Shunt snapped and caused a fire🔥

[ConnerLabs]

The other ones had a resistance up to 24 mOhm . Am thinking the German company has been selling me used ones now...
Do they check these relays at battery hookup?

The TE Connectivity EV200 contactors are available from RS, Farnell, Mouser and Digikey but rather expensive.

Panasonic AEV series are somewhat cheaper.
https://www.digikey.co.uk/en/products/detail/panasonic-electric-works/255-AEVA1251-ND/13967865

With any of these contactors you have to be careful not to weld the contacts with excessive inrush current on closing. They stick closed and won’t open when you need them to. This is a common problem in high voltage EV world, I’m not sure how much of a problem it is at 48V. The fix is precharge, which a good contactor BMS should support.

If the contacts do weld, a few smacks with a hammer will sometimes free them, then you sell it on eBay and let the buyer wonder why the contact resistance is so high.

 

[Brucey]

That's the reason I'll only buy new ones at an official reseller. I won't compromise with the safety of our house.

Except looks like you might have got something used in your set of five "new". The battery hookup ones are cheap enough where you could potentially use two per battery for redundancy.

 

[Daddy Tanuki]

That's the reason I'll only buy new ones at an official reseller. I won't compromise with the safety of our house.

100% agreed, the plan I have for mine is a double redundant system and does not involve the house but an outbuilding that houses a hot water dump load so even if it welds shut all it will do is boil off some water and deplete my banks. There are redundancies there as well, they can only discharge while SOC is 80% or higher so worst that happens is my cells get dragged down to 80% and the other control systems kick in and stop it, if that happens I got a manual reset alarm that will notify me

 

[k490]

Not sure if you can have someone in US send you some of these, huge savings over new:

9-36v BMS Upgrade to 500a Relay+Fuse Kit

This kit includes a 500a relay and a 500a fuse. These were recovered from industrial battery modules. These are normally VERY EXPENSIVE online. If you have any project that needs a high current relay this is your chance to save some money. Make a cheap 30a BMS into a 500a BMS. This will work for...

batteryhookup.com

I might have to order one of these could use these for solar disconnect?

 

[robbob2112]

That's the reason I'll only buy new ones at an official reseller. I won't compromise with the safety of our house.

They are pulls... I've tested all 8 by opening and closing while measuring contact resistance... I've taken one to 120amps and repeatedly opened and closed it with no increase in contact resistance. Note - I didn't do it a hundred times, just 10 or so.

I might have to order one of these could use these for solar disconnect?

You could do that, but you would need a pair slaved together so you do both positive and negative at the same time. And I would put them in a metal box to protect them from the weather.

If you did this you could control it from any dry contact relay and the inverter or a RPi to throw it. They require very low current to keep them energized so they don't get very hot or drain your battery.

 

[Brucey]

I might have to order one of these could use these for solar disconnect?

Well theres a small power cost to using these, generally you'd reserve them for duty where you have hundreds of amps to deal with, i.e batteries.

 

[robbob2112]

Here is the datasheet including the second page that tells all the characteristics. With the economizer they only use 1.7w to stay connected.

If you equalize the voltage on both sides before turning it on, it has 50k cycles.

At the voltage and current we typically operate at they have 10k cycles in them when loaded. From reading they were apparently used to switch directions on a motor - i.e. reverse polarity using 4 of them connected so it would break then make the contacts with brief period in between.

If you want something better or that is new you can look for Albright brand contactors - the SW22, SW88, and others they make in different configurations. Those are intended as motor controls for forklifts, pallet jack, trolly trains, and the like. They have them grouped with bus bars to do just about anything you want but they are pricey new. You can get them used for 1/2 price. The really nice thing about most of the albright models is you can buy replacement conacts and rebuild them so you keep the case and everything else and just replace the copper contact plates with the hardend points in them.

 

[doubledutch]

They are pulls... I've tested all 8 by opening and closing while measuring contact resistance... I've taken one to 120amps and repeatedly opened and closed it with no increase in contact resistance. Note - I didn't do it a hundred times, just 10 or so.



You could do that, but you would need a pair slaved together so you do both positive and negative at the same time. And I would put them in a metal box to protect them from the weather.

If you did this you could control it from any dry contact relay and the inverter or a RPi to throw it. They require very low current to keep them energized so they don't get very hot or drain your battery.

How many milliOhms did you measure?

 

[robbob2112]

5 of them test at 0.3milliohms and 3 test at 3 milliohms.

 

[doubledutch]

Here is the datasheet including the second page that tells all the characteristics. With the economizer they only use 1.7w to stay connected.

If you equalize the voltage on both sides before turning it on, it has 50k cycles.

At the voltage and current we typically operate at they have 10k cycles in them when loaded. From reading they were apparently used to switch directions on a motor - i.e. reverse polarity using 4 of them connected so it would break then make the contacts with brief period in between.

If you want something better or that is new you can look for Albright brand contactors - the SW22, SW88, and others they make in different configurations. Those are intended as motor controls for forklifts, pallet jack, trolly trains, and the like. They have them grouped with bus bars to do just about anything you want but they are pricey new. You can get them used for 1/2 price. The really nice thing about most of the albright models is you can buy replacement conacts and rebuild them so you keep the case and everything else and just replace the copper contact plates with the hardend points in them.

I looked at the allbrand disconnects but these puppies use 11-15 Watts each, not so very economical...

 

[OffGridForGood]

Well theres a small power cost to using these, generally you'd reserve them for duty where you have hundreds of amps to deal with, i.e batteries.

Or a DIY RSD system LOL.

 

[robbob2112]

The continuous duty Albright contactor coil is 7 to 13 watts. Higher quality everything than the tyco contactor and they sell the parts to customize or build to order. They also have an economizer that can be added to make the load 1.4 to 2.6 watts. Or they have bistable latching ones that switch on an impulse signal and take zero watts to maintain.

The downside is they are expensive, the upside is they are repairable, $100 per set of contacts generally...$20 on aliexpress....wonder how long those would last.

What I may do is use the Tyco and monitor the swap to the Albright when I see an issue.

I suspect the inconsistent contact resistance is why they were pulled...can't trust them in a car like that.

 

[doubledutch]

Do you know if these contacts are in the open? The Tyco ones are vacuum contacts and safer when built into a battery compartment with venting EVE cells in worse case scenario.

Since I suspect we both are living in the land of the dutchies, could tou share a dealer where these can be bought?

 

[robbob2112]

You can get Albright contactors in a sealed casing for wind, rain, and explosive atmosphere.

They are manufactured in the UK so probably easy for you to order.

 

[OffGridForGood]

I might have to order one of these could use these for solar disconnect?

Well theres a small power cost to using these, generally you'd reserve them for duty where you have hundreds of amps to deal with, i.e batteries.

Maybe these would work for this battery back-up relay I have been pondering:
The basic idea: a failure mode of LFP packs is the BMS could fail to stop charging as a cell voltage passes the set point (say 3.60v)
Such a situation with many packs charged thousands of cycles seems enevitable.
The back-up system: - an Arduino monitors each cell voltage (ties into the sense wires) and if any one cell hits 3.65v it opens a relay (like this one we are discussing) for that pack and sends me an alert & lights a big red LED on the front of that pack.
Yes the arduino could also fail, but what is the probability of both failing at once.

Wondering about how to set up just one arduino to monitor All the packs, maybe some type of 16 pin connector built into each pack, for the sense voltages and another conductor for a keep-alive relay to each pack. It is just an idea. Maybe it would prevent a pack from run-away voltage failure.
With a system that opens a relay built into each pack, we could have other triggers - like heat - to also open the relays and automatically shut down a system.

 

[Daddy Tanuki]

Maybe these would work for this battery back-up relay I have been pondering:
The basic idea: a failure mode of LFP packs is the BMS could fail to stop charging as a cell voltage passes the set point (say 3.60v)
Such a situation with many packs charged thousands of cycles seems enevitable.
The back-up system: - an Arduino monitors each cell voltage (ties into the sense wires) and if any one cell hits 3.65v it opens a relay (like this one we are discussing) for that pack and sends me an alert & lights a big red LED on the front of that pack.
Yes the arduino could also fail, but what is the probability of both failing at once.

Wondering about how to set up just one arduino to monitor All the packs, maybe some type of 16 pin connector built into each pack, for the sense voltages and another conductor for a keep-alive relay to each pack. It is just an idea. Maybe it would prevent a pack from run-away voltage failure.
With a system that opens a relay built into each pack, we could have other triggers - like heat - to also open the relays and automatically shut down a system.

is that not basically what you buy a BMS for? seems to me if you can put together a system that actually works you could probably sell it. I am always in the market for something to play with as the currently available BMS's do not impress me one bit, I am just not an adurino jockey or code writer like some of you talented geeks.

 

[OffGridForGood]

is that not basically what you buy a BMS for? seems to me if you can put together a system that actually works you could probably sell it. I am always in the market for something to play with as the currently available BMS's do not impress me one bit, I am just not an adurino jockey or code writer like some of you talented geeks.

I am no IT guy either, but by grand-daughter and I worked on E-bike conversions (something to do together when she visits us) and this lead to getting a couple Arduino starter kits. - I highly recommend it, for under a hundred bucks, for fun and opening up opportunities to automate things around the property.

Yes a BMS's primary job is to provide the cell level protection, but just like the brakes on a car, we should have a back up system if the primary one fails.

 

[Hedges]

It will fail some day, and unless you are Watching the Watchers, you will never know.
Now you have no protection.

Smoke alarms are like that. So they are designed to beep as their battery gets low.

Your BMS should have a watchdog timer, so other monitors can aggregate status from one or more of your DIY BMS and report.

The BMS shouldn't open and hold open a relay in the event of failure. It should be fail-safe, hold relay closed while cell voltages are OK.

It likely polls multiple inputs with a mux, and state machine goes through each cell, updates state of relay as "open" or "closed".
You could have an electrical one-shot or some sort of limited time on relay circuit, so if your DIY BMS doesn't refresh relay in closed state periodically, it opens (dead-man switch.)

Some circuits are more reliable than others. FMEA, Failure Modes and Effects Analysis, asks questions like, "If this FET fails shorted, what will happen?" "What are the chances of FET failing shorted?" "If this resistor fails open, what will happen?" And, "If both failures happen simultaneously, what will happen?"

If you held the relay closed not with power from a FET, but power from a transformer/rectifier/capacitor, and if the DIY BMS had an Arduino that had to toggle state of output on/off for each pass through its polling loop, you then have AC to create DC to keep relay closed, and if firmware gets hung or FET fails shorted, power to relay is removed.

That reduces chance of most failures resulting in "fail deadly", but still has the relay contact welding issue.
A brute-force active backup could be crowbar to blow fuse. Any better ideas? Active Pyro fuse?

 

[OffGridForGood]

is that not basically what you buy a BMS for? seems to me if you can put together a system that actually works you could probably sell it. I am always in the market for something to play with as the currently available BMS's do not impress me one bit, I am just not an adurino jockey or code writer like some of you talented geeks.

I am no IT guy either, but my grand-daughter and I worked on E-bike conversions (something to do together when she visits us) and this lead to getting a couple Arduino starter kits. - I highly recommend it, for under a hundred bucks, for fun and opening up opportunities to automate things around the property.

Yes a BMS's primary job is to provide the cell level protection, but just like the brakes on a car, we should have a back up system if the primary one fails.

I bought a couple of those for playing with and I can say they are a pretty heavy duty piece of gear.

Do the relays you bought from battery hook-up need to operate at 9-36 volt? ie not 48-60 volt battery voltage?
this would be a pita for 16s pack, since it will mean buck converter to operate the relay voltage.

 

[Daddy Tanuki]

I am no IT guy either, but my grand-daughter and I worked on E-bike conversions (something to do together when she visits us) and this lead to getting a couple Arduino starter kits. - I highly recommend it, for under a hundred bucks, for fun and opening up opportunities to automate things around the property.

Yes a BMS's primary job is to provide the cell level protection, but just like the brakes on a car, we should have a back up system if the primary one fails.

Do the relays you bought from battery hook-up need to operate at 9-36 volt? ie not 48-60 volt battery voltage?
this would be a pita for 16s pack, since it will mean buck converter to operate the relay voltage.

Had me in a panic for a second there, . The trigger coil for the relay is 12-24 but the contacts are rated up to 900 volts at 500 amps according to battery hookup. That's DC power. I have plans for a dump load in mind for these relays. power will come from my inverter(s) output relay... it just cannot handle a lot of amps, 1 amp max. If it would handle more I would not need this.

 

[OffGridForGood]

The trigger coil for the relay is 12-24

Darn,
I was hoping to use the battery voltage (48-58) to run the coil to open/close the contacts.
Then again, could always use AC output to run a small transformer to control the relays, although it would be more efficient to run on DC with a buck converter.

power will come from my inverter(s) output relay... it just cannot handle a lot of amps, 1 amp max.

Does the 1 Amp run the relay ok? (ie will it peak over 1 Amp during closing the relay?)
I am considering buying a few of these relays, as the price seems unbeatable, and they could be handy for several things including dump loads as @Daddy Tanuki is doing.

 

[Hedges]

Then again, could always use AC output to run a small transformer to control the relays,

Which came first, the Chicken or the Egg?

This may work to keep the relays closed. But once they are open, where were you planning to find AC?

Your system will have to pull itself up by the bootraps.

 

[Daddy Tanuki]

Darn,
I was hoping to use the battery voltage (48-58) to run the coil to open/close the contacts.
Then again, could always use AC output to run a small transformer to control the relays, although it would be more efficient to run on DC with a buck converter.

Does the 1 Amp run the relay ok? (ie will it peak over 1 Amp during closing the relay?)
I am considering buying a few of these relays, as the price seems unbeatable, and they could be handy for several things including dump loads as @Daddy Tanuki is doing.

not sure, not to that stage of collecting bits and bobs yet, though i have several options to power this with. one is a laptop charging cord... cheap all over the place used, and reliable as can be.

Which came first, the Chicken or the Egg?



This may work to keep the relays closed. But once they are open, where were you planning to find AC?



Your system will have to pull itself up by the bootraps.

in my scenario, this is part of the control system for a second (cheap HF) inverter. the Magnums stay powered 24-7 this will be for the excess production sigineers that will dump to a water heater. I don't want them power hungry critters running 24-7 when not in use. to much idle power loss.

 

[OffGridForGood]

Which came first, the Chicken or the Egg?

This may work to keep the relays closed. But once they are open, where were you planning to find AC?

Your system will have to pull itself up by the bootraps.

I suspect the egg came first, from a very similar not quite a chicken parent. lol.
See the signature line below - there are always three separate systems available 12v, 24v and 48v that all produce 120v independently.

The main solar power plant has never been "off-line" in over three years now. only need to bootstrap it once? LOL
Besides, my thought is to build out the relays into each DIY battery pack one at a time. Power will always be available from all the other packs in the ESS during the installation. If I was really stuck, fire up the genset for starting current.

 

[OffGridForGood]

not sure, not to that stage of collecting bits and bobs yet, though i have several options to power this with. one is a laptop charging cord... cheap all over the place used, and reliable as can be.



in my scenario, this is part of the control system for a second (cheap HF) inverter. the Magnums stay powered 24-7 this will be for the excess production sigineers that will dump to a water heater. I don't want them power hungry critters running 24-7 when not in use. to much idle power loss.

okay I will try some, ordered on Battery Hookup - will see what these relays can do for me.