Hooking up combination voltmeter / ammeter

[popefelix]

So I bought a panel mount voltmeter / ammeter to put on my ST1100 (98). I run a lot of accessories (including an amateur radio transceiver) on the bike, and I want to make sure that I'm not draining the battery when I'm using stuff. Mounting it wasn't hard, but I'm at a loss as to where to connect it. I'd really like to monitor the total current draw on the bike (including things like fuel pump and headlights), but the ammeter can't handle more than 15A, and I don't want to burn the thing out every time I start the bike.

The ammeter wants to be connected in parallel with the "hot" wire going to the load, so I was figuring on using one of those "tap" connectors from the auto parts store and attaching it to something. But I don't know what. If I hook it up to the wire coming off the battery, is the meter going to see the starter current as well as everything else?

 

[dwalby]

there's a lot of possible answers to your question, but you're right about the 15A not being sufficient to monitor total current draw on the battery. So you don't want it in a path that includes everything. That leaves the individual fused circuits as options, but I can't really see what benefit monitoring just one of those would provide. Generally the voltmeter is sufficient for monitoring overall electrical system health, the ammeter is probably not something you really need.

edit: looked at the simple schematic after following the link and it appears that you're stuck with monitoring both voltage and current on the same circuit, they're not individually selectable monitoring points. This may be a problem if you want to measure right at the battery, where all current loads will be monitored and you'll exceed your 15A meter limit. You probably have to monitor one of the fused circuits (10A so the fuse blows before the meter) because you're going to be monitoring more than 15A at the battery terminal, and I can't predict what that may do to the meter.

If its returnable, I'd return it and look for a dedicated voltmeter without the ammeter. The other issue with the meter you have is it sits in series in the ground path, so if the meter continuity fails you'll lose ground continuity and the circuit you're monitoring with it will be dead.

 

[k2mpw]

Ditto what dwalby said... Powerwerx isn't bad stuff but a little pricey. Keep in mind that you want that voltmeter on the ACCy side of anything or else the meter will be on ALL the time and kill the battery you are trying to monitor! Here's some other info and a different take... what I did...
OOOPs it looks like st1300.us.com is no longer.... so all those pictures for the aux relay project are toast.... You might want to search st-owners for "aux relay" and see what pops.

 

[popefelix]

Ditto what dwalby said... Powerwerx isn't bad stuff but a little pricey. Keep in mind that you want that voltmeter on the ACCy side of anything or else the meter will be on ALL the time and kill the battery you are trying to monitor! Here's some other info and a different take... what I did...
OOOPs it looks like st1300.us.com is no longer.... so all those pictures for the aux relay project are toast.... You might want to search st-owners for "aux relay" and see what pops.

I'll do some looking. Thanks and 73 de W0KEH

 

[Jim Van]

I would just get a simple & cheap digital voltmeter to monitor the battery charging voltage. If it gets too low, then switch off an accessory.

Like this one :

P1 Green LED Digital Waterproof Voltmeter Gauge Meter 12V-24V Car Auto Motorcycl | eBay

LED Digital Display: Precise 3-bit LED digital display. This can only delay our service. - Got a problem?. No Problem. You will be pleasantly surprised by our service.

www.ebay.com

And you could replace your headlamps with Evitek LED's to give you more amps for your accessories.

p.s. My brother is WA8ZLQ

 

[Jim Van]

Yup, The voltage across the shunt is measured and the current through the shunt would = V(shunt) / R(shunt) . Where , V(shunt) = voltage drop across the shunt.

 

[popefelix]

Keep in mind that you want that voltmeter on the ACCy side of anything or else the meter will be on ALL the time and kill the battery you are trying to monitor! https://qsl.net/k2mpw/honda/st1300/usbvoltmeter.htm

How much current is that voltmeter going to consume, realistically? I wouldn't imagine more than a few mA. And I guess that can add up over a while, but how long is "a while" here?

 

[dwalby]

How much current is that voltmeter going to consume, realistically? I wouldn't imagine more than a few mA. And I guess that can add up over a while, but how long is "a while" here?

yeah, its not much, but when its drawing 24/7 it can add up over time, best to avoid that possibility altogether.

 

[SMSW]

I mounted a voltmeter on my V Strom 650 because the alternator on Suzi's bikes is small compared to a full blown touring bike (or the ST). If you do the same, and simply check the voltage now and then, you will be fine. The voltage at the battery should be 13+volts, if it drops down into the mid 12's when you turn your loads on, then the alternator is not keeping up with your usage and you are draining the battery. Of course you can get a separate ammeter and mount it in series with the battery, and this will tell you when the battery is charging or discharging, but I don't think its necessary.

Once you install the voltmeter, ride the bike w/ no auxiliary loads and observe the voltage at various rpm's. Watch it at idle as well. Then turn on all of your loads and do the same checks. This will probably tell you all you need to know.

 

[W7AX-Lee]

The voltmeter is not a bad idea. Just needs to be on a DC point downstream of the ignition switch. The ammeter is a whole different scenario. First off, in order for it to be useful, it would have to monitor the complete current used from the battery. This would require an ammeter capable of reading about 60 amps. Usually a shunt is used and the meter is calibrated to suit that shunt. I think you would be far better off forgetting the ammeter idea.

 

[Larry Fine]

Felix, I can probably help you get it wired. I need to see the wiring instructions.

Never mind; found it:

This meter measures current on the negative side of the circuit, not the positive. That means you would have to isolate the ground side of whatever load you want to monitor, so won't work in this application, where everything uses the chassis as the negative conductor.

 

[Larry Fine]

A few things to note: A voltmeter is wired from hot to ground, like a load would be wired, while an ammeter is wired in series with the hot wire, like a fuse would be wired. In a vehicle, the ammeter is used to determine whether the battery is being charged or discharged at any given moment, so should be wired between the battery and the rest of the vehicle.



The right place to insert an ammeter in a vehicle is between the battery and everything else (other than the starter motor). The alternator's output wire should be connected to the bike's main wire on the bike's side of the main fuse, but on the ST (and most Hondas) the main fuse is fed at the starter relay, so the starter and main fuse share the battery's + wire..

See upper right corner here (click to enlarge): http://st-riders.net/aow/AOW - ST1100/one page color 96-97 std wiring 3.jpg

See where the battery's heavy black wire connects inside the starter's relay to both the starter relay's contact and the 30a main fuse? The electrical fix would be to instead connect the main fuse (or more practicable, the main red wire through a new 30a fuse) to the alternator fuse's red wire, and then those joined wires to the ammeter's - terminal, and the + terminal to the battery +.

 

[popefelix]

Thank you, Larry. That was very helpful.

I think my best course of action here will be to return the combination voltmeter/ammeter and get a straight voltmeter instead. Connecting an ammeter in series with the battery the way you describe seems like an awful lot of work, and as other commenters have noted, the thing I really care about is voltage.

 

[ST Gui]

A voltmeter is wired from hot to ground, like a load would be wired, while an ammeter is wired in series with the hot wire, like a fuse would be wired.

I didn't see this mentioned earlier and was curious as to how a ammeter could work wired in parallel. I put an ammeter on my GL1000 (I think from some Honda bike – the Interceptor?) and it was in series. I had to run some heavy gauge cable and more than once I got across the meter's terminals and got a little arcin' and sparkin'.

For my money the ammeter gives a better indication than a voltmete. But like anything you learn to interpret voltage and assume conditions based on that. When the ammeter reads 0 or –X there's no guesswork.

But a voltmeter is much easier and potentially safer to install and can do pretty much the same job so that's how I'd go.

 

[popefelix]

I didn't see this mentioned earlier and was curious as to how a ammeter could work wired in parallel.

Hall effect or a shunt as described by Jim Van. I saw a combination voltmeter / Hall effect ammeter on Amazon yesterday, but there was an aluminum body voltmeter that was prettier and fit in the hole I'd already cut.

 

[jrp]

[...]
I run a lot of accessories (including an amateur radio transceiver) on the bike
[...]

Curious about your transceiver/antenna setup OM.

Jeff (NØDT)

 

[popefelix]

I'll have to make a big post about it at some point. Short version: Yaesu FTM10R/E with the main unit under a board attached to the tail and the head unit attached to the left side of the fairing, about 6 inches below the TCS / ABS switches. The radio is paired to a Sena SMH-10 which is attached to my helmet. I built an external PTT switch for the radio, so I don't have to use the Sena for PTT. Antenna is a Comet SBB-5 attached to the board on the tail.

Plans are to replace the board on the tail (which is a piece of scrap I had laying around) with something nicer. Maybe another board, maybe an aluminum or steel plate, I don't know.

 

[Jim Van]

Hall Effect ammeter - that's new to me. I need to research that - sounds like a great idea. The current flow creates a magnetic field that creates a potential at right angles to the direction of current flow because the electrons get pushed to one side. Then the voltage difference due to the difference in electron density is measured and the voltage magnitude is proportional to the current flow - slick.

EDIT : This is the way I would go for the ammeter. Cheap & Simple - can't beat that !! Hall Effect Ammeter ( Even cheaper on EBay ) I would choose the 100 amp version.
And I would also install the voltmeter in post #6 , since you can't have too much data ( or do too much PM ).

 

[John OoSTerhuis]

EDIT : This is the way I would go for the ammeter. Cheap & Simple - can't beat that !! Hall Effect Ammeter I would choose the 100 amp version.
And also install the voltmeter in post #6 , can't have too much data ( or do too much PM ).

Interesting, Jim. I don’t claim to understand much of this, but it looks like you just run the red wire from the battery through the 100A version’s (link) circular sensor. Sez it can display amps and volts. The shielded cable looks to be too short for a motorcycle install though...(?) Thoughts... anyone?

It would be really neat to see the total/individual draw/load while underway.

John

 

[jrp]

Interesting, Jim. I don’t claim to understand much of this, but it looks like you just run the red wire from the battery through the 100A version’s (link) circular sensor. Sez it can display amps and volts. The shielded cable looks to be too short for a motorcycle install though...(?) Thoughts... anyone?

It would be really neat to see the total/individual draw/load while underway.

John

Looks like it comes with an extension. However, it is not waterproof.