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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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 Posted: Mon Aug 05, 2013 7:12 pm Post subject: Battery question |
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My understanding is that it takes at least 13.8 volts to charge a 12 volt battery.Last Sunday I was using a Schumacher SC 8010A to charge a 12 volt 20 a.h. AGM battery. The charger started out at 12.5 volts and gradually climbed until after an hour the display was reading 15.5 volts. I disconnected the charger even though when I selected percent of charge it indicated 71 % charged. I used a Fluke VOM to check the battery and it indicated 15.4 volts. The battery was not even warm to the touch so I put the charger back on and continued charging until the battery was at 95% charge at which time the charger was still at 15.5 volts. The battery was barely warm to the touch. Again, with battery disconnected from the charger it tested at 15.4 volts. The battery seemed to work normally when we attempted to start the engine.
Why would the charger charge at such a rate?
Why would a 12V battery test at 15.4 volts?
Rick Girard
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Tue Aug 06, 2013 3:04 am Post subject: Battery question |
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At 10:10 PM 8/5/2013, you wrote:
My understanding is that it takes at least 13.8 volts to charge a 12
volt battery.
Last Sunday I was using a Schumacher SC 8010A to charge a 12 volt 20
a.h. AGM battery. The charger started out at 12.5 volts and gradually
climbed until after an hour the display was reading 15.5 volts. I
disconnected the charger even though when I selected percent of
charge it indicated 71 % charged. I used a Fluke VOM to check the
battery and it indicated 15.4 volts. The battery was not even warm to
the touch so I put the charger back on and continued charging until
the battery was at 95% charge at which time the charger was still at
15.5 volts. The battery was barely warm to the touch. Again, with
battery disconnected from the charger it tested at 15.4 volts. The
battery seemed to work normally when we attempted to start the engine.
An idealized automated battery charging profile looks
like this:
http://tinyurl.com/k6xr9mk
As a practical matter, there are variations on
the theme that will produce a family of recharge
profiles
http://tinyurl.com/m3o6mtu
Why would the charger charge at such a rate?
Probably because it was conforming to design goals
Why would a 12V battery test at 15.4 volts?
Because you measured the voltage too soon. The
REAL voltage representing state of charge can
be measured only after the battery has been
disconnected the charger for several hours.
If the battery is healthy, something on the order
of 12.8 to 13.0 volts for a fully charged open
circuit value.
Bob . . .
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Tue Aug 06, 2013 6:38 am Post subject: Battery question |
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Thanks All, This was my first go 'round with a smart charger. Always good to learn something.
Rick
do not archive
On Mon, Aug 5, 2013 at 10:10 PM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:
| Quote: | My understanding is that it takes at least 13.8 volts to charge a 12 volt battery.Last Sunday I was using a Schumacher SC 8010A to charge a 12 volt 20 a.h. AGM battery. The charger started out at 12.5 volts and gradually climbed until after an hour the display was reading 15.5 volts. I disconnected the charger even though when I selected percent of charge it indicated 71 % charged. I used a Fluke VOM to check the battery and it indicated 15.4 volts. The battery was not even warm to the touch so I put the charger back on and continued charging until the battery was at 95% charge at which time the charger was still at 15.5 volts. The battery was barely warm to the touch. Again, with battery disconnected from the charger it tested at 15.4 volts. The battery seemed to work normally when we attempted to start the engine.
Why would the charger charge at such a rate?
Why would a 12V battery test at 15.4 volts?
Rick Girard
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
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Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
[quote][b]
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dave.saylor.aircrafters(a
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| Posted: Tue Aug 06, 2013 7:22 am Post subject: Battery question |
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Bob, can you comment on Odyssey's requirement to keep the charge below 15 volts? Â See page 6:
http://www.odysseybattery.com/documents/US-ODY-OM-011_0213.pdf
This requirement has also been given to me by phone on a few occasions.
My understanding is that the battery has to see some extended time above 15 volts to cause any ill effects, particularly off-gassing. Does the SC 8010A drop below 15 quickly enough to avoid off-gassing, or would it be considered inappropriate for Odyssey batteries?
Dave Saylor
831-750-0284 CL
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Tue Aug 06, 2013 12:58 pm Post subject: Battery question |
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At 10:20 AM 8/6/2013, you wrote:
| Quote: | Bob, can you comment on Odyssey's requirement to keep the charge below 15 volts? Â See page 6:
http://www.odysseybattery.com/documents/US-ODY-OM-011_0213.pdf
This requirement has also been given to me by phone on a few occasions.
My understanding is that the battery has to see some extended time above 15 volts to cause any ill effects, particularly off-gassing. Does the SC 8010A drop below 15 quickly enough to avoid off-gassing, or would it be considered inappropriate for Odyssey batteries?
Dave Saylor
831-750-0284 CL |
Have no idea my friend. Haven't tested it. Here's a chance
for you to make a mark in the understanding of the various
batteries and their accessories.
If you acquired this (or something like it)
http://tinyurl.com/lv2d6r4
you could hook your charger to a run-down battery and
plot the recharge curve. I think I have an idea for
how this critter could also watch the recharge current
curve as well.
The DAS would let you do data gathering in flight
tests too.
With respect to Odyssy's user data, I don't know
why they would be any more vulnerable to service
life degradation due to top-off protocols than
any other manufacturer. ALL of them would like
to see their recharge cycles stay at or below
15 volts . . . In fact, I've been disappointed
that Schumacher hasn't upgraded their charger
designs to do the idealize profile with a top-off
to be pegged at 14.8 volts and held until charge
current drops to 100 mA.
If you deep cycled your Odyssey battery and
hit it every time with the "too hot" Schumacher
charger every time, I think the deep cycle treatment
would be harder on the battery than the aggressive
top-off. Under ideal conditions, a ship's battery
NEVER sees a recharge from deep discharge so
top-off protocols become moot. The few times
that accident or circumstance demands a hot
top-off shouldn't be a big event in the battery's
service life.
But it would be very interesting to know how
that charger behaves when paired with your particular
battery. If top-off plateau is higher than specified,
then the time required for the recharge current to
fall below the sustain decision point will be stretched
out . . . wonder by how much?
Bob . . . [quote][b]
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