Install done, power up fail…..

[JTB321]

So, complete the install and come to power up off batteries to set up inverter. Two batteries each measure 13.2v as supplied, series connected giving 26.4v as expected. No AC mains or PV enabled. Closed power switch and one battery dies to <3v. Not a good start. Complete system is an LV2424 and relatively straight forward. now need to figure out if I have a faulty battery or it is just not fully charged. After three attempts the battery recovers to around 12.5v slowly. Going to call Shop Solar Kits and see what they think. Disappointing to say the least. Any one with suggestions or comments?
Cheers, John

 

[Vigo]

It may have something to do with the capcitor inrush to the inverter tripping the bms overcurrent protection.

Depends on what switch you mean. If it’s a battery disconnect switch that isolates battery from inverter, you would get inrush when you close that switch. Look up ‘precharge resistor’ or precharge circuit for context. If you just mean the power switch on the inverter that would not cause this as the inrush would have occurred when you connected battery to inverter, even if inverter was off.

 

[MisterSandals]

Closed power switch and one battery dies to <3v.

Can you post a pic of your battery, switch and wiring?

 

[timselectric]

Definitely BMS over current shut down, due to capacitor inrush.

 

[JTB321]

The switch I was referring to is the inverter on/off switch. Should be photos in the initial post showing the battery wiring. I’ll research the inrush issue, thanks.

 

[740GLE]

Glad your fuse held. What’s it’s rating? 200A?

The inrush should have happened when you connected the battery leads, did you check voltage at the DC terminals after you made connections and before flipping the switch?

 

[Doggydogworld]

Did you precharge the inverter caps when hooking up the battery?

 

[JTB321]

No inrush when battery connected to inverter. Only when I turn on the inverter power switch does one battery ‘die’. With the batteries connected I get the full 26.4v at the inverter terminals.

 

[MisterSandals]

Only when I turn on the inverter power switch does one battery ‘die’. With the batteries connected I get the full 26.4v at the inverter terminals.

So if you then switch the inverter off, the "dead" battery comes back to full voltage?

Are you sure all the loads are off (or disconnected) from the inverter?

 

[sunshine_eggo]

Did you fully charge each battery individually as a 12V and then again in parallel before placing in series?

 

[Hedges]

The switch I was referring to is the inverter on/off switch. Should be photos in the initial post showing the battery wiring. I’ll research the inrush issue, thanks.

I don't see anything like a 200A switch (that would complete circuit between batteries and inverter).
A little rocker switch, which signals to the inverter time to power on?

 

[JTB321]

Initial connecting of the batteries to the inverter showed no inrush/spark. Full battery voltage measured at inverter terminals. Closing the small inverter power switch causes the battery issue.
I did not charge the batteries before use, don’t have method to do so?
as per the photo, the AC input is not connected and thr are no loads on the AC output.
going to try contacting Shop Solar Kits this morning. Could be a faulty inverter. Nothing in the install instructions details needing to use the resistor current limit when the batteries are connected. I expected to see a spark but didn’t?

 

[MrM1]

The manuals of units like MPp and Growatt usually do not mention start up procedures or precharge resistors. I just got scolded on YouTube by a commenter who said "read the manual" (as if I didn't) when I was doing start up testing to develop a starter up sequence for my daughter.

Growatt literally takes 30 words in the manual to describe start up. And even though there is a power saver mode on the switch. It's not mentioned.

I'd precharge.

 

[MrM1]

InRush can do some interesting things to a BMS. Can you access the BMS via Bluetooth and see if you have error codes in the log file?

 

[TomC4306]

I did not charge the batteries before use

Then do that.
Especially series connecting pre-made batteries.

 

[JTB321]

Then do that.
Especially series connecting pre-made batteries.

Don’t have a charger, wasn’t expecting to have to need one once the system was running. I’ll feedback what info I get from the supplier.

 

[MrM1]

I doubt it's the inverter. It's mostly likely the BMS shutting down the battery. Do you have a couple Led acid batteries to test power up of the inverter?

 

[TomC4306]

Lol

Don’t have a charger

Perhaps it might be a good tool to have around a 12v charger...
You know, if you are going to play with 12 volt batteries...

Your problem is not the inverter.
Nor is it a battery problem per se. You need to charge these two batteries that you have connected in series to the same place.
I guarantee they did not arrive identically charged

 

[JTB321]

Lol

Perhaps it might be a good tool to have around a 12v charger...
You know, if you are going to play with 12 volt batteries...

Your problem is not the inverter.
Nor is it a battery problem per se. You need to charge these two batteries that you have connected in series to the same place.
I guarantee they did not arrive identically charged

I have auto battery charger, not sure if it is compatible? Still don’t understand why no inrush observed?

 

[JTB321]

Can you post a pic of your battery, switch and wiring?

 

[Vigo]

So i agree with you that it is ODD that you did not get a MAJOR spark when initially connecting the batteries, if you did not use any kind of precharge technique.

It's also odd that flipping the inverter switch from off to on results in ANY immediate change at the battery. The power the inverter uses to run itself is tiny, <3a from those batteries. It would take several seconds for the inverter to actually become operational and present any significant load to the battery circuit. Maybe 10 whole seconds! And that's only IF there were a load on the AC output!

So if you are getting some kind of problem immediately upon flipping that switch, AND you got no spark on initial battery hookup in spite of having no precharge circuit, i'm beginning to suspect you have a defective bms. Because you got no initial spark on battery hookup, the inverter would have to have ALL of its capacitors failed for that to be an inverter problem. If there was an actual open circuit between the inverter's battery terminals and the capacitors, you would also get no action/change from flipping the on/off switch.

But, because the batteries are in series, ALL the current which would be creating that spark/inrush at initial hookup, would have to flow through BOTH batteries. If one battery presents an extremely high resistance, it would prevent that current flow from reaching an obvious 'big spark' level.

It may or may not be BMS related. The fact that you ever saw a "<3v" number is odd because when the BMS disconnects, you would see basically NO voltage on the battery terminals. When it reconnects, it would not "slowly recover to 12.5v". It would jump almost instantly to the full resting ~13.2v. So i suspect you have a loose internal connection either between the cells and the BMS, or between the BMS and the case terminals. If you could communicate with the bms over bluetooth you could probably figure out which one it is from that, but either way if it's a sealed battery it's a warranty issue and not something you would DIY repair unless you had no warranty coverage at all.

 

[HRTKD]

It may or may not be BMS related. The fact that you ever saw a "<3v" number is odd because when the BMS disconnects, you would see basically NO voltage on the battery terminals.

I think there have been posts showing that when the BMS disconnects, there is still voltage (often at a reduced amount) but no current. But that varies from BMS to BMS.

 

[sunshine_eggo]

Don’t have a charger, wasn’t expecting to have to need one once the system was running. I’ll feedback what info I get from the supplier.

Get one. Your expectations were incorrect. You assumed the batteries you purchased were:

1) at the EXACT same state of charge.
2) needed EXACTLY the same amount of mAh to get to 100%.

I have a better chance of winning the Powerball.

 

[sunshine_eggo]

You will not

So i agree with you that it is ODD that you did not get a MAJOR spark when initially connecting the batteries, if you did not use any kind of precharge technique.

Is it odd? I've watched Will deliberately short battery terminals to test the BMS short circuit protection. No spark at all.

 

[Bluedog225]

I’m curious about the function of the unplugged male plug.