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equalization charge


Tommo

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Whilst we are talking chargers what is the consensus regarding equalizing?

I only have 3 stage charging systems and can’t get to the required voltage of 15.5V (recommended by battery manufacturer). Is there anything out there I can use just for equalizing and what current would I need. Battery bank is 675Ah using 6 x 6 Volt.

Thanks

 

Ian

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Whilst we are talking chargers what is the consensus regarding equalizing?

I only have 3 stage charging systems and can’t get to the required voltage of 15.5V (recommended by battery manufacturer). Is there anything out there I can use just for equalizing and what current would I need. Battery bank is 675Ah using 6 x 6 Volt.

Equalising is important for bank long term health in situations where there are a lot of batteries and they may be discharged/charged at different rates. This is particularly relevant with 24V systems or where 12V systems use 6V batteries, but is probably a waste of time if you have not taken the trouble to ensure all the connecting leads are the same length and of the same size.

The idea is to make sure that all the batteries in the same bank are charged to the same state, so if they are deep cycled, all the batteries suffer the same degredation!

If you already have 3 stage charging then the 3rd stage should be equalisation, but the time it takes to reach the equalisation voltage is very short in a healthy system, so with a standard voltmeter you may not see that attained, as as soon as the 3rd stage shuts down the voltage drops back to float (~13.5V).

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I thought:

 

float and equalisation were two different things.

 

three stage charging was bulk, absorption and float.

They are!

You would have to look at the specs. for the particular charging system, some ignore the 'float' bit and others include it, so you can see four stage chargers mentioned, not all include three stage ones include equalisation!

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The only time you would't need it is if you have some form of charge balancing system fitted to the battery bank. It's common on big battery banks using lithium batteries (read hybrid vehicles) and consists of circuitry that brings each cell to the same level of charge. The simpler ones do it by bleeding power off cells till they're all at the level of the lowest, the more sophisticated ones can move charge from the more fully charged ones to the less well charged ones.

 

With the type of batteries used on boats you have to use an equalisation charge.

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Float charge will, if kept going for long enough, equalise all cells. Normal equalisation isn't something special, it's just a long enough charge to allow the lowest cell to catch up, and reach 100% SoC, speeded up if required by increasing the voltage, a bit like in a race each runner reaching the finishing line and staying there running on the spot until all the other runners including the last straggler reaches the line.

 

Then the race starts again :)

 

ETA: just read Chalky's post which deals with equalisation in a different more sophisticated way.

Edited by nb Innisfree
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Equalising is important for bank long term health in situations where there are a lot of batteries and they may be discharged/charged at different rates. This is particularly relevant with 24V systems or where 12V systems use 6V batteries, but is probably a waste of time if you have not taken the trouble to ensure all the connecting leads are the same length and of the same size.

The idea is to make sure that all the batteries in the same bank are charged to the same state, so if they are deep cycled, all the batteries suffer the same degredation!

If you already have 3 stage charging then the 3rd stage should be equalisation, but the time it takes to reach the equalisation voltage is very short in a healthy system, so with a standard voltmeter you may not see that attained, as as soon as the 3rd stage shuts down the voltage drops back to float (~13.5V).

Thanks Robin

 

Sorry but I don’t quite understand that, my 3-stage charge is Bulk, Absorption, Float at 14.25 and 13.5 Volts respectively, (Mastervolt 12/2500/100 Combi with CSCP) I cannot alter the bulk/absorption voltage but I can vary the float slightly. When I charge via the alternator (Mastervolt 120 amp 3-stage) I have more control over the voltage and bulk/absorption is set to 14.5V at 20 degrees. I can even push the voltage to just above 15V but it is a bit of a fiddle to keep adjusting it. And by the way, nothing wrong with my cables.

 

Regarding an equalization charge, I was under the impression it could help remove sulfate crystals that might have built up on the plates. And as you point out with 6V batteries it is probably a good idea.

 

So the general consensus seems to be that yes it is a good idea. Next question is, can I get a charger just for equalization and if so what current is required?

 

Ian

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So the general consensus seems to be that yes it is a good idea. Next question is, can I get a charger just for equalization and if so what current is required?

Not sure that you can get a unit that just equalises?

It is important that it is done after the batteries are charged, so normally as the charge goes into float. The current is not terribly important and should be around a tenth or twentieth of the bank capacity, or course the actual equalisation voltage also depends on the battery type and is usually between 14.8 and 15.5V.

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Whilst we are talking chargers what is the consensus regarding equalizing?

I only have 3 stage charging systems and can’t get to the required voltage of 15.5V (recommended by battery manufacturer). Is there anything out there I can use just for equalizing and what current would I need. Battery bank is 675Ah using 6 x 6 Volt.

Thanks

 

Ian

 

 

I am going to stick my neck out here and say (based on something Gibbo wrote rather a long time ago) that unless you are using a shoreline based charger you do not need to equalise.

 

To be more controversial equalisation has nothing to do with reducing sulphation although it must help in that respect. It is to do with "stirring the acid up" to get rid of stratification and possibly forcing any less charged cells to become closer to fully charged.

 

I would have thought that an ex.MOD bench type power supply with variable volatge might do one battery at a time after it had been well charged by the ordinary system. Set the volts to 15.5 or whatever and if too much current is flowing hopefully the internal circuits will protect the power supply. However you would have to check temperature, Sp. G. & keep the cells topped up. I seem to remember Gibbo was not so keen on automatic equalisation anyway.

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I am going to stick my neck out here and say (based on something Gibbo wrote rather a long time ago) that unless you are using a shoreline based charger you do not need to equalise.

 

To be more controversial equalisation has nothing to do with reducing sulphation although it must help in that respect. It is to do with "stirring the acid up" to get rid of stratification and possibly forcing any less charged cells to become closer to fully charged.

 

I would have thought that an ex.MOD bench type power supply with variable volatge might do one battery at a time after it had been well charged by the ordinary system. Set the volts to 15.5 or whatever and if too much current is flowing hopefully the internal circuits will protect the power supply. However you would have to check temperature, Sp. G. & keep the cells topped up. I seem to remember Gibbo was not so keen on automatic equalisation anyway.

My charger has an equalisation function, only works on wet cells. It sets the current to a fixed 4.2 amps and then increases the voltage. I have all the lesiure batteries at home in the garage at the moment, during the cold weather when I was charging and equalising them the voltage was in the order of 16.5V and the acid was certainly being stirred up.

 

Ken

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To stir electrolyte up you can if you want do that with a hydrometer instead of using a higher voltage, just squeeze electrolyte in and out of the tester a few times. We have AGMs so can't use this method and being off grid and using partial state of charging we do a long 8 hour+ raised absorption/equalisation charge once a week or so just to make sure batts reach 100% SoC and hopefully all cells are equalised.

Edited by nb Innisfree
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Equalisation was originially "thought up" in order to equalise the charge between cells in series. It does this by simply overcharging them all. The ones that come up to charge first lose water (that's where the energy goes), the others slowly catch up. That was the intial idea and that was its main purpose.

 

As an aside it also stirs everything up and reduces stratification. Stratification can damage the cells because it concentrates the acid at the bottom of the cells and corrodes the grid. Stratification is really only a problem on batteries that never move and are left with no charge or left on float for long periods. Many modern "smart" chargers go into a quick bulk/acceptance every X number of days which massively reduces this as it gives the electrolyte a bit of a gas (and hence a stir) once in a while.

 

A final benefit of equalisation is that it reduces and/or helps reverse sulfation. This was not it's initial intent, however it's probably it's main use in many installations today because sulfation itself is much more of a problem than the others. Individual cells going out of balance is less of a problem because batteries themselves are simply better balanced today than they were 100 years ago. Stratification shouldn't be a problem if the boat is used (ie it moves) or with a modern smart charger.

 

This is all assuming the charger and alternator are actually charging at the correct voltage. If they're not, then equalisation is a must in order to avoid very rapid sulfation.

 

All, of course, just MHO.

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Whilst we are talking chargers what is the consensus regarding equalizing?

I only have 3 stage charging systems and can’t get to the required voltage of 15.5V (recommended by battery manufacturer). Is there anything out there I can use just for equalizing and what current would I need. Battery bank is 675Ah using 6 x 6 Volt.

 

If they're flooded non sealed batts, see the suggestion in this post. Another way could be an unregulated solar panel, especially if you're without a shoreline.

 

Again if they're flooded non sealed batts, if you can split the bank and do part at a time then a low cost DC to DC laptop charger with some current limiting might do.

 

I'd expect the current should be enough to make them gas a bit without pushing the charge voltage much above 15.5V in your case. Try starting off with C/40 to C/50 where C is the bank/battery size.

 

Do follow all precautions regarding battery charging and gassing, see The Battery FAQ and this section for more details.

 

cheers,

Pete.

Edited by smileypete
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My charger has an equalisation function, only works on wet cells. It sets the current to a fixed 4.2 amps and then increases the voltage. I have all the lesiure batteries at home in the garage at the moment, during the cold weather when I was charging and equalising them the voltage was in the order of 16.5V and the acid was certainly being stirred up.

 

Ken

Payne (p.9) says "a higher voltage level at a current rate of 5% of the battery capacity...."

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I am going to stick my neck out here and say (based on something Gibbo wrote rather a long time ago) that unless you are using a shoreline based charger you do not need to equalise.

 

I would have thought that an ex.MOD bench type power supply with variable volatge might do one battery at a time after it had been well charged by the ordinary system. Set the volts to 15.5 or whatever and if too much current is flowing hopefully the internal circuits will protect the power supply. However you would have to check temperature, Sp. G. & keep the cells topped up. I seem to remember Gibbo was not so keen on automatic equalisation anyway.

Thanks for all the replies,

 

Tony, I forgot that I had a old switch mode 25amp bench power supply in my workshop, do you think it may do the job. It does just about get to 15.5V

power-supply.jpg

Yes, I am using flooded cells, 6 x 6 Volt 225Ah I installed them about nine months ago (to replace 3 new 220 Elecsols which just did not work for me) and so far they seem to be very good.

Edited by Tommo
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Thanks for all the replies,

 

Tony, I forgot that I had a old switch mode 25amp bench power supply in my workshop, do you think it may do the job. It does just about get to 15.5V

power-supply.jpg

Yes, I am using flooded cells, 6 x 6 Volt 225Ah I installed them about nine months ago (to replace 3 new 220 Elecsols which just did not work for me) and so far they seem to be very good.

 

 

Not sure why the section above 13.8V is in red, but if we assume it is rated up to 16 volts continuous and you start with a single fully charged battery then I do not see why not. (fully charged so the current rating is not exceeded).

 

As you will only be doing one 6v battery at a time The voltage should be plenty but whether 225 Ah would allow too much current draw at equalistaion volatge is open to question.

 

I would say suck it and see, the power supply should (I hope) protect itself from excess current flow.

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I am going to stick my neck out here and say (based on something Gibbo wrote rather a long time ago) that unless you are using a shoreline based charger you do not need to equalise.

 

To be more controversial equalisation has nothing to do with reducing sulphation although it must help in that respect. It is to do with "stirring the acid up" to get rid of stratification and possibly forcing any less charged cells to become closer to fully charged.

 

I would have thought that an ex.MOD bench type power supply with variable volatge might do one battery at a time after it had been well charged by the ordinary system. Set the volts to 15.5 or whatever and if too much current is flowing hopefully the internal circuits will protect the power supply. However you would have to check temperature, Sp. G. & keep the cells topped up. I seem to remember Gibbo was not so keen on automatic equalisation anyway.

 

Hi Tony,

 

We'll I'm here ! Vida~Nueva is fitted with a 'Power Master' battery charger. The instructions that come with it make interesting reading. It has an equalising charge of 14.6v and a floating charge of of 13.7 v

 

I have made the assumption that it is all automatic and as so far boat has not left the Mercia Marina very much, due to the ice, for most of the time it has been hooked up to the shoreline. Until very recently I did not connect the shoreline to the charger or anything else for that matter, as our surveyor wasn't totally happy with the way the Galvanic Isolator was wired. I think he was concerned that there was no bonding cable connected from the hull onto the boat side of the earth connection.

 

I had doubts about all this, so now I have a proper isolation transformer which as far as I can tell, is doing it's stuff.

 

I now feel more confident to leave the charger connected all the time(while still connected to the shoreline !)

 

I am aware that the charger is operating, because in the dead of night, I can hear the fan working, which soon stops after all the cabin lights(LED downlighters) are switched off; eventually it comes on again, I presume the fridge has cut in(the shorline fridge is lovely and quiet !)

 

Do you think it is desirable to leave the charger permanently switched on, as it is a fully automatic model ?

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Hi Tony,

 

We'll I'm here ! Vida~Nueva is fitted with a 'Power Master' battery charger. The instructions that come with it make interesting reading. It has an equalising charge of 14.6v and a floating charge of of 13.7 v

 

I have made the assumption that it is all automatic and as so far boat has not left the Mercia Marina very much, due to the ice, for most of the time it has been hooked up to the shoreline. Until very recently I did not connect the shoreline to the charger or anything else for that matter, as our surveyor wasn't totally happy with the way the Galvanic Isolator was wired. I think he was concerned that there was no bonding cable connected from the hull onto the boat side of the earth connection.

 

I had doubts about all this, so now I have a proper isolation transformer which as far as I can tell, is doing it's stuff.

 

I now feel more confident to leave the charger connected all the time(while still connected to the shoreline !)

 

I am aware that the charger is operating, because in the dead of night, I can hear the fan working, which soon stops after all the cabin lights(LED downlighters) are switched off; eventually it comes on again, I presume the fridge has cut in(the shorline fridge is lovely and quiet !)

 

Do you think it is desirable to leave the charger permanently switched on, as it is a fully automatic model ?

 

 

In my view it is preferable to leave the charger on BUT it is wise not to do so if you suspect damaged cells or you allow wet cells to become dry. With dry or damaged cells you might end up with an explosion.

 

Really you need Gibbo to give his opinion.

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