Author Topic: optimum temperature range for battery bank long life  (Read 3351 times)

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dlenox

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optimum temperature range for battery bank long life
« on: November 02, 2009, 09:40:14 AM »
All,


I have searched and not found an answer to "what is the optimum temperature range for a battery bank"?


I have seen posts on batteries in low temperature and high temperature, as well as what telephone company maintains, but I am looking for the temperature range that gives the batteries the longest life - assuming that they are charged properly and not deeply discharged.


I have AGM batteries and does this temperature range differ for various other types of batteries.


Dan Lenox

« Last Edit: November 02, 2009, 09:40:14 AM by (unknown) »

Flux

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Re: optimu
« Reply #1 on: November 02, 2009, 10:49:18 AM »
I don't think there is a definite answer. Certainly high temperatures lead to short life and anything above 25c is probably not good.


At low temperatures the performance suffers but within reason you get a little longer life. Very low temperatures pose many problems with freezing on part discharge and low performance on heavy loads.


Here in the UK the normal temperatures cause little problems as we don't have the extremes. Temperatures from 10 to 20 C seem to be no problem.


In certain military applications they heat the battery boxes in low temperatures to get the things to perform but I don't think life is the main consideration for this.


Batteries die if you use them, they die if you don't and they die a lot quicker above 25c but you can't win. AGM seem a bit less troubled by sulphation on part discharge but you pay a price for them and although they tend to last longer under some conditions I doubt that that they are more cost effective. They certainly won't stand the abuse of the old wet Plante batteries but they don't need the constant maintenance either.


Flux

« Last Edit: November 02, 2009, 10:49:18 AM by Flux »

SparWeb

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Re: optimum temperature range for battery bank
« Reply #2 on: November 02, 2009, 12:41:32 PM »
I have to concur with what Flux said, but I'll add my 2 cents because I'm using AGM's in a pretty cold climate, with little ill effect.  The batteries are in an insulated shed, but when it goes down to -30C for a week it will be -30C in the shed for much of that time.  I put the dump load inside the shed for the winter and the inverter may put out a bit of heat under load, but otherwise not a lot of temp control out there.


Every once in a while I do a deep discharge of the AGM cells to see how they're doing, and so far I haven't found much degradation in their condition since I got them.  Of course these were discarded and used when I found them - I could never have afforded to buy these things.


Do you have a temperature sensor on the charge control?  (I'd be surprised if you didn't, let me put it that way.  Everything else you have looks well done.)  I made up a chart for reference so that I can tell how high the voltage should go when they're full.  With lower temperatures the float voltage must be raised to maintain a "full" charge.  But when I read the installer's manual for these batteries, I found that I cannot let them go above 28.2V.  This causes conflict with the temperature compensation, because it wants to charge them above the hard limit of 28.2V.  I have to turn down the float voltage knob manually when it's below -20C (aproximate temperature I can't remember exactly).  If you can't get by with that kind of situation, then yours have to be inside a heated building.


So when it's extremely cold, I have to live with:

a) reduced charge voltage,

b) reduced performance, (both battery chemistry and inverter efficiency) and

c) risk of freezing electrolyte when the charge gets too low.


That combined state of affairs means that the most full they can get is 80%, they deliver only half the Amp-hours for the nameplate state of charge, and I cannot let them discharge below 50% for fear of freezing the cells.  


My 800 Ah is whittled down to only 120Ah!  Compounding penalties, but it's just a hobby.  I'm not trying to survive off this stuff.  Good thing it's almost always windy in the winter here!  I've only been doing this for 2 years, and I started out with some abused cells, so I can't comment on "long life" direclty.

« Last Edit: November 02, 2009, 12:41:32 PM by SparWeb »
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rossw

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Re: optimum temperature range for battery bank
« Reply #3 on: November 03, 2009, 12:10:09 PM »
I got some used 2V/500AH AGM cells several years ago. They've been treated badly by virte of me not having had enough PV capacity to ever get them to float until the last month.

They don't get as cold as you northern guys - they live in the bunker with me, never get below 19 deg C, rarely get above 25 deg C.

By my rough calculations, they've had close on 4,000 discharge/charge cycles since I have had them and they're only a little worse now than they were when I got them.

They have spent most of the last few years getting a rapid charge from 6am to 9am, then discharging through the day, another charge from 7pm to 9pm, then discharging overnight. Week in, week out. Sometimes during bad weather they've needed a topup charge in the middle of the day too.

I can only seem to pull about 150 amphours out of them before their voltage has dropped to 1.88v/cell

It says on the cells 500AH, 1.8V @ C10 rate or 484AH, 1.75V @ C8 rate and I'm pulling well below the C10 rate. Should I be letting them go lower? (I don't think so!)

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« Last Edit: June 03, 2011, 06:43:54 PM by rossw »

dlenox

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Re: optimum temperature range for battery bank
« Reply #4 on: November 08, 2009, 12:54:56 PM »
Guys,


Have had issues in posting a comment for last week or so, talking with Dan F about it.


Did more research and found out the the optimum temperature range for battery bank is between 65 - 75 degrees farenheit.


Dan Lenox

« Last Edit: November 08, 2009, 12:54:56 PM by dlenox »

dlenox

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Re: optimum temperature range for battery bank
« Reply #5 on: November 08, 2009, 12:57:18 PM »
Test comment, last one sucessfully made using FireFox.  Previous attempts using IE or Opera all failed and have not been able to post comment to anything...
« Last Edit: November 08, 2009, 12:57:18 PM by dlenox »