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Thread: Battery capacity tester for 12v SLA in backup power supply?

  1. #1

    Default Battery capacity tester for 12v SLA in backup power supply?

    Had a momentary power glitch, as we do, & my old APC backup power supply just started beeping w/ error F-07, which is "temperature."

    Unhooked everything & plugged it in, which cleared the code.
    Seems to be indicating a discharged battery so I plugged it in.
    After a while, still 0 capacity.
    One of the two batteries (in series) is warmer than the other.
    Want to confirm its the battery & not the unit, before buying a new battery or two.
    They are 7.2 Ah. Peeled off the APC label & the supplier is Kung Long.

    EDIT: they have some kind of battery management software, would that show a bad battery?
    www.apc.com/shop/us/en/products/PowerChute-Personal-Edition-v3-1/P-SFPCPE31

    No idea how to hook the power supply to my computer for data transfer.
    Last edited by lumen aeternum; 06-07-2021 at 06:18 PM.

  2. #2
    *Flashaholic* idleprocess's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    UPSs are notorious for their sloppy charging circuits. Conveniently, the OEMs make a tidy profit selling replacement batteries (or battery cartridges ala APC).

    Odds are you have a dead battery. If you have a multimeter, try taking a reading on the battery that was getting hot. I imagine it's well below the nominal ~14.4V it should see at top charge.

    The 7.2Ah SLA is one of the most common sizes out there. Plenty of other suppliers than whoever APC is badge-engineering. I've hade decent luck with Powersonic. You'll want to verify the terminal style and size first - the smaller F1 terminals will work mechanically for a F2 connector but won't make the most reliable contact; the other way around won't work.

    Every APC 'cartridge' I've come across can be disassembled and the internal components reused with new batteries - just make note of how the connections are made when disassembling the original, replicate when re-assembling, and use packing tape or similar if necessary to re-constitute the 'cartridge'.
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  3. #3

    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    The error code says to contact them, so it might be the circuit board itself that has gone bad.

    I guess I could hook up the battery to my car battery charger?

  4. #4

    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    And if one battery is bad, I suppose I may as well replace both...the old battery might impair charging the new?

  5. #5
    *Flashaholic* turbodog's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Batteries age together. Unless the pack is new (<6 mo old) I would replace both. That said... I've never seen the error code you describe... unit may have failed??? You could unplug from AC power, pull batteries, leave off, and then re-energize and see what happens.

    I added a small ac-power muffin fan to the side of one of my 'problem child' units that was in a warm area. Seems to have helped. Attached it with double sided tape.
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    Flashaholic* DIWdiver's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Also, just because the batteries are bad doesn't mean the rest of the unit is okay. If the charger failed, it could damage the batteries.

    If one is getting warm I wonder if the other is shorted, which would mean the 24V charger is attempting to charge a 12V battery.

  7. #7
    Flashaholic* snakebite's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Quote Originally Posted by DIWdiver View Post
    Also, just because the batteries are bad doesn't mean the rest of the unit is okay. If the charger failed, it could damage the batteries.

    If one is getting warm I wonder if the other is shorted, which would mean the 24V charger is attempting to charge a 12V battery.
    bingo!
    those plastic apc units kill their cheap capacitors at about the same rate they destroy batteries!

  8. #8

    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Quote Originally Posted by idleprocess View Post
    The 7.2Ah SLA is one of the most common sizes out there. Plenty of other suppliers than whoever APC is badge-engineering. I've hade decent luck with Powersonic. You'll want to verify the terminal style and size first - the smaller F1 terminals will work mechanically for a F2 connector but won't make the most reliable contact; the other way around won't work.
    what's the size of F1 vs F2?
    EDIT found it
    F2 is 0.250 INCH
    F1 is 0.187 INCH
    F STANDS FOR FASTON TAB

    I see so many reviews saying 3rd party batteries are junk...

    So the OEM supplied batteries made by Kung Long in Vietnam have F2.
    I suppose all APC units will have F2 to draw the current without heating up.

    searching for Kung Long yields only "replacement" brands having F1
    except ApexBattery has a confusing spec...
    also, they seem to be rounding up the 7.2Ah to 8. Unless their battery in the same size package can have more Amps?
    page: /kung-long-wp72-12-f2-battery.html

    Manufacturer Apex Battery
    UPC 683405590910
    Model Number APX1280F2
    Made In China
    Terminals F2 (0.25" Faston Tab)
    Brand Kung Long Battery <<== MUST MEAN WHAT THEY INTEND IT TO REPLACE?
    apex_sku APX1280F2

    They charge $13.50 each & postage, versus the APC replacement pack APCRBC123 which is $52 online.
    Last edited by lumen aeternum; 06-12-2021 at 11:43 AM.

  9. #9
    Flashaholic* DIWdiver's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    There are plenty of good battery makers around. PowerSonic is certainly one of them. There are also a few garbage vendors around, so you want to be a bit careful. If you go to a reputable distributor, you probably can't stray too far from 'you get what you pay for'. OTOH, if you buy from some unknown vendor, 'caveat emptor'.

    I would never buy the massively overpriced OEM batteries if there was any reasonable choice.

    I've never heard of Kung Long Battery, but that doesn't mean they aren't a good manufacturer. If you have solid evidence that they manufacture the OEM batteries, then you probably can't go too far wrong buying from them, especially if they seem to be a good price.

    It is possible to pack slightly higher capacity in a certain size than is typical of the market. However, it's likely you'll pay a steep price for this, either when you buy it today, or when you replace it sooner than you should need to. I'm no expert in this, so maybe others will chime in.

  10. #10
    *Flashaholic* Lynx_Arc's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    I bought some batteries once when 7Ah SLAs were going for $12 or so shipped if you bought enough stuff. I ordered several batteries including one for a neighbor for his lawnmower. My lawnmower battery died about 8 years ago and I'm not spending $25 to replace it because my mower starts on the first or second pull as it is. I've found the life time of SLAs not worth the hassle of investing in them unless I abolutely need to since the prices doubled years ago I used to use SLAs to power things even have a 6V spring top SLA still not sure it is any good after sitting 10 years on a shelf unattended but at one time I used it in a power outage and to power a battery soldering iron.
    I have some old corded headlamps that use a small 6V SLA also they were halogen and krypton high quality lamps I've used one at a time but the bulk of an SLA on your belt and the large headlamp also.
    I did find some inexpensive ones at Academy sports about $22 for a 12v 7Ah SLA not a bad price and after you try to buy them online and have them shipped you aren't going to save much for your hassle IMO.
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  11. #11

    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Found a pair of Powersonic PS 1270 F2 for under $30 so I'll give those a try.
    Only 7.0 Ah instead of OEM 7.2 but its not meant for long operation, only the intermittant drops.
    I just want them to last a long time.
    I wonder if the version mean for deep cycle would last longer in my application? PDC-1275.

  12. #12
    Flashaholic* DIWdiver's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Deep cycle will last longer if you discharge them most of the way each time before recharging them. This is pretty hard on regular SLA batteries, and would cause them to fail even more quickly than they would otherwise.

    So on an electric lawn mower, where you use most of the capacity each time you mow, deep cycle would be good. But on a tractor where you only use it to start the engine and the tractor immediately recharges it, deep cycle battery would not have an advantage.

  13. #13
    *Flashaholic* idleprocess's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Quote Originally Posted by Lynx_Arc View Post
    I've found the life time of SLAs not worth the hassle of investing in them unless I abolutely need to
    They're a subscription plan item at this point: you value the uptime so you replace them on a schedule. Working from home, I need the uptime since there's no office to return to so I'll be blowing 3 figures money every other year keeping the UPS fleet afloat. Unless some of these "portable power station" products start to demonstrate real utility as a UPS and have the longevity to justify their prices.
    I apologize that this letter is so long; I did not have time to write a short letter

  14. #14
    Flashaholic* snakebite's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    the best battery for a ups is the one with the lowest internal resistance.
    figure 10a per 1a on the output.
    and thats being generous about the efficiency.
    thats for a 12v unit.
    a 24v halves the battery current.
    deep cycle does not matter. .
    low ir and float life does.they will not last long enough to get that many deep cycles.
    and deep cycles are optimised for cycling not high rate/low ir.
    most batteries on the market that fit these ups units do not have a datasheet anyway.
    your powersonics do.

  15. #15

    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Quote Originally Posted by idleprocess View Post
    They're a subscription plan item at this point: you value the uptime so you replace them on a schedule. Working from home, I need the uptime since there's no office to return to so I'll be blowing 3 figures money every other year keeping the UPS fleet afloat. Unless some of these "portable power station" products start to demonstrate real utility as a UPS and have the longevity to justify their prices.
    If you need that much backup power, why not use industrial 12v batteries & a big inverter?

  16. #16
    *Flashaholic* idleprocess's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Quote Originally Posted by lumen aeternum View Post
    If you need that much backup power, why not use industrial 12v batteries & a big inverter?
    I don't need a great deal of backup power - just in multiple locations, and they must be UPSs. Suspect that the greater longevity of such a setup would be offset by the greater upfront pricing. Besides, for longer outages I'll soon have a generator inlet into the building wiring.
    I apologize that this letter is so long; I did not have time to write a short letter

  17. #17
    Flashaholic* orbital's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Quote Originally Posted by lumen aeternum View Post
    If you need that much backup power, why not use industrial 12v batteries & a big inverter?
    +

    If you do that, I'd more than suggest using straightforward lead acid deep cells.
    Any trickle charger setup ruins AGM.

    Currently in the process of doing 2x100W solar panels in series, connected to a Samlex PST-1000-24.
    I had the 24V inverter setup for a few years, so it's only logical putting it to better use.

  18. #18
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    A UPS I tried to service a number of years ago had one of two 7Ah SLAs swollen, no doubt from overcharging, jammed in and quite hard to remove. I don't necessarily blame the batteries. Fault was narrowed down but in the end it was`not worth servicing.

    While tracing out the circuit I was surprised by complexity of the design. I know these things need to do certain things under different conditions (and safely) but it looked like they tried to maximize usage of the simplest/cheapest components.

    Fortunately power outages here are fairly uncommon, usually short and such are my needs that UPS is not really needed; so much less the bother of maintaining and repairing.

    BTW something interesting I learned was how some of these batteries are rated. Amp-hours is common, but another is the watt-hours per cell over a short-term heavy load (15-20 minute backup). For one case "1234" in part number means 12v, 34 Wh per cell. By my estimation for 12v, six cells nominally 2v each, that's 204Wh for 20 minutes which translates back into roughly 5.7Ah. For battery rated 7-9Ah under a C/20 (light) load, this gives indication of reduced capacity under heavy load.


    Dave

  19. #19

    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Quote Originally Posted by DIWdiver View Post
    Deep cycle will last longer if you discharge them most of the way each time before recharging them. .
    That is NOT true. Tens of thousands of fishermen know to keep discharge nearer to 40 or 50% *when possible*. During tournaments, if/when discharge is greater, immediate recharge is called for.

  20. #20
    Flashaholic* snakebite's Avatar
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    the deeper the cycle the fewer the battery will give.
    btw at the rate a ups drains its battery when it hits 10.5v shutdown the battery may only be 50% drained.
    and you get less as it ages.

  21. #21
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    Default Re: Battery capacity tester for 12v SLA in backup power supply?

    Quote Originally Posted by snakebite View Post
    the deeper the cycle the fewer the battery will give. btw at the rate a ups drains its battery when it hits 10.5v shutdown the battery may only be 50% drained. and you get less as it ages.
    Regular SLA "gel-cell" battery will be around 12.0v at 50% capacity, under light load. Dave

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