Break Down

Your bike's voltage regulator shunts current to ground over a specific voltage (14.4v?). When you hook up a running car, the car's alternator detects the current draw / voltage drop and 'ramps-up' to keep the voltage up, supplying more current. Your bike's VR was designed to sink the excess current from your bike's alternator and may be overwhelmed by the running car's supply.

A non-running car is ok - the car's alternator is not active...
 
I was under the impression car electrics and bike electrics could handle the max you'd see from a car. If that's not the case then it makes sense. I agree that the battery could be slightly damaged but if you're boosting your battery probably isn't the greatest anyway.
 
unL33T said:
I was under the impression car electrics and bike electrics could handle the max you'd see from a car. If that's not the case then it makes sense. I agree that the battery could be slightly damaged but if you're boosting your battery probably isn't the greatest anyway.
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I don't know about that.
The battery in my mid size van is 1000amp @ 12v... we can weld with that, easily. That's more than enough to fry some cheapo electronics.

What damage am I going to do to my battery?

...just playing the devil's advocate....This could be quite funny.
 
FLSTC said:
Your bike's voltage regulator shunts current to ground over a specific voltage (14.4v?). When you hook up a running car, the car's alternator detects the current draw / voltage drop and 'ramps-up' to keep the voltage up, supplying more current. Your bike's VR was designed to sink the excess current from your bike's alternator and may be overwhelmed by the running car's supply.

A non-running car is ok - the car's alternator is not active...
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This makes sense.
 
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The voltage regulator of the bike is on the "other side" of the battery in the primary circuit. Unless it has a problem the energy from the boost wouldn't get to the voltage regulator. The regulator/rectifier has diodes on the output. (Think about that for a minute).
You're not boosting to the alternator windings.

The voltage will stabilize using the regulator in the boosting vehicle at it's voltage set.

So, no, that actually doesn't make sense.

On a charging system that isn't broken (something going to ground that shouldn't for example), with just a low battery, when you connect the boost the only load will be charging the low battery. Not a lot of load. (Yes it is possible to over charge the battery if it is EXTREMELY low, but if it is EXTREMELY low the battery is already damaged).
If you have more load than charging the battery, you gots other issues.

Let's go back to my van with the 1000amp 12 volt battery.
It has a 130 amp 14.4 volt alternator.
Which one is going dump electrical energy faster?.

To answer your question: Way back when cars had generators and crappy batteries. Boosting cars was a common thing. If you drove you knew how to boost a car,and when you boosted a car you had to rev up the boosting car to get over 12.5 volts.
You don't have to do that anymore and a percentage of boosts result in some idiot getting caught in moving stuff under the hood and getting hurt pretty good. If the boosting car is off, there's only half a chance some idiot is gonna get hurt.
There is no electrical reason.
 
frekeyguy said:
1. Never boost with a running car. This is going to cause havoc on your
bike's electrical system - there is going to be way too much amperage.
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?

Sorry, incorrect. If they're both 12V systems and the polarity is correct no harm will come from jumping even with the donor vehicle's engine running.
 
Finally got around to replacing the battery and my findings are as follows:

New battery before install 12.94 volts (as it should be.

Bike started ok, and after a bit of warm-up time the voltage while the bike was running got up to 14.10 volts.

I wasn't able to ride it around and test it again as I busted my ankle and I'm in a cast .

From what everyone is saying, the readings are good, and hopefully the only problem was the old battery was a dud.

Sent from my ONEPLUS A3000 using Tapatalk
 
Weird, I had to bump start my old VFR for a month till I got around to replacing the batt. Once started, it had no problem running.
 
Riceburner said:
Weird, I had to bump start my old VFR for a month till I got around to replacing the batt. Once started, it had no problem running.
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I guess my bike needs a charge on the battery to keep running. I'm surprised since it's pretty basic.

Sent from my ONEPLUS A3000 using Tapatalk
 
ay33 said:
I guess my bike needs a charge on the battery to keep running. I'm surprised since it's pretty basic.

Sent from my ONEPLUS A3000 using Tapatalk
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I wonder if a battery is required and needs a charge because the bike has a digital transistorized ignition system?
 
The CDI ignition needs around 11 volts to work. It will shut down when it hits 10 volts.
If your battery has a short to ground,and it seems your battery was shorted to ground, the load from the battery will drag down the output voltage from the alternator. In your case it dragged the voltage below 10 volts, so the bike won't run.
The ignition doesn't care/know where the voltage is coming from; the battery or the alternator, it only cares that there is enough power to fire.
 
unL33T said:
Can someone with apparently more electrical knowledge than me explain why boosting from a running car would damage the electrical system? Maybe I need more coffee but I have an electronics degree and can't think of how it would cause a problem unless there was a short somewhere. I've boosted three different bikes several times off running cars and never had an issue.

I've once connected several batteries in parallel to get enough amperage to turn over a truck engine that had been sitting for a long time but that's a different story.
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My concern would be surges. Does an air conditioner in the car kick in or some other load that results in a surge? With the donor vehicle off its battery would be static.

When the disabled vehicle starts there could be a startup surge that affects the donor. How many surges before a component fails?

The extra power from a running motor isn't needed to boost an otherwise sound bike. In the case of a crapped out donor car trying to start another crapped out heavy vehicle in winter maybe every extra millivolt is needed.

I had an old boat with a 5.0 L V8 and the recommendation was to start the engine before turning on any electronics because of a potential surge from the starter.
 
When something like an air conditioner comes on in the donor vehicle there will just be a slight voltage drop, not a spike, to the boosted vehicle so that isn't really an issue.

I could buy the argument that inductive kickback from the coils in the bike's starter could potentially be an issue for any powered up devices in the donor vehicle but I would expect modern starters and electrical systems to be designed in such a way that it's not a problem or you'd have issues just from starting your car unless it cuts power to everything when the starter is running and that can't be the case or the most sensitive item, the ECU, wouldn't be powered up and the vehicle wouldn't start.
 
unL33T said:
When something like an air conditioner comes on in the donor vehicle there will just be a slight voltage drop, not a spike, to the boosted vehicle so that isn't really an issue.

I could buy the argument that inductive kickback from the coils in the bike's starter could potentially be an issue for any powered up devices in the donor vehicle but I would expect modern starters and electrical systems to be designed in such a way that it's not a problem or you'd have issues just from starting your car unless it cuts power to everything when the starter is running and that can't be the case or the most sensitive item, the ECU, wouldn't be powered up and the vehicle wouldn't start.
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My point is that if you only have a discharged battery (Someone left an accessory plugged in) and both vehicles are in good shape there is no need to have the donor vehicle running. If one vehicle is a bike the weather is likely warm so no cold battery issues.

Most electronic devises are surge protected but repeated surges can break down surge protectors. Induction is a *****.
 
If your car is running and it's voltage regulator has a voltage-setting higher than the voltage-setting of the VR on your bike, then the car's alternator will continue to drive current while your bike's VR will be sinking that extra voltage/current to ground. Will heat up and depending upon the duration and current flow, may cause the bike's VR to fail.

If the voltage-setting is the same or less, no big deal.
 
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