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  1. #1
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    Default Monitoring battery state of discharge / charge

    So now again I am going to ask what are probably a couple of stupid questions.
    Maybe this will help other elektrickery ignoramuses such as myself in the process.
    1
    What is the best (economical but reasonably accurate) way to monitor your battery status?
    I am speaking of aux. batteries for camping, overlanding or as backup power source during Eksdom outages.

    Do I need a VOLT meter, an AMP meter or both to properly monitor "maintenance free" battery status ?
    If so, either way, where and how do they need to be connected?

    This would be in the context of batteries being charged by mains 220 - 240 V A/C supply via a charger most of the time, supplemented by a small 80 W or so solar panel via a solar controller during daylight hours - sometimes simultaneously and in the case of a mobile set-up, while driving - the alternator charging via solenoid or other means.
    In dark hours could the mains charger be left on when power returns even if the inverter is still drawing power from the batteries?

    So quite a few different connections involved.
    Add multiple batteries linked together to provide 12 V DC to a small inverter of (say) 1 000 W or maybe a bit more - but not hugely bigger.

    Trying to keep costs down but effective and to provide a reasonably accurate indication for detecting SOD at any time, (even when busy charging or under load?)

    So a few consideration there.

    Apologies for keeping on harping on this subject but these things are beyond my ken and I need to protect my new deep cycle batteries to the best of my ability for extended life.
    (Batteries - not necessarily mine ! Although that would be a plus.)

    OK - Again: Wait for it .................................................. .............................

    Eish.

    Apologies for that overworked "Eish".
    Last edited by Peter1949; 2021/04/12 at 02:14 PM. Reason: Eish apology
    Peter Hutchison
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  2. #2
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    Default Re: Monitoring battery state of discharge / charge

    I suppose this if for your removable camp setup which will do duty in the house as well as per your other thread?

    If you want to monitor state of charge and discharge accurately, then you need something with a shunt, which is designed for battery monitoring.

    A volt/amp meter will only give you an indication of what the battery's level are and even though these have shunts in them, they are not accurate.

    In my vehicle setup I have gone the v/a meter route (x2) which more than sufficient meets my needs. It works on the principle of being able to monitor simultaneously amps drawn and amps supplied to the battery from alternator, AC or solar.

    As long as he former is smaller than the latter, I know I'm good. To get an idea of state of charge, all loads must be disconnected and battery left for an hour or so.

    But you'll probably need something smarter.

    Saw a reasonably priced battery monitor on one of the threads a while ago which should suit your needs.

    On my home setup I have a Victron BMV712 which is silly expensive, but worth every penny to me to protect 4 very expensive batteries.

    There is cheaper stuff that works just as well though.

    I'll find some pics.
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  4. #3
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    Default Re: Monitoring battery state of discharge / charge

    Nico Swart

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  6. #4
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    Default Re: Monitoring battery state of discharge / charge

    This is what I have done in the vehicle. And this was cheap.
    Attached Images Attached Images  
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  8. #5
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    Default Re: Monitoring battery state of discharge / charge

    I think the most easy set-up on the 12V side would be the use of a dual battery monitoring system like National Luna in connection with a CTek D250 DC-DC charger.

    The Ctek has apart from the alternator terminal an extra solar port and includes a controller and the battery monitor gives you LED reading for the battery status.
    You just add the inverter of your choice onto the battery connection.
    It works for mobile as well as stationary set-up, best to install the whole into a ammo box and move it where you use it.

    If you use it on 220V AC then connect an ordinary battery charger (Ctek has a variety of models working just fine with standardised plugs or battery clamps.
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  10. #6
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    Default Re: Monitoring battery state of discharge / charge

    It is now in process of conversion to a house based - non portable, small backup system - so no more alternator charging unless I were to run the vehicle motor and manually connect which I think would be highly inefficient.
    Could you send me a link to your cheaper, stuff that works ?

    Your comment much appreciated.
    Thank you.

    Quote Originally Posted by Die SwartKat View Post
    I suppose this if for your removable camp setup which will do duty in the house as well as per your other thread?

    If you want to monitor state of charge and discharge accurately, then you need something with a shunt, which is designed for battery monitoring.

    A volt/amp meter will only give you an indication of what the battery's level are and even though these have shunts in them, they are not accurate.

    In my vehicle setup I have gone the v/a meter route (x2) which more than sufficient meets my needs. It works on the principle of being able to monitor simultaneously amps drawn and amps supplied to the battery from alternator, AC or solar.

    As long as he former is smaller than the latter, I know I'm good. To get an idea of state of charge, all loads must be disconnected and battery left for an hour or so.

    But you'll probably need something smarter.

    Saw a reasonably priced battery monitor on one of the threads a while ago which should suit your needs.

    On my home setup I have a Victron BMV712 which is silly expensive, but worth every penny to me to protect 4 very expensive batteries.

    There is cheaper stuff that works just as well though.

    I'll find some pics.
    Peter Hutchison
    Answering the call of the wild is just so much beter than answering the telephone.
    [B][SIZE=2][FONT=Calibri][SIZE=2][B]ISUZU KB 280 DT LE
    Modified Glider Hunter trailer fitted with RTT.
    Platkar = Chevy Spark 1.2

  11. #7
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    Default Re: Monitoring battery state of discharge / charge

    Quote Originally Posted by Die SwartKat View Post
    This is what I have done in the vehicle. And this was cheap.
    Neat setup, where did you get them?
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  12. #8
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    Default Re: Monitoring battery state of discharge / charge

    Quote Originally Posted by ChrisH View Post
    Neat setup, where did you get them?
    Bought them from 4x4 Direct. R196.00 per meter. Search (4x4direct.co.za)
    Nico Swart

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  13. #9
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    Default Re: Monitoring battery state of discharge / charge

    I have also heard many times on this forum that these also work very well, R400 also at 4x4 Direct. Connection much easier.
    Nico Swart

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  15. #10
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    Default Re: Monitoring battery state of discharge / charge

    1
    To monitor Lead Acid:
    All you need is a cheap volt meter attached to the terminals, the average accuracy isnt an issue due to LA step voltage curve. A decent voltage to soc graph during charge (chargers typical rate) and discharge (typical loads like fridges etc) is all you need, problem is these graphs are hard to come by and can be quite unreliable so to get the numbers yourself requires a few days of cycling and testing counting AHs. Also a basic amp meter at the neg terminal to tell you when the battery is really fully charged or not. LA is fully charged when at the correct voltage the amps flowing into the battery reaches down really low.These tools are cheap but can start to get expensive if you want remote long fistance viewing.


    Lifepo4:
    Same exact as above except the voltage curve is flatter and requires a volt meter that reads 13.25 instead of just 13.2
    You also need to calibrate your voltage gear against a good DMM, like 13.25 on a cheap volt meter might equal 13.28 on the DMM.

    Basically you have to learn how to properley read the voltages and end amps to get a good ballpark idea. The voltages during charge are the hardest to learn especially if the charge rate is small.

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  17. #11
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    Default Re: Monitoring battery state of discharge / charge

    Quote Originally Posted by Die SwartKat View Post
    On my home setup I have a Victron BMV712 which is silly expensive, but worth every penny to me to protect 4 very expensive batteries.
    Stop all the messing about. Just do this.
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  19. #12
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    Default Re: Monitoring battery state of discharge / charge

    A wee bit cheaper from Banggood than the Victron BMV:
    Attached Images Attached Images
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