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Suzuki GS500- dead battery or regulator/alternator?

Discussion in 'Maintenance and Servicing' started by TeeKey, Feb 1, 2015.

  1. Hi guys,

    Apologies if the thread already exists.Tried to find some info here but no answers so starting a new one.

    Brief description of the 'problem',

    Left my GS500 in a garage for approx. 2 weeks and came down to start it and it wouldn't. I purchased a motorcycle battery charger left it overnight and it started without problems. The battery however would go flat every 2-3 days and would have to repeat recharging it. (Note: I do very short trips 2-3 times a week)

    Few days ago mate asked me to plug in an air pump to my battery because his bicycle tyres were flat and it drained my battery completely and even after charging it wouldn't start. Lights come on and all but once you press the ignition button it makes a weird noise and the lights fade a bit.

    I push started it few times and kept on riding alright but the battery wouldn't recharge ( I do very short trips so no surprise here). The bike ran fine with the push start and upon acceleration the light would go brighter. Yesterday however on my way back from work (after a push start) I noticed that the lights would fade when accelerating and I "lost" the Speedometer and Odometer mid-ride (they remained on 0 or would flap a bit, later on regained the speedometer).

    Would it be just a flat battery issue or something more serious??

    I know it might be a noob question but I'm not particularly good with the mechanical staff ( learning phase)

    Would be really grateful for any advice or information.

  2. First of all do you have a multimeter? Doesn't need to be fancy, but for diagnosing electrical issues it is essential to at least be able to measure voltage. Do you have a lithium or a lead battery? If you haven't changed it, it is most likely (90%+) to be a lead-based one.

    If/once you do, check the battery's voltage with the bike turned off (before it's been charged at all), then with it turned on. To do this you set the multimeter to DC voltage (should be a V with tow parallel lines, one solid, one dashed) and touch the black to the neutral (-, negative) terminal and the red to the positive (+) terminal.

    Before charging, assuming it is lead acid, 12V means the battery is flat, 11V-12V means the battery is very flat, below 11V means the battery is kinda dead, below 10V means the battery is definitely dead. It should sit at thirteenish.
  3. You almost certainly have a dead battery. If it won't accept charge from a charger it is most certainly dead.

    Gauges will normally stop working when the battery is almost flat this shouldn't be a sign of other problems.

    Replace your battery and you'll be good to go.
  4. Sounds like one of two possible things is happening and you need to determine which.

    Either you a generating charge but the battery is stuffed and won't hold it, in which case you need a new battery. Or you are not getting charge to the battery. If this is the case, one of two possible things is happening and you need to determine which.

    Either you the alternator isn't generating power or the regulator/rectifier is stuffed and it's not getting the power you are making to the battery.

    Step one is to measure the voltage of your battery with engine not running, then motor and rev above idle say 2-4k revs and see what voltage is.

    With engine off a good battery should be around 12-12.5 v. With motor revving should increase to around 13.5v. If you are getting the 13.5 v it is probably battery. To test this charge the battery, isolate it by removing from bike or at least disconnecting leads and check it again next day. While disconnected the voltage should not drop significantly.

    If the battery seems good but you aren't getting 13.5 or thereabouts volts with engine running you will need to test that the alternator and reg/rec are working. This is a bit more complex so not going to describe here but there are plenty of YouTube vids showing how to test. Google is your friend. And if alternator isn't working then the first suspect is the stator.

    Finally if charging circuit and battery both seem good, a final possibility is that you have a leak somewhere, a bit of equipment or a sort which is draining battery.

    Our resident electrical guard is cjvfrcjvfr who may be able to provide further advice and also check mine for something resembling accuracy.
    • Agree Agree x 1
  5. My Comments in red text.

    Cjvfr has more bike experience, but I think I can help out sometimes. :bag:
    • Agree Agree x 2
  6. Thanks for the input gunissangunissan

    I certainly didn't mean to imply cjvfr was the only guru and I am sure your knowledge exceeds mine

    I agree that a battery in good condition should exceed 12.5 V. But I have had a couple of vehicles (one a car) start and run happily for a year or so with a battery which was barely holding 12v . It was obviously on its way out but it lasted a bloody long time dying which is why I used the lower figure.
    • Like Like x 1
  7. Hi guys, agree with pretty much all above. To the OP a simple multimeter is a worthwhile investment when doing bike electrics and a fairly cheap one. Heavy cycling of the battery may have done it some harm but as discussed above I wouldn't dismiss charging circuit issues yet.
    • Agree Agree x 1
  8. No problem GreyBMGreyBM no offence taken and none implied. A few detail corrections is all, you were basically correct in all you said. (y)(y)

    And to TeeKeyTeeKey , as cjvfrcjvfr has said, a multimeter is pretty well crucial for these sort of problems. Beg, buy, or steal one and the process is a lot easier.
  9. Correct, the information is basically correct.

    Any 12 volt battery is fully charged at 12.7V, Flat at 11.9V and recoverable above 10.5V. Anything over 12.7V is float voltage as a result of charging. Anything under 10.5V and you might as well throw it away.
  10. The only thing I'll add is that Lead-acid batteries need to be cycled quite regularly. If you only ride every 2-3 weeks you will find you will only get about a year out of them.

    Get a more modern "sealed" battery. These things are much more forgiving to irregular use.
  11. Hi guys,

    Thanks heaps for all the info and advice.

    Went to buy the multimeter today. I tried to perform everything according to your instructions.

    The battery with the engine turned off was at 11.4-11.6 with the running engine 12.6-12.8, once revved above idle fell to 8.9-9.6...which would be consistent with weird gauge behaviour and fading lights while accelerating

    I did not try anything else today- a bit time restricted.

    What could be wrong?
  12. Two things:
    A: Your battery is dead flat
    B: It's not getting enough charge

    Could be multiple things. But, flat battery means its not getting charge and so does the fact the voltage drops when the bike is revved. In saying this though, the battery may be on it's way out and as it isn't fully charged. It might not be taking a charge as it's past it's used by date.

    Something is possibly wrong with the charging system. Unfortunately you can't test a flat battery to see if it has a problem too so you'll have to get some charge into it. at 11.4V the best thing to do is find another (similarly sized) fully charged 12V battery and hook it up + to + and - to -. This will even out across both batteries and should give you more than 12V. Then you can get it on a charger to charge it fully. Once this is done you can get it tested. If you're near a Battery World they can do this (generally free of charge - no pun intended). The other things to do is borrow a similar sized battery from a friend if you're lucky enough to have a friend with a similar bike that has a suimilar battery.
    • Agree Agree x 1
  13. "battery with the engine turned off was at 11.4-11.6"
    Yep, battery is flat, needs a charge. May also need replacement depending on how old it is. Charge it first and see how it performs.

    "with the running engine 12.6-12.8"
    Getting some charge at idle, voltage still seems a bit low.

    "once revved above idle fell to 8.9-9.6"
    Ru-roh, not good. Something wrong with charging circuit. Rec/reg and/or stator.

    With luck cjvfrcjvfr will be along soon to help out.
  14. I'd follow DonJuanDonJuan 's suggestions. See if the battery is recoverable but definitely seems a charging issue. Looking like Reg/Rec but I think I would do some tests on the alternator stator.

    Get the battery charged up first then with the bike off disconnect the stator and measure the resistance between the windings. These are generally yellow wires. 1-2 2-3 3-1 they should be low resistance and much the same resistance on each.

    Then switch your multimeter to AC volts, start the bike. Measure the AC volts between each phase 1-2 2-3 3-1 you should have the same reading on each. Generally 50-60v. If the alternator seems to be ok then it is probably reg/rec.
  15. As said earlier there are a couple of good YouTube vids that show to do this
  16. Hi TeeKey,
    +1 to cjvfrcjvfr's post above.

    From your original post and descriptions, it sounds like the battery is OK but the charging system has died.
    Once you've charged the battery and prove that it holds its charge then I'd be looking at the rectifier/regulator.
    You'll still need to ensure that the stator is providing enough power.
  17. Thanks a lot guys!

    I will definitely try your advice DonJuanDonJuan.

    If the worse comes to worse what do you think would be the cost of repair of such issues?
  18. A reg rec is pretty much bolt on and plug in and would probably cost $100 or so. Stator will cost more just for the part and will require a few more bits to be pulled apart just to get to it.
  19. Given that it's chargin ok at idle, but then falling over with revs, I'm betting the rectifier.

    The GS is an older design of bike and you'd expect to see around that at idle then a bit more with a few thousand RPM.