| Re: [GMCnet] Battery charging confusion [message #104972] |
Wed, 03 November 2010 18:08  |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Thanks Ken,
OTOH Handy Bob was pretty unequivocal that 14.8 for an hour or two before floating was the only way to get a battery 100.00% charged, & he quotes batt mfr specs to support that. Is he mistaken or just radically over-reacting?
J
76 PB
Portland, OR
--------------------------
> 14.8 is a little high. Normal charging is between 13.8 and 14.2. You can get by at 14.8 for a short while IF the battery is cold and depleated enough. If you do not know the state of charge on the battery and have no way to monitor the state while while charging, I would not go that high. There is really no advantage to going that high other than an initial quicker warm up and slightly quicker charge.
>
> You are going to have to drop back to a lower voltage (13.6-13.8) once the battery starts gassing or gets too warm. When it is fully charged you will need to drop every further to about 13.2 as a maintenance charge of about 13.2.
>
> Note: On a fully charged room temperature battery you can go to 14.4 for very brief periods like 15 minutes or so without hurting it.
>
> I would not go to 14.8 unless you are going to sit there and watch it while it charges.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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| Re: [GMCnet] Battery charging confusion [message #105013 is a reply to message #104972] |
Thu, 04 November 2010 01:27  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| jayrabe wrote on Wed, 03 November 2010 18:08 |
Thanks Ken,
OTOH Handy Bob was pretty unequivocal that 14.8 for an hour or two before floating was the only way to get a battery 100.00% charged, & he quotes batt mfr specs to support that. Is he mistaken or just radically over-reacting?
J
76 PB
Portland, OR
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14.8 will get you charged sooner, but not any more completely. I personally would not do it because of the risk of boiling and destroying the batteries.
Some expensive charge controllers have a temperature probe that sits in the battery to tell to the charger to down shift when things get too warm. Your final charge to finish off the battery will be around 13.8 no matter what the initial charge rate was.
Float or maintenance more is another thing and it is around 13.2 volts.
If Bob was correct then every car and truck running around would be under charged. Every automotive alternator system I know of runs 13.8 to 14.2. Most of those that run up to 14.2 sense the alternator temperature and throttle down to 13.8 when it get warm. This reduces the charge rate and tops off the battery without over charging it.
In another application I have several small battery packs that have thermistors implanted in them. The thermistors tell the matching smart charger when they are being over charged. Once the thermistor trips the charger throttles down and stays there until the pack is removed from the charger and is reconnected again. This arrangement allow much higher initial charging rates and shortens the normal slow 12 hour charge rate on a completely depleted battery to about 2.0 hours. It works.
If you had similar smart charging technology built into your battery and a smart charger to interpret it, then you could go to 14.8 or higher on your GMC batteries. Without it I suggest you stay in the 13.8 to 14.2 volt range and float them to 13.2 when they are fully charged.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Battery charging confusion [message #105029 is a reply to message #104972] |
Thu, 04 November 2010 08:00 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| jayrabe wrote on Wed, 03 November 2010 19:08 |
Thanks Ken,
OTOH Handy Bob was pretty unequivocal that 14.8 for an hour or two before floating was the only way to get a battery 100.00% charged, & he quotes batt mfr specs to support that. Is he mistaken or just radically over-reacting?
J
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J,
The 14.8V (~2.47/cell) is a left over from the thinking that a Lead/Acid (LA)battery is better off if the electrolyte is circulated during charging, and the heat was thought to be a good way to cause this. This also what I was taught about forty odd years ago.
What I have learned since is that most of the power that the extra 1/2V represents goes directly into heat in the cell. If this was all that important, AGM batteries would not be very good at very much.
There are also two important points you have to absorb when reading what Handy Bob wrote about four years ago.
One is that he is using a temperature controlled charger. This is very important if you are trying to charge at a high rate as over heating an LA cell is a pretty quick way to damage it.
The other is that he is charging Trojan T105s. These are constructed to take the stresses that high charge rates put on a LA cell. Most are not, even most other golf-cart grade deep cycle batteries will not readily tolerate this activity.
Charging a LA bank is really a complex equation that involves cell temperature, supply voltage and most of all - Time.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Battery charging confusion [message #105038 is a reply to message #104972] |
Thu, 04 November 2010 10:43 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I know my Chrysler XJ Jeep uses a batt temp probe to the computer. Reg is in the computer not the alt. GMs with the internal reg use a temp sense in the reg to emulate batt temps.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Battery charging confusion [message #105040 is a reply to message #105013] |
Thu, 04 November 2010 11:02 |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Senior Member |
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Thanks Ken,
Yes, I'm planning on getting the remote temp sense accessory for whichever charge controller I end up with. I'm looking at both Morningstar and Xantrex.
Thanks again.
J
76 PB
Portland, OR
> From: n9cv@comcast.net
> Date: Thu, 4 Nov 2010 01:27:19 -0500
> Subject: Re: [GMCnet] Battery charging confusion
> 14.8 will get you charged sooner, but not any more completely. I personally would not do it because of the risk of boiling and destroying the batteries.
>
> Some expensive charge controllers have a temperature probe that sits in the battery to tell to the charger to down shift when things get too warm. Your final charge to finish off the battery will be around 13.8 no matter what the initial charge rate was.
>
> Float or maintenance more is another thing and it is around 13.2 volts.
>
> If Bob was correct then every car and truck running around would be under charged. Every automotive alternator system I know of runs 13.8 to 14.2. Most of those that run up to 14.2 sense the alternator temperature and throttle down to 13.8 when it get warm. This reduces the charge rate and tops off the battery without over charging it.
>
> In another application I have several small battery packs that have thermistors implanted in them. The thermistors tell the matching smart charger when they are being over charged. Once the thermistor trips the charger throttles down and stays there until the pack is removed from the charger and is reconnected again. This arrangement allow much higher initial charging rates and shortens the normal slow 12 hour charge rate on a completely depleted battery to about 2.0 hours. It works.
>
> If you had similar smart charging technology built into your battery and a smart charger to interpret it, then you could go to 14.8 or higher on your GMC batteries. Without it I suggest you stay in the 13.8 to 14.2 volt range and float them to 13.2 when they are fully charged.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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