Junctek shunt relay operation

[Ucatchmydrift]

Hi, ive just ordered a junctek kg140f.

https://m.aliexpress.com/item/1005003245578434.html

(400amp version without the lcd screen as will only be using it via Bluetooth)

I noticed on a youtube video someone mentioning that it has relay control based on different situations occuring, such as over or under voltage protection.

I was wondering if anyone has used this function? And if so, do you know if i could use it to switch on an external relay when the battery bank (24v lifepo4) drops to a certain voltage, then switches the relay off when the battery voltage gets to or goes over a certain voltage?

Reason im asking is:

I have an epever all in one inverter that is connected to the grid permanently to allow a pass through function if i run out of battery and there is no solar available, which is great, accept for two things.

1. For some reason it draws a continuous 10w from the grid 24/7. - not much i know, but annoying, so id like to use the relay control to activate a relay/contactors to connect the grid power only when the battery gets low, then disconnect once it has been charged to a certain voltage.

2. All in one inverters seem to draw about 300w when using grid power - this seems crazy, but it does seem to be true (ive checked using a ac clamp meter), and there is another thread on here discussing the issue with growatt all in ones too. - not sure why im stating this, just having a moan. Would just be interesting to know why. Luckily it will only be using grid power at cheap rate overnight in winter. Most of the year it wont be being used at all.

Also, does anyone have the manual for this shunt? As the official link does not work for me...

Thanks ???

 

[diegofaral]

Hey Ucatchmydrift,

I have bought a similar junktek recently (100A model) and I am wondering the same question that you had.

I think you can definetely use the relay function to use it with an external relay

did you try it?

I am wondering what type of relay shoud I buy, is it normal close or open?
There are some 100A, 12V DC to DC relays normal close in the market but they say the can produce a lot of heat when the current goes over 60A, so I am not sure if it is a good idea to try this option in my small electrical system in my van.

I am attaching the manual, just in case you still need it.
Cheers

 

[Ucatchmydrift]

Hey Ucatchmydrift,

I have bought a similar junktek recently (100A model) and I am wondering the same question that you had.

I think you can definetely use the relay function to use it with an external relay

did you try it?

I am wondering what type of relay shoud I buy, is it normal close or open?
There are some 100A, 12V DC to DC relays normal close in the market but they say the can produce a lot of heat when the current goes over 60A, so I am not sure if it is a good idea to try this option in my small electrical system in my van.

I am attaching the manual, just in case you still need it.
Cheers

Hi, yes i have tried it and it does work.. It sounds like i may be using it for a differnt reason to you, as im using it to switch a 240v ac circuit, and you want to switch a dc circuit. I bought one of these solid state relays:

diymore Solid State Relay Module 25A SSR-25DA Input 3-32VDC,Output 24-380VAC https://amzn.eu/d/bLZ7CCs

I have the shunt wired to the dc side of the relay, and a wall plug going to the ac side. When the shunt activates the dc side, this allows current to then pass throght the ac side which then activates a contactor that then allows current to flow to my inverter giving it access to grid power which will then automatically start charging my battery banks.
Unfortunately, when testing this out, i left it all wired up, and switched the switch on the back of the shunt back to its original position, and there was a puff of smoke from within the shunt and i fried the relay circuitry! ? (so disconnect everything when switching that switch!)
I think this happened as i had not unplugged the external power supply to the shut and it was also still plugged into my battery banks to power it like normal. (when using the relay feature it needs external power, i used an old car battery to test- but you can just use your lifepo4's assuming they are the voltage of the relay you choose). The rest of the shunt operation is still fine though.

I have another shunt delivered the other day (which i needed for my second battery bank anyway) and am about to set it all up today.. Only thing is, im not sure the software on the app will then switch off the relay if one of the other conditions is met in the app (for example high voltage), so you have to switch it off in the app manually. In my case, as its just for emergency charging, this would be ok for me.
Like you say, you may find it hard and expensive to find a relay that can switch a high current dc circuit i think due to dc circuits creating an arc on the contacts meaning they have to be very well made to cope with this (im not sure how much heat they would generate, but if they are capable of 100a and you are just using say 50a, im sure that would be ok with regards to the amount of heat they produce, but im no expert!)

As far as the type of the relay goes (normally open/closed), it doesnt matter as in the app, you can press the relay button and tell it if the relay is normally open or closed..

 

[diegofaral]

Hey,

Thanks for the reply, it is very helpful. I think in my case it is not very useful to get a DC relay to protect my battery.
I want to design my system so I can load 100amps max eventually from the battery and a Relay with those characteristics is not designed for a small compartment covered with wood like in my case. It makes more sense to protect the Inverter from a big load and monitor the battery so It does not go under 10.5V. As that was my first concern, to have an automatic device not to discharge my battery in excess.

About your concern, I think you can set a timer in the app, after the software triggers an alarm and activates the relay after some specific time that you can configure, it deactivates the relay automatically . I have not tried it yet, but I have seen some videos of that functionality.

I may buy a cheap relay of 20A, just to see how ir works before I install my power system.

 

[Ucatchmydrift]

Hey,

Thanks for the reply, it is very helpful. I think in my case it is not very useful to get a DC relay to protect my battery.
I want to design my system so I can load 100amps max eventually from the battery and a Relay with those characteristics is not designed for a small compartment covered with wood like in my case. It makes more sense to protect the Inverter from a big load and monitor the battery so It does not go under 10.5V. As that was my first concern, to have an automatic device not to discharge my battery in excess.

About your concern, I think you can set a timer in the app, after the software triggers an alarm and activates the relay after some specific time that you can configure, it deactivates the relay automatically . I have not tried it yet, but I have seen some videos of that functionality.

I may buy a cheap relay of 20A, just to see how ir works before I install my power system.

Yes unfortunately the timer only allows for up to 99 seconds ?..
The app will also trigger a relay based on current, so you could protect your circuit using the relay based on that, but you would obviously still need a high amp relay. Could also protect it all with a class t fuse like this:

Bussmann 125 Amp HRC Fuse / Fuselink DD125 125a Bs88 for sale online | eBay

Find many great new & used options and get the best deals for Bussmann 125 Amp HRC Fuse / Fuselink DD125 125a Bs88 at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

But that doesnt help i guess if your worried about the heat from the relay, but i wouldnt have thought it would produce enough heat to cause a fire?

 

[diegofaral]

Yes unfortunately the timer only allows for up to 99 seconds ?..
The app will also trigger a relay based on current, so you could protect your circuit using the relay based on that, but you would obviously still need a high amp relay. Could also protect it all with a class t fuse like this:

Bussmann 125 Amp HRC Fuse / Fuselink DD125 125a Bs88 for sale online | eBay

Find many great new & used options and get the best deals for Bussmann 125 Amp HRC Fuse / Fuselink DD125 125a Bs88 at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

But that doesnt help i guess if your worried about the heat from the relay, but i wouldnt have thought it would produce enough heat to cause a fire?

Well I found this relay:

Link

That they usually sell them with theese kind of heat sink


I Think they can produce a lot of heat, not sure if they can start a fire but I do not want to try.
Anyway, I also dont know if this solid state relay is bidirectional ( charge-discharge battery) as they reccomend to put the load in one of the extremities. I ended up to the conclusion that they are not designed for the use I want to give them.

Searching a bit more I found this other relay for protection the batterty that looks very interesting:

Link2

In the comments I read that the relay is Normal Open (NO) as most of the relays I found and I would like to be Normal Closed (NC) because of:

1) NO means that I have to close the relay in normal operation thus consuming power from the battery ( may be the control circuit consumes very low current not sure though)

2) If the relay was designed for normal operation open I am not sure what happens if you are constantly using it as closed, as current is going to flow all the time and may be it damages the device that was designed for being open in normal operation. Anyway with small currents I do not think this is a big issue, specially the relay I found that can manage up to 500A for a short period of time

 

[Rickey]

About this problem, I gave feedback to the technical staff of JUNCTEK. They said that they will modify a custom firmware recently, and change the protection recovery time to 0-99999 seconds, which can be adjusted. Enough charging time of the battery, and then close the discharge circuit.

 

[Rickey]

Yes unfortunately the timer only allows for up to 99 seconds ?..
The app will also trigger a relay based on current, so you could protect your circuit using the relay based on that, but you would obviously still need a high amp relay. Could also protect it all with a class t fuse like this:

Bussmann 125 Amp HRC Fuse / Fuselink DD125 125a Bs88 for sale online | eBay

Find many great new & used options and get the best deals for Bussmann 125 Amp HRC Fuse / Fuselink DD125 125a Bs88 at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

But that doesnt help i guess if your worried about the heat from the relay, but i wouldnt have thought it would produce enough heat to cause a fire?

Please brush the firmware first, open the mobile APP - After Sales (8610) - Firmware Update (526), and complete the firmware upgrade before exiting the mobile APP; The new firmware has increased the default protection and recovery time by 100 times, which was originally 99 seconds. After the upgrade, it still displays 99 seconds, but it has been increased by 100 times to 9900 seconds;

 

[Ucatchmydrift]

Please brush the firmware first, open the mobile APP - After Sales (8610) - Firmware Update (526), and complete the firmware upgrade before exiting the mobile APP; The new firmware has increased the default protection and recovery time by 100 times, which was originally 99 seconds. After the upgrade, it still displays 99 seconds, but it has been increased by 100 times to 9900 seconds;

Thats awsome, thank you ??. I didnt think of asking them about that.. I did ask them to add SOC as a way of activating the relay, but they just said they will forward my feedback, but that was weeks ago now.

But, now i can have it charge the batts for say, just an hour from the grid in an emergency, meaning it wont end up charging from the grid for hours unnecessarily by the time i get up or notice.. ??

Ive got a couple of wemos d1 minis, going to attempt getting the data from the shunts to home assistant next..

 

[Rickey]

I bought the KH140F,https://www.aliexpress.com/item/1005005293126063.html
which should be an upgraded version of the KG series. It has an audible alarm function, and you can know whether it is overvoltage or undervoltage without adding a relay.
The relay consumes about 0.25A of current in standby mode, so I no longer Relay

 

[Richard Vallee]

Hi
anny one has instructions on how to program the relay option so it closes the external relay when voltage get down let s say to 12,0 V and if possible shuts a second relay when voltage is back to 13,6 v.

The idea is to use this option with a dry relay to start the RV generator which essentially is a 2 wire dry switch operated from inside the RV ( Onan generator ) ... if it works it be a very cheap auto start.

Merci.