# Victron smart 75/15 solar controller (1 Viewer)

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#### Top Hat

##### Free Member
I have recently installed the above MPPT controller and down loaded the Victron app. Looks a great bit of kit.
One part of the read out I'm not sure of is the Solar reading shows the ampage being produced, then the battery read out shows ampage at the battery which is always higher, am I correct this higher reading is the improvment the controller has made to charging.

Charlie

Last edited:

#### autorouter

The controller knows the best voltage and current to get the maximum power out of the solar panel depending on the brightness of the sunshine. It transforms that power into the best voltage and current for the battery, depending on its state of charge.

Looking at the numbers, the solar panel power is panel volts x panel amps. The battery charging power is battery volts x battery amps. You will find that the powers are about equal. The panel will probably have a higher voltage but a lower current (amps) than the battery.

OP
OP

#### Top Hat

##### Free Member
As a example today the sky was partly over cast with the sun very low this time of year, the victron app was registering Solar 9 watts 24 volts 0.4 amps and the battery 12.64 volts 0.7 amps.
With my limited knowledge I am trying to understand what I'm seeing.

Charlie

#### DBK

LIFE MEMBER
As a example today the sky was partly over cast with the sun very low this time of year, the victron app was registering Solar 9 watts 24 volts 0.4 amps and the battery 12.64 volts 0.7 amps.
With my limited knowledge I am trying to understand what I'm seeing.

Charlie
It's the wattage readings for each side which are more less equal, less a few percent for losses. So if the panel is generating 9W then it is no surprise about the same power (12.64 * 0.7) is going into the batteries.

The solar panels behave slightly oddly in that they will produce almost a constant current irrespective of voltage up to say around 18 volts after which the current drops very rapidly so that it will be zero by around say 22 volts. This means maximum power is generated somewhere around 18 volts and the controller reduces this to say 13 volts but with a corresponding increase in current. Power in always equals power out less a few losses.

In your case the controller has reduced the charge by letting the panel voltage increase to 24 as it must think the batteries are fully charged. I'm not completely convinced of this as the float voltage should be over 13 volts. It is possible your leisure battery is on the way out. Do you know how old it is?

OP
OP

#### Top Hat

##### Free Member
Battery as far as I know is no more than 12 months old, a few months back I was off ehu for 5 sunny days with a elec only fridge and it never dropped be low 12.7 at rest, so fingers crossed it's ok.
What caught my attenstion yesterday was that the voltage was reading 12.64v when it is usually over 13v, and found I had left a inverter switched on, so have charged the battery on ehu.
Today the readings are solar 8w 22v 0.3a battery 13.26v 0.6amps
Now I know a little more what the controller is telling me I will keep a eye on the battery.
Thanks
Charlie

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