question

liahskoolie avatar image
liahskoolie asked

Inverter loses charge every night. SOC reads 100%, but the inverter only turns on when the sun comes out.

img-0340.pngOur inverter doesn't seem to hold a charge anymore. We've only had this system for a couple of months. Everything was working perfectly. Out of nowhere we began to lose power in our RV in the middle of every night despite the SOC being very high and us using little electrical appliances during the night. The app shows the inverter is set to "off", despite trying to turn it on. Once the sun begins to rise, the app shows the inverter is still "off" while it is charging back up, and is usually at a super low voltage around 4-8V. After a few hours, it's up to around 13V, but then doesn't get much higher than that.


We have 3 lithium batteries connected that are fully charged. We see the inverter dies at night, and the app shows the low battery warning, yet the SOC is still very high (usually above 80%).

We believe the SOC trickles down to 80% because our lights are hardwired into the batteries.
img-0342.pngWe haven't had a problem for months up until now. We think it may have had to do with a recent software update. Also, we bought a space heater and used it in our outlets for a couple of days. We made sure our batteries didn't go below 70% while using it, just wanted to heat up the RV in the mornings. Sometimes, when using the heater, the power would cut out and then turn back on.


img-0341.pngWe've tried resetting everything to default, checking for updates, restarting the system - nothing works. Any help would be greatly appreciated.

Phoenix InverterSOCinverter current drawHot Water Diversion
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img-0340.png (274.6 KiB)
img-0342.png (352.6 KiB)
2 comments
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Our inverter doesn't seem to hold a charge anymore.

The battery is the one which does that.


super low voltage around 4-8V

That is very bad for the battery, if real.


Also, we bought a space heater and used it in our outlets for a couple of days.

That is a large load.


We believe the SOC trickles down to 80% because our lights are hardwired into the batteries.

You mean directly on the battery terminals?

Any other loads wired in the same way?

If loads (or chargers) are connected directly to the battery, the BMV SOC values are meaningless.


We have 3 lithium batteries connected that are fully charged.

What was the battery voltage?

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A lithium battery at 13,02V is at about 30% SOC (BMV screenshot)

Like others said, something is wrong with your settings.

  1. Charge you battery's with shore power untill the charger go in to float, then reset to 100%.

With 300Ah it is also better to change the tail current to 1.00% or max 1,50%.

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3 Answers
Paul B avatar image
Paul B answered ·

Please only use the SOC in conjunction with checking battery voltage at the time of failure. also please check the below video as it may help you understand how the SOC works

Suspect you have a flat battery issue. yes it may say 100% SOC this maybe very misleading at times VOLTAGE IS KING OF THE ROAD always compare to voltage and check the individual cell voltages if you have lithium

https://www.youtube.com/watch?v=mEN15Z_S4kE


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Alexandra avatar image
Alexandra answered ·

@liahskoolie

You have set on your shunt battery starts synchronised. So every time your system shuts down and restarts it is assuming the battery is full. So first step is to switch that off, it is giving you false soc.

Fully charge the batteries and you should be golden. Your batteries are shutting themselves down to protect themselves.

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Thank you so much! I switched off the battery starts synchronized. What should I do next? It’s been charging for a few hours and isn’t going over 13.5V. Should I turn off the inverter and then back on? Reset the batteries to default and re-enter the info?
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@liahskoolie


300ah will take quite a while if it was dead flat. What amperage are you charging at? And then was the multi /charging source also set to charge to the correct voltages?

For example if i use your origional post it is charging at 10A that will take over 30hours.

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Alexandra avatar image
Alexandra answered ·

@liahskoolie

A few other small changes (settings are for a bmv 700, bit the principles are the same) recommended by battleborn website.

Like you bank capacity is not 300ah but 3x99ah.

All loads should be connected to the load side of the shunt nothing should be directly connected to the battery, otherwise it also will not be able to calculate soc accurately.

Check your quick install manual.

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