Solar controllers and batteries connection

Hi glandvador,

Good to hear from the other side of the world!

This must be a big solar array. I doubt that there is any reason not to leave all batteries in parallel, though there might be some advantage in connecting as you suggest, two parallel pairs, each pair connected to the load through its own controller. That way, if one battery got tired it wouldn't affect the other pair.

The only disadvantage I can see to the present arrangement is that there might be some undesirable interaction between the controllers when they are lightly loaded, ie when the batteries are fully charged.

Think I'd be asking the manufacturer for a definitive answer.

Cheers

John

glandvador,

the stecas are common positive regulators.
This means there's a permanent connection between battery positive and load positive.
And while the battery's sitting above the low voltage cutoff, the electronic switches which are in the negative leg between the load and the battery are closed.
So it doesn't matter which way you make a parallel connection. It can be done on the battery side, or on the load side.

But there's more to it:

in case one of the four batteries develops a fault (shorting out of a cell), this battery then discharges the other battery which is directly wired in parallel.
But it'll also discharge the other two batteries if they were all wired in parallel.

On the other hand, if the two battery pairs are wired in parallel via the load terminals, then this would effectively prevent the 'good' pair from being drained to the same voltage of around 11.4V. Instead, it'll only be drained to 11.8V.
That's because the voltage differential between the good and bad pairs is reduced by the forward voltage drop of the drain-source diode which is an integral part of the electronic switch (power MOSFET). Sorry if I've confused you with techno speak.

To sum it up.
This can be done either way, but connecting via the load terminals has a small advantage which becomes relevant if one battery develops a fault.

grüezi

Thanks,

Yes, it is a pretty big array. It's needed on bad days :)

For the light loaded controllers, I think this is pretty much what he observes,
one shows 13.8V and the other 14.X. When charging batteries, they both show the same values.

I will motivate him to change the connections on batteries. Some fun in perspective :)

Best regards,
Glandvador.