Technical question: 349 batteries

Discussion in 'REME' started by SoftPawn, Jun 16, 2004.

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  1. Hi folks; I'm looking after the signals kit for a TA unit and having trouble getting 349 batteries to charge on the IBMUs because some are duff. Is there an easy way to find out which ones are bad with a voltmeter?

  2. Is it worthwhile?

    :( :?: The TA I know don't know or want to know how to turn a radio on.

    Anything other than knock off at 4 and go on the piss and they are not interested.

  3. I just like playing with radios. It wasn't for anyone else to use.

    :) Yes we knock off civvi work at 4, try and get all our kit together, turn up at TAC, get more kit together, then we're off into the hills for the weekend. Back on Sunday, clean up, into the pub midafternoon and then yes out on the pish - and a cheap one too after two days in the open air, giving the liver time to recover and deprived of sleep....

    But theriouthly; I don't want to be responsible for people having to carry around 351s when a 349 would do! I wouldn't be very popular, and then no-one would buy me BEER.
  4. It's no use using a voltmeter - most batteries will stay at their rated output voltage for 90-95% of their 'lifetime'. You need to use some sort of discharge tester, but what figures are involved, I don't know. Most discharge testers are designed for use with car batteries.
  5. Thanks MikeMcc; however I'm not after ones that are 'old' (yet), rather after ones that are causing the IBMU to report an error (and so not charge any) when they're inserted. I was wondering if this might be caused by shorted cells (which would report a different voltage) or summink. Anyway I have a voltmeter now so will try that out; if it doesn't work I shall have to hunt for a discharge tester. In fact, presumably they can be made? They're just ammeters yes?
  6. Take a known good battery and a known bad one. Measure the resistance across the terminals. This will give you a benchmark figure to determine which are likely to be knackered because of a short.

    However, if the battery is short circuit, a voltage reading across the terminals will be zero or close to it anyway.
  7. Hmmm I think using an ordinary meter to measure resistance of batteries can be bad for the meter (as most meters measure resistance by applying a voltage and measuring the current flow). But:

    If it's just a single broken cell then the voltage will certainly be different. I shall investigate next time I'm in.
  8. [BFG dons technical head & strenuously advices AGAINST checking the resistance between the two terminals of a battery]


  9. Cutaway

    Cutaway LE Reviewer

    BFG -

    Bugger, you beat me to it !
  10. Only just, by the look of it.

    There's a lot to be said for sitting in front of the PC instead of the TV waiting for 22 grown(ish) men to kick a ball about.


  11. Especially given the result :-(
  12. God I'm so boring, still posting stuff about batteries. Still, for reference, measure with a voltmeter - they are nominally 12V:

    Good 349 batteries: 10V+
    Possibly OK: 8V+

    otherwise they wilnae werk, chuck em back up the line.
  13. To softpawn, the easiest way to check that a battery is u/s is to put a simular voltage test lamp and then put your voltmeter across it. That might help you.
  14. The quickest way to test a battery is to lick the two terminals, not the most scientific of tests i know, but you can tell instantly if there is a serious problem.

    How good the beer would taste after licking a unit's worth of 349 batts i don't know.. :roll:
  15. Aaargh the battery thread is back to haunt me!

    For reference, it seems that once the batteries (349, 351, whatever) have discharged too much, the "Intelligent" Battery Charging Unit assumes they're broken. You have to get a Stupid Battery Charging Unit (eg a slow charger) to recharge them. Which of course, we don't have in our unit. And we don't have time on one Tues a week to charge all gazillion of them on one six-pack charger, so after a while they all fade away into uselessness. And sending them up the chain to someone with a stupid charger gets a bollocking for not keeping them charged. And indenting for pencil batteries for the cassettes is one of those herculean tasks involving sphinxes and riddles and mucking out stables or something.

    If this was a commercial company we'd all be on the dole. Rantirant rant etc.