measuring leisure battery voltage (1 Viewer)

[tomm]

The habitation control panel in our MH has simple needle readout dials for water and batteries , showing incremental empty, quarter//half etc . No voltage/amps etc shown for batteries . Apparently the needle readout dials are not particularly accurate and a more precise battery state could be of benefit.

Until we get round to delving into long term solutions for actually maintaining battery power , would one of these things give an accurate enough voltage reading for hab batteries , when put in one of the hab area 12 volt sockets fitted in MH ?

 

[icantremember]

would one of these things give an accurate enough voltage reading for hab batteries , when put in one of the hab area 12 volt sockets fitted in MH ?

Yes ... I have one I use in the cars sometimes.

 

[Two on Tour]

We use one of those on our last motorhome to give us an idea of the hab battery voltage and is a low cost simple solution.
I have now fitted a fancy bit of kit in our present camper which give more detail on battery percentage, amps/watts usage etc.

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[tomm]

We use one of those on our last motorhome to give us an idea of the hab battery voltage and is a low cost simple solution.
I have now fitted a fancy bit of kit in our present camper which give more detail on battery percentage, amps/watts usage etc.

Thats the way forward for us as well. The plug in battery voltage detector being a basic interim measure . Recent problems with our diesel heating actually highlighted the requirement for monitoring an accurate readout on hab batteries status ...As well as deciding to fit , in the near future , appropriate "gadgetry " to maintain engine and hab batteries at optimum levels ........ Am at the start of the delving around for gadgets

 

[Vanman]

The trouble I've found with these sorts of gadgets / meters is that they don't 'play well' with electrical equipment. If you have a solar panel fitted then even an empty battery will show 13-14v whilst it's charging. It's only an hour after everything else has stopped putting in, or taking out, that you can get a 'proper' reading. Hard to achieve when you are using the vehicle.

 

[hilldweller]

would one of these things give an accurate enough voltage reading for hab batteries

They might look accurate but unless you can check against a decent voltmeter do not trust one, says a man who bought a couple and although a good quick check they were not very accurate.

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[tomm]

The trouble I've found with these sorts of gadgets / meters is that they don't 'play well' with electrical equipment. If you have a solar panel fitted then even an empty battery will show 13-14v whilst it's charging. It's only an hour after everything else has stopped putting in, or taking out, that you can get a 'proper' reading. Hard to achieve when you are using the vehicle.

They might look accurate but unless you can check against a decent voltmeter do not trust one, says a man who bought a couple and although a good quick check they were not very accurate.

Points noted and accepted folks.
As briefly mentioned above , am looking for a interim workaround until moving on to fitting more accurate means of maintaining and measuring battery status...... That will no doubt be in another thread topic from me in the near future

 

[PhilandMena]

You may want to consider what your long term aim is rather than your short term aim in order to save money.......in the long term.
Many experienced motor homers fit a 'shunt' and appropriate meter which measures the true state of the battery and in particular, how many Amps are being taken out, put in, (at any given moment) and, how long to fully charge the battery and how long before it's discharged. One of the problems you will encounter when using a Volt Meter with reading a battery when the battery is in use, is that you will not get an accurate reading. This can only be achieved when there is no charge going into or out of the battery and it has been rested for a few hours. However, saying all that, a volt meter is better than nothing. Should you decide to go down the route of fitting a shunt, you will get loads of help from U Tube videos and fitting instructions are usually comprehensive and one can do it themselves. They even have Bluetooth models available now so no drilling and routing of cables to the display case. An example below.
http://www.nasamarine.com/product/bm-1-bluetooth/

 

[daveandsan]

I have one of those gadgets which I bought before I had our solar panel fitted and it is within 0.1 of a volt to the actual reading on my panel.

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[tomm]

You may want to consider what your long term aim is rather than your short term aim in order to save money.......in the long term.
Many experienced motor homers fit a 'shunt' and appropriate meter which measures the true state of the battery and in particular, how many Amps are being taken out, put in, (at any given moment) and, how long to fully charge the battery and how long before it's discharged. One of the problems you will encounter when using a Volt Meter with reading a battery when the battery is in use, is that you will not get an accurate reading. This can only be achieved when there is no charge going into or out of the battery and it has been rested for a few hours. However, saying all that, a volt meter is better than nothing. Should you decide to go down the route of fitting a shunt, you will get loads of help from U Tube videos and fitting instructions are usually comprehensive and one can do it themselves. They even have Bluetooth models available now so no drilling and routing of cables to the display case. An example below.
http://www.nasamarine.com/product/bm-1-bluetooth/

Weve only just taken the MH on a PX for our previous MH and the short term aim isn"t to save money , its until we get round to delving into long term solutions for actually maintaining battery power .

IE the gadget I showed the link to , is to have a basic and interim solution of even rough measurement of battery voltage . Which is still a lot better than our present innaccurate needle meter % system . This until such time as the onboard electrics have been fully checked out and appropriate modifications /additions decided and made to improve the batteries ( engine + leisure ) charging/conditioning /monitoring .

EG at the moment the solar panel only has a mono charging PWM regulator , so looking to probably changing that to MPPT dual .Also maybe fit a B2B charger or voltage sensitive/sensing relay etc .

As another measure of conserving power, am at the stage of ordering up LED to replace the halogen and PL fluorescents which are in the van at present and eating up battery power like no ones business .

 

[Richard n Ann]

I fitted a NASA BM2 battery monitor. Top quality, love it, in fact I think I look at it a bit too often... Ann's getting a bit worried

 

[Davylambretta]

Something like this any good to you if you look about ebay you can get them cheaper

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[pappajohn]

As you have a solar panel fitted the gadget in your opening post will be useless in daylight as it will show the solar charge voltage, not the true battery voltage.
The same applies if you're on hookup...charger voltage, not battery voltage.

 

[tonyidle]

As you have a solar panel fitted the gadget in your opening post will be useless in daylight as it will show the solar charge voltage, not the true battery voltage.
The same applies if you're on hookup...charger voltage, not battery voltage.

Battery and solar / EHU charger voltage are always the same. Voltage at rest is only available at the battery terminals with everything disconnected and then only after a period of stabilisation. The arrangement suggested by the OP used intelligently will do the job.

 

[PhilandMena]

Something like this any good to you if you look about ebay you can get them cheaper

In the picture, this is connected to a shunt! I assume this would have to be bought separately.

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[Vanman]

Battery and solar / EHU charger voltage are always the same.

Hmmm. My Solar panel outputs a whole range from 0 to 14+ I suspect that the only places they are constant is very sunny places in daytime and the dark side of the moon

As soon as the solar input exceeds the battery level then I believe a simple meter will only show the higher of the two.

 

[hilldweller]

I fitted a NASA BM2 battery monitor. Top quality, love it, in fact I think I look at it a bit too often... Ann's getting a bit worried

Ours is above the TV, it's often more entertaining than the TV.

 

[pappajohn]

Battery and solar / EHU charger voltage are always the same. Voltage at rest is only available at the battery terminals with everything disconnected and then only after a period of stabilisation. The arrangement suggested by the OP used intelligently will do the job.

Yes, but only if ALL charging sources are turned off....including the solar charger.

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[tonyidle]

Hmmm. My Solar panel outputs a whole range from 0 to 14+ I suspect that the only places they are constant is very sunny places in daytime and the dark side of the moon

As soon as the solar input exceeds the battery level then I believe a simple meter will only show the higher of the two.

If the meter is on the output of the solar regulator then it is reading battery voltage no matter what the solar panel, or any other charging source, is doing.

 

[Vanman]

If the meter is on the output of the solar regulator then it is reading battery voltage no matter what the solar panel, or any other charging source, is doing.

That's not my understanding of how it works ... if the battery is receiving power then it is that power that the meter will show, if the reading is taken off the battery or any circuit directly attached to battery

 

[tonyidle]

That's not my understanding of how it works ... if the battery is receiving power then it is that power that the meter will show, if the reading is taken off the battery or any circuit directly attached to battery

How what works? I am talking about using a simple digital voltmeter (or a multimeter) to measure voltage. If the meter is connected across any pair of wires, anywhere in the vehicle, that are connected to the battery positive and negative terminals, then it will read battery voltage. I am deliberately avoiding complicating the issue by not mentioning the effect of wire resistance and the voltage drop it may or may not cause.

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[mitzimad]

How what works? I am talking about using a simple digital voltmeter (or a multimeter) to measure voltage. If the meter is connected across any pair of wires, anywhere in the vehicle, that are connected to the battery positive and negative terminals, then it will read battery voltage. I am deliberately avoiding complicating the issue by not mentioning the effect of wire resistance and the voltage drop it may or may not cause.

im sorry to say you are wrong with my engine running it will show alternator output and when stationary it will show solar input only after dark will it show battery voltage and then it needs up to an hour to stabilise

 

[Richard n Ann]

How what works? I am talking about using a simple digital voltmeter (or a multimeter) to measure voltage. If the meter is connected across any pair of wires, anywhere in the vehicle, that are connected to the battery positive and negative terminals, then it will read battery voltage. I am deliberately avoiding complicating the issue by not mentioning the effect of wire resistance and the voltage drop it may or may not cause.

I suppose it's down to what you mean by battery voltage... The voltage across the battery terminals is different to the battery's resting voltage, which can be used to determine the state of charge.

 

[mitzimad]

I suppose it's down to what you mean by battery voltage... The voltage across the battery terminals is different to the battery's resting voltage, which can be used to determine the state of charge.

yes thats correct you need the resting voltage i couldnt think of the correct word for it

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[Dazzlin]

Ours has never run out. Hook up about twice a year but keep an eye on batt charge and state via BM1. 2 x AGM's & 4 x solar (another thread)
Bring it on....

 

[tonyidle]

I suppose it's down to what you mean by battery voltage... The voltage across the battery terminals is different to the battery's resting voltage, which can be used to determine the state of charge.

I made that statement earlier in the thread.

 

[tonyidle]

I suppose it's down to what you mean by battery voltage... The voltage across the battery terminals is different to the battery's resting voltage, which can be used to determine the state of charge.

I mean by battery voltage - Battery Voltage. The conditions under which it is measured will change the value of the voltage but it is still battery voltage. I made the point about measurement at rest earlier in the thread.

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[Richard n Ann]

I mean by battery voltage - Battery Voltage. The conditions under which it is measured will change the value of the voltage but it is still battery voltage. I made the point about measurement at rest earlier in the thread.

All we're doing then is wording it differently, but I don't think it's helpful to talk of battery voltage when measuring the solar charging voltage (which happens to appear across the battery terminals). I would say "voltage across the battery" but each their own.

 

[tonyidle]

All we're doing then is wording it differently, but I don't think it's helpful to talk of battery voltage when measuring the solar charging voltage (which happens to appear across the battery terminals). I would say "voltage across the battery" but each their own.

I agree it's semantics but it's important that there's no misunderstanding. The lowest resistance source (the battery) is what determines the measured voltage. It is influenced by what is connected to it (or not) but that is still what you see with your meter. Last week l helped friend who's solar system had stopped working. He believed that a meter across the solar regulator measured the output of the panels and a meter across the battery measured the battery voltage. So when he saw nothing across the regulator and 12.6v across the battery he thought his regulator had failed. He didn't realise that whether the solar regulator was working or not he should expect the same reading at both ends of the cable that linked it to the battery. (The fault turned out to be a parted connector in that cable).