Battery Volt and Amps Meter Advice Please

[jo10000_6]

Hi

Upon buying my little motorhome both Leisure and Cab Battery needed changing - chances are they hadn't been used that much and were ready to die.

Made me a bit paranoid so I do check both batteries often.

I have an auto electrician coming next week to do a couple of jobs and ideally I'd like a couple of battery monitors so at a glance I can see what's what without having to take the front cover of the engine - not a hardship but its fibre glass and ideally I never want it off to long because as careful as you are that's how accidents can happen and things get broken.

For the cab battery I'm quite happy with one of those little digital display things - but for the leisure battery (110 Amp) Id like one that shows Volts and Amps - you know a little bit more info on what's in and what's going out.

I have looked on eBay and Amazon but there are so many different options - different sizes I concerned about ordering the wrong thing so I thought it might be worthwhile asking what other people can recommend.

Any advice / recommendations appreciated.

Thanks
Jo

 

[Dazzlin]

NASA bm1 or 2.
They both show all the info you need, charge, discharge amps etc and you can connect your cab battery and get the voltage at the touch of a button.

Big numbers are easy to read as well

https://www.nasamarine.com/product/bm-2-battery-monitor/

 

[Richard n Ann]

We've got a BM2 as well, very good

 

[Ivory55]

Out of interest are the nasa monitor more accurate then the original equipment in the van like sergeant in an auto trail.

 

[PeteH]

Out of interest are the nasa monitor more accurate then the original equipment in the van like sergeant in an auto trail.

Accuracy depends upon location, primarily distance from the batteries, and the use of the correct size of cable (line loss can be considerable). Used to be that to accurately monitor Amperage the Cable need to be nearly as thick as the Starter cable!. Modern Electronics can mitigate this.

PS. I note from the technical description that the device monitors BOTH and uses known tried methods to compute with accuracy. It come with a set 5M of cable so will likely be calibrated to that length, and should not be lengthened or shortened to preserve that calibration? I also Noted that the Cost is relatively high!. Maybe just using a decent Digital Test Instrument is all that is necessary?

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[PhilandMena]

Out of interest are the nasa monitor more accurate then the original equipment in the van like sergeant in an auto trail.

I have the NASA Bluetooth fitted to my autotrail and they both more or less are giving the same readings with the exception of the NASA device providing more information.

 

[Ivory55]

I have the NASA Bluetooth fitted to my autotrail and they both more or less are giving the same readings with the exception of the NASA device providing more information.

Have you got the blown air heating or a gas fire, if blown do you find it knocks the batteries down if not on ehu?

 

[PhilandMena]

Have you got the blown air heating or a gas fire, if blown do you find it knocks the batteries down if not on ehu?

I have a Webasto heater. Never been serviced and still working although I now have a fault indicated on the status light so will probabbly need it to be looked at sometime later this year. The fan for the heating does use a lot of amps (10) but chucks out a lot of heat and I have to turn it down after 10 minutes as it's getting to warm in the van. When heating water it only uses around 3 to 4 amps and I suspect as I have never had it serviced the fan is drawing more amps than it should.
I have 2 new Excide 650 et lead acid batteries and 250 W of solar and I've only needed to put the heating on first thing in the morning when coming down through France and Spain and the very North of Morroco. So far, my batteries have not fallen below 80 % and most nights we watch a film from my laptop which is plugged into my inverter. There fully charged again in a few hours once the sun comes out. It was a bit chilly first thing this morning about 8 deg. But once the sun gets up it's scorchio time. Temp now is 20.3 deg and climbing. Yesterday was fabulous here and we could be in for anouther one of those days.

 

[Ivory55]

Sorry thought you had the blown gas heating that was standard. Yes a diesel heater does chuck out some heat. Not in our budget at present. Cheers.

 

[PhilandMena]

Sorry thought you had the blown gas heating that was standard. Yes a diesel heater does chuck out some heat. Not in our budget at present. Cheers.

Came as standard with motorhome.

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[PhilandMena]

We have been asked to leave parking along with several other motorhomes. Parking money returned and told it's official. Locals have complained about German couple who turned up with 4 dogs and built a pen for them next to motorhome. That's 5 wild dogs occupying this space and at least 5 more from motorhome owners. We have been here 5 days and many are telling us they are sad to see us go as we have got on very well with local people and hotel staff. Not to worry, it is what it is and that's life.

 

[Pausim]

I have a Victron BMV with bluetooth. I have left the display in the battery compartment and just use the app on my phone/pad to check, saves finding somewhere for the display and wiring.

 

[LesW]

We have been asked to leave parking along with several other motorhomes. Parking money returned and told it's official. Locals have complained about German couple who turned up with 4 dogs and built a pen for them next to motorhome. That's 5 wild dogs occupying this space and at least 5 more from motorhome owners. We have been here 5 days and many are telling us they are sad to see us go as we have got on very well with local people and hotel staff. Not to worry, it is what it is and that's life.

Wrong thread?

 

[Augusta08]

Wrong thread?

Two of the dogs are called Volts and Amps, but Watts in a name?

 

[jollyrodger]

Are they now returning ohm ?

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[xsparks]

Currently with resistance.

 

[Pausim]

Are they now returning ohm ?

Yes but they can’t get far a day.

 

[xsparks]

But Milihenry is creating some enducemen.

 

[autorouter]

For the cab battery I'm quite happy with one of those little digital display things - but for the leisure battery (110 Amp) Id like one that shows Volts and Amps - you know a little bit more info on what's in and what's going out.

I have looked on eBay and Amazon but there are so many different options - different sizes I concerned about ordering the wrong thing so I thought it might be worthwhile asking what other people can recommend

There are two types of devices that are sold as 'battery monitors'.

One type is a simple voltmeter/ammeter that simply gives the volts and amps at the time you are looking at it. They are much better than nothing, but voltage is not a good indication of state of charge, especially when there's a solar panel and/or there is any kind of load on the batteries.

The other type is better, more complex and more expensive. A 'shunt' is wired into the main cable, usually right next to the batteries. A pair of thin wires goes to either side of the shunt. This measures amps very accurately. The battery monitor reads the amps continuously, and internal software adds up and subtracts the charge as it goes in and out of the battery. Once set up, this method is more accurate than the voltage method, and also gives an accurate charge level even during charging and discharging. The NASA BM types are like this, as are the Victron BMV types.

 

[JeanLuc]

A battery computer will give the most accurate information and the Victron is well regarded. I don’t have one but when I considered fitting a monitor a couple of years back, Votronic was recommended by Schaudt who make the charging system used in many motorhomes including Hymer. (Might get around to fitting one some day.)
https://www.roadpro.co.uk/product/0...ttery-computer-100s-smart-shunt-c8507a/C8507A

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[jo10000_6]

Hi All - Thanks for replies.

I've looked at the NASA BM1 and you are right does everything I need it to - but its a little bit pricey - the only reason I say that is at some point I'd like solar and I'm fairly sure (not totally) that if I buy the right kit for that this will also tell me this information as well and then the battery monitor - other than doing a double check on the figures will be an expensive display.

Accuracy depends upon location, primarily distance from the batteries, and the use of the correct size of cable (line loss can be considerable). Used to be that to accurately monitor Amperage the Cable need to be nearly as thick as the Starter cable!. Modern Electronics can mitigate this.

PS. I note from the technical description that the device monitors BOTH and uses known tried methods to compute with accuracy. It come with a set 5M of cable so will likely be calibrated to that length, and should not be lengthened or shortened to preserve that calibration? I also Noted that the Cost is relatively high!. Maybe just using a decent Digital Test Instrument is all that is necessary?

I am testing via the multimeter - but more 110 amp battery is discharging quicker than I think it should and Id like to know where from - and I don't know how to test individual items - I've done the on paper calculation of what it should discharge when used.

I suppose I could get the auto electrician to show me how to do some things next week.

Have you got the blown air heating or a gas fire, if blown do you find it knocks the batteries down if not on ehu?

I have blown gas heating and haven't used it much but the product book for it says 0.2-1.0 Amps Per Hour - which I'm assuming is form having it on low to full pelt - I didn't think that was bad considering I'd heard that this can eat into your 12V battery but perhaps I've misread it !

There are two types of devices that are sold as 'battery monitors'.

One type is a simple voltmeter/ammeter that simply gives the volts and amps at the time you are looking at it. They are much better than nothing, but voltage is not a good indication of state of charge, especially when there's a solar panel and/or there is any kind of load on the batteries.

The other type is better, more complex and more expensive. A 'shunt' is wired into the main cable, usually right next to the batteries. A pair of thin wires goes to either side of the shunt. This measures amps very accurately. The battery monitor reads the amps continuously, and internal software adds up and subtracts the charge as it goes in and out of the battery. Once set up, this method is more accurate than the voltage method, and also gives an accurate charge level even during charging and discharging. The NASA BM types are like this, as are the Victron BMV types.

Thanks for this - Yes I'm beginning to see its going to be a really good one or perhaps not worth having. I've seen some shunt types from China but you could never guarantee their accuracy over a tried and tested product.

A battery computer will give the most accurate information and the Victron is well regarded. I don’t have one but when I considered fitting a monitor a couple of years back, Votronic was recommended by Schaudt who make the charging system used in many motorhomes including Hymer. (Might get around to fitting one some day.)
https://www.roadpro.co.uk/product/0...ttery-computer-100s-smart-shunt-c8507a/C8507A

Thanks Jean-Luc also looks good.


Thanks all - really appreciate the answers - I may have to muddle through with the multimeter for a while - I don't mind spending the money but have to rein myself in sometimes when I know my little motorhome will be upgraded sometime in the future.

 

[Pausim]

I've looked at the NASA BM1 and you are right does everything I need it to - but its a little bit pricey - the only reason I say that is at some point I'd like solar and I'm fairly sure (not totally) that if I buy the right kit for that this will also tell me this information as well and then the battery monitor - other than doing a double check on the figures will be an expensive display.

I have have a solar system that tells me battery volts and amps produced by the panels but it does not tell me what is actually going in and out of the battery. My Victron BMV gives far more useful information. Some of the solar output will never reach the battery, running the 12v systems, losses in wiring etc. The Victron BMV also has adjustable settings (I guess the NASA one does too but worth checking) to reflect the battery type. Lead acid batteries are generally only 95% efficient when charging, 5% of the amps are lost. There is also a factor known as Peukerts Exponent that affects how much power is left in the battery after heavy use. A good battery monitor will allow for these factors and should give a much better idea of what is going on. I would much prefer the battery monitor and wish I hadn’t bothered with the solar display, it only gives part of the story.

 

[jo10000_6]

Thank you - I think I needed it clearing up whether solar kit was just going to double up.

Appreciate the reply.

Jo

 

[jo10000_6]

If I buy a good battery monitor is it easily removed upon changing to a new motorhome ?

 

[busby]

Sorry thought you had the blown gas heating that was standard. Yes a diesel heater does chuck out some heat. Not in our budget at present. Cheers.

Some cheap Chinese ones,,BUSBY,

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[maxi77]

I have have a solar system that tells me battery volts and amps produced by the panels but it does not tell me what is actually going in and out of the battery. My Victron BMV gives far more useful information. Some of the solar output will never reach the battery, running the 12v systems, losses in wiring etc. The Victron BMV also has adjustable settings (I guess the NASA one does too but worth checking) to reflect the battery type. Lead acid batteries are generally only 95% efficient when charging, 5% of the amps are lost. There is also a factor known as Peukerts Exponent that affects how much power is left in the battery after heavy use. A good battery monitor will allow for these factors and should give a much better idea of what is going on. I would much prefer the battery monitor and wish I hadn’t bothered with the solar display, it only gives part of the story.

I would agree a decent monitor will tell you what is going in and out and give a decent idea of what is left. Volts when on load are not that helpful most of the time but can have some use when charging.

 

[Pausim]

If I buy a good battery monitor is it easily removed upon changing to a new motorhome ?

Yes easily removed, particulary if you have a bluetooth one and don't bother to permanently mount the display in the cabin. If you are thinking about future prroofing your purchase worth checking that it can be adjusted for all battery types, including lithium.

 

[Lenny HB]

I have the Victron BMV700 very pleased with it. I went for the Victron rather than the cheaper NASA BM1 or BM2 as there were so many reported problems of the BM's giving inaccurate readings when you have solar panels, it may have been fixed now.

 

[PeteH]

I wouldn't get too hung up on this. Most modern vehicles have "ghost" drains. Electronics clocks etc: But a good set of batteries, Nothing wrong with Lead acids, just get the right capacity for your usage, and proper ventilation. Even some alternators can be "upgraded" too. Solar Panels are a worthwhile addition unless you park in dark sheltered places you will get some payback even it the depth of winter, basically you only really need to know if the Battery is charging or discharging. switching off unused kit, and replacing the Lighting with LED`s will make a real difference. Older kit is more energy hungry unfortunately often relying on Rheostats for speed control rather than the later electronic controllers, for example.