Solar Panel Voltage too high

[Crazy Pirate]

I have 2 solar panels in parallel each rated for 31.5 volts @ 9.45 amps. This panel pair goes into a Victron 100 volt 50 amp MPPT controller and then out to my 12v battery bank. I monitor this solar panel pair using the Victron connect bluetooth app. This has been working just fine until a few days ago. Nothing has changed but now this panel pair in full sun (no shading) is showing a higher battery voltage (14.45v) (actual battery voltage is 13.7v) and goes into float generating 1 or 2 watts of power.

I have a second pair setup identical to the first and under the same conditions and at the same time the second pair is generating 240w vs the first pair at 1w.

Can you or anyone point me in the right direction for a solution.

Thanks

Capt Dave

Reply

 

[Bud Martin]

'This has been working just fine until a few days ago. Nothing has changed but now this panel pair in full sun (no shading) is showing a higher battery voltage (14.45v) (actual battery voltage is 13.7v) and goes into float generating 1 or 2 watts of power.'

Do you mean the 'Battery Voltage' is too high?
So if you put DC Voltmeter at the battery terminals, it shows 13.70V, does it also show 13.70V at the Victron SCC battery terminals, and Victron interface shows 14.45V?

 

[Bobert]

My initial thought is that your battery bank is nearly full and one of the chargers has stopped charging

 

[MisterSandals]

My initial thought is that your battery bank is nearly full and one of the chargers has stopped charging

Pics of both SCCs app screens showing solar info, battery info and charge status would be REALLY helpful figuring this out.

 

[l00semarble]

My initial thought is that your battery bank is nearly full and one of the chargers has stopped charging

2nd

 

[Crazy Pirate]

This is for more clarification.

12v System / Lifepo4 300ah battery / Stbd Pair of Solar Panels (not producing like the port) / Port Pair of Solar Panels (producing normally).

The solar panels are the only charging source for the battery and the screenshots I've attached are for the same time frame, sun exposure, no shading etc. The solar panels are all identical. The port battery voltage (13.95) on the scc is verified per a multimeter measurement at the battery terminal.

Earlier in the charge cycle the Stbd panels showed a battery voltage of 13.90v and was charging at around 22a and the Port panels showed a battery voltage of 13.5v and was charging at around 20a but then as the voltage rises the Stbd panels gets to 14.45v and the charge current drops even though the mppt shows it is still in bulk charge mode. This does not happen on the port panels.

Hope this helps as I am very confused. Looking for any direction.

Thanks again,

Capt Dave

 

[Zwy]

It appears you are on a boat.

Even a slight difference in angle to the sun will affect the output of a panel. With a boat, I doubt you are keeping both panels equally pointed directly at the sun. The starboard battery is higher voltage and accepting fewer amps as it is closer to full charge. The problem you have is both batteries if paralleled are not equalized, this can be due to several factors.

With 2 batteries, these should have been ran to a common busbar if your are on a 12V system. Cable length will also affect charge/discharge to each battery. Having one battery with 5 feet of cable to a busbar and the other with 15 feet will affect the balance between the 2 batteries.

 

[Rocketman]

My guess is that the temperature compensation is somehow raising the voltage- what kind of batteries do you have - lead? Lithium?

Do you have a Victron shunt on the battery- with a temperature monitor?

 

[RCinFLA]

showing a higher battery voltage (14.45v) (actual battery voltage is 13.7v) and goes into float generating 1 or 2 watts of power.

Reply

Sounds like you have poor cable connection giving voltage drop between the charge controller and actual battery.

The extra voltage drop due to resistance will allow the charge controller voltage to rise to absorb voltage making it think full charge has been achieved, therefore the drop in output charging current.

Look for the warm/hot connection point.

 

[400bird]

Sounds like you have poor cable connection giving voltage drop between the charge controller and actual battery.

The extra voltage drop due to resistance will allow the charge controller voltage to rise making it think full charge has been achieved, therefore the drop in output charging current.

Yeah, I was going to post this.
OP, do you have fuses or breakers between the battery and charge controllers? I'd check those first, but the resistance and voltage drop could be anywhere.

 

[MisterSandals]

panels gets to 14.45v and the charge current drops even though the mppt shows it is still in bulk charge mode. This does not happen on the port panels.

Can you post screenshots of both SCCs charge/battery settings?

Are the 2 batteries connected together?

 

[sailingcal21]

One possible way to trouble shoot would be the swap SCCs to see if the issue follows the controller or stays related to the Stbd side. If the issue follows the controller that would indicate a failed controller (IMHO, not likely) or perhaps a configuration error as Mr.Sandals suggests.

Has the system ever worked?

It is definitely a curious issue, it will be interesting to know the solution.

 

[Crazy Pirate]

To all, I appreciate all the replies. Let me add some additional clarification.

This system has worked flawlessly for the last 2 years. There is a Victron shunt with temp comp feeding a BMV 702, each pair of solar panels are in parallel wired to an input breaker to its mppt then to an output breaker before connecting to a common positive bus bar and a common negative bus bar. I have a single 300ah lifepo4 (lithium iron phosphate) battery that is also connected to the same + and - bus bars.

So, when I stated the voltage levels on both the Port and Stbd panels it was the voltage being measured on the same battery. When the Stbd showed 14.45v on the only battery in the system the Port showed 13.95v on the same battery. When I measured at the battery terminal my reading was 13.95.

I think a poor cable connection is probably the culprit. I will go through and measure the voltage at each connection point while correcting any connection issues. If this fails, I will swap the mppt controllers and hopefully find the solution.

I will report back any findings.

Thanks again,

Capt Dave

 

[RCinFLA]

To all, I appreciate all the replies. Let me add some additional clarification.

This system has worked flawlessly for the last 2 years. There is a Victron shunt with temp comp feeding a BMV 702, each pair of solar panels are in parallel wired to an input breaker to its mppt then to an output breaker before connecting to a common positive bus bar and a common negative bus bar. I have a single 300ah lifepo4 (lithium iron phosphate) battery that is also connected to the same + and - bus bars.

So, when I stated the voltage levels on both the Port and Stbd panels it was the voltage being measured on the same battery. When the Stbd showed 14.45v on the only battery in the system the Port showed 13.95v on the same battery. When I measured at the battery terminal my reading was 13.95.

I think a poor cable connection is probably the culprit. I will go through and measure the voltage at each connection point while correcting any connection issues. If this fails, I will swap the mppt controllers and hopefully find the solution.

I will report back any findings.

Thanks again,

Capt Dave

Make sure you run the battery down first so you get large charge current to battery. It will make finding bad connections easier. You need current to see voltage drop across poor connection.