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Old 03-22-2021, 07:24 PM   #21
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reread and had missed the battery location but still those feeders are undersized.

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Old 03-22-2021, 07:36 PM   #22
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Originally Posted by Rivetboy View Post
You are feeding your 3000 watt inverter with 2/0 cable . 2/0 is adequate for a 1000 watt inverter. How far to the batteries with those undersized feeders? 4/0 feeders for a 1500 watt to 3000 watt inverter. The inverter protection breaker is 250 amps. This is way to small for a 3000 watt inverter. Put a meter on the batteries and start the inverter. How far below 12.xx volts did it sag to? My opinion is you have inadeqaute power supplied to the inverter to feed the load you are attempting to run..
The batteries are only a few inches from the inverter.

As I mentioned in my previous reply, I believe that the wiring is actually upgraded beyond what is listed on the diagram. Is there a way I can tell visually what kind of cable it is?

I do not have a handheld meter. There is a monitor display inside the bus, would that have the information youíre looking for?

Is the short answer to my question, ďhave an electrician look at it?Ē I donít really understand this stuff and feel like this is too important of a system for me to fumble around with trying to figure stuff out.
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Old 03-22-2021, 07:48 PM   #23
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oops. duplicate comments
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Old 03-22-2021, 07:52 PM   #24
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I am in Virginia too, close to Fredericksburg. I could look at it. It is not my business, so just one skoolie to another. I am believing as others have said the wire to the inverter is likely to small. If you are lucky there is enough wire between the batteries and inverter that the wire gauge will be visible on the wire.
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Old 03-22-2021, 08:03 PM   #25
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I read the wire size off of your picture. The cable is 2/0. Go to the Renogy website and see what the say for size and protection.
By a $20 meter from home depot. Then play with it and learn how to use it.
Good luck
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Old 03-22-2021, 08:36 PM   #26
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I am in Virginia too, close to Fredericksburg. I could look at it. It is not my business, so just one skoolie to another. I am believing as others have said the wire to the inverter is likely to small. If you are lucky there is enough wire between the batteries and inverter that the wire gauge will be visible on the wire.
I appreciate the offer, but no thank you. I have a couple of acquaintances nearby who are electricians, I'll just get one of them on it.

I was naively thinking this would be a super simple fix that I could do myself.
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Old 03-22-2021, 08:40 PM   #27
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Quote:
Originally Posted by Rivetboy View Post
You are feeding your 3000 watt inverter with 2/0 cable . 2/0 is adequate for a 1000 watt inverter. How far to the batteries with those undersized feeders? 4/0 feeders for a 1500 watt to 3000 watt inverter. The inverter protection breaker is 250 amps. This is way to small for a 3000 watt inverter. Put a meter on the batteries and start the inverter. How far below 12.xx volts did it sag to? My opinion is you have inadeqaute power supplied to the inverter to feed the load you are attempting to run..
Wire, Fuse and Breaker sizes for 12v/24v/48v:
https://www.altestore.com/howto/reco...-or-fuses-a62/

12v battery bank
3000w Inverter
400a max DC input to Inverter
400a DC fuse
250a Breaker
4/0 Wire

1200w (kettle) @ 12v = 100a
2000w (blow dryer) @ 12v = 166a
Even if you add 10% for inverter inefficiency, that's still ~183a.

I know enough to know not to play with electricity unless I'm really sure what I'm doing. So, with some knowledge, and just thinking out loud here, it seems even a 183a draw would not trip a 250a breaker.

Battery Bank:
I'm assuming that the two batteries are 12v each, in parallel (+ to +) and delivering 400ah total.

AGM - Figure a max 50% discharge level, that brings the batteries down to 200ah. Getting pretty close number wise, yet, that blow drying would need to be going for a pretty long time to drain a solid 200ah.

How do you know the batteries are always at 90% charge or higher? Where are you getting that information from?

I kind of get with RivetBoy thinks the battery bank is too small, yet I'm confused why the breaker would trip if there's NOT enough amps in the battery bank.

Overloads or shorts yeah, not enough energy....the appliance just wouldn't work.

Is my thinking correct?

Seems to me, it may be a short of some kind that only shows up with high loads.

Yet, I do agree that running those high loads makes me think some additional amp hours would be a good idea.

Looking forward to hearing what the solution is.
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Old 03-22-2021, 08:49 PM   #28
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...
How do you know the batteries are always at 90% charge or higher? Where are you getting that information from?
There is a system monitor screen installed inside the bus that shows the battery level as well as (I believe, not currently looking at it) power in/out.

Even after several consecutive cloudy/rainy days running a fridge and lights etc, the battery was only down to about 70% and that's the lowest I have ever seen it, so far.
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Old 03-22-2021, 08:59 PM   #29
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Not the battery bank to small the feeders from it to the inverter. Your guide indicates a 250 amp breaker using 4/0. 2/0 is not 4/0. Also, has the SOC of the bank been determined? What does that remote battery monitor sag to when the inverter goes online? Undersized feeders plus partially a discharged battery bank hit with a high wattage resistive load equals Trip.
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Old 03-22-2021, 09:30 PM   #30
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Quote:
Originally Posted by Rivetboy View Post
You are feeding your 3000 watt inverter with 2/0 cable . 2/0 is adequate for a 1000 watt inverter. How far to the batteries with those undersized feeders? 4/0 feeders for a 1500 watt to 3000 watt inverter. The inverter protection breaker is 250 amps. This is way to small for a 3000 watt inverter. Put a meter on the batteries and start the inverter. How far below 12.xx volts did it sag to? My opinion is you have inadeqaute power supplied to the inverter to feed the load you are attempting to run..
That sounds about right. Roughly 85 amps @ 12v per 1000w. Big wire, 350 MCM. Parallel runs of 2/0 THHN would work if the batteries are close by
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Old 03-22-2021, 09:33 PM   #31
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... Also, has the SOC of the bank been determined? What does that remote battery monitor sag to when the inverter goes online? Undersized feeders plus partially a discharged battery bank hit with a high wattage resistive load equals Trip.
Apologies, I don't understand what you're asking.

What is SOC?

And what do you mean by when the inverter goes online? It is always on. When I plugged the blowdryer directly into the inverter earlier and ran it for a few minutes, the battery monitor barely changed. I wasn't keeping special track of it at that time, but any drain was certainly not significant.
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Old 03-22-2021, 09:40 PM   #32
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I think youíre just pulling more than 250a or the breaker is a little too sensitive.

Your inverter isnít super high quality and likely inefficient at high loads, so you may be hitting the 250a threshold when things are on.

My suggestion would be in this order:

First make sure all the connections are clean and really tight. I just fixed a problem for someone that was similar caused by a corroded fuse terminal. If that doesnít fix it, I would try another breaker first, or maybe an inline 300a fuse (if 2/0 wire can support it). You might be able to diagnose this problem by comparing voltages at the batteries vs voltage at the inverter. If itís more than a tiny bit different your cabling is the problem. You can also try running things and seeing if anything in the wiring gets hot, if so the hot spot is your issue.

Third, I would upgrade to 4/0 wire first, then fourth, upgrade the inverter to a better unit.

Hope that helps.
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Old 03-22-2021, 09:44 PM   #33
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Quote:
Originally Posted by rffffffff View Post
I think youíre just pulling more than 250a or the breaker is a little too sensitive.

Your inverter isnít super high quality and likely inefficient at high loads, so you may be hitting the 250a threshold when things are on.

My suggestion would be in this order:

First make sure all the connections are clean and really tight. I just fixed a problem for someone that was similar caused by a corroded fuse terminal. If that doesnít fix it, I would try another breaker first, or maybe an inline 300a fuse (if 2/0 wire can support it). You might be able to diagnose this problem by comparing voltages at the batteries vs voltage at the inverter. If itís more than a tiny bit different your cabling is the problem. You can also try running things and seeing if anything in the wiring gets hot, if so the hot spot is your issue.

Third, I would upgrade to 4/0 wire first, then fourth, upgrade the inverter to a better unit.

Hope that helps.

Alternatively, if the ability to power things from the inverter directly works and not if youíre plugged in to the branch circuits you may have bad wiring or connections on the 120v side. Try different outlets and see if they all do it, if so then you have to look hard at at your ac wiring from the inverter to the sub panel.
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Old 03-22-2021, 09:51 PM   #34
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LBH, I think what they are saying is:

1) Whomever designed your system made it so it can run smaller AC loads, like the computer and such. But, when you plug in your large loads, 1200w+ the system can't handle it and the 250a breaker trips.

2) SOC = State of charge. How much charge is actually in your batteries. Your battery monitor may not be accurate. That's why they suggested you use a meter to see what the volts are at the battery terminals when you are running the blow dryer. Your batteries may not have enough charge or overall capacity.

3) Most of my electrical experience is with AC (homes), so the only time I'm familiar with a breaker tripping is with an overload, short, etc. Yet, if you think of a breaker of having a high and low range, it can trip when there's not enough charge.

4) Part of the reason the blow dryer runs fine at the inverter is because after the inverter are more breakers, wires, etc.. This creates more effort to push the current just enough to push your system outside of its low range and the breaker trips.

Summary:
You have too small of wires on the battery side of the inverter
You have too small of a charge or capacity at the batteries
You are asking too much of your system to run the larger loads

I THINK, this is what's basically, layman's terms, is being said.

I'll be corrected if I'm not right. LOL.
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Old 03-22-2021, 10:23 PM   #35
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OP actually has one of the better case scenarios for this (even though their batteries need to be at or near peak to support this use case). I think we can look past the DC side. Your diagram shows a "20A Fuse box", can you show us how it is connected to the inverter and the fuse box itself? That's looking like the problem to me now.
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Old 03-22-2021, 10:43 PM   #36
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OP actually has one of the better case scenarios for this (even though their batteries need to be at or near peak to support this use case). I think we can look past the DC side. Your diagram shows a "20A Fuse box", can you show us how it is connected to the inverter and the fuse box itself? That's looking like the problem to me now.
I saw that too Kaz, and maybe wrongly so, but I'm hoping that means it's not a "fuse box" but an AC panel with individual 20a fuses for key circuits (refrigerator if 110v), microwave, etc., and 20a for a series of non-dedicated outlets.

In addition to the panel, have we determined if anything else (AC or DC) is on when the breaker trips. If so, what is on and what kind of draw is it pulling?
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Old 03-23-2021, 02:43 AM   #37
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Quote:
Summary:
You have too small of wires on the battery side of the inverter
You have too small of a charge or capacity at the batteries
You are asking too much of your system to run the larger loads

I THINK, this is what's basically, layman's terms, is being said.

I'll be corrected if I'm not right. LOL.
I think you got it. If the battery voltage drops the amperage will rise to meet the wattage demand. Larger battery feeds and more battery capacity
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Old 03-23-2021, 07:03 AM   #38
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Quote:
Originally Posted by rffffffff View Post
I think youíre just pulling more than 250a or the breaker is a little too sensitive.

Your inverter isnít super high quality and likely inefficient at high loads, so you may be hitting the 250a threshold when things are on.

My suggestion would be in this order:

First make sure all the connections are clean and really tight. I just fixed a problem for someone that was similar caused by a corroded fuse terminal. If that doesnít fix it, I would try another breaker first, or maybe an inline 300a fuse (if 2/0 wire can support it). You might be able to diagnose this problem by comparing voltages at the batteries vs voltage at the inverter. If itís more than a tiny bit different your cabling is the problem. You can also try running things and seeing if anything in the wiring gets hot, if so the hot spot is your issue.

Third, I would upgrade to 4/0 wire first, then fourth, upgrade the inverter to a better unit.

Hope that helps.

All great points. A reminder the smaller the number on wire gauge the bigger the wire. So 2 gauge is larger then 4 gauge and will handle more amps.


I have 2 gauge for a 1000 watt inverter. Start up load often really spikes the amps. Watching a quick acting volt gauge, and amp gauge will show for example when the fridge comes on the voltage will drop a lot and the amps will jump up lot just for s second. Of course a fridge has a compressor to get going, and are notorious for needing huge start power in relation to running load.


After checking connections testing for actual amp draw on the dc side would be my next step.
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Old 03-23-2021, 08:25 AM   #39
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Thank you, everyone, for your input.

This has clearly become a situation that is outside of my DIY ability, and so I am going to have a professional look at it and see what’s up.

I’ll report back when I do to satisfy your curiosity.
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Old 03-23-2021, 09:16 AM   #40
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This could all be solved with a multimeter/amp clamp combo available at most hardware stores. Measure the dc amperage you're pulling and the voltage it's pulling it at.

But if you're blowing the 250 amp circuit breaker you have shown, it's likely because you're drawing more then 250 amps......

You can run all the simulations and figures that you want, and that's exactly what should be done when designing the circuit, but to actually troubleshoot issues, you need hard figures that you have measured, nothing speculative.

To get to the science behind this, Watts law states that watts = volts X amps. When the wattage is a fixed value like it is in our case, and the volts drop, amperage raises. This scenario has the ability to spiral out of control in battery systems because as the amp load on the battery increases, the battery volts will drop farther, causing the amps to increase even more, which turns into a vicious cycle. As a prior poster pointed out, your battery bank is inadaquate and likely not capable of running what your trying to do.

Maybe you need more batteries. Or maybe you need better batteries. Testing with a meter will tell you what you need to know.

You also should have 4/0 cable for 3000 watts on 12v. If you have 2/0 in use, it's too small.

What inverter are you using? What charge controller are you using? Maybe you can convert this system to a 24vdc system with 4 12v batteries in a parallel/series arrangement. Maybe you can arrange some 6v golf cart batteries.
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