Battery condition (1 Viewer)

[Ivory55]

On our panel in the auto trail it shows volts in the batteries and amp hours. The volts can show 12.4 v yet the amp hours remaining 100% is this normal ? Cheers

 

[PhilandMena]

Possibly. You have a load placed on your battery hence the 12.4 V reading. Impossible to accuratly ascertain the state of the battery when there is a load on it. Isolate for a few hours then measure with a digital Volt meter. However, this will not tell you what your capacity state is.

 

[Ivory55]

Cheers, this 12v is a black art. Haha

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[autorouter]

You say the panel shows amp-hours in percent, but does it also the current (amps)? If the current (amps) is low, maybe the battery is no good, or the voltage reading is inaccurate.

 

[Ivory55]

I hope it’s the panel as batteries only a year old. It shows volts and battery amp hours.

 

[SMB]

My BM1 monitor shows battery percentage remaining, hours it will take to charge with current input of power, voltage and charge/discharge rate. At the moment it is showing 90% remaining at 12.8v with no solar or charge. I have 4 x 95a wet batteries which probably doesn't help, I only really take notice of the voltage and charge/discharge rate.

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[autorouter]

First thing to do is get a voltage measurement of the battery terminals using a multimeter. Then you can see if it's the battery, or a problem with the wiring like a bad connection, or an inaccurate panel display. If you can't get at the battery itself, go as near as you can to it - the isolator switch or the fuse for example.

 

[PhilandMena]

My BM1 monitor shows battery percentage remaining, hours it will take to charge with current input of power, voltage and charge/discharge rate. At the moment it is showing 90% remaining at 12.8v with no solar or charge. I have 4 x 95a wet batteries which probably doesn't help, I only really take notice of the voltage and charge/discharge rate.

Please explain how this answers the original questioners enquiry. It's gone right over my head. No surprise as I'm quite thick.

 

[PhilandMena]

On our panel in the auto trail it shows volts in the batteries and amp hours. The volts can show 12.4 v yet the amp hours remaining 100% is this normal ? Cheers

I too have an Autotrail. I'm fairly certain you are ok. Be careful of members who with the best intent accidently mislead you. This forum is full of experts who disagree with each other.

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[autorouter]

Please explain how this answers the original questioners enquiry.

In summary, he has a battery at 90% charge with a voltage of 12.8 volts. That's more like what most people would expect if the battery is fully charged, or very nearly so.

I too have an Autotrail. I'm fairly certain you are ok. Be careful of members who with the best intent accidently mislead you. This forum is full of experts who disagree with each other.

I think 12.4V for a fully charged battery is suspiciously low. Is it the kind of reading you expect on an Autotrail display panel?

 

[PhilandMena]

In summary, he has a battery at 90% charge with a voltage of 12.8 volts. That's more like what most people would expect if the battery is fully charged, or very nearly so.

I think 12.4V for a fully charged battery is suspiciously low. Is it the kind of reading you expect on an Autotrail display panel?

I was Right! I'm totally out of my depth. Where did the OP state his battery was at 12.8 V and how does this equate to 90 % charge. If you put a load on a fully charged battery and measure it', you will not get a true reading, this is common knowledge. The battery needs to be disconnected and allowed to rest before ascertaining its true state. Thete are plenty of threads on here that agree with this.

 

[autorouter]

Where did the OP state his battery was at 12.8 V and how does this equate to 90 % charge.

The OP has a battery at 100% with a voltage of 12.4V:

The volts can show 12.4 v yet the amp hours remaining 100%

@SMB says his battery is at 90% with a voltage of 12.8V:

At the moment it is showing 90% remaining at 12.8v with no solar or charge.

I said that 12.4V was unexpectedly low for a 100% charged battery. There are a number of possible causes, one of which, as you say, is that maybe there is a load on the battery pulling down the voltage.

Other possible causes are bad connections, bad earthing, inaccurate panel meter, and a few other even less likely but possible faults.

My view is that the first thing to do is to check that the actual battery voltage really is 12.4V, by measuring the voltage at the terminals. I have no experience of Autotrail, so it's likely that others with more experience will have better ideas.

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[Reallyretired]

My panel meter is pretty inaccurate reads 0.5v low compared with an accurate voltmeter on the batteries This is on a Rapido

 

[Ivory55]

What I will do is wait till I see the mobile fitter or someone who knows how a meter works and check it, mean time I will just carry the generator with me. Cheers ( bloody 12v makes home electric seem so simple, haha)

 

[PhilandMena]

The OP has a battery at 100% with a voltage of 12.4V:

@SMB says his battery is at 90% with a voltage of 12.8V:
I have no experience of Autotrail, so it's likely that others with more experience will have better ideas.

Like me perhaps!

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[gus-lopez]

Mine does it other way round.Display tells me battery is at 12,4 v at rest with habs @12,9v.
just dodgy wiring connection as when metered ,the van batt is at 12,78v & leisures always show at 12,9v at night.

 

[SMB]

Please explain how this answers the original questioners enquiry. It's gone right over my head. No surprise as I'm quite thick.

It doesn't answer anything, I was trying to illustrate how inaccurate some battery monitors are. Thats why I said I only take notice of the voltage and charge/discharge rate, there's too many factors to the readings to believe the accuracy of the monitor. I also have little idea of electrics amongst other things

 

[PhilandMena]

It doesn't answer anything, I was trying to illustrate how inaccurate some battery monitors are. Thats why I said I only take notice of the voltage and charge/discharge rate, there's too many factors to the readings to believe the accuracy of the monitor. I also have little idea of electrics amongst other things

Thank you for your input on this thread. I'm of the view a battery monitor (with a shunt) is the only way of measuring a battery state in real time with confidence. If there is another device that will do this and can be permanently connected to the batteries, I would be interested in knowing about it.

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[Richard n Ann]

Just been out and measured ours, 13.71v on the battery 13.8 on the BM2 (BM2 resolution only 100mv steps) so very close.

I wanted to test the accuracy of the BM2 because in the evening when not charging the battery stays at 12.9v for a long time even with the TV taking 2 amps must be a characteristic of our Yuasa battery?

I've only been obsessive about lead acid batteries for about 4 years so don't have experience with any others

 

[autorouter]

Thank you for your input on this thread. I'm of the view a battery monitor (with a shunt) is the only way of measuring a battery state in real time with confidence. If there is another device that will do this and can be permanently connected to the batteries, I would be interested in knowing about it.

Some battery monitors need to be set up correctly. For example, if it was set up for one battery, and he added a second battery without changing the settings, it could be reading 100% even though they were only half charged,

 

[funflair]

Thank you for your input on this thread. I'm of the view a battery monitor (with a shunt) is the only way of measuring a battery state in real time with confidence. If there is another device that will do this and can be permanently connected to the batteries, I would be interested in knowing about it.

I find an inverter and van voltmeter quite good for measuring battery state of charge, turn it on with the coffee machine on and if the volts goes under 12.6 the batteries were not full

Martin

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[SMB]

Some battery monitors need to be set up correctly. For example, if it was set up for one battery, and he added a second battery without changing the settings, it could be reading 100% even though they were only half charged,

The monitor was set for four batteries and when i bought new batteries I reset the monitor as the available amps was slightly less. I just think that the monitor readings can be misleading, having read some reviews of the BM-1 online others have said the same. Its still handy for indicating how many amps individual items use

 

[PhilandMena]

I have the BM-1 battery monitor and it seems to be accurate, as far as I can tell. Little to no difference between read out on Autotrail control panel and digital volt meter. They cant all be wrong.

 

[SMB]

I contacted the manufacturer a few weeks ago as when the backlight of the unit is illuminated the charge rate rises dramatically until the backlight goes off. They thought it was a problem with the shunts and recommended cleaning them which I did. This had no effect but I'm not too bothered, its just more annoying than anything else. I've had the unit a few years now and it still works, I just don't take much notice of the percentage reading.

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[autorouter]

I contacted the manufacturer a few weeks ago as when the backlight of the unit is illuminated the charge rate rises dramatically until the backlight goes off. They thought it was a problem with the shunts and recommended cleaning them which I did.

The battery current (amps) passes through the big terminals on the shunt. The shunt is a very small but very accurate resistance. There is a tiny voltage across it when a current flows.

The panel measures the current (amps) by reading the tiny voltage, using the two small terminals on the shunt, and two thin wires going all the way back to the display.

If there is any problem with the connections of the thin wires, they can pick up tiny stray voltages which will significantly change the current it thinks it is reading.

The first thing to do is make sure the shunt terminals are clean and tight, as the manufacturer has said. If it's not that, check the thin wires all the way to the panel. Especially where they actually reach the panel. If all the connections are good, then maybe it's a faulty circuit board - a bad solder joint or a cracked track. The change in reading when the backlight is on is very suspicious.

 

[andy63]

They thought it was a problem with the shunts

Hi.. I reckon the best way to check your battery monitor is giving a resonable indication of battery capacity is to check the current reading at a known rate and that's usually with no load and no charge.. ie 0 amps..
If you have a a known and trusted ammeter you could do it again at a known rate and compare the readings...
I had a Stirling power management panel that used to indicate about 2 amp hours of charge over a 12 hour period that was obviously rubbish...
Stirling sent me the instructions on how to calibrate the electronic circuitry that aggerates the battery capacity... so thats another possible cause of monitors not been correct on the battery capacity even if the wiring is sound..
Andy.

 

[SMB]

Thanks for the advice @andy63 and @autorouter, I will have another go at it and see if it can be corrected

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