# ssmith1952: AC inverter shuts solar system down

This discussion was created from comments split from: Solar setup help..
«1

• Registered Users Posts: 25 ✭✭

HELP

I have set up two 100 watt solar panels in parallel, running into a 30 watt control box using one 12 v deep cel sealed battery with attached 1100 watt inverter.

everything charges well. Battery at 100% and about 13.5 volts

when I turn on the inverter ( with nothing plugged into it), the battery drains and the controller shuts down.

However, when hooking inverter directly to the battery, it registers and holds at 13:4 volts.

What is happening here or what am I doing wrong?

Welcome to the forum S.Smith,

I don't know what solar charge controller you have, but if you are plugging the AC inverter DC input into the Solar Charge Controller's "output"--That is usually not a good idea.

An 1,100 Watt AC inverter can draw:

• 1,100 Watt * 1/0.85 AC inverter eff * 1/10.5 battery cutoff = 123 Amps at full load

And most charge controllers only have around 8-20 amp LVD output (low voltage disconnects). And remember, if you are starting a large motor, the inverter can draw upwards of 2x rated input current (~246 amps).

And, can you tell us a bit more about your inverter... A very efficient AC inverter draws something like 6-20 Watts (0.5 to ~2 amps @ 12 volts) just to turn on. And some less efficient inverters can draw 20-40 Watts or more.

In general, the correct place to connect your AC inverter is directly to the Battery Bus (usually with a circuit breaker or fuse to protect the wiring against short circuits).

Can you tell us a bit more about your system? Battery bank AH capacity, solar charge controller and AC inverter name/models, and what you want to use the system for (backup power, camping, running tools, etc.)?

Just to give you an idea... Your 200 Watt solar array in a reasonably sunny location would produce around:

• 200 Watts * 0.52 off grid system eff * 5 hours of sun per day = 520 Watt*Hours per reasonably sunny day (usually not winter)

Your 1,100 Watt AC inverter would use 100% of the typical solar arvest in about 1/2 an hour...

-Bill

Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 4,496 ✭✭✭✭✭

Is the "30 watt control box" actually a charge controller, or could it be a 30w load controller, or ?. It may help to know exactly what it is, and how it's wired.

Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Solar Expert Posts: 5,729 ✭✭✭✭✭

Most charge controllers will specifically state NOT to hook up an inverter to the 'load' terminals. Those terminals are typically for stand alone systems for lights or other minimal loads. Their terminals usually can't even handle a large wire even for a 1100 watt inverter, which with a quick thought would be 90 amps or 6gauge wire minimum. (From my feeble mind)

Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Solar Expert Posts: 9,511 ✭✭✭✭✭

200w of panels and a 30w control box ? How can you expect a 30w box to control 200w ?

perhaps it's a nomenclature problem. Maybe it's a 30A charge controller ?

Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,

• Registered Users Posts: 25 ✭✭

2 100 watt renogy solar panels connected in parallel connected to a 30watt charge controller (also renogy) in turn connected to 12v deep cell sealed battery (agm 100AH). out going connections are connected to the battery. Inverter KR1100 (Kreiger) connected directly to battery terminals and nothing else. All connections on battery are made to dual terminal post connections. When inverter is hooked to this, it blows everything and drains the battery. When inverter is hooked directly to another battery, it show voltage at 13.4v and holds. What am I doing wrong?

• Registered Users Posts: 25 ✭✭

30 volt charge controller not 30watts. Thanks for all the comments and questions. I still need help

• Registered Users Posts: 25 ✭✭

HELP

• Registered Users Posts: 25 ✭✭

30AMP charge controller not 30volts

• Solar Expert Posts: 1,654 ✭✭✭✭

What do you mean by "It blows everything"

Sounds like you are either using a defective battery or are connecting the battery incorrectly.

2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

• Registered Users Posts: 25 ✭✭

Ok blows everything isn’t the correct terminology. The inverter is connected correctly to the battery. Pos to pos. Neg to neg. when the inverter is turned on, it registers 13.4 v and rapidly goes down to 10v (about 3secs). I hear a pop or snap if you prefer, the inverter turns off, the charge controller turns off and the battery is discharged. When the charge controller is reconnected it shows the battery is discharged and nothing is charging at that time. Unconnected the battery and charge with charger and start again. I’ve done this with 2 batteries. I know that this is damaging to the battery and don’t want to do it again. Would it have anything to do with the connections or wiring?

It sounds like the battery(ies) is not any good. Or at the very minimum is pretty much zero state of charge.

Can you tell us a bit more about your battery (flooded cell/sealed)? Its Amp*Hour capacity? Or BCI battery size?

To recharge this battery, it needs to be brought back up to 14.2 to 14.8 volts (depending on type of battery, temperature) and held for 6-8 hours before the battery is 100% charged (if it will take a charge).

13.4 volts is "floating"--Basically just keeping the battery from self discharging.

If the system is in full sun, the solar panels should keep the battery voltage up enough to power the inverter (with 100 watt or less) load...

-Bill

Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 4,496 ✭✭✭✭✭

Is the controller positive or negative ground (I think they make both)?

Are any grounds connected (panel, battery, loads)?

Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Registered Users Posts: 25 ✭✭

To repeat, the battery is a sealed deep cel marine battery. AGM 100AH. The panels are in full sun daily. There are no grounds connected.

• Registered Users Posts: 25 ✭✭

Batteries were charged for about 20 hrs

• Registered Users Posts: 25 ✭✭

Battery meter I used said 100% @ 14.5 volts on both

If the batteries where in good shape and held at 14.5 volts (or even reached 14.5 volts), then to discharge the bank to 10.5 volts or less in a few seconds--That would suggest that drawing 100's to 1,000 amps of current... Not just drawing 2 amps.

If your wiring is too long, too small of diameter, bad electrical connections, etc., you could have a "wiring issue" -- But it does not sound like it (assuming you are measuring the battery terminal voltage).

Longer term, you might want to get a DC Current Clamp type Digital Multi-Meter to help you figure out how much current is flowing in your system when charging and discharging.... Since you have sealed cells, you cannot use a hydrometer.

Normally, for a 200 AH @ 12 volt battery bank, I would be suggesting around a 250-500 Watt maximum AC inverter. A deep cycle lead acid battery bank cannot really reliably supply much more energy than that for more than a few minutes at a time.

But since your inverter is apparently drawing the bank "dead" with no AC loads, it really sounds like failing battery bank (why it failed, is another set of questions).

-Bill

Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 25 ✭✭

The battery I have is a 100 AH. The wires, however, are quite long at this time. So you think shortening them may help? Was planning to shorten once I got the darn system working. Both batteries I have tried were brand new and fully charged. I don’t mind buying a smaller inverter but I want to use it to do more than charge my phone. Plus, are you telling me that, thru the inverter that I will only be able to use it for a few minutes? I’m quite confused now.

• Registered Users Posts: 437 ✭✭✭✭

You should not even be thinking about charging a phone with a 110 watt inverter There are 12 volt DC chargers available. Either your inverter is blown or you have failing batteries

2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
• Registered Users Posts: 4,496 ✭✭✭✭✭

A couple of other things to check:

- confirm the battery is connected to the controller BATT terminals, not the load terminals.

- confirm BATT terminal connections are made first, and pv panel connections after.

I assume you haven't fused the inverter to battery connection (it appears a fuse and holder are included with the inverter?).

I'm a bit confused by your statement in first post "However, when hooking the inverter directly to battery", it works. In a later post, you mention a "dual terminal post connections". I assume you mean a battery connector like this?

So there's a positive from controller, and a positive from inverter going to the above dual terminal on the battery positive, and likewise for negatives to battery negative?

Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter

Watts is a rate--Like Gallons per Hour

Watt*Hours is an amount--Like Gallons total

So, if you have a 100 AH @ 12 volt battery, its storage capacity is:

• 100 AH * 12 volts ~ 1,200 Watt*Hours

Your cell phone will take about 1.7 amps * 5 volts * 2 hours (at most) to charge (from dead):

• 1.7 amps * 5 volts * 2 hours = 17 Watt*Hours (total energy from USB charger)

You could, in theory, fill your cell phone:

• 1,200 WH storage / 17 Watt*hours (phone 0%-100% state of charge) = 70.6 times

Your AC inverter, if it is a "cheap model", could draw around 20 Watts... If you ran your inverter for 2 hours to charge the phone:

• 20 watts * 2 hours = 40 Watt*Hours -- Just running the AC charger because it is 'on'

When your phone would only take 17 Watt*Hours (at most) to recharge. The total from the battery would be for 2 hours of charging 17 WH phone+40 WH inverter=57 WH total

• 57 WH via AC charger / 17 WH via USB charger = 3.4 times more energy to charge your phone through an AC inverter

The above numbers are very rough--But close enough to give you a good idea of why using a relatively large AC inverter to charge a small cell phone is not the most energy efficient method.

For example, you can get a 12-24 VDC input USB charger what would be better than ~95% efficient:

https://www.amazon.com/Anker-Charger-Compact-Delivery-PowerDrive/dp/B07GZ78R6D

How long you can use the inverter on your 12 volt @ 100 AH battery bank, really depends on the loads--

OK, I think this is your AC inverter:

https://www.kriegermfg.com/product/kr1100/#

The specs say that is draws only ~0.5 amps @ 12 volts (0.5a*12v=6watts)--That is actually very low Tare Loss for an 1,100 Watt AC inverter.

The only other reason I could see it working on one "good battery" and failing on another "good battery" is if you got the + and - Lead reversed (connected the AC inverter "backwards" to the battery). Some electrics use a "diode shunt" across their DC input to protect against connecting things backwards. If you were to connect the AC inverter backwards, the diode inside the inverter shorts out the battery bank and pops a fuse or circuit breaker.

One other generally "warning", you have to really use bolted up electrical connections to connect your AC inverter to the 12 volt battery bank. If you, for example, just try to use automotive jumper cables, there is a good chance the inverter will not even start (jumper cables do not make a "good enough" electrical connection).

Also, this is (I think) an MSW (modified sine/square wave) AC inverter... There are "grounding issues" with most MSW AC inverters (do not wire your MSW inverter into a household breaker panel)--MSW inverters do not "like" their AC output with a "grounded bonded AC neutral/white wire"... It creates a short circuit between the "ground referenced" AC output back to the ground reference DC negative battery bus (if you are using grounds in the system).

Do you have a wiring diagram you can post? And/or a photograph of your battery+inverter wiring?

I think their is a disconnect between what you are doing, and what we think you are doing. Some drawings*&pictures could help.

-Bill

Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 25 ✭✭

Battery is connected to the charge control terminals

battery is connected first to the charge controller, then pv wires are connected to the charge controller

there definitely is a fuse between the inverter and the battery

pos/ pos control charger/inverter to positive battery terminal, correct and neg to neg

when I said that we connected inverter directly to battery, what I meant was one person held the inverter cables directly onto the terminals and the other person held the inverter, turned it on and read the display. Worked

No jumper cables have been used and there are no grounds connected

• Registered Users Posts: 25 ✭✭

Pictures to come soon

• Registered Users Posts: 25 ✭✭
• Registered Users Posts: 4,496 ✭✭✭✭✭

What are the thinner (12ga?) wires going to the battery for? I see a pair of thick (8ga?) black wires going to the controller, and a red and a black (16ga?) apparently going to the meter sitting on the battery, but can't see where the two slightly thicker black ones go. Something above and to the left of the controller?

Something I like to do when using one colour (black) for both polarities is mark the designated positive wire with red tape and double check for continuity on the marked wire, and again for correct polarity before final connection. I get mixed up too easily otherwise ;-)

Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Registered Users Posts: 25 ✭✭

Those wires are for the exhaust fan

• Registered Users Posts: 25 ✭✭

I still need help before I have to call someone to pay to help me. I have another inverter coming this Friday. Maybe that will make a dif.

• Registered Users Posts: 25 ✭✭

Otherwise I just may throw in the towel.

The setup looks OK... And the 14.2 voltage when charging is correct for a sealed lead acid battery.

The exhaust fan should have a 2-3 amp fuse (or so, depending on the fan) to protect that wiring against shorts.

Also, how much power does the fan draw, and how many hours a day do you run it? If you run even a small fan 24x hours per day, it can use most of the energy harvested from your solar panels.

Can you show a picture of how you are connecting the AC inverter?

The cables are a bit long... It is better to run them side by side and short/direct runs side by side for the +/- cables (bundle tie together). But, I don't see them as being a cause of the problems you are having.

If the battery voltage (as measured at the battery terminals) is dropping that quickly (a few seconds with the inverter just "turned on" and no AC loads--It would seem that you have a bad battery.

-Bill

Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 4,496 ✭✭✭✭✭

I also don't see any obvious problems with wiring that would account for your problem. As Bill noted, the fan should be fused (the meter too, for that matter), but that wouldn't solve your problem.

Since the inverter apparently works when connected to another battery, Bill's notion that the battery has lost capacity seems quite possible. Do you know the amp draw on the fan? Does it drain the battery faster than expected without solar?

Either that, or a bad/shorted connection to the inverter. As mentioned earlier, taking a good, fully charged, 100ah battery down to 10v cut-off in a matter of seconds takes a lot of current. Enough that I'd expect something to get pretty hot in the process.

Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter