Help understanding my new solar set up

[Crisby]

I am struggling to get my head around our solar charging, previously we had 2 x 90w panels feeding 3 x 110 ah agm domestic batteries but last year the batteries were replaced with 3 x 115 ah agm as the old ones were 12 years old and not too good any more. We then replaced the panels with 2 x 175w panels but kept the same pwm controller as it was rated to 25 amps. Over the winter one panel was disconnected and the batteries were 100% capacity on return in March.

2 weeks ago I fitted a new Victron MPPT controller and via Bluetooth and the app on my phone I can see how it is charging but the battery capacity never gets past approximately 80% and is in float mode from about 76% despite there being another 3-4 hours of daylight left and the voltage is around 14 on the panel.

My confusion is why does the controller not take the batteries to nearer 100%, is it to preserve battery life and which is more important as an indicator of battery strength, volts or battery capacity?

Any help will be gratefully received!

Chris

ps, if it is relevant we are in the med and when plugged in to shore powere the batteries do come up to 100%

 

[Baggywrinkle]

I am struggling to get my head around our solar charging, previously we had 2 x 90w panels feeding 3 x 110 ah agm domestic batteries but last year the batteries were replaced with 3 x 115 ah agm as the old ones were 12 years old and not too good any more. We then replaced the panels with 2 x 175w panels but kept the same pwm controller as it was rated to 25 amps. Over the winter one panel was disconnected and the batteries were 100% capacity on return in March.

2 weeks ago I fitted a new Victron MPPT controller and via Bluetooth and the app on my phone I can see how it is charging but the battery capacity never gets past approximately 80% and is in float mode from about 76% despite there being another 3-4 hours of daylight left and the voltage is around 14 on the panel.

My confusion is why does the controller not take the batteries to nearer 100%, is it to preserve battery life and which is more important as an indicator of battery strength, volts or battery capacity?

Any help will be gratefully received!

Chris

ps, if it is relevant we are in the med and when plugged in to shore powere the batteries do come up to 100%

Where are you getting the info on charge level? Do you have a BMT? All the BMT does is count current in and current out .... it needs to be told when the batteries are full and it will adapt from there.

The Victron MPPT will register that the batteries are full due to the amount of current they take and will move from bulk to absorb and then float dependent on the battery demand and the charging profile set.

... they are basically independent from each other using different mechanisms to determine if the batteries are full.

 

[Crisby]

Where are you getting the info on charge level? Do you have a BMT? All the BMT does is count current in and current out .... it needs to be told when the batteries are full and it will adapt from there.

The Victron MPPT will register that the batteries are full due to the amount of current they take and will move from bulk to absorb and then float dependent on the battery demand and the charging profile set.

... they are basically independent from each other using different mechanisms to determine if the batteries are full.

We have a Mastervolt Mass Inverter Charger Control panel which was installed with the Mastervolt Inverter/charger by the previous owner and that is where I am reading ‘Battery Status’ and ‘Volt-Amp’. The Volt-Amp page generally agrees with the MPPT status on the Victron app, we always have plenty of volts but never seem to go above 80% or so on the battery status unless we leave everything off for a few days or so and then it creeps back up. When plugged into shore power the batteries come up to 100% overnight.
This morning with good sun on the panels I am looking at 13.8v with 10 amps of charge and a battery status of 63% at 10 am.

Chris

 

[roaringgirl]

Your Mastervolt Mass Inverter Charger Control panel needs to be recalibrated, it is not telling you the truth. Do you have a shunt?

 

[Sandy]

Have you programmed the in the correct Ah for the new battery bank?

 

[simonfraser]

Which ‘controller’ is showing 80%

 

[Crisby]

Your Mastervolt Mass Inverter Charger Control panel needs to be recalibrated, it is not telling you the truth. Do you have a shunt?

Not sure if we have a shunt, don’t think so but all installed by a previous owner so I will have to check

Chris

 

[Crisby]

Have you programmed the in the correct Ah for the new battery bank?

No but it was only 30 ah difference to the previous one

 

[Crisby]

Which ‘controller’ is showing 80%

The Mastervolt battery monitor, which also seems to monitor charge when on shore power and battery discharge/voltage which tends to agree with the voltmeter on the switch panel

Chris

 

[noelex]

What battery settings are you using on the MPPT controlle?

 

[roaringgirl]

If there isn't a correctly wired shunt, feeding both data sources; it's hardly surprising that they don't agree.

 

[Sandy]

No but it was only 30 ah difference to the previous one

From years of testing stuff - if your don't set up and calibrate your instrumentation correctly it will never give your accurate results.

 

[Crisby]

What battery settings are you using on the MPPT controlle?

Rotary switch posn 2 which includes AGM batteries which we have

Chris

 

[Crisby]

If there isn't a correctly wired shunt, feeding both data sources; it's hardly surprising that they don't agree.

I’m not necessarily interested in them agreeing, I just want to know which one is more important, battery status or volts. Does it matter if my battery status is not 100%?
How would I calibrate a battery monitor for a system over 10 years old with no instruction manual on board ? For batteries within 10% capacity of the previously installed batteries. If I can I will.

Chris

 

[roaringgirl]

I’m not necessarily interested in them agreeing, I just want to know which one is more important, battery status or volts. Does it matter if my battery status is not 100%?
How would I calibrate a battery monitor for a system over 10 years old with no instruction manual on board ? For batteries within 10% capacity of the previously installed batteries. If I can I will.

Chris

Go with the (no charge, no load) voltage. If you have no shunt then the monitor is using voltage to estimate the capacity reading anyway.

 

[noelex]

Rotary switch posn 2 which includes AGM batteries which we have

Chris

Thanks for the reply.

I am not familiar with any Victron MPPT controllers with a rotary switch. Which model do you have? Sometimes the default values can undercharge, which may explain your problems.

 

[Crisby]

Thanks for the reply.

I am not familiar with any Victron MPPT controllers with a rotary switch. Which model do you have? Sometimes the default values can undercharge, which may explain your problems.

We have Victron smartsaolar 100/50 and I must admit I have suspected the default setting being part of the problem

Chris

 

[Buck Turgidson]

your master volt is probably confused by the float voltage 13.8. I'll bet the 10A you see as charge is actually 10A being used by your boat. Switch everything off and look at the "charge" current. Ill be it's milliamps.

 

[Buck Turgidson]

Thanks for the reply.

I am not familiar with any Victron MPPT controllers with a rotary switch. Which model do you have? Sometimes the default values can undercharge, which may explain your problems.

it's 14.4v charge. 13.8 float.

 

[noelex]

I have downloaded the Victron manual for the 100/50. The rotary switch bypasses the settings available on the Victron app.

The rotary switch has a very conservative charge setting, which may be causing your undercharging.

What brand of batteries do you have? I can suggest some new settings using the app, which may fix the problem. If not, at least you know the problem lies elsewhere.