Battery problems
06-20-2005, 07:08 AM
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Battery problems
Amanda's car has a flat battery, the door was left slightly open all weekend and the battery is completely flat. Too flat to jump off the S2000 or even get any lights on the dash board 
So I've borrowed a charger from my neighbour, but the battery keeps blowing the fuse in the charger
Does it sound like the battery is completely fecked, or should I take it to my local Auto electrician to charge up?
So I've borrowed a charger from my neighbour, but the battery keeps blowing the fuse in the charger
Does it sound like the battery is completely fecked, or should I take it to my local Auto electrician to charge up?
06-20-2005, 07:18 AM
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Connect the cars together, leave yours running for a while(2 mins) and then try starting up.
Strange that the battery is blowing a fuse on the charger, sure you've got the connections OK and that the battery isn't fusing against anything.
Get a multimeter (
Strange that the battery is blowing a fuse on the charger, sure you've got the connections OK and that the battery isn't fusing against anything.
Get a multimeter (
Another good reason for running a beater
06-20-2005, 12:33 PM
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Lead acid batteries degrade fairly quickly while they're discharged. I wouldn't expect much damage to occur after a few days of being flat but they will degrade.
Always always keep your car/bike batteries topped up. Foregoing accidents like leaving the door open there's no reason for a car battery to degrade over time when you use a decent charger. If the car/bike is going to sit in the garage for a while and the vehicle has an alarm/stereo to slowly drain it connect the battery to a battery conditioner at least once a week.
Do note that sealed lead acid batteries (you can't top them up and there's no breather tube, may be an overflow tube though) require different charging characteristics than unsealed. Make sure you've got a charger which can do the right type of battery. Hellfrauds do sell a combined charger with a selector switch.
A few things:
- If your battery is blowing charger fuses it's either short circuit (possible but unlikely), you're connecting it backwards (connect red to +, black to -) or your charger is buggered. Switch charger and/or battery to prove the point but don't connect this battery to anything but a charger until you've figured out what's up.
- Measure the voltage across the battery terminals using a voltmeter. A fully charged battery should hold 13.8 volts (6 cells of 2.3 volts each). It's quite common for one or more of the cells in the battery to die, giving a reduced or zero voltage. If you measure 11.5 volts then 1 cell is almost definitely dead. A good battery should measure 13.8v after charge and almost exactly the same after excessive load (e.g. starting the car). Do not measure the battery voltage while it's charging except as below.
- It's meaningless to measure battery voltage whilst it's charging unless you want to verify the charging circuit itself. Certain motorcycle charging circuits (the Honda VFR is a classic case) are well known to overheat and die, and when they die they do nasty things to the battery. The charging voltage for a 6 cell lead acid battery is about 16v, anything more and the battery will literally boil (get very hot and degrade VERY fast). Most charging circuits are designed to generate enough charge current at relatively low engine revs, which means that they have to tame the excess energy at high revs. If a charging circuit gives out much more than 16v when you rev the engine the charging circuit is toast and will eat batteries for breakfast.
- NEVER EVER connect a flat battery to a charged battery. NEVER. NEVER EVER. Cell resistance of lead acid batteries is low enough that if you do so the huge current surge is likely to destroy one or both batteries, both jumper cables and if you're particularly unlucky the charging circuit. You must NOT charge a flat car battery from another car battery without a current limiting circuit in the middle. You may not see the damage immediately but the damage will be there. I can elaborate on this further if you don't believe me.
In short: Charging the battery on another charger is a good idea and a sensible way to identify the fault. I suspect that you were either inadvertently (and embarrassingly) connecting it backwards or the charger doesn't have a current limiting circuit and the flat battery is effectively short circuiting it. If you're unlucky despite charging the battery now it may continue to give you further problems. If so there isn't much option but to buy another one and put signs on the car doors
Always always keep your car/bike batteries topped up. Foregoing accidents like leaving the door open there's no reason for a car battery to degrade over time when you use a decent charger. If the car/bike is going to sit in the garage for a while and the vehicle has an alarm/stereo to slowly drain it connect the battery to a battery conditioner at least once a week.
Do note that sealed lead acid batteries (you can't top them up and there's no breather tube, may be an overflow tube though) require different charging characteristics than unsealed. Make sure you've got a charger which can do the right type of battery. Hellfrauds do sell a combined charger with a selector switch.
A few things:
- If your battery is blowing charger fuses it's either short circuit (possible but unlikely), you're connecting it backwards (connect red to +, black to -) or your charger is buggered. Switch charger and/or battery to prove the point but don't connect this battery to anything but a charger until you've figured out what's up.
- Measure the voltage across the battery terminals using a voltmeter. A fully charged battery should hold 13.8 volts (6 cells of 2.3 volts each). It's quite common for one or more of the cells in the battery to die, giving a reduced or zero voltage. If you measure 11.5 volts then 1 cell is almost definitely dead. A good battery should measure 13.8v after charge and almost exactly the same after excessive load (e.g. starting the car). Do not measure the battery voltage while it's charging except as below.
- It's meaningless to measure battery voltage whilst it's charging unless you want to verify the charging circuit itself. Certain motorcycle charging circuits (the Honda VFR is a classic case) are well known to overheat and die, and when they die they do nasty things to the battery. The charging voltage for a 6 cell lead acid battery is about 16v, anything more and the battery will literally boil (get very hot and degrade VERY fast). Most charging circuits are designed to generate enough charge current at relatively low engine revs, which means that they have to tame the excess energy at high revs. If a charging circuit gives out much more than 16v when you rev the engine the charging circuit is toast and will eat batteries for breakfast.
- NEVER EVER connect a flat battery to a charged battery. NEVER. NEVER EVER. Cell resistance of lead acid batteries is low enough that if you do so the huge current surge is likely to destroy one or both batteries, both jumper cables and if you're particularly unlucky the charging circuit. You must NOT charge a flat car battery from another car battery without a current limiting circuit in the middle. You may not see the damage immediately but the damage will be there. I can elaborate on this further if you don't believe me.
In short: Charging the battery on another charger is a good idea and a sensible way to identify the fault. I suspect that you were either inadvertently (and embarrassingly) connecting it backwards or the charger doesn't have a current limiting circuit and the flat battery is effectively short circuiting it. If you're unlucky despite charging the battery now it may continue to give you further problems. If so there isn't much option but to buy another one and put signs on the car doors
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