battery bank configuration question

davo · February 2015

Hello all, I have a very limited battery bank space approx 40cm x 48cm x 150cm tall. I want to make a 24v system up of 2v forklift batteries I can fit 6x batteries in the space to make 12v and can weld a shelf up directly above the batteries to put another 6 and then link up both to make 24v, the 2v cells are 55cm in height so it would mean a long link between the top 12v and bottom 12v.will this work?how much power is lost by having a long link between the two 12v battery banks? Hope this makes sense,I have been told in the past links should be short as possible,interested to know your thoughts.thanks in advance!

BB. · February 2015

When working with fork lift cells... See if they need to be in a full metal case/jacket or not. Many of these types of cells expect to be in a metal box for structural support.

And do you have a way of moving the batteries without breaking your back? Depending on the size of the cells/12 volt block, you may need an overheat crane, pallet jack on concrete floor or something to move them around.

We are very careful about wiring when paralleling strings (i.e., 2x 12 volt packs wired together in parallel for a larger AH 12 volt pack). Wiring length is not as big of issue for a single series string.

There, we are looking for low voltage drop so that you don't waste energy heating the wiring and/or have so much voltage drop that A) the inverter cuts out under heavy loads/discharged battery and

the charge controller has an accurate voltage measurement when charging the battery bank.

So--What is the planned inverter current (24 volt?). What is the total length of wire run (one way or round trip distance)? And what will be your charging source (solar charge controller, inverter or backup AC charger, wire length, amount of charging current from each source, etc.).

Working with "real numbers" for your application should be less frustrating than doing a "theoretical discussion".

-Bill

davo · February 2015

Inverter is 24v exactly 1metre from banks.battery banks are made up of 12 2v batteries in 2 lots of 6,links are 18cm between cells but to link the two together top and bottom to make 24v requires a long link approx 60cm. Solar array thru mppt charges bank. What I need to know is this is it ok to have such a long link between the top set of 12v and the bottom.thanks

davo · February 2015

Cells are in metal casing I can move them no problems.

BB. · February 2015

Should not be a problem.

Of course, you have to design the wiring to carry the current you need... With about 1.0 volt drop maximum from battery wiring all the way to the inverter.

And you should look at ~0.1 to 0.2 volt drop maximum from Charge controller to battery bank (my personal recommendation).

As long as your wire is heavy enough to carry the current with the above maximum voltage drop, it should be fine.

Of course, you need the copper cable heavy enough to pass the maximum required current. And you should have fuses/breakers between the Battery common point (bus bar, battery cable ends, etc.) to each branch circuit (i.e., 100 amps for DC inverter, 60 amps for charge controller, etc. or whatever your application requires).

-Bill

Blackcherry04 · February 2015

Don't make them hard to Check the electrolyte level in or put water in. Most Forklift have a very limited reserve capacity, some as little as a 1/2 inch and they use a lot of water. I have a set of Surrettes that have about 8" above them and it's a real job to deal with them.

davo · February 2015

Great advice,thanks to both of you,height is the one measurement I have so I will make sure there is space between for watering,thanks again for the advice

battery bank configuration question

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