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  1. #41
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quote Originally Posted by Prof View Post
    PWM comes to mind
    to measure Ah capacity is in essence to measure the chemical surface area, for this the test is mainly DC or low frequency pulsed DC to allow the chemical reaction to proceed at its pace.
    here's a very brief write up:
    https://securepower.com/impedance-testing/

    there are AC tests but these are not strictly for Ah.

    issue with the Mecer type trolley is that the inverter rating far exceeds the sustained discharge capability of the lead acid battery ito its C rating. to prolong battery life only apply sustained loads to the inverter of about 0.15C of Ah capacity.

    for series-connected batteries (24V) there may also be the issue of progressive battery imbalance after several charge / discharge cycles. I stand to be corrected on this one ... is the Mercer charger 24V without knowing the charge state of each individual battery, ie. it is only concerned with 28V as the terminal voltage even if this means one battery is that 12V and the other at 16V.

  2. #42
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Some are 12 V some are 24V. Grannies typically have 12V one battery. Sometimes a second battery is added when the first is half gone. Very unpredictable what their kids are connecting for them when they visit from up-country once a year.

  3. #43
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Must say this thread again illustrates clearly that there is no 'flick a switch' solution.

    Or the cheapest option will work but not for the those who do not fully understand the ramifications.
    Thus a more expensive option is needed to put some 'padding' to the solution, and even that comes with some serious caveats.

    A minefield....truly.

    Then it seems some here are at cross purposes....one who is discussing a solution to measure batteries for the ones who do not understand the science, the other knowledgeable side wants to complicate the 'simple' issue with science which will never be properly understood by those that use the solution to keep the lights etc going for a short period.

    Me, having a scientific background, can tell by the seat of my pants if a battery is on the way out
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  5. #44
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Digital panel meter connected to battery and Kill O Watt meter plugged into inverter 3pin outlet socket. This way you take inverter efficiency into account as well as our friend Peukert. You can also accelerate the test by plugging a higher consumption appliance e.g. toaster etc.

  6. #45
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quote Originally Posted by RussellF View Post
    to measure Ah capacity is in essence to measure the chemical surface area, for this the test is mainly DC or low frequency pulsed DC to allow the chemical reaction to proceed at its pace.
    here's a very brief write up:
    https://securepower.com/impedance-testing/

    there are AC tests but these are not strictly for Ah.

    issue with the Mecer type trolley is that the inverter rating far exceeds the sustained discharge capability of the lead acid battery ito its C rating. to prolong battery life only apply sustained loads to the inverter of about 0.15C of Ah capacity.

    for series-connected batteries (24V) there may also be the issue of progressive battery imbalance after several charge / discharge cycles. I stand to be corrected on this one ... is the Mercer charger 24V without knowing the charge state of each individual battery, ie. it is only concerned with 28V as the terminal voltage even if this means one battery is that 12V and the other at 16V.
    The batteries should stay balanced, just like the cells in the battery do. Remember a 12V battery is 6 cells in series and a 24V battery is just the same cells but 12 of them in series. If they are the same battery type and age, they should stay balanced to within acceptable tolerance.

    12V and 16V is an almost impossible situation.
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  7. #46
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    January 2021 we bought a Mecer 2400 trolley from Geewiz. The one with the 2 x AGM batteries. It ran our Server room beautifully for over 6 hours easily. (Load according to the unit 25%). Did have two or three incidents that took them down to dead (fried substations etc).

    Found out a bit more than a month ago that the ups cannot run the server room for more than 45min. Accepted batteries as fried. Replaced and again up to former glory, but this time around we turn the UPS off when leaving work. (This will in future create problems for those wanting access to server after hours, during loadshedding) (We do run a genny at work that powers the server room when we are at office)

    Anyway, took the two "fried" batteries home and put the one on a smart charger for a few days. Then used it during loadshedding to power a TV with a pure-sinwave inverter. Lasts about an hour before inverter starts complaining. I have to accept that they are indeed fried at this point. My 8 year old Exide semi deep cycle lasts two hours running the same TV....

    So, with a stress test, figured out that they are fried... Problem is the wheels needs to keep turning at work so could only do the stress test after replacing. If they were fine, I would have left them topped up on the smart charger, as backup should the new ones die...
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  9. #47
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    ito production spread, cells of the same batch, exposed to similar environmental conditions would most closely be matched ito their performance & characteristics.

    the ideal is to manage each cell individually as per BMS or individual charger. individual lead-acid cells are available but not generally so and come at a cost / volume premium.

    next best ito lead-acid is a battery since these cells by and large were precisely of the same batch and exposed for the most part to the same environmental conditions.

    one then has to manage each 12V battery ito itself. most common 24V chargers charging two 12V batteries have no idea the state of charge of the individual battery - it looks only at the 28V terminal voltage.

    by its nature, the Ah of each battery is different to any other, charging the string only by terminal voltage would, after several charge/discharge cycles, result in varying battery voltage with some batteries ultimately being "overcharged" and others "undercharged".

    one could use the analogy of vertically stacked water buckets linked in series by pipes near the base of each. then filling the stack only by pouring water into the topmost bucket then emptying the stack by discharging the bottom bucket.

    because the buckets are not precisely identical ito volume, after several fill / discharge cycles the water level in each bucket would vary relative to other buckets in the stack.

    in this example bucket-volume equates to Ah, water-level equates to voltage.
    Last edited by RussellF; 2022/07/11 at 10:32 AM.

  10. #48
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quite a lot of loadshedding threads on the go - most very interesting and quite complex - how to parallel inverters, which inverter is best, building your own LifePo4 battery, series or parallel panels, sizing your system.

    Who would have thought the most complex, unsolved discussion from the bunch is how to know your battery level?

    Iím being a bit facetious of course. This is an interesting discussion too. One of those simple things that maybe isnít so simple.

    Notice how I said ďbattery levelĒ. To be honest, Iím not quite sure - even after reading this entire discussion - I know (for sure), what State of Charge really means and what state of health really means and what all the different measures around them are, never mind methods to take said measures (which seems to be a large part of this discussion).


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  11. #49
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quite a lot of loadshedding threads on the go - most very interesting and quite complex - how to parallel inverters, which inverter is best, building your own LifePo4 battery, series or parallel panels, sizing your system.

    Who would have thought the most complex, unsolved discussion from the bunch is how to know your battery level?

    Iím being a bit facetious of course. This is an interesting discussion too. One of those simple things that maybe isnít so simple.

    Notice how I said ďbattery levelĒ. To be honest, Iím not quite sure - even after reading this entire discussion - I know (for sure), what State of Charge really means and what state of health really means and what all the different measures around them are, never mind methods to take said measures (which seems to be a large part of this discussion).

    Thanks


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  12. #50
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quote Originally Posted by Tsotsi View Post
    Is it wise to set the Mecer to 20A charge rate during heavy load shedding?
    Mecer 1200VA currently set at 10A with 1x 100ah deep cycle batt.

    Think I have the same setup for my TV and wifi, well mostly wifi.

    Probably similar battery too. One 100/105 ah semi deep cycle. Deltec or ennertec or something.

    So far, Iíve kept mine on 10A. Itís a switch right? So you get either 10A or 20A. Iím trying to stick to 10A.

    If the LCD panel reaches 50% and further downtime is expected, Iíll switch to 20A and maybe keep TV off so it recharges up high before next downtime hits.

    Had mine for a few months. So far so good. Not pressed too hard with just the wifi though


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  13. #51
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Rule of thumbs from Lead-acid days:
    Weekend battery: Recharge at 8% of battery ah rating leisurely over a week. Must be fully charge once a week.
    Daily usage: Recharge at 10% of battery ah rating.
    Frequent LS: Recharge at 15% of battery ah rating. 20% if you are forced to.

    Lifepo4: Read the manufactures specs, or warranty can be affected.


    Must say, since I could afford the DIY Lifepo4 bank, rated at 1C charge or 100% of ah, I have not looked back as recharging is not an issue anymore ito time it takes.

    But bugger me!!! ... it cost a damn lot when Cpt has bad weather for days on end, and panels are just sitting there giving a red roof a tint of black colour. (faceplam)
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  15. #52
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quote Originally Posted by pantoffel View Post
    One of those simple things that maybe isnít so simple.
    So, to complicate your life further, with lead acid batteries there is this thing called Peukert's law ... in short:
    Manufacturers specify the capacity of a battery at a specified discharge rate. For example, a battery might be rated at 100ah when discharged at a rate that will fully discharge the battery in 20 hours (at 5 amperes for this example). If discharged at a faster rate the delivered capacity is less. Peukert's law describes a power relationship between the discharge current (normalized to some base rated current) and delivered capacity (normalized to the rated capacity) over some specified range of discharge currents.

    So you say bugger this, too complicated, I'm going with lithium batteries where Peukert's law does not apply.

    But, that is not the end of the story ...

    Lithium batteries work best on a very flat curve like 3.2v - 3.45v for optimal lifetime use, like 3/4/6k cycle life, right?
    Hold on, no SOC, SOC is volts based(?) you may ask.

    Yeah, it is like the HD explanation you gave ... man, I laughed at that.

    You can count the coulombs in/out of the battery with a damn good shunt but it never ties up with the BMS (with a shunt) state of charge because the BMS factors the cells voltages in too.
    Volts are very NB for lithium batteries, it hits a certain volt and bam, SOC is 100%.

    Confused? Ok, to make sense of it all, it is like your vehicles fuel gauge. Unless you have run out of fuel and know in your gut where the limits are, you won't know how accurate the meter is, so you drive it within parameters you set like quarter tank, or light coems on, you fill up.

    Or the computer says X km still to drive on the tank ... depends on how you drive and if it got the calcs right.

    See, as simple as that.



    Ok, serious now, it is not THAT complicated. Depends on what you want to know and how you want to get the info ... IF it is important to you.
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  17. #53
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    A couple of random points . . . . .

    State of health SOH is a completely different thing to SOC. (SOH is my term, there is probably a more general term in use, but can't think of it at 5am)

    If you know a battery's history, then judging the SOH is much easier. Battery sellers are skewed to telling you your old battery is shot - unless it is still in warranty in which case it still is fine and they send you home with it.

    My load test of 17 Amp for 2 hours before 11.0 V is reached on a nominal 100 Ah battery works okay for deciding SOH. But I wonder if there is standard recognised test used in the battery industry? A Hawkins battery tester, or similar that applies 100 A load for a few seconds tells me the battery is okay to start a truck, but my test shows the battery won't deep cycle on an inverter. Am I looking for a "deep cycle tester"? Not looking for fancy lab equipment- something practical and affordable.

    Right now I am stumped in finding a simple hour meter for this test. Must run between 11 and 16 V and be resettable. Surprisingly very hard to find.

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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quote Originally Posted by Jonatan View Post

    Right now I am stumped in finding a simple hour meter for this test. Must run between 11 and 16 V and be resettable. Surprisingly very hard to find.
    Perhaps you can read the complete test of checking battery SG to find if any cell was overcharged. Also to ensure battery is charged prior to load test. Test of high current to ensure battery does not drop to under 9V etc. Full details on how a Probe battery should be tested and under what readings a claim should be rejected on their Web page.

    Stumped you never tried to Google to see a wide range of hour meters. This one can run from below 10V up to over 60V. Not sure about resetting.
    Attached Images Attached Images  
    Last edited by ekkekan; 2022/07/13 at 06:09 AM.

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  20. #55
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quote Originally Posted by ekkekan View Post
    Stumped you never tried to Google to see a wide range of hour meters. This one can run from below 10V up to over 60V. Not sure about resetting.
    Must be resettable

  21. #56
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    I covered some of this a year ago in this thread: https://www.4x4community.co.za/forum...esults-for-UPS

    The only progress I seem to have made since then is to automate the test procedure to some extent.

    And I have acquired a clamp meter since then, so I can confirm that the 4 headlight bulbs draw over 17 Amp

    Click image for larger version. 

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  22. #57
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    The Probe warranty conditions. This particular paragraph seems a bit extreme?

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  23. #58
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    Quote Originally Posted by Jonatan View Post
    Hawkins battery tester ...
    I use a Hawkins tester after I burnt the shiite out of my finger testing a battery that was faulty. I can say for sure, if it does not pass the Hawkins test, it is on its way out or shot. Takes seconds.

    Quote Originally Posted by Jonatan View Post
    The Probe warranty conditions. This particular paragraph seems a bit extreme?

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    Jip, correct.

    I used to use name brands like 12v Excide/Royal/Delta till I got gatvol as they "never lasted" in UPS use.

    Learnt three things:
    1) that the SOC/DOD is rather damn important when checking the claimed cycle life - as Probe is now clearly displaying.
    2) that temp kills batteries, even lithium, FAST
    3) that batts can also die of old age, being a chemical reaction, so use them daily

    So I saved some monies and bought tried and tested forklift/Golfcart batteries, 6v Trojan T105RE. At the time, just WOW.

    Claimed cycle life of T105RE's are 4000 cycles at a max of DOD (Depth of Discharge) of 20% / SOC (State of Charge) of 80%.

    Or +-750 cycles at 100% DOD/SOC of 0, see below.
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  25. #59
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    Default Re: Testing the typical battery in a "Mecer trolley"?

    I have come to realise that the biggest battery killer in these DIY "Mecer" type home setups is simply under-sized or overloaded batteries. The 12V Mecers typically only have 1 battery and people are draining them to flat battery alarm twice a day. People need to learn to use the batteries down to 12V only . . . . if they can't manage on that, use two batteries. This is more important than looking for the best brand or type of battery.

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