 | Home > Maintenance & Modifications > Battery Leads for Dual Battery Installation ? |
 
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| LinDens90XS Member Since: 24 Feb 2012 Location: Merseyside Posts: 83  
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With my limited electrical knowledge, does that not make it into an 24 volt system? Regards
Dennis. |
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24th Jan 2016 9:43pm |
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| LRmud Member Since: 22 Oct 2014 Location: IV12 Highland Posts: 198  
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Check out Autosparks website. It might have the stuff you need.
http://www.autosparks.co.uk/electrical-components.html Best of luck  --------------------------------------------------------------------------------------------------
1989 Defender 90 Toyota Aygo & Honda FR-V |
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24th Jan 2016 9:43pm |
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| mrd1990 Member Since: 16 Aug 2012 Location: Wales Posts: 600  
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Don't forget when you connect two batteries in parallel like that, they will drain each other constantly unless the positive is disconnected between the batteries. The simple option is to use a relay and activate it by an ignition live feed such as the positive going to the cigarette socket.
As for all the leads, build them your self.. its easy, cheap and you get the exact length you need. |
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24th Jan 2016 9:48pm |
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| Nostromo Member Since: 17 Jul 2015 Location: The Mendip Hills Posts: 73 
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Well I dont think so Dennis, as I understand it, two 12 volt batteries wired in parallel as shown in the diagrams are still 12 Volt in total . . you have to wire them in series to get 24 Volts. My understanding is, that wiring two in parallel gives you the effect of a bigger longer lasting 12v battery.  |
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24th Jan 2016 9:48pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971 
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I see where they're coming from with their connections, but I can't see it making that much difference so I'd go with whichever is easier to wire up. Batteries aren't perfect so one will always discharge better than the other, however it will be slight and will balance out once they get to full charge. In an ideal world, yes, but there are far greater worries! Keep the additional cable runs short and use heavy cable.
Where to get stuff from... https://www.mobilecentre.co.uk/ are a site sponsor and seem popular. We buy quite a bit of stuff from these guys: http://www.beal.org.uk/automotive/automoti...00146.html their service and prices are good in our experience. The only slight snag is that they only sell heavy cable 10m at a time. I think I'd be tempted to buy 10m red and pop some black sleeving over the negative one! |
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24th Jan 2016 9:49pm |
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| JAY BOY Member Since: 04 May 2010 Location: Not here Posts: 1706
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Series batteries together and you get 24v Parallel batteries together and you get 12v double the current. |
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24th Jan 2016 9:53pm |
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| Nostromo Member Since: 17 Jul 2015 Location: The Mendip Hills Posts: 73
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Thanks for your advice, again I wouldn't know where to go for the lead components or what exactly to ask for or search for if I was looking on line. re the battery draining effect you mention, I did read about that, but the view appeared to be that if the batteries were an identical pair and properly wired, then the current flow between them would be negligable and wasn't a problem ? . . . but maybe thats not the case ? |
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24th Jan 2016 9:54pm |
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| mikeh501 Member Since: 07 Jan 2013 Location: United Kingdom Posts: 1142
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http://www.vehicle-wiring-products.eu sell made up cables to your spec. Choose wiring diameter and length and they professionally crimp, solder and heat shrink the connector of your choice. I wouldn't bother doing it yourself for large diameter cables as you need decent tools to crimp those large cables. It was pretty cheap if I remember correctly.
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24th Jan 2016 10:02pm |
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| LinDens90XS Member Since: 24 Feb 2012 Location: Merseyside Posts: 83
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Thanks for the info. As they say you are never to old to learn something new. Regards
Dennis. |
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24th Jan 2016 10:03pm |
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| dorsetsmith Member Since: 30 Oct 2011 Location: South West Posts: 4554 |
two 12 volt battery in parallel i.e. + to + and - to - is 12 volt at high Amp Hours two 12 volt battery in series = 24 volts |
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24th Jan 2016 10:30pm |
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| JWL Member Since: 26 Oct 2011 Location: Hereford Posts: 3443  
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As I'm getting older and further away from school and college I allways use the thought that 'in parallel' is + to + still keeping the same voltage, 'in series' is what happens in most of your torches and transistor radios where you're fitting 1.5V AA batteries but sticking them in series ie + to - so you get a bigger voltage, 2 x AA batteries gives you 3V, 3 of them 4.5V etc etc.
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25th Jan 2016 12:36am |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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As an electronic engineer that does parallel batteries at work, that's what I'd always understood too 
You can parallel dissimilar batteries but it's not good for them. |
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25th Jan 2016 8:02am |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8580
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Looking at that parallel battery arrangement, what it does is give a much larger capacity Ahr of the battery system. A quick google showed it come from a caravan/motor home type site. The argument in wiring in fashion B is due to voltage drop along the wire connecting the two positive terminals and on the single earth cable.
Now if all you are interested in is larger capacity battery then it is possible to buy single 12 volt batteries with capacity exceeding 200 Ahr. Yes you will probably have to relocated the larger battery. Voltage drop IIRC is dependent on two things, length of wire and cross sectional area of wire. Longer the wire and the smaller the CSA the bigger the voltage drop. With the typical distance of say 250mm and 35mm2 CSA between 2 Defender batteries I struggle to see the 0.5 volt drop on that positive cable. If there is a 0.5 volt drop there what would the voltage drop be in the 1.5m cable from the alternator? 3+ volts? The typical twin battery set up in a Defender has the primary battery as engine and vehicle functions and the auxiliary battery running fridges etc off the secondary battery. I.e. Positive cables from both batteries with an isolator between the two batteries. Without that isolator you run the risk of having a flat starter battery. I would suggest you follow something like the IBS dual battery system wiring system. Beat at IBS has only been dealing with designing and manufacturing dual battery charging systems for 20+ years. Brendan |
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25th Jan 2016 8:54am |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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Brendan, the other thing to take in to account with voltage drop is the current the cable is taking. You won't get any volt drop if there's no current flowing, V=IR, the bigger the I (current) or the bigger the R (resistance, small cables=high resistance) the bigger the V. As the battery gets topped up, the current drops so the volt drop reduces. What that means in practice is that once the battery nears full, it gets the full voltage it needs to top off. Voltage drop isn't a static thing, that's why if you take the headlight off and measure the voltage you get a much higher reading than when the bulb is lit.
Using 35mm2 cable as you mentioned, the first place I've found lists it as 0.000564 Ω/m. Say we have 50cm of each of + and -, at the full rated current of 240A (which is half the maximum load of a winch) V=0.14. When you're charging at 50A that's going to be 0.03V. It would be good to link them as in the picture, but I wouldn't bust a gut doing so. On the subject of split charge, I wouldn't say there was any point for winching. You'll be joining both batteries together anyway with the winch running and it just adds more things to the system with their own associated voltage drop. |
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25th Jan 2016 1:11pm |
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