Is too much charge OK?

Hi HKB.
I have a CTEK D250S dual and the standard Nissan Patrol alternator.

Ok so you get 20A from the ctek, you need to look at the battery specs, if the battery can accept high charge rates then the additional charge from the solar controller might contribute some extra charge current when the battery is low, once the battery terminal voltage is forced to 14.4V the chargers will throttling back.

It will be upto the batteries charge acceptance as to weather its worth it, I had 200Ah of gel batteries at one stage and a 20A charger, I upped the charger to a 40A unit and it made no difference to the recharge times, the gels just wouldn't accept more than 20A.

One other thing to keep in mind also is how the chargers work, the ctek will pump 20A into the battery until it gets to 14.4V for example, it will then start reducing the charge current to keep the voltage at 14.4V until the charge current drops to less then .5A for example then go into float charge. If you have three chargers pumping current in they can confuse each other and they think the battery is fully charged so go into float mode early. This interaction can result in actually lengthen the time it takes to go from say 80% - 90% to fully charged.

So may be of value when the battery is low if the battery will accept high charge currents but could lengthen charge times at higher SOC's

Hi Lancie
I have a CTEK D250S dual and the standard Nissan Patrol alternator.

Racey. The battery is about 18mths old and 2 fridges would be running off it while we are driving along. It would also be being charged by the alternator and the 2 solar panels. So discharging and being recharged at the same time.

Deejay,

The two fridges running while you are driving will be using a portion of your Ctek's output, so your battery won't be getting the full output of the Ctek.

It is simple to improve your setup to get the max out of your Ctek.

You need a 5 pin (single pole double throw, or SPDT) automotive relay like this one.

Supply the coil from an IGN source in the car. Wire the normally closed contacts to power the fridges from the aux battery. Wire the normally open contacts to power the fridges from the vehicle's electrical system when the engine is running.

Here's how it looks on my setup. The red line is an IGN-controlled source. The Ranox DC-DC charger is like your Ctek.

Hi Deejay, if you are running 2 frigs , is one run as a freezer?

I generally agree with most of the comments from other contributors. A freezer unit would make the situation worse.

Cheers
Jon

Yes Racey, one fridge (30L) runs as a freezer while the other, a 60L Engel, runs as a fridge.

Thanks PK. My question would apply to a worse case scenario where we were camped in overcast conditions. I also wanted to know if there was a limit to how much charge could be put into a battery. I'm hoping the above never happens.
Thanks for your advice.

In overcast conds, you could have a panel on each battery and run a fridge off your main and other off your aux.
Panels will (should) put in ample to cover 2 fridges, even with one running as a freezer.
Well, at least in cloud for a few days it should keep your batteries up to decent levels, you might in rare circumstances have to turn the fridge off at night to keep things in check.
Of course just an hours driving a day would put a lot of power back into them too.

Sounds like measuring what's going out and what's coming in so you can avoid going below 50% SoC might be an idea.

I'm guessing with two fridges one is running as a freezer. During warmer parts of the year you might be drawing 100 Ah or more a day*. What are the panels putting back on an average day?

* http://12voltblog.com.au/how-much-power-does-12volt-stuff-use/

Sorry Sigmund, can't tell you what the panels put back into the battery.

I think you need another battery.

If you plan to do any camping of more than a day you don't have enough reserve power.

Going by what the website says ( Baintech ) the smart pass is a given. The charger will not recognise the solar while an alternator is running, it is either one or the other.

Having said that trying to run 2 fridges off a 105 ah battery is always going to be a uphill battle.

THats right, the 250 won't combine power sources, the smart pass will. It is a tricky bit of kit. With that sort of draw seconds count and having the panels being brought in and out seamlessly as they are required would make a difference.

Thank you for all that Swampy.