Quick question about dual batteries

Sorry to say I dont agree with manual switches ..you just forget to operate them and its all a waste of time...what you need is a VSR ..voltage sensitive relay .....when battery volts reaches 13.6 it connects in the extra battery and disconnects it when main battery volts falls...I dont know how reliable the post in in Eygpt ..bad I suppose but lots on e bay ..used for caravans and 4x4 of which (4x4) that is you have a lot in egypt...

 

So if enough drivers forget to release the handbrake we reward stupidity by installing automatic ones? Citroen has done just that: if the battery is dead there is no way to move the car!

I once made a motorized switch for a guy who wanted state of art circuitry in his sailing yacht. A VDR isn't enough, when starting you want both batteries connected and during starting there should be no switching so as not to fuse the relay contacts.
The solution I came up with used a microprocessor and the stepper motor from a 5.25" floppy drive to move a solid copper wedge between two contact springs that could carry 300 Amps. Because the micro was over-qualified for the job I added a display to inform the owner about the battery status.
In my own boat I use a 4-way Vetus switch and never forgot to operate it in the past 25 years.

 

I am a bit old school. I still have my old wave runner jet ski 2 stroke engines and although its an old model, its simplicity and ease of repair for me outweighs and new overpowered computer / electrical controlled models.

So yah switch sounds like the choice i would take, specially the boat is a 5.5 meter cuddy cabin.

 

usually you have one battery for starting and one for the accessories joined by a VSR ...then if your start battery fails you switch in the other battery with a big two pole switch and off you go hopefully....everyone to his own

 

i dont know what you mean by a VSR

 

I like the VSR for a small boat. If you are out messing about stopping and going you will end up turning the switch a lot so you don't kill your cranking battery running house loads such as refrigerator and nice stereo system. If you just want to have a battery ready to go when you get aboard or don't have significant house loads then the manual switch is fine.

 

think I already explained it ...Voltage Sensitive Relay ...used in caravans boats and 4x4.....joins the batteries when the starter battery gets to 13.6 and disconnects when it goes lower...three wires ..earth . bat 1 pos and bat 2 pos....photo of one attached but its an expensive marine version ..check at your caravan RV shop ...you dont need 125 A as the max charge current you will get to your second battery is about 25 A

 

Then you said VSR, thought it was a different thing just a typo then

 

Yep they do just as they say on the packet
and they are fool proof

 

Told an operator I was training on a piece of equipment that it was "fool proof". She then looked me right in the eye and told me she wasn't a fool she was an idiot. Turns out the equipment was pretty much "idiot proof" too