Wiring a 24v battery bank?

[DHutch]

Thoughts comments on the two layouts below?

 

I am reading a guide on the best way to wire up batteries and it shows both methods, but without an explanation of which is better or why. Dotted line in the first layout added by yours truly....

 

 

Link to guide; http://www.batterytender.com/Connecting-Chargers/

 

 

Daniel

[WotEver]

Fig 11 complete with dotted link plus another dotted link the other way if you really want to do best practise.

 

But... tbh it's unlikely that it'll make much difference.

 

Tony

[David Mack]

Either looks good to me. The first uses series links to give you 2 24 volt batteries, which are then wired in diagonal fashion. The second wires pairs of 12V batteries in diagonal fashion, and then puts them in series to get 24V. I wouldn't add the dotted diagonal link in the first layout - it destroys the symmetry (unless you add both diagonals as WotEver suggests - and that seems completely OTT).

Edited April 18, 2016 by David Mack

[DHutch]

Two links (diagonal other otherwise?) to make a full square in effect does seem overkill, if minimal in total cost compared to batteries. However, why is Fig13 any more symmetrical than Fig11 with link added?

 

What is the reason for showing Fig13? It seems to make little or no sense as while it is clearly balanced and works, it appears perverse for the links between A&B -ve and C&D +ve to be running perpendicular to the current flow rather than with it? Or is it just a method of linking them in the middle with three links rather than the full four, see question above?

 

The application is a fairly high-current one, hence I am keen to have the batteries working evenly when under full load, duty cycles are short but at times recharging may be left longer than ideal.

 

 

Daniel

[David Mack]

In Fig 11 without the diagonal link you just have 2 24V batteries in parallel. The links from A to C and B to D are effectively no different from the internal links between cells in each of the batteries. If you add the diagonal link then the connections between A and C and between B and D are a short link, between A and D a long link, but from B to C you have a long link and 2 short links. So different length (and resistance) connections between different 'top' and 'bottom' battery combinations, and hence unequal current flows, which are bad for battery life (according to Gibbo).

 

In Fig 13 the link is not really diagonal. Replace A and B by a single 12V battery and the same for C and D and that link becomes just a series link between 2 12V batteries to give 24V.

[ditchcrawler]

Or four 6 volt Trojans in series

[DHutch]

In Fig 11 without the diagonal link you just have 2 24V batteries in parallel. The links from A to C and B to D are effectively no different from the internal links between cells in each of the batteries. If you add the diagonal link then the connections between A and C and between B and D are a short link, between A and D a long link, but from B to C you have a long link and 2 short links. So different length (and resistance) connections between different 'top' and 'bottom' battery combinations, and hence unequal current flows, which are bad for battery life.

 

In Fig 13 the link is not really diagonal. Replace A and B by a single 12V battery and the same for C and D and that link becomes just a series link between 2 12V batteries to give 24V.

 

Yes ok, that works sorry. Hence if you wanted to put a centre tap in into Fig11 without removing the balance you would/could put either the two intermediate positives, or the two intermediate negatives, however I guess it serves little purpose and if anything omitting it allows an additional diagnostic option open to you, as you can then read the PD at the mid point to see if a cell has gone down.

 

In my mind that is the better option, unless anyone can produce a vaild a reason why you would choose to wire it as per Fig13, which needs one more wire making up?

 

I've removed the dotted diagonal link, and also added in diagrams of how it would actually end up laid out once installed.

 

 

The 'guide' also talk about using two 12v charger wired to the two halves, which if what you had was a twin-output 12v charger would be perfectly reasonable (assuming no links between the two outputs) I also see no significant advantage?

 

 

 

Or four 6 volt Trojans in series

 

For packaging reasons, four 12v batteries is the only really pragmatic way to do it.

 

 

Daniel