rupertshearer avatar image
rupertshearer asked

Correct MPPT charge controller to remove sulfation from lead acid battery?

Hello, I work for a solar company and have access to a wide range of Victron MPPT charge controllers. I am trying to remove heavy sulfation off 2 6V Rolls deep cycle lead acid batteries connected in series, by first allowing them to bulk charge, and then setting the current very low, around 0.5A, and keeping the voltage at around 15.5V for a week or two. Is there any Victron controller which can maintain this current and voltage for a long period of time? Thanks

battery charging
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2 Answers
wkirby avatar image
wkirby answered ·

You can set absorb and float to 15.5V to mainatain that Voltage. Then set a current limit, I think the resolution of the current limit setting is an integer, so minimum 1A.

Consider Ohms law when doing this though, a current limit set to low may never get the battery to reach 15.5V at all, so you might need to raise the current limit if find that you don't achieve your target Voltage.

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Alistair Warburton avatar image
Alistair Warburton answered ·

Sulfation is, by definition, insoluble sulphate crystals built up on the plates where there would have been soluble ones if everything was working as it should.

There is much debate as to weather this condition is reversible and I suspect, just my opinion, that as the effect is cumilative and time dependent that some of the crystals will be soluable, given sufficiant voltage, but most could only be removed mechanically.

As far as I know, chemically, sulfation cant be reversed and is cause primerrally by systemically under charging, in the ay that most off grid generator based systems and many solar systems will do.

Have look at betery university... Just google it.

Some folk have claimed that high frequency pulses can dislodge crystals and that a subsiquant electrolite change can fix a bad battery... I cant comment.

I can tell you that a plate with reduced surface area because it is partly covered with useless insulating crystals will reduce available current & capacity whilst increesing internal resistance.

'Heavily' sulfated batteries are likely worth more as scrap than anything else.

Relitivly high voltage may help, in which case MPPT is irrelavent.

MPPT on its own will have no effect as it is a system management strategy to maximise solar output as opposed to managing or modifying a battery.

Remenmber that lead acid chmestry CAN NOT be fast charded no matter how much energy you have or what size the battery is.

You can ram a huge amount of energy in quickly during bulk but without a sutibly long absorbe phase where well under 20% of the total capacity is absorbed you will have an under charged cell that will quickly suffer...

Sorry this isnt a positive comment, but it is realistic.


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