question

novice avatar image
novice asked

Bluesolar 75/15 voltage too high

EDIT: No longer on mobile, adjusting....


Hello,

My tech (father) just called from a remote site and said the measured voltage is at 16.6v at the battery terminals, I haven’t been out to the site to see what’s going on.


Setup:

-Bluesolar 75/15 MPPT charge controller

-Single 38v pmax 345w mono solar panel

-2x 104ah 12v sla batteries wired in parallel


All default settings on the controller, ve.direct jumper in it's factory default place


Some quick searches leads me to believe it's “auto detecting" a 24v battery and is trying to charge at a higher voltage? I would think I'd be seeing closer to 24v though.

I wonder how long my batteries been cooking.....and I wonder if my 11 other sites are doing this :(

MPPT Controllers
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novice avatar image novice commented ·

I just confirmed via VictronConnect that the system thought it was a 24v system.


It updated the firmware from 1.15 to 1.59 and after the update it still remained thinking it was a 24v system. I have set it to 12v manually.


This was a factory default install.


I assume Victron would like some logs or additional info? These were well on their way to cooking my batteries with permanent damage.

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3 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hello Novice,

This issue relates to the auto sense behaviour of the MPPTs that was changed in firmware version v1.26.

The Automatic battery voltage detection was improved. In the old situation it remained active; even after initial commissioning. Which in rare occassions could lead to overcharging. In the new situation (after 1.26); it will detect and stored the battery voltage (12, 24, 48V) only once.


At powerup: when not configured yet; the charger checks battery voltage. If the battery voltage is present (>7V), then the detected battery voltage is stored and further automatic detection is disabled. If the battery voltage is absent (<7V) the unit operates as a 12V model. At next powerup it will retry the sequence.


In practice this means that when connecting the battery first after taking it out of the box; all works well immediately; and will never accidentally change later. When connecting PV first; it operates at 12V as long as its powered. Then connecting a 24 or 48V battery will make it switch off in an error. To recover from that; disconnect all wires and connect battery first.

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novice avatar image novice commented ·

Thank you for the clarification.

This does not explain what happened with my firmware (1.15) but we may never know!

Just to clarify, with updated firmware (>= 1.26) when a unit is completely disconnected from PV and battery, it will always auto detect the battery voltage when hooked up according to the directions (when it hasn't been set to a fixed voltage via external configuration) which is battery first, then PV.

Thank you!

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wkirby avatar image
wkirby answered ·

That's not good.
The Voltage autodetect should have worked, but it is possible to set it manually too.
So it's either the wrong system battery Voltage set or the absorb voltage is set too high, it can be set to just over 17V from memory (useful for certain chemistry / cell configurations).

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novice avatar image novice commented ·

I’ve ordered the Bluetooth dongle to set it to 12v manually. There’s several posts on here people have mentioned a similar issue, and they bought the usb cable for pc or bt dongle and the controller was in 24v mode when they checked.


I just cold booted a few minutes ago and will be adding some monitoring tomorrow.

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

I previously wrote some information here about the behaviour of the auto detection.

This was based on my own observations and conclusions - but I have since been corrected by Victron R&D on the precise behaviour, so I have removed it to prevent confusion.

Unfortunately this site doesn't allow me to strike through, so I thought it better just to delete it.


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novice avatar image novice commented ·

I can confirm it was setup with the battery connected first during the initial install.


I do know during a site wire cleanup, the battery fuse was blown at one point which would have resulted in a short seen on the battery connection to the mppt and thus panels connected and no battery connection.


I know before this from previous spot checking the charge voltages were in spec for a 12v setup and that the 16+v was only noticed after that incident.


I assume the auto voltage check is done at every power up?

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ novice commented ·

Re-sensing depends on the age and firmware of the unit.

All current models only do a single initial check to set voltage and then will not do any further auto-sensing (for this reason).

That has been the case for over a year from my memory, perhaps longer.

We are now looking into ways to improve this system even further.

With more Bluetooth units than ever before, it is becoming easier to do the necessary programming than it once was.

I haven’t heard of another case of the a unit changing voltage settings. But that is also very serious and will be on the lookout for other reports.

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