Battery SG readings.

[dmr]

3 hours ago, nicknorman said:

In that case you are jolly clever!

 

I think it was only some adds, tekaways, timeziz and guzintas, it did not need integration and proper clever stuff.

.....................Dave

[nicknorman]

2 minutes ago, Dr Bob said:

So the temperature that the sg is measured at ,is the temperature of the measurement device which will be dependent on where it has been stored, or where the measurements are taken. Perhaps, yesterday evenings results were obtained in low temps - at midnight, hence higher sg's whereas todays may have been taken this lovely sunny day when it might have been considerably warmer and thus lower sg's. The user really need to try and keep the refractometer around the same sort of temperature if comparing sets of data taken at different times.

Not according to the quote from the instructions I posted. Obviously the RI of the electrolyte will vary with temperature, but if the device itself has an equal and opposite temperature effect these will cancel out. I seem to recall seeing somewhere a temperature range quoted within which the temperature compensation was adequate, it was a fairly wide range but I can't remember what.

[canals are us?]

8 minutes ago, Dr Bob said:

So the temperature that the sg is measured at ,is the temperature of the measurement device which will be dependent on where it has been stored, or where the measurements are taken. Perhaps, yesterday evenings results were obtained in low temps - at midnight, hence higher sg's whereas todays may have been taken this lovely sunny day when it might have been considerably warmer and thus lower sg's. The user really need to try and keep the refractometer around the same sort of temperature if comparing sets of data taken at different times.

You are most likely right. Yesterday evening I had the internal doors open and the fire going. Refractometer in box on kitchen worktop. Today no heating on and internal doors open and refractometer stored in an unheated engine bay. Ooops! Should I continue?

James

Edited March 7, 2018 by canals are us?

[Phil.]

16 minutes ago, canals are us? said:

You are most likely right. Yesterday evening I had the internal doors open and the fire going. Refractometer in box on kitchen worktop. Today no heating on and internal doors open and refractometer stored in an unheated engine bay. Ooops! Should I continue?

James

I would keep going if you are only equalising at 15.5 volts. As previously said this will take a while, you can up voltage to 16.2 which what Trojan say is the correct voltage. Keep going until the values stop rising.

[canals are us?]

I have just re- checked the calibration with a few drops of water and the white shading wasn't on 0 it was below. I adjusted the screw and brought the shading difference/line to 0.

I don't know if I should of re-calibrated as the readings are now much higher!

Battery 1

1 = 1.290

2 = 1.280

3 = 1.300

4 = 1.285

5 = 1.280

6 = 1.300

James

[Dr Bob]

2 minutes ago, canals are us? said:

I have just re- checked the calibration with a few drops of water and the white shading wasn't on 0 it was below. I adjusted the screw and brought the shading difference/line to 0.

I don't know if I should of re-calibrated as the readings are now much higher!

Battery 1

1 = 1.290

2 = 1.280

3 = 1.300

4 = 1.285

5 = 1.280

6 = 1.300

James

I did say in an earlier post you could have an offset! 

 

33 minutes ago, canals are us? said:

You are most likely right. Yesterday evening I had the internal doors open and the fire going. Refractometer in box on kitchen worktop. Today no heating on and internal doors open and refractometer stored in an unheated engine bay. Ooops! Should I continue?

James

That's the wrong way round. The SG is higher at lower temps. I thought you said the readings were higher today (before the recalibration).

It may be difficult to know if you have sufficient calibration to know where 100% is, but if you repeat another equalisation, you know cells 1 and 6 must be pretty near full capacity, and you should be looking at differences between the cells. These batteries dont sound like they are that bad.

[canals are us?]

7 minutes ago, Dr Bob said:

I did say in an earlier post you could have an offset! 

 

That's the wrong way round. The SG is higher at lower temps. I thought you said the readings were higher today (before the recalibration).

It may be difficult to know if you have sufficient calibration to know where 100% is, but if you repeat another equalisation, you know cells 1 and 6 must be pretty near full capacity, and you should be looking at differences between the cells. These batteries dont sound like they are that bad.

The readings are lower today using the same refractometer as used on the other results and not re calibrated. The latest results on post 80 are when I have just re-calibrated it. It doesn't make sense? Your thoughts?

James

Edited March 7, 2018 by canals are us?

[Phil.]

13 minutes ago, canals are us? said:

I have just re- checked the calibration with a few drops of water and the white shading wasn't on 0 it was below. I adjusted the screw and brought the shading difference/line to 0.

I don't know if I should of re-calibrated as the readings are now much higher!

Battery 1

1 = 1.290

2 = 1.280

3 = 1.300

4 = 1.285

5 = 1.280

6 = 1.300

James

Those readings if correct are pretty good.

[canals are us?]

7 minutes ago, Phil. said:

Those readings if correct are pretty good.

My thoughts too.

I'm giving it one final EC and calling it a day. I'll buy just two more batteries.

James

Edited March 7, 2018 by canals are us?

[Dr Bob]

3 minutes ago, canals are us? said:

The readings are lower today using the same refractometer as used on the other results and not re calibrated. The latest results on post 80 are when I have just re-calibrated it. It doesn't make sense? Your thoughts?

James

The pre calibrated results today are lower than yesterday. That would fit if you measured them at a higher temp today but you didnt - and Nick is saying the device will compensate for the temperature anyway - so lets forget temperature. Why were they lower?....as said above, if the batteries were discharged a bit then that would show up as a lower sg. You need to make sure they are fully charged if you are using sg to determine degree of sulphation.

You have now re-calibrated and are getting sg's that when taken in isolation could be too high....but I dont know what the design sg is of your type of battery. You may have not calibrated it properly so now it is reading high. You may not be reading the device right....but that is not a problem as the repeatability looks good....so keep doing what you are doing. I dont think you will be able to calibrate it properly unless you get some acid of known sg so forget the 'accurate' calibration. You dont need that accuracy. Just do another equalisation and look to see if the 'low' cells come up to meet the high values. Once you are done, double check with a volatage at rest first thing in the morning vs Ahrs used. Dont chuck them out!

[nicknorman]

The original sg is 1.277. The sg should therefore not be higher than that unless the electrolyte level is low. I suggest you have another go with the calibration / water drop to make sure you haven't over-corrected it. Ideally the calibration should be done with the device having reached an even temperature of around 20C

[nicknorman]

1 minute ago, Dr Bob said:

The pre calibrated results today are lower than yesterday. That would fit if you measured them at a higher temp today but you didnt - and Nick is saying the device will compensate for the temperature anyway - so lets forget temperature. Why were they lower?....as said above, if the batteries were discharged a bit then that would show up as a lower sg. You need to make sure they are fully charged if you are using sg to determine degree of sulphation.

You have now re-calibrated and are getting sg's that when taken in isolation could be too high....but I dont know what the design sg is of your type of battery. You may have not calibrated it properly so now it is reading high. You may not be reading the device right....but that is not a problem as the repeatability looks good....so keep doing what you are doing. I dont think you will be able to calibrate it properly unless you get some acid of known sg so forget the 'accurate' calibration. You dont need that accuracy. Just do another equalisation and look to see if the 'low' cells come up to meet the high values. Once you are done, double check with a volatage at rest first thing in the morning vs Ahrs used. Dont chuck them out!

Obviously the most accurate calibration should be done with acid of a precisely known strength that is close to the strength of the electrolyte to be measured. But in reality, it depends on what accuracy is actually needed. For example, some folk use refractometers to measure water salinity for aquaria. With the range of sg from pure water to water of the desired salinity being only about 1/10th of the range of sg from pure water to that of a fully charged battery's electrolyte, in the former case precision has to be x10 to get the same effective accuracy. So in the case of battery acid with its relatively high sg, calibration at 1.000 sg gives adequate accuracy.

[canals are us?]

20 minutes ago, nicknorman said:

The original sg is 1.277. The sg should therefore not be higher than that unless the electrolyte level is low. I suggest you have another go with the calibration / water drop to make sure you haven't over-corrected it. Ideally the calibration should be done with the device having reached an even temperature of around 20C

Electrolyte level is normal/full. Not used any. The room where I re-calibrated it is chilly as no heating on. I have just lit the stove! I'll recalibrate it in the heated room.

EDIT. Tempted to just buy 4 new for £551.36 delivered and save the hassle as cant have a shower as stuff out of rear stored in bath. Would my existing 2 batteries have a value or not?

James 

Edited March 7, 2018 by canals are us?

[smileypete]

Another way to get an idea of SoC is resting voltage:

http://jgdarden.com/batteryfaq/carfaq4.htm#ocv_soc

Like I say, don't worry (just don't neglect them either).

 

Edited March 7, 2018 by smileypete

[WotEver]

4 hours ago, canals are us? said:

A diagram would be great when you have got time!

How’s this?

[nicknorman]

 

(You’ll have to ignore that very naughty extra red wire on the left!)

[canals are us?]

Thanks for the diagram and photo whotever and nicknorman and smileypete for the link.

If you were me would you keep these 2 batteries and buy 2 more or buy 4 new?

I really can't spend any more time on them as need to put everything back, shower and dinner.

James

[WotEver]

8 minutes ago, nicknorman said:

(You’ll have to ignore that very naughty extra red wire on the left!)

Shhh, nobody would have noticed...

1 minute ago, canals are us? said:

Thanks for the diagram and photo whotever and nicknorman and smileypete for the link.

If you were me would you keep these 2 batteries and buy 2 more or buy 4 new?

I really can't spend any more time on them as need to put everything back, shower and dinner.

James

Buy two more and get on with your life

Just charge ‘em correctly and perform the occasional equalising charge as per Trojan’s advice. 

[nicknorman]

14 minutes ago, canals are us? said:

Thanks for the diagram and photo whotever and nicknorman and smileypete for the link.

If you were me would you keep these 2 batteries and buy 2 more or buy 4 new?

I really can't spend any more time on them as need to put everything back, shower and dinner.

James

Yes I would just buy 2 more. The original 2 have slightly reduced capacity but if you are used to having just 2, having the equivalent of about 3.8 will still seem a big improvement.

[canals are us?]

Thanks both, I'll buy just 2.

This forum and advice has been great. I have learnt a lot from all your advice over the last 2 months regarding my electrical set up and have now learnt about keeping a good charging regime and to do an EC as needed.

James

[MtB]

2 hours ago, nicknorman said:

Obviously the most accurate calibration should be done with acid of a precisely known strength that is close to the strength of the electrolyte to be measured.

 

This raises another point I have discussed with DMR over a bottle or three of Thatchers and concluded we don't know. Perhaps someone here does.

When new batteries are filled, what are they filled with, exactly? Yes sulphuric acid, and according to a brief google at a concentration of between 30% and 50%. So does the bloke filling the battery have a carboy of 100% H2SO4 and dilute it himself? Or will the carboy of acid be factory prepared for him to dispense? If the former there is a lot of scope for sloppy filling. Stretching the acid to go into more batteries as it is probably very expensive. 

When I bought my Yuasas the retailer was apparently filling batteries as there were large carboys of 'something' up on the benches. I should have asked what they were.

I'm wondering if my Yuasa will never come up to normal SG if the electrolyte was over-diluted when they were filled. 

[WotEver]

Dunno if they ever get the concentration wrong either deliberately or accidentally but here’s a high-end battery manufacturer’s instructions for how to do it. 

http://support.rollsbattery.com/support/solutions/articles/427-activating-instructions-dry-charged-batteries-detailed-

[dmr]

2 hours ago, canals are us? said:

Electrolyte level is normal/full. Not used any. The room where I re-calibrated it is chilly as no heating on. I have just lit the stove! I'll recalibrate it in the heated room.

EDIT. Tempted to just buy 4 new for £551.36 delivered and save the hassle as cant have a shower as stuff out of rear stored in bath. Would my existing 2 batteries have a value or not?

James 

Scrap yard prices are very variable from yard to yard and day to day, but you might get £30 for your old Trojans, but you need to factor in how far you need to drive and how many hours it will take. Maybe if you see a "subsistence boater" on a little plastic cruiser you could donate them and they can get the scrap value, they have spare time but not much money.

..................Dave

[dmr]

1 hour ago, Mike the Boilerman said:

 

This raises another point I have discussed with DMR over a bottle or three of Thatchers and concluded we don't know. Perhaps someone here does.

When new batteries are filled, what are they filled with, exactly? Yes sulphuric acid, and according to a brief google at a concentration of between 30% and 50%. So does the bloke filling the battery have a carboy of 100% H2SO4 and dilute it himself? Or will the carboy of acid be factory prepared for him to dispense? If the former there is a lot of scope for sloppy filling. Stretching the acid to go into more batteries as it is probably very expensive. 

When I bought my Yuasas the retailer was apparently filling batteries as there were large carboys of 'something' up on the benches. I should have asked what they were.

I'm wondering if my Yuasa will never come up to normal SG if the electrolyte was over-diluted when they were filled. 

A while ago I tried to make up a "calibration fluid" using Citric Acid and some accurate scales but it was not too good, I could only get onto the very lowest part of the hydrometer scale so could not diagnose "scale" errors.

I reckon with a "Turkey baster" I am limited by the float sticking to the sides and meniscus errors. I have played with two "rotating dial" devices (mine and mtb's) and these differed by 10points, plus a random element due to stiction in the temperature compensation dial (mtb proposed air bubbles as the source). The optical gauge is possibly the best but you need to go in with a turkey baster first to stir up the acid. At work my speciality was designing instruments and software to make difficult measurements, anyone who can really measure SG to better than +/- 50 points is a better man than me (but then I drink too much Thatchers) .

..............Dave

1

[MtB]

21 minutes ago, dmr said:

The optical gauge is possibly the best but you need to go in with a turkey baster first to stir up the acid.

 

I hold that the SG varies with height in the battery. The feeble bubbles created even during desulphation are too tiny and lacking in energy to effectively disrupt the stratification in the acid IMO. I reckon even serious turkey baster squirting only penetrates an inch or two below the top of the plates. 

A device to properly mix up the electrolyte needs inventing.