Getting more than 1500w out of an EG4 3000w and a single Lifepower4 48v

[ZeroZim]

I have an EG4 3kw inverter and a single lifepower4 battery. It runs as a backup for the networking equipment in the house with a steady 500w load. We had the opportunity to borrow a travel trailer and I wanted to be able to have the AC after "generator hours" are over. So I dismantled the setup in the house and attached it to a hand truck to put into the trailer.

However, it won't run the AC. The battery goes into fault and the inverter reboots. I tried the firmware update that EG4 put out (the one with the lousy attitude in the video) and successfully updated it. Now it doesn't go into fault but it does restart. No error on the inverter that I could see. The battery specs clearly indicate that it's capable of 100a output, with 30 recommended. I just don't see more than 30a output.

My little Honda will start it, if Eco mode is off, so the surge isn't much more than 2000w. The generator doesn't even go into overload to do it.

Components:
12,500 BTU AC from 2019
Travel trailer with 30a input wiring
Honda EU2000i generator with 2000w surge, 1600w rated
LifePower4 5kwh battery 48v
EG4 3kw inverter

I'm sure adding another battery would be all the difference, but this is a temporary setup just needed through the end of the week. It's just frustrating to not get anywhere near the rated power out of the unit.

Any ideas for how to get this working?

 

[Koldsimer]

You could always install a soft start for the ac - that would likely get you by and it would be beneficial in the long run for your ac.

Seems the 'recommended' 30 amp limit is actually a hard limit. Which makes their claim of 100a discharge BS.

I'm surprised to hear that the firmware update didn't work for you. Has Signature responded to the update not working and offered an explanation?

I didn't like their video either. Typical amateurish Signature Solar quality. No details on what the 'fix' is. Reminded me of a hostage video. I can just imagine James off camera telling poor Richard "Remind them it's their fault! Tell them we are the best!"

 

[Browse]

Has anyone done any real world testing of these rack mount batteries to see if they are even capable of supplying 100A discharge? Any application with a large inrush would be impacted by this presumed limitation, in which case it would be better for most folks to simply get a basic battery with no internal BMS at all.

 

[ZeroZim]

>install a soft start for the ac

If it was my trailer, or if the soft starts weren't $300, I'd definitely be doing this.

 

[Koldsimer]

Has anyone done any real world testing of these rack mount batteries to see if they are even capable of supplying 100A discharge? Any application with a large inrush would be impacted by this presumed limitation, in which case it would be better for most folks to simply get a basic battery with no internal BMS at all.

I tested my SOK 48v by itself on my system. Not only did one battery start my large LF inverter with no issue, it powered about a 4.5kw load for several minutes without flinching. Part of the load was a table saw and i'm sure the load momentarily exceeded 5kw but the SOK battery handled it no problem.

When Current Connected says it will do 100a, they mean it!

 

[Solar Guy Richard]

Just to verify - the battery and inverter work fine together in your home but not with the load from the trailer? Have you tried starting the system up and then adding the load by engaging breakers?

 

[timselectric]

Plain and simple.
Not enough battery for the startup surge of the A/C.

 

[Koldsimer]

What do you estimate the startup surge to be? Seems like a 48v 100a rated battery should be able to handle that. After all, the little honda 2000w max generator didn't trip anything when powering the same ac.

 

[timselectric]

Whatever the manufacturer recommends for the inverter. I'm guessing 150a, for a 3k.
But, can't say for sure.

 

[ZeroZim]

Just to verify - the battery and inverter work fine together in your home but not with the load from the trailer? Have you tried starting the system up and then adding the load by engaging breakers?

The inverter/battery work in the trailer too, just not for the AC load. It does the lights, microwave, fan, chargers plugged into outlets, 12v charger, etc. It will start a vacuum if nothing else is hooked up, but will not start the vacuum if there's any other load on the system already. Before applying the firmware the battery would get a red light and go into fault. Now, post-fix, most of the SOC lights go out but then it comes back and the inverter isn't powered off.

It's the starting surge that it's not coping with. the AC uses about 1400 watts to run, and the rule of thumb seems to be double that for the starting surge. The weird part is the little Honda can get it started without tripping (it is clearly not happy about it). It revs all the way to the top but it pulls through and settles back down.

 

[timselectric]

Surge can be up to 5x.
Depending on the startup efficiency.

 

[ZeroZim]

Just to verify - the battery and inverter work fine together in your home but not with the load from the trailer? Have you tried starting the system up and then adding the load by engaging breakers?

I just recorded a video of it, and I think that the battery firmware did shift the problem to the inverter.

There is a noise in the inverter when the load hits, and the inverter reboots. I didn't see a change on the lights on the battery. This isn't the behavior I thought I observed yesterday, but I'm not going to argue with video. I do have a second inverter, so maybe halfassing them in parallel would work.

Apologies for the flaws with making a video, clearly I am not a youtuber.

 

[chess-equality]

Does it run the AC initially then faults, or it couldn't start the AC at all?

How about a soft start on the AC? Or in my case, I put the AC on "fan" mode first for a few seconds before turning the compressor on to "cool" mode.

My AC is rated 1200+ watts connected to my 2p 12v bank + Chinese inverter (3kw) and I've got no problems with it (max draw though is only 700-800w, and since it is an inverter-type AC, it powers down when it gets cold enough).

 

[timselectric]

Startup surge on an inverter type A/C is minimal.

 

[Vigo]

Do you have a meter with min-max? Might put it across your battery leads at the battery end, and then at the inverter end, and see if your cabling is causing a substantial drop during the startup surge. Scabbing more paralleled leads onto the connections would be a pretty quick and easy bandaid if you didn't already have the stuff to do a permanent upgrade of the cabling. That's IF you find a substantial drop during those conditions.

I agree with turning on the breakers one at a time. Another thing you might want to do if possible is start the AC in fan-only mode and let the fan get up to speed before trying to start the compressor. If you are already CLOSE to getting it started, not trying to start both the fan and compressor at the same time may make the difference for you.

I don't know anything specific about the inverter, but if it has an AC-input and a transfer switch you might just start the generator before starting the AC, and then shutting it down after the compressor starts. Yeah that's half-ass but if you run the AC at max settings that compressor may never turn off and have to restart in which case 1 minute of generator operation would facilitate hours of AC function.

I agree that it's fundamentally down to the battery acting wimpy. I have started a 22k btu ac off of 4 group 29 hybrid marine lead acid boat batteries through 10 feet of crappy cabling hundreds of times, nary a complaint. A battery that size should be able to cover up a whole pile of wiring sins before it makes you not able to start a 14k ac.

In my RV with a 12v system and a ~14k btu rooftop unit, I have measured a little over 300a into the inverter during the startup surge. Now at 48v that would be ~1/4 the amps, well under 100 I would hope and a battery that size should not only be able to do that momentarily, it should be able to do it for an hour straight.

 

[ZeroZim]

Ok, so 2 inverters in parallel got it running. Battery firmware update clearly did something positive with current availability on the battery.

Load per each was 600w running. Not sure what starting was. It really seems like 3000w (6000w surge? for 5 seconds?) should have been enough. I was able to shut off the secondary inverter and keep the AC running, as pictured below. 1.27 kw on the one inverter.

Are there any settings to make these inverters less sensitive to the surge?


Wiring needs to be redone properly and I need to rethink the mount/hand truck.




>chess-equality, timselectric
Starting the fan first, then the AC didn't work, I tried that before redoing it.
Also, it's not our camper and is just a temporary setup, so a soft-start is out of budget for this initiative.
It is definitely not an inverter AC. We have minisplits in the house and they have a very minimal start load.

 

[ZeroZim]

Do you have a meter with min-max? Might put it across your battery leads at the battery end, and then at the inverter end, and see if your cabling is causing a substantial drop during the startup surge. Scabbing more paralleled leads onto the connections would be a pretty quick and easy bandaid if you didn't already have the stuff to do a permanent upgrade of the cabling. That's IF you find a substantial drop during those conditions.

I agree with turning on the breakers one at a time. Another thing you might want to do if possible is start the AC in fan-only mode and let the fan get up to speed before trying to start the compressor. If you are already CLOSE to getting it started, not trying to start both the fan and compressor at the same time may make the difference for you.

I don't know anything specific about the inverter, but if it has an AC-input and a transfer switch you might just start the generator before starting the AC, and then shutting it down after the compressor starts. Yeah that's half-ass but if you run the AC at max settings that compressor may never turn off and have to restart in which case 1 minute of generator operation would facilitate hours of AC function.

I agree that it's fundamentally down to the battery acting wimpy. I have started a 22k btu ac off of 4 group 29 hybrid marine lead acid boat batteries through 10 feet of crappy cabling hundreds of times, nary a complaint. A battery that size should be able to cover up a whole pile of wiring sins before it makes you not able to start a 14k ac.

In my RV with a 12v system and a ~14k btu rooftop unit, I have measured a little over 300a into the inverter during the startup surge. Now at 48v that would be ~1/4 the amps, well under 100 I would hope and a battery that size should not only be able to do that momentarily, it should be able to do it for about 5 hours straight.

Battery cables are 4awg. 2awg to connect the bus-bar in parallel (was series in the house). The AC out wiring was on the wimpy side at 12awg going into a normal outlet, I wanted this to work before I started cutting up the RV power cable I bought.

Should I have cut off the tinned ends?

 

[Vigo]

Load per each was 600w running. Not sure what starting was. It really seems like 3000w (6000w surge? for 5 seconds?) should have been enough. I was able to shut off the secondary inverter and keep the AC running, as pictured below. 1.27 kw on the one inverter.

Yes, it SHOULD be enough. I suspect the problem is actually in the battery, not the inverter(s). But you would have to verify that to be sure. Again, if you have a meter with min max and clip to the battery leads and turn on min-max, the min reading would tell you if the battery bms actually shut off or not. By extension, if it did not that means the inverter itself was the culprit. I think that putting the 2nd inverter in parallel doesn't actually prove that it's not a battery problem, because the inverter probably has capacitance built into it such that if you installed a crap load of paralleled inverters, they would 'mask' the full extent of the inrush current requirement from the battery because of their internal capacitance taking some of the initial hit. Anyone and everyone feel free to correct me if that's off base.

Are there any settings to make these inverters less sensitive to the surge?

IF the battery itself is not causing the problem, the only thing you could do in the inverter is make sure the low voltage cutoff point is higher than what the battery's internal low-voltage cutoff is. For example, if the battery bms low voltage disconnect is at 10.0 but for some reason the inverter it set to 11.5, it's possible changing that would make a difference. BUT, as far as i know lifepo4 voltage under load does not sag to anywhere near the extent of a lead acid (and possibly other chemistries I know nothing about), so you should really never be hitting low voltage disconnect on lithium in response to a short heavy load unless the state of charge of the battery was low and the 'resting' voltage was very near to the cutoff point already.

As far as what size the cables are, nothing about their performance is guaranteed without actual voltage drop measurements. You install the 'correct' size of wire as best practice, but it's possible a crimp is not very good, especially if you're DIY'ing them. Or a bolted terminal connection is simply loose, or bolted down on top of a speck of junk, etc. Lots of possible imperfections, and checking for and sometimes even correcting them is often easy and free. Trust but verify, i guess.

 

[timselectric]

By adding the second inverter, you also doubled the size of battery cables. Which lowered the voltage drop. And allowed it to hold long enough to start the A/C. And also doubled the surge capacity from the battery and inverters. Both helped, but either might have been enough.

 

[Lilikoi_Heavy_Industries]

Your video shows the lugs sliding around on your battery terminals, they aren't tightened. 2GA is the minimum wire size I'd use, and then I'd still be following up with voltage loss measurements...

While you're right, it's very common to use 6GA and 4GA for busbar jumpers on these batteries, your 4GA wires seem long by comparison.