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wscholtz asked

SmartSolar MPPT 100/15 raising battery voltage too high

Hi everyone.

I'm currently using a MPPT 100/15 with a 12V battery bank (2 x 12V 100Ah Lead Acid batteries in parallel) with 2x100W solar panels. The solar controller's settings are on 14.4V absorption and 13.9V float. The equalization voltage was set to 16.2V but it is disabled and I've never manually triggered the equalization.

I also have a BlueSmart 12/15 charger which I set on power supply mode during the day with a voltage of 13.4V while the solar panels provide power to my system. It's charge mode's settings are similar to the solar charge controller (14.4V absorption, 13.8V float and 13.4V storage).

Earlier today I noticed a strange series of events.

1. The power from my solar panels dropped from around 130W to zero. (it's a sunny day, panels had no shade, I measured the panel voltages and everything seemed fine on the panels and at the cable going into the solar charge controller when unplugged - around 70-80V open circuit voltage). After this the Victron app stated that the charging state is "Off".
2. The reported voltage on the victron connect app showed that the voltage from my solar panels dropped from the normal 65-ish Volts to just above the battery voltage. This was thus different to what I measured with my multimeter at the cables going into the charge controller while they were unplugged.
3. I changed the BlueSmart charger from power supply mode to charger mode, detached the solar panels and measured their voltage (mentioned in point 1).
4. I re-attached the solar panels.
5. Soon thereafter I heard a boiling sound coming from the batteries and noticed the battery voltage going over 15V and steadily climbing.
6. I immediately switched off the BlueSmart charger, but it had no effect.
7. I then detached the solar panels which brought the voltage down again.
8. To investigate I tested this by leaving the BlueSmart charger switched off, and re-attached the solar panels. The voltage started climbing again.

Afterwards I took some screenshots (below). It's quite clear on the screenshots that the voltage climbed each time I re-attached the solar panels.

What I'm seeing is:

- The solar charge controller is in an "off" state.
- The charging current was showing zero
- The power and current from the solar panels were showing zero
- The battery voltage kept on climbing and I heard the Lead Acid batteries boiling.
- Even though an audible boiling sound came from the batteries, the solar power and current and battery charge current all showed zero.

What am I missing?

It almost seem like the battery voltage was chasing the solar voltage. I don't think this was an equalization happening because during "step 7" I did decrease the equalization voltage to 14.5V and the battery voltage still climbed past it to 16V+ before I detached the panels again.

Did my SmartSolar MPPT charge controller break? It's only a few months old now.
Did it perhaps somehow decide the batteries are 24? I double checked the settings and the battery is set to 12V. At no point in time was the battery cables disconnected.

I will be testing everything again in the morning when the sun is back up and if anything changes I will comment on this post.


MPPT SmartSolarHelpovervoltagemppt overvoltage
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wscholtz avatar image wscholtz commented ·
This question has been a little more quiet than I hoped, but I'll keep on updating in case anyone else experiences something similar.

I spoke with a local installer that work with Victron products. He mentioned that he has not seen this behavior before and he suspected that a MOSFET failed into an open position which could have connected the PV input to the battery output.

Based on the discussion with him I have requested a replacement unit from the vendor I bought this unit from. Hoping they will sort it out with Victron for me.
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wscholtz answered ·

I tested again this morning. Same issue. I unplugged the normal IP67 BlueSmart charger from the beginning to make 100% it doesn't interfere.

As soon as I connect the solar panels, the battery voltage shoots up to above 16V, even though the solar panel values aren't showing any current or power (same as before).

Next test I disconnected the battery bank and the solar panels. Charge controller switched off. I left it for a few minutes. Then connected only the solar panels. The solar panel voltage is now showing correctly. It's actually about the open circuit voltage being displayed. However, the battery voltage is now also showing close to the the solar panel voltage! This was very surprising to me, because the battery bank was still disconnected so this is telling me that the "battery voltage" being read is not purely from the battery terminals but somehow connected to the solar panels. See image below.


For what it's worth: The "Why is the charger off?" reason is showing as "#OR1: Insufficient PV power". Seeing as the battery was still disconnected, I would rather have expected this to tell me that there is no battery connected and not "Insufficient PV power".

I'm starting to think there might have been some kind of a short that bypasses the components that handle the battery output voltage which separates the PV and batteries. Thus connecting the PV directly to the batteries. Is this possible? Something anyone has heard of before?

The setting are still set to 12V battery, 14.4V absorption voltage, 13.9V float voltage.

After disconnecting the panels, I reconnected the battery, reconnected the panels and the battery voltage went up again to 16V+.

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