Which battery type is best suited for high rate of charge?

 Hi all.

For 7 months of the year I need to use a generator to charge the
batteries due to a huge ridge at the back of the property that gives
the PV nothing to work with.

I currently have a 7kw generator.

Q. Is there any battery type that is best for accepting a high rate of
charge that would allow me to run the generator for shorter periods at
a higher rate. Or is this logic flawed?

This document http://www.rpc.com.au/products/services/REG-LSettings.pdf
gives the charge rates for several brands/types and i noticed that my
current set of batteries can only be charged at a max rate of 4% of C25
where as the Sonnenschein batteries can be charged at 50% of C100.
However the absorbtion period of the former is .5 hour and the
Sonnenschein's are 3 hours.

Is it going to be swings and roundabouts with this? Or is there
something that would suit my requirement?

  On 24 Jan 2007 15:40:27 -0800, lovingit69@gmail.com wrote:


Your battery maker will recommend bulk charging at up to the highest
rate, then tapering off the current to maintain absorption voltage for
a certain period, generally an hour or more. They usually specify that
you do the whole bulk and absorption routine at least once a week.
That absorption stage will likely extend your charging time
considerably, which is why generator-based charging is often limited
to bulk charging only. .


It appears that you have PVstor batteries. The correct recommended
charging rates can be found on pg. 26 here
http://www.solartech.com.au/pdfs/products/batteries/pv_stor_manual_5.pdf .

Wayne

 Cheers Wayne..

I have that doc back to front and that's why I'm confused. I've got the
785's and it gives rate of 60amps (which is what I have been charging
them at).

But just above that in section 4.4.4 it states that as a guide it
should be C25/25 which for those batteries is around 23 amps. Do you
think they are just giving this as a general rule for batteries to be
on the conservative side and then giving the actual figure below?

Also the other thing I was confused over was the amperage rates listed

Peak 60
Float 28
Equalise 33

Peak and Float I get...but I thought that equalise would have required
more than peak as it pushes the voltage higher than peak.



2nd.


I thought most generator charging was limited to bulk and absorbtion
but not float.

Have I got this wrong?

Thanks for the info.


Just out of interest...what charge rate do you use for your setup?


charging at up to the highest

appears that you have PVstor batteries. The correct recommended

herehttp://www.solartech.com.au/pdfs/products/batteries/pv_stor_manual_5.pdf .

 On 24 Jan 2007 16:40:59 -0800, lovingit69@gmail.com wrote:


bulk charging at up to the highest

appears that you have PVstor batteries. The correct recommended

herehttp://www.solartech.com.au/pdfs/products/batteries/pv_stor_manual_5.pdf .

You should contact the maker for specifics if it matters to your
application. Keep in mind that some controllers are simple
voltage-controlled relays - single stage. With those the user might
want to limit max current, since instead of charging gradually
tapering off for absorption and float, the current is going to be on
or off while the controller tries to hold the batteries at a
compromise voltage - lower than the usual bulk, and higher than the
usual float. In practice it can be better than it sounds. For
instance, with solar supply, in afternoon when voltage has risen,
available current is falling off.


I imagine that those are guidelines for maximum rates. The spec for
equalization is generally a voltage, and the current will be whatever
is required to maintain that voltage. The usual idea is to fully
charge the batteries first, so equalization current will be something
more than what's required to maintain float voltage.


It depends on the controller and your needs. If one's setup has only a
generator source, then an automatic controller capable of the normal
three-stage routine would be best, except that the user would have to
suffer the extended running time required for a finish charge. Perhaps
not every time, but at least as often as the battery maker recommends.
But if one is only using a generator for backup, then quitting once
bulk is finished should be practical since finish charging happens
often enough with the main source - solar or whatever.


It varies constantly depending on source and loads. Source current can
be as high as the 90s with sun and wind combined. But even then the
batteries generally see far less because there are always loads
present. Shop loads are occasionally over the rated fuse limit of 400A
for short durations. Therefore we can have discharge currents in the
300A range concurrent with maximum solar and wind. *Routine* charge
current with solar alone, or combined with light and variable winds,
and normal variable loads, tends to be in the 30 to 40A range.
Backup generator bulk source (50 to 100 hours per year range) is 75A,
but it tapers to about 70A as the generator heats up.
Backup to the backup :-) ( a few hours per year) can do as much as
120A. I sometimes use that generator only because it needs a run once
in a while, or when I can use the heat in the shop (that generator can
be used indoors or out).
Same as with our normal charging sources, the actual charge currents
are somewhat less due to routine loads, and even lower with some
elective loads. For example, we don't usually run the well pump on
days when power is in short supply. But when there are cattle here and
we need to pump the well every day, we run it concurrent with the
generator to minimize battery cycling. That turns the normal generator
source of 75A into a charge current of about zero for as long as the
pump is running.

Wayne

 

lEAD ACID  normal wet type can take a high rate of charge but you will need
to keep an eye on them and add water when needed..