Hodge's Dual Battery System

[Hodge]

OK time for me to expand this cars travelling luxuries. I need to organize and get a dual battery system fitted. So I need to know if this is the right path to go.
I don't need anything extravagant. I'll only be running a fridge and a few lights at the back for now anyway.
This is what I've come up with.
Already have a battery tray under the hood so this is already done.

- Redarc BCDC 25A unit with MPPT for future solar provisions if I ever go down that path.
http://www.ebay.com.au/itm/REDARC-BCDC1225-DUAL-BATTERY-ISOLATOR-SYSTEM-DC-TO-DC-MPPT-SOLAR-4X4-4WD-AGM-/300914060803?pt=AU_Car_Parts_Accessories&hash=item460fe02e03&_uhb=1

- At the back I'd like one of these units. I'll be running an ARB fridge so, this has an engle socket ready to go, as well as a few other bits. And fits nicely in the corner at the back.
http://www.ebay.com.au/itm/BAINTECH-NISSAN-GU-POWER-PANEL-MERIT-ENGEL-WAECO-/171285989076?pt=AU_Car_Parts_Accessories&hash=item27e170c6d4&_uhb=1

- Battery? Now this is my biggest puzzle. Recommendations are most welcome. As above, I'll running a fridge, few lights, charge a few phones etc... Nothing special. Something around 100Ah perhaps ???

Shoot me with opinions please.

[Family4x4]

Another option for the back.

http://www.ebay.com.au/itm/400581545507?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

[Hodge]

Thanks mate. Definitely an option with more features, and I'm 50/50 between that one and the one I listed. Although the one I listed replaces that rear corner pocket as its designed to fit in perfectly and looks neat.

[graeme1969]

Gday,

This battery that mitch.mccabe purchased on here a couple of days ago seemed to receive favourable comments.

http://www.nissanpatrol.com.au/forums/showthread.php?26695-Dual-Batteries-or-one-single/page4

[sooty_10]

Hodge although the redarc is a decent unit just be aware that a simple dual sensing solenoid utilising the alternator will bulk charge a battery under the bonnet a lot quicker. If your running long lengths of cable a DCDC charger becomes beneficial due do voltage drop. The redarc will still work damn good and probably get that last ~10% charge more efficiently. However a simple smart solenoid setup will be a fair bit cheaper. There is quite a bit of info on the site and no doubt you've already read it, just thought I'd add it here.

[the evil twin]

What he said ^^^^

The three biggest reasons IMHO...
I am not a fan of putting those complex units where they are constantly subjected to high temps under the bonnet.
Considering the cable run is probably 2 metres or less there is not much point because, as Sooty mentions, you get bugger all voltage drop
They won't connect back to the Cranker for Jump starts like a "smart solenoid"

[Hodge]

Much thanks for the replies. Evil and Sooty, I can see your point. Till now I haven't even thought or considered a simple option like that.
I'll be doing some homework on this, over the next week. Battery is decided.
This battery seems like a winner though. Thanks Graeme. Purchased from that shop many times, always good service.
http://www.ebay.com.au/itm/130AH-AMP-HOUR-BATTERY-AGM-SLA-12-VOLT-12V-DEEP-CYCLE-DUAL-FRIDGE-SOLAR-/400634846771?pt=AU_Car_Parts_Accessories&hash=item 5d47b29e33&clk_rvr_id=618662801959

[Hodge]

Alright, I need to step this up a level. BCDC1225 25A unit is decided, as I scored one for peanuts. I will be running 8 gauge wire to the back, through a fusable link block, and then onto relevant loads, which will just be a fridge, rear light and some LED light strips around the doors etc...

Running the wire to the back... Need opinions, did you run it through firewall, and then under the trims between doors and seats, or did you run underneath the car and popped back up at the rear?
The other thing is, AGM batteries not so good under the bonnet? I didn't know this until someone mentioned to me today. So more confusion. :S

[mudski]

Just get a deep cycle for under the bonnet mate. you can run them almost flat and recharge them. Decent deep cycles are designed to discharge down to around 20% of its capacity, the cheaper units maybe around 40%.
A Redarc SBI12 would be more than enough for under the hood too. And still cheaper than the DC-DC.

[deanfurley]

Just get a deep cycle for under the bonnet mate. you can run them almost flat and recharge them. Decent deep cycles are designed to discharge down to around 20% of its capacity, the cheaper units maybe around 40%.
A Redarc SBI12 would be more than enough for under the hood too. And I'll still cheaper than the DC-DC.

I thought like 80% was the minimum? I thought 12.7 volts was the danger level.

Choppa seems to be the man to talk to about this stuff, from what I have read.

[threedogs]

I have the simple Redarc solenoid unit on the firewall running a Trojan 115 AH battery ,
these are wet cell and the same battery they use out on the shipping bouys in the Bay.
You might be better off running a designated wire and thermo couple to power your fridge,
using a merit or better still a 50A Anderson or the twist lock Engel/baintech plug and socket.

[cjb]

My 2 cents what about the SBI12D. If you run your main down it can jump it.

[megatexture]

Ive got a ctek, same sort of thing... regarding jump starts just run a wire from pos to pos and have an isolator switch under the bonnet ..or use jumper leads .if anyones getting a flat enough that they need a switch on the dash to link batteries for convenience then they some bugs to work out.

11.6 volt is half charge of a battery any lower than that and you will do damage to any battery agm's are just able to discharge that little more but it will still be doing damage

[Cuppa]

I have stayed quiet on the dual battery set up discussions lately.
I will make my points in this post & leave it at that, hopefully remembering where I did so, so I can refer back to here in future, rather than becoming overly repetitive.

I have trouble accepting the ‘the battery will charge faster via a smart solenoid than it will via a dc to dc charger’ statements.
Whilst they are true to an extent I believe they are statements which need qualifying.

An alternator will ‘bulk charge’ an aux battery (ie. via a solenoid) faster than most DC to DC chargers.
HOWEVER this bulk charging will only take the battery (AGM) up to around 80% charged (lower for wet batteries), unless as some here have found the owner drives for a long time.
ALSO if the owner is treating his/her battery well, they will not have discharged it below 40% to 50% & thus the period of bulk charging will be far less than the battery murderers who lets their battery become discharged to a point of being ‘flat’. (If treated this way no type of charging will help to prolong battery life).

Where the DC to DC chargers come into their own are as ET suggests when batteries of different voltage/chemistry to the crank battery are used, or where voltage drop courtesy of distance from the alternator are issues. HOWEVER where they also help greatly is in two further ways.

1. Charging the battery from around 80% to 100% in the shortest possible time - might not sound a big deal, but if you treat your battery well to ensure it lasts for many years by not discharging it beyond 50%, that extra 20% virtually doubles your ‘useable capacity’. Getting that extra 20% in with a DC to DC charger will be much quicker than direct from the alternator (via a solenoid).

2. Many batteries are killed by undercharging, but many also by overcharging. Lots of folk have a dual battery system where effectively the aux battery is unused most of it’s life. Every time the engine runs, the alternator is trying to charge it by throwing 14.something volts into it. A DC to DC charger is a bit smarter & ‘floats’ the battery at a much kinder voltage once full. My one at 13.3v. Others usually at around 13.6v.

Ask all the folk who happily state how well their solenoid set up works how long their batteries last for. Most are pleased to to get 4 years, many get a lot less. I will be very disappointed if I get less than 8 years, & hope for more.

It is possible to set up the aux battery to provide emergency jump starting whilst having a dc to dc charger, I have. It does mean however that the emergency ability bypasses the charger.

Worth dispelling the myth that a solenoid is a charger. It is not. It is just a switch which allows the alternator to charge the battery.

I have found that the 40 amp dc to dc charger I have to charge my bank of 360Ah AGM batteries to be quite adequate for my purposes, (in conjunction with solar if camped without driving for more than a couple of days). Should a 40 amp unit be insufficient for anyone, there are a couple of choices which allow the user to continue to be kind to their batteries. Either install a dc to dc charger, but have a means of bypassing it, allowing bulk charge from the alternator to bring the batteries up to around 80% as quickly as possible & then switch over to dc to dc charging to ’top up’. (I have this ability in case I am ever in the situation where my batteries have been discharged lower than normal & I don’t wish to drive a long distance) OR to use the Ctek DC to DC charger in conjunction with it’s Smart Pass ‘box’, which I believe allows smart charging at up to 80amps. (Even though some alternators are capable of putting out more than 80 amps it is unlikely that the battery capacity used by most 4wd’ers would accept this amount of charge. Allowing an alternator to continuously output close to it’s full capability for more than a short time is also a good way to kill the alternator).

Of course it can also be argued that the expense of fitting DC to DC chargers can be offset by using a simpler solenoid set up & buying replacement batteries more often. The point is that those who want their batteries to run their fridge, lights etc over a full weekend will need to do this & batteries are not cheap. In the long run the DC to Dc setup will work out to be cheaper , & I personally feel better about making my batteries last longer, & conserving resources.

Again I want to be clear that I am not looking to be argumentative or tell others what they should do, just repeating my thoughts in a regular ‘horses for courses’ debate.

[Cuppa]

11.6 volt is half charge of a battery any lower than that and you will do damage to any battery agm's are just able to discharge that little more but it will still be doing damage

From the table below you can see that 11.6v would actually be only around 20% capacity - well into battery damage territory. Half charge is around 12.1v (on a rested battery with no loads of course). My preference is to never to let the voltage drop below 12.2v, but with smaller battery capacity this can be impractical. I would suggest a minimum of 11.9v or higher if long term damage is to be avoided.

46475

[Hodge]

Thank you for everyones' input. I might have mentioned it in the earlier posts, I have gone down the DCDC path. I'm in the process of getting everything fitted, with a Redarc 25A charger. In a nutshell, the only advantage of the smart solenoid is he ability to parallel the main and the off-set batteries, for starting purposes. Nothing a set of leads could fix.
Cuppa's write up just about sums everything that I've researched, and clarifies the DCDC is what I need.

[lhurley]

From the table below you can see that 11.6v would actually be only around 20% capacity - well into battery damage territory. Half charge is around 12.1v (on a battery rested battery with no loads of course). My preference is to never to let the voltage drop below 12.2v, but with smaller battery capacity this can be impractical. I would suggest a minimum of 11.9v or higher if long term damage is to be avoided.

46475

Thats a really handy diagram. Would be something to print out and have on hand, stuck near your voltage meter or in with your multimeter.

[Cuppa]

Thats a really handy diagram. Would be something to print out and have on hand, stuck near your voltage meter or in with your multimeter.


Yes but do bear in mind that it is only going to be accurate(ish) if the battery is doing no work & has done no work for half an hour or so. Something that never happens with a cycling on/off fridge. It really is only a very rough guide. Switch something on & the voltage might drop below (for example) 12.06v. This does not necessarily mean that the battery has been 50% discharged, because when the ‘something’ is switched off, the voltage may slowly rise back up. So voltage cannot be used as a ‘Battery fuel gauge’. Where it IS useful is in providing the battery owner with comparative data, this becomes useful in regard to developing a familiarity with your system over time, so you have a better idea of whether what you observe is ’normal or to be expected in the circumstances.

The only way to have a ‘Battery fuel gauge’ is to use a battery monitor with a shunt. This counts the amps in & amps out, with the user having set the total capacity. Even then it is not always 100% accurate, because of the way a battery works (chemical reaction), but it is the best there is available. Personally I prefer the ‘familiarity model’ but this takes time & regular use to achieve, not easily done on a weekend here & there.

[mudski]

I have stayed quiet on the dual battery set up discussions lately.
I will make my points in this post & leave it at that, hopefully remembering where I did so, so I can refer back to here in future, rather than becoming overly repetitive.......
.
.
.

Again I want to be clear that I am not looking to be argumentative or tell others what they should do, just repeating my thoughts in a regular ‘horses for courses’ debate.
Mate can you just repeat what you said. :D

[Hodge]

Got all the bits and pieces, ready to go. Just wondering one thing. The negative from battery to battery. I can just ground the secondary, but am I right to also run a cable between each battery too ??

[Cuppa]

Got all the bits and pieces, ready to go. Just wondering one thing. The negative from battery to battery. I can just ground the secondary, but am I right to also run a cable between each battery too ??

Yes you can just run a neg cable between the two. It should be the same size cable as the positive. In many cases this is more reliable (& can also make any future fault finding simpler) than using chassis earth.

[Hodge]

Yes you can just run a neg cable between the two. It should be the same size cable as the positive. In many cases this is more reliable (& can also make any future fault finding simpler) than using chassis earth.

Thanks Cuppa. I don't see many people doing this most just ground it to chassis so I thought I better ask if there was a "negative" in running a hard negative between batteries as well as grounding it. I'll do both.

Sent from my SM-G900I using Forum Runner

[Cuppa]

Thanks Cuppa. I don't see many people doing this most just ground it to chassis so I thought I better ask if there was a "negative" in running a hard negative between batteries as well as grounding it. I'll do both.

Sent from my SM-G900I using Forum Runner


No advantage in doing both. If intending to fit solar down the track I feel there is an advantage to essentially keeping the ’house’ electrics separate to the vehicle electrics.

[Hodge]

Took advantage of good weather today, and finished the dual battery system. Was hard finding a spot for the redarc unit so, i made a stand-off bracket, for it, and fitted the fused on top, works a treat and looks neat. Ran 2 twins to the rear, which I'm yet to terminate into a some form of fridge plug? I'm not sure what the ARB fridge plugs into until I buy one. And one of the circuits will be just tapped into a 6 way box and spread from there onward to lights and other gadgetry.

4716447165

[Hodge]

So I want to wire up my spare wheel bracket/light for 2 functions. A reverse light and camping/general rear light.
Whats the best way to go about it? Put a relay in, that's triggered by the reverse hot wire, and also have a switch that triggers also triggers the relay when I want the light on manually. Does this sound feasable?

[mudski]

Looking neat mate. As for the reverse light, that's how mine is setup. Comes on with reverse, but I can also turn the rear light on via a switch. Which also turns on the reverse lights to but it's no issue to me.
How it's done was via a relay but I can't remember how. MudRunnerTD showed me how ages ago in a thread here. I'll see if I can find it if you like bud.

[megatexture]

A few option in here for your wiring re the reverse light http://www.nissanpatrol.com.au/forums/showthread.php?14737-7-pin-on-off-on-switch/page2

[Flex]

Hodge loved how you cable tied the spare fuse. Great idea!!!

[mudski]

Heres the thread that Daren helped me with. Starts from about post #19...
http://www.nissanpatrol.com.au/forums/showthread.php?20033-GU-Centre-console-switches-What-fits-three&highlight=reverse+light

[Hodge]

Thanks fellas. Have been going through those threads and some other reading ... It's amazing I work with power every day yet car electrical gives me a headache. lol
I was looking at Darrens drawing, and it is perfect for what I need... however. With that setup, when I manually turn on the light, the reverse lights will turn on too. This is something I want to avoid.
In a nutshell I need a relay that can be triggered from 2 different sources ( reverse light and manual switch), yet not interconnect those 2, if that makes sense ?

47200

[Hodge]

This is what I just drew up quickly. Would this work ????

47203

[Flex]

It will, however when you turn your work light switch "manual switch" on your reverse lights will come on

[megatexture]

One rocker switch on/off/on or on/ on would stop that rather than 2 individual switches

[Hodge]

It will, however when you turn your work light switch "manual switch" on your reverse lights will come on

Yeah I just realized I didn't quiet draw that well. So thinking about it, I need a relay, with 2 of those "86" positions, that are not interconnected, so the 2 trigger sources never end up being in parallel.

[Hodge]

Also, that Reverse switch is the switch at gearbox, it's not an additional switch. I didn't label it right. I'd have the relay at the back of the car, and the reverse wire I'd pickup from loom, on the right, just tap into it, so when it becomes "live" it triggers the relay.

[mudski]

Thanks fellas. Have been going through those threads and some other reading ... It's amazing I work with power every day yet car electrical gives me a headache. lol
I was looking at Darrens drawing, and it is perfect for what I need... however. With that setup, when I manually turn on the light, the reverse lights will turn on too. This is something I want to avoid.
In a nutshell I need a relay that can be triggered from 2 different sources ( reverse light and manual switch), yet not interconnect those 2, if that makes sense ?



If you work it out, let me know. But it's no biggie having the reverse lights come on too. Bit of extra light...

[Flex]

I've modified your drawing, basically I've added a diode between the reverse switch and the relay, this will stop the reverse lights coming on with the manual switch:

47204

You can buy them from Jaycar or eBay them (Cheap cheap):
http://www.jaycar.com.au/productView.asp?ID=ZR1004

[Hodge]

I've modified your drawing, basically I've added a diode between the reverse switch and the relay, this will stop the reverse lights coming on with the manual switch:

<img src="http://www.nissanpatrol.com.au/forums/attachment.php?attachmentid=47204"/>

You can buy them from Jaycar or eBay them (Cheap cheap):
http://www.jaycar.com.au/productView.asp?ID=ZR1004

Thanks bud. Was thinking of a one way valve ( diode), tried to see if there was a workaround first. I'll go with this though. Will report back. Cheers !

Sent from my SM-G900I using Forum Runner

[Hodge]

OK. Done some wiring tonight. Bought the diodes as flex suggested. But I actually went down the path megatexture suggested. And below is the updated diagram, of how I've done it. The on/off/on switch replaces 2 switches, or a switch and a diode. Flicked up, is normal/usual position while I'm driving for reverse etc.... Flicked down, is when I want the light on without the reverses, camping/work light etc... And the middle turns them both off. I got all the bits, but haven't finished the wiring yet, on paper it should work, but will find out tomorrow when I put it in practice!


One rocker switch on/off/on or on/ on would stop that rather than 2 individual switches

47241

[mudski]

That won't work mate. Your diagram is wrong.
Your tail lights are different to the one pictured... :p

[Hodge]

That won't work mate. Your diagram is wrong.
Your tail lights are different to the one pictured... :p

Yeah wrong lights, cause I'm waiting for the LED versions from someone.... :tease:

[mudski]

Yeah wrong lights, cause I'm waiting for the LED versions from someone.... :tease:

So am I.... Bloody GQ lights are holding the order up.

[CarlLC78]

47256

Dodgy pic but this one worked for me. Ran 12v feed off sub battery

[Hodge]

47256

Dodgy pic but this one worked for me. Ran 12v feed off sub battery

Thanks for that. Definitely makes sense. Might have to re-think this then.

[Hodge]

Wired in the GU baintech panel. These come with all the sockets wired up piggy-back style at the rear. I've re-wired this so the Engel plug has a dedicated feed from the battery, so it feeds the fridge.
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