Equalising

[MtB]

 

 

I think Mike describes a situation where he charges his batteries to 100%, (or near enough), on a Sunday, (perhaps over Saturday and Sunday). He then uses them without further charging over the course of the week, then he charges them again the next weekend, and so on.

 

He therefore doesn't leave them discharged to 50% for a week but, they are a bit more discharged each day until they are at 50% on say, Saturday. There is no charging over the course of the week.

 

Assuming this is a battery killing regime, we could do with identifying how many days the batteries can be discharged without charge, or how far they can be discharged before some charging should take place.

 

In fact, is it a function of time with no charging, rather than depth of discharge? I think I recall that you discharged your Trojans to 30% SoC regularly, on the basis that this encouraged them to reach max capacity.

 

If Mike had a bigger bank, such that his weeks useage only took them to 80% DoD, would they survive for many years, or would they still suffer because they havent experienced any charging for 6/7 days.

 

Could it be that, no matter how deep we discharge our batteries, they ought to have a few hours of charging every day, or every other day, or whatever, ("whatever" being less than 7 days).

 

In fact, perhaps it could be said that a battery on permanent shore power charge, and therefore constantly as close to fully charged as possible, and being charged constantly, (mostly at float), is experiencing the ideal regime.

 

Perhaps a boater who cruises for 5 or 6 hours every day, with only occasional periods where they dont cruise every day, creates close to the ideal regime for battery longevity. i.e. batteries experience some charging every day, and are charged to 100%, (as good as), every day.

 

Of those boaters who have batteries which last them for many years, I wonder what is the commonality, (deliberate or otherwise), between their charging regimes?

 

 

You have articulated very well the thoughts running through my mind here.

 

Mike (Blackrose) claims his set of (eight cheapos, I think it was) lasted him for ten years. I also remember him commenting that he has to add de-ionised water to them in such large quantities that the price of it concerns him. Litres and litres per year.

 

This suggests to me he has a generous battery bank size and he de-sulphates fiercely and regularly. My own batteries fizz a bit at the end of a charge but the electrolyte level never goes down.

[cuthound]

I don't think Mike has a battery killing regime, he just needs to charge them enough to recover the the lead sulphate, which he can only do by charging at around 32 volts for at while AFTER the tail current has remained constant for around 30-45 minutes.

 

At the dawn of my career I looked after a very old telecommunications installation, which used two batteries on a "one in use for a week", "one recharged during the week ready for use the next" and they didn't suffer, but they were equalised every month.

 

Edited for spillung (twice)

Edited January 8, 2017 by cuthound

[MtB]

But what will the domestic alternator be doing? We have to consider all possible risks. need some advice from NN and others.

 

 

What domestic alternator!

 

I have one 40A 24V alternator driven by the Kelvin vintage engine...

I don't think Mike has a battery killing regime, he just needs to charge them enough to recover the the lead sulphate, which he can only do by charging at around 32 volts for at while AFTER the tail current has remained constant for around 30-45 minutes.

 

 

 

Last night I tried a 30.3V 'finishing off' charge using the little current pump PCB. I dared not raise the voltage any higher as the batteries were fizzing audibly (still with the caps on!) and even tiny rises in the voltage made them even noisier. Was I being too timid?

[WotEver]

Okay, here's what happens to lead acid batteries which will hopefully answer some of the confusion in a few of the previous posts...

 

When you discharge a battery, even just a little bit, sulphate crystals will form on the surface of the plates. These crystals will then steadily grow and harden hour by hour, day by day. If you played with a chemistry set as a kid you might have gown an Alum crystal - it's much the same.

 

If, like Mike, you leave it a week prior to fully charging the batteries then it's apparent from his experience that some of those crystals have now hardened (it's the hardness as opposed to the size that's relevant here although the two are obviously related) to such an extent that he doesn't have the time to charge for long enough on a Sunday to remove all of them.

 

Hardened sulphate crystals can take hours and hours and hours to remove and even then might not all go.

 

The only way to avoid hardened sulphate is to fully charge daily. This is of course impractical for many boaters which is why their batteries don't last 10 years. Sadly that's just a fact of life.

[WotEver]

 

 

Last night I tried a 30.3V 'finishing off' charge using the little current pump PCB. I dared not raise the voltage any higher as the batteries were fizzing audibly (still with the caps on!) and even tiny rises in the voltage made them even noisier. Was I being too timid?

Difficult to judge whether or not you were being too timid but I can guarantee that you didn't do it for long enough.

 

I've said before to you that even the 12 hours from 8 to 8 on a Sunday probably isn't long enough.

At the dawn of my career I looked attfter new very old telecommunications installation, which used two batteries on a "one in use for a week", "one recharged during the week ready our use the next" and they didn't suffer, but were equalised every month.

And that bit is the secret. You must get rid of those crystals before they grow too hard to ever be removed.

[mross]

MtB, so does your alternator charge the starter battery? Do you have a split charge or a B2B for domestics?

[WotEver]

 

But these are two different things to my mind. "Leaving batteries discharged for a week" seems different from "discharging continuously from 100% to 50% over a week long period".

It's incremental for sure. The further you discharge the battery the more crystals will form. However during this time the first crystals to form will be getting larger and harder. See what I wrote a couple of posts back.

[Gareth E]

I'm wondering if I've wrecked mine as well, here's the story:

 

Fitted battery 1st November. Voltage without load has never been below 12.4. One day I charge for an hour and a half which results in a tail current of around 2.5a. The following day I charge until the tail current is 1.6a. This is the lowest tail current I've been able to achieve. Running the genny for a further 45 minutes doesn't lower this. How long this takes depends on how much solar has gone in and also how windy it's been, as I have a wind turbine. It usually takes between 2 and 3 hours.

 

So that's it, one day probably 90 odd percent soc, the next day 100% or thereabouts, as far as I know.

 

Because of the low temperature the effective voltage has been less than the 14.8 the charger was set at. Possibly as low as 13.8.

 

What do you reckon?

 

p.s. single 12v 105ah Trojan.

[WotEver]

I reckon you need to equalise at around 15.5V for at least two hours. Top up both before and after.

[cuthound]

What domestic alternator!

 

I have one 40A 24V alternator driven by the Kelvin vintage engine...

 

 

Last night I tried a 30.3V 'finishing off' charge using the little current pump PCB. I dared not raise the voltage any higher as the batteries were fizzing audibly (still with the caps on!) and even tiny rises in the voltage made them even noisier. Was I being too timid?

Yes, at equalising voltages the cells will gas freely and to desulphate them you will need to keep the voltage raised for several hours. Keep an eye on the battery temperatures though, if they get too hot apparently they can (although I have never witnessed it) go into thermal runaway.

 

I would keep them at a high voltage for three hours, then take temperature corrected specific gravity readings.

[cuthound]

Okay, here's what happens to lead acid batteries which will hopefully answer some of the confusion in a few of the previous posts...

When you discharge a battery, even just a little bit, sulphate crystals will form on the surface of the plates. These crystals will then steadily grow and harden hour by hour, day by day. If you played with a chemistry set as a kid you might have gown an Alum crystal - it's much the same.

If, like Mike, you leave it a week prior to fully charging the batteries then it's apparent from his experience that some of those crystals have now hardened (it's the hardness as opposed to the size that's relevant here although the two are obviously related) to such an extent that he doesn't have the time to charge for long enough on a Sunday to remove all of them.

Hardened sulphate crystals can take hours and hours and hours to remove and even then might not all go.

The only way to avoid hardened sulphate is to fully charge daily. This is of course impractical for many boaters which is why their batteries don't last 10 years. Sadly that's just a fact of life.

The sulphate crystals definitely grow as well as harden.

 

When I started work at the then Post Office Telecommunications, they had folders and folders of "Engineering Instructions (EI's) which were later updated to "Telecommunications Instructions" (TI's).

 

These covered every aspect of theory, practice and maintenence of all equipment used from boilers to batteries. There were photographs of healthy and sulphated battery plates as seen under a microscope, and you could clearly see the crystals were larger the longer the battery had been left in a sulphated state.

[WotEver]

The sulphate crystals definitely grow as well as harden.

 

When I started work at the then Post Office Telecommunications, they had folders and folders of "Engineering Instructions (EI's) which were later updated to "Telecommunications Instructions" (TI's).

 

These covered every aspect of theory, practice and maintenence of all equipment used from boilers to batteries. There were photographs of healthy and sulphated battery plates as seen under a microscope, and you could clearly see the crystals were larger the longer the battery had been left in a sulphated state.

Yes indeed, as I said in my post. However it's worthy of note that a new (therefore not hardened) crystal will be easy to remove. It is the hardened crystals that are truly obstinate. Generally these are also the largest.

[ditchcrawler]

I don't think Mike has a battery killing regime, he just needs to charge them enough to recover the the lead sulphate, which he can only do by charging at around 32 volts for at while AFTER the tail current has remained constant for around 30-45 minutes.

 

At the dawn of my career I looked after a very old telecommunications installation, which used two batteries on a "one in use for a week", "one recharged during the week ready for use the next" and they didn't suffer, but they were equalised every month.

 

Edited for spillung (twice)

That is how we ran our foghorn batteries

[dmr]

Mike, have you considered a bench power supply? I have a £40 unit but it's only suitable for 12V systems. I plan to use it to equalise my Trojans. You could set a voltage AND limit the current at the same time. Obviously, it would supplement your normal battery charger.

 

I thought seriously about this a while ago, its a nice idea but I rejected it, it might just work for Mike though.

For me there are three problems.

>Its yet another box of doings that I would have to find space for and space is precious.

>Even If I wait till 3% tail current to start equalising that's still 20 amps for me (660Ah of Trojans) and ideally I would like to start a bit sooner. A bench psu that can do 20+ amps at 15.5 volts is not an easy or cheap thing to get (forum input welcome here).

I only have mains when the engine is running (the mighty TravelPower) so the psu would have to work alongside the alternators. I know that some bench psu's do not like this. If the output voltage is accidentally set lower than the battery voltage the internal smoke can escape big time.

 

If anybody can point me towards a smallish affordable psu than does 30 amps at 15.5v and can charge batteries then I'll get one.

 

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

Yes, at equalising voltages the cells will gas freely and to desulphate them you will need to keep the voltage raised for several hours. Keep an eye on the battery temperatures though, if they get too hot apparently they can (although I have never witnessed it) go into thermal runaway.

 

I would keep them at a high voltage for three hours, then take temperature corrected specific gravity readings.

 

Just for info, its common to see the terms "Gass Freely" and even "Fizz" when talking about equalisation. What we would actually see if we took the cap off is a few very small bubbles gently rising to the surface and maybe 3 or 4 getting to the surface every second, its not very dramatic and in my experience a couple of hours does not use much water.

 

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

[dmr]

 

 

Thanks for the suggestion, no I hadn't!

 

I'm not entirely sure though as the elapsed time necessary to fully charge my batteries seems to run into the tens of hours per week. This is simply impractical and I'm now wondering if I should change my policy to buying a new set each spring (which will be looked after by the solar), then just allowing them to get trashed over the three winter months when I have the least time available for charging and they need the most time spent charging.

 

However, there is new information to add to the mix. I'm getting a Whispergen to play with! So that will change EVERYTHING...

 

New batteries every spring is a reasonable strategy for liveaboards, though some here would say you should then use cheapo leisures rather than Trojanoids *.

 

However I bet just before you throw your batteries away you would think "I wonder if I could recover them with a single long hard equalisation" and the answer just might be yes, especially if its only three months.

 

* my new name for the increasing number of lower cost batteries that look like Trojans but probably aren't. See Listeroid.

 

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

[Gareth E]

I have another question. I've dug out the temperature sender for my Sterling Pro Charge Plus. I didn't fit it because it would have meant drilling another hole through the bulkhead. The instructions say to attach the ring terminal on the end of the sender to a negative on one of the batteries.

 

I was thinking of attaching the ring terminal to the hull, in the cabin bilge. This is easily accessible, I could do this without drilling any further holes. The temperature here should be fairly close to the temperature the battery sits at. I've hesitated because a ring terminal suggests electricity! Would I be right in thinking that if I carry this out, while it's not ideal, can't do any harm, it's only a sensor for temperature?

[WotEver]

What would worry me about that is that the hull wouldn't track the battery temp and if the batteries warmed up during the charge for instance the sensor wouldn't detect it - that's why it's supposed to be physically (not electrically) connected to the battery.

[MtB]

But if you set Custom to 30.2v, what voltage do you actually get with a cold temperature probe? Is 30.2 the absolute maximum output voltage, or is it the nominal voltage at 25C in which case at 5C you could expect another volt or so.

 

 

Ok just done this. Custom charge voltage and float voltage both set to maximum setting of 30.2V.

 

The temperature in the back cabin (where the batteries are) is 8C according to the Met Office The charger is running and batteries are approaching fully charged. The charger is now displaying a charge voltage of 30.7V and the BMV-702 is measuring it as 30.61V. So know we know temperature compensation raises the voltage higher than the settings entered if necessary.

 

Tail current is down to 4.25A now and still falling very slowly. Was 4.9A an hour ago. About 2%. I think I'll start the desulphation cycle again shortly or is there any benefit in waiting for the tail current to fall further?

Edited January 9, 2017 by Mike the Boilerman

[WotEver]

I'd say that although 2% is still a bit high for newish batteries you've got to be practical about this. You could charge all day and still only be down to 1.5%. Therefore I'd say yes, go for an equalisation charge for 3 hours.

[nb Innisfree]

Back several years ago I used to bulk charge our AGMs daily with the engine alternator and a monthly 8r raised absorption with a Kipor and Victron Multiples. After their near death I experimented and eventually settled on a weekly 8hr absorption (29.2v) on top of the usual daily bulk charge to 80% (ish). Combined with 3 or 4 long charges of a few days on a hookup the batts made a full recover after a few months.

 

ETA: the long hookup charges took the charge rate down to, on one occasion, 0.2 amps (8x120ah batts)

Edited January 9, 2017 by nb Innisfree

[Wrinkley]

Just want to say I am reading this thread with great interest. Just waiting for my refracometer to arrive then watch me go!

 

Graham

[WotEver]

ETA: the long hookup charges took the charge rate down to, on one occasion, 0.2 amps (8x120ah batts)

Yes, Nick has observed on here that he regularly gets down to 0.25% C, so it's certainly possible with a long enough charge. Nobody believes how many hours that can take though, and that's the biggest problem with educating folk about charging. How many times have we read "I charge them for at least 2 hours every day"?

[MtB]

 

 

Ok just done this. Custom charge voltage and float voltage both set to maximum setting of 30.2V.

 

The temperature in the back cabin (where the batteries are) is 8C according to the Met Office The charger is running and batteries are approaching fully charged. The charger is now displaying a charge voltage of 30.7V and the BMV-702 is measuring it as 30.61V. So know we know temperature compensation raises the voltage higher than the settings entered if necessary.

 

Tail current is down to 4.25A now and still falling very slowly. Was 4.9A an hour ago. About 2%. I think I'll start the desulphation cycle again shortly or is there any benefit in waiting for the tail current to fall further?

 

 

Now here's a curious thing. The de-sulphation cycle runs for three hours then reverts to float according to my Sterling Pro Charge Ultra manual.

 

I started the desulphation cycle running at 12 midday exactly and now, at 3.35pm, more than three and a half hours later it is still in de-sulphation mode. Why hasn't it turned OFF and reverted to float? Could the length of the cycle have been increased as temperature compensation perhaps?

 

Its desulphating at a rock solid 31.35V. The starting current was 6.28A and the current now after 3.5 hrs is 4.60A. All cells bubbling steadily.

[nicknorman]

If you monitor the specific gravity during the desulphation process, you will hopefully see it rising slowly. It is time to stop the desulphation process when the gravities no longer increase.

[nb Innisfree]

Yes, Nick has observed on here that he regularly gets down to 0.25% C, so it's certainly possible with a long enough charge. Nobody believes how many hours that can take though, and that's the biggest problem with educating folk about charging. How many times have we read "I charge them for at least 2 hours every day"?

And the answer to how long depends on all sorts of variable factors, the time for our batteries to reach max charge varied from 24hrs to 3+ days, not achievable when off grid so it has to accepted that batteries will always be treated less than ideally.