onechanet avatar image

SmartSolar 150/70 showing float when in absorption


I recently updated firmware of my SmartSolar 150/70-tr and now it's doing weird things. It goes into absorption for a few minutes and then jumps to float. However what is being reported and what it's doing are not the same. It's clearly still operating as if it's in absorption but showing float. The load when I took the screen shots was 150W.

Any help/instructions would ve very much appreciated. We live off-grid and depend entirely on our solar setup.

Many thanks,







mppt smart solarabsorptionfloat
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.

3 Answers
wkirby avatar image
wkirby answered ·

Why does the first screenshot show 13.78V from the SBS - as if a 12V system and the rest of your screenshots relate to a 48V system?
A battery Voltage of 55.79V seems a reasonable Float Voltage. What is your Float Voltage set to?
A short absorption time would be normal if you have the Absorption duration set to Adaptive.
If a 150W load, there is still 1.1KW going to the battery. This is possible if the battery Voltage dipped a little bit whilst in Float, but not low enough, for long enough to trigger a Re-bulk. What is your Re-bulk Voltage set to?

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.

I posted onto the main thread by mistake. I'm posting this in case you are not notified.



onechanet avatar image
onechanet answered ·

Hi @wkirby, thanks for your reply.

The reason I initially asked was because I've never seen this before in almost two years of using the Victron.

I have used the same settings on the controller since I installed it. The battery settings are those recommended by the manufacturer per 2V cell (screenshot of settings below)

As for the SPS, I only have it connected to the first battery for temperature monitoring/compensation.

Again, thanks so much for your help.



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.

The Voltage setting look fine to me. Those settings are for 25°C, bear that in mind.
The temperature compensation seems really off though. It's usually set around about -16mV/°C. I wouldn't imagine this being a great deal different from one battery brand to another. The colder it gets, the higher the battery Voltages will be. Maybe worth double checking this with your battery manufacturer?

I was under the impression that the SBS was communicating with the controller via venet and the compensation was automatic.

The compensation is automatic, but you have to throw it a bone.
It can only perform the automatic calculation based on the baseline information that you give it.
It can't automatically guess what the temperature compensation figure should be for your particular brand of battery, you need to provide this information in the same way as you set your Voltage limits.

  • Your float Voltage is set to 55.20V for 25°C
  • Your temperature compensation is set to -64.80mV/°C
  • The temperature is 16°C which is 9°C below 25°C (-9°C).

Armed with this information we can calculate the Voltage compensation ourselves and figure out if it is being automatically applied correctly.
Here is the mathematics:

(-64.8 x -9) = 583.2mV or 0.5832V compensation.
55.2 + 0.5832 = 55.783V which is pretty much what your float Voltage is reading in your screenshot earlier (55.79V).

So at 16°C your float Voltage is being automatically calculated correctly according to the compensation Voltage that you have given it.
If that compensation Voltage is wrong, which I suspect it is, then you'll need to find out what it should be. Consult the datasheet for your battery.

First, I just want to say thank you for your patience. :-)

The datasheet only mentions the capacity at certain temperatures.

If I have float set to 55.2V (25°C) then the capacity at 20°C is rated as 96% (52.992V). So, does this mean I have to compensate for 2.208V over a range of 5°C? If that's the case, then the numbers are huge!



No, that box is the capacity correction, not the charge Voltage compensation.
Thank you for attaching the battery datasheet. Unfortunately, it does not tell us the compensation Voltage, which is strange.

In that case, we should stick with the default value as it is -64.8mV/°C
This is usually -16.2mV/°C for a 12V battery, so 48V battery would be 4 times that.
I think I mentioned -16.2mV/°C earlier on, I was confused by the SBS readings in your very first screenshot relating to 12V.

Do you think that the 16°C is accurate? If so, then the compensated Voltage is correct - we calculated this earlier on based on the current compensation value.

It may be worth connecting your SBS over the whole battery bank so that it can convey an accurate Voltage of the whole bank rather than just the temperature.
Also, although it is a very light load, it is still a load on only a quarter of the series string and will cause an imbalance over time.


The 16°C is accurate. I'll follow your recommendation and connect the SBS over the whole bank.

As for the original question, I guess it must have been a firmware change. I was worried because the behaviour changed radically. I haven't yet noticed anything to suggest that the batteries have a problem.

Thanks for all you patience and help!



onechanet avatar image
onechanet answered ·

Oops, I forgot to upload yesterdays history.


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.