Sidestep the dual battery system





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  1. #1
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    Default Sidestep the dual battery system

    I am going to just drop this here and see what happens.

    I have seen to many aux batteries die, due to non use, wrong charging and a number of issues.

    So I am busy with a 4500EFI LC pickup and I intend to bypass all that with a 682 battery.
    Then all the accessories go via a low limit cut out. So if the battery goes below a specified level, the accessories die.

    https://www.communica.co.za/products/cem-1007-low-battery-cut-out


    This is for 10A. For more, just hook up a relay.

    Click image for larger version. 

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    Might just fiddle the cut-out voltage. Will also add a timer. Just to add a 30sec delay before he acc come back online, after starting.

    Most modern cars have bigger alternators now and charging 2 batteries takes just as much amperage as 1 big one does.

    Something like this.

    Click image for larger version. 

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    Last edited by Henris; 2019/09/17 at 06:13 AM.
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  3. #2
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    Default Re: Sidestep the dual battery system

    My 2c

    Negatives
    - At 500m long and 35kg it's a monster ito space and proper bracket installation
    - Designed to provide a massive 840 Amps CCA
    - meaning thin but many plates construction, more susceptible to sulfation at low SOC

    Positives
    - It's a Dixon
    - 120Ah for R2200 not bad - worth a try
    - It is not sealed - therefore properly serviceable

    Challenges
    - Will be OK for long driving distances, short stops / single overnights
    - Low voltage cut out device for Accessories must be accurately adjustable
    - Once the SOC is too low to crank your vehicle a jump start supply will have to be a monster as well - especially on a diesel - think cold mornings.
    - Have some backup plan...maybe a small cheap battery box with a charged 638L Dixon Deep cycle stashed away somewhere, holds charge for weeks
    Last edited by Dungbeetle; 2019/08/25 at 08:25 AM.
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  4. #3
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    Default Re: Sidestep the dual battery system

    A lot depends on specific circumstances.

    How many accessories and how much current they draw.
    How important is it for them to run.
    How much time driving vs standing.
    How easily the car starts.

    And probably a host of other factors.
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  5. #4
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    Default Re: Sidestep the dual battery system

    Quote Originally Posted by Fluffy View Post
    A lot depends on specific circumstances.

    How many accessories and how much current they draw.
    Quartz halogen hunting light
    Fridge for drinks

    How important is it for them to run.
    How much time driving vs standing.
    Quite a bit of driving in between.
    How easily the car starts.
    That 4500EFI start when you tap the key.

    And probably a host of other factors.
    It is a hunting vehicle. So no real huge periods of time that it will carry accessories.
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  6. #5
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    Default Re: Sidestep the dual battery system

    Quote Originally Posted by Dungbeetle View Post
    My 2c

    Negatives
    - At 500m long and 35kg it's a monster ito space and proper bracket installation
    - Designed to provide a massive 840 Amps CCA
    - meaning thin but many plates construction, more susceptible to sulfation at low SOC

    Positives
    - It's a Dixon
    - 120Ah for R2200 not bad - worth a try
    - It is not sealed - therefore properly serviceable

    Challenges
    - Will be OK for long driving distances, short stops / single overnights
    - Low voltage cut out device for Accessories must be accurately adjustable
    - Once the SOC is too low to crank your vehicle a jump start supply will have to be a monster as well - especially on a diesel - think cold mornings.
    - Have some backup plan...maybe a small cheap battery box with a charged 638L Dixon Deep cycle stashed away somewhere, holds charge for weeks
    One of those Romoss Li-ion jumpstarters would probably be enough, if I recall correctly they can give 400amps on crank, handy little devices.
    Last edited by Skylark; 2019/08/25 at 10:21 AM.

  7. #6
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    Default Re: Sidestep the dual battery system

    Henri, I'm also leaning your way. I have 3 of those exact batteries on my solar setup in my house, to just run a 12v circuit with lights in every room in the house. I seldom use eskom for lights in my house. Batteries were dumped by one of my clients 3 years ago. Some of them only gave me 1.2v when I got them, but I could rescue them, they do well on my solar.

    Anyhow, the other day it was time to start the Sani for the first time in 18 months. It's usual battery has died a long time ago. So I pulled one of these batteries off my solar setup and had to hook it up to my normal cabling with a set of jumpers and welding cable as the battery does not fit in the engine compartment. Now even with the additional cable I had to add, after a whole lot of turning on the starter to get some oil into the motor, and a few glo's. The cranking sounded so much better than the old 70Ah battery that was in there.

    I have been eyeing a spot under the back seat for a while now, to put two of those batteries, and remove my normal battery from the engine compartment, which seems to come to end of life due to heat, rather than normal use. At crawling speeds, I have measured in excess of 60DegC under the bonnet, and that does not work well for any battery.

    I was a First National Battery Dealer till about a year ago, and one of the guys there, was telling me how much he reckons they score because of the heat under the bonnet, and how much faster it stuffs up a battery.
    David/Hillbilly - 1997 SFA Nissan Sani 2,7 TD - 5" lift on 33" tires - Dual Transfer with 4.1 gears

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  9. #7
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    Default Re: Sidestep the dual battery system

    Quote Originally Posted by bfreesani View Post
    ................

    I was a First National Battery Dealer till about a year ago, and one of the guys there, was telling me how much he reckons they score because of the heat under the bonnet, and how much faster it stuffs up a battery.
    Well BMW and Audi has been putting the batteries in the boot for quite some time now.
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  11. #8
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    Default Re: Sidestep the dual battery system

    I run 2 in parallel, with a big isolation switch.
    One is for vehicle and the other for other stuff.
    Both are permanently linked to charging system and I only isolate when needed.

    They are under the passenger seat without any fancy electronic stuff.
    I bring the isolated battery back into the charging system only after about 8 minutes of driving.
    The only thing I do not know too much about is the effect when reconnecting the slightly discharged battery.

    In 20 years and 2 Defenders, I have only bought batteries twice.
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  12. #9
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    Default Re: Sidestep the dual battery system

    When your main battery dies for whatever reason. It is extremely useful to be able to switch in an isolated second battery to start the car. I had tracker units draining the battery, cells dying etc. Just flick the override switch and start the car.

    Just my 2c worth.

  13. #10
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    Default Re: Sidestep the dual battery system

    The big thing for me is the "redundancy" of the setup. Firstly, 120Ah is a damn side more than the normal 70Ah. Now put 2 of them back to back, and 240Ah will go a long way to keeping trackers and alarm systems running for weeks. I'm really keen to move my battery, and if I'm cutting the floor, and re-arranging stuff, I may as well see if two of them will fit into the space. Lucky my rig is an open canvas under the floor at the moment. Don't know where things like a fuel tank is even going to go for now.
    David/Hillbilly - 1997 SFA Nissan Sani 2,7 TD - 5" lift on 33" tires - Dual Transfer with 4.1 gears

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  14. #11
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    Default Re: Sidestep the dual battery system

    The concept of a single very large battery is good in principle provided nothing goes wrong. But from a practical perspective I reckon that is where the idea ends.

    For me when it comes to serious overlanding the cranking battery is a holy cow. It is exclusively reserved for starting the car. If for any reason it gets drained it is important to be able to tap into a secondary battery to get the car started (this is where the NL solonoid set up has the advantage). The solar set up can also be used as a cranking battery charger and is the ideal last resort back up.

    With all the long lasting USB 5v lithium rechargable battery lighting options now available and PWM solar controllers with 5v 2amp usb ports when it comes to charging cell phones ETC - the secondary battery charged via a combination of alternator when driving and solar when stationary can now realistically be reserved exclusively for running the 12v fridge. This also bearing mind that at many camp sites one can also run the fridge and charge all other batteries via a 220v supply.

    Sure the secondary battery works hard and a bog standard 90 or 105ah sealed lead acid deep cell as the secondary battery needs replacement every 4-5 years or so if you do a number of trips each year but that is just the way.

    Personally, just having one battery even if it is a big one would make me nervous out there.

  15. #12
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    Default Re: Sidestep the dual battery system

    I like it Henris and think you should pursue it.
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