SternWake
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Charging a battery can be mysterious, especially when one does not have an Ammeter or an ability to apply a known current to a battery. Bulk, Absorption, float, equalizing, these terms have been maligned by marketers of charging equipment and have warped the minds of those who read them more than once.
Mainsail takes a used lifeline gpl-31t AGM (105AH) battery, fully charges it, equalizes it, and then loads it at the 20 hour rate at 77f and posts voltage readings at various states of charge.
His next writeup he charges it at different rates, and while double the charge current initially only reduce time to full by a meager 12 minutes, the doubled charge current got the battery to 96% in 2 hours.
Anyway, he says it all better than I can, and it might help others, and take some mystery out of lead acid battery charging, specifically in this case, on a high$$ AGM that has lost~10% of its total capacity before the test.
http://www.pbase.com/mainecruising/voltage_vs_soc_lifline_battery
http://www.pbase.com/mainecruising/effect_of_charge_rate_on_agm_battery
If one wants a quick summary of results, moral. When Aiming for a 50% discharge and no more by reading voltage alone. Most people are going well below 50%
When recharging a high$$ AGM, more charging current is mo Better, but it still takes a long time to go from 95% to 100%, but 50% to 96% can be done in 2 hours at a 40% charge rate. 96 to 100% takes 3.5 more hours
At a 20% charge rate 50% to 87% can be done in 2 hours, and 87% to 100% takes approximately 3.75 more hours.
The battery he tests is used and has lost ~10Ah of its 105Ah original capacity. The less healthy the battery the longer the charge times will be.
50% to 100% took a minimum of 5.5 hours. but 50 to 96% could be accomplished in 2 hours.
that last 4% takes 3.5 hours, and is incredibly important for achieving good cycle life of an AGM.
So is 92% to 95% SOC, that most automatic charging sources stop at, 'good enough?'
Certainly not.
Achieve absorption voltage, hold it as long as it takes, and it takes a minimum of 5.5 hours from 50% to 100% on a high$ high quality still relatively healthy AGM battery.
Real Data.
Facts.
No blinking, feel good, lying, green lights.
Hold absorption voltage until amps taper to 0.5% of capacity. 0.5 amps per 100Ah capacity. Can't measure amps? then hope and pray your batteries are getting full, but that is like trusting a politician. Unwise in the extreme.
Mainsail takes a used lifeline gpl-31t AGM (105AH) battery, fully charges it, equalizes it, and then loads it at the 20 hour rate at 77f and posts voltage readings at various states of charge.
His next writeup he charges it at different rates, and while double the charge current initially only reduce time to full by a meager 12 minutes, the doubled charge current got the battery to 96% in 2 hours.
Anyway, he says it all better than I can, and it might help others, and take some mystery out of lead acid battery charging, specifically in this case, on a high$$ AGM that has lost~10% of its total capacity before the test.
http://www.pbase.com/mainecruising/voltage_vs_soc_lifline_battery
http://www.pbase.com/mainecruising/effect_of_charge_rate_on_agm_battery
If one wants a quick summary of results, moral. When Aiming for a 50% discharge and no more by reading voltage alone. Most people are going well below 50%
When recharging a high$$ AGM, more charging current is mo Better, but it still takes a long time to go from 95% to 100%, but 50% to 96% can be done in 2 hours at a 40% charge rate. 96 to 100% takes 3.5 more hours
At a 20% charge rate 50% to 87% can be done in 2 hours, and 87% to 100% takes approximately 3.75 more hours.
The battery he tests is used and has lost ~10Ah of its 105Ah original capacity. The less healthy the battery the longer the charge times will be.
50% to 100% took a minimum of 5.5 hours. but 50 to 96% could be accomplished in 2 hours.
that last 4% takes 3.5 hours, and is incredibly important for achieving good cycle life of an AGM.
So is 92% to 95% SOC, that most automatic charging sources stop at, 'good enough?'
Certainly not.
Achieve absorption voltage, hold it as long as it takes, and it takes a minimum of 5.5 hours from 50% to 100% on a high$ high quality still relatively healthy AGM battery.
Real Data.
Facts.
No blinking, feel good, lying, green lights.
Hold absorption voltage until amps taper to 0.5% of capacity. 0.5 amps per 100Ah capacity. Can't measure amps? then hope and pray your batteries are getting full, but that is like trusting a politician. Unwise in the extreme.
