Is this correct?

[Rasman]

http://oi55.tinypic.com/34g4oky.jpg

Would they discharge disproportionally?

[vascop]

Looks right to me - two above are in parallel and two below are in parallel, so each combination giving 24v and then these 2 combinations are wired in series and so result is 24v+24v=48v and each battery has a charge of 9Ah so all 4 give 4 x 9Ah=36 Ah.

[Rasman]

Thanks vascop

[mjd]

Not quite correct I think. The combination as shown will provide 18 Ah.

[Rasman]

Now I'm confused
I wasn't sure about going from parallel to series if I'd get the full 36Ah

[mjd]

If you connect two identical 24v 9 AH batteries in series you get a battery combination that will provide a voltage of 24v and a charge of 18 Ah.

If you connect the same two batteries in series you will get a combination providing a voltage of 48v and a charge of 9 Ah.

[Jemisa]

What a complicated world you live in, my brain hurts just looking at it.

jem

[Rasman]

>>If you connect two identical 24v 9 AH batteries in series you get a battery combination that will provide a voltage of 24v and a charge of 18 Ah.<<
you mean parallel?

>>If you connect the same two batteries in series you will get a combination providing a voltage of 48v and a charge of 9 Ah.

So what happens with the combination shown?
two pairs in parallel connected in series, 36Ah?

[Rasman]

Funk it, I'm going for it, it looks right to me as well vascop.

[mjd]

My apologies in the first paragraph I did mean parallel.

The combination that you show will provide you with a 18 Ah 48v battery.

It's connecting batteries in series that limits the Ah rating to that of a single battery.

[gen2]

Batteries in series :- add their voltages
Batteries in parallel:- add their capacities (Ah)

The set-up shown therefore produces 48 volts 18Ah (NOT the 36Ah shown on your diagram)

[vascop]

Yes, sorry for my error. Having reconsidered I agree with 48V and 18Ah.

[Rasman]

No problem.

What about this then:

http://oi55.tinypic.com/34g7ktz.jpg

That'll work yes or no?

If not why not and how on earth do you wire up 4 24v9Ah cells to give 48v36Ah?

[chakka35]

You can't, because to get 36Ah you would have to connect all four batteries in parallel, leaving the voltage at 24v.

Each battery can work at 24x9 watts for one hour, which equals 864 watts for all four.

But 48x36 comes to 1728 watts! Can't be done.

[mjd]

No that won't work, all batteries are now in parallel giving you 24v 36 Ah. You need twice as many batteries to get to 48 Ah.

[Rasman]

mjd, LOL are you deliberately trying to mess my head up? :)

chakka35, seems so obvious now, I feel stooopid. Time for a rethink. (I'm surprised no one picked up on that earlier) Thanks chakka

[wildwood]

Don't know if they're available but can't you get a stepdown transformer from 96v to 48v and connect the 4 batteries in series.

[gen2]

Wildwood, that wouldn't help at all since you would still not have 36 Ah.

As I said in my earlier post:

Batteries in series :- add their voltages
Batteries in parallel:- add their capacities (Ah)

[wildwood]

I am sure these people will sell you 1 or 2) batteries.

http://www.zippe.co.uk/#/buy/4530077582

[jomifl]

It is effectively a pair of 18 ah 24v batteries connected in series, so you get 18 ah at 48 v The ah stays the same when you connect them in series but the watt hours are doubled.

[Rasman]

wildwood, that's a fantastic link, to discover that team of professional engineers arrived at the same conclusion I did regarding battery output is extremely encouraging.

jomifl, I was right all along then?
It will extend the range of my Ebike after all.

many thanks to all that answered.