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Old 05-06-2013, 01:46   #1
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Battery Charging - Absorption Voltage - Calcium/Calcium Batteries

We have recently replaced our domestic bank of batteries. We now have 4 X 105 Ah Varta LFS105. These are Calcium/Calcium maintenance-free. The battery charging is either shore power/generator through a Victron Multi 12/2500/120 inverter/charger, or a 75 amp alternator controlled by a Balmar MaxCharge 614 controller. At the moment, the absorption voltage on both systems is set to 14.4 Volts. Both charging systems have temperature sensors and voltage sensors at the batteries for temperature and voltage compensation to limit gassing. Recent research on the internet indicates that Calcium/Calcium batteries can be charged at a significantly higher absorption voltage than Lead/Antimony batteries, whose maximum is 14.4 Volts. Queries to battery dealerships and equipment suppliers have produced advice that Calcium/Calcium batteries should indeed be charged at higher voltage than 14.4 Volts, but the advice has varied from a low of 14.7 Volts to a high of 16.0 Volts.

Indeed, as Lead/Antimony batteries have now been almost completely removed from the market to be replaced by Calcium/Calcium batteries, it is perhaps timely for most boat owners to be questioning whether the advice they have been given concerning charging voltages is still extant; persistent under-charging causes premature battery failure just as much as over-charging.

Of course there is the possibility that, because most charge controllers are set to a maximum of 14.4 Volts, battery manufacturers / distributors / salesmen are reluctant to advertize the use of higher charging voltages because then most boat owners would have to go out and buy new charge controllers.

I would like to point out that I am following the convention whereby the term "Calcium/Calcium" refers to batteries which have Calcium re-enforcement in both grids, rather than Lead/Calcium where one grid has calcium and the other could be Antimony, Selenium or even Silver.

Despite considerable research, I have been unable to find a single authoritative source on the subject. Should anyone have definitive information on the subject, I would be grateful for details of the source.

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Old 05-06-2013, 02:22   #2
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Re: Battery Charging - Absorption Voltage - Calcium/Calcium Batteries

Well, I think you should charge your batteries at the voltage specified by the battery manufacturer. There is no fixed rule as there are so many variations and manufacturers.

Not more than 14.8 volts though as otherwise you run the risk of damaging some of your 12v devices that maybe are not designed to handle voltages much above this.

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Old 05-06-2013, 04:22   #3
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Re: Battery Charging - Absorption Voltage - Calcium/Calcium Batteries

As Fuss points out, it may boil down to a practical decision re: the highest charging voltage that your other onboard electronics will be happy with.

The issue is not new; calcium/calcium batteries have been around a very long time, as have the other formulations for grids. Each formulation brings with it both advantages and disadvantages. For example, the calcium/calcium batteries with very low gassing and water loss potential bring with them increased susceptibility to electrolyte stratification and plate corrosion.

The European approach has differed markedly from the U.S. approach. A good article which tries to trace these and other differences between the various technologies can be found here:

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Old 05-06-2013, 04:39   #4
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Re: Battery Charging - Absorption Voltage - Calcium/Calcium Batteries

Very interesting paper btrayfors
We have lead calcium batteries, 12 x 105Ah wired in 24V configuration and the absorption voltage from the charger is 28.8V...same as standard FLA batts.
16V is used as an equalizing voltage to dump deposits off the plates on FLA batts.
16V will drive your batts to gassing and if you charge at that rate they will die no doubt.
Seems to me batt manufacturers have varying opinions on how to charge even the same construction some AGM makers say equalize, others say Don't do it ! but the batteries are essentially the same....
Calcium batts are still feeling would be to stick with standard voltages unless the batt maker says 14.4 absorb, 13.4 float....
I doubt that much would be gained by raising the absorption V to 14.8 say over 14.4...If you have a big bank and its down to 70% or so, you may kill the engine before you get to float anyway ....
Interesting subject !!
See you out there ....... Alan S.V. Elyse
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