The best way to wire 6 volt batteries to give a 12v system?

[Iceblink]

My boat has 6 separate 6volt batteries wired in series and parallel to make up a 12v system but it hasn't been wired in the most obvious configuration. I have attached a diagram. Can anyone see any good reason for this? As is is wired at the moment if one of the fuses blows the electrics remain on using the power from batteries that are still connected at a reduced capacity but this is also potentially troublesome because you may not realise that a fuse has blown and the batteries that have been disconnected will prob just go flat and end up damaged. Any help would be much appreciated. cheers.

https://www.flickr.com/photos/135789728@N04/21793362931/in/dateposted-public/

 

[yachtorion]

My boat has 6 separate 6volt batteries wired in series and parallel to make up a 12v system but it hasn't been wired in the most obvious configuration. I have attached a diagram. Can anyone see any good reason for this? As is is wired at the moment if one of the fuses blows the electrics remain on using the power from batteries that are still connected at a reduced capacity but this is also potentially troublesome because you may not realise that a fuse has blown and the batteries that have been disconnected will prob just go flat and end up damaged. Any help would be much appreciated. cheers.

https://www.flickr.com/photos/135789728@N04/21793362931/in/dateposted-public/

Any chance it could have originally been two banks that been joined?

 

[prv]

The separate fuses make no sense.

I would keep the series connections forming three 12v pairs, then connect the pairs in parallel, then take the positive cable from one corner of the grid and the negative from the diagonally-opposite corner. It's possible that there's some even cleverer arrangement, but this is simple and should be well-balanced enough in practice.

See http://www.smartgauge.co.uk/batt_con.html for a general discussion of the issues.

Pete

 

[oldharry]

Looks eminently sensible to me, reducing the possibility of a total power outage, if it is arranged that one bank supplies 'essentials' like radio and engine, leaving the other for 'domestic' use. Similar to a boat that has a separate starter battery. However if it worries you, just bypass one of the fuses by connecting the two + leads from the batteries together to go through one fuse, so that all 3 12volt pairs are in parallel.

EDIT, it does occur to me that the combined capacity of the two fuses will allow the battery bank to push twice the rated amperage before anything blows: I.e if the fuses are rated 20 amps, it would take a 40+amp load to blow them, which may be a lot more than the wiring can take if it was designed to take 20 amps. So unless the 'fail' load is shared between the two fuses (i.e 2x 10amp fuses with a combined failsafe load of 20 amps, then converting to a single fuse you would need to uprate the fuse to 20amps - or whatever the load rating is.

 

[prv]

Looks eminently sensible to me, reducing the possibility of a total power outage, if it is arranged that one bank supplies 'essentials' like radio and engine, leaving the other for 'domestic' use.

That's not how I read the diagram, though. It appears to show the two halves connected together immediately after the fuses, jointly supplying all the loads. Ailsa's probably right that it used to be two banks which a previous owner has sort-of joined.

Pete

 

[Iceblink]

Pete.. agree your suggestion seems the best option. Good article on the smartguage site thanks.. the other options they describe look a bit complicated for only marginal extra benefit. I thought I'd post this up and see what people thought in case there was something I'd missed..

 

[skipmac]

That's not how I read the diagram, though. It appears to show the two halves connected together immediately after the fuses, jointly supplying all the loads. Ailsa's probably right that it used to be two banks which a previous owner has sort-of joined.

Pete

That's how it appears to me as well. The diagram doesn't show the where the charging is connected, I assume at the common + output after the fuses. If so, since it's already wired this way I don't see any reason to change it except as one post noted, one fuse could be blown and the boat running on just one battery bank and it wouldn't be obvious to the boater. It would however give a little redundancy if one fuse blows the systems would keep running.

Just need to check both fuses on a regular basis or rig some kind of indicator.