Faulty Samlex 3kw Inverter?

[sturmgewehr762]

I recently installed a 3kw Samlex (NTX-3000 12) in my cargo trailer and am having issues with the inverter triggering the short circuit protection one time, every time it is switched on.

The scenario is that everything is wired in via a Lynx distributor, battery is never disconnected, power always remains available to the inverter. Should the capacitors in the inverter remain charged in this scenario even if the inverter is switched "off" but remains connected to the battery?

What is happening here is that every time I turn on, if it has been turned off for a few minutes, the inverter it triggers the short circuit protection in the JK BMS. Then, when I force the BMS back on via the "emergency" mode, the inverter powers up fine and functions normally, I'm assuming because it pre-charged enough on the first power on attempt.

I'm feeling like there's an issue with the inverter but wanted to get some additional feedback here to see if I am missing anything.

Thanks!


Edited post to correct model number of my inverter.

 

[Steve_S]

I believe the PST's have a Jumper / Switch for grounding... That by default is set for grounding from AC Line, (not sure, I use an EVO) so check that, if wrong it will pop CGFI everytime.

I do believe that if just turned off while connected to BATT's the capacitors remain charged but I don't think for long, they do bleed off.
The GOTCHA ! If Caps are discharged & you turn it on the Inrush is heavy and CAN trip the BMS into thinking it's a short and cutoff. A Precharge setup with resistor is the solution... The upside if you have more than 1 battery in parallel, 2 or more can usually take that with no issues whatsoever.

 

[sturmgewehr762]

I believe the PST's have a Jumper / Switch for grounding... That by default is set for grounding from AC Line, (not sure, I use an EVO) so check that, if wrong it will pop CGFI everytime.

I do believe that if just turned off while connected to BATT's the capacitors remain charged but I don't think for long, they do bleed off.
The GOTCHA ! If Caps are discharged & you turn it on the Inrush is heavy and CAN trip the BMS into thinking it's a short and cutoff. A Precharge setup with resistor is the solution... The upside if you have more than 1 battery in parallel, 2 or more can usually take that with no issues whatsoever.

Thanks Steve, The piece of this I'm unable to reconcile in my head is, what purpose does the pre-charge resistor serve if power is never disconnected in the first place? The resistor circuit would simply be in parallel to a circuit that is already live.

I will read up on the jumper and see if there is something there that I need to change, I appreciate the feedback.

Thanks!

 

[sturmgewehr762]

The upside if you have more than 1 battery in parallel, 2 or more can usually take that with no issues whatsoever.

Maybe this problem goes away then when I have my final batteries in place. Right now I'm using a portable 180ah DIY LiFePO4 (60ah cells in 4s3p configuration) with a 200a JK BMS but I'm in the process of building out two EVE 4S 304ah packs that will be running in parallel, each with a dedicated 200a JK BMS.

 

[Steve_S]

If the inverter is Running and hits Low Volt Cutoff it won't dump the capacitors but they will eventually drain if battery cuts off. If the batteries cutoff before the inverter, the capacitors are dumped and the inverter stops.

60AH cells even in 3P have their limits and the BMS rules and it won't take what it sees as a short. 2x 304's with 200A BMS won't have any stress with the CAPS.

 

[sturmgewehr762]

If the inverter is Running and hits Low Volt Cutoff it won't dump the capacitors but they will eventually drain if battery cuts off. If the batteries cutoff before the inverter, the capacitors are dumped and the inverter stops.

60AH cells even in 3P have their limits and the BMS rules and it won't take what it sees as a short. 2x 304's with 200A BMS won't have any stress with the CAPS.

Thanks Steve,

The thing that I am surprised about here and apparently didn't realize, is that the capacitors will drain if the inverter is off but still connected to batteries. I ended up leaving the inverter turned on all weekend when we were out camping so it didn't trigger the short circuit protection on the BMS, I was very disappointed that I had to do that.

 

[chrisski]

I have the Samlex PST 3000-24 volt version on a 560 ah battery bank.

I have none of the issues you mention. It makes a sound every time I turn it on, but nothing wrong with 200 amps of BMS

1) Did you connect the frame ground to the trailer?

2) What is the total ratings on the BMS? You could expect the inverter to pull in excess of 350 amps when maxes out.

I don’t think the inverter has a huge surge on start up provided the battery is powered on. For the lithium batteries, prior to installing the pre charge resistor, when I turned the battery power on, I could see the spark from inside the Blue Sea sealed switch.

 

[Texas-Mark]

The thing that I am surprised about here and apparently didn't realize, is that the capacitors will drain if the inverter is off but still connected to batteries.

I'm not understanding this either. Every inverter I have owned keeps the caps charged as long as it's connected to the battery. However, if the BMS trips and the inverter is on, then I can see the caps bleeding off nearly instantly. But that does not seem to be your issue.

 

[sturmgewehr762]

I have the Samlex PST 3000-24 volt version on a 560 ah battery bank.

I have none of the issues you mention. It makes a sound every time I turn it on, but nothing wrong with 200 amps of BMS

1) Did you connect the frame ground to the trailer?

Yes, based on the manual, earth ground is via the negative input on the inverter. That connects to the Lynx distributor which I have properly grounded to the frame of the trailer via the center grounding lug.

2) What is the total ratings on the BMS? You could expect the inverter to pull in excess of 350 amps when maxes out.

BMS is a 200 amp JK BMS.

I've tried to be quite meticulous about this install so this has thrown me a curve ball for sure.

 

[sturmgewehr762]

I'm not understanding this either. Every inverter I have owned keeps the caps charged as long as it's connected to the battery. However, if the BMS trips and the inverter is on, then I can see the caps bleeding off nearly instantly. But that does not seem to be your issue.

Yes that is correct, if I turn the inverter off for a few minutes, leave everything in place and connected, then turn the inverter back on again five minutes later, my BMS shuts down due to short circuit protection. Then, when I force it back on, the inverter functions normally.

 

[TacomaJoe]

What sort of numbers do you have on the BMS settings for over current and short current?