Charging test - can be done with car battery?

Hi,

I know the famous "charging system test" all too well unfortunately, so I also

know it has do be done with a fully charged battery.

My question is - in case I don't have a charged DRZ battery, or I suspect it's dead,

can I perform those tests with a random 12V car battery?

Can I do it with the car battery connected through jump start cables (with the DRZ battery disconnected of course).

Should I expect different results?

And for the reason I'm performing those tests -

My bike stood at the dealer's for 6 months.

They've charged it a few times, don't know when and how.

When I took it back it was charged and ran fine for 4 days, and suddenly today the battery is completely flat, even the speedometer screen is off.

starts fine with cables, as is said charging need to be tested.

Could this be a dead battery, that for some reason held up for four days?

Thanks!

Yes you can do the tests with a car battery. The battery being so much larger capacity, it will react differently plus its fully charged voltage is less.

Battery connected, key off, expect something around 12.5 volts. Exact voltage is not important.

Key on - Voltage should drop a little bit. Again exact voltage is not important.

Motor running - you want to see the voltage rise slowly above the key off voltage. Let it run for several minutes. If it goes to 13 volts or above, I would call it good. If it does not rise above key off voltage, there is a problem.

The rest of the tests can be performed no problem.

DO NOT EVER USE A CAR BATTERY on a motorcycle, or use one to jump start one, unless you have the proper low amperage cables. Automotive batteries have way higher amperage than a motorcycles, and can possibly harm the electrical system on the bike. I've seen it happen.

Please do not listen to stories that a car battery is wrong. 12 volts is 12 volts. Available amperage is not an issue. Amperage draw is based on the load not the source. There are several people on this forum that regularly answer electrical questions. They will all tell you the same thing. You are fine to jumper a car battery for starting and running electrical troubleshooting tests.

What is wrong is to use an automotive "booster charger" or "starting booster" on a motorcycle. Boosters put out much higher voltage than the small M/C battery can absorb so the entire electrical system sees much higher voltages.

It is also advised that when jumping from a car, the car should not be running. I agree with that but the reason is a little hard to explain. Just know that it is safer for the car to be not running.

In the original question, the poster intends to use the motorcycle to charge a car battery so naturally the car would not be running or possibly the car battery is not even connected to a car electrical system.

Thanks Noble!

I ran the tests with a car battery.

It all came out good (car battery went over 14V with bike running).

My battery is not charged, but still with key off I see ~10V, and with key on it drops to ~3V, and back to ~10V with key off.

That means the battery is dead, right?

So how come it was charged when I took the bike from the dealer's, and ran good for 4 days?

Thanks again.

That means the battery is dead, right?

So how come it was charged when I took the bike from the dealer's, and ran good for 4 days?

Thanks again.

It could be that the dealer used a mains powered charger that has special charging modes which your bike charging system doesn't have - such as an Optimate.

They can recover a battery to some extent but I wonder how much you gain by that. Once a lead acid battery has gone flat it's storage capacity will have been serverly reduced. It can also set-up a drain path within itself so even if left disconnected it's discharging itself.

You may get lucky a few times but if you keep discharging your battery to below normal level while storing a bike your battery will fail on you.

What is this 'nomal' level - 1 volt per cell is generally considered fully discharged (which is 12 volts open terminal voltage). I think once a battery is showing 10 volts or less the battery is in trouble.

DO NOT EVER USE A CAR BATTERY on a motorcycle, or use one to jump start one, unless you have the proper low amperage cables. Automotive batteries have way higher amperage than a motorcycles, and can possibly harm the electrical system on the bike. I've seen it happen.

I suspect only if there was a problem with the bikes electrical system to start with, or it had a 6 volt system like some older/smaller bikes do. Not that I think that happened in your case. A car battery could make a shorting problem worse but other than that I can't see any issues. As Noble said "12 volts is 12 volts". Amperage is asked for by the bike not the battery, but if the bike asked for too much (faulty electrics) the car battery can supply it so be very carefull when hooking a car battery to a bike.

Low amperage jump leads won't help - enough current to start the bike is enough current to burn out other electrics.

Low amperage leads would be a very good idea if just trying to trace a fault or test things other than the starter motor. A good plan would be to have an inline fuse in this low amperage lead. That way you can set a limit on how the bike can take.

DO NOT EVER USE A CAR BATTERY on a motorcycle, or use one to jump start one, unless you have the proper low amperage cables. Automotive batteries have way higher amperage than a motorcycles, and can possibly harm the electrical system on the bike. I've seen it happen.

explain, please. make a new thread if you like, but be very thorough and expect criticism.

I have blown several fuses jumping bikes from a car battery. But on same bikes I have jumped with no problem also many times. maybe just luck

It is not luck. Blown fuses are the result of current draw greater the the fuse rating. Has nothing to do with the battery current capacity. The stock battery has enough energy to light the whole electrical system on fire if a direct short were to occur. The 20 amp fuse next to the battery will prevent that.

The thing to consider is when a battery has gone dead there may be a reason for that. If that reason is a problem with the electrical system then jumping from any battery may cause further problems. It is not the jump that creates the problem. But he jump can add to it. So it is wise to know why a jump is needed before jumping to any battery. Car batteries get a bad rap because when someone needs a jump, what is around to provide 12 volts? Most likely a car, maybe a garden tractor, less likely another motor cycle. So the car gets jumped to the dead motorcycle and if something bad happens, the car battery gets the blame. Not fair but some urban myths never die.

I've jumped many bikes with a dead battery from a car battery without any problems over the years so long as the donor vehicle's engine is not running.That is key.

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