Flummoxed by a small meter

[Simpo Two]

Yesterday I bought a small LCD multimeter for light duties, £4.99 from Mapiln.

However whilst the voltage side of the meter seems to work perfectly I can't get any reading from the current side. There are five ranges from 200 microamps to 10A and no matter which combination of range and socket I try (one does high current, the other low) I get a reading of zero. I'm a little hesitant to test it on mains, but certainly on batteries of 1.5, 9 and 12V the current is always zero. Am I doing something wrong or is it faulty?

[Simpo Two]

Hmm, thought it might be something like that.

I bought the meter at the same time as a breifcase-style 13W solar panel to charge boat batteries.

How would I measure the current produced by the solar panel? Put it in the live line between battery and panel? But then you have the battery current coming from the other direction - milliamps from one side and two car batteries with a combined current of god-knows-what on the other. Which side wins?

ETA between the panel and batteries there's also a seperate charge regulator.

http://www.maplin.co.uk/module.aspx?moduleno=99760...

Edited by Simpo Two on Saturday 13th November 11:25

[Simpo Two]

GarryA said:

Simpo Two said:

Hmm, thought it might be something like that.

I bought the meter at the same time as a breifcase-style 13W solar panel to charge boat batteries.

How would I measure the current produced by the solar panel? Put it in the live line between battery and panel? But then you have the battery current coming from the other direction - milliamps from one side and two car batteries with a combined current of god-knows-what on the other. Which side wins?

Current measured will be the load, just because car batteries are say 400A max output does not mean you will pick that up unless you attach a load to them i.e. a running starter motor.

P = IV

2 car batteries are 24v if the solar panel is 13W then I = P/V which is roughly 500mA.

The batteries are in parallel; it's a 12V system.

I hate electrons, they're too damn small to see!

[Simpo Two]

GarryA said:

Unless the batteries are attached to a load greater than what the solar can charge? Then you are going to see a discharge current.

O/P is this solar charger just clipped to the batteries? Or are the batteries disconnected from the supply (I mean totally isolated) when on charge by the panel?

I don't intend to run any devices from the panel because in normal use the batteries will have enough power between cruises. The panel is simply there to keep the batteries topped up, and principally during the winter lay-up (5 months on the bank with no mains power).

There's a batttery isolator as you see here, currently 'off'. Even when it's 'on' the only electrical things on the boat are four lightbulbs and a starter motor.

Here's the regulator connected to batteries by clips:



And here's the regulator:



By deduction from the curiously-worded Chinese instructions, both lights being on is good. If the panel is overcharging then one light goes off; if there's something drawing too much current (the setup has an option to connect another device) then the other light goes off.

I was trying to judge whether the panel was sending too little or too much power to the batteries ot keep them topped up.

Edited by Simpo Two on Saturday 13th November 12:06

[Simpo Two]

xllifts said:

You people scare the st out of me sometimes! If you don't know what your doing leave well alone!

People like you are the reason my and other trades peoples Liability Insurance is so high and the reason the H+S is so restrictive!

Get yourself on a electronics appreciation course and learn the basics rather than poke and see

Oh FFS, it's only a 12V battery.

Do you really think I'm going to pay someone to plug a mickey mouse solar panel onto a 12V battery? And who would do it anyway? If it was dangerous they wouldn't sell them.

Edited by Simpo Two on Sunday 14th November 00:26

[Simpo Two]

I have also not been on a course on how to operate light switches which are mains and therefore very dangerous. I am frightened it may go wrong and I might kill myself; in fact you may be in the nick of time to save my life.

Lucky you turned up really. Please quote me for coming over in about 30 minutes to operate my bedside light for me.



If you can't contribute anything useful, save your 'industry outrage' for somebody else please.

Edited by Simpo Two on Sunday 14th November 00:48

[Simpo Two]

xllifts said:

Its far from an Industry outrage, its a statement of how incompetent fools play with fire and then get burnt costing us trained professionals in the pocket!
Items such as test equipment should not be allowed for general public purchase to stop unskilled people meddling with stuff they have no knowledge on.

For a constructive comment

'you don't have a clue so leave it alone'

HTH

My apologies for being a little sarcastic last night but it was late and I didn't expect such an attack.

You should write a strongly worded letter of complaint to Maplin and every other company that sells meters, and do it today before any harm is done. It is not my fault for buying it; after all I am simply an ignorant fool bedazzled by shiny things. It is their fault for selling it.

Now the question, before you waded in puffing your chest out was 'How to read the current of a 13W solar panel with a meter?'. You told me I was ignorant, should go on a course, and that 20mA would stop my heart.

This sort of silly fact, whilst no doubt correct in certain (undefined) circumstances, is akin to saying 'A bucket of water can kill 12 people'. Yes it, can, if they stick their head in it for long enough, but we are still allowed to carry buckets of water around without safety certificates and training courses.

My field is photography, and if someone posts a question about cameras I don't tell them 'You're ignorant, go on a course'. It would save me much time, but when they replied that they felt my comment unhlepful and aggressive, I could warn them that a camera can kill them. And it will, under certain circumstances.

Actually, I just realised that the batteries in my cameras probably put out more than 20mA - how can I still be alive? Just lucky I guess.

And so to regain some sense of perspective, I am not fititng a distribution borad in a house and I am not wiring up an electricity sub-station, I am simply connecting a poxy meter to a poxy solar panel that couldn't tickle an ant. Indeed, if you can think of any way that a car battery and a solar panel could be used with fatal consequences I'd be interested to hear them, so that I can avoid them and therefore be less ignorant.

The trick to forum advice is to disseminate one's information in the best way to assist. Everyone who posts for advice on a forum is ignorant of the answer, or they would not be posting! Naturally if someone posts 'I am about to stick a metal rod into mains socket, will it hurt?' then you can dive in guns blazing. But simply to brag about your qualifications whilst not providing any useful information is silly, and words such as 'tt' are not awfully constructive either Mr Poledriver. But perhaps it was the only thing you could think of.

[Simpo Two]

I'm going in...