Alternator and a deep cycle battery





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  1. #1
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    Default Alternator and a deep cycle battery

    Hi Guys,
    I have a KZTE (2002) with what i assume is the stock standard 70amp/hr alternator. When i got the car there was a duel battery system installed with a deep cycle battery (95 amp/hr).
    If i have nothing plugged into the system it is fully charged and all seems well, but as soon as i try run a fridge it lasts about 2 days and then no matter how much driving i do, never seems to get above 20%.
    I have replaced the battery with a new deep cycle (95 amp/hr) but still the same story. I have now been told that the alternator is not strong enough to charge the battery and possibly need to upgrade it. I have also been told that a deep cycle battery was the wrong choice.
    SO, can a deep cycle battery work in a standard KZTE or will i have to make adjustments or is it possibly something else?
    Any help would be appreciated before i fix something that is not broken!
    Thanks
    Warren

    Toyota Hilux KZ-TE
    Goodies and space for more goodies

  2. #2
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    A deep cycle battery is EXACTLY what you need for a fridge. A normal car battery cannot take the hammering of frequent near-total discharges, it is meant for "floating" applications where the total charge rarely falls below 70%.

    Possible causes for the behaviour you describe are:

    • the alternator does not give the correct charging voltage - get a new alternator / have the alternator rebuilt / have the diode pack replaced;
    • there is an excessive voltage drop through the electronic controls of the dual battery system - shot thyristor(s) usually the problem;
    • too thin wires / earth strap loose or corroded or too small;
    • wires are too long;
    • loose earth connection / inadequate earthing point.


    Your voltage at the alternator should be 13.8 V or higher. At the battery you should get about 13V - there is an inevitable voltage drop through the electronics but it should not be more than 1V, typically only 0.5 V. I would suggest you take the whole thing to a REPUTABLE auto-electrician to check. Maybe they can fit new control circuitry, or only replace a thyristor. The 75A alternator per se is big enough to charge both batteries - although it will take longer than a bigger alternator.

    In my very old 1985 110, a previous owner had installed an electronic control for the dual batteries, and I had the same problems. I eventually had the electronics ripped out and installed manual switches (i.e zero voltage drop!) with thicker wires. The system then worked perfectly, with me in total control. The only (VERY BIG) caveat is that alternators must not run on an open circuit - surefire way of burning the armature and/or frying the diode pack. So one must always ensure that the alternator is charging something.
    Dries Venter

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  3. #3
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    Default Deep cycle battery

    National Luna split charging manual states that a deep cycle battery can take up to 24 hours to fully charge depending on its dischage state, and this is the problem, because a deep freeze/fridge running overnight will drain the battery too far to be recharged fully during even 8 hours of driving the next day, so you have to switch it off anyhow at night. Ten grand later. Now I pack a 3 way fridge as well to keep my critical stuff like beer and mom;s goodies cold and use the compressor fridge for non critical things, (meat is cheaper and better in Botswana and Namibia anyway) because if you are standing for more than 1 day at a camp, you are in trouble with a compressor fridge. A lead acid battery appears to be a better choice as well.

  4. #4
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    Thanks guys for the info, i am going to get the wires checked and most probably replaced. Thanks for the info Dries.

    Not to argue coz i dont own my own fridge, but everyone i speak too seems to be able to run a fridge (Engle 40L - 3.5amp) for up to 4 days, min 48hr. So if i am at absoloutly most running it for 12 hours then surley i am not draining the battery to a state in which it cannot charge? Basically it is not performing to the standard of all the other guys i speak to?

    Thanks Again

    Toyota Hilux KZ-TE
    Goodies and space for more goodies

  5. #5
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    That is why I spent R5,000 to install a decent battery maintanace system into the car.

    I am happy so far.

    I installed both the Voltage regulator as well as the Bi-Isolator. With that I also added a 220v charger that I plug in when I get to a camping site.

    http://www.planmypower.co.za/4x4_acc...ATOR_REGULATOR
    LC 78 Troopie 1HD-FTE
    Uniglide
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  6. #6
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    Well, i decided to rip out the old system and found they had used 3 different size wires (some thin). Also the circuit was earthed onto the back bumper! So i have taken it all out and redone the system with 16mm. So hopefully it is now sorted. Good excuse to go on a trip to test!
    Thanks for the input.

    Toyota Hilux KZ-TE
    Goodies and space for more goodies

  7. #7
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    Warren on the topic of the "run time" - 5 A x 12 hours = 60 A.h. This leaves about 40 % of your deep cycle battery.

    BUT ht ecompressor does not run all the time. The thermostat switches it on as needed only. Now if the goodies are already frozen and you dont open the lid frequently you will get a lot more run time out of the deep cycle battery.

    Yet, as was mentioned previously, it takes LONG to then charge up the battery again.

  8. #8
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    Warren

    I hope your system works better after you have redone all the cables and make sure of a good earth point.

    But I have to agree with Henris about the "decent battery maintenance system", as there is no or very little alternators that will or can charge a deep cycle battery to a full state.

    The reason: Alternators are designed to charge lead acid batteries and the chemical construction of a deep cycle battery requires a higher charge voltage than a lead acid battery.

    To charge a deep cycle battery properly you need at least 14.8v on the terminals and a lead acid battery at least 13.8v

    There is a new "DC to DC Booster Charger" on the market that will solve Deep Cycle battery charging problems. The input for the booster charger is 8 - 16v and the charger will charge the Deep Cycle battery with a 3 stage charging cycle.

    I make use of booster charger in a off road trailer to charge my Deep Cycle battery.

    Best Regards

    Johann Prinsloo
    082 903 9971

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