VW T4 Forum - VW T5 Forum banner

1 - 20 of 30 Posts

·
Registered
Joined
·
44 Posts
Discussion Starter #1
Hi All,

Im hoping of buying a Split Charge kit from Raw Components and without doing a mock cable run I cant be sure how long it will need to be to run from the relay under the bonnet to my leisure battery. I was hoping to put the aux. battery in a cupboard on the drivers side about half way down the rear of the van so its positioned centrally to run other items off it. Has anyone any idea roughly how long this cable run may be and what capacity it should be to avoid any voltdrop? I was hoping to run it from the engine bay through behind the dash and then along the d/s door step to the rear.

Cheers
 

·
Registered
Joined
·
433 Posts
I'm also keen to know the answer to this. I am contenplating having my battery in the engine bay. I have been reading that for evry 6ft of cable you need to increase the amp size of the cable by 10% to reduce drop but don't quote me on that. I'll try and find the site I was reading and let you know.
 

·
Registered
Joined
·
44 Posts
Discussion Starter #3
Yeah that would be useful if you can find it. Im happy to just go as big as possible in terms of cable diameter but il be annoyed if I start to run it and find ive not got a long enough length.
 

·
Registered
Joined
·
2,008 Posts
its not just lenght of run that affect volt drop but temperature too. 16mm cable is around 2.8mV/M/A and 25mm2 is 1.75mV/M/A. Basically at the length of run you are talking about and the system you are using, Volt drop will not make that much difference to the losses from the components. That said go for the largest cable you can afford..............but 16mm should be fine.

Volt drop = mV/M/A x current x length
 

·
Registered
Joined
·
44 Posts
Discussion Starter #6
its not just lenght of run that affect volt drop but temperature too. 16mm cable is around 2.8mV/M/A and 25mm2 is 1.75mV/M/A. Basically at the length of run you are talking about and the system you are using, Volt drop will not make that much difference to the losses from the components. That said go for the largest cable you can afford..............but 16mm should be fine.

Volt drop = mV/M/A x current x length
Cheers Davie, thats encouraging. Can you confirm what mm cable people mean when they refer to a "70amp cable" for example? This is how the cable with the kit I'm interested in is advertised. No mention of mm2 or AWG etc.
 

·
Registered
Joined
·
44 Posts
Discussion Starter #7
Here is that site as promised: http://www.kampenwagen.co.uk/Electrickery.html i'm finding it usful although some of it is confusing but he does put it in idiots terms which is suiting me. Sorry couldn't get it earlier but was in work and couldn't remember it.
Hey Nogdo, thanks a lot. Just had a skim through it but I'll have to sit down with a brew for a while and get my head into it I think. Cheers :)
 

·
Registered
Joined
·
433 Posts
No worries, yea its not light reading but does give you a basic knowledge. well I hope I havn't read it all yet as it long winded.
 

·
Registered
Joined
·
2,008 Posts
'Vehicle Wiring Products' are an excellent source of ....er.....vehicle wiring products.

Used them in the past (and today!) and they have cable in lengths, and also the fittings. They have been excellent.

Battery cable, 16mm here: £2.35 a metre. http://www.vehicle-wiring-products.eu/VWP-onlinestore/cable/batterycable.php
they also have a very helpful chart that details current carrying capacity and awg and mm2 sizes of the cable. but to answer your question 10mm2 70amp.
 

·
Registered
Joined
·
407 Posts
Please tell me why you would wish to charge you leasure at the rate of 70amps?

you only want to trickle charge them.

By fitting a 70 amp cable when you start your van with a flat leasure battery you will dump 70 amps into it from the first battery!

You need to limit the current.

A 10amp battery charger only has 1.5mm 12volt leads on it!
 

·
Registered
Joined
·
1,705 Posts
Please tell me why you would wish to charge you leasure at the rate of 70amps?

you only want to trickle charge them.

By fitting a 70 amp cable when you start your van with a flat leasure battery you will dump 70 amps into it from the first battery!

You need to limit the current.

A 10amp battery charger only has 1.5mm 12volt leads on it!
i wired my leasure battery (in the middle of the van) in 2.5mm and it wont charge due to voltage drop.if i connect a coolbox to the leasure battery the 2.5mm wont keep up with the coolbox and takes a big chunk out the leasure battery after about 6 hours driving.its totally useless and ive always had to use a mains charger
1m of 1.5mm might be ok on a battery charger @10 amps but you wouldnt want to drive for 11hrs to charge a 110 amp hour battery
also the alternator on my van is 90 amps ands it doesnt damage the engine battery when thats low so im not to worried about a leasure battery which is more robust to deep cycles so i going for 16mm fused at both ends next time
 

·
Registered
Joined
·
2,008 Posts
Please tell me why you would wish to charge you leasure at the rate of 70amps?

you only want to trickle charge them.

By fitting a 70 amp cable when you start your van with a flat leasure battery you will dump 70 amps into it from the first battery!

You need to limit the current.

A 10amp battery charger only has 1.5mm 12volt leads on it!
The trouble begins if the battery is flat and it tries to pull all available power from the alternator that will melt cables and blow fuses. Thats why manufacturers use big cables to the battery from the alternator then to the starter. Mains chargers are a slightly more complex set up than a split charge relay.
 

·
Registered
Joined
·
407 Posts
i wired my leasure battery (in the middle of the van) in 2.5mm and it wont charge due to voltage drop.if i connect a coolbox to the leasure battery the 2.5mm wont keep up with the coolbox and takes a big chunk out the leasure battery after about 6 hours driving.its totally useless and ive always had to use a mains charger
1m of 1.5mm might be ok on a battery charger @10 amps but you wouldnt want to drive for 11hrs to charge a 110 amp hour battery
also the alternator on my van is 90 amps ands it doesnt damage the engine battery when thats low so im not to worried about a leasure battery which is more robust to deep cycles so i going for 16mm fused at both ends next time
Your problem is not down to your cable, its correct to charge your battery, if running a cool box during driving it should have its own feed or when you dont have it on the alternator will charge your second battery too fast, if its the correct type.

So what happens when one battery is flat and the other fully charged?

Your starter battery may like being fast charged but a proper leasure battery wont.

Would you use a leasure battery to start your van?

You need to regulate the charge.
 

·
Registered
Joined
·
2,008 Posts
really depends on your system. Mine charges my bats from flat to full in 2hrs. I have 50mm2 cables running from a diode block and use an advanced regulator to give me as much power as poss to the bat. So i do want mine to charge fast but the regulator has a cyclic effect which stops the bat from boiling. I can also start the van with the bats, but it depends on the type of bat. Mine are semi-traction vartas 110ah.
 

·
Registered
Joined
·
407 Posts
really depends on your system. Mine charges my bats from flat to full in 2hrs. I have 50mm2 cables running from a diode block and use an advanced regulator to give me as much power as poss to the bat. So i do want mine to charge fast but the regulator has a cyclic effect which stops the bat from boiling. I can also start the van with the bats, but it depends on the type of bat. Mine are semi-traction vartas 110ah.
Sorry I was unaware you had a regulator, me bad I:

I have seen so many fire ready diy jobs, a car battery has the potential to deliver huge amounts of current.

50mm2 cable? that is huge.

The best solution would be a second alternator regulated to suit the battery as on many boat installs.

I run 2 lucas sealed leasure batterys with 2x 2.5mm power feeds fed from 2 relays, the cable is run in ducting and the cable needs to be over 4M long to regulate the current.

I can switch each battery to charge or both, one normally runs the heater and the other the TV and lighting.

Caravans (is that a swear word!) use a 2.5mm split charge wire and the cable is well over 5M long with connectors in the line.

Even the VW split charge kit I have seen only had a 2.5mm cable :confused:

Either way remember the fuse is there to protect the cable and fit at both ends!
 

·
Registered
Joined
·
2,008 Posts
these systems generally assume your on mains most of the time though. I use mine wild for days with no mains.

Nogdo, If you are confused my choice of split charge would have 16mm2 cable min. I am sure raw do that. Charging systems vary greatly.................split charge in all its guises..........battery to battery................advanced regulators...........so on and so on.

Sterling battery management and Adverc provide other possibilties try googling them.
 

·
Registered
Joined
·
433 Posts
Thanks Dave, I think I will put the 16mm cable through, board, carpet and then get an electrician to do the rest.

Just another question though. Will it make any difference if I have my leisure battery in the engine bay or in the back of the van? I'm really likeing the idea of putting the battery in the engine bay to save space and for safety reasons! But does this in anyway change the wireing process, particulary cable size? Do I still put the 16mm one in and route it to the back?
 

·
Registered
Joined
·
2,008 Posts
no is the short answer..............just fuse any circuits off the battery within 9inches of it. I ran 6mm to the back from the battery to cut the volt drop.
 
1 - 20 of 30 Posts
Top