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How to best connect up 3 x leisure batteries


Rebotco

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I am planning to move my 4 x 110Ahr leisure batteries to a new position where there is only room for three.

So the idea is to fit 3 x 130Ahr batteries instead. Slightly less total power available, but possibly slightly better SOC may be maintained.

I can find quite a bit of info on connecting banks of 2 or 4 or 6 etc, but nothing on 3 x batteries.

I would appreciate the battery gurus' advice on how best to arrange the batteries' interconnections.

If it is relevant I am a leisure boater and the boat is often left for several weeks unattended.

Thanks in advance.

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2 hours ago, WotEver said:

Method 2 here:

http://www.smartgauge.co.uk/batt_con.html

Hope that helps :)

I have used Method 2 which according to this link still has a small imbalance of discharge current according to position.

I was curious because I thought this configuration was optimum. So I've just put some numbers into a spreadsheet for equal current drain independent of position and I get 4 x 12V batteries.

If I put the website values as per Method 2 I get a mismatch of battery EMFs.

If anyone knows better or wants my spreadsheet..............................

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4 hours ago, Mikexx said:

I've just put some numbers into a spreadsheet for equal current drain independent of position and I get 4 x 12V batteries.

That's not a lot of help to the OP who only has room for 3. Gibbo's method 2 is the best for 3 batteries unless you go to the trouble of busbars which is complete overkill for 3 batteries. 

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7 hours ago, WotEver said:

That's not a lot of help to the OP who only has room for 3. Gibbo's method 2 is the best for 3 batteries unless you go to the trouble of busbars which is complete overkill for 3 batteries. 

 

I also recommend Method 2, though obviously applied to 3 batteries.

My issue is I don't see it as a sub-optimum solution as per the link.

Edited by Mikexx
Typo
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7 minutes ago, Mikexx said:

I also recommend Method 2, though obviously applied to 3 batteries.

My issue is I don't see it as a sub-optimum solution as per the link.

The sub-optimalness (hey, I made up a word!) wouldn't be noticeable away from the test bench or theoretical maths but Gibbo's calculations on that page clearly demonstrate that it's not optimal. Not anywhere near enough of a difference to get overly concerned about but nevertheless the maths is there to 'prove' it. 

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I'm using option 2 for 3 leisures. Easy to setup. 

 

16 hours ago, Rebotco said:

If it is relevant I am a leisure boater and the boat is often left for several weeks unattended.

Thanks in advance.

A solar panel would do the job with the SOC while you are away. Same use as you with 200W. Works well. 

Edited by Jak
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On 15/08/2017 at 13:31, WotEver said:

The sub-optimalness (hey, I made up a word!) wouldn't be noticeable away from the test bench or theoretical maths but Gibbo's calculations on that page clearly demonstrate that it's not optimal. Not anywhere near enough of a difference to get overly concerned about but nevertheless the maths is there to 'prove' it. 

 

I redid the calculations and naturally I agree spot on with the currents in Method 2, even though the result doesn't looking intuitively correct. I should never have doubted Gibbo's calculations!

 

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5 hours ago, rustydiver said:

Got me thinking now to wire my bank of 4 up like method 2. I've got to remove them to paint under them in the engine bay. 

You're never telling us they're as per example 1, surely?

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