16.8V charger for equalising Trojans?

[WotEver]

24 minutes ago, smileypete said:

Why not ask Trojan and see what they say?

I’ve done just this. I wrote earlier when i suggested it to Nick. Obviously I’ll report back what they say. 

[jenevers]

I’ve never strictly monitored this but I’ve never noticed my Trojans getting warm, even when I can smell fumes (can’t remember the exact chemical) after some high voltage charging.

[WotEver]

3 minutes ago, jenevers said:

I’ve never strictly monitored this but I’ve never noticed my Trojans getting warm, even when I can smell fumes (can’t remember the exact chemical) after some high voltage charging.

It’s not that then

[smileypete]

I guess heat may be a possible problem depending on climate, battery condition and batt bank size.

[WotEver]

I’ve had a reply from Trojan. It is as I suspected when I wrote...

On 25/12/2017 at 19:07, WotEver said:

It also causes heat which in theory at least will cause the plates to move around, exacerbating the effect. 

Their reply...

The main reason charge current is limited is due to concerns over heat. When batteries charge, the charge current generates heat in the battery. Heat is the enemy of lead acid batteries as it increases grid corrosion which is a failure mechanism.

They said no more nor less - that’s not a selective quote - that is the entirety of their reply.

 

[WotEver]

I’ve replied, asking if they can comment on Nick’s observation...

I don’t really buy the heat thing. The plates are in intimate contact with the electrolyte which has a fairly high specific heat capacity, and I never see any rise in electrolyte temperature associated with fast charge rates.

[nicknorman]

2 minutes ago, WotEver said:

I’ve had a reply from Trojan. It is as I suspected when I wrote...

Their reply...

 

 

They said no more nor less - that’s not a selective quote - that is the entirety of their reply.

 

Interesting. However not very scientific IMO! I suggest that heat isn’t the enemy, it is temperature!

So perhaps the issue is that fast charging does increase the battery temperature a bit (although I’ve never noticed it) so the next question is, is it absolute temperature that is the issue, or differential temperature. If absolute, I suggest we don’t need to worry about fast charging batteries in typical UK temperatures especially in winter!

Another question - which generates the more heat, charging at C5 (20% of capacity) or discharging at the same rate? Since the chemical reaction is broadly thermodynamically neutral, I suggest that these two cases are much the same thermally. They seem not to recommended a maximum discharge rate.

[WotEver]

Nick, rather than me copy/paste your questions I’ll pm you the email address of the Trojan tech  

 

[Dr Bob]

11 minutes ago, nicknorman said:

Interesting. However not very scientific IMO! I suggest that heat isn’t the enemy, it is temperature!

So perhaps the issue is that fast charging does increase the battery temperature a bit (although I’ve never noticed it) so the next question is, is it absolute temperature that is the issue, or differential temperature. If absolute, I suggest we don’t need to worry about fast charging batteries in typical UK temperatures especially in winter!

Another question - which generates the more heat, charging at C5 (20% of capacity) or discharging at the same rate? Since the chemical reaction is broadly thermodynamically neutral, I suggest that these two cases are much the same thermally. They seem not to recommended a maximum discharge rate.

Watch out, we are in danger of mixing up chemical reactions. The charge and discharge reaction is thermodaynamically neutral ie no heat is give off or taken in. If it was then on discharge the battery would need heat added to work. I think the heating (or temperature they are talking about) is the heat generated during charge but not from the lead sulphate to lead (and lead oxide) reaction. Presumably therefore this heat is from the current going through the internal resistance (oh no!!!). Simiarlary on high discharge we get heat - again probably via the internal resistance. You cant get heat on charge and discharge from the same reversible reaction - but you can from another 'reaction' that always goes the same way regardless of direction of charge (in or out). If it isnt internal resistance then it is some other side reaction that generates heat.

If then it is heat generated at a specific point, the degradation of the plates could easily be speeded up by these pin point heat sources even though the overall battery temp does not rise. Think of tiny 3 bar electric fires all over the plates. The electrolyte could be a pretty constant temperature but where the heat is generated on the plate surface (or internals) could be significantly higher particularly if it is an internal resistance issue at the micro level.

I would guess it is more of a localised temperature issue (or indeed a temperature differential here) rather than the overall temperature of the battery. I've never seen anything saying try and keep your batteries below 30°C.

[nicknorman]

1 hour ago, Dr Bob said:

Watch out, we are in danger of mixing up chemical reactions. The charge and discharge reaction is thermodaynamically neutral ie no heat is give off or taken in. If it was then on discharge the battery would need heat added to work. I think the heating (or temperature they are talking about) is the heat generated during charge but not from the lead sulphate to lead (and lead oxide) reaction. Presumably therefore this heat is from the current going through the internal resistance (oh no!!!). Simiarlary on high discharge we get heat - again probably via the internal resistance. You cant get heat on charge and discharge from the same reversible reaction - but you can from another 'reaction' that always goes the same way regardless of direction of charge (in or out). If it isnt internal resistance then it is some other side reaction that generates heat.

If then it is heat generated at a specific point, the degradation of the plates could easily be speeded up by these pin point heat sources even though the overall battery temp does not rise. Think of tiny 3 bar electric fires all over the plates. The electrolyte could be a pretty constant temperature but where the heat is generated on the plate surface (or internals) could be significantly higher particularly if it is an internal resistance issue at the micro level.

I would guess it is more of a localised temperature issue (or indeed a temperature differential here) rather than the overall temperature of the battery. I've never seen anything saying try and keep your batteries below 30°C.

Yes I agree with your points on the chemical reaction. I said “the” reaction because it’s the same reversible reaction for both charge and discharge. And yes I think the heat is generated from internal resistance, the same for both charge and discharge. That was my point - if charge current needs to be limited to avoid undesirable heating effects, surely the same applies to discharge current?

Oh except that I don’t understand your third sentence.

[WotEver]

Trojan’s response. It appears to me that they’re simply being careful:

Hi Tony,

Since batteries work based on an electro-chemical reaction, it is not always possible to accurately determine what will happen.  Ambient temperature, battery state of charge, battery age and charge current / voltage play into to the equation.  If time is of the essence when charging (and needs to be minimized) we generally say that flooded batteries can be charged with 20% of their C20 rating.  However, the caveat is that if the battery temperature increases more than 20 degrees F above ambient temperature, that is an indication that the batteries are not properly accepting the current and it is just being converted into heat.  There are “schools of thought” which say that a battery that is 50% discharged can safely accept 50% of its C20 rating when charging or if it’s 80% discharged it can accept 80% of its C20 rating.  Trojan uses a very dense paste formula.  We are also pretty conservative in terms of proper care / maintenance of our batteries.  Our experience shows that 13% of C20 does not generate damaging heat when charging.

 

Please let me know if you have other questions.

 

Have a good day,

[Dr Bob]

3 hours ago, nicknorman said:

Yes I agree with your points on the chemical reaction. I said “the” reaction because it’s the same reversible reaction for both charge and discharge. And yes I think the heat is generated from internal resistance, the same for both charge and discharge. That was my point - if charge current needs to be limited to avoid undesirable heating effects, surely the same applies to discharge current?

Oh except that I don’t understand your third sentence.

Ok, so the heating occurs via internal resistance - so takes place both on charge and discharge. I am not really sure what 'internal resistance' means - but guess it is various pathways within the plates that current flows along - so is spread out over the whole plate area. Areas where there is more resistance will heat up more. If the resistance is at various points rather than pathways then those points will get hot (and maybe very hot) so setting up a big temperature differential to the areas where the resistance is less. The problem is more likely to be these 'hot spots' rather than the overall battery temperature.

If the above is right then the heating effect will be the same on both charge and discharge as you say.

My cheapo Lead acids lasted 6 years on my lumpy water boat which had reasonable care but very rarely seeing 150A out - nesspresso machine etc. My gut feeling says this high current out has to be bad for a battery and maybe even a few minutes at 150A gives temperature rises at the micro level which does damage without you seeing an overall significant rise in temperature.

[nicknorman]

1 hour ago, Dr Bob said:

Ok, so the heating occurs via internal resistance - so takes place both on charge and discharge. I am not really sure what 'internal resistance' means - but guess it is various pathways within the plates that current flows along - so is spread out over the whole plate area. Areas where there is more resistance will heat up more. If the resistance is at various points rather than pathways then those points will get hot (and maybe very hot) so setting up a big temperature differential to the areas where the resistance is less. The problem is more likely to be these 'hot spots' rather than the overall battery temperature.

If the above is right then the heating effect will be the same on both charge and discharge as you say.

My cheapo Lead acids lasted 6 years on my lumpy water boat which had reasonable care but very rarely seeing 150A out - nesspresso machine etc. My gut feeling says this high current out has to be bad for a battery and maybe even a few minutes at 150A gives temperature rises at the micro level which does damage without you seeing an overall significant rise in temperature.

Just on the “hotspots” thing don’t forget that if there are different current paths in parallel, the one with the higher resistance will generate less heat, not more, since it will take a smaller share of the current. Power dissipated being I^2R. Only if the resistances are in series will the greater one dissipate more power. But apart from that I don’t have a strong disagreement except to say that the metallic parts of the battery are surely in fairly intimate thermal connection with each other, just split into the +ve bits and the -ve bits. It seems unlikely that significant very localised thermal differences would occur in metallic substances which by definition conduct heat well. Incidentally it’s intersting to note that whilst Mastervolt locate their charger/Combi temperature sensors on the side of the battery (and thus measure electrolyte temperature), Victron choose to attach it to the battery -ve post which presumably is in fairly intimate thermal contact with the plate material. 

[cuthound]

The highest points of resistance on a battery are where the plates join the group bars.

These are welded joints and frequently suffer corrosion where the pure lead group bars react with the alloyed lead/calcium or lead/antimony plates. This was a major problem with the first and second generation VRSLA recombination cells with up to 75% of batteries being affected until the quality of the welding process improved.

[nicknorman]

1 hour ago, WotEver said:

Trojan’s response. It appears to me that they’re simply being careful:

Hi Tony,

Since batteries work based on an electro-chemical reaction, it is not always possible to accurately determine what will happen.  Ambient temperature, battery state of charge, battery age and charge current / voltage play into to the equation.  If time is of the essence when charging (and needs to be minimized) we generally say that flooded batteries can be charged with 20% of their C20 rating.  However, the caveat is that if the battery temperature increases more than 20 degrees F above ambient temperature, that is an indication that the batteries are not properly accepting the current and it is just being converted into heat.  There are “schools of thought” which say that a battery that is 50% discharged can safely accept 50% of its C20 rating when charging or if it’s 80% discharged it can accept 80% of its C20 rating.  Trojan uses a very dense paste formula.  We are also pretty conservative in terms of proper care / maintenance of our batteries.  Our experience shows that 13% of C20 does not generate damaging heat when charging.

 

Please let me know if you have other questions.

 

Have a good day,

Thanks, been out all afternoon so no time to email myself. One permissible charging strategy is a constant current one, I can see that one would have to be careful to set a current that the battery could easily accept to avoid a risk of excessive voltage. Also with constant voltage charging one has to remember that the battery's ability to accept charge increases with temperature, so in a hot climate with battery electrolyte temperature of say 40C, it might be relatively easy to pump enough current in to the battery to get towards thermal runaway.

But anyway for me, pushing in as much current as the batteries want to take at 14v or so (initial charge voltage) seems to be OK as the batteries are lasting well, and has the advantage of being able to pump in >100AH in an hour if we want to do a top-up on a static day. Absolutely maximising battery life is not necessarily the predominant consideration. 

Edited December 27, 2017 by nicknorman

[WotEver]

I think though that we’ve reestablished the concept that fast charging can be damaging to batteries, cheaper ones probably being more susceptible, that damage being ‘grid corrosion’ caused by a softening of the paste, warping of the plates due to heat, or a combination thereof.  

I think we’ve also established that it’s far more likely to be an issue in the summer than in the winter (in the UK), unless the batteries are old or damaged. 

Edited December 27, 2017 by WotEver

[smileypete]

8 minutes ago, nicknorman said:

But anyway for me, pushing in as much current as the batteries want to take at 14v or so (initial charge voltage) seems to be OK as the batteries are lasting well, and has the advantage of being able to pump in >100AH in an hour if we want to do a top-up on a static day. Absolutely maximising battery life is not necessarily the predominant consideration. 

I guess their advice has been arrived at over many years of experience.

OFC if a batt under >>C/8 charge mysteriously goes into boil mode one day, then the buck stops with the owner. Ebay thermostats are v cheap, so it wouldn't be too hard to have a warning beeper for each bat, eg:

https://www.ebay.co.uk/itm/W1209WK-Digital-thermostat-Temperature-Smart-Control-Sensor-50-110-C-DC-12V-/281986675443

[Richard10002]

On 22/12/2017 at 18:06, Mike the Boilerman said:

 

The custom setting on my pro charge ultra contains a very irritating gotcha. There is a circumstance which crops up from time to time which erases one’s custom settings, and it’s not a five second job to put them back in again. 

I can’t remember what the circumstance is however, other than it is bloody annoying! I’ve posted about it on here before though. 

Mike.... I'm about to buy a Pro Charge Ultra in Midland Chandlers Freaky Friday 20% off sale - think it's tomorrow.

Can you confirm that the custom setting allows you to set both absorbtion and float voltages at a max of 15.1V. I'm slightly concerned that the max for float might be lower as I cant find a specific reference to it.

I want to be able to set absorbtion and float at the same voltage, somewhere between 14.5V and 15.1V, so the absorbtion time limit doesnt affect charging.

Alternatively, I could be looking at a Victron Centaur, which seems to have a 4 hour absorbtion period, which will almost always be more than enough.

[MtB]

3 hours ago, Richard10002 said:

Mike.... I'm about to buy a Pro Charge Ultra in Midland Chandlers Freaky Friday 20% off sale - think it's tomorrow.

Can you confirm that the custom setting allows you to set both absorbtion and float voltages at a max of 15.1V. I'm slightly concerned that the max for float might be lower as I cant find a specific reference to it.

I want to be able to set absorbtion and float at the same voltage, somewhere between 14.5V and 15.1V, so the absorbtion time limit doesnt affect charging.

Alternatively, I could be looking at a Victron Centaur, which seems to have a 4 hour absorbtion period, which will almost always be more than enough.

 

No I'm afraid I can't confirm that, as mine is 24v! 

I'm reasonably sure from memory though, that the maximum selectable float voltage is the same value as the max absorption voltage on mine. 

I also STR that setting the equalisation/desulphation cycle running erases one's custom settings which is a complete ball ache. The max equalisation voltage is also too low for Trojans.

Buy the Victron. 

 

[Richard10002]

1 hour ago, Mike the Boilerman said:

 

No I'm afraid I can't confirm that, as mine is 24v! 

I'm reasonably sure from memory though, that the maximum selectable float voltage is the same value as the max absorption voltage on mine. 

I also STR that setting the equalisation/desulphation cycle running erases one's custom settings which is a complete ball ache. The max equalisation voltage is also too low for Trojans.

Buy the Victron. 

 

Very Torn on this. To save a hundred quid or so, I need to buy in the Freaky Friday Sale, so by the end of tomorrow...

I like the versatility of the Sterling, like the custom setting, and the ability to vary the power factor, and it's a bit smaller overall.

I dont think any charger has an equalisation setting to suit Trojans. My existing Sterling Inverter Charger has a 15.5V equalisation voltage, and I'd guess the Pro Charge Ultra is the same. The Victron doesnt seem to give that info.

Will I be hacked off if I lost the custom settings every 4 weeks, or 8 weeks, dependent on how often I equalise? or will I be hacked off with the inflexibility of the Victron, and pleased with the quality?

I'm leaning towards the Sterling, but will probably sleep on it

[Dr Bob]

1 hour ago, Richard10002 said:

I'm leaning towards the Sterling, but will probably sleep on it

I think the victron will be a bit lumpy to sleep on. The Sterling is a better shape to have in the bed.

[rusty69]

1 minute ago, Dr Bob said:

I think the victron will be a bit lumpy to sleep on. The Sterling is a better shape to have in the bed.

3 minutes ago, Dr Bob said:

I think the victron will be a bit lumpy to sleep on. The Sterling is a better shape to have in the bed.

Hey. I'm getting greenies for your jokes too now

[Richard10002]

Bought the Sterling....

[WotEver]

7 hours ago, Richard10002 said:

Bought the Sterling....

Let us know how you get on with it

[Sea Dog]

2 hours ago, WotEver said:

Let us know how you get on with it

He will - we'll soon see another thread starting with "My Sterling..."  

Sorry Richard, I hope it gives you many years of great service (I hesitate to say sterling service)!