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battery charging

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Posted by Tim on December 8, 2006, 7:43 pm

I have a small solar set-up that I use to provide power to light a
small stable block. I set it up in the summer, and have discovered now
that we are in winter that I have put the panels in just about the
worst place due to the fact that they are in a lot of shade. I will
move the panels, but for a variety of reasons don't want to do it until
next summer. In the meantime I need to provide additional charging to
my battery bank. The bank consists of four 110Ahr leisure batteries
providing a total of 440Ahr. I do not really want to split the
batteries up, and I don't really want to purchase an expensive battery
charger. Is there any good reason why I cannot simply hook up a couple
of ordinary car battery chargers to this set up to charge the bank? I
have two chargers (an 11amp and an 8amp), but they say that they are
suitable for (up to) 110Ahr and 80Ahr batteries respectively. Will they
charge the bank (but slowly) or will they be ineffective?

Posted by Vaughn Simon on December 9, 2006, 12:39 am

     The biggest danger is that the battery chargers will overcharge your
batteries.  Your average automotive battery charger is not automatic, and is
certainly not a float charger.  We have some solar experts here and listen to
them before you listen to me, but it may be possible to connect your auto
battery chargers to the input of your solar controller, which would protect your
batteries from overcharge.

    Do you have a 12 volt system?


Posted by homeboy465 on December 9, 2006, 11:31 am

if using a 12v system then the best peice of kit you can have and one that
is worth while is a 'Shunt Voltage Regulator' one i have herd of being used
with  5 golf cart battries. The shunt just sits between the powersorce
wither it is your solar pannels a wind turbine a petrol generator aor any
other powersorce and as soon as the battries are full  it cuts off so not to
over  charge the battries. it also has a 12V output and this in turn can be
connected to a inverter of your own needs the system i  saw was just being
used to power a laptop and waj  only a 150W model i must add that the
inverter used was for a 230V system beuing here in the uk.

the shunt used was a SYGMA 300W/30A and i must say that as this guy went
from a single solar pannel input to 3 pannls and a turbine he had to ad a
hefty diode and heatsink so ensure that the battries didn;t discharg back to
the pannels at night but you should have one in place already. for more
details contat me and i will try and scan the artical in so show you what
thety did.

Posted by Tim on December 9, 2006, 1:34 pm

Thanks for the advice.

Just so that you know I too am in the UK. I currently have three panels
with a nominal output of 200W, and use a Morningstar PS-30 solar
controller. I did not want to connect the car charger outputs to the
input of the controller as the manual specifically warns against that,
but also says that connecting other power sources to the battery side
is OK.

I am not too concerned about overcharging the batteries, as I keep a
pretty close eye on them. What I was not sure about was whether the
fact that the chargers state they are suitable for a specifc size of
batery means that they will not be able to provide sufficient output to
charge my larger battery bank.

One of the chargers does have the ability to drop back to a float
charge once it thinks the battery is fully charged, but the other one
does not. However after trying the set-up I mentioned, I have yet to
see the voltage rise above 13.2V so I guess these two charges are
struggling a bit. The initial voltage was arround 12.4.

Thanks again for the help.

homeboy465 wrote:

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