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:
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!
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:
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!