Hi all, I commissioned a 24V 120Ah DIY lifepo4 battery. There was a short circuit when the relay of the BMS made contact with the cells and now the charge switches keeps on switching on and off when the inverter is connected. Could it be that the relay is malfunctioning or there's still hope for the this BMS? How can I resolve this issue? 

@Tim003 

Please switch off switch function and check. Another thing what inverter are you using? Are the parameters correct on the BMS?

Edited January 5, 20232 yr by Raj35

1 hour ago, Raj35 said:

@Tim003 

Please switch off switch function and check. Another thing what inverter are you using? Are the parameters correct on the BMS?

I did try to switch off the switching function but it is still toggling, I'm using default BMS settings and the inverter is RCT 3kva Vmiii. 

Talking about this particular inverter. I connected earth directly from the earth spike to the inverter body, the earth leakage trips when I press the test button but does not trip when I use plug socket tester (even though it indicates that everything is connected correctly). Does this inverter require bonding of earth and output neutral? Please let note this inverter is used in an off-grid environment. 

Edited January 5, 20232 yr by Tim003
Spelling, more info.

Please note that the test button on the E/L is an internal test and doesn't test if the sockets or lights will trip it. This must be done with a plug type tester.

1 hour ago, Jacques Ester said:

Please note that the test button on the E/L is an internal test and doesn't test if the sockets or lights will trip it. This must be done with a plug type tester.

Yes I used that plug tester and it's not tripping. There's 230V between Live and Neutral, 130V between Live and Earth, 100V between Neutral and Earth. I strongly believe Neutral-Earth bonding is required. 

Your earth should be to your home DB earth busbar.  Not an earth spike. 

 

I disassembled the battery pack and rebuilt it, the charging switch the app is no longer toggling. I connected PV to 24V RCT inverter but it's not charging the battery even though it reads the PV voltage. The battery happily charges with a separate solar charge controller. What are the recommended settings for this kind of inverter for charging lifepo4 batteries? 

3 minutes ago, Steve87 said:

Your earth should be to your home DB earth busbar.  Not an earth spike. 

 

Isn't that the earth from the DB is also coming from the earth spike? 

9 minutes ago, Tim003 said:

Isn't that the earth from the DB is also coming from the earth spike? 

No, the earth from the DB is tied to the neautral at substation or ODU. Should be DB earth as or if you have a split DB as the earth leakage will not activate. Correct me if I'm wrong. 

33 minutes ago, Tim003 said:

I disassembled the battery pack and rebuilt it, the charging switch the app is no longer toggling. I connected PV to 24V RCT inverter but it's not charging the battery even though it reads the PV voltage. The battery happily charges with a separate solar charge controller. What are the recommended settings for this kind of inverter for charging lifepo4 batteries? 

@Tim003 use amg settings cut off 25v and charge 27.6v should be fine if you have a 8s configuration 

Edited January 5, 20232 yr by Raj35

8 minutes ago, Raj35 said:

No, the earth from the DB is tied to the neautral at substation or ODU. Should be DB earth as or if you have a split DB as the earth leakage will not activate. Correct me if I'm wrong. 

It's an off-grid system. I had a earth and Neutral bonding with the previous 12v inverter and the earth leakage was working fine but removed the connections as I thought the RCT has internal bonding which it clearly doesn't have. Just to remind myself, neutral of inverter will go to the earth spike, neutral from the spike+inverter live goes to main switch,then to earth eakage. Earth from the spike goes to inverter earth, correct? 

This is how I did it previously with a 12V inverter. 

1 hour ago, Tim003 said:

Isn't that the earth from the DB is also coming from the earth spike? 

Yes it does. But the source of your AC input must be the same source of Earthing. Why go to the Earth spike when the DB is in closer proximity or maybe your site is different to what I am assuming. The RCT has the Neutral to Earth relay

 built in if it's the Voltronics type of inverter. If it doesn't then there is a fault in the internal circuitry. 

3 minutes ago, Steve87 said:

Yes it does. But the source of your AC input must be the same source of Earthing. Why go to the Earth spike when the DB is in closer proximity or maybe your site is different to what I am assuming. The RCT has the Neutral to Earth relay

 built in if it's the Voltronics type of inverter. If it doesn't then there is a fault in the internal circuitry. 

I was surprised to read that the known RCT does not do the E to N bond as my no name brand clone does it correctly. 

4 hours ago, Steve87 said:

Yes it does. But the source of your AC input must be the same source of Earthing. Why go to the Earth spike when the DB is in closer proximity or maybe your site is different to what I am assuming. The RCT has the Neutral to Earth relay

 built in if it's the Voltronics type of inverter. If it doesn't then there is a fault in the internal circuitry. 

Thanks for this info, I will double check my connections. My inverter and earth connections are made inside the ceiling, goes via trunking into the inverter. The same earth connection goes to the DB and earth spike. It's good to know that external bonding is not required. 

5 hours ago, Raj35 said:

@Tim003 use amg settings cut off 25v and charge 27.6v should be fine if you have a 8s configuration 

Thanks, I will try this. What should be settings for program 13?

 

6 hours ago, Tim003 said:

Thanks, I will try this. What should be settings for program 13?

 

If it's like the Axpert the 40amp should be good.

 

 

 

 

Please help, my inverter is not charging batteries but they are charging with a separate charger. 

And how do I solve the earth leakage problem? 

Edited January 6, 20232 yr by Tim003

57 minutes ago, Tim003 said:

Please help, my inverter is not charging batteries but they are charging with a separate charger. 

I just realized that my inverter's MPPT minimum input is 120V, I only have two Canadian 360W panels in parallel with Vmp of 39.6V, therefore I have insufficient solar panels. Luckily I have an external MPPT that I will use until we buy additional solar panels. 

4 hours ago, Tim003 said:

I just realized that my inverter's MPPT minimum input is 120V, I only have two Canadian 360W panels in parallel with Vmp of 39.6V, therefore I have insufficient solar panels. Luckily I have an external MPPT that I will use until we buy additional solar panels. 

Even when connected in series the voltage would be too low to start MPPT as you indicated. External MPPT should work just as well as the inverter MPPT. 

14 hours ago, Tim003 said:

And how do I solve the earth leakage problem? 

I resolved this by connecting E and inverter output N together in the DB, when I remove the bond, the socket earth tester doesn't trip; perhaps it's not all Axpert/RCT inverters that have an internal bonding. 

On 2023/01/05 at 5:30 PM, Raj35 said:

No, the earth from the DB is tied to the neautral at substation or ODU. Should be DB earth as or if you have a split DB as the earth leakage will not activate. Correct me if I'm wrong. 

Could be wrong here but when we built our house our Electrian had to put in a ground spike between db and sub station. I think this is required for every house. 

2 hours ago, sunset1 said:

Could be wrong here but when we built our house our Electrian had to put in a ground spike between db and sub station. I think this is required for every house. 

Yes that is correct, but when wiring the inverter it should go to DB first.