Battery connection

Thanks Ross,
As the batteries are different values (75ah & 100ah) I was merely wondering If parralel connection was more OR less beneficial to full charging as connecting both batteries to the same point at the regulator would be.
In essence i would treat the regulator like a double adaptor..
Would it make a difference to;
A) charging the batteries
And/Or
B) discharging the batteries if one gets the fridge load and the other lights and coffee maker?
I hope I explained it better this time
Marcel

I use the vehicle battery to charge a 105ahAGM in the rear of my ute and that is also connected to a 120ahAGM in a camper.
Solar feeds a PWM regulator and the engine is the source of amps while driving and when stopped the solar (connected all the time) charges the batteries. No trouble but does have good sized cables to minimize VD.

If you are going to drag BIG amps (I read your post about a coffee maker) the cables between the two batteries would have to be a fair size.
I wouldn't be running a coffee maker, Microwave oven or do the ironing either.

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It really does not make a lot of difference having two batteries of different capacity in parallel. Consider the large number of dual battery systems with a flooded lead-acid cranker and a differently sized AGM auxiliary which are in parallel on the alternator when the charging isolator is closed. Each battery will absorb current based on its state of charge (voltage) and its internal resistance and ultimately both will charge to the same terminal voltage. Being of differing chemistry is however not ideal for charging.


Much the same with two auxiliary batteries permanently wired in parallel. And they will contribute energy to the load proportional to their internal resistance. It is appropriate for them to be of the same chemistry however to achieve proper charge.

Thanks Allan,
When you say 'add a fuse on the +', I'm a bit stuck. I'm running a 6mm2 cable but can not find a fuse holder that I can add inline....???
I understand the need/precaution, but....
Marcel

get something like this. Cut the loop near the screw cap bit of the holder and splice it to the cable to the regulator (joining crimp splice will do.) Crimp an eye terminal to wire to the long bit of the holder and terminate on the battery positive. That will get the fuse close to the battery. No need for a fuse at the regulator end, the regulator will not supply enough current to cause problems.

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Marcel, here are some suitable fuses, and Sidewinder is a Business Member on ExplorOz. Similar products can be found at auto accessory shops, BCF and the like.


Personally I prefer the 40A or 60A 'circuit breakers/trip switch' that you will find further down the referenced page. They have electrical advantages over fuses and also are easier to install as the cable is inserted and secured by a grubscrew whereas the fuse has a tail which has to be joined to the cable which can be difficult if you do not have the appropriate equipment. Keep the wire from the breaker to the battery +ve short and unlikely to contact earth. Take the load cables from the side of the fuse or breaker furthermost from the battery and these will also be protected by the fuse/breaker.


Be sure to open both fuses or breakers if disconnecting a battery as otherwise the removed cable will be 'live' from the other battery.