Smartgage and Equalisation

[dmr]

This is one for Gibbo...

Whenever I equalise charge my batteries (Trojans) I note that they discharge quicker than expected the next day.

Is this some strange mechanism within the batteries?

or

Does the Smartgage detect the equalisation and do some sort of internal reset and then have to "relearn" the battery capacity?

I am a sad engineer and get curious about these things....

 

.......Dave

[pearley]

See you didn't get a reply to this. I think it is just the way Smartguage relearns. I find that the day after coming off a shoreline the batteries appear to discharge quicker.

 

Regards

Pete

[by'eck]

Since the equalisation cycle will have left your battery voltage artificially high, their voltage will initially drop quite quickly before resuming a more normal voltage reduction rate with discharge.

 

I'm not familiar with the Smartguage but do know its primary reference is battery voltage.

[dmr]

Thanks for the replies!

 

I have thought about this a bit more, and I reckon Smartgage is detecting the equalisation process and doing a reset.

This is reasonable behaviour as Smartgage (or rather its creator) knows that equalisation has most likely changed the effective capacity of the batteries.

However I am still a bit surprised that Smartguge assumes a reduced capacity; taking its current estimate of the capacity and increasing it by maybe 10% would have been "smarter".

I guess Smartguage is going back to a "default" battery model which has a capacity of rather less than my 450Ah...but this is probably reasonable as maybe a lot of Smartgages are fitted to vehicles where bank sizes are smaller.

 

Its been said before. but where is Gibbo?????

 

........Dave

[nb Innisfree]

Smartgauge has no idea of battery capacity, as it keeps comparing discharge characteristics against various battery type logarithms it gradually keeps making more accurate guesses of SoC as it narrows down the choices. It's a bit thick and slow really as it can only make one comparison at a time but it never gives up as it relentlessly keeps cornering the nearest it can get to the truth.

 

That's how I picture it anyway, I await my fate.

Edited December 23, 2012 by nb Innisfree

[dmr]

I have always assumed that Smartgage does know the bank capacity. It obviously learns as it goes along and capacity would be the main thing it could learn. I also wonder if it learns about typical user habits!!!

I just don't see how it can work off voltage alone as load will massively change the voltage....so it must make an educated guess most of the time.

I suspect it uses rate of change of voltage quite extensively.

It also makes a reasonable shot at state of charge during charging...surely it must have an idea of bank capacity to do this???

I held off getting a Smartgage for several years as I could not convince myself that a voltage only device would be sufficiently accurate.

I now think it works amazingly well which is why I was curious about the equalisation anomaly!

 

..........Dave

[Paul C]

It doesn't use voltage. I raised a similar question about it, and on pressing, got the right answer but Gibbo was a bit too shy to actually post it.

[nb Innisfree]

The new up and coming Smartgauge has a shunt I think and by comparing ah counting with the standard Smartgauge is able to make a decent fist of battery ah capacity.

 

C'mon Gibbo put me out of my misery, right or wrong.

[dmr]

It doesn't use voltage. I raised a similar question about it, and on pressing, got the right answer but Gibbo was a bit too shy to actually post it.

 

Smartgage certainly does measure voltage. The clever thing about it is that it Only measures voltage and nothing else, where many engineers would feel that a measure of current would also be required.

I suspect Gibbo was saying that it is not a "simple voltmeter" but instead uses information from the voltage that it measures to magically deduce the state of charge.

 

........Dave

[nb Innisfree]

I reckon it uses loads of various logarithms created from hours and hours and hours of tracking different sorts of batteries to determine their performance characteristics to enable a match to be made between batteries being monitored and and one of those many logarithms. No magic involved just loads of high speed comparisons, oh and lots of relentless accurate and consistent measuring by our resident guru.

 

My layman's diagnosis that's all.

[smileypete]

There's a hint of how it works in this thread:

 

http://www.ybw.com/forums/showpost.php?p=716133&postcount=42

 

Edit: Also worth a read:

 

https://docs.google.com/viewer?a=v&q=cache:MN3jI7_OlYYJ:www.cadex.com/industry_rapid/DeepCycle-LA-Batt-LowRez-Golf1.doc+&hl=en&gl=uk&pid=bl&srcid=ADGEESibi7dHoqS1a0A9vYsh-zyM7suM0R0Dhczf2diHs1EG8TYxsdhktYUx1ccwHkSY7_ZeAFxQQG9-8tgmyRig35I1GWhuTKkfKcmUOzx5SSFK8_HHXzw-p9S9NbwYi_J28CVC5Oc1&sig=AHIEtbRsxxYN-9TtGU3QfX7bx2Zxa7gKGA

 

cheers, Pete.

~smpt~

Edited December 24, 2012 by smileypete

[bottle]

 

I think Gibbo may be on the 'norty step' after a recent post, so it may be some time before he returns

 

or

 

he is on holiday.

[Richard10002]

There seems to be some talk here that sounds like smoke and mirrors. Smartguage measures only voltage. It can the calculate change in voltage, and rate of change of voltage.... I think that is all. It then uses a bundle of equations to attempt to calculate State of Charge - which it seems to do quite well, if reports here are anything to go by.

 

When new, or after something changes, it seems to take a few cycles to calculate how things are going. Perhaps charging at 15.5V for 4 hours or so is one of these occasions, although you would have thought its equations would allow for any reasonably possible combination of charging and discharging voltages, I.e. between about 11.5V and 15.5V?

[nicknorman]

I have a SG and an amp-hr counter. The bats are on float charge when in the marina, and we tend to cruise for longish days, so usually the bats are fully charged when we start to drain them. I have noticed that SG tends to be a little pessimistic for the 1st 25% or so, but by the time 50% SoC is approaching, SG and AH counter are once more agreeing fairly closely (and bear in mind set and actual capacity are probably by now drifting apart a bit - bats 1 season old). So SG is remarkably accurate at say 50% SoC but not so good at say 80% SoC. Still very good though for a 2 wire device.

 

I suspect that in OPs case the algorithms are put off by a higher voltage since SG has to be able to cope with different battery technologies within the groups available, and doesn't know the battery temperature. But I am sure it will come good by 50%.

 

I remain unconvinced that it works by injecting any signals into the Bats to measure impedance etc, since the impedance of its wiring , fuse etc is likely to be more significant than a big battery bank. Has anyone taken the cover off to see what components are on the PCB? It could probably be determined whether only the voltage is being measured, or whether there is any driver electronics capable of sending a signal down the wires (which I doubt). And that would be visible on a 'scope. Gibbo does coyly deny that it "only measure voltage" but I remain dubious that it does not just measure voltage and its derivatives.

[ditchcrawler]

I have a SG and an amp-hr counter. The bats are on float charge when in the marina, and we tend to cruise for longish days, so usually the bats are fully charged when we start to drain them. I have noticed that SG tends to be a little pessimistic for the 1st 25% or so, but by the time 50% SoC is approaching, SG and AH counter are once more agreeing fairly closely (and bear in mind set and actual capacity are probably by now drifting apart a bit - bats 1 season old). So SG is remarkably accurate at say 50% SoC but not so good at say 80% SoC. Still very good though for a 2 wire device.

 

I suspect that in OPs case the algorithms are put off by a higher voltage since SG has to be able to cope with different battery technologies within the groups available, and doesn't know the battery temperature. But I am sure it will come good by 50%.

 

But how do you know which one is right, it could be the SG is spot on and the counter out, but who knows. The batteries may already be down to 75% capacity and they are both wrong.

Old Chinese proverb.

Man with watch knows time. Man with two watches never knows time.

[DaveC]

 

Old Chinese proverb.

Man with watch knows time. Man with two watches never knows time.

 

 

And a watch that doesn't go is right twice a day!

 

 

 

Dave

[nicknorman]

But how do you know which one is right, it could be the SG is spot on and the counter out, but who knows. The batteries may already be down to 75% capacity and they are both wrong.

Old Chinese proverb.

Man with watch knows time. Man with two watches never knows time.

Any error in the AH counter will be a scaling error - ie a fixed % error. So the fact that the SG and AH don't track each other quite proportionately means that element is an SG error. That they come closer around 50% indicates that the AH is not too far out, as does observing the no-load rested voltage. So you are right in that neither is correct, but they have different types of errors and my point is that in my installation, the SG appears a little pessimistic at first but settles down by the time 50% is approached.

[Chris Pink]

Gibbo does coyly deny that it "only measure voltage" but I remain dubious that it does not just measure voltage and its derivatives.

 

This is my impression too, as it can also measure time, that it measures rate of change of voltage and compares this with various battery types in its EEPROM. The interesting thing is that it has absolutely no idea of capacity.

 

His answer on ybw forum ( better social skills than his current style I notice - something to trying to sell the things?) about other things that could be measured with two wires was more about contradicting the 'two wires = voltmeter " argument.

Edited December 24, 2012 by Chris Pink

[smileypete]

I have a SG and an amp-hr counter. The bats are on float charge when in the marina, and we tend to cruise for longish days, so usually the bats are fully charged when we start to drain them. I have noticed that SG tends to be a little pessimistic for the 1st 25% or so, but by the time 50% SoC is approaching, SG and AH counter are once more agreeing fairly closely (and bear in mind set and actual capacity are probably by now drifting apart a bit - bats 1 season old). So SG is remarkably accurate at say 50% SoC but not so good at say 80% SoC. Still very good though for a 2 wire device.

Are you inferring that an amp hour counter is more accurate than SmartGauge? Burn the heretic!!!

 

I suspect that in OPs case the algorithms are put off by a higher voltage since SG has to be able to cope with different battery technologies within the groups available, and doesn't know the battery temperature. But I am sure it will come good by 50%.

 

I remain unconvinced that it works by injecting any signals into the Bats to measure impedance etc, since the impedance of its wiring , fuse etc is likely to be more significant than a big battery bank. Has anyone taken the cover off to see what components are on the PCB? It could probably be determined whether only the voltage is being measured, or whether there is any driver electronics capable of sending a signal down the wires (which I doubt). And that would be visible on a 'scope. Gibbo does coyly deny that it "only measure voltage" but I remain dubious that it does not just measure voltage and its derivatives.

Well the article linked to refers to commercial meters that measure both SoC and state of health, then explains how they do it.

 

SmartGauge clearly does compensate for declining state of health, it's a pity it can't display a raw figure for state of health and then allow it to be stored and used for a baseline for future relative measurement as a percentage. Would make it much easier to tell whether the batts were being persistently undercharged or not.

 

cheers, Pete.

~ smpt~

Edited December 24, 2012 by smileypete

[nicknorman]

Are you inferring that an amp hour counter is more accurate than SmartGauge? Burn the heretic!!!

 

 

Yes, an AH counter is more accurate than SG IF it is correctly set up with the current actual capacity, CEF, Peukets etc and is kept in sync. However a SG is much easier to install and requires no "maintenance" of settings.

 

On the subject of how it works, it would be interesting to take it home and connect it up to an adjustable bench power supply, then see if SoC is reasonable as the regulated voltage is slowly reduced. That would prove or disprove any ideas about impedance measurement etc

 

 

SmartGauge clearly does compensate for declining state of health, it's a pity it can't display a raw figure for state of health and then allow it to be stored and used for a baseline for future relative measurement as a percentage. Would make it much easier to tell whether the batts were being persistently undercharged or not.

 

 

Therein is the advantage of having both an AH counter and a SG. Anyway, son of SG seems likely to be able to do as you suggest, if it ever materialises!

[Taslim]

I reckon it uses loads of various logarithms created from hours and hours and hours of tracking different sorts of batteries to determine their performance characteristics to enable a match to be made between batteries being monitored and and one of those many logarithms. No magic involved just loads of high speed comparisons, oh and lots of relentless accurate and consistent measuring by our resident guru.

 

My layman's diagnosis that's all.

 

Feel free to slap me if i'm wrong but do you and some other posters mean Algorithms?

 

taslim.

[nb Innisfree]

Smartgauge is either 100% genuine and a testament to Gibbo's genius or his first class conman skills are a testament to his genius.

 

Either way you have to take your hat off to him.

 

Feel free to slap me if i'm wrong but do you and some other posters mean Algorithms?

 

taslim.

 

Yes I do, don't know why I typed that, age probably.

[Grace and Favour]

Smartgauge is either 100% genuine and a testament to Gibbo's genius or his first class conman skills are a testament to his genius.

 

Either way you have to take your hat off to him.

 

 

 

Yes I do, don't know why I typed that, age probably.

 

agelogorithms? (are they extended algorithms?)