Discovery3 twin battery installation - second battery fault





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  1. #1
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    Default Discovery3 twin battery installation - second battery fault

    Hi there

    I have a professionally fitted dual battery system fitted to my Disco3. This was installed several years ago for an overland trip - it worked great for that purpose.

    I want to know whether I can simply disconnect the second battery from the system whilst in town. The problem that I find is that the second battery is failing since its not really being utilised in town conditions - nothing is attached.

    I've now had 2 batteries die on me completely. They will no longer hold a charge - and this causes the main battery to go flat because the system keeps trying to charge the second battery (which won't take a charge).

    During lockdown, I've disconnected both batteries to be charged.
    - The main cranking battery was a little low, but picks up its charge and keeps it fine from a normal mains charger (and maintenance charger). Testing the battery, its good for cranking, saving etc.
    - The second (deep cycle) battery is flat, and will not take a charge any more. Its voltage is below 7V, and is therefore useless to man or machine!

    1. Can I simply disconnect the second battery from the dual battery system?
    2. Can I simply connect the two terminals of the second battery together - probably not a good idea, as it would be a direct short!)
    3. How do I disconnect the dual battery system, in favour of just the cranking battery?

    Deep cycle batteries are expensive - the current one is over R5000! Ouch!
    Can I get away with a smaller Deep Cycle Battery in its spot (perhaps one that is only R1500 or R2000?)

    Your expert advice is very welcome!

    Thanks

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    Default Re: Discovery3 twin battery installation - second battery fault

    I'm no expert like Eggie or Fluffy but would say you can disconnect in town. But with no load on the 2nd battery, won't cause it to die. Do NOT under no circumstances connect two battery cables together. R5000 for a derp cycle for your vehicle? I would say they saw you coming. I would easily use a 102Ah (1150K) Royal. It should be a lot cheaper. Something else caused your 2nd battery to die.
    Current - 2009 Mazda BT50 3.0CRDi 4x4 d/c
    Previous - 2005 Ranger 2.5 tdi 4x2 d/c (277 422km)

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    Default Re: Discovery3 twin battery installation - second battery fault

    Quote Originally Posted by Spiceman View Post
    I'm no expert like Eggie or Fluffy but would say you can disconnect in town. But with no load on the 2nd battery, won't cause it to die. Do NOT under no circumstances connect two battery cables together. R5000 for a derp cycle for your vehicle? I would say they saw you coming. I would easily use a 102Ah (1150K) Royal. It should be a lot cheaper. Something else caused your 2nd battery to die.
    The second battery is installed in the right hand side compartment where the hydraulic pipes etc go. This means a tight space for a small battery (55Ah). There is not much on the market in the dimensions needed - Optima Bluetop fits = R5500!

    I don't want to cause a fire or other problem by not having a battery connected!

    Thanks for the tips!

  4. #4
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    Default Re: Discovery3 twin battery installation - second battery fault

    You can tape the terminals with insulation tape.
    I get the issue wrt battery size. There my "expertise" fails me. Someone else with more knowledge should assist.
    Current - 2009 Mazda BT50 3.0CRDi 4x4 d/c
    Previous - 2005 Ranger 2.5 tdi 4x2 d/c (277 422km)

  5. #5
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    Default Re: Discovery3 twin battery installation - second battery fault

    I am no expert but something doesn't sound very kosher about your system.

    if you use a solenoid then the second battery should be isolated from the main battery and should not drain it when parked. The same goes for using a dc/dc charger unit, these would also isolate the second unit from draining the main battery. Without further information about the design/components of your system it will be hard to troubleshoot accordingly.

    If you need to bypass the second batter then start at the main battery terminals and remove the positive and negative power take of wires. Also test at the rear after removing with a meter if there is any power coming through to ensure it is the correct wires that were removed.

    I would remove the failed second battery from the current space as trying to charge a failed battery can cause numerous problems, among them being the battery exploding or catching fire or spilling battery acid in its enclosure.

    As an alternative for your small enclosure size i would rather look at a lithium battery and proper battery management system (BMS) to manage your needs.

    Snap some pics for us till one of the forum sparkys come along and help further...

    Quote Originally Posted by Photorer View Post
    Hi there

    I have a professionally fitted dual battery system fitted to my Disco3. This was installed several years ago for an overland trip - it worked great for that purpose.

    I want to know whether I can simply disconnect the second battery from the system whilst in town. The problem that I find is that the second battery is failing since its not really being utilised in town conditions - nothing is attached.

    I've now had 2 batteries die on me completely. They will no longer hold a charge - and this causes the main battery to go flat because the system keeps trying to charge the second battery (which won't take a charge).

    During lockdown, I've disconnected both batteries to be charged.
    - The main cranking battery was a little low, but picks up its charge and keeps it fine from a normal mains charger (and maintenance charger). Testing the battery, its good for cranking, saving etc.
    - The second (deep cycle) battery is flat, and will not take a charge any more. Its voltage is below 7V, and is therefore useless to man or machine!

    1. Can I simply disconnect the second battery from the dual battery system?
    2. Can I simply connect the two terminals of the second battery together - probably not a good idea, as it would be a direct short!)
    3. How do I disconnect the dual battery system, in favour of just the cranking battery?

    Deep cycle batteries are expensive - the current one is over R5000! Ouch!
    Can I get away with a smaller Deep Cycle Battery in its spot (perhaps one that is only R1500 or R2000?)

    Your expert advice is very welcome!

    Thanks
    Ford Ranger 3.2 Auto 4x4 XLT
    Paj DiD SWB Auto
    E92 335i 430kw at the wheels!
    VW G6 GTi DSG

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    Default Re: Discovery3 twin battery installation - second battery fault

    Quote Originally Posted by Photorer View Post
    The second battery is installed in the right hand side compartment where the hydraulic pipes etc go. This means a tight space for a small battery (55Ah). There is not much on the market in the dimensions needed - Optima Bluetop fits = R5500!

    I don't want to cause a fire or other problem by not having a battery connected!

    Thanks for the tips!
    Optima is a very good battery. How long have you been using that one?
    Current - 2009 Mazda BT50 3.0CRDi 4x4 d/c
    Previous - 2005 Ranger 2.5 tdi 4x2 d/c (277 422km)

  7. #7
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    Default Re: Discovery3 twin battery installation - second battery fault

    OK - here's my setup:
    1. Main Battery (currently on maintenance charge just for luck!)
    Click image for larger version. 

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    2. Second battery located in a tight bay on the right of the car:
    Click image for larger version. 

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    Not sure if you can see, but the top of the battery is bulging a little directly above the round parts of battery.


    3. This is the DC/DC charger unit that has been fitted:
    WRND Dual Battery Charger - Unit automatically charges from vehicle or solar as detected.
    Current Limited to 20A
    Aux Battery boosted to 14.4V
    Aux battery float at 13.7V
    Solar voltage range 12V to 40V max
    Car Battery discharge to 12.8V
    Extend discharge to 11.8V
    Click image for larger version. 

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    The Optima Battery has been in there for around 1 year.
    Last edited by Photorer; 2020/05/21 at 01:58 PM.

  8. #8
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    Default Re: Discovery3 twin battery installation - second battery fault

    I year for a proper battery such as Optima is not normal. Something went wrong somewhere. You should get at least 5 years service.
    Current - 2009 Mazda BT50 3.0CRDi 4x4 d/c
    Previous - 2005 Ranger 2.5 tdi 4x2 d/c (277 422km)

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    Default Re: Discovery3 twin battery installation - second battery fault

    Quote Originally Posted by Spiceman View Post
    I year for a proper battery such as Optima is not normal. Something went wrong somewhere. You should get at least 5 years service.
    Hence my question.........


  10. #10
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    Default Re: Discovery3 twin battery installation - second battery fault

    Quote Originally Posted by Spiceman View Post
    You can tape the terminals with insulation tape.
    I get the issue wrt battery size. There my "expertise" fails me. Someone else with more knowledge should assist.

    Simply removing the second battery and insulating the terminals sounds like a very easy solution.

    I just want to know that I will not be damaging the DC-DC charger, or possibly causing another problem.

    If I do that, I will also quickly find out what is not working, as that would have been attached to the second battery - a way of finding the fault!

  11. #11
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    Default Re: Discovery3 twin battery installation - second battery fault

    Something is seriously wrong.

    There had been discussions from members that had trouble with their WRND units, but generally it's accepted to be a robust no nonsense dc2dc charger which will isolate the two batteries when power is turned of.

    So, if this is not being done, then there is a problem with your WRND unit. If not, then you had been given a factory dud as far as the Optima battery is concerned.

    Seeing that the battery is stuffed now in any event, you can just disconnect the cabling coming from the unit and insulate them where they connect to the Optima while you have the charger removed and tested.
    Last edited by Die SwartKat; 2020/05/22 at 09:56 AM.
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    Default Re: Discovery3 twin battery installation - second battery fault

    Here is two of those discussions.

    https://www.4x4community.co.za/forum/showthread.php/329854-WRND-Electronics

    https://www.4x4community.co.za/forum/showthread.php/329855-WRND-DC-to-DC-Charger?highlight=
    Last edited by Die SwartKat; 2020/05/21 at 02:39 PM.
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  14. #13
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    Default Re: Discovery3 twin battery installation - second battery fault

    Quote Originally Posted by Die SwartKat View Post
    Something is seriously wrong.

    There had been discussions from members that had trouble with their WRND units, but generally it's accepted to be a robust no nonsense dc2dc charger which will isolate the two batteries when power is turned of.

    So, if this is not being done, then there is a problem with your WRND unit. If not, then you had been given a factory dud as far as the Optima battery is concerned.

    Seeing that the battery is stuffed no in any event, you can just disconnect the cabling coming from the unit and insulate them where they connect to the Optima while you have the charger removed and tested.

    This is the second attempt...... I firstly had a HCDC (?) unit fitted, that fried my second battery (previous installation). The DC-DC charger was swopped out for this one, and a "new" Optima battery installed. Its not been very long before the same problem arose.

    My primary battery is dead if I leave the car standing for more than a day. I've taken the opportunity of lockdown to source a solution........ last weekend I got a maintenance charger and battery tester, and found that the secondary battery is toast!

    If I can simply disconnect the secondary battery whilst still driving around to get things tested, that would be great! can you confirm that if I insulate the terminals this won't cause a problem.

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    Default Re: Discovery3 twin battery installation - second battery fault

    Quote Originally Posted by Photorer View Post
    This is the second attempt...... I firstly had a HCDC (?) unit fitted, that fried my second battery (previous installation). The DC-DC charger was swopped out for this one, and a "new" Optima battery installed. Its not been very long before the same problem arose.

    My primary battery is dead if I leave the car standing for more than a day. I've taken the opportunity of lockdown to source a solution........ last weekend I got a maintenance charger and battery tester, and found that the secondary battery is toast!

    If I can simply disconnect the secondary battery whilst still driving around to get things tested, that would be great! can you confirm that if I insulate the terminals this won't cause a problem.
    Yes confirmed.
    Nico Swart

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    ZS6NJS

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    Default Re: Discovery3 twin battery installation - second battery fault

    Based on your pictures you have already disconnected the positive on the 2nd battery. As is already indicated you just need to tape them closed to prevent a short. You can then drive like that. Always better to also disconnect the positive at source as indicated and tape up.

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