Equalising

[WotEver]

While an equalisation charge is intended to removed sulfation (or is it sulphation?) a secondary purpose is to stir the electrolyte which otherwise stratifies.

 

There's a chance that the low cell's SG will increase and match the others. I've read an article to specifically apply an equalisation charge when there is a mismatch in SG.

That's because an Equalisation charge's primary purpose is to equalise the cells - there's a clue in the name.

 

Desulphation is a secondary benefit.

 

Destratification is a third benefit.

 

Of course, a disadvantage is increased plate corrosion.

[MtB]

Dave's estimate of my reduced battery capacity is remarkably accurate. Before starting cruising yesterday the SG was reading 51% with 61AH drawn from the fully charged* batteries. 3/5 of supposed new capacity.

 

* Fully charged in this case means charged to 100% on the SG, tail current of about 5%, followed by 2 hours of equalising at 31.6V.

[WotEver]

 

* Fully charged in this case means charged to 100% on the SG, tail current of about 5%, followed by 2 hours of equalising at 31.6V.

Doesn't sound like fully charged to me Mike. More like maybe 90%.

[MtB]

Doesn't sound like fully charged to me Mike. More like maybe 90%.

 

 

Hmmm ok, so does the equalising at 8A for two hours not count towards charging? What would you suggest 'counts' as fully charged after equalising?

Or are you basing your comments on the SG results I posted the other day?

(Recorded after the two hours of equalising.)

[WotEver]

 

Hmmm ok, so does the equalising at 8A for two hours not count towards charging? What would you suggest 'counts' as fully charged after equalising?

 

Or are you basing your comments on the SG results I posted the other day?

 

(Recorded after the two hours of equalising.)

5% tail current sounds like three hours or so off full, so the 2 hours at elevated voltage would have helped, although the bubbles caused by gassing will have probably decreased the charge rate.

 

You really need to get charging at 14.8V down to around 2% or at least 'no change over 45 minutes'. THEN you can Equalise.

 

Tony

 

Note that the 8A at high voltage isn't all going into the battery. A substantial amount of that current is simply going towards gassing.

[MtB]

Hmmm so considering my OP and the earlier replies, your view is that it is pointless running the 'desulphation cycle' untill the after the tail current stabilises for 45 min?. This is at variance with the some of the other answers!

 

Looks like I need to set up the donkey battery bank as to fully charge as you describe IS going to take ten hours or so.

[nicknorman]

Hmmm so considering my OP and the earlier replies, your view is that it is pointless running the 'desulphation cycle' untill the after the tail current stabilises for 45 min?. This is at variance with the some of the other answers!

 

Looks like I need to set up the donkey battery bank as to fully charge as you describe IS going to take ten hours or so.

 

Another way of looking at it is, having done your 2hr EQ, to revert to the normal charge voltage, leave for a few minutes for bubbles to disperse, and check the charging current. Although folk talk about 2% or even 1%, actually fully charged on reasonably new batteries is likely to be more like 0.25% or less. On our 450AH bank I get below 1A when it really is fully charged.

[MtB]

Another way of looking at it is, having done your 2hr EQ, to revert to the normal charge voltage, leave for a few minutes for bubbles to disperse, and check the charging current. Although folk talk about 2% or even 1%, actually fully charged on reasonably new batteries is likely to be more like 0.25% or less. On our 450AH bank I get below 1A when it really is fully charged.

 

 

How long did it take to get down to that 0.25% Nick? About 12 hours I'm imagining!

 

And to answer your previous question, my battery model is Yuasa DCB105-6ET 225AH (20HR) according to the label.

 

Thank you to everyone for your replies to date. Much appreciated. I feel I'm getting a clearer understanding now... (some way to go yet though!)

[nicknorman]

How long did it take to get down to that 0.25% Nick? About 12 hours I'm imagining!

 

At least! I'm not suggesting you should run your genny for >12 hrs, I'm just pointing out that stopping at 2% or whatever, is a compromise.

[nicknorman]

And to answer your previous question, my battery model is Yuasa DCB105-6ET 225AH (20HR) according to the label.

 

Ok so there are similar to Trojan T105s bynthe look of it. Have a look at the charging info here:

 

http://www.thebatteryshop.co.uk/dcb105-6et-yuasa-pro-spec-battery-6v-225ah-4507-p.asp

 

It says charge at (24v system) at 28.6v to 29.2v until the current falls to 0.9 to 2.7%. But remember those voltages will be at 25C and if at 5C you need to add 1v.

 

Then you finish the charge at constant current of between 0.9% and 2.7% until the voltage reaches 30v to 32.4v (again, add 1v per 20C below 25C) or until the dV/dt is less than 0.035 (but it doesn't say what unit of time!).

 

So for EVERY CHARGE you should be finishing with no less than 30v, or 31v at 5C, if you want to fully comply with the manufacturer's recommendations.

 

Oh, better link to the manufacturer's instructions here:

 

http://news.yuasa.co.uk/wp-content/uploads/2014/09/Pro-Spec-leaflet.pdf

 

Further edit, sorry I was looking at the wrong capacity battery when I calculated the current percentages, should be 1% to 3% which makes more sense!

Edited January 3, 2017 by nicknorman

[dmr]

 

 

How long did it take to get down to that 0.25% Nick? About 12 hours I'm imagining!

 

And to answer your previous question, my battery model is Yuasa DCB105-6ET 225AH (20HR) according to the label.

 

Thank you to everyone for your replies to date. Much appreciated. I feel I'm getting a clearer understanding now... (some way to go yet though!)

 

I don't think I could get to 0.25%, though I think it depends on how old the batteries are. I did see about 0.5% in the summer (consecutive long cruising days) but this was probably when the Adverc was in the lower voltage part of its cycle.

Be aware that the Smartgage goes a bit daft for a day or two after an equalisation and shows an over rapid discharge. I don't know if this is a Smartguage feature or a real battery voltage anomaly.

 

and Mike, I assume you don't need your lock hobbler today?, rather frozen here.

 

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

[nicknorman]

, rather frozen here.

 

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

(OT but it's a balmy 9C here in the "frozen north"!)

[cuthound]

Ideally you shouldn't start an equalising charge (at elevated voltsge) until the battery is fully changed, as measured by the tail current remaining constant for 3 x 15 minute periods.

 

If you start before that you increase plate corrosion because the battery has to be held at an elevated voltage for longer.

 

Sometimes, heavily sulphated batteries can be recovered by equalising until the battery starts gassing, stopping charging for 30 minutes and then equalising again. Repeat until the battery recovers significant or is confirmed as knackered.

[WotEver]

And Clift batteries respond best

[cuthound]

And Clift batteries respond best

Only if you have four of them

 

Edited to make the emoticon work.

Edited January 3, 2017 by cuthound

[MtB]

 

Then you finish the charge at constant current of between 0.9% and 2.7% until the voltage reaches 30v to 32.4v (again, add 1v per 20C below 25C) or until the dV/dt is less than 0.035 (but it doesn't say what unit of time!).

 

 

 

Thanks Nick.

 

The thing is, my expensive Sterling Pro Charge Ultra doesn't appear to offer a constant current option.

 

Maybe this is where that little current step-up device will come into its own!

 

Incidentally I've charged the batts this evening. SoC according to the SG was 54% at start of charging. After exactly three hours (to the minute!) the SG clicked up to 100%. The charge current was 11.2A and the charge voltage 30.0.

 

And no it wasn't you suggested 100% on the SG equated to approx 90% actual SoC, my mistake. It was WotEver, earlier in this thread. And from the figures above I still think he was about right!

[WotEver]

And no it wasn't you suggested 100% on the SG equated to approx 90% actual SoC, my mistake. It was WotEver, earlier in this thread. And from the figures above I still think he was about right!

It's certainly looking that way, which just reinforces the advice not to rely on SmartGauge to tell you when your batteries are charged because it simply can't tell.

The thing is, my expensive Sterling Pro Charge Ultra doesn't appear to offer a constant current option.

It shouldn't need to. If you up the charge voltage to between 32-36V the batteries should limit the current.

(Assuming the batteries are virtually fully charged)

[MtB]

Then you finish the charge at constant current of between 0.9% and 2.7% until the voltage reaches 30v to 32.4v (again, add 1v per 20C below 25C) or until the dV/dt is less than 0.035 (but it doesn't say what unit of time!).

 

 

Yes that initially had me puzzled for a bit then I decided the same as you, the time unit needed defining.

 

So lets plug in some numbers. My charge current at 7.30 was 11.2A. Half an hour later it is 8.3A. Trouble is, the voltage was 30.0V at both readings so dV = zero. DOH!

 

Still puzzled about how to get a constant current finishing charge....

[WotEver]

 

Yes that initially had me puzzled for a bit then I decided the same as you, the time unit needed defining.

 

So lets plug in some numbers. My charge current at 7.30 was 11.2A. Half an hour later it is 8.3A. Trouble is, the voltage was 30.0V at both readings so dV = zero. DOH!

 

Still puzzled about how to get a constant current finishing charge....

I can't see why you can't do it the other way. Charge at 32V and wait for the current to drop...

[cuthound]

I can't see why you can't do it the other way. Charge at 32V and wait for the current to drop...

Exactly, unless you have a charger with a manually variable voltage (unlikely) then raise the voltage and as the battery charges it will self limit the current.

[WotEver]

Exactly, unless you have a charger with a manually variable voltage (unlikely) then raise the voltage and as the battery charges it will self limit the current.

Yup.

[MtB]

I can't see why you can't do it the other way. Charge at 32V and wait for the current to drop...

 

 

Ok how does one persuade a Sterling Pro Charge Ultra to deliver 32V?

[WotEver]

 

Ok how does one persuade a Sterling Pro Charge Ultra to deliver 32V?

Looking at the user guide... one could select Equalization/Desulph which would give 31V or you could use 'Custom Setup' which appears to allow you to set whatever you want, but it seems that the upper limit is 30.2V.

 

Or the optional Battery Chemistry Module looks like it may be able to do it - maybe worth a phone call. In fact, if you phone them they might be able to offer you a solution to raising that 30.2V upper limit.

Edited January 6, 2017 by WotEver

[MtB]

Looking at the user guide... one could select Equalization/Desulph which would give 31V or you could use 'Custom Setup' which appears to allow you to set whatever you want, but it seems that the upper limit is 30.2V.

 

Or the optional Battery Chemistry Module looks like it may be able to do it - maybe worth a phone call. In fact, if you phone them they might be able to offer you a solution to raising that 30.2V upper limit.

 

 

Well yes, which is why I asked!

 

Can anyone suggest a charger that can be set to 32V?

Or are these impossible charge voltages specified by manufacturers to stave off guarantee claims?

[WotEver]

 

 

Well yes, which is why I asked!

 

Can anyone suggest a charger that can be set to 32V?

 

Or are these impossible charge voltages specified by manufacturers to stave off guarantee claims?

At a quick glance at the specs this one appears to http://www.asap-supplies.com/30-amp-battery-charger-for-24-volt-batteries-61112313