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Old 29-12-2011, 13:14   #1
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Charging Voltage Question

Good Day All,

First of all thanks to all who have previously posted in the electrical forum, searching for an answer to my question has been enlightening (even for a retired engineer).

I have recently acquired a used ARS-5 regulator and when charging in the initial "Bulk" phase I am getting voltages of 14.8-14.9 (measured by Link 10, analog meter, and a multimeter at the regulator's contacts). Admittedly the batteries (4 Trojan 105s) are fully charged from shore power (off while testing). Trojan shows a 14.8v spec for charging on their site, so I'm not really worried about them.

My concern, having read comments alluding to "bulk charge is full field" and tuning/dialing in smart regulators is required due to mfrs. dumbing down their default settings. The ARS-5 brochure shows a 14.6v default bulk setting for FLA batteries, while the voltage is programmable, I am not sure I should or would want to lower it as it would extend charging times.

Is 14.9 volts dangerous for marine electronics or a Danfloss compressor
(I could not find a maximum operating voltage on their site)?

Some facts;
I have replaced the 16ga. harness from my BRS II with the 14ga. for the ARS and all connections are good.

I have a 75A Balmar alternator, so I am not worried about thermal runaway/over charging (acceptance rates/ Batt temp sensor should handle any issues).

I have not yet run it long enough to assess what happens when it transitions to the absorption phase.

The readings are identical w/wo Bat/Alt temperature sensors.

I am not interested in Mr Sterling's theories.

Thanks,
Ed
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Old 29-12-2011, 15:50   #2
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Re: Charging Voltage Question

Before I switched to LiFePo4 batteries, I had FLA's.
Once a month, the MPPT controller would automatically go to the Equalize mode, running the batteries slowly up to 16.5 volts.
It never hurt the fridge or anything else I ran including the inverter.
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Old 29-12-2011, 19:36   #3
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Re: Charging Voltage Question

14.9 is a bit high - the batteries will need watering a lot more often I think. I would dial it back to 14.6 volts.
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Old 29-12-2011, 19:53   #4
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Re: Charging Voltage Question

What does the regulator display show for

Battery program type
Battery Voltage
Calculated Voltage
Percentage of field output.
Battery temperature
Voltage compensation for battery temperature?

At the same time, record what you measure for battery voltage and temperature.
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Old 30-12-2011, 19:44   #5
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The definitive answer to charging voltage

Long term float voltage is the only important voltage for any lead-acid battery, AGM or gel included.

Because you have a Link 10 you should observe the number of Amp-hours "missing" from your deeply discharged battery and as long as the number of charging Amps does not radically exceed the scalar number of "Amp-hours" missing you will not excessively gass or experience an intolerable temperature rise. It, therefore, becomes merely "interesting" to observe the voltage that gives you that number of charging Amps.

Yes, it may be important to not have any "12V" load that might over heat at voltages close to 15V yet not many loads do. Even incandescent bulbs do not radically shorten their lives as long as they are on already when you begin the charging regimen (or turn them off).

With this information keep in mind that for short periods the above number of Amps described MAY be exceeded as long as the battery is designed to carry heavy loads.
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Old 31-12-2011, 08:15   #6
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Quote:
Originally Posted by Rick
Long term float voltage is the only important voltage for any lead-acid battery, AGM or gel included.

Because you have a Link 10 you should observe the number of Amp-hours "missing" from your deeply discharged battery and as long as the number of charging Amps does not radically exceed the scalar number of "Amp-hours" missing you will not excessively gass or experience an intolerable temperature rise. It, therefore, becomes merely "interesting" to observe the voltage that gives you that number of charging Amps.

Yes, it may be important to not have any "12V" load that might over heat at voltages close to 15V yet not many loads do. Even incandescent bulbs do not radically shorten their lives as long as they are on already when you begin the charging regimen (or turn them off).

With this information keep in mind that for short periods the above number of Amps described MAY be exceeded as long as the battery is designed to carry heavy loads.
This isn't correct , firstly in a dynamic system, battery usage , discharge and charging intermingled , float voltages are meaningless.

Despite what you say, the absorption does indeed matter, firstly it should be temperature compensated, too high a value and significant out gassing can result. You need to look at manufacturers specs for absorption voltage. But typically 14.4 to 14.6 is typical , temperature compensated.

Dave
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Old 01-01-2012, 16:03   #7
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Re: Charging Voltage Question

Please understand the history of three-step charging regimens: They were developed as a "first approximation" of Amp-hour-law charging with limitations because no one had an economical method of implementing a charger/battery monitor that could do the real thing. As such, temperature compensation of absorption voltage was more important without the ability to monitor the battery state-of-capacity.

With 100% recovery of any lead-acid battery it IS important to use a regulated float voltage to enhance the life of the battery. Too small a voltage does not necessarily keep ahead of self-discharge, too much causes unnecessary gassing and heat. Cruisers who live continually on charge/discharge cycles do not have the luxury of having a 100% recovered battery and, therefore, float voltage is less important to them. Otherwise, long term float voltage must be applied (yes, with temperature compensation) to maximize the lifetime of the battery.

This information is not merely theoretical and was develped around 1930. Unless the battery is charging near thermal runaway temperatures (120deg F) Amp-hour law charging without temperature compensation is sucessful because the heat capacity of the battery compensates for any danger of excessive temperature rise WHEN using an Amp-hour-law charging regimen. By the time the battery temp should begin to rise significantly the unit is "full" and temperature compensated float voltage prevents any destructive current from flowing.

Please do not challenge this concept until you investigate the veracity of my claims.
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Old 01-01-2012, 16:15   #8
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Absorption voltage

With Amp-hour-law charging there never IS an absorption voltage. The voltage changes as the curve of Epsilon while the current does as well. When the capacity lost has been replaced the charger applies a regulated float voltage. That is why ONLY float voltage is important.

The original question (and my answer) is how a user with a good battery monitor and the ability to change the voltage of a charge source can best (and quickly) charge a battery. It turns out that because the charge acceptance of any lead-acid battery follows a curve of Epsilon inverse to the state of capacity as it charges using an elivated charge voltage(s) one can use the monitor to verify safe areas of charging operation. At temperatures well below thermal runaway of a battery the Amp-hour-law limitations may be radically exceeded with relative safety. One example of this is how some racing electric vehicles recharge in one hour or so. Amp-hour law charging requires 3.5 to 4 hours from empty to full.
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Old 01-01-2012, 16:22   #9
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Re: Charging Voltage Question

Right on Rick!
And most commercial gauges are only accurate within +/- 5%, maybe more, unless calibrated by a certified instrument repair facility.
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