Is it ok to leave my volt meter switched on ( I've wired meter thru a switch directly to the battery ) all the time when I'm riding ? A respected mechanic ,who's my neighbour , says one of his customers had a meter he plugged into his cigarette lighter in his car and this buggered up his alternator. He insists it affects the diodes in it somehow . ? ? ? Anybody heard anything like this before ? I know ours are on bikes and his was in his car but I'm unsure weather to switch it on .
Well thats a load of bull. You bike will be fine, if left sitting in storage and switched on long enough it could drain the battery but thats it. That car had other issues.
Yah, that's a massive load of shit. Personally, I'd put it on a relay so it's only working when the ignition key is in the ACC or ON position though so it doesn't drain the battery.
I did what Jeff mentioned but with an additional feature. I added a power controller (PDM60) and added a momentary switch that will trigger the circuit that controls the relay. This way I can press the button and get a reading without needing to have a key and turn the bike on. The same circuit also comes on when the ignition is on.
Thanks for your thoughts. I didn't think it would affect my bike but didn't want to question him as he's a really nice guy.
The LED type volt meters consume very little power. So its safe to connect the + side of the volt meter via a 1amp inline fuse to any wire which only goes live with the ignition turned on. The rear light feed is a fairly easy access wire and if you want you can use it as relay trigger source for accessories as well. Run the - side to any earthing point, and you are good to go. A lot of the cheaper meters from China are not very accurate - so don't get overly worried about the number shown. What you want to see is the number staying fairly stable when the engine is running - if it takes a nose dive or shoots though the roof - you will at least have a chance to head for a safe place to stop before whatever is left in the battery is used up and the bike shuts off leaving you stranded. SkiMad
A voltmeter is supposed to have an extremely high resistance. However a bad unit may have a relatively low resistance. Put this bad unit in parallel with a car circuit long term, and the result is the voltmeter significantly reduces the impedance of the system. Very very bad. I doubt this was the case, but getting a bad unit out of China? Certainly possible. Do you know what kind of meter it was? I am wondering if it was a multimeter. If they flicked the control to the wrong setting, like AC or ohmeter, and left it there long-term, that could cause a problem. Three, there are low impedance voltmeters available. These intentionally load the circuit, like my first example. This meter is expensive and used for utility companies. Maybe the vehicle owner thought that this high-end meter he got at a garage sale would be good for this purpose. I believe the mechanic's story but think that it was a bad or incorrect device, or otherwise user error. Unless it was a self-fulfilling prophesy. Why is this person connecting a meter to the car? Seeing problems? Maybe the alternator was already having problems and the first diode failure was imminent. Although the mechanic probably would have known this scenario from the customer's story.
http://www.ebay.co.uk/itm/DIGITAL-L...614543?hash=item1eb203d54f:g:v1wAAMXQdohREU7A One of these ,not necessarily this one.
Searching the Internet I have found two stories total of people questioning whether the items they connected to the cigarette lighter burned up the diodes in the alternator. Your mechanic's story is the third. Maybe a bad unit there did cause a problem. But, there just is not enough evidence anywhere to suggest not to use that voltmeter. I'd say you have to go with the crowd here and use it to your heart's content!
