[dog_house]

I'm with Gary on this one, it seems like those batteries are a bit weak. For comparison, we have a set of the absolute cheapest LiFePO4's you can buy right now and they stay above 12.6v at .5c (equivalent of 200a with your setup). With a two foot round trip your 2awg wires should be dropping less than .2v or so and a bad crimp would have shown up as a warm lug and wire which you don't seem to have. You should be above 12v at the inverter terminals all the way down to below 20% on your batteries.

If it's not too hard to do I would check a few things to rule out the batteries or maybe find the problem. I would charge the batteries one at a time at 14.6v until the current drops below an amp and leave them there for a few hours to help balance the cells. If you never did this "out of the box" there are probably low cells in each battery. The BMS balances the cells in your batteries by "holding back" the higher cells with a resistor and bleeding off power while the others catch up. It only does this when the battery is above 14 volts. You can do this by setting the float on your charger to 14.6v. If the amperage going in the battery drops suddenly and the voltage spikes above 14.6 it means they were in fact out of balance and the BMS turned off. Once the battery has been at 14.6 for several hours so that you know its 100% charged and balanced run the inverter with an 800-900w load to cause a 100a draw in the battery and see what the terminal voltage is. Running at the BMS rating (100a) and .5c the voltage at the battery terminals should be above 12.5v until the battery is almost completely discharged. Repeat with the other battery and make sure they are both healthy, sometime when you have LiFePO4's in parallel one can trip it's BMS and not be contributing and it's hard to tell. With your setup if one battery trips, the other is not going to be able to maintain the load by itself.

Multiply these values by 4 for your 12v battery. You can see that the voltage at the cells should be 12.8v for almost all of the discharge curve. The BMS and skinny little wires they use where you can't see will drop that to around 12.5v at the terminals.

 

[Dirtrider]

It didn't go off today when using both sources but in the past, yes. I didn't measure voltage when it did but watching the voltage drop quickly today, I would guess that is what's happening.
I'm going to contact the battery company and see what they say.
Looking at the Renogy battery, it states 200A Max continuous which is double of these batteries.

 

[larry barello]

I have a similar setup but with 2x100ah Renogy batteries and it handles an 1800wt load without issues and my batteries drop to 12.8v very quickly under load (150+ amps). I use #2 wire and have about .8v drop under load.

As @SteveSS points out the inverter cut off it 10v (default). Mebby you should check what it is actually set to?

I recently replaced my isotherm with a 1.3 g point of use heater with 1440w element and on my first camping trip I must say I am really happy with it.

 

[dog_house]

It didn't go off today when using both sources but in the past, yes. I didn't measure voltage when it did but watching the voltage drop quickly today, I would guess that is what's happening.
I'm going to contact the battery company and see what they say.
Looking at the Renogy battery, it states 200A Max continuous which is double of these batteries.

You should have 200 amps available since the two batteries are in parallel 👍

 

[SteveSS]

Looking at the Renogy battery, it states 200A Max continuous which is double of these batteries.

I just looked at their 200Ah battery. It's practically twice the size of SOK's. Renogy's may be configured more like two 100Ah batteries in one box, which would explain the 200A max continuous draw.

 

[larry barello]

Lithium cells can be designed for high capacity or high current draw. Guess which one is larger.

Still, the two high capacity batteries in parallel should be able to handle 150a without problems. That's 2kw.

 

[Uvan]

voltage drop in high amperage draw is normal but it shouldn't drop below the warning threshold. You should check with the voltage at the inverter terminals and see at what voltage the warning starts. Maybe like what other said, the warning voltage might be set too high??

 

[Dirtrider]

I don't think there is any adjustments on the inverter to adjust. I'm working with the battery manufacture now getting them the reading they requested. They seem very eager to assist which is a good sign. They stated that this setup should more than handle the load. We'll see what happens in the coming week

 

[dog_house]

I just looked at their 200Ah battery. It's practically twice the size of SOK's. Renogy's may be configured more like two 100Ah batteries in one box, which would explain the 200A max continuous draw.

LiTime/Ampretime offer another version of the 200amp hour battery called "Plus" with a higher 200a discharge rating.

 

[psantangeli]

Been said before, but I'd probably start with cables. I use 2 BigBattery's for a total of 340ah. The cables they came with were way too small - particularly the parallel 'Y' cable.

I swapped them out for 0 gauge and 00 gauge cables (the 0 going 'into' my home made 'Y' adapter, the 00's coming out of the 'Y' adapter and to the panel), and it has made a big, big difference. With big loads and small cables the voltage will drop to the point that your devices can cut out.

 

[Dirtrider]

I think I solved the problem. In testing the power when running, I used two meters to measure the current at the batteries and the other at the inverter. Working from the batteries outward I had one at the batteries and the other at a 250A re-settable circuit breaker "fuse". The voltage was fine even through it kicked off. I moved the meter to the output side of that breaker and the voltage when "normal" was .30V lower running through it which seemed OK. Just for a split second, the output side of the breaker dropped to 9.11 setting off the low voltage beeper on the inverter. So, I let it run again and it did it again. I then disconnected the circuit breaker from the system and just bolted the two positive wires together for testing. It worked perfectly fine, ran until the water was hot and the heater stopped (not need to heat more). The lowest the voltage I got was 12.4V at the inverter so I think I found the problem. At no time did that breaker trip which is troubling. Ordering a ANL fuse (like I should have used) and will test it out again. Crossing my fingers but it looks to be promising.

 

[RV8R]

I think I solved the problem. In testing the power when running, I used two meters to measure the current at the batteries and the other at the inverter. Working from the batteries outward I had one at the batteries and the other at a 250A re-settable circuit breaker "fuse". The voltage was fine even through it kicked off. I moved the meter to the output side of that breaker and the voltage when "normal" was .30V lower running through it which seemed OK. Just for a split second, the output side of the breaker dropped to 9.11 setting off the low voltage beeper on the inverter. So, I let it run again and it did it again. I then disconnected the circuit breaker from the system and just bolted the two positive wires together for testing. It worked perfectly fine, ran until the water was hot and the heater stopped (not need to heat more). The lowest the voltage I got was 12.4V at the inverter so I think I found the problem. At no time did that breaker trip which is troubling. Ordering a ANL fuse (like I should have used) and will test it out again. Crossing my fingers but it looks to be promising.

Yup ,,, Good Find 👍

This is partly why I prefer fuses & a switch over a “breaker switch” ,,, can get resistance.

 

[Uvan]

What brand breaker did you used? From what I read here, a lot people have issue with the cheap Chinese made breaker. I'm currently using ANL fuses but it will be nice not having to unbolt a burnt out fuse every time with a resettable breaker.

 

[83Grumman]

Just for a split second, the output side of the breaker dropped to 9.11 setting off the low voltage beeper on the inverter.

Open and close the breaker 25 times, then test it again.

 

[Dirtrider]

What brand breaker did you used? From what I read here, a lot people have issue with the cheap Chinese made breaker. I'm currently using ANL fuses but it will be nice not having to unbolt a burnt out fuse everything with just a resettable breaker.

One like this

Amazon.com

 

[Dirtrider]

Open and close the breaker 25 times, then test it again.

Not sure if this is a fix or you're pulling my leg here
I'm just going to change it out and hopefully fix the issue

 

[RV8R]

Not sure if this is a fix or you're pulling my leg here
I'm just going to change it out and hopefully fix the issue

He isn’t joking. The contacts can get a bit of corrosion on them & cause resistance. Breakers are “exercised” in airplanes to overcome this issue & voltage drop.

If you are going to use breakers ,,, use good quality ones.

 

[Wowbagger]

For high currents like this, I am squarely in the fuse camp. Breakers are great if you plan on them tripping all the time - for example, on my van's 120VAC side I use the breaker on the auxiliary heat to switch it off when I am on battery and using the diesel heater. But if you don't plan on the circuit tripping all the time, fuses work and are more reliable.

 

[GaryBIS]

If you have any more of those cheap Amazon China breakers, I'd get rid of them. I've had two of mine go out and others here on the forum have reported more failures.
Use fuses or high quality breakers like BlueSea.

Gary

 

[HarryN]

For high currents like this, I am squarely in the fuse camp. Breakers are great if you plan on them tripping all the time - for example, on my van's 120VAC side I use the breaker on the auxiliary heat to switch it off when I am on battery and using the diesel heater. But if you don't plan on the circuit tripping all the time, fuses work and are more reliable.

This is one of the reasons that I use a breaker for each parallel battery or battery string.