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jm0278 avatar image
jm0278 asked

Multiplus Compact Won't Pass Through AC In Invert Mode?

Have a Multiplus Compact in an RV with Battle Born lithium batteries. Preparing the RV for a trip in winter temps: upper 20's F/ -2C. I plugged the RV into shore power and intended to use electric heaters to warm the interior. I did not want the batteries to charge at all due to the low temperatures (low temp charging can damage lithium batteries), so I tried setting the Multiplus to "Invert" mode instead of "On" and it would not pass through the available AC shore power that I wanted to use to run electric heaters.

I used an extension cord to bypass the Multi along with a portable catalytic heater to bring the batteries up to temp. When I switched the Multi to "Charge" I had AC pass through. And, of course, when set to "On" there was pass-through. But no pass-through when set to Invert.

Does this sound correct, functioning as expected?

TIA


Jim

MultiPlus Quattro Inverter Charger
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2 Answers
David Kroher avatar image
David Kroher answered ·

Battleborn batteries have an internal BMS and temp sensor that will prevent a charge when below freezing. You are trying to do something that is already performed by the BMS.

Battle Born Batteries protect themselves from charging in cold temperatures and 
won’t accept a charge once the internal cell temperature drops to 24°F. At this 
point they will continue to discharge even down to -4°F. At this temperature we 
recommend no longer pulling power to avoid damaging the batteries.
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jm0278 avatar image jm0278 commented ·
@David Kroher Yep, I was thinking about that. I decided not to trust the low-temp protection, though. There's a chance it wouldn't work, but more importantly, I'm assuming Battle Born set the cutoff temp very close to the point at which the batteries would actually be damaged and I just wasn't comfortable with way the risks were stacking up.
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Kevin Windrem avatar image
Kevin Windrem answered ·

The AC input to the Multi is ignored in Inverter Only mode so what you are seeing is correct.

You may wish to install a bypass switch around the inverter AC in-out so that you can shut down the Multi and still have AC power in the RV. I did this in mine using a 30 amp double-pole-double-throw switch. You need to switch the hot and neutral leads going to your distribution panel between incoming shore power and the output of the inverter. the input to the Multi can remain connected to shore power.

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jsimps707 avatar image jsimps707 commented ·

Hi Kevin,

Thanks for the idea. I'm going to do the same on my system. Which switch did you install?

Thanks.

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Kevin Windrem avatar image Kevin Windrem jsimps707 commented ·
Shore power to both the Multi and the "bypass" side of the switch. Inverter out to the "normal" side of the switch. Distribution panel to the switch common (output).

I have a breaker in the shore power line before it goes to the Multi and bypass side of the switch. I have a breaker on the output side of the switch also but if you have a master breaker in your distribution panel, that will serve.

Make sure you switch both hot and neutral wires. If you have a 50 amp shore power connection, then you'll need to switch both hots if they both go to an inverter

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jsimps707 avatar image jsimps707 Kevin Windrem commented ·
Awesome. Thanks for further clarifying. I'm only 30A. Any suggestions for a quality switch?
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