sealed lead acid batteries?

[Jeremy Harris]

A few years ago, I bought a couple of 100Ah 12V sealed lead acid batteries from a dealer somewhere not fr off the M3, North of Basingstoke.  He had hundreds of the things, removed from data centre UPS systems

 

I now need another couple of these, as the last two were great, and still had loads of life left in them, I've been using them for around 8 or9 years and they were 3 years old when I bought them, and they are only just beginning to show signs of losing a bit of capacity.

 

 

I use these as a back up supply to keep our network and internet connection up and running during power cuts, and could really do with a couple more of these batteries.  The snag is that I didn't keep a record of the place I bought them all I can remember was that they took cash and were a big warehouse place, filled with pallet loads of sealed batteries.
 

I will need to pick them up, as they are heavy, around 60 to 80kg apiece if they are like the ones I have,  They are the sort of size that looks like it'll was designed to fit laying on their side in a rack system, but any gel type sealed battery at a bargain price would do.  I only draw around 3A max off these batteries when they are in use and they sit on trickle charge at around 13.5V most of the time.

 

Does anyone have any clues as to where I might find somewhere within reasonable driving distance from here that flogs off old data centre backup batteries, please?

[Onoff]

You might try a used forklift truck place like here:

 

https://phl.co.uk/about

 

 

[Jeremy Harris]

Thanks, I had thought about forklift batteries, but I'd have to keep them outside somewhere, as they aren't sealed. 

 

The big advantage of the old data centre backup batteries is that they are sealed gel AGM ones, so are safe to keep indoors, and are certified as such, as they are used inside data centres.  The ones I have are around a standard 19" rack internal width and depth, and about 5U high at a guess when laid on their side, and I think they were originally fitted into a big, modular, UPS system, to provide the short duration power needed before the data centre generators came up on line during a power cut.  The great thing about them is that data centres used to routinely replace these batteries every three years, just to be on the safe side, yet they were barely used, perhaps a few test cycles and maybe one or two genuine outage cycles, so they were really almost like new.

 

I wish I could remember the place I got them from, as he literally had dozens of pallets loaded up with the things, and was selling them for around £50 each.

[dpmiller]

At three years you'd probably be OK but best look closely at them for signs of overheating- the UPS supplied with our Immunostainers (a nice Riello) isn't worked hard, but I've replaced four sets of batteries this year in 6yo systems, the individual 12v AGMs in the bank/box had been hot enough to meld together...

[Jeremy Harris]

Good tip, thanks. 

 

The ones I bought originally, around 8 or 9 years ago, came from a seller on ebay, one of those 99p ads that's really just an advertising poster.  As the place was only half an hour or so's drive away I went up to see him, armed with a meter and load tester, and was pleasantly surprised to find that all the batteries he had looked and seemed to perform like new, even though they had date codes showing they were around three years old.  The only problem I had with them was trying to find the proper connector to fit them - they had a two blade connector arrangement on one end, that must have been designed to allow quick replacement.  I ended up making my own connectors for them, with Anderson plugs on the end of short flying leads.

 

I have a feeling that this bloke had a contract for replacing batteries in some pretty big data centres, as his warehouse was stuffed to the ceiling with pallet loads of batteries, most the same size and type (around 100 Ah, sized to fit a 19" rack).

 

I've hunted all over the place and can't find anyone selling off these old batteries any more.  May be the high price of scrap lead has made it more economical to just scrap them rather than try and sell them second hand.

[Onoff]

There's legislation came in in 2009 which pretty much prevents Joe Public buying second hand batteries like this. The cynic in me says it prevents you doing anything "off grid" on the cheap. No different to how "they" reduced the FiT rates when they realised the amount of cash they could lose!

 

It's all about provable, documented waste streams & waste transfer tickets now.  Saying that the "mixed" loads I see still going off site suggest otherwise unless they get sorted elsewhere!  Things like batteries and waste oil, anti freeze etc are going to attract more attention than a bit of old timber and Unistrut though!

 

I'd try a battery recycler like this:

 

http://www.g-pbatt.co.uk/industrial.html

 

Maybe play on your SHC connections? I think even they have to prove where a customer's waste went now in that it was properly disposed of.

[SteamyTea]

Why not call up a couple of battery supplier in Basingstoke and ask if they know who it may be.

I got a job offer that way once.

Edited December 30, 2017 by SteamyTea

[Jeremy Harris]

12 minutes ago, Onoff said:

There's legislation came in in 2009 which pretty much prevents Joe Public buying second hand batteries like this. The cynic in me says it prevents you doing anything "off grid" on the cheap. No different to how "they" reduced the FiT rates when they realised the amount of cash they could lose!

 

It's all about provable, documented waste streams & waste transfer tickets now.  Saying that the "mixed" loads I see still going off site suggest otherwise unless they get sorted elsewhere!  Things like batteries and waste oil, anti freeze etc are going to attract more attention than a bit of old timber and Unistrut though!

 

I'd try a battery recycler like this:

 

http://www.g-pbatt.co.uk/industrial.html

 

Maybe play on your SHC connections? I think even they have to prove where a customer's waste went now in that it was properly disposed of.

 

 

That explains why there seem to be no ads for these second hand batteries any more.  Back when I bought the last two, there were loads of places selling ex-data centre UPS batteries, but now they've all seemingly gone.  IIRC, I got the original tip off about this ebay seller from one of the renewable energy forums, can't recall which one, that had a link to the advert.  A fair few there were using them to build cheap off-grid solutions.

 

14 minutes ago, SteamyTea said:

Why not call up a couple of battery supplier in Basingstoke and ask if they know who it may be.

I got a job offer that way once.

 

 

I might try that.  This place was North of Basingstoke by a fair bit, somewhere around Hook, I think.  However, if the regs no prohibit the sale of second hand batteries then it may well be that I have to look at forking out for new ones.  The annoying thing is that I doubt the new ones would last much longer in this application.

[Spangles]

@JSHarris Give a call to a few data centres close to your area. Who knows, you might get lucky and they'll be willing to 'offload' used batteries. 

Quite a few dotted around 

https://www.google.co.uk/maps/search/data+centres+uk/@52.1990019,-2.6401555,8z/data=!3m1!4b1

 

spangles

[Vijay]

a mate of mine goes up and down the country doing something with large batteries and I've messaged him. Have you got a pic of the battery you're looking for?

[Onoff]

With cheap labour here I guess these things are readily recyclable.

 

Is there no way of you popping the seals on the batteries you have and regenerating them somehow? Even if I'm means storing them upright thereafter.

[Jeremy Harris]

20 minutes ago, Vijay said:

a mate of mine goes up and down the country doing something with large batteries and I've messaged him. Have you got a pic of the battery you're looking for?

 

I can try and take a photo next week, I'm not sitting near them at the moment.  The shape and size doesn't matter, though, as I have them sat on the floor so they could be any shape really.

 

7 minutes ago, Onoff said:

With cheap labour here I guess these things are readily recyclable.

 

Is there no way of you popping the seals on the batteries you have and regenerating them somehow? Even if I'm means storing them upright thereafter.

 

Be a tough job to get inside them, I think.  They have cases that look as if they are made to be chucked around by gorillas.  Not sure they've dried out, as they've been on a constant 13.5 V charge all the time I've been using them, and when called upon to run the router. modem etc in a power cut I doubt the peak discharge exceeds 3A, and is probably around half that most of the time.  There's a low voltage cut-out that's set for 11.5 V at the moment, that turns the load off if the battery gets below that voltage, so they haven't been over-discharged ever, either.  I suspect they are just at the end of their life, as they are around 12 years old, and probably had a design life originally of around 5 years or so.

 

The real issue here seems to be that, as @Onoff mentioned, the law has changed and everyone is now required to keep accurate records of disposal, which really stops batteries being sold off second hand to ordinary people.  I can understand why the law was introduced, but it's a bit of a sledgehammer to crack a nut, especially as it seems to have stopped people like me getting an extra few years life out of these things.

[Onoff]

Where there's muck there's brass! 

 

"They" have to make money from somewhere. Think how local councils have householders sorting rubbish into streams and and many cases fine you if you don't.  (Speed cameras, parking fines, late tax returns etc. All a tax on "living").

 

This is interesting:

 

https://www.letsrecycle.com/news/latest-news/batteries-sector-set-for-shakeup-after-portable-ruling/

 

&

 

https://www.letsrecycle.com/news/latest-news/battery-collection-costs-expected-to-shoot-up/

[Jeremy Harris]

I found the paperwork for the batteries I bought years ago, and as far as I can tell they are very similar to the Sonnenschein A400FT A412/120 FT  batteries, but with a custom blade connector at one end at the front.  My guess is that they were specially designed to just have some sort of quick-fit connector in the rack they were originally installed in. 

 

Looking at the prices of new gel batteries, I'm going to have a serious rethink about my standby system.  Originally it was just a way to keep the internet connection and house wifi running during a power cut (we get loads of power cuts here, for some reason) and it does that job just fine, but because the ex-UPS batteries were cheap, I just used them, with some voltage regulators to supply the required DC to the modem, router, switch etc.  I didn't bother optimising anything, as I had loads of spare battery capacity, so there are separate regulators for every device, including a boost-buck regulator to give a steady 12 V to the modem, irrespective of the battery voltage. 

 

The system is pretty simple.  The battery runs the voltage regulators 24/7, and then run the bits of kit with the right regulated DC voltage.  A small switched mode power supply is set to 13.5V and that float charges the battery all the time the mains is on.  If the mains fails, all that happens is that the battery stops getting charged.  As a safety device, I added a small extra circuit, with a latching relay, that draws less than 1 mA, and monitors the battery voltage.  As soon as the battery discharges down to 11.5 V the latching relay disconnects the battery from everything.  There's a reset button to bring the system back on line if this ever happens (it never has).

 

The system is a bit wasteful of energy, both because of the poor Peukert number for the lead acid battery, but also because the voltage regulators and charger aren't optimised at all.  If I'm faced with having to spend lots of money (over £200) on a replacement battery that's as good as the one I have now, then I may as well look at switching to a different system, using longer life LiFePO₄ cells, perhaps.  I happen to have a few dozen old 10 Ah LiFePO₄ cells spare, that aren't in the best of health, but are good enough to build a proof of concept system.  I could change the battery voltage so that I can use efficient synchronous rectification buck regulator for both the 12 V and 5 V supplies, and I could improve the charging and battery management system to reduce losses a fair bit.  Using LiFePO₄ cells also means I could get away with a smaller capacity pack, as the usable capacity would be a fair bit higher than for the sealed lead acid battery.

 

It's more work, but I think it should be possible to make a decent backup system for around the same cost as a replacement battery, and that would probably have a longer life.

 

I just need to sort and capacity test my big box of Headway LiFePO₄ cells to see how many of them are any good..............

[dpmiller]

how many Ah do you really need?

[Jeremy Harris]

3 minutes ago, dpmiller said:

how many Ah do you really need?

 

 

Good question, as it depends on the battery chemistry, at least as far as usable capacity required. 

 

I've started measuring the average current each device draws, to get a better feel for it, as before I just went for over-kill on the basis that 100Ah sealed gel lead acid batteries were cheap and dead easy to rig up.

 

So far, I've found that the switch draws around 450 mA at start up (on 5 V) and idles at about 120 mA.  I need to run some traffic through all the ports to try and get a feel for the average current, but would guess that something like 300 mA might be about right.

 

The modem draws about 600 mA at start up from 12 V, but this drops back to a pretty steady 330 mA when it's running and doesn't seem to change with the amount of traffic it's handling to any appreciable degree.

 

I'm struggling to get a measurement from the router at the moment - for some reason I'm getting wildly variable readings from one switch on to the next, plus there is a lot of variation as it does things like poll the 5 GHz band every few seconds and does some sort of regular internal cycle where the current goes up and down a lot.  Best guess is that it's somewhere around 500 to 600 mA at 12V, with a peak at around 850 mA.

 

Using those figures, and assuming I'd like 24 hours of back up operating time, and using a figure of 85% for the switched mode regulator efficiency (I reckon I can do a lot better than that with synchronous rectification, though, probably around 92 to 94% with luck), then it looks like I need around 340 Wh or so of usable capacity.   If I was to use a 5S LiFePO₄ cell arrangement then that would give me a voltage range of between about 17.75V fully charged (assuming that I only charge the cells to 3.55 V to extend their life) to 16 V at discharge cut-off (again, assuming I want to cut off at 3.2 V per cell to extend life). 

 

It looks like a pack with a nominal capacity of around 30 Ah would give me a bit of headroom and still allow the cells to operate within a limited SoC range to extend their life.  The question now is whether I can find 15 good cells in my collection of 10 Ah Headway LiFePO₄s.  I know I had a couple of hundred of them originally in my motorcycle pack, and that only around 20 failed, but they have been sat lying around for a time, so I need to cycle test any that look good to see how they hold up.