Trouble with large loads on Giandel Inverter

[clyndes]

I'm still in the shakedown portion of my new system. I'm having a problem when I put large loads on my Inverter (Giandel 2200Ksc 12v). Smallish loads, 50 amps or less, everything works as expected. Larger loads (my hot water heater 1500W, vacuum cleaner 700W) sees the DC voltage from my 2 271Amp Hour Lithium batteries (CATL Cells, OverKill Solar BMS) settle down at around 13V. My smart shunt shows 100 amps being drawn. Tracking voltage from the batteries to the inverter I see .3V DC loss (2 circuit breakers, two 6' 00 cables). This gives 12.7V at the inverter. After a minute or so the inverter goes into low voltage (says <12.1) and shuts down. Checking the voltage on the inverter terminals I see very low voltage 4V or so. Shut everything down. Batteries go back to charging, all voltages look OK. Turn on inverter, looks fine. Add 1500 watt load and the whole thing repeats.

Do I have a bad inverter?

Thanks in advance!
Craig Lyndes

 

[sunshine_eggo]

1500W/12V/.85 = 147A

What is the cable gauge and one-way cable length between battery and inverter?

Have you TRIPLE CHECKED that every single crimp/fitting is of high quality and confirmed that all threaded connections are properly torqued? The #1 cause of what you describe is a bad connection somewhere. A single improperly torqued bus bar terminal can do this as well.

 

[12VoltInstalls]

single improperly torqued bus bar terminal can do this as well.

The load makes heat and the stud elongates a few thou (or less) but the nuts not only have less thread length but ‘in theory’ can only contribute half the length of their depth of thread to compensate for thermal expansion. Which is where proper torque comes into play as the torqued stretch of the stud/fastener exerts more net force than that which is reduced by thermal expansion.

When I torque nuts on flooded batteries they seldom loosen; when I tighten them ‘enough’ by hand even with a lot of years of experience I’ve been surprised how often I later find the nuts not tight- especially if installed in freezing temps and it’s 70*F later…

 

[740GLE]

Your issue is a 12v system for the intended loads, 24v is more suitable for that size.

What’s the current rating of the BMS 150A? Do you have a BMS per battery? If your reading 4v at the inverter that would lead me to look at a BMS cutting out and then the other going into over current protection.

(1500+700)/12v/.85 = 215a

This would exceed 100a BMS.

Can you measure the current split of the batteries under load? Verify it’s 50/50.

 

[mikefitz]

The BMS is shutting down due to over current or over temperature in the fets. The Overkill BMS is rated for 120 amps.

Mike

 

[MichaelK]

This is a reality check. This is what happens when you attempt larageloads with a 12V system. You really should be looking at a 24 or 48V system to run the loads that you are talking about.

 

[clyndes]

Thanks folks for your replies!

One way length of cable from batteries to inverter; 4' 2/0 then 3' 1/0.

l triple checked connections, found 1 misplaced washer on smart shunt, fixed that. Terminals applied with hammer type terminal tool by myself, amateur. Ordering hydraulic tool when I'm at a place where I can get deliveries next. .3 V drop from BMS to Inverter under 100 AMP (measured at smart shunt) load.

120 Amp Overkill BMS, one BMS per 12V Battery, 2 batteries in parallel. Amperage draw within 1 amp under 80 amp combined load (40 amp and 39 amp). Possibly because I can't look at both BMSs simultaneously.

I've been expecting heat where the current is being blocked. I haven't found anything getting hot.

Dreaming about rack mount 48V batteries and inverters, but guess I'll make do with what I have for now.

Thanks Again.