I’ve had my set up for about a year now, but the last couple weeks, it’s acting weird. Mostly it seems to stop charging when the battery gets to around 50%ish
To start, I read the voltage of the battery and looked at the BMS, they both read the same voltage. However, on the Victron App, the voltage is not even close.
Why is there such a difference?
First off you are reading different things, your battery terminals via the BMS and the multimeter and your MPPT terminals from Victron Connect. The proper test is using the multimeter on the MPPT. The MPPT can be higher due to poor resistance in the cables, poor connections, loose plugs and sockets, loose fuses, cheap breakers etc. Such a poor connection results in voltage drop and under charging.
Ok, I can measure the voltage at the mppt.
I did read the voltage at battery terminals when it’s unplug and it did read the 13.0v. If there was a loose/bad connection, wouldn’t the voltage be lower (sorry, I’m not the most experienced electrician).
Previously, I did switch the switch the cable from the MPPT to the battery and had the same voltage readings. I’ve also tried this with a second battery and have the same reading differences.
So I’ve swapped cables and swapped batteries, but have the same results.
Are you measuring while it is producing power form solar or while it is just connected to the battery?
Just as an FYI for charging to happen - a higher potential (voltage) has to happen so the power flows.
I measured while connected to solar panels and battery. In addition, I also measured the battery when disconnected. The actual battery voltage was the same 13.0v as measured in the posts.
I guess a basic question is, why would the app say the battery voltage is 14v when the battery is actually only 13v? It did not do this before, it only started happening about a month ago.
It also causes the system to enter float when the battery is only 13.0v. I haven’t been able to get much of a charge because of this new issue.
The app does not show the battery voltage, it shows the output voltage of the MPPT. These are not the same thing if current is flowing. In your photo I see what looks like an Anderson plug, so do you disconnect and reconnect this, if so is it working loose giving a high resistance and voltage drop. You do not need much resistance in your cables between the MPPT and battery to make the MPPT voltage 14.1V with a battery voltage of 13.0V and 15Amps flowing.
Think of the cable as a water hosepipe, voltage is pressure, amps/ current is flow. Resistance is a kink in the pipe. You may have high pressure at the tap, but if your hosepipe is kinked you will have much lower pressure at the outlet.
