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Discussion Starter #1
My solar system was working great. Then it started misbehaving in two different ways: One is that when I first turn the inverter on, it sometimes squeals. If I turn it off and then on again, it's fine. The other is that it squeals if I try to run the kettle.

I talked to Krieger, the folks who made my inverter. They noted that the voltage drops before it starts squealing, and so they think it's a problem with the battery system. I tested it using jumper cables off the van battery, with the battery running, and got the same behavior, even with my 220-amp alternator. They said that makes sense because it's a car battery, and they still think the problem is the batteries.

I tested the voltage on the batteries, disconnecting them from one another, and they each test at 13 volts. But still, there could be a problem there.

One possibility the inverter folks mentioned (they're very nice and seem competent, btw) is that the wire connecting my batteries may be too small. Anyone know what gauge I should have used? I'm not sure what gauge I have -- I'm away from home and don't have a way of figuring that out right now.

Any other ideas what could be going on? The whole system is only a couple of months old. The panels and controller are Renogy, and the batteries are three 110-amp Duracell Ultra deep cycles.

TIA! BTW, my cell service is spotty right now, so I may be a bit slow responding.
 

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Krieger supplied wire (right?) and it should be large enough. The voltage 11.1 will NOT run the inverter. The problem is with the batteries.
Remove the wires from your batteries one at a time and clean the ends with sandpaper and reinstall them on the cleaned terminals. I suspect a loose or dirty connection.
Run your van until your solar controller shows the batteries are full. If the voltage drops to under 12 under load you have a defective battery. They can be tested.
BTW this is NOT a solar problem. It’s an inverter problem.
 

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Discussion Starter #7
Thanks, RD. I'll do that.

Does it surprise you that the same problem happened with the van battery, given that it has a 220 amp alternator?

Also, what I meant was that perhaps the wires connecting the batteries to one another aren't big enough, not the wires connecting the inverter to the batteries. Again, unfortunately, I'm not sure what size they are.
 

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Those should not be involved in running the inverter normally. Even too small wires there will charge the coach battery eventually. 4AGW is about the smallest you should have there. Many wires have it printed on them. That is not the problem either.
 

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I think the cables going to the inverter could be too small, or a bad connection.
When you said you measured 11.1V was that at the inverter or at the battery?
When you tried it with the van battery, & van running, where did you connect the jumper cables?
 

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2014, 138WB, High Roof, Gas, SW MT
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Hi,
It seems like the inverter supplier should have a recommendation for wire gage.

But, if they don't, you can estimate it as

Current = (inverter wattage) / ((12 volts) (0.9))

So, for a 2000 watt inverter, the current is about (2000) / (12 volts) (0.9) = 185 amps.

The 0.9 is the nominal inverter efficiency.

Then, use the BlueSea Circuit Wizard calculator to estimate the wire gage (which will depend strongly on the length of the wire): http://circuitwizard.bluesea.com/
Its asks you for allowed voltage drop -- I'd use 2%.

So, for the 2000 watt, 185 amp current draw and (say) 4 ft each way wire runs (8 ft total), 2% voltage drop, and 90C wire insulation, 30 minute load duration, I get AWG 0.

You might contact DuraCell and ask them what the maximum current your batteries will support is, and make sure its not less than what is needed to run the inverter.
Agree with cleaning the terminals.

Seems like 11.1 volts when its running is too low -- too much voltage drop. So, too small wire gage, dirty terminals, terminal bolts not torqued down enough, or batteries that won't supply the required current are most likely problems.
I guess bad inverter, or (if its not a pure sine wave inverter) maybe a load that won't run on modified sine wave?

Gary
 

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Discussion Starter #11
Well... I just cranked down on all the nuts on the batteries, and the behavior was unchanged. Then I decided to double-check the tightness of the connections at the inverter, and in the process I managed (apparently) to hit the negative post with the end of the wrench as I was tightening the positive one, creating a big spark. And now the inverter is unresponsive.

Gah.

When I connected the inverter to the van battery, I ran jumper cables from the positive post of the van battery to the positive post of the inverter, and likewise with the negative posts. I'm using the cables supplied with the inverter to connect it to the batteries, and they're huge -- close to an inch in diameter. What I was wondering about was the wire that I used to connect the batteries to one another. They have lots of markings on them, but they're very hard to read and I don't know what they mean.
 

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Fixing the fuse may restore the inverter issue.

Please be very careful when tightening connections, etc. You were lucky! A much more serious situation is possible when a wrench or screwdriver crosses the negative and positive terminals on a battery...sometimes the wrench will cause enough current flow for it to "weld" itself to the battery terminals... this creates a situation where there is an unfused path from + to - on the battery (the wrench), and the huge current flow may cause the battery to explode! (think acid and metal flying in all directions)

Not trying to scare you but to create an awareness of the potentially hazardous situation that something as simple as a slipped wrench may cause. Best practice is to connect the negative battery terminal last... and with caution. Cover the positive terminal if possible.
 

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Get a volt meter and charge up the batteries. Put a small load on them like the fan and test across each one. They should each test 6.3 or close. If one is low it is bad and will need replacing. If they both read low it is unlikely they are charging properly.
 

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A much more serious situation is possible when a wrench or screwdriver crosses the negative and positive terminals on a battery...sometimes the wrench will cause enough current flow for it to "weld" itself to the battery terminals...
One of our forum members tested this on his lithium batteries . . . as we remember, he said it melted the wrench.
 

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Yikes.

So wait, what should read 6.3? The batteries? They're 12 volt batteries.
RD must be assuming that you have 2 6 V batteries. If you charge it up and then let it sit overnight with no load (if possible), the open circuit voltage should be 12.8-13.0 (depends on the battery). It will drop with load, but shouldn't get near 11.2 unless it is almost dead or the load is huge.
 

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Yes I thought you had 2- 6 volters. So with a small load it should read 12.6+. The problem with two 12 volters in parallel is you can’t read the voltage of ONE of them to test unless you disconnect the other. If you have one bad that may be the only way to test.
 

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Discussion Starter #20
Well, I'm plum stumped. The connections are all tight and clean -- I checked them myself and had someone else do it too. The wire is an adequate size, according to the place I bought the batteries from. I had them check the batteries, and they're in excellent shape with plenty of storage. I'm getting the same behavior on two different inverters. So, um, what's left?

The only thing I can see to do now is to have an electrician look at it. I'm not sure who to go to for that, honestly. I've called solar places, and they haven't even returned my phone call.
 
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