Battery charger not coping





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  1. #1
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    Default Battery charger not coping

    I am looking for some advice and will appreciate if you can help, or point me in the right direction.

    I have a Hawkins 15 battery charger connected to a 105 A deep cycle battery. The battery is connected to a 1500w pure sinewave inverter and the inverter feeds equipment.

    When all is connected, and the power is on, in other words the battery is being charged and the inverter feeds 220v to my equipment, the battery loses power.

    To my inexperienced mind, either the charger or battery is not coping.

    Will it help if I connect another battery in parallel?

    Or is the problem somewhere else?

    I will appreciate your advice.
    Last edited by Stockman; 2015/05/25 at 04:26 PM.

  2. #2
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    Hi Jurgens57,

    What load do you have connected to the invertor?

    Say your battery is at 12V and your charger is running flat out at 15Amps, the most you can draw from the invertor is 180Watt without draining the battery!!!

    Anything more than 180W will drain the battery, even with the charger connected, sorry.


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  3. #3
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    Agree with Wetkit.
    Even a second battery will not make a difference.
    Your charger must be capable of supplying more than the equipment is taking.
    Eggie.

    "Do not go where the path may lead, go instead where there is no path and leave a trail."
    - Ralph Waldo Emerson.

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    Thanks Eggie and Wetkit.
    Seems like a bigger charger is the solution.
    I have a 10A Hawkins - will search for a bigger one - 20A.
    Can you recommend reputable suppliers?

  5. #5
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    Default

    Hawkins is a good choice as you probably know.
    Hawkins, Benton, Ctek, Victron...

    Speak to Eric Skeen and George Bosch on the forum or try Current Automation, Exsolar, Safari 4x4, ODW...
    Up to 25A or 30A. But brace yourself, it will not a cheap charger.

    If you could opt to have your inverter run off mains (or simply pass the mains through) when available, you would not need such a beefy charger. Should your current inverter not have a built-in charger and change-over option, it might be an idea to consider purchasing one that does. It is just so much more elegant and it requires very little or no attention from you in doing its thing. Choices...
    Eggie.

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  6. #6
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    Could I add some ideas :

    A 1500w inverter uses @ 12v -> 125A, its also not overly efficient so your loss might be 20%

    so 145A at 12V. The equation for W = V * A

    So.. your 105 AH battery will keep things running at full load for around 40mins or so.

    Your battery should be charged at less than C/3. This would be 105AH/3 < 35A.

    So.. To feed your equipment at full load you need around 145A, to charge the battery you need an additional say 30A. Thats a lot of current, which explains why the Hawkins isn't keeping up. 12V * 15A = 180W, energy requirements above this bleed off the battery.

    Now onto matters on the Hawkins, Mine is a 8A which seems to follow the exact opposite principles for battery charging. Initial charge voltage is 12.48 at low current, as the current drops the voltage goes up, eventually winding up at 15V and no amps.

    Batteries like a float voltage of 13.6V - 13.8V, 15V is a great way to fry it. Please check yours as this might be limited to mine only (hopefully)

    I hope this clears matters up a bit, if you have any questions please ask.
    Last edited by nitrious; 2015/05/25 at 07:09 PM.

  7. #7
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    Default

    Quote Originally Posted by Jurgens57 View Post
    I am looking for some advice and will appreciate if you can help, or point me in the right direction.

    I have a Hawkins 15 battery charger connected to a 105 A deep cycle battery. The battery is connected to a 1500w pure sinewave inverter and the inverter feeds equipment.

    When all is connected, and the power is on, in other words the battery is being charged and the inverter feeds 220v to my equipment, the battery loses power.

    To my inexperienced mind, either the charger or battery is not coping.

    Will it help if I connect another battery in parallel?

    Or is the problem somewhere else?

    I will appreciate your advice.
    What are you trying to do? Go from 220V AC to 12V DC - that back to 220V AC, with a 1500W load? That is double conversion...

    You should rather just bypass from 220V to the load.. that is how most UPS systems work.

    A 220V AC to 12V DC supply for 1500W (125 A) is a mean piece of equipment, and totally unnecessary?
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    Thank you Greg. How do you bypass the 220v?

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    If you want it to be automatic, you'll need a change-over relay (break-before-make) that switches based on the availability of the Eskom supply.

    I haven't bought one before - maybe ask Gerald_D what he uses?
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    Yeah - You need more than 125A charging current NOT to drain the battery.. (Can be done, I actually do have a 150A charger)

    BUT WHY What on earth are you trying to do?
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    Quote Originally Posted by RogueFrontier View Post
    Yeah - You need more than 125A charging current NOT to drain the battery.. (Can be done, I actually do have a 150A charger)

    BUT WHY What on earth are you trying to do?
    He was trying to build an Online (double conversion) UPS system - which does not used a change-over switch.
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  12. #12
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    the 1500w PSW inverter at full load is drawing 125amps out the battery.
    it will not last long with load like that.
    I suggest getting a second battery connected in parallel, that way at full taps the inverter is only drawing +-60 amps from each battery.
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  13. #13
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    Angry

    Hi Greg and RogueFrontier,
    I think I am making things complicated for myself.
    I have a Hawkins 15 Smart charger, putting out 10A. And NL battery pack with a 105A battery and a 1500w pure sine wave DC to AC inverter.
    Wanting to run UPS to computer, SMART TV, etc.
    I convected the charger to 220V, the charger to the battery, the battery to the inverter and a multiplug to the inverter.
    My problem is even when power is on, with battery charging, the battery gets drained.
    The equipment is using 900w.
    Looks like the missing part is the change over switch - if I understand you correct.
    Back to the drawing board.
    Thanks for advice guys - I appreciate it!

  14. #14
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    For sure... You have everything you need to charge/provide power, but it won't be seamless / automatic. The change-over relay could solve that.
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  15. #15
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    Thanks Greg. Just been to Voltex - no stock of automatic change-over switches. And when they have, cost of +- R1800.00. Seems a bit crazy!

  16. #16
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    Jurgens57, if you would like to run your set-up as an 24/7 UPS, you going to need a (900W/12V=75A) 75Amp at least!!!


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  17. #17
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    Something else to consider is that the number cycles a battery can do is directly related to how depleted you make it very time you use it.

    The multiple battery idea is a good one. 48V makes life a lot simpler, so 4x 105AH batteries with smart charger and whatever size inverter suits, will give a longer battery life and easier charging without crazy high amps needed.

    you could simply sell yours to help fund the new one.

  18. #18
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    I bought a cheap chinese 660W inverter as an emergency when this load shedding started just to keep the lights on. Needless to say it lasted one day before i got something better.

    I've since decided to make it into a battery charger, a 660W battery charger. Say it all at once, its just sounds crazy. Yet, even this would not be enough to help your situation.

    I'm adding a microprocessor plus extras to make it smart (hopefully), so far have 8 charging cycle modes, depending on battery conditions. Should this actually get somewhere and not blow up I'll post details of the 660W smart battery charger. Still sounds crazy tbh.

  19. #19
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    One thing to also consider - my Royal batteries suggest a charging current of 0.1C - that is 10A per battery.

    If you spec a charger to cope with the maximum current use (around 75-80A) (breaking even, not charging the battery during use after a power failure) plus say 20A to charge after a power failure, you're looking at say a 100A charger. If your battery is flat and you're NOT using any power through the inverter, all that is going to go into the batteries (and trust me, a flat battey will accept that), and that cannot be good. In the short term, no problem, but it will hurt the batteries over the long run.

    For such a high power use, I would seriously consider a 48V system. This cuts the current requirement down to a quarter of the 12V system.

    Hein
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