http://cgi.ebay.co.uk/ws/eBayISAPI....479033981&viewitem=&sspagename=STRK:MEWAX:VRI

 

Why not buy one and try? It looks like it could work and is cheap enough.

 

If it's not temperature compensated (which it doesn't appear to be), then it will only be reasonably accurate for the temperature range that it was programmed for.

If your battery core temperature doesn't change much (slow charges/discharges; maintained indoors) then that wouldn't be much of a concern.

Those monitors were probably made using PIC10Fx uC's to make them small in size.

 

I'm guessing at room temperature they'd probably function fine, but who knows at automotive temperature ranges. Looks like a nice device but the price seems a bit high, then again it performs a very basic function with no fuss or muss.

 

Speaking of automotive temp ranges, I wonder if they used a uC that's specifically rated for the automotive temperature range or better, and whether it was designed to withstand the high transient peaks that are typical for that environment?

 

Who knows? Plenty of people in my motorcycle forum are ordering them and starting to give some feedback. Since our antique bikes don't have a voltmeter onboard, and adding a regular one whether it be digital or analog is difficult to mount without it standing out like a sore thumb so it looks like a potential solution. All we want to know is if our charging system or battery is failing.

Motorcycle charging systems are often rather weak and the tiny batteries we use are lucky to last 3 years given even the best attention.

Feedback from the manufacturer is once we've got it set to the range we want it to remain in that we seal the back up with marine grade silicone sealer or an equivalent and of course not use it until the sealant has cured for a few days. Some people don't realize that silicone sealer remains a bit conductive until it's finally set up fully (which highly depends on the thickness you apply) and the older common ones with a high acetic acid content are often worse for use on circuitry than the newer 3M caulk that is far less aggressive such as their 4200 or 5200 line which is even available in small squeeze tubes. Regular caulking compounds tend to hold moisture and can play heck with anything that has CMOS in the circuitry.

http://www.jamestowndistributors.com/userportal/siteMap.do?action=map2&catId=32 is a fairly comprehensive listing of some of the better ones.

 

So replace the alternator/dynamo...
The problem with bike electrical systems is that the typical dynamo they're attached to won't actually be able to produce anything when the engine is idle.

 

I don't think you could build one for $10 and end up with the nice "fit and finish" the one you are looking at offers. It may be overpriced, but people need to make money.

I'd also guess it is a 10F20x uC running it all, I'm curious as to the method of voltage regulation in a package that small, not a lot of room for caps, even SMD. 10F200 standard temp range is -40C - +80C, they also offer an "Extended Range" that is -40C to +125C. The price difference is 6 cents ($0.58 vs $0.64).

I'd be more concerned about the power supply rated temps than the uC, especially any filter caps (if they exist). I'd probably add one external to the unit to be sure. A 10Ω/47uF Automotive cap filter could be added on the input would clean up the power quite a bit over what may already be inside, without dropping too much voltage (though it could be programmed around the new input).

 

I'd say it's more than a fair price considering what it claims to do especially since they're just starting out on stuff and have to make a few $ for their efforts.

Naw, we know when our stators are going out easily enough if we ride at night, problem is that we dread having to replace them because it's an engine out job not to mention the cost of a rewound stator, gaskets etc. The engines on the CX/GL Honda's take but an hour to remove and put on a bench if you've got a helping hand or are strong enough to lift one but by habit if we ever have to break one open we do all the cam chain stuff at the same time. Properly serviced these engines will run easily to 300K miles.

True, as even with a car it isn't going to charge at idle but we've got no kick start on these bikes and push starting one is almost an impossibility unless you've got at least two people helping you push the beast. In most cases it's merely a poor connection to the stator or to the battery itself, not to mention that common MC batteries fail on regular occasions.