EG4 12V voltage drop under load

justinm001

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I have a pair of 12V EG4-LL batteries and when trying to run 1 AC unit it drops from 13V to close to 9V which restarts my entire system since i get a low voltage error. I have a Victron Quattro 5000 inverter and even tried a sungoldpower 4000w inverter but same issues. I don't have smart starts which I know the AC uses quite a bit of power to start but this shouldn't be an issue.

All wiring is 4/0 gauge to a Lynx1000amp distribution and just a couple feet between them all
 
I have a pair of 12V EG4-LL batteries and when trying to run 1 AC unit it drops from 13V to close to 9V which restarts my entire system since i get a low voltage error. I have a Victron Quattro 5000 inverter and even tried a sungoldpower 4000w inverter but same issues. I don't have smart starts which I know the AC uses quite a bit of power to start but this shouldn't be an issue.

All wiring is 4/0 gauge to a Lynx1000amp distribution and just a couple feet between them all
Too much surge for the batteries.
Maybe a 3rd will be enough.
Maybe a 4th.
Soft start is much cheaper.
 
Where in the circuit do you measure 9 volts, perhaps the BMS is entering protection mode.
 
It shouldn't be too much surge for a pair of 400ah lithium battery packs both with 4/0 cable to the Lynx and 4/0 combining them. These things are supposed to have 200a discharge EACH constant so 4800w or so combined.
 
Where in the circuit do you measure 9 volts, perhaps the BMS is entering protection mode.
On each inverter, the lynx and the battery terminals themselves. The victron shuts off and so does my internal firefly 12v system so had to rewire the thermostat outside that and use that sungoldpower inverter which keeps trying to pull loads then stops when voltage gets low so it was going from 13v to 9v every 5 seconds or so which confirms its the batteries causing issues.
 
9 volts at the battery suggests it's in protection mode, either over current or low cell volts. What is the info from the BMS reporting?
 
1 AC unit
stats on the AC unit? does it give its startup amps? or just running amps?

Too much surge for the batteries
^^ this is my guess. I had a chest freezer that was using ~250w running, but I was having issues starting it with a 1500w running 3000w surge inverter. The inverter would trip. Eventually replacing the stranded aluminum cables between battery and inverter with actual copper battery cable made it work.

restarts my entire system since i get a low voltage error
where is the low voltage error coming from? the batteries or inverter?
 
It's a dometic 11.5k rv roof ac unit. I have 6 of these on my coach. Basically it runs 500w for fan and 1700w when ac is also on. I'm able to get one running sometimes if I have no other load on. But even when on shore/generator power I have issues (victron assists power)

Problem is I have this firefly system that runs all my stuff and when 12v is low it turns off or restarts. Designed to protect things from low voltage like when batteries die. But the AC thermostat runs on 12v so whenever this happens everything shuts off for a second and I have to turn lights off and all. Then ac fan turns on for a few minutes before the ac compressor tries and it reboots again.

I get low voltage errors on my victron inverter and cerbogx. Also get high voltage on alternator since the batteries shut down it sends all the power back to the alternator. It's a pain bc the alternator shuts off and I need to pull over and turn off the coach. The alternator pumps up to 3000w but I'm not always driving when using the coach.

The battery bms doesn't trip and their software seems so buggy its not worth using.

I'm wondering what the max load is for these batteries and how much voltage drop is normal. I need 2 more batteries and planning 24v but now concerned if they can't handle the current if I should use something else and replace them all
 
I've seen reports of locked rotor amps for these units at well over 50 amps at 120v. Do the math and you are over 500 amps for 12 volt.
according to the manual below I should have 200amps per battery. What math am I missing 2000w at 12v is 166amps I'm not sure the start amperage but its gotta be under 4000w as i'm not getting inverter overload issues (5000va is 4000w) so its gotta be under 333amps.

 
batteries 400a at 12.8v is 5120w
reports of locked rotor 50a at 120v is 6000w
I thought locked rotors is a problem and just a one time issue at that. I have 6 of these ACs (only 3 or so wired up/working) but same issue with either one of the ACs.
 
I don't think the issue is the ac units pulling to many watts I think it's the batteries not being able to handle large loads without lowering the voltage. I belive I have this issue with anything pulling over 2000w
 
IMHO: Trying to run large loads on a 12V inverter is not a good idea. The DC current gets extremely high which means voltage drops get very high. At 300A, every connection is going to see a voltage drop. Add to that the operating voltage range on a 12 V system is rather narrow compared to a 48V system.

With the high currents creating larger voltage drops and the lower tolerance of voltage drops of 12V systems, you get a double whammy.
 
IMHO: Trying to run large loads on a 12V inverter is not a good idea. The DC current gets extremely high which means voltage drops get very high. At 300A, every connection is going to see a voltage drop. Add to that the operating voltage range on a 12 V system is rather narrow compared to a 48V system.

With the high currents creating larger voltage drops and the lower tolerance of voltage drops of 12V systems, you get a double whammy.
But the batteries should be able to handle 200amps constantly each right? And at 200a the voltage shouldn't drop from 13 to 9 regardless.
 
But the batteries should be able to handle 200amps constantly each right? And at 200a the voltage shouldn't drop from 13 to 9 regardless.
Yes... the batteries should be able to deliver the amps without a huge voltage drop... and they probably do.

Try this.
Slowly ramp up the load till you are running 150A from the batteries. If the system won't get to 150A, stop at just below what the system will handle.

With the large load, Measure the voltage at the battery and at the Inverter.
If you have an infrared camera, look for hot spots. If you don't have an infrared camera, try touching all the connections and see if you find a connection that is warmer than others.
 
Yes... the batteries should be able to deliver the amps without a huge voltage drop... and they probably do.

Try this.
Slowly ramp up the load till you are running 150A from the batteries. If the system won't get to 150A, stop at just below what the system will handle.

With the large load, Measure the voltage at the battery and at the Inverter.
If you have an infrared camera, look for hot spots. If you don't have an infrared camera, try touching all the connections and see if you find a connection that is warmer than others.
Thank you will do
 
But the batteries should be able to handle 200amps constantly each right? And at 200a the voltage shouldn't drop from 13 to 9 regardless.
When I was looking at the eg4 12v server rack batteries 4-6months ago I think the max continuous was only 100a. There were some discussions about how ridiculous this was for a 400a battery. I believe SS claimed they fixed it and they now do 200a continuous but some people were still having issues similar to what you are describing. They don’t handle large surge loads with out tripping. Not sure if it was actually a battery issue or user setup issue. I know the blame SS topic gets a bit touchy around here so I’ll just leave it at that.

 
I thought locked rotors is a problem and just a one time issue at that
LRA or Locked Rotor Amperage will happen every time you start the unit. Its equivalent to surge wattage.

For example my well pump has a FLA (Full Load Amperage) of 5.0a
a SFA (Service Factor Amperage) of 6.2
and a LRA (Locked Rotor Amperage) of 18.0a.
So essentially the surge wattage needed to run it is 3x the running wattage.

Motors and Pumps are notorious for needing a much higher surge wattage rating on an inverter to start them.

The same is true for anything with a compressor - refrigerator, freezer, or AC.


I've seen reports of locked rotor amps for these units at well over 50 amps at 120v. Do the math and you are over 500 amps for 12 volt.

50a * 120v = 6000w
6000w / 12.8v = 468a

You say that the batteries should be able to handle 400a, but you are pulling more than that.

Q-Dog says "well over 50a" and even with the 50a equation you are over 400a at the batteries.


Motor-driven appliances (such as refrigerators and air conditioners) for initial start-up require larger amounts of current than when they are running. This is because induction motors initially act like a short-circuited transformer. The maximum start up current is referred to as "Locked Rotor Amps" (LRA) because at the first moment when the rotor is at standstill it appears as if it's locked. This current will drop significantly when motor accelerates to about 75% full speed. The LRA is typically 3 to 8 times continuous operating current (called full load amps, or FLA).

The LRA is typically 3 to 8 times continuous operating current (called full load amps, or FLA).



So even if we assume the LRA is only 3x what you say the wattage is (1700w) ((not sure if this includes the 500w fan or not))
1700w * 3 = 5100w
5100w / 12.8v =398a


You are simply trying to pull too much from the batteries.
We have done the math in multiple ways.

Its very unlikely its an issue with the batteries.


The first reply you got says it all
Too much surge for the batteries.
Maybe a 3rd will be enough.
Maybe a 4th.
Soft start is much cheaper.

No way of knowing how many batteries you will need to run the AC without knowing its actual LRA
 
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