Adding batterys to a 24 volt bank

[coventrylad]

Hello folks, I am getting confussed again. At present I have managed to wire up four, 12volt 110amp hour batterys in series/parrell to give me a total of 220 amph at 24 volt. But I would like to add another four batterys so total of eight batterys. My problem is where they are to be located they have to be all in a line(this is where it is getting me ) Please bear with me here and I will try to describe ! they need to be side by side i.e all the poss facing me and all the negs further away from me, wish i could do a drawing ! I have searched every where for a diagram in this configuration but can not find one, I have even tried to copy diagrams using peices of would with string on to try to copy the wiring but just end up with string evry where ! could some one please please give me a link or poss a diagram. I can also see it getting a bit crowed at the +/- terminals where the alternater, inverter and dc fuse box are fed from. Thank you all

Edited May 13, 2013 by coventrylad

[Scholar Gypsy]

Does this help. I think version 2 would be better, though there is not a lot of difference.

[coventrylad]

Yep thats how they are wired at the moment thank you very much, But how to add another 4 ! thank you once again.

[Shropshirecoal]

Rewire your original set in parallel, wire your new set in parellel and join the two banks in series.

Edited May 13, 2013 by Shropshirecoal

[coventrylad]

Ha Ha sounds so simple when put like that, any chance of a diagram fella please. thank you.

[Shropshirecoal]

A little difficult to explain and i cant upload a picture from my tablet but i hope you can make sense of this. In bank 'A' wire all the positives together and also all of the negatives together, that gives you a bank of batteries that now have the same voltage but the capacity of the combined batteries. Do the same with bank 'B'. Then take the positive from bank 'A' and connect to the negative on bank 'B'. The negative from bank 'A' and positive on bank 'B' will be your 24v feed. Please be careful, batteries can explode if wired incorrectly.

[coventrylad]

Thank you once again, yes I understand wiring each bank (A and B )in parraell to get "two large 12volt banks " the bit I am strugling with is when I come to wire them in series, which poss and neg to use to to get 24 volts. once again thank you for the time and effort you have given me

Edited May 13, 2013 by coventrylad

[steelaway]

Thank you once again, yes I understand wiring each bank (A and B )in parraell to get "two large 12volt banks " the bit I am strugling with is when I come to wire them in series, which poss and neg to use to to get 24 volts. once again thank you for the time and effort you have given me

 

My suggestion - I hope (think) I'm right?

 

Alex

 

Edited May 13, 2013 by steelaway

[Scholar Gypsy]

Steelaway

 

Sorry, your diagram is dangerously wrong - you have connected the positive and negative terminals of all the batteries together, so you would get a short and a loud bang.

 

I think this is what the OP was after. (sorry I can't work out how to embed pictures yet ...).

Edited May 14, 2013 by Scholar Gypsy

[coventrylad]

Brilliant you have cracked it thanks a million ! oh your up early !

[Shropshirecoal]

Yes thats the one, sorry, i cant do pictures on this tablet.

[smileypete]

Would help a lot if the OP could do a sketch of the physical layout of the batts in the engine room.

 

cheers, Pete.

~smpt~

Edited May 14, 2013 by smileypete

[Scholar Gypsy]

Sorry, I have reread the existing posting. I don't think there is any need to adjust the wiring on your current batteries - the bottom half of this diagram.

 

You just need to add the four new batteries, the top half of the diagram, in the new location, and then connect them in parallel with the existing battery set.

[coventrylad]

Thank you Scholar Gypsy once again. Your diagrams are really helpfull. One last question I promice ! if all eight batterys were in a line i.e neg nearest to me and poss furthest away would I still use the latest of your drawings ? cheers.

[Scholar Gypsy]

Well you could, but this would I think be easier to get right (and just as important to remember what you have done when you come to replace the batteries).

 

Next task, I suspect, is to find a large weight to put on the other side of the boat to get the trim right!

[bottle]

and remove some ballast from under the floor.

 

When I replaced my batteries with the same number but of heavier duty and weight I had to remove 12 paving slabs from under the bedroom floor.

 

Strange but sideways trim was OK.

[smileypete]

If the batt bank spends much of it's time on a shoreline I'd also consider connecting it like this (scuse the rough sketch...)

 

That way if one of the 48 batt cells develops a short, the pair of batts where the faulty cell is will be getting full charge voltage over 11 out of 12 cells which isn't so bad.

 

Normally with 12V setups, if a cell develops a short the batt gets full charge voltage over 5 out of 6 cells which can cause batt overheating and even affect the other batts.

 

Another nice perk for 24V

 

cheers, Pete.

~smpt~

Edited May 15, 2013 by smileypete

[davey b]

It is quite clearly explained http://smartgauge.co.uk/batt_con.html which I think is Gibbo's site - generally good for electrical stuff.

[Alastair]

Your batteries should be the same capacity and you need to keep a close eye on each cell.

 

If you have one failed cell in one battery then your charging system may stress and damage the others.

 

Pete's diagram has kind of covered this. Nice setup

Edited May 16, 2013 by Alastair

[Scholar Gypsy]

The smartguage article is fascinating, and really surprising!

 

I've checked the maths (rather easier using the matrix inversion function in Excel!). The key ratio in this calculation is M = (internal resistance)/(link resistance). In the example quoted M = 0.02/0.0015 = 13.3, and then the current split is indeed as quoted (see below).

 

17.7% 20.4% 26.1% 35.8%

 

 

One has to increase M to a rather implausible 75 to get the percentages in the band 23% to 27%.

 

So, taking all these posts together, my final proposal is here. This will achieve balanced loadings on each of the four pairs of batteries. It will also handle a failure of a single cell best, for the reason noted in an earlier post.

 

If anyone wants to play with my Excel spreadsheet repeating the results in the smartgauge article, it is here.

 

The OP may prefer to buy a generator instead??

 

I promise not to post any more on this.

Edited May 16, 2013 by Scholar Gypsy

[smileypete]

Or split thing the whole lot into two 24V banks of 4 batts each, connect each bank to the batt isolator and the hull common bonding point with equal length cables.

 

Also out of the four old batts, maybe even try find the better two using a hydrometer if poss and pair them together, and then pair the remaining less good two together.

 

Came across some 25mm² grey trirated cable today on Ebay, might be good for the links between pairs of batts in series on a 24V bank:

 

http://www.ebay.co.uk/itm/25mm-sq-TriRated-Cable-BS6231-Tri-rated-Singles-Panel-Wire-105degree-Tri-Rated-/181002357334

 

cheers, Pete.

~smpt~

Edited May 16, 2013 by smileypete

[coventrylad]

Thank you all so much, I really appreaicate all the time and effort. I am going to stick with post 15 diagram !! Gypsys latest looks tooo completed, and by the time I have connected Inverter, 24volt alternater and feed to dc consumer unit there would be six cables off the neg/poss feed! Oh I do have a jenny, cable I have been using for the batts, alternator, invertor and feed to dc consumer is this

150906249533 off ebay, sorry can not do a link.£10 a metre, over the top I know but big is best ! thank you all again.

[nb Innisfree]

Edited

Edited May 19, 2013 by nb Innisfree