question

happyday avatar image
happyday asked

Unexpected Inverter overload

We are using a Multiplus 12/3000/120-50 120v Inverter powered by Battleborn batteries that are showing 100% full (600Ah).

ISSUE: Approximately 15 secs after turning power on to our Bosch 3000 T water heater, the inverter flashes the low battery light, then the overload light flashes. The inverter stops working.

While it is on with power requested by the water heater, the SmartBMV software shows current = -120A, Power = -1454W.


Note: When I plug the water heater into an extension cord from our house, the Kill-A-Watt shows 10.85A 1235W.


Note: The water heater is on its own circuit. We use other circuits. For example, one for a microwave that appears to be working as expected.


I am looking for guidance/advice on how to get this AC circuit working as expected. The challenge does not appear to be the water heater since it works fine when powered from our house.


Thank you.

Phoenix Inverter
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4 Answers
rslifkin avatar image
rslifkin answered ·

What is the battery voltage doing leading up to the overload? And how big is the battery bank feeding the Multiplus?

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happyday avatar image
happyday answered ·

Thank you for your reply.


Screen video showing the characteristics before and during an AC Current draw. In this case, a Dremel plugged into one of the AC plugs.

The battery bank is 600Ah (6 100 Ah Battery Born batteries).

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Justin Cook avatar image
Justin Cook answered ·

Hi @happyday, welcome to the Community!

There could be a few things going on here, depending on your system and how everything is connected. If you get a moment, please post photos or a diagram showing how your battery bank is connected together, and how the Multi is connected to the bank; that will help us rule out a couple of the common issues that we see. Improperly paralleled batteries, for instance, could result in a low battery/overload scenario if the battery bank is being discharged unequally under heavy load (~120A would count as a heavy load), and likewise if the batteries were not all fully charged prior to connection in parallel and so are out of balance; we might also see this behavior in a number of other scenarios, thus why photos of the entire installation and a schematic would be extremely useful in being able to provide assistance.

It is also possible that the Multi needs a firmware update, as a couple of firmware versions were given to spurious overload faults; what firmware version do you currently have installed?

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happyday avatar image happyday commented ·

Thank you Justin. I have written up our schematic (please scroll down until you see the schematic) that includes images from the install. I am excited for your feedback. Good point about updating the firmware. I haven't done that I'll google about until i figure out how to do it and then give it a go.

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happyday avatar image happyday commented ·

Hmm... to update the firmware looks like I need to VE connect to USB cable. $70. WHOA...for a cable?

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cleaver avatar image cleaver happyday commented ·

I've seen improper connections cause the overloads. I actually made the mistake myself. Check for loose connections and improper sized wire. With that many batteries I hope your running 4/0 wire.

Do you know the size of wire used for battery connections. Quite often the wire is good enough for charging but when demand goes big. the wire just can let enough power to flow back and it will overload.

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happyday avatar image happyday cleaver commented ·

Thank you for your reply @cleaver. I am using 2/0 copper. I am using this size because cables are all less than 6 feet, and assumed max amps at any one time is 30A. Which as I write this I noted an anomaly when the water heater was being used. It registered a far greater amp pull...hmmm..

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seb71 avatar image seb71 happyday commented ·

30A from a 12V battery would be 360W.

I think you mix/confuse AC amps (at 120V) with DC amps (at 12V).

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happyday avatar image happyday seb71 commented ·

I do not think I did? I am assuming a 120V max load of 30A I apologize for not understanding your point. I admit i am not that smart.

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seb71 avatar image seb71 happyday commented ·

You were talking about using 2/0 battery cables. Sized for maximum 30A:

I am using 2/0 copper. I am using this size because cables are all less than 6 feet, and assumed max amps at any one time is 30A.


Then you wrote:

Which as I write this I noted an anomaly when the water heater was being used. It registered a far greater amp pull...hmmm..

Probably talking about those 120A your BMV showed when using the water heater.


While it is on with power requested by the water heater, the SmartBMV software shows current = -120A, Power = -1454W.


And here you measured "only" 10.85A drain by the water heater:

Note: When I plug the water heater into an extension cord from our house, the Kill-A-Watt shows 10.85A 1235W.


You can directly compare (between AC side and DC side) power draws, but not current draws .

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nickdb avatar image
nickdb answered ·

Have you tried updating to 4.81 firmware?

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happyday avatar image happyday commented ·

@nickdb - thank you. I haven't. Is there something in the updated firmware that you believe is important or does this makes sense since there seems to be a problem?


Does this mean I need to spend $70 on their cable to connect to my PC to upload the firmware? That seems to be the best for me. However, if this is the case, it strikes me as how expensive this cable is considering updating firmware on other devices (say my 3d printer) uses standard cables. After all, it IS just shoving bits from one place to another. It is unclear to me why firmware can't be updated from the UI via Bluetooth via an OTA (Over The Air) method.

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