Measuring current drain on running bike/trike?

[titusni]

Tonight I'll be connecting up my multimeter to measure the voltage across the battery when idlng and also when the RPMs increase to see how my new stator and rectifier are doing (plus switching on lights etc and seeing the effects).

As per the Haynes book I previously connected the multimeter as an Ampmeter in series with the battery when the power was off to measure the drain of my immobliser. However the Haynes book mentioned about *NOT* doing this with the engine/power on.

Is it not possible for me to connect up the ampmeter to measure the current with the engine going? I'd like to do the same as for voltage - check idle, 4000/5000rpm, lights on and off, etc.

[davesatan]

you can do it but the problem you have is the starter motor current normally far exceeds what you meter can take . meters normally only take 10 or 20 amps in theory you could switch it inline after you have started it

[titusni]

you can do it but the problem you have is the starter motor current normally far exceeds what you meter can take . meters normally only take 10 or 20 amps in theory you could switch it inline after you have started it

I just got home and checked the meter - 10A max :-(

Connecting up the meter when the engine's going sounds a bit dodgy - sparks likely?

I guess I could check current draw further downstream in individual circuits - but I'd like to know the full drain on the r/r and battery - in particular whether when idling the stator is supplying enough current to run everything or not or whether its getting "topped up" by the battery.

I recently upgraded the Max's stator from the stock 25A to an aftermarket 33A one.

[smeghead]

or nip down the scrapyard and get an ammeter from an old mini, or other old car should only be a few quid, the go up to abot 40 amps i think

[titusni]

I've damaged a few test sets in me time so I bought an induction ammeter from Vehicle Wiring Products. It's not milliamp accurate but is very usefull for the tests you want to do. Dead safe and highly recommended. Just hang it on the battery + wire an jobs a good un.

That sounds just the job - plus I was just about to order some other stuff from them - so 18.61 for the 75A one. Its hard to see from pic - does this clip on to cable or do I tape it to live wire? Hopefully crank doesn't exceed 75A.

[guydewdney]

i cant believe that any stator on a bike would be able to run everything at tickover (headlights, brake lights etc)...

one simple way to check is to run it on tickover, check voltage, leave everything on, go for a fag/spliff/cup of tea, come back, check voltage.

why the hell do you want to be able to run everything at tickover anyway? 99% of the time you will be revving it a bit when riding... unless you sit in the queue at traffic lights ;)

Guy

[titusni]

i cant believe that any stator on a bike would be able to run everything at tickover (headlights, brake lights etc)...

one simple way to check is to run it on tickover, check voltage, leave everything on, go for a fag/spliff/cup of tea, come back, check voltage.

why the hell do you want to be able to run everything at tickover anyway? 99% of the time you will be revving it a bit when riding... unless you sit in the queue at traffic lights ;)

Guy

This is a triked V-Max. Maxes never had exactly the best electrical system around (marginal at best) and this one is the original 1985 vintage. When it was triked it ended up with 2 headlights (was 2x55/60W - currently 2x35/35w) instead of the usual 1, it also ended up with 3 tail/brake lights, an immobliser, and a few other things.

At the start I had several occasions when I saw sitting at traffic lights and the engine rpm suddenly fluctuated and then it died - always with dip or full beam on.

Eventually I twigged that 2 headlights + 3 brakes + various other things (indicators, fan) were taking too much power.

I changed the front indicators to LEDs, changed the instrument panel/speedo bulbs to LEDs, and have an LED to replace the mid tail/brake/numberplate light and downgraded the 55/60W headlights bulbs to 35/35W.

With that done the only time its stalled recently was at night with indicators on, sitting on brake and the fan kicked in.

So I decided to upgrade the stator/rectifier for an aftermarket one - 33A vs stock 25A - plus the new one is supposed to produce more amps at lower rpms.

Yeah I could sit at lights blipping the throttle to stop it dying but I'd rather not have to.

Plus I'm about to wire to a headlight relay harness so I can change the headlights back up to 55/60W bulbs so power drain will increase again.

[guydewdney]

nice big chunky battery? Like a car one? trick looking belt drive from crank to car alternator (the one in my car is a 120 amp one...)

split charger (off a caravan system)? charges one battery until charged, then uses 'spare' power to charge second battery. use second battery to run lights etc, first to run engine / fan - so if the lights drain the battery to almost flat, at least the engine still runs / you can start the trike even tho' you have left your lights on (damhikijkok)

[titusni]

Cranking can use quite a bit of power depending how thick the oil is (temp & type) and what kind of motor it is. I think that a V-max would well exceed 75 amp.

Well its the old 2-brush starter the early Maxes had which aren't supposed to be as powerfull as the 4-brush starters on the later models.

So if it does take more than 75A will this damage the meter or will it be ok?