New batteries

[Sybaris]

Willow3,
Yes I am getting more impressed by the minute, and reading a lot more on the canal boat forum which seems to have quite a few very knowledgeable members I think I am starting to understand how the SoC (state of charge) is calculated in the smartgauge and it all makes good sense. In brief it is based on testing the voltage and loads with time delays. He also says that it is more precise during discharge than during charge, but the gauge is always connected and keeps correcting itself so that doesn't matter in the long run.

Interestingly one thread called "Buying a Multimeter, What sort should I get?" (which I started to read because I want to get a good multimeter) lead to discussions in which Gibbo reveals some of the logic. I think this link might get you there
http://www.canalworld.net/forums/index.php?showtopic=7218&hl=smartgauge&st=120

Incidentally Gibbo has also claims to have worked on the design of several Ah gauges and I am convinced he knows his stuff. Reading all the information it is now totally clear to me how an Ah gauge can never be very reliable, especially if you often discharge your batteries down to 50%. The only way to be safe then is to synchronize the gauge every time you know for sure you have made a completely full recharge.

This also gives you an idea of how to calculate your SoC which you can do yourself with a watch and a multimeter. http://www.attfield.dircon.co.uk/info-indx.html#Testing

Interesting stuff, and I know what I am buying next.

Cheers,
Per

 

[Plevier]

Willow
We're following each other around. I was on the panbo site last night as well as the canalworld forum. I came across this link on panbo about methods of measuring battery capacity. You might find it interesting.
http://www.buchmann.ca/article25-page1.asp

Yes that's what i was referring to re AC impedance.
I find it unconvincing. It's one man's pet theory and instrument AFAICS. That doesn't mean it's wrong, I know. You could say the same about the SmartGauge.

 

[Plevier]

Willow3,
Yes I am getting more impressed by the minute, and reading a lot more on the canal boat forum which seems to have quite a few very knowledgeable members I think I am starting to understand how the SoC (state of charge) is calculated in the smartgauge and it all makes good sense. In brief it is based on testing the voltage and loads with time delays. He also says that it is more precise during discharge than during charge, but the gauge is always connected and keeps correcting itself so that doesn't matter in the long run.

Interestingly one thread called "Buying a Multimeter, What sort should I get?" (which I started to read because I want to get a good multimeter) lead to discussions in which Gibbo reveals some of the logic. I think this link might get you there
http://www.canalworld.net/forums/index.php?showtopic=7218&hl=smartgauge&st=120

Incidentally Gibbo has also claims to have worked on the design of several Ah gauges and I am convinced he knows his stuff. Reading all the information it is now totally clear to me how an Ah gauge can never be very reliable, especially if you often discharge your batteries down to 50%. The only way to be safe then is to synchronize the gauge every time you know for sure you have made a completely full recharge.

This also gives you an idea of how to calculate your SoC which you can do yourself with a watch and a multimeter. http://www.attfield.dircon.co.uk/info-indx.html#Testing

Interesting stuff, and I know what I am buying next.

Cheers,
Per

Oh well found!
Not digested yet but seems to be on the lines I was thinking but simplified by making assumptions about shape of discharge curve.
Noticed in passing that his Peukert page was written by someone else, who is over my head in pure maths but who I really think has misunderstood the topic.
"Gibbo" seems to be a practical man rather than theoretician - nothing wrong with that!

 

[Sybaris]

Willow3,

I have to add some more info I have found.

This is what Gibbo wrote in the Multimeter thread:

The way I do it in the monitor is to take 3 voltage readings at short intervals, check to see if there's enough difference between them to get meaningful results (if there isn't, do it again at longer intervals) then "curve fit" to the three points and predict the voltage after 12 hours. This is merely one of the many strategies used. This task is trivial for a computer but not so for a brain.

It keeps a log of the minimum time required between readings and uses that as the starting point next time. This remains roughly constant as the battery ages. Having also "sucked" the info out of units in installations it's pretty constant for all batteries of any one type. You need to wait about 30 mins after removal of the load or charger (not saying how I detect that) then about 15 mins between each reading to get meaningful results. Obviously the longer you wait between readings, the more accurate the final result will be. But you never know when something might get switched on so it keeps going and keeps a record of the previous readings, finally settling on using the longest time interval it got before something loused it up.


I also read the manual for the NASA BM-1 gauge and found this:

When the battery is being charged, the voltage is no longer a reliable
estimate of the state of charge, and so the BM-1 integrates the Ampere
hours added to the last known capacity to estimate the battery's state of
charge on a continuous basis.

This implies that they measure the SoC based on voltage reading at discharge and Ah at charge. Perhaps the best of both worlds. I have written to NASA to ask them to confirm that to be the case.

I have read comments from many happy Smartgauge users and I think that when used with an existing battery meter (such as Xantrex) to see the Ams in and out you have a perfect combination.

Cheers,
Per

 

[Roger_D]

I have the alternator charging the main bank (wet cells) directly, which in turn charges the start battery (olympus) through a Xantrex slave charger. I retained the 1,2 off switch (well, bought a new Bluesea one) which is not needed to operate the engine, (I have a isloator switch at the start battery), but it connects the main bank in emergency to the engine/starter as well as the starter battery to the boat if needed . If someone turns it off while running no damage should occur.

I bought the Smarguage at the beginning of the season at it seems to work very well. It can be set to turn on its dislplay when the charge voltage exceeds a certain amount, (say 13 volts) so it is comforting to see that the charging circuit is working and what its charging voltage is.

 

[Plevier]

Sybaris
The NASA and the SmartGauge have nothing in common. The NASA is a conventional monitor with a shunt. The SmartGauge cannot measure Ah because it has no current measurement input.
At the moment I can't follow how the SmartGauge monitors on charge.

 

[Sybaris]

Willow3,

Oh no I shouldn't have written anything about the NASA unit to potentially start a new thread spin. I know they are not the same thing but I thought it would be interesting to mention that it seems in their manual as if they calculate the SoC during discharge using the voltage, i.e. similar to the Smartgauge. I have written for confirmation.

I already have the Xantrex link to measure amp in and out so I don't need the NASA, but I will now purchase the Smartgauge in order to also get a correct SoC seading instead of relying on the Ah counter in the Xantrex.

Cheers,
Per

 

[Plevier]

Willow3,

Oh no I shouldn't have written anything about the NASA unit to potentially start a new thread spin. I know they are not the same thing but I thought it would be interesting to mention that it seems in their manual as if they calculate the SoC during discharge using the voltage, i.e. similar to the Smartgauge.

Are you sure it calculates SOC from voltage? I'm really surprised, I thought it counted Ah.

I haven't been able to find their manual on a site that will download - have you a link?