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The wee solar panel

7/04/2018

The solar panel is only a 10W item and mounted under the skylight.  It seems to work as predicted, even better really.  After a day of sunlight the leisure battery was showing 15.6V.  This is what the CTEK battery charger information calls "A reconditioning charge"  There cannot be much current from a 10W cell - maybe 3/4 of an amp - less than the C100 charge for a 90AH battery but a little bubbling will be happening which apparently is good to prevent stratification in the battery.

But I think I can do better.  I am changing the unit to allow the panel to charge both the vehicle battery AND the leisure battery.  They are both new batteries and are both flooded lead acid.

The leisure battery, when the van is parked, supplies zero current.  The vehicle battery supplies the circuitry for the remote locking receiver, the burglar alarm, and the radio memory.  It's not much, around 50mA.  That is about 1.2AH per day.  The panel should easily provide that even in winter.

When the power is split using diodes, it's the lowest voltage battery which will take the current until it's voltage appoaches the same as the other one.

For anyone interested, the final circuit is here.

A few days after fitting the new arrangement, 10am, Weather a lttle cloudy.
The leisure battery is sitting at 12.9V taking and supplying zero current.  It is fully charged.

The starter battery is at 12.7V and taking 0.3A from the solar panel.  This will be replacing the power from the steady drain from last night. (radio, remote doorlocking etc). As the voltage increases to 12.9V the current will split and both batteries will be getting topped up.

Will this conversion to a solar make me change to a roof covered in panels? Absolutely Not. I stand by all of my original comments in Power use management.

Now, next post in another four years maybe?

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