The Morris battery. Again.

How much did you pay? RS were still selling them new up until fairly recently. May still do. Over 500 quid. My ancient one is still in good nick, having recently replaced the stitching on the leather case. ;-) But it never gets used. Batteries removed to prevent corrosion.

In message , GlowingBlueMist writes

I remember them, but sadly, no, don't have one. Good thought though.

A friend spent quite a few months replacing the main battery on his boat as he couldn't find a fully charged battery that would turn the engine over. In the end he found out that the cable between the battery and the engine there was a 0.9V drop so he was only gettign 11V at the engine whereas previously he only ever measured the voltage from the battery which was 12V. Once he replaced the cable the engine started, but the lenght of this cable was almost theb lenght of the boat, so unlikely to be the cause in a car.

In message , whisky-dave writes

Indeed, car cable is probably about a foot long. Car parked yesterday, battery fully charged and connected. I'll see what happens tomorrow, 48 hours later.

I paid just under £100, and it is in as-new condition, immaculate, with case. I think RS stopped selling them several years ago, although they were still on the website.

Production stopped in 2008.

In article , Dave Plowman (News) scribeth thus

Points?, aren't they for trains to run o??.....

FFS buy a new battery already.

Moggies are from the steam train era

NT

;-) It's a 50 year old car.

However, a dwell meter still has its uses on a modern car. All coils - even multiple ones - will still give a dwell reading pretty similar to points ignition. A dwell meter will also give a reading from (some) injectors, as it measures the mark space ratio.

I keep a cheap one in the motorhome and only use it in dire emergency. We have about five dire emergencies per trip, and the meter is invaluable.

Bill

The next part, which is harder, is learning how to use it.

Lesson 1: don't connect it across a circuit when it's set to measure current. Current measurements are made in series with a load, and even then only after careful thought.

Lesson 2: Don't get mixed up between AC and DC.

Lesson 3: Buy some decent test leads, ones where you can fit different ends: croc clips, probes, etc. The ones supplied with the meter will be s**te.

Lesson 4: Test the meter before use. For resistance put the probes together; the reading should be zero or near enough. For DC voltage use a dry battery. For AC voltage I generally use the mains. For current I use a DC source and a headlamp bulb.

Lesson 5: turn the damned thing off when you've finished with it.

Any more tips, anyone?

Bill

I helped a friend (a friend in need...) who had a similar problem in a motorhome. For some bizarre reason the starter battery was in a locker instead of in the engine compartment. It wasn't all that far but during a start the voltage at the starter motor was about 6V. In the end we put the battery back where it should have been and that fixed it.

Bill

In message , Huge writes

But it would break my heart if I did, and the same thing happened :-)

on 10/05/2018, Bill Wright supposed :

Many people do not understand volts drop and just how serious a problem it can be at such low voltages. They base their calculations simply on the current rating of the cable and even the pros ignore volts drop..

In message , Bill Wright writes

Thanks Bill. I'm certainly no expert, but have used an ancient analogue cheapo Eagle meter for years, mainly, I admit, with low voltage stuff (old toy trains!), but enough to know the difference between measuring volts and amps. I will, however, shout if/when I'm unsure!

In message , Harry Bloomfield writes

It is a problem those of us involved with old toy trains are well aware of, using up to, say, 20v/5amp, but more usually 12-15v/1amp. Even with longer track lengths (36 inches) and good, tight rail connections, the difference across an oval can be substantial, so multiple feeds are required, using good quality heavy duty wiring, with soldered connections. None of you needed to know that :-)

The good RC car racers do as they often go as far as soldering directly the things like the speed controller to the motor and even to the batteries using the shortest lengths of the largest CSA and best quality copper wire that fits. As you say, if you only have 7.2V in the first place ...

When I made up some extension leads for my electric outboard motor (because for good boat trim I needed the batteries in the bow) I used quality, copper, stranded starter motor / welding cable that was probably 6 x the CSA of the original outboard cables.

When I built my electric endurance racing 'motorbike', even though the main battery cable was pretty heavy, I was able to use the voltage drop over it to drive a mini DVM calibrated in Amps.

Cheers, T i m

Yup - even my pretty expensive Fluke came with near rigid PVC leads and silly probes. Naturally, Fluke sell a kit of decent ones.

(The as supplied probes were so large they were only of use on big terminals - near useless for electronics.)

I keep trying to persuade members of my old car club to measure voltage drop directly - ie across either ends of the cable. Which may mean extending one of the test leads. Which then isolates just where the drop is occurring - 'live' or ground. And that open circuit measurements are pretty useless - you need to measure under load. But am whistling into the wind. ;-)