General Battery Charging Questions
lovin...@gmail.com
couple of questions in regard to battery charging that I can't seem
to work out on my own.
I have several general questions.
1. When charging up a brand new set of batteries 12x2v to the
recommended float of 28.8, how much would you expect the voltage to
drop when they come off float and there is no load attached....
2. The manual for my batteries says as a general guide the maximum
charge rate is 4% of C25. Which is 23.5 amps. But I'm unsure at what
that means. Does that mean 23.5 amps/DC? Or AC? Later on in the
document it gives these figures... Recommended charge rates, Peak 60
Float 28 Equalise 33 with the caveat (actual rates will depend on SOC
but it doesn't specify AC/DC or what voltage the bank is. I just went
and bought a 6.5kva generator cause I thought it was amps/ac....!!!!!!
3. The figure of a battery being about 80% efficient. Is that only in
regard to the imput. E.g You put 100ahr in, expect to have 80 amp/hr in
the tank and then if you invert that to 240 and your inverter is 90%
efficient then expect to get around 72amp/hours 'at the plug'
(forgetting about transmission loss)
George Ghio
> Hi guys...I'm still pretty green when it comes to solar and I have a
> couple of questions in regard to battery charging that I can't seem
> to work out on my own.
>
>
>
>
> I have several general questions.
> 1. When charging up a brand new set of batteries 12x2v to the
> recommended float of 28.8, how much would you expect the voltage to
> drop when they come off float and there is no load attached....
After charging if the batteries are not used, say over night, the
voltage should read around 25.4VDC
>
> 2. The manual for my batteries says as a general guide the maximum
> charge rate is 4% of C25. Which is 23.5 amps. But I'm unsure at what
> that means. Does that mean 23.5 amps/DC? Or AC? Later on in the
> document it gives these figures... Recommended charge rates, Peak 60
> Float 28 Equalise 33 with the caveat (actual rates will depend on SOC
> but it doesn't specify AC/DC or what voltage the bank is. I just went
> and bought a 6.5kva generator cause I thought it was amps/ac....!!!!!!
Batteries are DC so the charging is DC
>
>
> 3. The figure of a battery being about 80% efficient. Is that only in
> regard to the imput. E.g You put 100ahr in, expect to have 80 amp/hr in
> the tank and then if you invert that to 240 and your inverter is 90%
> efficient then expect to get around 72amp/hours 'at the plug'
> (forgetting about transmission loss)
>
Batteries are, sadly, only around 80 to 90% efficient. This should
always be part of a sizing calculation.
--
Posted via a free Usenet account from http://www.teranews.com
nicks...@ece.villanova.edu
>Batteries are, sadly, only around 80 to 90% efficient. This should
>always be part of a sizing calculation.
IIRC, the coulombic (round trip charging) efficiency is close to 100%
if they are not fully charged. Inverters are another matter.
Nick
George Ghio
Ah Nick, it is always a pleasure to read your posts. After all they are
so entertaining.
Perhaps you will be a bit more forthcoming and explain the efficiency of
charging an inverter.
lovin...@gmail.com
To clarify I guess my question is "In which function are batteries
only 80% efficient?"
E.g You give it 100 and it stores 80 Or You give it 100 it stores 90
and then delivers 80.
I was assuming that it's only 80% efficient at storing but that
can't be right because it must lose a certain amount in the deliver
or is that factored into the 80%
Solar Flare
other 10% out anyway.
Besides, suphuric acid tastes terrible.
<lovin...@gmail.com> wrote in message
news:1169163333....@38g2000cwa.googlegroups.com...
NoSuch...@bigfoot.com
> Would it matter? We know of no sneaky way to get inside and get that
> other 10% out anyway.
If a tree falls in the forest, and nobody is around to hear it, ...
8-)
lovin...@gmail.com
rlsu...@NOSPAMPUHLEEZschnapp.org wrote:
> Solar Flare wrote:
> > Would it matter? We know of no sneaky way to get inside and get that
> > other 10% out anyway.
>
> If a tree falls in the forest, and nobody is around to hear it, ...
>
> 8-)
>
Probably wouldn't matter at all. Just like it wouldn't mattter to our
every day life if we could disprove the existence of God - doesn't stop
people asking the questions though does it?.
Solar Flare
If a tree falls in a forest and nobody is around to hear it. Does it
make a noise?
The answer is NO. Noise is in the ear of the beholder. It makes a
sound though.
Poor example...LOL
"rlsu...@NOSPAMPUHLEEZschnapp.org" <NoSuch...@bigfoot.com> wrote
in message news:45b02109$0$27086$4c36...@roadrunner.com...
George Ghio
nicks...@ece.villanova.edu
>lovin...@gmail.com wrote:
>>
>> I was assuming that it's only 80% efficient at storing but that
>> can't be right because it must lose a certain amount in the deliver
>> or is that factored into the 80%
>>
>More like 10 on each side.
No. More like 97% round trip, at less than 90% SOC. See page 4:
http://www.battcon.com/PapersFinal2004/SymonsPaper2004.pdf
Also note the author cautions against SERIES battery strings.
Go back to welding, George.
Nick
wmbjk
>http://www.battcon.com/PapersFinal2004/SymonsPaper2004.pdf
Doesn't its conclusion about increased life span with shallow
discharges disagree with previous info (from a battery maker as I
recall) that you cited? I remember that one indicating that deeper
discharges resulted in the most total Ah available. I hope this latest
one is correct, most of my discharges have been shallow.
>Go back to welding, George.
He isn't needed there either. Please invite him to pursue his editing
"specialty" instead. :-)
Wayne
Martin Riddle
news:eon6o0$1...@acadia.ece.villanova.edu...
But he says at low charge rates. I guess it applies to low discharge rates
as well. And I dont see anywhere that charge rate percentage, is it C/10
C/20 C/50 ?
So how many people use low charge rates in a PV set up?
Cheers
nicks...@ece.villanova.edu
http://www.battcon.com/PapersFinal2004/SymonsPaper2004.pdf
>Doesn't its conclusion about increased life span with shallow
>discharges disagree with previous info (from a battery maker as I
>recall) that you cited?
Yes. Trojan's curves indicate otherwise.
Batteries are mysterious.
Nick
yoyo
>
> http://www.battcon.com/PapersFinal2004/SymonsPaper2004.pdf
>
> Also note the author cautions against SERIES battery strings.
>
> Nick
Well, you left out the key word 'long'. The article is really about the
DANGERS of LONG-string series; 50 or more cells and coupled with
inadequate maintenance. That is 100+ volts. It doesn't take a rocket
surgeon to figure out that connecting 1,000,000 cells might lead to
problems!
If, as you say, SERIES is bad; how do we get past 2volts?
John
wmbjk
As are some papers. How do you figure the author was able to reach
conclusions about efficiency without mentioning Peukert's equation?
Wayne
daestrom
<nicks...@ece.villanova.edu> wrote in message
news:eorngn$2...@acadia.ece.villanova.edu...
The nuclear submarine navy found that calcium-grid batteries last longer if
trickle *discharged* while on standby. Then once a week charging to bring
up to full capacity. This was quite different from the antimony-grid
batteries used on diesel-electric boats which self-discharged rather fast
and had a shortened lift if left in storage 'wet'.
All different kinds, all different results. But generally, reputable
manufacturers know their products. What type of alloy is used in the grids
of these batteries? Or is that 'proprietary' secret that the manufacturer
won't share?
daestrom