General Battery Charging Questions

 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....

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)

  lovingit69@gmail.com wrote:

After charging if the batteries are not used, say over night, the
voltage should read around 25.4VDC

Batteries are DC so the charging is DC

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

 

IIRC, the coulombic (round trip charging) efficiency is close to 100%
if they are not fully charged. Inverters are another matter.

Nick

 nicksanspam@ece.villanova.edu wrote:

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.

--
Posted via a free Usenet account from http://www.teranews.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%