48v battery advice

Thommo

I really hope that someone can help me with my 48v battery system.
I have 24 cells Sunlight Batteries (Greek manufacturer) model 7OPzS490 - 48v nominal (490a/h). The battery supports a Xantrex SW3048E Inverter Charger
For some time now I have felt that the system is underperforming and that the battery is not holding much charge.
A friend (in the battery industry) has asked me to document the individual cell voltages every day, which I have just started to do.
To my horror, one of the cells actually reads -0.40v !
If the cell has gone bad, I'm sure that this is the cause of the poor system performance
Any comments anyone
Regards
Thommo

inetdog

Re: 48v battery advice

Thommo wrote: »

To my horror, one of the cells actually reads -0.40v !
If the cell has gone bad, I'm sure that this is the cause of the poor system performance
Any comments anyone
Regards
Thommo

The bad cell is almost certainly toasted beyond repair. In a series string of batteries, if one cell has a lot less capacity than the others, normal use can, for example, drain 20 % of the charge from all of the other cells. But because its capacity is only 1/5 of what it should be, that cell will be 100% discharged after the same length of time. If you keep drawing current from the battery, that cell gets charged in the reverse direction, leading to the -.40 volts you measure. The internal resistance will also go up drastically, causing the voltage of the bank under load to drop to the point where your low voltage cut off will activate before the rest of the cells are discharged very much.
An equalization charge, or removing that cell from the bank and charging it separately (assuming you can find a 2 volt charger) might restore some of its capacity. But seriously, the only reasonable action would be to replace that cell. If you replace that cell with a new one, you should try to make sure that the new cell and the old bank are both fully charged before you connect the new cell in. (As determined by specific gravity and voltage.)

Thommo

Re: 48v battery advice

Hey Inetdog,
Many thanks for the tech info on my battery problem - I didnt know the math (as you obviously do) but having sold UPS systems in another lifetime suspected that the problem was as you described.
The major problem for me is that I live in the South of Spain (I guess that we have common weather and climate seeing as you live in California!) and the people who sold us the Solar system and also installed it - well....they just dont do after sales service and didnt even mention maintenance or fault diagnosis.
Good advice - thanks very much for the speedy reply.
I'll let you know when I get it fixed.....hopefully.....
Best Regards
Thommo

niel

Re: 48v battery advice

with that cell reversed in polarity there was a strain put onto the other cells and i have no doubt they all were drained down too far in the first place which allowed the strain to reverse the polarity on that cell. in other words, the deep discharge strained all of the cells until one of them reversed which put a further strain on them all. there's a good chance of further failures to come even if you replace the bad cell.

Vic

Re: 48v battery advice

Hi Thommo,

As has been said cell reversal is usually very bad for that cell. niel noted that it could be from the entire bank having been run down too far, although is could have been just a single poor cell to begin with ...

In looking around on the Net, it appears that this is a VRLA battery, quite possibly a Gelled electrolyte (?). Since this system was installed by others, perhaps you could tell us more about your system details, your useage, and a link to the data for your exact battery. It appears that several companies may make a battery with this part number -- assume that you are off-grid.

What are your daily loads, amount of PV and other charging sources, Charge Controllers, and so fourth.

Are the Chargers set to the battery manufacturer's recommended voltages? Does each charge source have a Battery Temperature Sensor? More data is helpful. Thanks, Vic

stephendv

Re: 48v battery advice

Hi Thommo,

Coincidentally I have a 48V battery from the same manufacturer, except they're PzS forklift cells and not the OPzS you have. Bought them through the Spanish distributor up north: http://www.norwatt.es/en/
Don't know if your charge controller and inverter can support it, but if you could configure them to work with a 46V nominal battery you can continue as normal without downtime.

Thommo

Re: 48v battery advice

Hey Vic,

Well,......wow.....what a mountain of stuff that you have - just how big is your house anyway?;)
You'll have to give me a bit of time to correllate all of the links that you want - but

http://www.systems-sunlight.com/?contentid=51&langflag=_en

gets you to the page that has the info on the battery cells - the 7OPzS490 is in the block describing the two volt cells and if you click on the type number it brings up a PDF of the individual cell
Not a VRLA battery tho'.
Loads during the day are only 0.5a to 1.0a - the only time that we have larger loads is when we are cooking (between 5 and 15 amps usually) and using the washing machine or the microwave or the kettle.
Xantrex (the manufacturer of the inverter charger system have now been taken over by Schnieder Electric (also in California) and I started to have conversation (by email) about my problems with their helpdesk, but I stopped because, well, they just dont have the knowledge, y'know?
The thing that kicked all this of was that during the day things wetre fairly ok, but after dark when I put the genset on the charger would charge the batteries for about a minute, and then latch out.
Then, after another minute the charger would re-engage and charge again, for another few minutes.
All well and good but with a load on teh system, when the charger latched out that would leave the battery and the inverter carrying the load and for every cycle the mean battery voltage would get lower and lower. I then took to putting the genste on well before the time arrived when we had to cook our meals and usually by then the charger had charged the battry to the point where the system was son 'float'.
When the battery go to that stage it seemed to handle the loads ok and that was fine.

When I switched off the genset at say 20.00 in the evening, the voltage would read about 52v or so. We would then watch a couple of hours TV (the total load would be about 2.0a) and then retire for the night. The overnight load would be absolutely minimal, 0.5a or less.
In the morning I come out and the battery reads 46.4volts. This is what got my attention in the first place - a 460ah battery can't carry a 2 amp load for 2 hours without discharging down from 52 to 46 volts - please....!

Anyhow, I'll do some more link checks and get back to you as soon as I can - sorry for the delay in reply by the way - I've been rather caught up in trying to correct the problem before we have NO power at all.
Cheers man
Thommo

Blackcherry04

Re: 48v battery advice

Thommo, Try cutting the charger back on the Inverter. Start at 80% then raise it a little at a time. Mine will do that Latch on then off if I raise above 90% charge rate, so I leave it there and live with it. I don't know what causes it, I think is the internal Temperature of the inverter, it seems there is a sensor that causes it to do that or the high voltage runs up to high and it gets into some kind of loop with that on and off. There a huge difference in the battery voltage and the measured voltage in the inverter as it tries to ramp up to charge, Cutting it back is what worked for me.

Worth a try.

Thommo

Re: 48v battery advice

Blackcherry04, Thanks for that - I'll give it a whirl
Thommo

Vic

Re: 48v battery advice

Hi Tommo,

Thanks for the additional information.

Sorry that when I Searched for only the model number of your battery, happened to find a Gelled-electrolyte model.

Those batteries look very nice.

1. Hope that you have a Hydrometer (or perhaps a Refractometer) to actually measure the Specific Gravity of each cell of the battery bank. This is the essential way to know what the SGs really are. If you do not have a Hydrometer, please try to get one very soon, or perhaps borrow one from a neighbor, although it seems that the bank probably at a very low state of charge, and needs charging as soon as you possibly can do it, regardless of the individual SGs.

2. YES, you are correct regarding the need to focus on your problem with the battery bank. This is of utmost importance.

3. Regarding your SW Inverter/Charger's ability to charge the battery bank; As you probably know, there are several things that will cause this Charger to "lock out". To me, the main reasons are often with the Inverter's qualification of how appropriate the generator's voltage and frequencies are. The inverters in use here are fairly similar to yours. In the Advanced menu (IIRC), there is sub menu for the Charger voltage, current and frequency settings. Perhaps these settings are too critical for voltage or frequency to allow it to accept the generator's output. It is possible as blackcherry mentioned that the charger is demanding too much current from the genset, the genset's voltage or frequency fall out of the ranges set in the Charger menu. There are seveal settings in that same menu for the amount of current taken from the genset, and how much of that current is used to charge the batteries. These current settings are for AC Amps, and not DC amps going into the battery. For a 48 volt battery bank, the Battery charger AC settings will be about 50 % of the maximum current that will actually be available for battery charging.

4. When you do get the battery bank more fully charged, you will want to do an EQualization charge, to help equalize the SGs of each cell in the bank, but getting the SGs of the bank UP very, very soon is the most important.

There are those here who have your exact Inverter, and can advise about the actual menus for that inverter/charger. I will try to find the manual on-line.

More later, Good Luck, and please check in to keep us informed on how you are doing, and with any questions that might arise. More later, Thanks, Vic

Thommo

Re: 48v battery advice

Hey Vic, Thanks for posting your comments - I think fortunately that I have come across this problem at an early stage. Yesterday I got a Hydrometer and checked all the cells as soon as I got home and with the exception of the one cell that I think (or more correctly... I know) is toast, all the rest show an SG of between 1.24 and 1.28.
First thing in the morning I check the volts for all the cells and they show about 2.08vpc - the dud one shows about -0.48v.
By my reconing 24 x 2.08 = 49.92 - so when I get the new cell all aught to be well.......maybe....
I called the guy who originally supplied and installed my system, but he's unfortunately living in Galicia in the north of Spain now (we live in Almeria in the south) and he's also not in that business now - so no help there. He gave us the name of a guy that he used to get his battery cells from - we phoned him and he said he could get us a replacement 2v battery cell, model 7OPzS490, but not made by Sunlight (the original Greek manufacturer).
Is this model number 7OPzS490 some generic type - I feel rather skeptical about having a cell from some other company. What do you think about that? - Do you think that a cell made by a different manufacturer would be ok as long as the tech specs were the same?
If must also ask your advice on the rating of the alternator in the genset. When I read the manual supplied by Xantrex it clearly stated that in the settings for the Amps in the AC2 input (the genset input ) should be set at the max output (in amps) of the alternator on my genset (which is 26a). I went to the menu to alter that setting, if need be, and found that it had been previously set at 15a.
I reset the value to 25a and the system does seem to be functioning a little better for that change (battery probelms notwithstanding).
I know that ther is a difference between the amps (DC required by the battery and the AC amps supplied by the generator but isnt there some credo that says that the charge (or charger) should be rated at 10% (c/10) of the battery A/H capacity - that being so shouldnt I need around 50a for the battery charging? (whereas I only have 25a - to cope with both the load and the battery charging)
I know that you'll set me strait on that - sorry - I dont have the math for that!
Hopefully, within a week we will have bought another cell and it will have been installed and at that time I'll do an 'Equalise Charge' to synch up all the battery cells.
Do you have any recommedations at to what the max voltage the battery should be charged at for this 'Equalisation Charge'?
I have a feeling that the current value for this setting is a tad low - 57v or thereabouts.
Many thanks again for you help and advice - I look forward to your further comments, for which I am truly grateful, 'cos its really difficult here in Spain to have any kind of meaningful technical discussion about these things, because, well,.....their attitude here is........ 'well, if its working whats to worry about technical details'
I am NEVER going to fly in a Spanish built aircraft.........
I look forward to your further comments
Best Wishes
Peter Thomson (Thommo)

BB.

Re: 48v battery advice

Thommo wrote: »

Hey Vic, Thanks for posting your comments - I think fortunately that I have come across this problem at an early stage. Yesterday I got a Hydrometer and checked all the cells as soon as I got home and with the exception of the one cell that I think (or more correctly... I know) is toast, all the rest show an SG of between 1.24 and 1.28.
First thing in the morning I check the volts for all the cells and they show about 2.08vpc - the dud one shows about -0.48v.

You need to monitor the voltage (and specific gravity) per cell over time and under various conditions (under charge, load, and resting after 3 hours or more)... The only "accurate" method is to measure the voltage after 3+ hours of no charging/discharging current to estimate the state of charge (and ~25C/77F is the cell reference temperature).

By my reckoning 24 x 2.08 = 49.92 - so when I get the new cell all aught to be well.......maybe....

In the end, you want to get the cells to at least 90% State of Charge several times a week (minimum). You are not after 100% SOC every day--that would be a waste of generator fuel and a bit hard on the batteries.

I called the guy who originally supplied and installed my system, but he's unfortunately living in Galicia in the north of Spain now (we live in Almeria in the south) and he's also not in that business now - so no help there. He gave us the name of a guy that he used to get his battery cells from - we phoned him and he said he could get us a replacement 2v battery cell, model 7OPzS490, but not made by Sunlight (the original Greek manufacturer).
Is this model number 7OPzS490 some generic type - I feel rather skeptical about having a cell from some other company. What do you think about that? - Do you think that a cell made by a different manufacturer would be ok as long as the tech specs were the same?

You really have no other option (unless you can find a used cell in good condition).

If must also ask your advice on the rating of the alternator in the genset. When I read the manual supplied by Xantrex it clearly stated that in the settings for the Amps in the AC2 input (the genset input ) should be set at the max output (in amps) of the alternator on my genset (which is 26a). I went to the menu to alter that setting, if need be, and found that it had been previously set at 15a.
I reset the value to 25a and the system does seem to be functioning a little better for that change (battery problems notwithstanding).

You may have to back the maximum current down a few amps--Depends on how well your genset tolerates the maximum current (some are better than others).

I know that there is a difference between the amps (DC required by the battery and the AC amps supplied by the generator but isnt there some credo that says that the charge (or charger) should be rated at 10% (c/10) of the battery A/H capacity - that being so shouldnt I need around 50a for the battery charging? (whereas I only have 25a - to cope with both the load and the battery charging)

We use a 5% to 13% rule of thumb as a starting point. Read the manuals for your batteries and make sure you are within their recommendations too.

Below 5% gets questionable as batteries are cycled (and get older--when they have higher self discharge). If you charge only during the day and discharge only at night, 5% can work... If you use power during the day, then you are removing charging current available to the battery bank--So you have to watch your battery state of charge (and water usage) to make sure it is getting recharged properly.

Over 13% rate of charge--Batteries can over heat (probably more of an issue for fork lift operations where batteries are deeply cycled every day). Also, it becomes a bit of a "waste" of money as for the typical users, the battery banks reach full charge very quickly and the excess generator (or solar array) capacity is "unused" much of the time. 10% to 13% is a good "balance" for most people (we don't like to see very large battery banks relative to loads--that drives larger solar arrays and gensets--And too large of gensets can waste fuel much of the time when running at less than 50% of output capacity).

I know that you'll set me strait on that - sorry - I don't have the math for that!

So, how much power do you use every day (AH @ XX battery voltage; Watt*Hours or kWH per day, any peak loads like a well pump, etc.).

What is the kW rating of your genset (I assume at 230 VAC and 50 Hz)?

If you have a large enough genset, it would not hurt to get a second AC to DC battery charger (~25-35 amps) and connect that up. You can parallel battery chargers to the same battery bank (with proper wiring). And the extra AC battery charger should not be too expensive (relative to your battery bank costs).

Hopefully, within a week we will have bought another cell and it will have been installed and at that time I'll do an 'Equalize Charge' to synch up all the battery cells.

Yea--You need to do this--And it may take a lot of generator run time/fuel to get things working well again... More or less (another rule of thumb) you want to equalize if the cells are more than 0.015 to 0.030 SG difference between the high and low cells. Measure the SG of each cell every 30-60 minutes--and when all cells stop rising, stop the equalization charging. Log the temperature corrected SG for each cell--and that is your "new" 100% SOC for each cell.

Also, monitor the battery temperatures too... You don't want to exceed ~120F (~49C)--High temperatures are very hard on battery banks too (more or less, for every 10C rise over 25C, your battery ages 2x faster--If 20C rise, battery ages 4x faster, etc... Conversely, for every 10C drop, the battery will age 1/2 as fast).

Do you have any recommendations at to what the max voltage the battery should be charged at for this 'Equalization Charge'?

Does your battery mfg. have a recommendation? In general, you want the the maximum equalizing current in the 2.5 to 5% range (500 AH, 12.5 to 25 amp range). That may take 60 to 63 volts or so (many battery chargers may have difficulties reaching those high of voltages). Monitor the current flow--As batteries "get hot", their required charging voltage does fall (so you could start at 62 volts and need to fall back to ~60 volts as the bank heats up).

Equalization is "hard" on a battery bank, so you only want to do the minimum amount required. Then stop. During equalization, charging current is converted into hydrogen/oxygen gases and heat... So, they tend to get hotter faster at lower charging currents.

Also, monitor electrolyte levels... Never have exposed plates. But don't fill too high either--As gas forms inside and batteries heat up, the electrolyte levels will rise and can flood over the top of the battery pretty easily (fill low cells to only 1/3 or 1/2 levels when cold/before equalization--Add water at the end of the equalization charge--and again don't over fill).

Regarding water usage--If you have to add water every two months--You probably are OK. If you are hardly ever adding water (more than 6 months between fills), then you may be under charging (there are some low water usage batteries that use less water than "normal"). If you are adding water every month or every few weeks, then you may be over charging.

I have a feeling that the current value for this setting is a tad low - 57v or thereabouts.

Make sure your volt meter is accurate and you are measuring the voltages at the battery (not at the battery charger--wiring voltage drop can give you inaccurate readings during charging).

And, you probably would be better at 58-59 volts. During winter you may need to keep the voltages a bit higher to make use of all of your available sun... During summer (and when you are away on vacation) you can probably dial the charging voltage down a bit (temperature compensated charge controllers will do some of this automatically anyway as the battery banks get hot/cold during the seasons).

Good luck Peter.

-Bill

Vic

Re: 48v battery advice

Hi Peter,

Thanks for the added informatnion.

Agree that if it is at all possible that you MUST get a replacement cell from Sunlight, as it would have the best chance of matching the rest of the cells in your bank.

Please try contacting the company that the installer referred you to, and ask them what it would take for them to get a Sunlight cell as a replacement. It is fairly common, stateside, that single cells are a bit difficult to ship, especially when they have electrolyte in them. I would advise against getting the replacement cell as a Dry battery, as, often, dry batteries would need Activation. Although perhaps the dealer could do that. In the USA, it is fairly common for replacement cells to be shipped to a distributor/dealer along with other batteries. This can cause a significant delay.

It is quite possible that you could remove the bad cell from the string, and adjust the charger voltages down to a lower voltage -- subtract about 2.37 volts from the Absorption charge voltage (called Bulk in the SW Inverter), and reduce the Float voltage by 2.23. The inverter should run OK down to about 44 volts. It would loose some Surge power, but sounds like this should be OK. You will want to do the save voltage reduction for all other charge sources, like the Charge Controller. This has come up before, and N-1 cells can work OK, especially with 2V cells on 48 V systems -- Think that inetdog touched on perhaps removing the cell ... AND, when you do an EQ, also reduce that voltage as well (23 X the Vper cell recommended by Sunlight) should be fine.

Do you have a Battery Manual, or recommendations from Sunlight regarding Equalization votage settings?

If not you might contact them and ask them for this. Also, if the dealer/distributor is not helping you in the way you like, you might tell them of your situation, and ask them how you can get the new cell. Perhaps there might be some warranty coverage for the bad cell ... perhaps not.

Did not see that you noted the STC rating of your PVs. It is a pain to do EQ from a genset, but when EQing is necessary, it is much better to use the genset vs not EQing at all ... Some of your cells appear to have SG readings somewhat above those speced by Sunlight. This is often caused by lower electrolyte levels in those cells (water evaporates and acid does not, as you know), or sometimes this can happen if the bank has not been recently cycled below 85-ish % SOC. Cycling is good for Flooded batteries. BUT let's not talk about cycling the bank just now, as there might be some risk of over-discharging an additional cell.

Doing an EQ soon would be a good place to start, with info re EQ voltage, max current, and duration of this EQ from Sunlight. Please check electrolyte levels soon, and top up any cells with low eledtrolyte levels by adding good quality DIstilled water.

You have been in the battery business, so hope the above is not insulting your knowledge/intelligence.

Regarding the AC current settings in the SW Inverter, let me go get my SW+ Inverter manual. The menus are different, but should look at it. But yes, the genset needs to supply all of the AC loads that are on the inverter AC outputs. Sometimes to get a good charge or EQ in a reasonable amount of time, it is necessary to cut back on these loads and increase tha amount of generator power that can go to battery charging. More later. Good Luck, Vic

stephendv

Re: 48v battery advice

Thommo wrote: »

I know that ther is a difference between the amps (DC required by the battery and the AC amps supplied by the generator but isnt there some credo that says that the charge (or charger) should be rated at 10% (c/10) of the battery A/H capacity - that being so shouldnt I need around 50a for the battery charging? (whereas I only have 25a - to cope with both the load and the battery charging)

Hi Peter,

The 10% rate is a good rule of thumb and refers to the DC current going to the battery. The 25A you've set on the Xantrex is the AC current from the generator at 230V, so that's 5.5kW of power. This gets transformed in the charger to the 48 - 57V you need to charge the battery. 5500W / 57V = 96A. With 500Ah of battery you're charging at 20% rate, which is fine for OPzS cells.

EQ should be at about 2.6V per cell.

I hope the guys at Norwatt can help you with a replacement cell... but shipping might be too expensive to make this a practical option. I wanted an air-mixing system for my batts which is really just a set of pipes and a small pump, which cost about 200 euros and they wanted 300 euros for shipping and they weren't willing to post it.

If you can't get a cell from sunlight, I would do one of the following:

- Reprogram all the chargers and inverters to work off a 46V bank permanently and remove the faulty cell (only practical if you really can change all the voltajes especially low voltage cut off on inverter)

- Get a replacement cell from a different manufacturer with the same model number, Ah rating, electrolyte density and antimony doping. Most of what constitutes an OPzS cell is governed by DIN standards, but as far as I know manufacturers can use different plate chemistries. E.g. 7 OPzS 490 means there are 7 positive tubular plates with 490Ah capacity. Sunlight advertise less than 3% antimony doping. The only other variable is the electrolyte density, which they should be able to tell you. Better the number from the factory than the number you're measuring in the cells.

Thommo

Re: 48v battery advice

Hey Bill, Thanks for all of the details - I'll have to keep re reading what you wrote until I have it clear in my mind - its been a few years since I sold UPS sysytems for a living and I'm finding that I am re learning what I used to know by wrote. But, you knw how it is - if you speak another language - if you dont use it - you lose it!
Thanks for all the advice - very difficult to come by here in Spain - I'm sue we'll communicate again,
Best Regards
Peter Thomson (Thommo)

Vic

Re: 48v battery advice

stephen,

Thanks for the info that there is a DIN standard for this cell, could make it simpler, although as you note, there are still a number of variables. Agree about removing the bad cell. The SW inverter appears to spec a 44 V minimum battery Voltage for operation. This could be a bit of an issue with warm batteries that are discharged somewhat and a large peak load coming along. This should be OK as a short-term work around for the Winter. But the system would probably be much happier with a new Sunlight cell of the same spec (of course). But for a month or two, would bet that this should work OK.

I had wondered if the normal 2.6ish EQ voltage might be a bit high for these cells, which appear to have a bit of a low density SG electrolyte.

Peter, hope that you CAN get the new Sunlight cell that matches your bank. Removing the bad cell and resetting the charger voltage settings of the Inverter, lo-voltage disconnect V, and the V of the CCs (if possible), should allow you quite some time for a new cell from Sunlight to arrive. Hope this is an option.

stephendv has experience with this manufacturer, but the Forklift batteries run a higher SG electrolyte than your batteries (as I read it), so Sunlight's guidance on EQ, in particular would be important in my opinion.

Believe that I misstated the AC Charger Amps settings for your 48 V 230 VAC inverter. Was stuck thinking about my USA models, where the AC - DC conversion is; each AC Charger amp gets two DC amps at 48 V. In your case, would bet that you would need to set one quarter the AC Charger Amps for the desired DC charging current.

In looking on the net, looks like your inverter's DC charging current is 50 A DC continuous. This MIGHT correspond to a Charger AC Amps setting of 12-13 A AC, although am just guessing. This charging power appears to represent about 50% of the power output of your genset, so that appears to be a good balance between battery charging and ability to provide loads on the inverter while charging batts. Good Luck, and hope that your CCs have a wide range of charging voltage settings, should you decide to remove the bad cell. Vic

blindpew

Re: 48v battery advice

so happy to find this thread, been looking for a more technical answer to the same problem i am having. my system is much the same trace sw4845 with 1kw wind and 2.5kw solar and the faults you all describe are like for like, although the batterys i use are 12v three banks of four linked in series then parralell at 690ah. i have lost 4 out of the 12 due to cell failure at three years old, so now run at 460ah but this is going down also.

Thommo

Re: 48v battery advice

Hi again to Vic, Steven, Bill, BB, Blackcherry04, Niel and the cast of thousands (well…10 or so, that have also read my post!).
So……there I am on Monday (17th), after breakfast…..head in hands, wondering where I am going to get 450 Euros (about 650 bucks) for the replacement battery cell that I need to get from Sunlight batteries.
In my mind I had already written off this dud cell and was wondering what on earth I was going to do now. When I bought the system in 2007 the cells were only 150 Euros!!!! – how come they are some much more expensive now?
Anyhow, I also checked out some alternative cells (Exide) which are only about 75 bucks cheaper and dimensionally rather different including the connectors, which are M8, not M10.
Also, I might add, about 12 days ago I sent an email to Sunlight batteries in Greece – and guess what? – yep – no reply!
What is it with apathetic companies – you would think that in this day and age where business is getting harder and harder to come by that they would be all over any little enquiry that came their way – anyhow - I digress.
I went and sat in front of my ailing battery and decided to review what I knew. All the cells rated an SG of about 1.25/6 (for arguments sake) except for number 24 (which wouldn’t even move the indicator of the bottom of the tube!).
I put the Hydrometer into the cell, sucked up a few cc’s of electrolyte and dropped it on the concrete floor of the battery room – nothing…….
I took the vent off another cell, picked up a few cc’s from this other cell and dropped that on the floor – hissing and bubbling of acid meeting concrete.
It was then that I thought back to the installation. When they came to site to install the battery and other components, I remembered that one of the battery cells was broken and they substituted another (very different) cell for a week or so until the replacement arrived.
I am now of the opinion that when the replacement cell arrived that they just filled the cell with distilled water, installed it with the other cells and considered the job done. I can see no other explanation. I tested it – there was no acid in the cell at all.
Given that, I went and bought a few litre bottles of acid and siphoned out a litre of water and added a litre of acid.
Blow me down if the cell didn’t start picking up voltage after about half an hour and within six hours was up to 1.8v (positive volts!)
The same morning before I had done this….experiment…. the cell voltage was -0.46v and the battery voltage was 46.2 (in total) when I checked it at 06.30.
The following morning, after I had added the litre of acid, the battery voltage was 49.4!!!!!!!!!!!
I was just gobsmacked - in fact my gob had never been so smacked!
Needless to say, on Tuesday I siphoned out another litre of liquid and added another litre of acid.
Today (Wednesday 19th) I checked the battery, as usual – and - 49.6v and the number 24 cell is reading 1.96v (positive charge). By the by - all the other cells read 2.06v this morning.
I guess that I need to add about a litre more acid (it’s still not showing a good SG, although the indicator is lifting off the bottom now!). According to my research, an effective electrolyte is made up of 36% acid and 64% dist water and the cell in question takes 8.6l of electrolyte, so….3.09l of acid needed (or thereabouts)
At some point in time I will have to do an ‘Equalise’ charge to synch up all the cells (hopefully).
I am just staggered to think that my system and the battery have functioned for 5 years
(FIVE YEARS!!!) with, effectively, (electrically speaking) 23 cells!
And for it to now (apparently) reviving itself to working capacity is absolutely amazing! Don’t forget that I had already written off this cell, so the experiment was a kinda ‘Hail Mary’ shot.
Any thoughts anyone?????????

stephendv

Re: 48v battery advice

Well it looks like there's some kind of faint light at the end of the tunnel! I can't add anything to your recovery procedures, having never tried that myself, but since the cell was dead anyway you have nothing to lose. As long as you keep a close eye on it, measure SG every day and see how it's doing. Perhaps don't add the final litre of acid all at once, but rather just a little bit every day, do an EQ charge, then check SG the next day; and repeat. Easy to add acid, difficult to remove it.

Regarding the pricing for cells, someone wants you to finance their new Merc. Retail price for an Enersys 7OPzS490 cell is about 270 Euros including VAT.

BB.

Re: 48v battery advice

Greece is having terrible economic/political problems right now (as I am sure you know)... I did not see any news about Sunlight SA. So don't know if related or not (company appears to still be operating in Greece).

I wonder if you could take the cell to a local battery rebuilding shop and see what they think.

If the cell was filled with water--I am not sure if the battery bank would even function (battery should have fairly high resistance). You should have noticed the cell getting hot during charging and a lot of gassing (I would guess). If there was a lot of gassing, then the cell may have been damaged by so much oxygen generated during current flow (again, guessing)...

I would suggest recharging the cell until the SG does not rise any more, drain the battery and refile with new electrolyte and see what happens... However, since I know nothing about batteries at this level--My suggestion could be quite dangerous--Or just a waste of money for the acid on a cell that should be scrapped...

-Bill

Thommo

Re: 48v battery advice

Hi Steve, The licenced bandits (Norwatt) who live in Gijon (you couldnt get much further away from us and still be in Spain) wanted 150 Euros to deliver the cell to Almeria and also 75 euros IVA
Not in my lifetime boys....
Pete

Thommo

Re: 48v battery advice

Hey Bill,
All still seems to be going in the right direction. After 4 days - the cell is gassing nicely - the plates have taken on the colour of the other cells and the cell and battery voltages seem to be coming up nicely - battery voltage this morning 49.8v (total). There have been days in the past, in high summer, when we were getting 9 hours of sunshine, that the battery hasn't shown that voltage in the morning.
Continuing with all fingers crossed.
I'll keep you (all) posted
Regards
Peter

inetdog

Re: 48v battery advice

Thommo wrote: »

I am just staggered to think that my system and the battery have functioned for 5 years
(FIVE YEARS!!!) with, effectively, (electrically speaking) 23 cells!
And for it to now (apparently) reviving itself to working capacity is absolutely amazing! Don’t forget that I had already written off this cell, so the experiment was a kinda ‘Hail Mary’ shot.
Any thoughts anyone?????????

Just this: It may not be quite a complete a miracle as it seems at first glance that this cell is coming back. After all with no sulphuric acid in the cell, there could be no sulphation. And with water in it, there would not be the possible interactions of air with dry plates that might cause deterioration.
Bottom line would be that with only water in the cell it would be dropping about the same voltage (that required to electrolyze water, 1.48 volts) during both charging and discharging (but in the opposite direction: It would raise the charging voltage and lower the voltage during discharge. In that sense, you were running with more like 22.5 cells than 23, since that one was dropping the discharge voltage rather than increasing it at all. And the cell should have been bubbling merrily during both charge and discharge. Do you recall having to add more water to it than to the others?
A fine lesson in the value of using a hydrometer and a proof of Sherlock Homes famous statement that when you eliminate the impossible, whatever remains, however improbable, must be true!

Thommo

Re: 48v battery advice

Vey True Steve - very true! - I have to ask how you change your description on your profile from 'Registered guest' (like I am now) to 'Fizzycist' - like you have on your profile?
Regards
Peter

Thommo

Re: 48v battery advice

Steve - re my last - just figured it out !!!!
Peter

inetdog

Re: 48v battery advice

Thommo wrote: »

Steve - re my last - just figured it out !!!!
Peter

Peter -- Glad you figured it out.

Dave (not Steve)