diodes required). I even got a Pololu relay pack, to use between the BMS and the Gigavac but then even that would require some additional resistor & fet/transistor components. So screw it just got a SSR on order. Its very pricey but makes everything stupid simple and only draws < 50ma of current.

ETA: so i've just recently learned a lot more, good thing too... anyhow I cannot find an appropriate (read: 200amp) SSR to replace the contactor altogether, the problem is you need either a DC-based-output SSR that has 2 mosfets on the output or a "random start" AC-based-output SSR (which also has 2 MOSFETS on the output). But if its an AC-based one it HAS to be "random" it cannot be zero crossing or other types. So anyhow I did end up not using the pololu or other devices and just using much smaller SSR in-between the Orion and the Gigavac as a current amplification device and now the contactor is doing like I want it.
 
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I can also share some successes and failures with the cut off of my systems.

Successes: I used Zeva BMS with a Gigavac GV200 relay (with economizer) in the past with sucess and I currently use a Chargery BMS16 with a Durakool DEVR20 relay (with economizer).
Failure: Chargery BMS16 with a Panasonic AEV140 relay. After few weeks of use I tested my system and I remark that the relay don't open. Tried to find BMS fault, but it was the relay, this one was weld :oops:
It was shocking considering it is the last security before a potential battery fire.
I was able to unweld it by putting it few hammer shot, but it weld another time, so it now for the garbage.
 
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