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Battery performance issue


Richardcn

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Hi all

 

I have two 6v US Battery 2200 XC2's which have been installed for about a year now but I'm concerned with their performance.

 

A quick bit of background...(btw we are CCers)

I bought these about a year before installing them whilst they were on offer. I had intended to install them straight away but the available charge from our solar system kicked back up again and the old batteries held on until the following winter (2018/2019). The 2200's were kept charged throughout that period and equalised from time to time, I try to look after my batteries. I measured the SG of all cells after purchase (once fully charged) and found them to be quite low so I contacted the manufacturer for advice, as I had some other questions as well. They felt that the readings (which now I can't find but possibly 1.260) were "...just within tolerance..." so I left it at that, although I wasn't completely convinced.

 

For the first few months after installation performance was poor but I put that down to them requiring a 'running in period'. However, the poor performance continued. I charge to tail current (when not using solar) so I know when they are 100% or near as. The voltage (12.7v) from full was dropping way to quickly and using the amps counter on our meter I estimated a capacity of approx 100 A/hrs, the rated capacity being 225 A/hrs! At first I thought I must have bought a pair of duds (“on offer”) but being well over a year since purchase there was little chance of getting a refund so we plodded on with them.

 

However....

 

After a couple more months things started to improve, I was seeing 12.8v when full (after surface charge was dissipated) and capacity was getting closer to what I expected. Obviously I was happy about that so I didn't think much more about it until I topped up (to correct level) with distilled water... straight back down to the previous poor performance again!!! I've just finished completing the same process over the last few months and the same has happened again, albeit that I haven't yet refilled, which leads to my theory and question.

 

I think that the supplier could possibly have carried out the initial fill with the wrong electrolyte strength. The levels at the moment are well down, less than a cm from the top of the plates but the batteries are performing much in line with expectations (as they were prior to the last top-up) with SG's of 1.295/1.300. I don’t really want to go through the same process again if I can avoid it, especially as the solar is starting to ramp down now and the necessity to survive for 3/4 days between charges will soon be upon us.

 

Might a carefully measured (and staged?) top-up with an electrolyte solution, rather than only distilled water be appropriate in this case? Your thoughts gentlemen please.

 

Regards

Richard

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Remember that sulphation caused by batteries being left in a discharged state takes sulpher from the acid so the specific gravity drops. I suspect they were sulphated when supplied to you. You can still get "fully charged" voltage readings with sulphated batteries. When sulphated they charge faster and discharge faster than non-sulphated batteries.

 

The strength of the acid must have an effect on voltage but if you make it over strong you then increase the plate erosion, its a balancing act. Although not impossible I find the idea of the initial filling with understrength acid unlikely.

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Many thanks for your thoughts Tony. I did wonder if sulphation prior to sale was the problem but the subsequent improvement in performance led me away from that idea. Even if that was (or is still) the case then I think I would rather accept that the battery life might be somewhat reduced whilst retaining the capacity that I seem to have regained from the higher (or restored) electrolyte strength. My aim really is to retain the current acceptable performance without having to keep the fluid levels dangerously low and having to top up a small amount far more frequently. In that scenario topping up with battery acid and thus retaining the current SG seems to be a viable solution.

 

Regards

Richard

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6 hours ago, Bobbybass said:

I was always told that the electrolyte should only be 1/4 inch above the plates ?. My previous batteries were great and lasted 5 years.

I think that may now be superseded and it was above the separators anyway, the plates are normally a little lower down. The best advice today with low maintenace batteries around isi t just top up the the level mark fitted by most manufacturers. (Not easy to see on far too many canal boats.)

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I too have wondered about this 'weak acid' thing (and posted my thoughts on here) where topping up to the level marker results in a sharp reduction in battery capacity, having experienced the same.

 

It strikes me that battery acid is expensive stuff, and when a battery supplier fills with acid at the point of sale, there must be a temptation to only fill to cover the plates rather than up to the level marker. It isn't a small amount of acid that gets saved when this is done. Topping up my four Trojanoids from top of plates up to level marker takes over three litres of water. That's three litres of acid mine were potentially missing when I bought them!

 

So when perhaps not very well informed workshop staff are instructed by the boss to only fill to cover the plates, they obediently do it and large amounts of expensive acid are saved. I'd be amazed if this does not happen widely.  How much does a glass carboid of sulphuric acid cost anyway? a few hundred quid delivered, I bet. 

 

So bottom line in my view is when buying batteries, don't just check the terminal voltage is 12.7, it is crucial to make sure it is 12.7v with electrolyte up at the level marker.

 

 

 

Edited by Mike the Boilerman
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9 hours ago, Bobbybass said:

I was always told that the electrolyte should only be 1/4 inch above the plates ?. My previous batteries were great and lasted 5 years.

Trojan batteries, and I expect US too as they are of a similar ilk (lead antimony), use significant water as part of their design. The correct level is just below the filler well, giving considerable margin for water usage before the plates are exposed.

 

Other types of battery (lead calcium found in many starter-type leisure batteries) use far less water and so need less depth of electrolyte above the top of the plates.

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I think I'll order some acid and make up a solution, after some further research, then top up in stages and monitor the effect over the next few months. That way I can always dilute back down with distilled water if I get it horribly wrong. Also if, when getting low again, the electrolyte is a bit too strong then I'll amend my watering routine to ensure the levels don't go down past midway. That should allow me to retain an improved performance without endangering plate damage by a missed top-up. What the meter is telling me will help me to spot when levels are low in future, once I've recalibrated my brain to take into account the better performance.

 

Regards

Richard

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I was always tought never to add acid to a battery except if supplied dry.  Thereafter, just distilled water. There may be exceptions for someone who knows exactly what they're doing, but I'm not sure that's layman's territory as SG changes with charge. How will you know when you have the concentration right?

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As yet I'm not sure but either the batteries were wrongly filled or I've lost concentration through sulphation and that has led to unacceptable performance. Once I've done my research I'll hopefully have a better idea but either way I'll be stepping very carefully. It should be easy enough to find out what batteries are normal filled with though and go from there.

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5 hours ago, Sea Dog said:

I was always tought never to add acid to a battery except if supplied dry.  Thereafter, just distilled water. There may be exceptions for someone who knows exactly what they're doing, but I'm not sure that's layman's territory as SG changes with charge. How will you know when you have the concentration right?

 

If you top up with acid, then to ensure the acid is the correct strength the battery MUST be fully charged first.

 

Also mixing acid to the correct strength can be very dangerous if you don't know what you are doing.

 

Protective equipment (acid proof gloves & apron, together with goggles) is essential. Keep a container of sodium bicarbonate handy to neutralise any spills. Ideally you will need a calibrated thermometer and calibrated hydrometer to ensure the acid really is the sg  thst you want it to be.

 

 

The correct mix for lead acid batteries is about 35% sulphuric acid to 65% distilled water, depending upon final sg strength. It can be purchased ready mixed at this strength.

 

If you purchase stronger acid, you must add the acid to water to achieve the correct sg, never the other way round, as the results can be somewhat explosive.

 

Magpie Patrick edit (at Curhounds request) you need to add a little strong acid to a larger volume of water, NOT the other way round, so you acid mix starts as water and gets stronger. 

 

 

Edited by magpie patrick
acid and water transposed
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5 hours ago, Mike the Boilerman said:

I too have wondered about this 'weak acid' thing (and posted my thoughts on here) where topping up to the level marker results in a sharp reduction in battery capacity, having experienced the same.

 

It strikes me that battery acid is expensive stuff, and when a battery supplier fills with acid at the point of sale, there must be a temptation to only fill to cover the plates rather than up to the level marker. It isn't a small amount of acid that gets saved when this is done. Topping up my four Trojanoids from top of plates up to level marker takes over three litres of water. That's three litres of acid mine were potentially missing when I bought them!

 

So when perhaps not very well informed workshop staff are instructed by the boss to only fill to cover the plates, they obediently do it and large amounts of expensive acid are saved. I'd be amazed if this does not happen widely.  How much does a glass carboid of sulphuric acid cost anyway? a few hundred quid delivered, I bet. 

 

So bottom line in my view is when buying batteries, don't just check the terminal voltage is 12.7, it is crucial to make sure it is 12.7v with electrolyte up at the level marker.

 

 

 

That would save more by skimping on the lead

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Thanks for that advice. My initial research leads me to think that a pre-mixed battery acid solution should be fine for what I'm doing. After all, I'm not trying to increase the acidity but to maintain it at normal fill levels. The SG of solutions that I've looked at are well below my current, fully charged SG's so unless I'm missing something (entirely possible!), I don't see a problem. As I said though, I'd be filling in stages to allow room for dilution if necessary.

 

Regards

Richard

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Does anyone know roughly how much fluid is needed to top up a cell on these 6v batteries, top of cells to full level? I just need to make sure that I order the right amount of fluid but I've never measured when topping up. 1 1/2 litres (for 6 cells) would seem like quite a lot, although maybe not?

 

Regards

Richard

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2 hours ago, cuthound said:

 

If you top up with acid, then to ensure the acid is the correct strength the battery MUST be fully charged first.

 

Also mixing acid to the correct strength can be very dangerous if you don't know what you are doing.

 

Protective equipment (acid proof gloves & apron, together with goggles) is essential. Keep a container of sodium bicarbonate handy to neutralise any spills. Ideally you will need a calibrated thermometer and calibrated hydrometer to ensure the acid really is the sg  thst you want it to be.

 

 

The correct mix for lead acid batteries is about 35% sulphuric acid to 65% distilled water, depending upon final sg strength. It can be purchased ready mixed at this strength.

 

If you purchase stronger acid, you must add the water to the acid to achieve the correct sg, never the other way round, as the results can be somewhat explosive.

 

 

Why is acid always added to water, and not the reverse?

 

 

 

A large amount of heat is released when strong acids are mixed with water. Adding more acid releases more heat. If you add water to acid, you form an extremely concentrated solution of acid initially. So much heat is released that the solution may boil very violently, splashing concentrated acid out of the container! If you add acid to water, the solution that forms is very dilute and the small amount of heat released is not enough to vaporize and spatter it. So Always Add Acid to water, and never the reverse.

Author: Fred Senese senese@antoine.frostburg.edu

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37 minutes ago, Harpur Hill said:

 

Why is acid always added to water, and not the reverse?

 

 

 

A large amount of heat is released when strong acids are mixed with water. Adding more acid releases more heat. If you add water to acid, you form an extremely concentrated solution of acid initially. So much heat is released that the solution may boil very violently, splashing concentrated acid out of the container! If you add acid to water, the solution that forms is very dilute and the small amount of heat released is not enough to vaporize and spatter it. So Always Add Acid to water, and never the reverse.

Author: Fred Senese senese@antoine.frostburg.edu

 

Yes that what I thought I had written. I'll amend my original if the edit time hasn't elapsed.

 

EDIT - I have missed the post editing window, so I have reported my own post asking the moderators to change it, just in case anyone tries to follow the incorrect advice and add water to a strong acid.

Edited by cuthound
See last paragraph above
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2 hours ago, Richardcn said:

Does anyone know roughly how much fluid is needed to top up a cell on these 6v batteries, top of cells to full level? I just need to make sure that I order the right amount of fluid but I've never measured when topping up. 1 1/2 litres (for 6 cells) would seem like quite a lot, although maybe not?

 

Regards

Richard

I have 4 X T105s and I used between about a lt last week to top them up I think,

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6 hours ago, nicknorman said:

Trojan batteries, and I expect US too as they are of a similar ilk (lead antimony), use significant water as part of their design. The correct level is just below the filler well, giving considerable margin for water usage before the plates are exposed.

 

 

Well that's good to know because my new ones seemed too full, but I guess they're ok. Good performance anyway on my last trip away.

 

I think I might have wrecked my last set of Trojans by topping them up with cheap deionised water from a discount shop. For all I know it was just water.

 

This time I'm taking no chances and bought a gallon of distilled water from a proper supplier. It even came with a certificate to show the purity.

 

The new Trojans (3 x T1275) don't seem to use very much water though. I bought them last March and still haven't topped them up. They're still full.

 

 

Edited by blackrose
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3 minutes ago, blackrose said:

 

Well that's good to know because my new ones seemed too full, but I guess they're ok. Good performance anyway on my last trip away.

 

I think I might have wrecked my last set of Trojans by topping them up with cheap deionised water from a discount shop. For all I know it was just water.

 

This time I'm taking no chances and bought a gallon of distilled water from a proper supplier. It even came with a certificate to show the purity.

 

The new Trojans (3 x T1275) don't seem to use very much water though. I bought them last March and still haven't topped them up. They're still full.

 

 

 

Topping up batteries with tap water wrecks them in the long term, because the impurities can build up into growths that can short the plates, but it does take a long time.

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3 hours ago, cuthound said:

 

If you top up with acid, then to ensure the acid is the correct strength the battery MUST be fully charged first.

 

Also mixing acid to the correct strength can be very dangerous if you don't know what you are doing.

 

Protective equipment (acid proof gloves & apron, together with goggles) is essential. Keep a container of sodium bicarbonate handy to neutralise any spills. Ideally you will need a calibrated thermometer and calibrated hydrometer to ensure the acid really is the sg  thst you want it to be.

 

 

The correct mix for lead acid batteries is about 35% sulphuric acid to 65% distilled water, depending upon final sg strength. It can be purchased ready mixed at this strength.

 

If you purchase stronger acid, you must add the water to the acid to achieve the correct sg, never the other way round, as the results can be somewhat explosive.

 

I’m pretty sure you should add the acid to water, not the other way round, as the acid wants to grab as much water as it can.

 

ETA:  just seen the other posts pointing this out.

Edited by dor
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8 hours ago, Richardcn said:

I think I'll order some acid and make up a solution, after some further research, then top up in stages and monitor the effect over the next few months. That way I can always dilute back down with distilled water if I get it horribly wrong. Also if, when getting low again, the electrolyte is a bit too strong then I'll amend my watering routine to ensure the levels don't go down past midway. That should allow me to retain an improved performance without endangering plate damage by a missed top-up. What the meter is telling me will help me to spot when levels are low in future, once I've recalibrated my brain to take into account the better performance.

 

Regards

Richard

Well I really hope you've had the appropriate training and have the proper equipment. I have but whilst 12.80 electrolyte is available I'm going nowhere near concentrated sulphuric acid!

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4 hours ago, ditchcrawler said:

I have 4 X T105s and I used between about a lt last week to top them up I think,

 

35 minutes ago, Mike the Boilerman said:

 

About 750ml per battery in the case of my Trojanoids. 

 

 

 

Great, many thanks.

 

Regards

Richard

50 minutes ago, Sir Nibble said:

Well I really hope you've had the appropriate training and have the proper equipment. I have but whilst 12.80 electrolyte is available I'm going nowhere near concentrated sulphuric acid!

Don't worry, I won't be touching anything other than a pre prepared battery acid solution.

 

Regards

Richard

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