Battery help please.

[Sue26]

Hi. We have a swift 696 with original sargent electrical systems fitted and what we believe to be a 60w roof fitted solar panel. When we go off grid we also use a portable solar panel which has so far all been adequate for our off grid usage.
I recently bought a couple of bm6 battery monitors to try and help me monitor/understand whats going on with the batteries. Whilst in storage and with the psu turned off and without ehu, the readings from the leisure battery are as I would expect. Theres no solar going into it and over 3 weeks, the soc has dropped a little.
The vehicle battery on the other hand has me totally confused. During the day, it fluctuates depending on the conditions/sun but on some days during the night when no solar available it seems to spike for no (to me) apparent reading.
I've attached screenshots from 2 different time periods if anybody can help me understand what might be going on with my vehicle battery I would be grateful for your observations.

 

[Sue26]

Bumped my message in the hope of a response...

 

[autorouter]

Is the 60W solar panel on the roof connected to the Sargent box? What model is the Sargent box? It looks to me like something is producing 'equalisation' pulses, of about 15V.

Equalisation is a process that some battery chargers apply to flooded lead-acid batteries, to stir up the liquid electrolyte, and equalise the voltages of the 6 individual cells in the battery. It is normally only applied every few weeks, and shouldn't be happening all the time.

Stirring the electrolyte is not really necessary in a vehicle, the normal vibration and movement are enough to stop the electrolyte stratifying. It is more necessary in house systems, where the batteries don't ever move.

 

[Sue26]

Autorouter
Thank you for your reply.

The solar goes into a pwm controller and from there it goes to which ever battery needs it at the time. With the psu turned off all solar should be directed to the vehicle battery. We have the px300 charger which I thought only worked when on ehu and the psu is in the ec400 range.
Is what appears to be happening within the vehicle battery dangerous or should I just keep an eye on it?
Sue

 

[autorouter]

It might not be equalisation, I didn't know the solar controller was a PWM type. Is the solar PWM controller separate, or built into the Sargent box? If it's separate, what make/model is it?

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[Sue26]

It might not be equalisation, I didn't know the solar controller was a PWM type. Is the solar PWM controller separate, or built into the Sargent box? If it's separate, what make/model is it?

Hi
It's mounted in a cupboard under the the solar panel. It must 'talk' to the psu to switch between leisure and vehicle batteries but I've no idea how this happens. When the psu Is off all available solar goes into the vehicle battery.

Sue

 

[Sue26]

It might not be equalisation, I didn't know the solar controller was a PWM type. Is the solar PWM controller separate, or built into the Sargent box? If it's separate, what make/model is it?

I forgot to add, the controller is a sargent 15778

 

[autorouter]

On second thoughts, maybe these high voltage pulses are an artifact resulting from the way the battery monitor works, so nothing to worry about really.

A solar controller reduces the voltage of the solar panel (maybe 18V to 28V) to something suitable for charging the batteries. A Pulse Width Modulation (PWM) solar controller does this by rapidly switching the panel voltage on and off.

If for example the panel voltage is 28V, and the required battery voltage is 14V, then it switches the voltage on and off so that it is on for 50% of the time, and off for 50% of the time. So on average the voltage will be about 50% of 28V, ie 14V.

As the panel voltage falls, it is switched on for a greater percentage of the time.

The battery monitor probably samples the voltage at high speed, rather than taking a continuous reading. So sometimes it samples the high panel voltage, and sometimes the battery voltage (when the panel is 'off'). That might result in the spiky trace that you are seeing. If so, it's just showing the PWM controller doing its job.

 

[Sue26]

On second thoughts, maybe these high voltage pulses are an artifact resulting from the way the battery monitor works, so nothing to worry about really.

A solar controller reduces the voltage of the solar panel (maybe 18V to 28V) to something suitable for charging the batteries. A Pulse Width Modulation (PWM) solar controller does this by rapidly switching the panel voltage on and off.

If for example the panel voltage is 28V, and the required battery voltage is 14V, then it switches the voltage on and off so that it is on for 50% of the time, and off for 50% of the time. So on average the voltage will be about 50% of 28V, ie 14V.

As the panel voltage falls, it is switched on for a greater percentage of the time.

The battery monitor probably samples the voltage at high speed, rather than taking a continuous reading. So sometimes it samples the high panel voltage, and sometimes the battery voltage (when the panel is 'off'). That might result in the spiky trace that you are seeing. If so, it's just showing the PWM controller doing its job.

Ah ok, I think I understand.
I just presumed that during the night when no sun/daylight then it wouldn't be doing anything.
I feel reassured that it's nothing to be concerned about.

Thank you for your help with this.
Regards
Sue