Battery SG readings.

[WotEver]

24 minutes ago, Neil Smith said:

I watched a YouTube video on desulphating batteries and it can take up to 3 weeks to fully recover, Google it and make your own mind up, they are not selling anything.

Neil

It depends on the amount of sulphation of course. Battery University states “24 hours” on one of its pages. Longer might be necessary. Shorter might suffice. A higher voltage will take less time than a lower voltage. There is no ‘one size fits all’. 

[Neil Smith]

34 minutes ago, WotEver said:

It depends on the amount of sulphation of course. Battery University states “24 hours” on one of its pages. Longer might be necessary. Shorter might suffice. A higher voltage will take less time than a lower voltage. There is no ‘one size fits all’. 

Exactly, he checked a few times a day until the st stopped rising then put it on normal charge until 100%.

Neil

[MtB]

55 minutes ago, Neil Smith said:

Exactly, he checked a few times a day until the st stopped rising then put it on normal charge until 100%.

 

Hmmm so a proper desulphate can take days on end eh?

Maybe I'll bring my set to the house and bung them on the bench. Will have to buy a second set of batts to use in the meantime. Hmmmm... now, what shall I buy?

[dmr]

7 hours ago, canals are us? said:

Well after 5 SG tests blue above is the latest readings at just gone 3am over 4 hours. What are your thoughts? Cell 5 not moving upwards in the last 3 tests. Thinking carry on and keep seeing if they continue to rise?

Can you mix new batteries with these sulphated batteries above or would it cause issues with new? Off to bed now!!

James

You could try increasing the voltage to 16 or so if you are able to (I assume you are at 15.5?). Also go on for another few hours. The figures are almost reasonable for older batteries but I would prefer to see them all above 1.26. You can mix old and new but you will then need to keep a close eye on the older ones for signs of impending failure which otherwise might be masked by the good ones.

But, its often quite a bit cheaper to buy a set of four rather than just two, and you have now learned all about SG and equalisation, 3.5 years in not a bad life, so maybe just get 4 new ones.

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

[WotEver]

15 minutes ago, Mike the Boilerman said:

Hmmm so a proper desulphate can take days on end eh?

Just keep going until the sg stops increasing. The rest of the sulphate is there to stay. 

[dmr]

Just to throw a little spanner in the works, how much water have you got in these batteries?

I did a quick calculation awhile ago and estimated that the difference between "just over the plates" and "right up to the mark" gives a SG variation of about 10 (a battery at 1.250 might read 1.26 on low water) so this could give false optimism on a very long equalisation if a lot of water was lost..

Does anybody want to check my calculation?

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

[Neil Smith]

1 hour ago, WotEver said:

Just keep going until the sg stops increasing. The rest of the sulphate is there to stay. 

That's what the chap on youtube said but on some it can take weeks as bits fall off allowing it to take a bit more charge, he done it with an old unreglugated charger with a resistor in line to lower the amperage.

Neil

[nicknorman]

1 hour ago, dmr said:

Just to throw a little spanner in the works, how much water have you got in these batteries?

I did a quick calculation awhile ago and estimated that the difference between "just over the plates" and "right up to the mark" gives a SG variation of about 10 (a battery at 1.250 might read 1.26 on low water) so this could give false optimism on a very long equalisation if a lot of water was lost..

Does anybody want to check my calculation?

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

I think this is a good point. Not sure exactly what the "calculation" is as we (I) don't know the electrolyte capacity to the top of the plates, and thence to the max fill point. But I do know that when my electrolyte is getting low, the Smartgauge tends to get slightly optimistic - with the acid concentration being higher for a given SoC, the rested OC voltage is a little higher. So inevitably a prolonged equalise without topping up will increase sg readings simply because there is less water.  However, 3 hours at 3.5A or whatever, isn't going to electrolyse a lot of water so the OP has still desulphated the batteries significantly. If he tops up, it can be a bit difficult to properly mix it all up so the sg will take a bit of a nose dive for while until it is all properly mixed.

[canals are us?]

Hi, thanks everyone.

Unfortunately I have no IR thermometer so don't know what temp they are, all I can say is they feel cold. The water level has never dropped while doing the EC and is right up to full as topped them up a few weeks ago. I am going to give them today and see if cell 5 recovers. If not probably may bin and buy 4 more, we'll see.

Is putting them in series like what is in the picture of current pair? Ie 2 separate pairs of batteries. Post 42. 

James 

Edited March 7, 2018 by canals are us?

[WotEver]

6 minutes ago, canals are us? said:

Is paralleling them like what is in the picture of current pair? Ie 2 separate pairs of batteries. Post 42.

No. 

Your pic in post #42 shows two Batteries in series, creating a 12V source. Another two would be similarly wired, creating another 12V source. You’d then put the two 12V pairs  in parallel. 

Without drawing a diagram (because I’m on a phone). Batt 1 has +ve terminal to Batt 2 -ve. Batt 3 has +ve terminal to batt 4 -ve. Batt 1 -ve and batt 3-ve are connected together and that’s your negative feed. Batt 2 +ve and batt 4 +ve are connected together and that’s your positive feed. 

[Alan de Enfield]

[dmr]

15 minutes ago, nicknorman said:

I think this is a good point. Not sure exactly what the "calculation" is as we (I) don't know the electrolyte capacity to the top of the plates, and thence to the max fill point. But I do know that when my electrolyte is getting low, the Smartgauge tends to get slightly optimistic - with the acid concentration being higher for a given SoC, the rested OC voltage is a little higher. So inevitably a prolonged equalise without topping up will increase sg readings simply because there is less water.  However, 3 hours at 3.5A or whatever, isn't going to electrolyse a lot of water so the OP has still desulphated the batteries significantly. If he tops up, it can be a bit difficult to properly mix it all up so the sg will take a bit of a nose dive for while until it is all properly mixed.

I measured the dimensions of case and estimated the plastic thickness.

I then found that one of the makers of similar batteries (it might be Yuassa which is not ideal) gave a wet weight and dry weight so I could estimate the volume of acid, then its just a few summs.

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

[Dr Bob]

19 minutes ago, canals are us? said:

 

Unfortunately I have no IR thermometer so don't know what temp they are, all I can say is they feel cold.

James 

Where are you batteries ie in  the heated part of the boat or in the bilge area in an unheated part? Can you guess the temp? If 5°C then the SG could be .014 (IIRC) higher than the SG at 25°C so your 1.270 cells, if they haven't heated up, could be 90% capacity rather than 100%, assuming no offset. The liquid and plates will have heated a bit with the equalisation current but maybe not that much.

Give it another go before you ditch these two. They may not be that bad.

[nicknorman]

9 minutes ago, dmr said:

I measured the dimensions of case and estimated the plastic thickness.

I then found that one of the makers of similar batteries (it might be Yuassa which is not ideal) gave a wet weight and dry weight so I could estimate the volume of acid, then its just a few summs.

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

In that case you are jolly clever!

1 minute ago, Dr Bob said:

Where are you batteries ie in  the heated part of the boat or in the bilge area in an unheated part? Can you guess the temp? If 5°C then the SG could be .014 (IIRC) higher than the SG at 25°C so your 1.270 cells, if they haven't heated up, could be 90% capacity rather than 100%, assuming no offset. The liquid and plates will have heated a bit with the equalisation current but maybe not that much.

Give it another go before you ditch these two. They may not be that bad.

I believe the OP has one of those temperature-compensating dial hydrometers? Perhaps he could confirm? It's an important point because if there has been no temperature compensation, the sgs are quite a bit worse than we at first thought.

[Dr Bob]

3 minutes ago, nicknorman said:

 

I believe the OP has one of those temperature-compensating dial hydrometers? Perhaps he could confirm? It's an important point because if there has been no temperature compensation, the sgs are quite a bit worse than we at first thought.

Oops sorry Nick, I hadnt realised it was the temp compensated ones. Yes, as per my post, I reckon 15°C drop in temp could mean a 0.014 change in sg which could be 10% capacity difference (ish) if you were using one of the 'floaty ball' type hydrometers.

[canals are us?]

22 minutes ago, WotEver said:

No. 

Your pic in post #42 shows two Batteries in series, creating a 12V source. Another two would be similarly wired, creating another 12V source. You’d then put the two 12V pairs  in parallel. 

Without drawing a diagram (because I’m on a phone). Batt 1 has +ve terminal to Batt 2 -ve. Batt 3 has +ve terminal to batt 4 -ve. Batt 1 -ve and batt 3-ve are connected together and that’s your negative feed. Batt 2 +ve and batt 4 +ve are connected together and that’s your positive feed. 

A diagram would be great when you have got time!

 

7 minutes ago, Dr Bob said:

Where are you batteries ie in  the heated part of the boat or in the bilge area in an unheated part? Can you guess the temp? If 5°C then the SG could be .014 (IIRC) higher than the SG at 25°C so your 1.270 cells, if they haven't heated up, could be 90% capacity rather than 100%, assuming no offset. The liquid and plates will have heated a bit with the equalisation current but maybe not that much.

Give it another go before you ditch these two. They may not be that bad.

They are in a modern trad engine bay on top of the swim in an unheated area. I have just put a weather station in to get a temp reading of the batteries location. I took the readings with this from ebay. https://www.ebay.co.uk/itm/ATC-Glycol-Refractometer-Auto-Car-Fluid-Battery-Antifreeze-Acid-Engine-Tester-UK/122874506527?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Off to take readings again.

Many thanks all.

  James

[canals are us?]

New readings       previous

Bat 1

1 = 1.26                 1.260

2 = 1.24.7               1.250

3 = 1.26.5               1.270

bat 2

4 = 1.25                  1.25.5

5 = 1.24.8                1.25.0

6 = 1.26.3                1.27.0

As you can see the  new readings on the left are lower than yesterday readings on the right! Is this due to temp differences? I have put my weather station in the battery box next to the batteries and it's reading 11 degrees.

James

Edited March 7, 2018 by canals are us?

[WotEver]

19 minutes ago, canals are us? said:

As you can see the  new readings on the left are lower than yesterday readings on the right! Is this due to temp differences? I have put my weather station in the battery box next to the batteries and it's reading 11 degrees.

Possibly. Or maybe they’re at a slightly lower state of charge since yesterday? Presumably you’ve been using them?

[canals are us?]

3 minutes ago, WotEver said:

Possibly. Or maybe they’re at a slightly lower state of charge since yesterday? Presumably you’ve been using them?

Turned the 12 volt fridge and freezer back on after doing the EC last night, so yes was using the battery power. I also turned the victron charger to charger only as well. battery monitor said 104% SOC this morning.

James

[canals are us?]

Battery 1

1 =  1.25.8

2 =  1.24.5

3 = 1.26.5

Battery 2

4 = 1.25

5 = 1.24.8

6 = 1.26.5

Would the reducing results stem from cold batteries or just time to finish an EC, ie as best as they will get? Battery box temperature 9 degrees and no heating on in boat. Yesterday SFS lit.

Would you continue equalising?

James

Edited March 7, 2018 by canals are us?

[MtB]

2 hours ago, canals are us? said:

As you can see the  new readings on the left are lower than yesterday readings on the right! Is this due to temp differences?

 

Hard to say without knowing which instrument you are using to measure the SG. Could tell tell us please?

Some are temp compensated, others not. Or have you already said what you ere using?

[canals are us?]

27 minutes ago, Mike the Boilerman said:

 

Hard to say without knowing which instrument you are using to measure the SG. Could tell tell us please?

Some are temp compensated, others not. Or have you already said what you ere using?

Hi Mike.

One of these.  https://www.ebay.co.uk/itm/ATC-Glycol-Refractometer-Auto-Car-Fluid-Battery-Antifreeze-Acid-Engine-Tester-UK/122874506527?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Thanks. James

[nicknorman]

Just now, canals are us? said:

Hi Mike.

One of these.  https://www.ebay.co.uk/itm/ATC-Glycol-Refractometer-Auto-Car-Fluid-Battery-Antifreeze-Acid-Engine-Tester-UK/122874506527?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Thanks. James

Those refractometers are intrinsically temperature compensated. If you think about it, you put a tiny drop of fluid onto the slide and then close the lid which spreads the fluid out over a wide area, very thinly. Thus the fluid assumes the temperature of the refractometer almost instantaneously. Obviously it is the temperature of the fluid on the slide, not the temperature of the fluid still in the battery, that is relevant. The device itself can of course be calibrated with a drop of pure water, but it shouldn't need it to operate over quite a wide temperature range. The instructions say "Equipped with ATC (Automatic Temperature Compensation), can automatically adjust itself to correct temperature discrepancies while being used."

[smileypete]

3 hours ago, canals are us? said:

Hi, thanks everyone.

Unfortunately I have no IR thermometer so don't know what temp they are, all I can say is they feel cold. The water level has never dropped while doing the EC and is right up to full as topped them up a few weeks ago. I am going to give them today and see if cell 5 recovers. If not probably may bin and buy 4 more, we'll see.

Is putting them in series like what is in the picture of current pair? Ie 2 separate pairs of batteries. Post 42. 

James

I'd not worry about it, just use normally and try to do some EQ on solar throughout the summer.

1.250 SG is about 85% charged at 10°C, so cell 5 as lost about 15% of capacity. Not ideal but not the end of the world either.

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

I've had some good success desulphating and it's not overly complicated, but it's not an easy off the shelf answer either. Most boaters probably prefer to just get new batts and be done with it when things have gone a little too far.

Edited March 7, 2018 by smileypete

[Dr Bob]

2 minutes ago, nicknorman said:

Those refractometers are intrinsically temperature compensated. If you think about it, you put a tiny drop of fluid onto the slide and then close the lid which spreads the fluid out over a wide area, very thinly. Thus the fluid assumes the temperature of the refractometer almost instantaneously. Obviously it is the temperature of the fluid on the slide, not the temperature of the fluid still in the battery, that is relevant. The device itself can of course be calibrated with a drop of pure water, but it shouldn't need it to operate over quite a wide temperature range. The instructions say "Equipped with ATC (Automatic Temperature Compensation), can automatically adjust itself to correct temperature discrepancies while being used."

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.