rwkoehler avatar image

How to connect a Victron battery protect between power inverter and battery

I currently have a small, off grid solar system - 100amp deep cycle sealed lead acid battery, 100 watt foldable solar panel, 20A charge controller and a 12V/750watt power inverter.

The power inverter is currently connected directly to the battery but I am concerned about over discharge if there are multiple consecutive cloudy days.

I purchased a 100A Victron battery protect. I am confused as to how to connect it to the battery and power inverter in order for it to prevent the battery from being over discharged.

  1. Does the power inverter connect to the battery protect and then the battery connect to the battery?
  2. Which connection do I use on the battery connect - IN or OUT?
  3. Where does the battery connect negative/black wire connect?

Battery Protect
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
michelg avatar image
michelg answered ·

Hi rwkoehler, this is how my setup is done. A picture is worth a thousand words.

The Smart Protect 220A is linked to a DC DISCONNECT Switch to provide power to 2 inverters.

The Top black red cable over the SP is bringing the power from the SmartSolar MPPT.

The Bottom black red cable is linked to a 125A fuse, linked to a 450A switch (2 battery banks)

It works perfectly, when it disconnects, and the voltage gets to the reconnection limit, it will take a few minutes to release the power and reconnect the inverter. The main inverter is limited to 100A and the backup to 32A.

Let me know if you have some questions.



1 comment
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Hi @MichelG,

This is a forbidden connection method.

I understand that it works now, and indeed it may continue working for an unknown period of time... but it will fail, and depending on how it fails, you may suffer damage to your batteries if the BP does not disconnect when it should.

Please connect Victron components in accordance with their manuals to avoid component failure and/or possible system damage that will not be covered by warranty.

Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

Hi @rwkoehler, welcome to the Community!

You must not use a BatteryProtect to directly disconnect the DC power supply of your inverter - this will, sooner or later, destroy the BP's logic. This is an expressly forbidden connection.

You may use the BatteryProtect to trigger the inverter's remote on/off pinout if so equipped, or perhaps to trigger an external relay that will then interrupt the inverter's DC supply, if it is not equipped with a remote on/off pinout, but you must not connect the BatteryProtect between the inverter and the battery.

Please see the user manual for acceptable connection methods.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Justin Cook: Ok, you say what I should NOT do. But what I'm asking for is how TO connect the battery connect in order to provide the over discharge protection. If the manual was clear, I would not be asking this question. Perhaps the manual is more clear to someone more technically familiar with solar. I am not. I am just asking what to connect to what, and in what order. Logically, it seems that in order to be able to determine whether or not the battery is in danger of over discharge, it would seem that the battery connect would HAVE to be between the thing drawing power from the battery and the battery itself. That seems to not agree with what you are saying.

He also wrote how you can connect it.

The problem is the high inrush current of the inverter.

The manual is clear about not connecting an inverter directly to the BP (installation point 4).

Maybe if you say us what kind of inverter you have we can say you how to connect it.

If you don't know what to do you should hire someone who knows.

michelg avatar image michelg Matthias Lange - DE ·

In my setup that you can see on the photo, the main inverter has a delay between the moment you switch it on, and when it starts providing power. And the backup inverter is a Phoenix 24/800.

The main reason I installed an oversized Battery Protect is to avoid overloading it, with theorical inrush currents.

@MichelG, inrush current is too fast to measure with most multimeters, and can be over 5x the maximum running current of the device.

"Oversizing" your BatteryProtect is not the solution here - the only reliable solution is to connect the BatteryProtect in a permitted configuration.

michelg avatar image michelg Justin Cook - Bay Marine Supply USA ♦ ·

Hi Justin, thanks for the information.

AFAIK, there is a startup circuit limiting the inrush current. That's the reason it takes several seconds before getting the inverter "ON", and then other several seconds before starting to invert.

I do use FLUKE instruments to check every point of my installation, and did not had any issues.