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Best way to interconnect 6 x leisure batteries?


Jay88
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Hi again,

I have posted this question in a different topic but decided to make separate it for ease of tracking.

 

Question: Any recommendations on the best way to interconnect 6 x leisure batteries? I know there is a preferred method for 4 x leisure batteries (as per Smartgauge website- Method 4: http://www.smartgauge.co.uk/batt_con.html) but what about 6  x batteries?  Currently it appears my batteries are done via method 2 but with the main feeds taken from the middle battery. Hope that make sense.... Thoughts?

 

Any advice is highly appreciated.

 

Cheers!

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Method 2 can use as many batteries as you wish, just take + from one end & - from the other

 

Added -  if you use method 2 but take from the middle battery then the middle battery (which is really 2 banks of method 1 joined together) will do slightly more work as it has the lowest number of connections and shortest cables.  But in the real world, so long as you have good chunky cables from the middle battery to the others batteries with good crimps and clean connections I am not convinced it will make that much difference.  For me it would be a ‘change that one day’ but never actually do it.

Edited by Chewbacka
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2 minutes ago, Jay88 said:

OK - so my current set-up is like this but is it best to have the installation feeds from batteries 1 and 6 instead of both from battery 4?

 

image.png.6f988f59914faeda03126f85d699bdfe.png

As I said above this is not method 2 but two method 1 banks where battery 4 is ‘shared’, so bank 1 being 1-4 and bank 2 being 4-6.  So as you can see 4 works hardest, then 3&5, then 2&6, then 1.  
The easiest thing to do (depending on cable runs etc) would be to take the - from one end, and + from the other.

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In my opinon, after a career designing and project managing critical power installations for telephone exchanges, data centres and hospitals, the method of interconnecting doesn't matter providing the cables and interconnects are adequately rated.

 

UPSs often have several strings of 200 x 2 volt cells connected in series/parallel and the power takes offs are invariably on the first and last cells.

  • Greenie 3
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Checking my new boat I found that the bank of 6 had the main cables connected to batteries 1 and 6. I did the calcs and theoretically, connecting to batteries 2 and 5 is the best as matty40s says, but when I checked the size of the interconnects I decided to leave them as they are.

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5 hours ago, cuthound said:

In my opinon, after a career designing and project managing critical power installations for telephone exchanges, data centres and hospitals, the method of interconnecting doesn't matter providing the cables and interconnects are adequately rated.

 

UPSs often have several strings of 200 x 2 volt cells connected in series/parallel and the power takes offs are invariably on the first and last cells.

Is it not so much the size of the interconnects (provided they are large enough), but the cleanliness and number of connections?  As I understood it, only very small resistances could influence how the volts are shared.

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13 hours ago, dor said:

Is it not so much the size of the interconnects (provided they are large enough), but the cleanliness and number of connections?  As I understood it, only very small resistances could influence how the volts are shared.

 

It it true that a few micro ohms of resistance will influence current distribution in parallel circuits and volt drop in cables and across connections, so it is best to minimise this by using large cables and interconnects and ensuring all terminations are clean and tight.

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Thanks all for the responses and I if I have enough cabling I'll go for the 2-5 setup

 

As I'm unsure of the ratings of the cables and interconnects, is there a recommended rating? 

 

Also I have noticed that the engine battery is connected to battery 1 (see photo) which has raised a few more questions..

 

After scrutinising the boats Electrical System Schematic, it appears the setup from the builder is as follows;

- 2 x 80A alternators with a Sterling A-B charger and a Bat-Bat charger

     *Alternator 1 goes to the B-B charger which connects to the Bow battery and also the A-B charger

     *Alternator 2 connects to the A-B charger which then connects to the Engine battery via the Engine Battery Isolator & the Leisure batteries via the Leisure Battery Isolator   

 

So while the schematic has the engine battery and leisure batteries completely separate, why in reality are they connected? Maybe I'm reading something wrong here? I always thought that the 2 x battery banks should be separate so if the leisure batteries ever die, the engine start battery is still good to go as it's on a different system as such.

 

Thoughts?

 

I would normally take a picture of the boats electrical system and post it here but it's very blurry and wouldn't be clear, maybe I'll do another PPT..

IMG_6712.JPG

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You will normally find the negatives are connected, the separation is in the positive side via the Isolators.

 

This is obviously completely opposite if the Isolators are in the negative side(not common, but does exist)

Edited by matty40s
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