Dual battery wires and fixtures/

[iceman]

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=160351381254&ssPageName=STRK:MEWNX:IT

i bought the above and have been reading around about Dual batteries and read somewhere that to have the wrong size cable small/thick will not be good for the system, can anyone recommended the right size please.

 

[jims-terrano]

As long as your system is fused correctly it should not be dangerous. The smaller the wire the more resistance so the less charge the second battery will receive, so the thicker the wire the more charge it will get so it will be quicker to charge. Think about normal caravan wiring from car to van, that is only thin wire so the split charge is negligible but the length of run also plays a part too.

When we had a local Lucas branch in our area their techies used to recommend "72 strand", this is quite thick and has served me well but wouldn't be suitable for a winch or starting.


Jim T

 

[iceman]

jim can you confirm that i would 72 strand be ok for me then.

is that your dog in the avatar and also is it choc lab, i have a 5 month old choc lab and a fantastic pet to have.

 

[Terranosaurus]

How big do you want?

72 strand isn't a usual auto spec.

Standard Cable specs
14/0.30mm, 1mm2, 8.75amp.
28/0.30mm, 2mm2, 17.5amp.
44/0.30mm, 3mm2, 27.5amp.
65/0.30mm, 4.5mm2, 35amp.
84/0.30mm, 6mm2, 42amp.
97/0.30mm, 7mm2, 50amp.

Thinwall Cable
16/0.20mm, 0.5mm2, 11amp.
32/0.20mm, 1mm2, 16.5amp.
28/0.30mm, 2mm2, 25amp.
44/0.30mm, 3mm2, 33amp.
84/0.30mm, 6mm2, 50amp.

 

[jims-terrano]

I really can't say what is a standard spec cable for automotive use these days, all I can say is that when we had a proper Lucas branch near us they used to supply it. There's no reason why the other specs of cable wont be just as good for you Iceman, I guess as a rule of thumb buy the best you can afford. With some of the kit that I use I can easily draw 20amps at the back of the car (not often). When I get organised I will probably link the batteries with some heavy duty starter type cable with a little idea that Trex gave me, use one of those isolator switches to overide the relay so that I can jump start from the battery.

Jim T

 

[iceman]

can this be done as my relay arrived today and i wondered if i fitted a isolator between the cable going to both positives and if at anytime my main battery died that i turned the isolator on and then after a moment start it and after finishing turn it back off.

 

[Terranosaurus]

Yup that will work. Make sure the lesure battery earth is plenty big though. My batteries are linked -ve to -ve but to earth is as good.

 

[Deleted account DD]

looks like a good scheme :thumb2 where are you putting the battery

 

[makeitfit]

Mine's going on the floor behind the passenger seat right next to the gas tank!
Could be interesting:naughty

 

[Deleted account DD]

Mine's going on the floor behind the passenger seat right next to the gas tank!
Could be interesting:naughty

You wouldnt know a thing if it became that interesting

I wondered about boot area with a leisure battery case around it (few quid from the caravan shop)

 

[makeitfit]

Well I hope these fancy new sealed type ones really are
I dont have back seats in so there's plenty of room and keeps some more weight away from the overhang up front:thumbs

 

[dino]

I see your using 10A fuses these might be a Little low, make sure the cable between the vehicle and auxiliary battery is capable of handling ?? (if your relays 100amp rated then at least 100 amp cable) amps, otherwise you can quite easily have a thermal incident.
If you only attend to draw 10A for the second battery the fuse will be OK ,anything after this then the fuse will blow.


I would also fuse the relay from alternator, if the relay goes short to earth, then you will earth your alternator and blow regulator pack or have a thermal incident.

 

[Deleted account DD]

Well I hope these fancy new sealed type ones really are
I dont have back seats in so there's plenty of room and keeps some more weight away from the overhang up front:thumbs

Sounds like a good scheme :thumb2 I wondered about doubling battery weight at the front end. Cant make my mind up on the ins and outs of it.

Do even the "sealed " ones not have some kind of vent? I know our "sealed for life" (yeah right) leisure battery has a little vent on the side that drains off out of the tray in case it overcharges or overheats

 

[makeitfit]

Just thought as I've got the winch bumper up there already I dont need the battery there too. I'm told that BMWs often have the battery in the boot, so I'll be liberating some cable from the scrap yard soon:sly
Not bought the battery yet, but I can buy marine ones at trade so will be on it soon:thumbs
LPG and turbo higher up on the ever growing list of things to do on the old beastie

 

[iceman]

i'm the person who looks at pictures then any writing in a mag lol so i will follow the diagram now thx Terranosaurus for your thumbs up.

dino i'm actually going to be using something like this that goes about right with the following,
1 x heavy duty relay 12 volt 180 amp rush 100 amp continuous,
2 fuses a 50 amp and 60 amp,
5 meters of 65/012" heavy duty cable (atm me and my elec m8 are deciding on which core cable be best),
2 meters of trigger wire ,
couple of meters of sleeving.

 

[zippy656]

hay Iceman, take a look here... might be of some help

http://www.vehicle-wiring-products.eu/VWP-onlinestore/home/homepage.php

and intrest to others

 

[iceman]

today i fitted a second battery and a relay and isolator switch, my question is it best to fit a fuse box near the leisure battery and wire all my accessories to it, or a direct link to the battery with fuses breakers along the wire.

i also wondered when my ignition is turned off my radio will not work, as my radio is needed to run tv or dvd's to the radio touch screen which will be feeding to the monitors in the back, do i just take another positive from the leisure battery and crimp it onto the positive already going into the radio.

 

[lacroupade]

I see your using 10A fuses these might be a Little low, make sure the cable between the vehicle and auxiliary battery is capable of handling ?? (if your relays 100amp rated then at least 100 amp cable) amps, otherwise you can quite easily have a thermal incident.
If you only attend to draw 10A for the second battery the fuse will be OK ,anything after this then the fuse will blow.


I would also fuse the relay from alternator, if the relay goes short to earth, then you will earth your alternator and blow regulator pack or have a thermal incident.

I just love a dry sense of humour!!! "Thermal incident" wins my vote for Euphemism of the Week :clap:clap:clap