Proposed battery bank for large inductive load's surge

[PowerAssist]

I'm looking at creating a battery bank capable of powering a large inductive load, specifically a 3hp well pump for which I've measured an inrush current of 55A at 240v. These low frequency inverter chargers are described as being well suited for such a load and can surge up to 18,000W for 20 seconds.

Can I pair one of these inverters with 4 (or more) EG4 batteries to handle such a load? The batteries are rated for 100A discharge which would be 19,200W. Would the batteries be able to handle such a surge/inrush? I've read other threads (here) which suggests that a surge of >30A causes issues, but I haven't been able to find any other info to back that up.

I suppose if I filled out a full rack of 6 batteries, that would drop it to 45A per battery which is still above that 30A figure. An alternative is the SOK battery whose manual states a "Peak Discharge Current: 125A (3 Seconds, automatic shutdown)". Can I assume this 125A figure to be valid for an inrush / surge load?

My plan would be to purchase as follows, though I don't know if there's a reason to prefer one hardware over the other:

• 6000W 48V Inverter Charger - one of:
  • AIMS - $2,244 or
  • Sigineer - $1,349 or
  • SunGoldPower - $1,299
• 48V 100AH battery:
  • 30.72kWh EG4-LifePower4 Kit - $8,694
  • 25kWh SOK Kit - $8,450

The main goal of this project would be to power our well during a power outage, but I see no reason that this wouldn't be able to run our house entirely (minus our central 3.5ton AC .. maybe with a soft starter). Ideally I could charge this from a 240v generator (I assume 120v is not possible) without having to turn off the inverter and it'll figure out how to manage itself.

But my main concerns is still about the batteries and how they respond to a large inductive load.

I appreciate the time and help, thanks!

 

[PreppenWolf]

LiFePO4 batteries have very high discharge rates. The BMS would be the only limiting factor. Two shared server rack batteries of either type you listed should have no problem supplying that load.

 

[BentleyJ]

I'm looking at creating a battery bank capable of powering a large inductive load, specifically a 3hp well pump for which I've measured an inrush current of 55A at 240v.

I would suggest looking into a soft starter. Many of us on forum use them for the AC condenser. If the well pump uses a normal induction motor a soft starter like this one should work.

SS1B16-32SN (230V, 60/50Hz, 16-32 FLA)

Soft Start Single-Phase | Eltwin

www.hypereng.com

 

[PowerAssist]

@PreppenWolf That's good to hear, I'm curious why others had mentioned something about surge issues, but I assume I would have heard more about it if it was really an issue.

@BentleyJ Soft starter would be nice though I'd like to get some confirmation that it wouldn't cause issues. I forget where I read it, but someone had mentioned that if the pump doesn't get up to full speed in <500ms that there isn't the same water lubrication that would exist normally? I might be totally making that up.

In any case, the pump we have is a Goulds 35GS30 and there's a control box with a 3 wire configuration (though still single phase 240v). I don't know what that means for a soft starter, but I'll reach out to https://www.xylem.com/en-us/brands/goulds-water-technology/contact-us/ and see if they can provide some information.

If I could get that tamed down from 55A to 25A that would be fantastic and make this whole thing much, much easier.

 

[PreppenWolf]

Soft starters are def the way to go on any high draw items you can afford them on. Gives you more headroom for sustained load.

 

[PowerAssist]

@PreppenWolf Okay so I looked up the manuals for the control box which on page 36 of this PDF says

Reduced-voltage starters have adjustable settings for acceleration ramp time, typically preset at 30 seconds. They must be adjusted so the motor is at full voltage within THREE SECONDS MAXIMUM to prevent excessive radial and thrust bearing wear.
If Subtrol-Plus or SubMonitor is used the acceleration time must be set to TWO SECONDS MAXIMUM due to the 3 second reaction time of the Subtrol-Plus or SubMonitor.
Solid-state starters AKA soft starts may not be compatible with Subtrol-Plus/SubMonitor. However, in some cases a bypass contactor has been used. Consult the factory for details.
During shutdown, Franklin Electric’s recommendation is for the power to be removed, allowing the pump/motor to coast down. Stopping the motor by ramping down the voltage is possible, but should be limited to three (3) seconds maximum.

However, that was under a section for 3 phase motors, specifically whereas mine is a single phase (three wire) so it may not apply. I'm reaching out to see what more info I can get though, but it does seem like there is consideration for soft starters so I'm not completely making this up. Though it may not be an issue for single phase.

The control box does have capacitors in it, which I assume would help with the startup so I'm curious how much lower the soft start can go. Again though, I'll reply back when I hear from Hyper support.

 

[Brett V]

For a large inductive load like the well pump you mentioned, battery capacity isn't your main concern...The startup surge is. You absolutely want a low frequency inverter with a transformer. I'd look closely at the Growatt 12k unit if you wish to stay in your specified price range.

 

[kjgee]

I have a 3HP well pump (865' deep) on an XW Pro 6848 and (4) EG4 Lifepower4 48V batteries. I have intermittent issues with inverter shutdown due to low voltage when the well pump kicks on. Low voltage cutout for the inverter is set to 44V as Signature Solar suggests. I've not yet experimented with a lower voltage cutout setting. I plan on eventually buying two more batteries to fill the 6-slot rack. 4 does not appear to be enough to reliably handle the surge. A soft start could help as well.

 

[Browse]

Growatt 12k. I've read about a bunch of issues with the 6k not performing as expected with large inrush devices. I have a 4-ton HVAC with an EasyStart 368 soft starter. The system draws about 55A on startup even with the soft starter. I also have 4 of the Lifepower4 batteries. Haven't tried the HVAC yet due to cold weather. I'll be able to try it in a few months.

This guy has both the 6k and the 12k:

 

[Browse]

If you're worried about voltage sag on the batteries, you can also consider one of these new "Chargeverters" which can take your generator power and convert it directly to DC and connect it to your rack. I may consider one of these as part of my backup plan since I only have 4 of the rack mount batteries.

 

[PowerAssist]

@kjgee I looked up the specs on the XW Pro 6848 and it seems to be 6kw continuous and 12kw surge. I don't know if you measured your inrush, but at 865' deep (wow) your pumps is literally 10x as far down as mine is. If there's a 240*55A=13,200W inrush on my pump it's got to be even more for yours. I would imagine that you're pushing the specs of your inverter but I'm curious if it's possible that a larger inverter could furnish that load given the same 4 batteries. Not 100% but I think 4 could potentially be fine with a larger inverter?

4 does not appear to be enough to reliably handle the surge

@Browse @Brett V I'm pretty sold on that Growatt 12k unit. It's not much more money and has significantly more headroom and should be a much safer bet overall.

I'm attaching a picture of our actual power usage - the largest spikes are the electric oven. A 12kw unit would be able to power our normal usage no problem whereas a 6kw unit would really be pushing the limits.

I'll have to look into the chargerverter - never seen one of those before, but the plan would be to charge the battery bank with a generator. I only have a 120V generator currently, so this would be a nice way to re-use that rather than buy a 240V generator. Ideally it would be possible to charge the batteries while they are being discharged through the inverter (which only has a 240V AC input).

I'd like enough batteries to make it 12 or more hours with enough surge power to run the well. So that's about 15kwh of storage and 15kw of surge power. That should be do-able with the Growatt 12kw unit and 4x 100Ah 48V batteries.

I wish we could use our solar, but we have a backfeed rather than a line tap so adding a IQ System Controller to our IQ7X based system would be cost prohibitive. It's a meter breaker "all in one" panel which may not be possible to make a sub-panel due to the bonded neutral as it was never meant to be a subpanel.

In a perfect world I'd buy 3x Encharge 10, IQ System Controller 2, and a new panel but that's $50,000.

Thanks for the help, I really appreciate the insight.

 

[Brett V]

Growatt 12k. I've read about a bunch of issues with the 6k not performing as expected with large inrush devices. I have a 4-ton HVAC with an EasyStart 368 soft starter. The system draws about 55A on startup even with the soft starter. I also have 4 of the Lifepower4 batteries. Haven't tried the HVAC yet due to cold weather. I'll be able to try it in a few months.

This guy has both the 6k and the 12k:

I have a 6k Growatt in service right now and it handles a 1hp well pump just fine. I've tripped a fault a few times on simple overload (exceeding 3000 watts on on leg) and have exceeded the 100 amp limit on my BMS a few times, but never had a problem with the well pump or any of the other inductive loads I have such as a few freezers. The energy stored in the transformer seems to get the job done.

 

[Browse]

I have a 6k Growatt in service right now and it handles a 1hp well pump just fine. I've tripped a fault a few times on simple overload (exceeding 3000 watts on on leg) and have exceeded the 100 amp limit on my BMS a few times, but never had a problem with the well pump or any of the other inductive loads I have such as a few freezers. The energy stored in the transformer seems to get the job done.

Yep, the 6k can handle surges but the OP has a 3HP pump. The 12k should provide a larger margin of error especially if other devices are running.

 

[Brett V]

Yep, the 6k can handle surges but the OP has a 3HP pump. The 12k should provide a larger margin of error especially if other devices are running.

That's why I suggested the 12k unit for him. I actually have a 12k still in the shipping crate sitting in the garage. Haven't installed it yet and not sure if I will since the wife has finally learned a few simple things like turning off the AC for a few minutes while she uses the hair dryer.

 

[Browse]

I found that the 12k is a beast to mount if you're going to do it yourself. There are a few videos of people using pulleys, but I was able to mount temporary legs on mine and tilt it up with the help of some rope and counterweights so I could walk it over to the wall. Once screwed in, I removed the legs. I suppose if you're really strong you can muscle this thing around, but that wouldn't be me....even 30 years ago in my prime.

 

[PowerAssist]

3hp pump, correct.

Yeah I'd have to figure out where and how to mount this all. I guess that was the once nice part about the smaller 6kw bricks .. much easier to mount. But I'd also need to account for non-flammable backing material, wires, breakers/fuses and all the rest, too. I wish they made a rack mount inverter that you could just slot in above the batteries.

 

[Brett V]

I found that the 12k is a beast to mount if you're going to do it yourself. There are a few videos of people using pulleys, but I was able to mount temporary legs on mine and tilt it up with the help of some rope and counterweights so I could walk it over to the wall. Once screwed in, I removed the legs. I suppose if you're really strong you can muscle this thing around, but that wouldn't be me....even 30 years ago in my prime.

Not me! I'm about 30 years past my prime. Wife and I muscled the 6k in to place using a small chain winch, it's rated at 500 pounds so I think it would be about the same job for the 12k. Key is to have the top two screws in place on the wall so the keyhole slots on the Growatt can slip on and support it while you get the rest of them in.

 

[PowerAssist]

That looks great - nice and clean, well done.

 

[novop]

Soft starters are def the way to go on any high draw items you can afford them on. Gives you more headroom for sustained load.

Be careful with this. Soft start kits can damage motors. A friend in HVAC has seen this happen on old ACs. Check with the manufacturer (of the pump, in this case) to see if they recommend using a soft start kit.

 

[Browse]

We have a warm week in NY and I finally got around to trying to start my 4-ton HVAC unit (with soft starter) with the Growatt 12k and 4 Lifepower4 batteries. So far, the Growatt has not been successful in starting the unit. It shuts down with an error 04 (low battery), so it must be the sag. I will reset the soft starter to re-learn it's startup and tomorrow I will try the system with my generator powering the Chargeverter to try to keep the voltage from sagging too much. I also have to check my Growatt settings to see if I need to make some tweaks there. Theoretically the system should be able to start the unit.