MPPT Charge controller problem?

[vagabondvanman]

Hi,

Ive got a 180W solar panel in my van connected to a MPPT Tracer with MT5 and 115AH battery.

I noticed that when the sun comes out the reading goes up to 100% full in a couple of minutes and then when some cloud comes over it goes back down to 50-60% very rapidly. Any ideas whats happening here??

Thanks

[Sunking]

What makes you think anything is wrong? Solar panels do not work with out direct sun light.

[vagabondvanman]

Because why would it reach 100% battery charge within a couple of minutes and then suddenly drop to about 50 % straight away?

[Sunking]

Would indicate your battery is not charged up yet or poor connections.

[vagabondvanman]

But surely that doesn't account for why it reaches 100% charge very quickly when a tiny bit of sun comes out.

[sensij]

Are you sure you set it up right? Correct battery capacity, temperature compensation, and type? Have you tried disconnecting all loads from the battery (besides the charge controller) so there is nothing that could drain it?

A bad connection, as Sunking suggested, could cause the charge controller to get a bad voltage reading and misreport the SOC, especially when there is current flowing (when the sun is out).

[thastinger]

Hi,

Any ideas whats happening here??

Thanks

Yes, the voltage is going up and down.

[vagabondvanman]

Capacity/ and type are correct. I left temp comp. as default.

I will disconnect everything tomorrow and see. How can I check/fix a bad connection if this is the problem? Thanks

Are you sure you set it up right? Correct battery capacity, temperature compensation, and type? Have you tried disconnecting all loads from the battery (besides the charge controller) so there is nothing that could drain it?

A bad connection, as Sunking suggested, could cause the charge controller to get a bad voltage reading and misreport the SOC, especially when there is current flowing (when the sun is out).

[Wy_White_Wolf]

Hi,

Ive got a 180W solar panel in my van connected to a MPPT Tracer with MT5 and 115AH battery.

I noticed that when the sun comes out the reading goes up to 100% full in a couple of minutes and then when some cloud comes over it goes back down to 50-60% very rapidly. Any ideas whats happening here??

Thanks

Doesn't that controller have just a single led that flashes when it's charged and solid green when charging? If so how do know the battery is dropping to 50-60% when a cloud goes over?

Sounds to me like everything is actually working just as it should. Your battery is already charged. When the sun comes out the panel can put out full power and the flashing light is caused by the shunt controller kicking off when maximum voltage hits and turning back on after a few tenths of surface charge drops off or load drops the voltage. When a cloud goes over the panel cannot support full voltage that would make the shunt controller kick off so it stays on just providing a trickle charge or the load drops the voltage.

One of the problems with meters like the MT-5 is they have to read battery voltage under charging and load conditions. But that is a bad indicator of true SOC conditions.

WWW

[sensij]

Doesn't that controller have just a single led that flashes when it's charged and solid green when charging? If so how do know the battery is dropping to 50-60% when a cloud goes over?

Sounds to me like everything is actually working just as it should. Your battery is already charged. When the sun comes out the panel can put out full power and the flashing light is caused by the shunt controller kicking off when maximum voltage hits and turning back on after a few tenths of surface charge drops off. When a cloud goes over the panel cannot support full voltage that would make the shunt controller kick off so it stays on just providing a trickle charge.

WWW

The MT5 meter reports SOC as a %, based on voltage feedback. I am assuming that is what the OP is reporting.

[Wy_White_Wolf]

The MT5 meter reports SOC as a %, based on voltage feedback. I am assuming that is what the OP is reporting.

Yes, so when a cloud goes over it changes from reading voltage under charge conditions to reading voltage under load conditions. We all already know that voltage is a poor measurement for SOC and is only remotely accurate if the batteries have been at rest for a couple hours.

WWW

[vagabondvanman]

Yeah thats correct.

The MT5 meter reports SOC as a %, based on voltage feedback. I am assuming that is what the OP is reporting.

[Mike90250]

Because why would it reach 100% battery charge within a couple of minutes and then suddenly drop to about 50 % straight away?

I would suspect that the batteries are old, or possibly sulphated. Time for new ones ? Get some more opinions before you spend any $$

What are your loads? what are the batteries ?

[vagabondvanman]

Battery is only about 4 months old....

[sensij]

Yes, so when a cloud goes over it changes from reading voltage under charge conditions to reading voltage under load conditions. We all already know that voltage is a poor measurement for SOC and is only remotely accurate if the batteries have been at rest for a couple hours.

WWW

Agreed. Taking the loads off the system and watching it over some time should give a better idea of what is going on, even if the measuring technique is still not great.