Power in my camper trailer ...

[Prime]

Hi WobblingFree,

You raise an interesting point. I have wondered about the internal resistances of batteries and until now, no one seems to have been concerned about it (or known about it?) ...

Time for a bit more research!

Thanks for your input!

Luke

[Prime]

Sorry, that should have been WomblingFree ... lol ... sorry ...

Yep, just gone back to basic DC theory, and you're right, the battery with least internal resistance will get more power.

I guess the next question though is to determine if smart chargers "see" the individual differences or if they look at the averages.

Mathematically, even if you have batteries of exactly the same internal resistance (say three of them), the net internal resistance will be roughly a third of the individuals ... if they are slightly different, the internal reistance will still be less than the one with the smallest internal resistance ... hmmm ...

Not sure this helps in determining how a smart charger will behave ... hmmm ????

Luke

[robcaz]

This is a good article http://www.smartgauge.co.uk/batt_con.html

I have spoken to Jamie Hazelden about charging two batteries that are connected in parallel ie +to+ & -to-. He said the most common cause of the second battery failure was when the charger was only going to one battery.

I have also spoken to Collyn Rivers & he said that connecting the charger to the first battery is ok.

In the above link it says..... Finally, if you only have 2 batteries, then simply linking them together and taking the main feeds from diagonally opposite corners cannot be improved upon.....

..... And finally, we keep getting asked where the chargers should be connected to. We didn't address this question because it seemed so blatantly obvious where they should be connected that it never occurred to us that anyone might be unsure. The chargers should always be connected to the same points as the loads. Without exception.....

[vincent]

Good tread so far, but why on earth do you want three batteries.It will not solve the fundamental problem, balance input against output.If you use more than you put in you end up with flat batteries.Secondly you have to learn to live with solar and
adjust your usage accordingly.If you want to do i.e. a lot of work on your laptop ( photo editing ) do it when the sun shines.
Charging twelve volt devices, on the run while your driving.Turn the fridge to its lowest temp during the day and ease of during the night. And have sufficient solarpanel capacity to serve your needs, keep in mind that the solaroutput is greatly reduced when it is overcast.Two batteries of 100 to 120AH are more than sufficient to serve your needs.Check my introduction, I have used this system over six years, the cable still sits coiled up on the drawbar never needed it.Never had to top up on a 240V supply.Fridge runs 24/7.In my case I used cristalline panels because they give more power for a given area than amorphous. both panels work fine. I needed to extract the maximum out of a small roof area, total 265W.My only regret is that the multi-input chargers were not available when I built the system.The first system I build was on a remote property I owned.24V system, 12x1400Ah batteries in the mid nineties, finally the batteries are shot. not a bad run for standard batteries.It shows that when you take care they can last a long time.And yes I have a folding panel 160W just in case.
Good luck, use correctly sized wire do not skimp on that and fuse your main cables on the battery terminal. Very often overlooked.