Would one of these be any use at all for monitoring leisure battery state?

[Capt.Golightly]

http://www.ebay.co.uk/itm/LED-Car-Battery-Electric-Cigarette-Lighter-Voltmeter-Voltage-Meter-DC-12V-24V-/230935260229?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item35c4d06c45

 

Would one of these be any use at all for monitoring battery state?

[RLWP]

I'm pretty sure we have discussed this before

 

In my opinion, it may be good at monitoring the state of the voltage at the lighter socket. How that might relate to what you want to know is beyond my experience

 

Richard

[Capt.Golightly]

would it not not tell you how many volts the batteries where putting out then? as in not allowing them to drop below 12,4v etc before charging?

Edited October 20, 2013 by Capt.Golightly

[bottle]

No it would tell you the voltage at the socket it was plugged into, which may be very different to that of the batteries.

[Chalky]

No. It'll tell you the voltage at the socket. Between the battery and the socket there will be voltage drops in the wiring and also in the socket contact. It would allow you to estimate those - provided it has been correctly calibrated. It'd be better than nothing however it's not a substitute for the correct tool / instrument

[RLWP]

would it not not tell you how many volts the batteries where putting out then? as in not allowing them to drop below 12,4v etc before charging?

 

Now, if there isn't any other current draw on the line containing the socket, and all the joints between the device and the battery (including the notoriously dodgy lighter socket contacts) are good, it will probably tell you what voltage the battery is at to one decimal place, within the accuracy of the meter

 

On the other hand, it would look Mega in the dash of your Citroen Saxo Man!

 

Richard

[Capt.Golightly]

given that the socket is wired to the batteries and aside from slight drops caused by cable length and the number of contacts etc is this likely to be wildly different?...barring some catastrophic fault between the socket and the battery that is of course..sorry you answered while I was typing thanks.

 

Now, if there isn't any other current draw on the line containing the socket, and all the joints between the device and the battery (including the notoriously dodgy lighter socket contacts) are good, it will probably tell you what voltage the battery is at to one decimal place, within the accuracy of the meter

 

On the other hand, it would look Mega in the dash of your Citroen Saxo Man!

 

Richard

Thanks Richard..But I didn't have a Citroen Saxo..... I had a Honda CB900f Hardtail Chop, and 1977 BMW R100rs instead as they both a tiny bit quicker

Edited October 20, 2013 by Capt.Golightly

[RLWP]

given that the socket is wired to the batteries and aside from slight drops caused by cable length and the number of contacts etc is this likely to be wildly different?...barring some catastrophic fault between the socket and the battery that is of course..sorry you answered while I was typing thanks.

 

Drops in the region of up to 0.5V for instance?

 

Well - I thought you wanted to monitor your battery to know what's going on. Which means you are interested in tenths or hundredths of a volt difference

 

It's a toy, Captain G, for young boy racers to bling their motors up with. If you really want to know, buy a Smartgauge

 

Richard

Edited October 20, 2013 by RLWP

[alan_fincher]

I think the bigger problem is that the accuracy of its reading is not stated.

It has been previously reckoned that to be useful in estimating even approximate state of charge a digtal volt meter need to e accurate to at least +/- 0.5%.

That is sometimes achieved by multi-meters costing tens of pounds.

I'm kind of doubtful that anything at under a quid will be accurate enough to be helpful.

[Ricco1]

I bought a similar one for a quid more, it's useful. It typically shows the voltage at .1 to .15 less than the batteries actually are. But once you know that you can allow for it. It's also useful to establish the lowest revs you can achieve maximum from your alternator when charging your batteries, as the voltage rises. Of course you could do this with a meter on the alternator, but this cheap bit of kit saves you the trouble. Well worth buying if you're new to boating (as I am) and want to get your head around things.

[Simple Things]

Is there anything on ebay that can be bought to test the acidity of some of the replies? it'd be useful sometimes on this site i think.

[George Kennedy]

At £2.19 delivered, it looks like a worthwhile purchase to me. All you need to do is to understand the relationship between the display and the voltage across the battery bank. Ten minutes with a voltmeter connected to your domestic battery bank would verify the difference, if any, between the voltmeter reading and the reading on this device when 1. the engine isn't running, 2. the engine is running at tickover speed, 3. the engine is running fast enough to let the alternator push out its maximum voltage.

The worst that can happen is that there is no useful correlation between the two, in which case you have wasted £2.19 and ten minutes of your life. Less than the price of and the time it takes to drink a pint, something that most of us have done on more than one occasion and not really regretted it. Buy one and let the rest of us know how you get on.

Is there anything on ebay that can be bought to test the acidity of some of the replies? it'd be useful sometimes on this site i think.

hear hear, well said Jeff.

[alan_fincher]

Is there anything on ebay that can be bought to test the acidity of some of the replies? it'd be useful sometimes on this site i think.

Odd reply.

 

I would have though several people have invested some effort into giving replies that might be informative to the OP.

 

Which, (acid bit coming now!), is more that you have done in your post.

[Simple Things]

I'm a beginer myself. And, have learned a little from the posts above. Just sometimes on this site a simple question can be asked and it seems there are a lot of keyboard warriors giving replies that would they do face to face? I dont know if they would. Its not the friendliest site and i refrain from asking simple questions as a result.

 

P.s. sorry to interject on the thread please carry on without me!

[alan_fincher]

I agree this site can appear unfriendly to a newcomer - very unfriendly sometimes, and we should be mindful of that.

I perhaps wrongly took your post to mean you felt several had done that in this thread, and I can't see that they have.

If I have misunderstood your meaning, (or said anything acidic to anyone else), then I apologise.

[Simple Things]

No worries Alan and thanks for your reply.

[George94]

I agree this site can appear unfriendly to a newcomer - very unfriendly sometimes, and we should be mindful of that.

 

I perhaps wrongly took your post to mean you felt several had done that in this thread, and I can't see that they have.

 

If I have misunderstood your meaning, (or said anything acidic to anyone else), then I apologise.

 

This site, or rather, certain people on it, can be very unfriendly, if not downright rude, and not just to newbies. And you know that. The least pleasant are often to be found amongst the ranks of the most prolific posters.

 

But on the other hand, many prolific posters are a model of courtesy and ever ready to be helpful. You are an example, usually. :-)

[Coelum Ruat]

I agree this site can appear unfriendly to a newcomer - very unfriendly sometimes, and we should be mindful of that.

 

I perhaps wrongly took your post to mean you felt several had done that in this thread, and I can't see that they have.

 

If I have misunderstood your meaning, (or said anything acidic to anyone else), then I apologise.

 

It is the rich mixture of kindly benevolents and cantankerous old know-it-alls that makes this site such a feast.

 

Indigestion is inevitable, but a good time is generally had by all.

 

If you have the courage to ask for opinion, you need to be able to hear it when it is given. Whatever the tone, I reckon it is given freely and with good intent. Persevere.

[Phil Ambrose]

Sometimes telling how it is can be mistaken for acidic. Once you get to know people or rather their on-line persona all becomes calmer.

 

Phil

[smileypete]

Bought this 5 digit voltmeter a few months back, was expecting something a bit el-cheapo but it's very accurate, easily enough for batt voltage reading. For the price, £2.71(!), and its accuracy I doubt there's anything else anywhere near it:

 

http://www.buyincoins.com/?r=product/index&pid=26013

 

 

Of course when connecting any voltmeter like this it's essential to put a low value fuse - say 2 or 3A, in the positive lead at the battery end to protect the voltmeter wiring.

 

cheers, Pete.

~smpt~

Edited October 21, 2013 by smileypete

[MtB]

The thing no-one has mentioned so far is that the battery voltage will be indicated less any volt drops in the wire to the socket, and if the wiring to the socket is carrying any substantial current (to say, a fridge) then the wiring voltage drop may well be substantial.

 

If there is a volt or two being dropped over thin wires on the way to the hypothetical fridge before it gets as far as the test socket, the voltage measurement from the toy will be utterly meaningless and misleading.

 

MtB

[Richard10002]

The voltage at the sockets at the front of my boat is quite a bit less than that at the back, (near the batteries), particularly when stuff is on, (TV, Radio, Laptop charger, Phone charger). However, I had a cheap digital voltmeter which I attached to the charger, and screwed onto the wall. It's reading was always very close to that at the batteries, so very handy until I got a NASA BM2.

[dor]

I've got a cheap (~£3) digital panel meter mounted at the front of the boat. It is linked to the 10mm supply put in for the TV which I don't use as the TV is 230V. It reads within 0.1V of my Blue Sea meter at the stern which is connected almost directly to the battery. I find it very useful as I like to know what state my batteries are in all the time.

 

Even if you do get a small difference between your meter and the actual battery voltage, then as long as you know the offset you still get a good idea of the state of the battery. Obviously if the feed is also used for something else that draws a lot of current like a fridge it will be less use.

[alan_fincher]

Yes, the biggest issue will be if any volt meter, whether dirt cheap or uber expensive shares a long cable run with something that sometimes draws current, and sometimes does not.

 

The variability of the volts drop would then render it fairly useless, unless you ignore readings when anything else is drawing current.

 

If it's on a dedicated feed for something you don't use as DOR says it should be OK.

 

A voltmeter on its own draws peanuts, so even bell wire the length of the boat should see no significant volts drop ofo that is all it is feeding.

 

I would still choose a cheap proper meter fully wired in though, even so.

[Ricco1]

The thing no-one has mentioned so far is that the battery voltage will be indicated less any volt drops in the wire to the socket, and if the wiring to the socket is carrying any substantial current (to say, a fridge) then the wiring voltage drop may well be substantial.

 

If there is a volt or two being dropped over thin wires on the way to the hypothetical fridge before it gets as far as the test socket, the voltage measurement from the toy will be utterly meaningless and misleading.

 

MtB

 

Only meaningless and misleading if you're not aware of it.

 

My cheap meter shows around .1-.15 volt less than if I measure voltage at the batteries. You're right, if you apply a load the voltage drops significantly.

 

For example: Cheapo voltmeter shows 12.4. I know it's 12.5 to 12.55 really.

 

Switch t.v. on: Voltage drops to 11.9. I still know the reality is around 12.5. A light will reduce the voltage by a further 0.1 volts, as will the radio.

 

So the reading does mean something, providing that you spend a bit of time switching things on and off when you buy it, to gain that understanding.

 

OK, it's not perfect. But for me it beats having the lift the cruiser deck board, position myself awkwardly in the engine bay getting at the battery terminals, which are not easy to reach. Especially when it's raining!

 

I agree that a better piece of kit, properly wired in would be an improvement on the cheapo but if you're not flush, 3 quid will give you a good idea of what's going on.