Cheap Voltmeters anyone?

[pedroinlondon]

My SmartGauge packed up! Or maybe it didn't, it could be that my amateur wiring came back to haunt me. It was fine for over a year but now it displays 100% charge ALL the time, which unfortunately is not true.

I will try to reset it soon and perhaps bring it back to its senses, but this small crisis alerted me to the fact that I should have more independent ways of measuring the batt bank, the starter battery and the power in from the solar panels.

 

Has anyone tried the cheap voltmeters for sale on ebay? You know, the little ones with only two wires and a digital display like this one:

 

http://www.dx.com/p/0-3-lcd-two-line-3-digital-dc-voltmeter-multicolored-2-4-30v-289940#.VFzdf_m-2Fw

 

It would be handy to have three or four of them giving some info of the several points all the time. Handy, if the info is fairly correct that is. Any good experiences?

 

Thanks in advance.

[Laurie Booth]

My SmartGauge packed up! Or maybe it didn't, it could be that my amateur wiring came back to haunt me. It was fine for over a year but now it displays 100% charge ALL the time, which unfortunately is not true.

I will try to reset it soon and perhaps bring it back to its senses, but this small crisis alerted me to the fact that I should have more independent ways of measuring the batt bank, the starter battery and the power in from the solar panels.

 

Has anyone tried the cheap voltmeters for sale on ebay? You know, the little ones with only two wires and a digital display like this one:

 

http://www.dx.com/p/0-3-lcd-two-line-3-digital-dc-voltmeter-multicolored-2-4-30v-289940#.VFzdf_m-2Fw

 

It would be handy to have three or four of them giving some info of the several points all the time. Handy, if the info is fairly correct that is. Any good experiences?

 

Thanks in advance.

Works fine. I plug it into my 12v socket for a read out. Shop around, I paid 99p inc postage!! Posted from Hong Kong

[keble]

I bought a round one to replace an analogue meter. Works fine. Might not be very accurate but good at least for relative measurements. A few quid on ebay

[bottle]

Smartgauge will give erroneous readings if the battery capacity is 50% below that of the original capacity.

 

Note: That is not the State of Charge but the amount of amp.hrs the capacity is now.

 

for example if the original bank was 100 amp.hrs the capacity will now be less than 50 amp, hrs or technically dead batteries.

 

All that a volt meter will tell you is the voltage at that point nothing about your batteries.

 

To know voltages and the amp flow etc. then this would be good. UNI T UT203

Edited November 7, 2014 by bottle

[magnetman]

I'm going to challenge you on that bottle.

 

A voltmeter will show you a certain amount of information if the batteries have not been subject to heavy charge or discharge. What I mean is if the voltmeter shows say 12.0v and there is nothing switched on then it is probably worth charging up. While a simple voltmeter is quite an unsophisticated device I think it is misleading to say that it tells you 'nothing about your batteries'

 

I've got cheap as chips voltmeters on my start battery, main battery and generator battery and they all do give reasonably useful information specially on the start and generator batteries which are at rest for long periods with no discharge - the voltmeter DOES show if the battery is self discharging over time.

For power in from solar panels I would recommend a Watt meter as used by Radio Control plane fanatics

 

will add link in a minute

These things really are good They will give instantaneous amps, voltage, watts, accumulated Amp Hours and if you go for an 'Eagletree' version you can get a full data logger which will give you volts, amps, temperature in more than one place and other things measured every second for about a month before you need to download it onto the laptop

 

quite cool. I used one to take measurements of my solar output when I was using a tracker made with a satellite dish motor.

 

Also logged my fridge power consumption.

 

Probably a bit anoraky for most people

http://www.ebay.co.uk/itm/DC-LCD-60V-100A-Balance-Voltage-Boat-RC-Heli-Battery-Power-Analyzer-Watt-Meter-/390932345418?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item5b0562324a

[Taslim]

Probably so Magnet man but it's rather a nice Anorak and I have a use for something like that.

 

Find Pay Pall pasword! Find....

 

Edit for fat fingers and to add that those little ones similar to the one spoted by the OP, are great. I bought a box of 10 (much cheaper that way & free postage) and have found them usefull in many situations. My ones are encapsualted & tough as old boots.

Edited November 7, 2014 by Taslim

[trackman]

Smartgauge correctly wired will tell you the voltages on two battery banks, if you have two.

The voltage measurements are just that and not affected by the % figure for the domestic bank.

Separate voltmeters unnecessary unless the unit is completely done in somehow. If you suspect that it's simple enough to check using a multimeter. If this confirms the Smartbank voltage figures then why fit more voltmeters?

A different matter altogether if the multimeter does disagree though.

[smileypete]

These look alright, uk seller:

 

http://www.ebay.co.uk/itm/Blue-Backlight-Digital-Voltage-Meter-Voltmeter-DC7-5-19-99V-LCD-Display-UK-Stock-/271542272682

 

These read 200 amps too, though only one direction and Asia based seller:

 

http://www.ebay.co.uk/itm/0-100V-200A-Shunt-DC-4-Digital-Voltmeter-Ammeter-LED-Amp-Volt-Meter-12v-car-/191226438481

 

There are ones that do current in both directions but may need a separate isolated supply so a bit fiddly.

 

ETA: Not come across these before, looks like they have an isolated supply built in so can read current in both directions easily, nice :

 

http://www.ebay.co.uk/itm/DC-200A-Red-LED-4-Digital-Display-Panel-Ammeter-Ampere-Meter-Shunt-AC-DC12V-260V-/231354947935

 

cheers, Pete.

~smpt~

Edited November 7, 2014 by smileypete

[bottle]

I'm going to challenge you on that bottle.

 

A voltmeter will show you a certain amount of information if the batteries have not been subject to heavy charge or discharge. What I mean is if the voltmeter shows say 12.0v and there is nothing switched on then it is probably worth charging up. While a simple voltmeter is quite an unsophisticated device I think it is misleading to say that it tells you 'nothing about your batteries'

 

I<<<<<<<<SNIP

 

 

You are right to challenge it and it was a sweeping statement.

 

I just did not put the qualification about batteries at rest etc.

 

Personally my batteries are never at rest and the use of a volt meter would tell me nothing about the batteries except as I said the voltage at the point of reading.

 

Also to be useful for battery SOC readings it would need to connected directly to the battery because of volt drop anywhere else in the boat.

 

ps. 12v reading is a little late, if going by the guideline not to go below 50% SOC, to charge the batteries. Assuming batteries have been rested and not being charged or discharged.

 

Of course a reading of 12v would be possible if there was a load

[Guest]

 

 

You are right to challenge it and it was a sweeping statement.

 

I just did not put the qualification about batteries at rest etc.

 

Personally my batteries are never at rest and the use of a volt meter would tell me nothing about the batteries except as I said the voltage at the point of reading.

 

Also to be useful for battery SOC readings it would need to connected directly to the battery because of volt drop anywhere else in the boat.

 

ps. 12v reading is a little late, if going by the guideline not to go below 50% SOC, to charge the batteries. Assuming batteries have been rested and not being charged or discharged.

 

Of course a reading of 12v would be possible if there was a load

Yes a volt meter requires some interpretation when the batteries are in use (as opposed to rested.) I have sort of got used to this though, and use just an accurate voltmeter. I have never had a smart gauge, though have heard good reports, and can see the sense in them.

[pedroinlondon]

Thanks for your comments, they all seem to be positive. I hate typing on this ipad so will comment (and ask more questions) once i get a proper keyboard.

By positive i meant to the point lol. Getting a digital meter from argos now. The analogue i have not good for my decaying eye sight not lol.

[bottle]

See my post #4

[magnetman]

 

 

 

 

 

snip.....

 

ps. 12v reading is a little late, if going by the guideline not to go below 50% SOC, to charge the batteries. Assuming batteries have been rested and not being charged or discharged.

 

Of course a reading of 12v would be possible if there was a load

That depends on the quality of your batteries and access to cheap (mains) power

 

A lot of people advocate running a good quality traction battery down to about 11.7v to get maximum value out of a consumable product.

Or should that be productS

 

Batteries & diesel

[bottle]

That depends on the quality of your batteries and access to cheap (mains) power

 

A lot of people advocate running a good quality traction battery down to about 11.7v to get maximum value out of a consumable product.

Or should that be productS

 

Batteries & diesel

 

First I have heard it but you live and learn.

[pedroinlondon]

Brethren,

 

This is going to be a long one. First of all thanks everybody for the input. Really good. I will get some voltmeters to save me the time of going around with a multi meter in rain and snow, but really, I’m glad I mentioned why I needed one, as otherwise I would not have got a probable solution to what is affecting my Smart Gauge.

 

What BOTTLE said is (I think almost) correct. I seem to remember that when I fitted the SGauge nearly two years ago, the manual instructed me to charge the batteries to 100% and let the gadget know that at that point the batts were fully charged. The problem of the percentual calculation being wrong now is that the batts are 2 years older and obviously they are not charging to the same capacity as when I fitted the thing. I will look into re-installing it. Possibly all that is happening is that the gadget is indicating 100% when the batts are probably between 80 and 100%.

 

I don’t think that the SGauge will only give wrong info if the batts are knackered, a small decrease in their capacity will give a small error in the reading/calculation.

I have newish solar panels, which I thought had been useless in the last few weeks, but today I ready the voltage output from them and it was about 14V!

Either the boaters that have been telling me that the panels are useless between October and March have terrible solar panels, or my cheapo ebay ones are extremely good. Or both?

I did get a digital voltmeter as the dial on my analogue meter is not good enough for my eyesight, or vice-versa, and carried out some readings, after one hour cruising. They were:

 

----------------------------

With solar panels connected

SGauge indicated: 14 V

Multimeter on the batts: 14 V

 

With solar panels disconnected

SGauge: 13.6 V

Multimeter: 13.8 V

----------------------------

So, not giving wrong readings, which again indicates that the problem must be what BOTTLE said, really. The batt changed and no one told the SGauge about it. Sounds about right doesn’t it?

 

No excuse not to have a voltmeter fitted to the solar panels. If I had one I wouldn’t have been so surprised that the batts were charging “by themselves” and there was good reason for the SGauge percentual display info to be high (even though not possibly 100% at 6 a.m. after having the lights on the night before for hours lol).

 

Thanks

[Dinz]

Have you had solar for long? unfortunately volts don't equal watts with them.

Perhaps smart gauge has been 'confused' by the panels?

Were they installed after SGauge set up & how?

[bottle]

The Smartgauge does not need to be told anything it is completely automatic.

 

It may take a few cycles of charge, discharge to be accurate.

 

It is not accurate whilst batteries are being charged, up to 10%.

 

The Smartgauge will always tell you the SOC of your batteries but it is the SOC of the capacity the batteries have.

 

Example:

 

New batteries, 100 amp.hr bank fully charged the SG will show 100%

 

Old batteries (same original capacity 100amp.hr) but now can only 'hold' 50 amp.hrs, fully charged to the 50amp.hrs the SG will still show 100%

 

When the battery bank is really old/knackered and cannot even hold 50 amp.hrs then the SG may show onerous readings.

 

When you took your volt readings , what was the amperage flowing.

[pedroinlondon]

I cannot read amperage with the way the connection is, without opening the circuit. Will get one of those gadgets magnean suggested above, or similar.

[smileypete]

I cannot read amperage with the way the connection is, without opening the circuit. Will get one of those gadgets magnean suggested above, or similar.

 

(Time for the regular 'clamp meter' cheerleading post methinks.... )

 

For occasional amp reading such as timing the weekly long engine or genny charge, plus power audits or problem diagnosis, it's hard to beat a DC clamp ammeter/multimeter aka 'clamp meter'. These have jaws that open and clamp round the wire to read DC current to reasonable accuracy.

 

Maplins do a Unitrend 203 for £40, CPC do their own rebadged Tenma version for £30ish incl delivery, plus on Ebay there are others notably the Mastech MS2108A starting from £27 incl delivery.

 

 

http://www.maplin.co.uk/p/uni-trend-203-dcac-current-clamp-multimeter-n41nc

 

Be careful if looking at other models as there are cheaper ones that only read AC current, maybe best choose from the above ones.

 

Your boaty friends may regard you as a genius if by wielding one of these you can help solve their electrical gremlins.

 

cheers, Pete.

~smpt~

Edited November 12, 2014 by smileypete

[ditchcrawler]

 

(Time for the regular 'clamp meter' cheerleading post methinks.... )

 

For occasional amp reading such as timing the weekly long engine or genny charge, plus power audits or problem diagnosis, it's hard to beat a DC clamp ammeter/multimeter aka 'clamp meter'. These have jaws that open and clamp round the wire to read DC current to reasonable accuracy.

 

Maplins do a Unitrend 203 for £40, CPC do their own rebadged Tenma version for £30ish incl delivery, plus on Ebay there are others notably the Mastech MS2108A starting from £27 incl delivery.

 

 

http://www.maplin.co.uk/p/uni-trend-203-dcac-current-clamp-multimeter-n41nc

 

Be careful if looking at other models as there are cheaper ones that only read AC current, maybe best choose from the above ones.

 

Your boaty friends may regard you as a genius if by wielding one of these you can help solve their electrical gremlins.

 

cheers, Pete.

~smpt~

Just bought one from Maplin but take care, there is one hanging beside it that looks almost identical but doesn't measure DC amps and they don't have the spec on the box. I had to go through the sheet inside to find out.

[bottle]

As mentioned in post #4 but the hint was not taken.

[pedroinlondon]

I'm going to challenge you on that bottle.

 

A voltmeter will show you a certain amount of information if the batteries have not been subject to heavy charge or discharge. What I mean is if the voltmeter shows say 12.0v and there is nothing switched on then it is probably worth charging up. While a simple voltmeter is quite an unsophisticated device I think it is misleading to say that it tells you 'nothing about your batteries'

 

I've got cheap as chips voltmeters on my start battery, main battery and generator battery and they all do give reasonably useful information specially on the start and generator batteries which are at rest for long periods with no discharge - the voltmeter DOES show if the battery is self discharging over time.

For power in from solar panels I would recommend a Watt meter as used by Radio Control plane fanatics

 

will add link in a minute

These things really are good They will give instantaneous amps, voltage, watts, accumulated Amp Hours and if you go for an 'Eagletree' version you can get a full data logger which will give you volts, amps, temperature in more than one place and other things measured every second for about a month before you need to download it onto the laptop

 

quite cool. I used one to take measurements of my solar output when I was using a tracker made with a satellite dish motor.

 

Also logged my fridge power consumption.

 

Probably a bit anoraky for most people

http://www.ebay.co.uk/itm/DC-LCD-60V-100A-Balance-Voltage-Boat-RC-Heli-Battery-Power-Analyzer-Watt-Meter-/390932345418?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item5b0562324a

Got one in the mail. Tomorrow will fit it and test it with my digital multimeter. I'm particularly interested to find out if the current readings are reliable, as it's fairly difficult (for me) to carry out a proper amp reading by disconnecting the wires, etc.

[Paul G2]

Thanks for your comments, they all seem to be positive. I hate typing on this ipad so will comment (and ask more questions) once i get a proper keyboard.

By positive i meant to the point lol. Getting a digital meter from argos now. The analogue i have not good for my decaying eye sight not lol.

 

I have one of these for my iPad. Great piece of kit! Light as a feather, fantastic battery, protects the screen, etc., etc.

 

 

 

[smileypete]

As mentioned in post #4 but the hint was not taken.

 

My bigger hint didn't seemingly wasn't taken either.

 

cheers, Pete.

~smpt~

Edited November 16, 2014 by smileypete

[magnetman]

 

I like the little watt meter because you can get accumulated power in and volts whenever you want. Clamp meter can also

be a bit tricky when 2 core wire is used as it needs just pos or neg or the reading would cancel itself

Edited November 16, 2014 by magnetman