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Author Topic: Build battery 24v bank with exide l2v320 marathon  (Read 8263 times)
Eleanor
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« Reply #15 on: June 05, 2012, 12:55:23 PM »

I agree with Elanors first pic (it matches the right hand side of my pic).

But the second pic I have doubts about.

You have gone to all the effort & expense on having cables for each connector on each cell but on the take off end you have basically cut corners by using the short link.

There are two possibilities:-

1, that the terminals are internally connected in a balanced way in the cell so it does not matter which terminal you use.
(but then why have two terminals in the first place)

or

2, they are not balanced evenly & the external double cable are needed for balance.

In 1 you might as well just use extra thick single cables for all the interconnects in 2 you need matched cables at all points.

Justme, I knew you wouldn't like it that way! This is how it was supplied with a sketch of how to install it. I don't think there's a major issue with imbalance as internally the posts are connected to the same strap*(see Edit below after reading next sentence). I was told that the reason there are two positive posts and two negative posts is that they share the current in cells over a certain size and this is how all cells used to be before some manufacturers moved to a single post (I don't know which Museum this lot came from  hysteria).

When we add more PV so we have 4-5 kW I think we will double up on the take off cables so that everything runs in 2 x 50mm2 as it would be skimping a bit. I don't know if anyone in Forklift Truck Land has this type of cell and if this is the standard way of doing it?  Huh

*Edit : I keep thinking about this and when he said "cells over a certain size" I assumed he meant in terms of Amps but now I'm thinking from what you say he meant the physical size ie length of the terminal strap. We will add a second cable when the rest of the PV goes in. Can't be less than perfect can we ralph
« Last Edit: June 05, 2012, 01:32:22 PM by Eleanor » Logged

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Justme
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« Reply #16 on: June 05, 2012, 02:13:27 PM »

The down side to using double cables you have to fuse each one individually for half the load or you could have one cable taking all the load.



In your 48v bank I would wire the top row to the third row & the second row to the forth row then the end cables will be the same size without having to make them both as long as the longest ones.
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« Reply #17 on: June 05, 2012, 10:05:10 PM »


Justme, I knew you wouldn't like it that way! This is how it was supplied with a sketch of how to install it. I don't think there's a major issue with imbalance as internally the posts are connected to the same strap*(see Edit below after reading next sentence). I was told that the reason there are two positive posts and two negative posts is that they share the current in cells over a certain size and this is how all cells used to be before some manufacturers moved to a single post (I don't know which Museum this lot came from  hysteria).

When we add more PV so we have 4-5 kW I think we will double up on the take off cables so that everything runs in 2 x 50mm2 as it would be skimping a bit. I don't know if anyone in Forklift Truck Land has this type of cell and if this is the standard way of doing it?  Huh

*Edit : I keep thinking about this and when he said "cells over a certain size" I assumed he meant in terms of Amps but now I'm thinking from what you say he meant the physical size ie length of the terminal strap. We will add a second cable when the rest of the PV goes in. Can't be less than perfect can we ralph

Hi Elenor,  It is down to the Amps.  They use two of them to bolster the current capacity and distribute the heat produced more evenly (so each side of the plate gets the same heat).  It also allows you to accidentally strip one thread (in soft lead terminals) and have a redundant connection.  My 400Ah cells came with single M12 terminals per cell terminal.  But the bigger 700 and 1000Ah cells have multiple M12 threads per terminal.  But then those cells can put out 3000A continuous.
 
Part of the move to single terminals is cost reduction and the fact that on traction packs they are moving to welded (or soldered) connections to reduce variations in contact resistance and corrosion issues on the links.

@fc  These Exide Marathons are classed as "telecoms / emergency standby" cells.  The "L" range is for Long term storage.  They were kept on float continuously with a view to only being used for emergency discharge.  In daily cyclic use they'll last about 350 cycles at 50% DoD to 80% of original capacity. 

I had some similar Marathon FT 104Ah 12V blocks.  I was using six in series-parallel (3x2) for 24V and that lot in parallel with some 180Ah Deka gel 6V blocks. I deliberately wired the Marathons so that the Deka cells did all the hard work and the Marathons were only called on as "backup".  The Deka blocks went for about 850 cycles before going high impedance (although not gassing).  The Marathons sort of made it to 630 cycles but a couple went high impedance and started gassing and wouldn't take or give much power in the end (probably well below 50% remaining capacity).

Wasn't an issue as I picked them up for 50 each but the gassing at the end of life was.  The gel ones performance went off but they remained air tight.

Try to keep discharge well below 50% to maximise the life of these Marathon cells. 30% would give you 4.6kWh usable per day.  Either that or accept that they are a short term solution (maybe 18-24 months).

Although I'd always advocate using cells only in a single series string, 24 cells in series for 48V means any failed cell will put your bank out of business.  Going 24V with two parallel strings at least gives you some redundancy if you have to drop down to one string and cannibalise the other string for spares.

The other thing about the Marathons is they really don't like high Voltage charging.  The FT104s would start to vent at anything over 14.0V (2.33Vpc at 25C).  They're pretty much only designed to float recharge over a 12-24 hour period.  I did run mine at an absorption rate of 2.325Vpc for a couple of hours and then float at 2.275Vpc.  Happily that suited the gel cells as well.  The L series data charts tell a similar story.  Absolute max charging Voltage is 2.275Vpc at 25C continuous float mode.

http://www.battery.co.za/download/dl/MarathonL_t_e.pdf
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fc
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« Reply #18 on: June 05, 2012, 11:28:15 PM »


Hi guys my dream is over Sad  
Today I connected 24v package and connected a very small inverter to the pack ..
Before I measured all of them and each cell had 2.14v and total of pack 25.6v pretty nice ..
Surprise as soon as I powered the inverter voltage drop to 24v..
As soon as I connected the load 400w drill voltage dropped in 10 seg to 16v yes 16v...
Inverter stopped automatically and voltage back to 25 Sad
The I connected a charger very small for the ah, but after 10min voltage at 28v and charger telling me that they are 100% Sad
So I think I had bring home half a ton of trash ....
What do you think ?
Now I have carrier all that trash to residues company Sad 



What do you recommend for buying new 2v modules  ? 

Thanks for all your inputs 
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Iain
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« Reply #19 on: June 06, 2012, 07:47:35 AM »

Hi
Might be worth trying to find if you have a couple of duff cells. Try picking the best of the cells to make a 24V bank. We used to check for duff cells by putting a medium load on the bank and then measuring the voltage on each cell. I used to use a 12v 100w Halogen bulb just to get a bit of current flowing. Any duff cell will have a very different voltage to the others. With the 12v bulb just test in 12v banks. Any obvious defective cells, remove. There is a possibility you might have enough cells for 24v to test the system  until you source new batteries. Or if you have time whilst your inverter is on check each cell voltage(with current flowing) should all read similar. Worth a try. Try after a recharge as well.
Iain
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fc
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« Reply #20 on: June 06, 2012, 12:11:49 PM »

hi will do that later today to see if i can at least do a 24v bank. but 'm still deciding as i will a lot of work to rearrange all the physical space and maybe only for few months

@Outtasight that "gassing" worries me because i have very small and closed space to have the bats,  but i have plans to build a h2 sensor that will trigger a fan to extract air in case of h2 concentration increases.. but even so these marathon are different from yours... btw how do you the verify that they  are gassing  ?
 
what do you think of these bats  exide 3EPZV-BS255  ? i have good offer for a kit that is supposed to be to a forklift machine

regards
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DaveSnafu
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« Reply #21 on: June 06, 2012, 12:20:47 PM »

A set of used forklift cells will give you the best long term solution and best value.
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fc
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« Reply #22 on: June 07, 2012, 12:53:32 AM »

Hi guys , good news .. That think that all these batts are bad didn't fit my head neither my wallet Wink 
Today i bring home a 30amps charger and  put it to charge...
Star measure all batts and all seem ok +- 2.35v charging but hi had all bats with the 2 posts connected except the corner where. I had only one post connected. I decided to measure all bats one by one and both posts ....
bingo...one of the bats in the corner on post measured 2.35 but other 1.2v  and that was the post not connected so I turn off the charger and reconnect the corner on the post with 1.2v and "caaaasbunmm " big spark on that batt...
So I turned off all again put a new cel on that position and voila my 24v bank with inverter and 400w load working fine...
Now I have some cells with slight difference on load. 2.13 2.10 and 2 at 2.2v .. So this means I need to equalize, right ?

Even if they all do 600 cycles will be ok until I can buy the forklift opz..
I now need to find a good charger that allow me to equalize them all ...
We have a saying here that translated is +/-  " the needs makes you find the solutions" 
 
Regards ..
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fc
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« Reply #23 on: June 08, 2012, 10:36:22 AM »

Hi there, yesterday was day dedicated to battery testing...
Some strange results i connected in 12v strings so i can use charger i have in 12v mode (more amps) .

Before i connected the charger all 6 bats measures between 2.12 and 2.16, after few minutes of charging some of the cells are at 2.35 , 2.40 , but a few got up to 2.5v and even  2.6v  .
What does this mean that this cells the go up to 2.6 are dead, broken ?  or they are full charged and the other ones are not ?

Can i charge a each cell individual, at what voltage ?

The cells have a sticker that says  "320Aah  C10 (1.8V/cell at 20C) | Nominal Float Voltage 2.27v at 20C)

I'm thinking on charge each cell individual so i can bring them all to a 100% charge, for that i have a small  charger that i use for charge lipo bats, but also have  program for LeadAcid bat where i can set the current and voltage..

this the charger that i can fix the voltage and the amps output :



will this be ok to charge a single cell? what voltage should i set the charger 2.35v ?

regards
« Last Edit: June 08, 2012, 11:16:07 AM by fc » Logged
Outtasight
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« Reply #24 on: June 09, 2012, 01:52:51 AM »

It can mean that the cells are somewhat out of balance (with some lower state of charge than others).  The low ones read low voltage under charge and the 2.6V ones are being over charged as they were "full".

Continuing to charge the full ones any more will seriously damage them.  Charging any AGM cell to 2.6V will risk thermal run away and a fire!  At the very least it will dry out the limited electrolyte in the cell and kill it.  As for how to tell when they are gassing... In my case it was not with a sensor but I could hear the valves making farting noises and general bad intestinal gurgling noises.  Gel and AGM cells shouldn't really make any noises at all as the gas is recombined as it forms between the plates.  It also made a stink and made me feel nauseous.  There are some nasty side reactions that can make quite poisonous gas as well as the plain explosive stuff.

Of course the ones that are reading as "full" could just be old and have reduced capacity. If they are all nominally 320Ah but some are old and tired and only hold 250Ah, then they will get to be "full" much quicker than others that can hold say 290Ah.

It would be definitely best to initially charge them individually with your charger in the photo.  If you can set it to 2.35V at 20C and charge each cell for 8-12 hours or until the current is less than 2A, that will be as much as they can absorb.  Then when you've done all of them individually, you can connect them in series again.  You could charge at the recommended 2.27V at 20C but it would take over 24 hours to reach anything like full charge.  If it's warm where you are then adjust the charge Voltage accordingly (-5mV per increase in degree C).  So 2.35V at 20C and 2.30V at 25C.

If the cells had been in storage for a long time they will have discharged at a rate of about 3-4% per month if kept cool (less than 20C).  They need a long charge like above to revive them from their sleep.  If they'd been stored for more than 12 months then some permanent loss of capacity may have resulted from prolonged partial discharge.

The exide 3EPZV-BS255 cells look good.  They are full traction cyclic gel cells.  Suitable for confined space without special ventilation (fans or the like).  They are rated for 1200 cycles to 60% DoD.  Old ones can have quite high impedance (means they hold charge capacity but can't charge or discharge quickly).  Cells that have become high impedance are no good for high power use (in fork lifts) but can usefully be used in low power off-grid applications for some time (as the Amp requirements are generally lower).  They aren't very big though... 255Ah when new would be fine for a 48V bank but a bit on the small side for a 24V one.
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fc
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« Reply #25 on: June 09, 2012, 11:12:20 AM »

Thanks I will try to charge each cell individual bu this small charger can only charge at 5amps
So 64C will take ages but I will try.

Even doing this later when all are connected and being charged in series the problem will return ..
Some of them ( if they have less capacity) will end up charging to higher voltage then the others .. Right ?
« Last Edit: June 09, 2012, 02:08:05 PM by fc » Logged
fc
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« Reply #26 on: June 20, 2012, 12:38:21 AM »

hi there just give some feedback...from all the 26 bats i had 2 were completely broken... 1 already explained the other had a big hole on the bottom, maybe fall and broke and when in charging i think some liquid started to go out of that hole ... maybe that or maybe some water got in the garage.. nevertheless its out of the game because is physically  broken..

so from the other i got 3 pack of 12v  (6*3 cells)  good ones at least they went well in my discharge test, taking 200w load during 12 hours  they kept their voltage at 2.05v 2.06
the other six that where mixed with these ones after that 12h got between 1.55v and 1.89v (that's why i stopped my test) when i saw this ones at so lower voltage...
so i recharged all of them in 12v and then finish all one by one with my 2v charger...  i now have 12v pack with "not so good ones" that may use or not ...

if i go with 2x24v banks maybe i can create one bank with 12 good cels and the other with 6 good cells and 6 not so good ... or should i stay with 1 24v bank and keep the others on float to have for backup if one the working banks fails.......... have to decide...

thank you all for you input and feedback.








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