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Author Topic: 16V batteries!?  (Read 6003 times)
timbo
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« on: November 08, 2007, 04:02:26 PM »

I just connected my 1kW Navitron turbine up and connected the 4 new "12" Volt batteries I bought from a local ships chandlers.

They are Fiamm deepcycle type 685.

With the 4 connected in series to give a nominal 48V, the actual voltage across then is currently 62.8V which is too much for my inverter which trips out.

One battery measures 14.2V, the other three are 16.2V (+/- 100mV)

Are the batteries duff? The little indicators on them say they "require charging" 16V seems too high to me...

Tim.
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Ivan
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« Reply #1 on: November 08, 2007, 04:14:57 PM »

Are they gel cells? They have slightly higher voltages than wet lead acid batteries.

You'd expect a fully charged wet battery to be 13.8v and a fully charged gel cell to be 14.4v.

Gel cells aren't really suitable for wind turbine charging, as they require very specific charging profiles.

You might be able to fool the inverter by putting a big diode in the line to drop 0.6v or so - although this will be wasted as heat.
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timbo
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« Reply #2 on: November 08, 2007, 04:46:41 PM »

Hi,

Thanks for the quick reply.

They are wet cells...they look just like car batteries with a cap to top up the acid/water but are supposedly "deep cycle" . Sold for use on boats.

16.2 V is pretty high huh?!!

The meter on the charge controller that came with the 1kW system is nudging 70V in this wind, but if I try and disconnect the turbine now it will spin itself to death I  imagine. But I guess that if the battery volts gets even higher then the charge controller may be at risk too.

Tim.
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6kW Kingspan turbine expected soon.
Alan
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« Reply #3 on: November 08, 2007, 05:05:04 PM »

Hello Tim

Sounds like your test meter has had a bad day.

A nominal 6 wet cell battery at 80% charge is 13.8 volts

at 100% charge this would be 14.4 volts for average ambiant temperature conditions.

Regards

Alan.
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Alan
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« Reply #4 on: November 08, 2007, 05:24:44 PM »

Cant spell

For Ambiant read Ambient

Think Ivan has got it backwards. A wet cell above 80% ( 13.8 volts ) will require regular topping up with distilled water but is quite happy being charged to 100%. A gel battery is limited to 80 % because by design the gel can not be replenished.

Regards

Alan
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timbo
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« Reply #5 on: November 08, 2007, 06:09:29 PM »

Hi Alan,

I just checked with a second DVM and get 15.9V....both meters read 1.61V on a new AAA cell as a reference.

Cells are all topped up (as new from the shop)

wierd.

Tim.
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6kW Kingspan turbine expected soon.
Alan
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« Reply #6 on: November 08, 2007, 06:22:47 PM »

Hello Tim

Sounds like three of them have gone high resistance because they were not regularly charged during storage. This should show it self by the current being low when they are charging. You need to get them checked by a high current discharge tester at your local garage. The marine shop where you purchased them should have a discharge tester. Any 6 cell wet cell left below 10.5 volts will self destruct very quickly.

Regards

Alan
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timbo
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« Reply #7 on: November 08, 2007, 09:23:53 PM »

Hi Alan,

Thanks for your help.

I guess I expected the batteries were duff but was hoping for a miracle cure.

Time to spend some more money then. :-(

Tim.
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camillitech
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« Reply #8 on: November 08, 2007, 09:36:51 PM »

Hi Alan,

Thanks for your help.

I guess I expected the batteries were duff but was hoping for a miracle cure.

Time to spend some more money then. :-(

Tim.

if your using wet batteries timbo i find a hydrometer the most useful indicator of knackeredness. i have several battery banks which i check regularly both at home and work (a ferry) it can save you allot of grief and time. i record all my SGs at least monthly and keep a log Roll Eyes i know it's a bit obsessive but i have to do it weekly at work on 5 different battery banks and it really does tell you when something is about to go wrong long before it does.

regards, paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SMA SI6.OH, 800ah Rolls, 8kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
Ivan
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« Reply #9 on: November 09, 2007, 01:45:56 AM »

Alan, Yes you are right - I was quoting 'floating voltage' rather than charging voltage. I've always found that when you disconnect the charger from a fully charged battery, the voltage falls quite quickly to the float voltage.

Timbo, I would also be tempted to put a load onto the batteries and check what the voltage drops down to, how quickly it climbs back up and whether the battery will cope with a good load. No substitute for the discharge test, though.


Ivan
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timbo
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« Reply #10 on: November 09, 2007, 10:26:35 AM »

Hi, Cammilltech, Ivan, Alan,

I  located locally a second-hand Forklift battery with 36 cells rated (when new) 480Ah.

The guy says that he knows 6 of the cells are duff but he is sure that there are more than 24 good ones.

Can you suggest what tests I should do before buying it?

What should the SG read? (I have never done this before) and he says he can discharge test 6 cells at a time, what result should I look for as a minimum.

How consistent should the cell voltages be, within 100mV of eachother??

He is asking 350 for a tested, charged set.

Tim.

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6kW Kingspan turbine expected soon.
Ivan
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« Reply #11 on: November 09, 2007, 03:23:57 PM »

Forklift batteries are very resilient - and can even be rebuilt by specialists. Having owned a forklift with dodgy batteries, the things I would check are 1)that they hold a charge and 2) that they haven't been regularly topped up with tapwater instead of deionised water.

Not sure about SG etc.

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Antman
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« Reply #12 on: November 09, 2007, 08:09:04 PM »

In very general terms, >1.26 is well charged and <1.15 would be pretty darned flat.

But exact figures depend on the original dilute sulphuric acid SG strength, temperature and the type of battery construction. Only the battery manufacturer / data sheet for the particular battery can give exact figures for a given battery.

Antman
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camillitech
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« Reply #13 on: November 09, 2007, 08:57:01 PM »

In very general terms, >1.26 is well charged and <1.15 would be pretty darned flat.

But exact figures depend on the original dilute sulphuric acid SG strength, temperature and the type of battery construction. Only the battery manufacturer / data sheet for the particular battery can give exact figures for a given battery.

Antman

the main thing to look for is uniformity, cos like antman says it depends on lots of things not least of which is how accurate your hydrometer is. we have a different one by each battery bank to save splashing  acid around the boat Wink and they all read different Roll Eyes so i look for no more than 10% difference, though you will get to know your own battery bank very well if you keep a log (another reason for avoiding gel batteries). if your forklift batteries are all in one bank i'd just pick the 24 with the highest sg Grin but PLEASE bear in mind i'm no electrician i've just been around lots of battery banks Huh

regards, paul
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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SMA SI6.OH, 800ah Rolls, 8kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
wyleu
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« Reply #14 on: November 21, 2007, 05:03:44 PM »

http://www2.cat.org.uk/shopping/product_info.php?products_id=1678&osCsid=8d9d95804c9ce9a6d283d7dd661dc404

A good book on batteries.
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