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Connecting batteries in parallel - some questions:

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Posted by Jim on December 27, 2009, 8:10 pm

I have just begun experimenting with a Kyocera 50 watt and have a 65
watt panel ordered, using the smaller panels mainly because they
can be easily handled, and I can buy one when I get some
extra cash.  Each panel has a Morningstar SunGuard
controller, good for 4.5 amps or up to an 80 watt panel.

According to the Morningstar website, as money becomes
available, I can just keep adding the panels and controllers
to the same battery bank with no interaction, and the
controllers will act in unison to charge the batteries as
if it was one larger controller.  Is this the case or is it
just advertising baloney?  I'd like to find out for sure
before buying a 3rd panel and controller.

About the battery "bank".  Are there any rules about adding
additional batteries in parallel?  It seems to me that if
you keep adding them in parallel, they should be somewhat
matched, that is, same brand and model, keeping capacities
of each unit about the same.  Is this correct, or can you do
like they did in that TV show "The Colony" where they got
all kinds of odd size/condition batteries and wired them in parallel
for their "bank"?

I now have a new "Energizer 27DC" deep cycle, and an
older "Energizer 73DT" available to play with, and they
are physically different sized and probably electrically
different.  The Energizer 27 DC is available at the local
Sam's club and is the largest one they carried that I could
lift without too much problem, and is supposedly for "Deep
Cycle" use.  

Anyway, should I just keep buying the "Energizer 27DC"
when funds become available and adding them in parallel, or
can you just add any size 12v battery as long as it's new and
in good shape?  I want to keep things to manageable weights
and sizes so I can eventually move everything to another
location when things get nasty....

I guess what I'm lookig for is a good tutorial on how to
build up a battery "bank" using the smaller batteries.
Sam's Club also carries some larger 6V batteries probably for
golf carts,  but they are pretty heavy for one person to
be throwing around.  Should I go with them in series-parallel
or can I stick with the Energizer 27DC to build up a bank?
Trojans are not available locally without paying big shipping costs.

I'll be using the bank only during emergencies for powering ham radio
12v Solsum lamps and some other 12V linear flourescents,
some computer equipment and perhaps some small kitchen appliances
running off an inverter.  Also a 12V fan or two, (as what I went
through after Katrina I never want to go through again).
We also have a Honda (converted to NG) generator thanks to FEMA
for backup as long as the natural gas/gasoline/propane lasts, but
if we have to leave for parts unknown we can't count on fuel
availability for the Honda.

(FYI: I have found that not all inverters are equal if you are
running radio equipment.  The el-cheapo inverters you buy in auto
parts stores put out huge amounts of hash all over the radio
spectrum, making sensitive reception impossible.  I found this out
when attempting to use a 500 watt inverter while operating my
mobile HF station, it destroyed reception.  When I buy another
inverter i will bring a portable shortwave receiver and give
it the reception test).  Anyone know a good clean inverter?

Posted by ghio on December 28, 2009, 12:55 am

Regulators - Buy one (1) that will handle all the panels that you
intend to purchase.

Batteries - Should all be of the same capacity and age. Buy a set that
will meet your needs for the system you intend to build.

Inverters - Buy one (1) true sine wave inverter that is of a size that
will meet the total load expected from your system.

Lights - Consider LED lighting. There are some very good products
available on the market.

El-cheapo - For an emergency power back up, ROTFLMAO.

Posted by clare on December 28, 2009, 4:46 am

The general rule is only parallel connect cells of the same size,make,
and age. Sometimes you can get away with mixing  brands or capacities
or ages - other times it "bites you".
Most definitely you have the best chance of getting maximum life and
performance out of a matched set - but even better is to buy big
enough and series connect - ie - buy big 6 volts and use 2 in series
rather than small 12 volts (physically the same size) in parallel.

Posted by z on December 28, 2009, 7:08 pm


I don't know about the morninstar ones.  I don't think they'd lie to you
about that, though.  Morningstar is pretty respected company I think.

You can run more than one controler -- like I have one 10 amp controller
for  some of my solar panels, and another 35 amp that takes my hydro + 2
other large panels.  So if you split your panels each into a different
controller that can take the amps then you'd be OK.

As I understand it, the weakest, oldest battery in the bank will
determine the efficiency of all the other batteries.  That's why everyone
says 'buy the same kind, same age all at once'.  Like clare & ghio said.  
So when you add another battery you can add some capacity but the rest of
the bank will only charge to the capacity of the worst battery in the

I had the same problem with the cheap inverters that can be reduced by
getting an RF filter, but once I had the $$ I got a xantrex 1000 watt
true sine and haven't been disapointed.  It's got a remote panel so you
can see what your loads are and it goes into sleep mode etc when you are
not using it.  No RF interference and nice clean power. Found one on
fleabay for 200 bucks .. most of the time they are a lot more though.

Best of luck


Posted by Jim on December 29, 2009, 3:32 am

I found this site that recommends NOT to use parallel batteries:


I am thinking I'll get the same Energizer deep cycle and place
them in parallel, as they will all be same and new, and I can
just lift them without too much trouble.  The 6V batteries were
too heavy for this old geezer and had no handles on them.  Am
awaiting the second panel.

Thanks for all the suggestions.


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