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Techie question

 
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Andy Hunt



Joined: 24 Nov 2005
Posts: 6760
Location: Bury, Lancashire, UK

PostPosted: Tue May 08, 2007 3:12 pm    Post subject: Techie question Reply with quote

Just hoping that Mike or Ken or anyone else can answer this one . . .

Can I connect a 12V power circuit directly to one of the batteries I am using for my existing solar PV system?
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mikepepler
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Joined: 24 Nov 2005
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Location: Rye, UK

PostPosted: Wed May 09, 2007 8:45 am    Post subject: Reply with quote

If the batteries are in series, then I think you shouldn't. This is because you end up with batteries in the chain charged at different levels, and that can mess things up, maybe even damage the batteries? Ken, do you know more?

This is why I'm using a 12V system, because I have loads of adaptors I can run off 12V.
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Andy Hunt



Joined: 24 Nov 2005
Posts: 6760
Location: Bury, Lancashire, UK

PostPosted: Wed May 09, 2007 10:13 am    Post subject: Reply with quote

Thanks Mike, I thought that might be your answer. Just mulling a few options at the minute . . .
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Bandidoz
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PostPosted: Wed May 09, 2007 12:36 pm    Post subject: Reply with quote

If you need to step down from, say, 48V, just use a DC-DC converter.

Another option is, if you have, say, 4 equivalent 12V lights, put them all in series (mmmmm Christmas tree lights Wink )
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Andy Hunt



Joined: 24 Nov 2005
Posts: 6760
Location: Bury, Lancashire, UK

PostPosted: Wed May 09, 2007 12:41 pm    Post subject: Reply with quote

Thanks Bandidoz . . .

(faint sound of cogs whirring . . . )
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adam2
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PostPosted: Thu Jul 05, 2007 9:01 am    Post subject: Reply with quote

As others have suggested, if 12 volt batteries are connected in series it is unwise to connect a load to only one of the batteries. it will result in unequal states of charge in the batteries and probably shorten the life.

The best solution is to purchase a DC to DC converter to convert the battery voltage to the desired 12 volts.

A cheaper way to obtain 12 volts from a 24 volt battery bank is to connect the 12 volt load to only one battery as originally suggested.
To avoid the enequal charging noted above, change the connections daily, in order to eqaulise to load on the two batteries.

A suitable changeover switch would of course be better than actually altering battery terminals daily.

alternativly if you have two or more 12 volt loads to be supplied from a 24 volt battery, it may be possible to to connect some loads to each battery. the daily amp/hour consumption of the two loads must of course be equal for this to work.

yet another possibilty is of course to instal a small 12 volt pv system, independant of any higher voltage system. this is the safest solution if the main pv system uses a dangerous voltage.
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