Home » Public Forums » GMCnet » An alternative for Battery Charging (Might this be interesting for us ??)
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| Re: [GMCnet] An alternative for Battery Charging [message #233717 is a reply to message #233706] |
Sun, 22 December 2013 19:03   |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| Robert Mueller wrote on Sun, 22 December 2013 17:17 |
G'day,
I know I'm sticking my neck out to respond to this question as I am "Electrically Challenged" but here goes; I vaguely remember
reading that a charging system can charge a battery only at an amp rate that the battery will accept; will a battery accept 200
amps?
Regards,
Rob M.
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Rob,
Your memory is accurate.
Short answer: Sort of Yes - Maybe and not for long
(Is that ambiguous enough for you?)
Let's limit the discussion to conventional lead/acid banks of flooded cells (you can open a cap and see electolyte).
LA's are limited both by temperature and charge voltage available. If there is more charge voltage being applied than they like, they will turn the excess into heat. This will both evaporate the water (and some acid) in the electrolyte and damage the lead-sponge that is the active plate in the cell. As the cell temperature rises, the charge voltage can also rise, but the efficiency of the charge can be reduced dramatically.
So, yes, you can throw 200 amps at a battery, but not for very long.
Working example:
If you have a bank composed of GC-2s (~225AH) at 50% and you put power to them (without any respect for the light bulbs in the coach) to get a 200 Amp charge going, (speculation based on significant experience from here) and planned to maintain that for an hour and one quarter. At the end of that hour, you will have a very hot bank, acid fumes all over and about an 85~90% charge that has had its useful life shortened by some (unknown) amount.
Why?
Three problems here. The heat, the rate and the time.
Heat is not good because is causes the things mentioned above and is implicated in causing the changes to the lead such that the chemical reactions required become less reversible.
The rate and the time kind of ball together here, but I will try to pull them apart enough so both cats are visible. The biggest part of the rate of charge is the heat, I talked about that, but the other part is the reverse of the LA battery gotcha called the Peukert exponent. This silly 19th century German pointed out that if you try to discharge an LA battery fast, it will not have as much power available as if you discharge it slowly.
Well the same is true for charging.
The time factor is also part of Peukert's damn number. This side is a result of the fact that a flooded cell needs to circulate the electrolyte to get full advantage of it. This circulation is driven by the change in density of the electrolyte and that does not have a lot of force to it.
Ready, here comes another little wrinkle with the Peukert thing. Which ever way you are going, the density circulation wants to go the other way from the way the thermal circulation would drive it ....
Boy, I like the PD box that I can just plug in and forget.
Matt - still here to answer the new questions I just raised.
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] An alternative for Battery Charging [message #233758 is a reply to message #233717] |
Sun, 22 December 2013 23:27 |
Ronald Pottol
Messages: 505
Registered: September 2012
Location: Redwood City, California
Karma: -2
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Senior Member |
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Quick rule of thumb, max charge rate or sustained discharge is 25% of
capacity, do your 200 amps of charge would be right for an 800 amp hour
battery.
Plato seems wrong to me today.
On Dec 22, 2013 5:04 PM, "Matt Colie" <matt7323tze@gmail.com> wrote:
>
>
> Robert Mueller wrote on Sun, 22 December 2013 17:17
> > G'day,
> >
> > I know I'm sticking my neck out to respond to this question as I am
> "Electrically Challenged" but here goes; I vaguely remember
> > reading that a charging system can charge a battery only at an amp rate
> that the battery will accept; will a battery accept 200
> > amps?
> >
> > Regards,
> > Rob M.
>
> Rob,
>
> Your memory is accurate.
>
> Short answer: Sort of Yes - Maybe and not for long
> (Is that ambiguous enough for you?)
>
> Let's limit the discussion to conventional lead/acid banks of flooded
> cells (you can open a cap and see electolyte).
>
> LA's are limited both by temperature and charge voltage available. If
> there is more charge voltage being applied than they like, they will turn
> the excess into heat. This will both evaporate the water (and some acid)
> in the electrolyte and damage the lead-sponge that is the active plate in
> the cell. As the cell temperature rises, the charge voltage can also rise,
> but the efficiency of the charge can be reduced dramatically.
>
> So, yes, you can throw 200 amps at a battery, but not for very long.
>
> Working example:
> If you have a bank composed of GC-2s (~225AH) at 50% and you put power to
> them (without any respect for the light bulbs in the coach) to get a 200
> Amp charge going, (speculation based on significant experience from here)
> and planned to maintain that for an hour and one quarter. At the end of
> that hour, you will have a very hot bank, acid fumes all over and about an
> 85~90% charge that has had its useful life shortened by some (unknown)
> amount.
>
> Why?
> Three problems here. The heat, the rate and the time.
> Heat is not good because is causes the things mentioned above and is
> implicated in causing the changes to the lead such that the chemical
> reactions required become less reversible.
> The rate and the time kind of ball together here, but I will try to pull
> them apart enough so both cats are visible. The biggest part of the rate
> of charge is the heat, I talked about that, but the other part is the
> reverse of the LA battery gotcha called the Peukert exponent. This silly
> 19th century German pointed out that if you try to discharge an LA battery
> fast, it will not have as much power available as if you discharge it
> slowly.
>
> Well the same is true for charging.
> The time factor is also part of Peukert's damn number. This side is a
> result of the fact that a flooded cell needs to circulate the electrolyte
> to get full advantage of it. This circulation is driven by the change in
> density of the electrolyte and that does not have a lot of force to it.
> Ready, here comes another little wrinkle with the Peukert thing. Which
> ever way you are going, the density circulation wants to go the other way
> from the way the thermal circulation would drive it ....
>
> Boy, I like the PD box that I can just plug in and forget.
>
> Matt - still here to answer the new questions I just raised.
> --
> Matt & Mary Colie The majestic, once snow covered glacier Chaumière is in
> for the winter.
> '73 Glacier 23 With 4 Rear Brakes that pull as they should
> SE Michigan - Twixt A2 and Detroit
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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