 | Home > Maintenance & Modifications > Dual battery installation - critique my wiring diagram! |
 
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| mikeh501 Member Since: 07 Jan 2013 Location: United Kingdom Posts: 1142  
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Hi all,
1st post  been lurking for a while and on other forums. My batt recently died on my 90 which spurred me on to sort out a dual battery installation. Ive now bought the 2 batteries and have started to plan out what electrics i want on the vehicle and how i want the wiring arranged. So i thought id put together a wiring diagram which i can then show a proper auto-electrician and get a quote for the work. given i know a number of people have put dual batteries into their defenders then im asking what you think of my wiring diagram! whether its any good or complete cobblers!
EXT AND = External anderson connector for jump leads VSR = Bluesea automatic sensing relay for battery charge/discharge 4-POS BUS BAR = Those metal bars with 4 posts which you can use to tidy your electrics 12-DIST FUSED = A 12 way fuse box for connecting ancilliraries  Click image to enlarge Electrical Setup by mikeh501, on Flickr No fuse on winch? just an isolator, as i read that winches draw a variable current which means id have to put a very very big fuse in place defeating the object? Chassis earth back to bus bar not battery? thoughts... |
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8th Jan 2013 1:35pm |
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| Go Beyond Member Since: 30 Jan 2012 Location: Headcorn, Kent Posts: 6678
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I'm looking at this on my iPhone do not had a good look but I would say its still worth putting a large mega fuse on each positive as it will blow if there is a dead short, in the event of a collision for example.
I've used the bus bar arrangement for my earths too, worth adding an additional earth within the battery box as a security precautions Also the top diagram differs from the bottom, have you mislabelled the batteries in one of them ? |
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8th Jan 2013 1:43pm |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8581
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A few comments for you Mike.
Depending on battery sizes and vehicle you may need to level off the bottom. Depending on size of batteries positive terminal might be getting close to box lid. Rubber cover over positive terminals plus insulate bottom of lid. Why 2 12 way fuse boxes? That is 24 extra circuits rather a large number I would have thought!. Check on phyiscal size of fuse boxes if putting them in main battery box Why use a 4 post bus bar? A stud terminal connector can take 4 35mm2 cables Is your auxiliary battery a starter/leisure battery? Winches draw high currents whereas radio etc is low. Is your ACR a linkable one? Useful if main battery goes down or doing lots of winching. Your fuse boxes have a 100 amp fuse in line plus a relay isolator??? Brendan |
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9th Jan 2013 8:56pm |
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| Luismi Member Since: 04 Nov 2010 Location: Cotswolds Posts: 178  
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Nice schematic, however find a sensing relay, your ACR/VSR, that you can manually operate too.
My schematic differ of yours just a bit , mine has a battery selector 1-2-both-off in negative rather than your bus bar. This two things will give me some options , like i can start the engine with battery 1 or 2 or i can disconnect all and do some welding in the car. Hope this helps |
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9th Feb 2013 10:52pm |
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| mikeh501 Member Since: 07 Jan 2013 Location: United Kingdom Posts: 1142
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ive slimmed it down to one at the mo. i was thinking of balancing the load across 2 fuse boxes, but it is total overkill tbh.... nothing wrong with that lol
Didnt know that, ill go have a look.
ive bought 2 Numax CXV-X 1000 which are both leisure and starting as i understand it. Ive measured up and they should fit in the battery tray 
I was thinking of one of those bluesea 120a ACR. its the one which doesnt have the remote button. Just wasnt sure if the more expensive one was complete overkill! 
I wanted a way of isolating all the ancillary equipment in one go, so an isolator for the fuse boxes and one for the winch. you think this is bad? i still need a fuse even if i have an isolator right? |
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10th Feb 2013 9:16am |
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| mikeh501 Member Since: 07 Jan 2013 Location: United Kingdom Posts: 1142
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Thanks
I think your talking about the more expensive bluesea ACR which brendan mentioned also. im not sure if its more than i need. we will see. re: the battery isolator, im not sure how would work. so on the nagtive side you wire my earths into a switch which allows me to isolate either battery, or knock out all the earths thereby turning off the vehicle? is that correct? will the switch have enough amperage to handle all the loads? i was worried a 350a bus bar wouldnt be enough to handle the peak loads from the winch and ACR in certain scenarios.... am i worrying about somethign which wont happen  |
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10th Feb 2013 9:22am |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8581
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An isolator for the winch is a good idea. Am not sure I would put a fuse inline. Remember at full load winch could be pulling up to 500 amps. Double lining halves the load and speed though. Having a blown fuse when winching????
I can see the logic of isolating all the auxiliaries however I would not do it. Not a bad idea in itself, just different people have different ideas/ways of doing things. Get different ideas and then decide what is best to suit your needs. Brendan |
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10th Feb 2013 9:59am |
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| VeeTee Member Since: 06 Mar 2011 Location: Somewhere Posts: 1512 
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Is the VSR capable of handling (very) high currents? Because the winch is draws its current from the ancillary battery, there will be leveling between the ancillary and starter battery during winching.
I would rather connect the winch to the starter battery, so when the winch is used and the engine is on, the alternator can deliver some of the current needed directly to the winch without need to go through the VSR. Cheers, Vincent 1959 Polynorm 1/4 Ton Trailer, Olive Drab Green (sold) 1970 M416 Military Trailer (Camping Trailer Conversion), Epsom Green (sold) 1975 Series III 88 V6, Light Green (sadly sold) 1996 Defender 110 CSW 300 Tdi, Epsom Green (sold) 2000 Freelander 1 TD4 3-drs, Silver (sold) 2006 Freelander 1 TD4 5-drs Facelift Automatic, Tonga Green (sold) MySite |
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10th Feb 2013 11:46am |
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| mikeh501 Member Since: 07 Jan 2013 Location: United Kingdom Posts: 1142
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Hmmm I don't it. Was looking at this one which is 120a continuous. http://www.mobilecentre.co.uk/index.php?ma...cts_id=245 They do a bigger one which is 500a. Just a thought but if the winch is taking load from the ancillary battery surely the vsr will disconnect the two batts? Is it the norm to connect the winch to the starter batt rather than ancillary battery? |
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10th Feb 2013 12:54pm |
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| Luismi Member Since: 04 Nov 2010 Location: Cotswolds Posts: 178
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[quote="mikeh501
Thanks
I think your talking about the more expensive bluesea ACR which brendan mentioned also. im not sure if its more than i need. we will see. re: the battery isolator, im not sure how would work. so on the nagtive side you wire my earths into a switch which allows me to isolate either battery, or knock out all the earths thereby turning off the vehicle? is that correct? will the switch have enough amperage to handle all the loads? i was worried a 350a bus bar wouldnt be enough to handle the peak loads from the winch and ACR in certain scenarios.... am i worrying about somethign which wont happen [/quote]
Hi Mikeh I always speak about the most expensive stuff on this matters  always i money well spend, i cant think of my car on flames because i save some money, for certain i will go for at leat 400 Amp continous rating.
Yes the negative switch will stop all the electrical if you want. if you decide to go for that you can use the 500 Amp switch as the blue sea PN3002 Hd series or similar. About the current capacity just as an example land rover install 25 mm2 cable to feed the winch, when i will go for a 95 mm2, Leeds is right this have to work for you, in my case i do it that way because i want fully control my electrical instalation, i have two warnings already and i work on a related sector. 120 Amp is clearly not enough if you are running the winch i use 120 amp relay just for the compressor and a continuos 400 Amp relay that work alone to do the charging and protect battery 1 of discharge. Initially i plan to install a battery isolator however as i have an inverter/charguer installed i have to discard that option. My 400 amp "smart relay" put in parallel at demand the two batteries for winching to split the "pain" if that makes sense. HTH |
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10th Feb 2013 4:20pm |
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| mikeh501 Member Since: 07 Jan 2013 Location: United Kingdom Posts: 1142
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thanks for all the feedback guys, its invaluable. the reason for the 120a bluesea ACR was that id read that the amps between batteries (at least those in a state of normal charge) is fairly nominal, so assumed nothing like 120a would be flowing between them, except on occasion. what i cant get my head around... if you have a winch pulling 400a load from the ancillary battery, how much of that load is being pulled through the ACR from the starter battery? surely the path of least resistance is to the ancillary battery and not through the ACR.... confused.com |
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10th Feb 2013 5:51pm |
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| VeeTee Member Since: 06 Mar 2011 Location: Somewhere Posts: 1512
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Some interesting reading here... Cheers, Vincent 1959 Polynorm 1/4 Ton Trailer, Olive Drab Green (sold) 1970 M416 Military Trailer (Camping Trailer Conversion), Epsom Green (sold) 1975 Series III 88 V6, Light Green (sadly sold) 1996 Defender 110 CSW 300 Tdi, Epsom Green (sold) 2000 Freelander 1 TD4 3-drs, Silver (sold) 2006 Freelander 1 TD4 5-drs Facelift Automatic, Tonga Green (sold) MySite |
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10th Feb 2013 7:51pm |
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| Luismi Member Since: 04 Nov 2010 Location: Cotswolds Posts: 178
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You will have the alternator and the starter battery in the other side of the ASR then, based on your diagram and the setup of your ASR, you will work with all (alternator, batt1 and batt2) in parallel in that case.
Then you will need to consider alternator and Starter battery current going through the relay. Depending of the status of your batteries..., but thinking in a good battery, after you start the engine the alternator will send to the battery arround 60 Amp for 10 to15 seconds , after that normally you can read 3 to 5 amp going to the battery and alternator take the rest( consupmsion, lke radio ligths o on) this means that your ASR in arround 30 sec after start will conmute to close and put in parallel the second battery. Please keep in mind that depend of the status of your batteries and the current setup of your ASR Cheers |
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11th Feb 2013 2:09pm |
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| SteveG Member Since: 29 Nov 2011 Location: Norfolk Posts: 660 
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As you've bought two identical batteries, why not just wire them in parallel. Then wire winch + and - directly to batteries via isolator. Keeps everything simple and no chance of limiting power to winch. Cheers Steve |
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11th Feb 2013 2:39pm |
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