Author Topic: 24v & 72 v batteries  (Read 1644 times)

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bobanne

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24v & 72 v batteries
« on: June 27, 2005, 10:12:43 AM »
Hi all, last week i posted that i came across a couple of forklift batteries, one was 24volt and the other 72 volt that i was hoping i could use in my solar/wind off grid system. Well i looked at them today and they are all made up of 2 volt cells! So that gives me 48 x 2volt cells, i think i will wire them up in 4 strings of 24 volt banks. Each cell in both batteries is rated at 413ah over a 5 hour period. Now does that give me 4 banks at 413 ah at 24 volts each ? If so i would have approx 1650 ah all up i think. I also have a heap of T105s 2 volters and 4 x 12 volt trojans that i will use as backups. Also is there an inverter that can take 4 banks of batteries or is this a specialist wiring problem ?


Bob

« Last Edit: June 27, 2005, 10:12:43 AM by (unknown) »

richhagen

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Re: 24v & 72 v batteries
« Reply #1 on: June 27, 2005, 07:22:42 AM »
That is going to be a nice battery bank.  If you were to wire them all up in series you would have 413Ah at 96V, If you were to wire up two strings of 24, then you would have 826Ah at 48V, If you were to wire them up as you suggested as 4 strings of 24V, then you would have 1652Ah at 24V, or you could wire up 8 strings of 12 volt and have 3304Ah at 12V.   I would recommend a higher voltage unless you enjoy buying and running really thick cables.  On a bank this size be very careful with your connections, and fusing.  You have a huge amount of potential energy there.  If the conditions of the cells are all similar, then you could parallel your strings.  I would fuse each series string individually in case of a problem with a bad cell down the road, and also have a fuse near the batteries where the strings are connected in parallel to limit overall power into and out of the batteries.  Others here might have more ideas or insight as to fault protection for a bank of your size.  Keep in mind that batteries have internal losses, and the larger your battery bank, the larger those losses.  Forklift batteries are made to take a bit more abuse over their lifetime, but at a cost of a generally higher self discharge rate.  Like all batteries, they will last longer if you don't abuse them by repeatedly deep discharging them or constantly overcharging them.  Wow, I would love to have an 826Ah bank at 48V of Forklift batteries.  At 20% depth of discharge that is 7.8Kwh of energy.  Even if there capacity is reduced somewhat, providing I could keep them charged during the day, that's still enough power to supply my residence AS IT IS NOW on the grid.  I'm not that bad, but with additional conservation measures, I could do a lot with a bank like that.  Rich
« Last Edit: June 27, 2005, 07:22:42 AM by richhagen »
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RobD

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Re: 24v & 72 v batteries
« Reply #2 on: June 27, 2005, 07:24:40 AM »
The inverter doesn't care how many banks of batteries you have, only that the voltage is correct into it.


It's not a good idea to mix the 105's and the other batteries.


One more thing, remember the greater your battery capacity the more solar cells or wind power you will need.

« Last Edit: June 27, 2005, 07:24:40 AM by RobD »

wpowokal

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Re: 24v & 72 v batteries
« Reply #3 on: June 28, 2005, 07:52:36 AM »
I posted last time on this, it is my belief that one can be too perdantic with batteries. I know all the guidelines but, my bank is 8x650A/h and one 650 A/h total 5760 A/h.


Now all banks are seperatly and conservitavly fused on positive and negative ends, there is a reason for this.


I know from measurements that all banks don't equally share the load but so what.


The bigest disadvantage in a bank of batteries that is too large is greater maitenance. And always remember every amp taken out has to be repaid with interest.


Internal resistance in my opinion is a function of amps through each bank. Self discharge is another thing, though in my opinion small.


allan down under

« Last Edit: June 28, 2005, 07:52:36 AM by wpowokal »
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