Setting up a Battery Monitor - Peukert's Law?

jagmanx

Full Member
As low as 12.7V? battery recovers to 12.8V when the heating is off? I would be inclined to check your voltmeter against another one!

As far as OTT for most of us, maybe, but more and more people are looking at going Electric (just look at the 'Electric Car' topic!) and to get the optimum use for a Battery Bank, you have to know what is available.
This is posted in the Forums '... Technical Section' also.
Simple answer ... Not Interested, Don't Read? (I take that approach in the "Jokes" section as I am a boring old fart)
I posted that I did not wish to be rude... Your reply borders on that !
I have read you other posts with interest....( and this one ) it is a shame you do not appreciate other opinions !
I did not contradict anything you posted I just offered my take on it
I have used this system to monitor my LB for the lats 3 years without problem
Ok I have not posted detailed voltages/monitoring etc but IT WORKS !.
Why do you suggest the reading is inaccurate when you have NO knowledge of my setup.
 

wildebus

Full Member
I posted that I did not wish to be rude... Your reply borders on that !
I have read you other posts with interest....( and this one ) it is a shame you do not appreciate other opinions !
I did not contradict anything you posted I just offered my take on it
I have used this system to monitor my LB for the lats 3 years without problem
Ok I have not posted detailed voltages/monitoring etc but IT WORKS !.
Why do you suggest the reading is inaccurate when you have NO knowledge of my setup.
sorry if you read it that way - not as intended. The way I read your post was as if I am wasting your time by you reading this thread, so simply suggested you didn't bother.

The knowledge I have assumed of your setup from your post is that you have a 12V Battery (or Batteries). That I think is likely to be correct?
A 12V battery is generally regarded as full if the voltage is sitting at around 12.7V or greater. The way you have described it, you have a full battery always despite using it and your voltmeter still shows it full even at that time. And when you remove a load from the battery the reading goes up. This seems quite remarkable to be and leads me to wonder if your voltmeter is misreading high and to confirm it might be worth checking it against another voltmeter/multimeter
 

Okta

Full Member
I do not wish to be rude..
But this is totally OTT for most of us !
I know you are "Electric only" so of real interest to you.
I monitor my LB voltage and late evening it some times gets as low as 12.7
I am happy with this..
If I turn heating off when it is dull at night the Voltage may go up to 12.8 as the battery recovers
Good enough for me...why overegg it ?

Winter use is different !
Somehow saying you don’t wish to be rude suggests you know what you are about to say is likely to cause offence. You might think the post OTT but you didn’t start it, Wildebus did, and I for one am interested. If it is of no interest to you why not just ignore it?
 

jagmanx

Full Member
See my earlier post with the PS.
We are very careful with our single battery having had the previous one DIE.
Out 120Watt Solar panel seems (as per my post) to maintain it very very well..
As I posted Summer Only
 

jagmanx

Full Member
Somehow saying you don’t wish to be rude suggests you know what you are about to say is likely to cause offence. You might think the post OTT but you didn’t start it, Wildebus did, and I for one am interested. If it is of no interest to you why not just ignore it?
I am interested.. just suggesting..
NO wish to be rude but my post was conflicting the OP
PS i do not see that an opposing rational view is in anyway rude !
 

Okta

Full Member
I am interested.. just suggesting..
NO wish to be rude but my post was conflicting the OP
PS i do not see that an opposing rational view is in anyway rude !
An opposing rational view is fine. I was reacting to “OTT” and “overegg” which didn’t read that way to me, however that is just my view which clearly differs from yours.
 

wildebus

Full Member
I had missed your more recent post and can see that 1.25 might be high, I will be interested to see your results at 1.1.
Done the tests at 1.1 now :)
The water in the heater tank will be different to the first test so the actual run time will be different. While the heater is on, the power drawn is the same though so we can just use maths to do the check and comparisions.

Quick reminder and some initial set points ...
Battery Bank is set at 380Ah@C20 (4 batteries at 95Ah each).
Quick recap on this @Cxx value. What this is saying that how much capacity the battery has for a different current draw. So a 110Ah battery @ C100 means if you pull 1.1A for 100 Hours, it will give 110Ah. And 95Ah@C20 means if you pull 4.75A for 20 Hours, it will give only 95Ah due to the higher current - this is the Peukert effect.

Batteries are fully charged and SOC is reading 100% at the start of each test.
Apart from heater (and inverter), the other load is a Victron Inverter driving a Network router and an amp or so being pulled.
The Water Heater is setup that it is on a 60 second ON, 120 second OFF repeat cycle.
When the Heater is ON, there is a pull of 180A from the battery for one minute. If we just take the battery as a constant 12V for the purpose of the calculations, then each ON period means 3Ah taken out the batteries (180A/60)

From Cold, the heater is always on for over an hour to get to max temp, so I took the charts and after exactly 1 hour running (20 ON periods and 20 OFF periods), cross-referenced against the monitor provided SOC reading


For Peukert Factor set at 1.25
Power Drawn is 20*3Ah = 60Ah
SOC is 72.2%
This gives the Battery Bank as having a Effective Capacity of 216Ah - so 54Ah per battery if we look at a per battery view
The Battery is quoted as 110Ah@C100 & 95Ah@C20, and would be 54Ah@C3.6 i.e. if you had a constant load of 15A it would last 3.6 Hours until totally depleted.

For Peukert Factor set at 1.1
Power Drawn is 20*3Ah = 60Ah
SOC is 79.6%
Now this gives the Battery Bank as having a Effective Capacity of 280Ah this time - so 70Ah per battery if we look at a per battery view. A signficant difference.
The Battery is quoted as 110Ah@C100 & 95Ah@C20, and this time would be 70Ah@C4.7 i.e. if you had this constant load of 15A it would last 4.7 Hours until totally depleted.

For Peukert Factor set at 1.0 (i.e. None). Now this one is purely calculated and I *think* you would see if you were setup for a Lithium Battery config in the monitor.
The calculation would be:
Power Drawn is 20*3Ah = 60Ah
The SOC with no Peukert Factor would be 84%
as there is no Peukert Factor the battery would remain at 95@C6.3 i.e. with a constant load of 15A, the battery would last 6.3 Hours until dead.


the "C" number varies as does the capacity for each of our examples - reason is that our Load is constant (this 15A per battery per hour) and what that does to the battery changes depending on the Peukert factor - and the 'rules' say that the correct Peukert factor varies depending on the battery technology.
So for our constant load, our 95Ah@C20 battery changes as follows
1.25 Peukert - 54Ah@C3.6
1.1 Peukert - 70Ah@C4.7
1.0 Peukert - 95Ah@C6.3

Which is right? who knows :)
Oktas comment about Victron Products is spot on and I am not dimissing them at all (quite the contrary - they are my 'go to' manufacturer where possible). I just have my doubts that so much capacity is really lost when pulling higher current, But I do think some is lost due to the battery heating internally, transferring to the casing and that heat escaping.

I will do one more run in next day or so with BMV Peukert at 1.0 just as a final check against my calcuated version, and ultimately I think for my own setup I will be probably setting the Peukert Factor ABOVE 1.0 - but not to the 1.1 Victron recommend - maybe just 1.02 to account for heat losses and a nod to Wilhelm Peukert, who knew far more about batteries than I ever will :)

For anyone who made it this far, I hope this was of interest. I was learning myself as I was doing the testing :)

I think this might have helped to work out how long your battery bank will really last (but as always, the least strain on the bank, the better for the long-term longevity of the bank, not just the day-to-day running time).

And of course, all the battery capacities quoted above are for 100% depletion - and depending on the battery you have, remember just 50% of that capacity may be the maximum available to you in many (most?) cases, with just a few batteries allowing for a safe depletion down to 60%, 80% or occasionally nearly 100% (for Lithium and the Victron Super Cycle AGMs for example)
 

Beemer

Free Member
As a mere amateur at motorhome electrics, I am keen to learn, so read your post with interest, although got lost eventually.
I was very interested to learn that you thought that after switching off a load, it would be strange that the voltage reading would rise.
I also see this voltage rise after switching off a "load", usually only up one volt. is this not normal?
 

wildebus

Full Member
As a mere amateur at motorhome electrics, I am keen to learn, so read your post with interest, although got lost eventually.
I was very interested to learn that you thought that after switching off a load, it would be strange that the voltage reading would rise.
I also see this voltage rise after switching off a "load", usually only up one volt. is this not normal?
This is with reference to my comment to jaxmanx?
Voltage rising up again after removal of a load is normal indeed and exactly what should happen. One volt would be rather a lot unless you removed a very heavy load though (0.1V is pretty typical)

What I was saying in my comment to him (clearly badly it would seem) is that the battery is starting up from an already fully-charged position and to rise futher that much (kind of above the 100% level), when there is no charging happening is strange and while the pattern is right, the actual values seemed too high IMHO - hence comment about checking voltmeter calibration.
Reading his post again he said "If I turn heating off when it is dull at night". Now I took that to say it was dark. but that was my interpretation . And of course in the summertime, it can be light at night :D Where I am, in the height of summertime, I get some solar harvesting at 10PM. So 'dull at night' could actually be providing a touch of charging still all this time and keeping the batteries at a higher level then a non-charge would be (and so voltmeter showing right)
 

wildebus

Full Member
I ran the final test today - Peukert Factor set at 1.0 - and thought would be interesting to compare the monitor results with the directly calculated ones below.

So to recap the calculated one
For Peukert Factor set at 1.0 (i.e. None). Now this one is purely calculated and I *think* you would see if you were setup for a Lithium Battery config in the monitor.
The calculation would be:
Power Drawn is 20*3Ah = 60Ah
The SOC with no Peukert Factor would be 84%
as there is no Peukert Factor the battery would remain at 95@C6.3 i.e. with a constant load of 15A, the battery would last 6.3 Hours until dead.
And the BMV Results
For Peukert Factor set at 1.0
Power Drawn is 20*3Ah = 60Ah
SOC reported is 83.9% - so near enough an exact match to the directly calculated one - which makes sense as the BMV will be doing just what I have done.
This time I remembered to look at the other Battery Monitor I have fitted and the SOC values directly matched between the monitors. That monitor has no place (that I have noticed) to apply a Peukert factor but not (IMO) a significant flaw.

I put the SOC results v. Peukert Factor in a chart and it is pretty well a straight line.


The alogorithm looks pretty simple and I bet if I ran the same test again with another Peukert Factor setting, the result would sit on the line or a straight extension of it.
As mentioned, I plan to settle on an Factor of 1.03 and I will predict that if I re-ran the same load test, the SOC reported will be 82.6% (I might do that test in the next day or so I think just to see)
The difference between 84% and 72% is actually pretty massive - that is a gap of 12% in terms of absolute battery capacity. If you want to avoid going below 50% capacity on your battery bank (a typical recommendation), then the difference becomes dramatic...
Peukert Factor =1.0 ==> using 16% (100% - 84%) of your whole battery means you have used 32% of the usuable capacity - nearly 1/3rd of what is available.
Peukert Factor =1.0 ==> using 28% (100% - 72%) of your whole battery means you have used 56% of the usable capacity -

If I have done my maths right, that is 75% more usable capacity used up when a Peukert Factor of 1.25 is applied compared to a 1.0 (no Peukert factor) (Note: This is for the specific fairly high load in my test remember).

So whatever your feeling is regarding the validity of the Peukert Exponent, the value of that entry in a battery monitor can make a major difference to what the monitor will be telling you (rightly or wrongly!) in terms of your remaining battery charge.

If you trust the principle of the Peukert Effect and you are a big Inverter user, then the numbers above could point you very strongly to looking at a Lithium Battery setup - as 1) they have no Peukert effect and 2) the full capacity is available. So if you were to work out the £ per Availble Ah cost, you would probably have to compare a 100Ah Lithium battery against something like a 300Ah Wet Cell battery as equivalents.
(For myself, I am not that convinced on Peukert so would still find Lithium still too much money for the benefit in my own rig)
 

chas142

Full Member
Well what a topic, as an ex Auto Electrician I found it very informative and useful, I am looking at my set up at the moment, the topic for many people goes well beyond what they need or want to know and comment have been exchanged and debated. But I have read every post and I suspect many others have as well, that's good because its turned into an informative debate.

When I was at collage some 45 years ago our training on batteries was basic, I was the only Auto Electrician all the other students were Mechanics getting an extra collage day off work for a year. That training was, It's a battery, it's got plates and acid inside, there is a chemical reaction inside and that all you need to know. The instructor was a mechanic he used to ask me on occasion how it was done where I worked.

Things have moved on as in those days you checked charge level by using a hydrometer in each cell, you could do a discharge test, and a charge test and we could check overall voltage and individual cell voltage by a cadmium meter cell test.

I think quite often thing are not as was thought previously and it's quite often the case that you have to check things more than once and with different tools or to different standards to fully understand what is going on. This is something I have done all my life if it interest me. Some people see it as obsessive and just don't understand why you don't think like they do.

On my part it is believed I have Asperger Syndrome, waiting for the test. That is what the Psychologists think in any case. So I liked the topic and the debate.

This Syndrome makes me look at things in a different way, so I noted that you said something like in another test the water wasn't the same water, and gave out all the data, correct me if I am wrong but it wouldn't matter if the water was the same tank full or a fresh tank full, as far as I am aware it would take the same amount of energy to heat the water AS LONG as the start and finish temperature of the water was the same and of course you used the same format of one minute on and two minutes off. Interesting and logical the way you have done that. However, I would have thought that as the batteries had all those separate two minute recovery section that, that would have improved your SOC reading above what was expected. Battery recovery may well not show in voltage reading in that short period of time but may be in the wings if you like making a slowly slowly approach.

I am buying a different, (dual), battery monitor to yours and I am considering replacing my 18 year old Gel Battery, but will test my system using various gauges and monitors to ascertain exactly where I am now and where I get to. Opps I might be classed as a Geek, is that good or bad?

In this post I am not trying to be rude, difficult, nasty, horrid or any thing else. Just enjoying myself. I know I should get out more;)
 

wildebus

Full Member
Hi, and thanks for the post :)

I don't know if I have some kind of syndrome myself but if you believe in the Zodiac and the Chinese Horoscopes, I really do seem match what I am supposed to be (Capricorn and a Metal Ox)
"Characteristics of the Metal Ox:
This Ox is certain and very strong willed. They can be blunt and direct in their views and is not afraid to say what they have to say. This Ox can get heavily involved in their objectives and goals which makes them unaware of other people’s thoughts and feelings at times."


Anyways, you make some interesting points which I have included in the snippets of the quote below which I think it would be worth replying to for clarity and extra info (y)

....
This Syndrome makes me look at things in a different way, so I noted that you said something like in another test the water wasn't the same water, and gave out all the data, correct me if I am wrong but it wouldn't matter if the water was the same tank full or a fresh tank full, as far as I am aware it would take the same amount of energy to heat the water AS LONG as the start and finish temperature of the water was the same
Agreed. it may have been the way I wrote it, but it is only the water temp which is the key. For these tests I set the heater to MAX (I would usually just use ECO in actual use) and left enough time to cool (or ran some cold water through) to ensure the heater would need to be on for over an hour minimum to heat back to MAX - that way I could always take a slice of an hours operation for comparision purposes.
As an aside (and nothing to do with the test), the way the heater seems to like to work is once up to temp the heater element goes off and then once the 'restart temp' is reached, it kicks on again, but only for a few minutes to put back what heat was lost over the previous 5 hours or so. so in real use it is on for one hour, then on for much shorter times every few hours after that.

and of course you used the same format of one minute on and two minutes off. Interesting and logical the way you have done that. However, I would have thought that as the batteries had all those separate two minute recovery section that, that would have improved your SOC reading above what was expected. Battery recovery may well not show in voltage reading in that short period of time but may be in the wings if you like making a slowly slowly approach.
Now this is an interesting observation you make here. This chart I think will answer your last thought? (I wasn't actually intending to show any charts but this seems to have the info you were wondering about?)

Heater VandC
by David, on Flickr
The Blue Line is the voltage. You see it immediately rises back up when the load is removed, as you expect, but then you see it recover futher just as you would expect a battery to do once you know something about battery chemistry.
Now having an improved SOC due to the 2 minute recovery periods. I have to agree with you there and I think this is where the Battery Monitors seem to fall down a little. They are instant point-of-time devices and don't (as far as I can tell) any kind of averaging/smoothing/retrospective algorithm.
I suspect that if I had a straight 20 minutes on, rather than 20 minutes on over a 60 minute window, the SOC would have ended up exactly the same (and I *think* it should not be the case for the same thinking as you?)
Now to be fair to the makers of them, the way I am using my system is not that typical by any means and it is impossible to them to cover every possibility and variation. Plus because of the brilliant Victron BMV and Victron GX software, I do have all this data on a minute-by-minute basis available to me to analyse which is fantastic for my inner Geek :geek:

I am buying a different, (dual), battery monitor to yours and I am considering replacing my 18 year old Gel Battery, but will test my system using various gauges and monitors to ascertain exactly where I am now and where I get to. Opps I might be classed as a Geek, is that good or bad?

In this post I am not trying to be rude, difficult, nasty, horrid or any thing else. Just enjoying myself. I know I should get out more;)
I read your post in - I am sure - just the way it was intended. And hopefully my reply will be seen in the same way also :)
 

bjh

Full Member
Having built an electric car and fitted 6 150Ah (C20 rating) deep cycle batteries in series, I believe Peukert. I think the problem maybe that the battery chemistry comes into play. After doing a discharge cycle there are probably localised effects around the plates, especially with a gel battery, where the electrolyte is rather more viscous. Letting them rest for a while would allow these local effects to dissipate and even out. With my "wet" batteries, I take up to 200 Amps at times and normally run about 70 to 100 Amps. This sort of current draw has definitely effected capacity and reduced the calculated range from about 45/50 to just under 30 miles. I forgot about Peurkert!!! Should have gone for Lithium Ferrous Phosphate (LiFePO), the constant is almost 1, so the capacity is only slightly reduced. The batteries would have been about one third the weight, giving me even more range. Unfortunately my pocket would have been very much lighter :)- I am pleased though with the life of the batteries, I was expecting maybe two years, but they are still going strong after four and a half years.
 

chas142

Full Member
Hi, and thanks for the post :)

I don't know if I have some kind of syndrome myself but if you believe in the Zodiac and the Chinese Horoscopes, I really do seem match what I am supposed to be (Capricorn and a Metal Ox)
"Characteristics of the Metal Ox:
This Ox is certain and very strong willed. They can be blunt and direct in their views and is not afraid to say what they have to say. This Ox can get heavily involved in their objectives and goals which makes them unaware of other people’s thoughts and feelings at times."


Anyways, you make some interesting points which I have included in the snippets of the quote below which I think it would be worth replying to for clarity and extra info (y)

Agreed. it may have been the way I wrote it, but it is only the water temp which is the key. For these tests I set the heater to MAX (I would usually just use ECO in actual use) and left enough time to cool (or ran some cold water through) to ensure the heater would need to be on for over an hour minimum to heat back to MAX - that way I could always take a slice of an hours operation for comparision purposes.
As an aside (and nothing to do with the test), the way the heater seems to like to work is once up to temp the heater element goes off and then once the 'restart temp' is reached, it kicks on again, but only for a few minutes to put back what heat was lost over the previous 5 hours or so. so in real use it is on for one hour, then on for much shorter times every few hours after that.


Now this is an interesting observation you make here. This chart I think will answer your last thought? (I wasn't actually intending to show any charts but this seems to have the info you were wondering about?)

Heater VandC
by David, on Flickr
The Blue Line is the voltage. You see it immediately rises back up when the load is removed, as you expect, but then you see it recover futher just as you would expect a battery to do once you know something about battery chemistry.
Now having an improved SOC due to the 2 minute recovery periods. I have to agree with you there and I think this is where the Battery Monitors seem to fall down a little. They are instant point-of-time devices and don't (as far as I can tell) any kind of averaging/smoothing/retrospective algorithm.
I suspect that if I had a straight 20 minutes on, rather than 20 minutes on over a 60 minute window, the SOC would have ended up exactly the same (and I *think* it should not be the case for the same thinking as you?)
Now to be fair to the makers of them, the way I am using my system is not that typical by any means and it is impossible to them to cover every possibility and variation. Plus because of the brilliant Victron BMV and Victron GX software, I do have all this data on a minute-by-minute basis available to me to analyse which is fantastic for my inner Geek :geek:


I read your post in - I am sure - just the way it was intended. And hopefully my reply will be seen in the same way also :)

Cancer, https://www.astrology-zodiac-signs.com/zodiac-signs/cancer/
No I don't believe in any of it, but its so right in everything it says.

I think I don't believe in the TV/Press side of it where say Russel Grant says 8.333333% of the population is going to find love, get a pay rise, win a holiday today, well it never happened to me, lol.

There is a lot we think we know as humans but we don't. Lay lines, Chinese Horoscopes, what came first the chicken or the egg, just three examples. I expect somebody knows all the answers.:rolleyes:

Well the graph show the two immediate stages of recovery for sure, I think over a say 2 day period you might get a bit more of a slow balanced recovery, but then you have to take account any other charge or discharge, as you mentioned in a reply to someone else, so if I was testing it I would disconnect the batteries and separate the bank, make sure all the battery tops are clean and dry, I am sure yours are. Working on many types of Trucks, including Insulated Earth Standard Trucks and Petrol Regulated Vehicles tracking of electricity by water moisture, mud on batteries or any exposed electrical item, brush carbon inside starter motors etc, all makes the small difference to muck up your readings, as would also be the case if one of the batteries was not up to scratch, difficult to tell in a block. Unless it was in an electric car where systems are set up to monitor separate parts of the block. I don't think you need to go that far as I think you will get to a point where you have proven your point about Peukert's Law not being as clear or as correct as it could be or why manufactures add this function or that function, to be honest they don't always know themselves what's right and what isn't, they just make something for a price and you hopefully get what you pay for.

It's interesting to see that, (and I think I am right in saying this), that the cheaper monitor gave out in effect the same readings as the Victron once you had set that up to 1.03. But of course without the two different monitors you couldn't test or prove that point to show yourself. Yes the BMV gives you more for your money and may well be more flexible for different systems but of course it costs a lot more. As you say very interesting data.

Your rely was as I suspected and understood as you wrote it:) You must have the same Syndrome as me, lol.
 

chas142

Full Member
Having built an electric car and fitted 6 150Ah (C20 rating) deep cycle batteries in series, I believe Peukert. I think the problem maybe that the battery chemistry comes into play. After doing a discharge cycle there are probably localised effects around the plates, especially with a gel battery, where the electrolyte is rather more viscous. Letting them rest for a while would allow these local effects to dissipate and even out. With my "wet" batteries, I take up to 200 Amps at times and normally run about 70 to 100 Amps. This sort of current draw has definitely effected capacity and reduced the calculated range from about 45/50 to just under 30 miles. I forgot about Peurkert!!! Should have gone for Lithium Ferrous Phosphate (LiFePO), the constant is almost 1, so the capacity is only slightly reduced. The batteries would have been about one third the weight, giving me even more range. Unfortunately my pocket would have been very much lighter :)- I am pleased though with the life of the batteries, I was expecting maybe two years, but they are still going strong after four and a half years.
Interesting, what make and type were your wet batteries?

I assume you removed the engine and fitted an electric motor, have a separate battery or a reducer for the 12volt side. I hadn't even heard of Peurkert till today, ok yesterday now, lol.

Well 30 miles is 30 mile, I don't think you get the rated mileage out of most electric or hybrid cars, it was a sales guide and I know that a new standard has been set to try to give a clearer picture. What mileage have you done in the 4.5 years?
 

Bigbarry

Full Member
You must really have a sad life to post this on New Year's day. I agree with Simon, but we are also sad for reading it. My excuse is that I'm waiting for my venison. Moira's out with the gun!
All the best for 2019, and respect for knowing what Airfix used to do.
See you at Moffat.
Gordon
Gordon, I'm in sleepless mode at the moment, but reading this I feel like I could retune to my mattress and actually get some zz's
 

trevskoda

Full Member
I just have two little volt meters on dash,one for engine and the other for service battery,as i mainly only use lights and loo flush and charging the phone i have never seen batterys go down below resting voltage of 12.6 /12.7.van f.jpg
 

wildebus

Full Member
....so if I was testing it I would disconnect the batteries and separate the bank, make sure all the battery tops are clean and dry, I am sure yours are. Working on many types of Trucks, including Insulated Earth Standard Trucks and Petrol Regulated Vehicles tracking of electricity by water moisture, mud on batteries or any exposed electrical item, brush carbon inside starter motors etc, all makes the small difference to muck up your readings, as would also be the case if one of the batteries was not up to scratch, difficult to tell in a block.
In fact, after the batteries had been installef for a year, I did disconnect them from the system, then each other, left them to settle and took voltmeter readings to see how close they were. Not identical, but I think the widest gap was 0.07V at an average of 13.09V, so I decided that was very acceptable for a mass-produced comsumer product :)
I have sketched out ways to monitor each battery but decided against as the monitoring tools themselves are as likely to have as much variation between themselves as the batteries are, so no point really :D

Unless it was in an electric car where systems are set up to monitor separate parts of the block. I don't think you need to go that far as I think you will get to a point where you have proven your point about Peukert's Law not being as clear or as correct as it could be or why manufactures add this function or that function, to be honest they don't always know themselves what's right and what isn't, they just make something for a price and you hopefully get what you pay for.

It's interesting to see that, (and I think I am right in saying this), that the cheaper monitor gave out in effect the same readings as the Victron once you had set that up to 1.03. But of course without the two different monitors you couldn't test or prove that point to show yourself. Yes the BMV gives you more for your money and may well be more flexible for different systems but of course it costs a lot more. As you say very interesting data.

Your reply was as I suspected and understood as you wrote it:) You must have the same Syndrome as me, lol.
it was set at 1.0 in fact (so no effect) when the two meters matched.
what this does mean though is that the cheaper meter will have a tendency to be optimistic in its SOC reading probably - and the more the Peukert factor comes into play (or should), the more optimisitic the SOC will be on the cheaper meter.

Drive something hard, it will last less time - like the electric car thing. But it doesn't mean necessarily the total energy is less, just harder to extract.
I don't know about anyone else, but when I reuse AA batteries (really Cells to be pendantic as we are trying to be exact on things). I use them in say a Radio. When that radio stops working, I don't throw the batteries away because they are dead - because they are not of course! I put them into an electric wall clock which uses a lot less power and so can extract the remaining energy in that battery. Then when the clock stops working, then the battery is pretty well dead (unless you had something even lower current draw?)




I just have two little volt meters on dash,one for engine and the other for service battery,as i mainly only use lights and loo flush and charging the phone i have never seen batterys go down below resting voltage of 12.6 /12.7.View attachment 41187
That method works well :)
This was my T4 Camper (only had a single Leisure, twin solar and compressor coolbox to drive)
by [url=https://www.flickr.com/photos/moominsonsafari/]David, on Flickr[/url]
 
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