Batteries for warmer climate

[digimart]

Hi
I need to have a battery bank of 48V with power ratings of 275AH or 300AH to connect with my Off-Grid Solar Power System.
My wish is to purchase AGM or GEL maintenance free batteries.
At our place during summer season the inside room temperature rises to around 40C ( 104 F ) during day time, and in winters at night drops to 1C ( 34 F ).

Its known fact that such temperatures are generally not deemed to be good for longer battery life.

However, I like to ask , that is there any such brand available which has good performance in temperatures as in my case ?

If none is available, then I would like to know from your personal experiences that which brand have you found good and satisfactory for your own systems ?

Regards.

[mapmaker]

My wish is to purchase AGM or GEL maintenance free batteries.
At our place during summer season the inside room temperature rises to around 40C ( 104 F ) during day time, and in winters at night drops to 1C ( 34 F ).

Its known fact that such temperatures are generally not deemed to be good for longer battery life.

However, I like to ask , that is there any such brand available which has good performance in temperatures as in my case?

I don't know much about AGM or GEL batteries and temperature. With flooded batteries, a lower concentration of sulfuric acid helps in high temperatures.

--mapmaker

[Mike90250]

Buy a battery from a local supplier of major brands. They tune the SG of the battery (acid content) to maintain lifetime, but you loose a bit of capacity.

[digimart]

Ok, just for my own understanding, that for warmer climate the specific gravity has to be more or less ?

Is there any online formula, which I could use to figure-out correct SG, keeping in view our day temps of upto 45C

[Sunking]

Ok, just for my own understanding, that for warmer climate the specific gravity has to be more or less ?

Is there any online formula, which I could use to figure-out correct SG, keeping in view our day temps of upto 45C

As temp goes up, SPG goes up. Every battery manufacture has a formula for their product. Typically .03 points for every 5 degrees C above 22 C, and subtract .03 points for every 5 degrees below 22 C. Many charge controllers come with Temperature Compensation to account for this and is programmable.

As for battery type Flooded would be the best choice for warm weather, and AGM for extreme cold weather. Gel should never be used for cycle service period.

[mapmaker]

As temp goes up, SPG goes up.

Huh? Is SPG specific gravity? I thought as electrolyte warms up it becomes less dense (lower SG).

Also, the OP is not trying to measure SG... he wants to know whether to modify SG because of the hot climate. I was under the impression that manufacturers "tune" their batteries for hot climate by reducing the acid concentration... is that wrong?

--mapmaker

[inetdog]

... I was under the impression that manufacturers "tune" their batteries for hot climate by reducing the acid concentration... is that wrong?

--mapmaker

My understanding was also that a lower initial SG (measured at standard temperature) was used for tropical batteries to reduce the effect of positive plate corrosion, etc. that results from the increased chemical activity of the electrolyte at higher cell temperatures.
See http://www.powerstream.com/1922/batt.../chapter12.htm

[Sunking]

My understanding was also that a lower initial SG (measured at standard temperature) was used for tropical batteries to reduce the effect of positive plate corrosion, etc. that results from the increased chemical activity of the electrolyte at higher cell temperatures.
See http://www.powerstream.com/1922/batt.../chapter12.htm

I read through some of that article but did not find any reference for adjusting SG for climate. SG of electrolyte is temperature specific. When initial electrolyte is put into the is specified at 70 degrees @ 1.28. Points are added if warner, and subtracted if colder. Here is verbiage from one manufacture on the subject of temp corrected SG:

Temperature Correction

SG of acid is temperature dependent. If the temperature is very cold or very hot this can lead to incorrect readings. To correct for temperature use the following equations the equations or below 70ºF subtract points (0.03 per 10ºF) and above 70ºF add points.

• Correction factor = (0.331 x T/ºF - 23) / 100 or 0.03 pts per 10 ºF
• Correction factor = (0.595 x T/ºF - 12.5) / 100 or 0.03 pts per 5 ºC

So basically if your battery electrolyte temp is 60 degrees F and the SG reads 1.25 it is 100% SOC
Same battery at 80 degrees reads 1.31 is 100% SOC
At 70 degrees 1.28 is 100% SOC

Temperature compensation built into controllers and chargers is negative compensation where as the temp goes up, voltage is decreased, and vice-versa as temp goes down the voltage increases.

[inetdog]

I read through some of that article but did not find any reference for adjusting SG for climate. SG of electrolyte is temperature specific. When initial electrolyte is put into the is specified at 70 degrees @ 1.28. Points are added if warner, and subtracted if colder. Here is verbiage from one manufacture on the subject of temp corrected SG:

Temperature Correction

SG of acid is temperature dependent. If the temperature is very cold or very hot this can lead to incorrect readings. To correct for temperature use the following equations the equations or below 70ºF subtract points (0.03 per 10ºF) and above 70ºF add points.

• Correction factor = (0.331 x T/ºF - 23) / 100 or 0.03 pts per 10 ºF
• Correction factor = (0.595 x T/ºF - 12.5) / 100 or 0.03 pts per 5 ºC

So basically if your battery electrolyte temp is 60 degrees F and the SG reads 1.25 it is 100% SOC
Same battery at 80 degrees reads 1.31 is 100% SOC
At 70 degrees 1.28 is 100% SOC

Temperature compensation built into controllers and chargers is negative compensation where as the temp goes up, voltage is decreased, and vice-versa as temp goes down the voltage increases.

Temperature correction of the SG reading to allow for the difference in reading of a hydrometer based on the electrolyte temperature is a very different thing from putting a different temperature corrected SG electrolyte into a battery that is intended for use in a hot climate.

Search the text in the article for "tropical" and you will see that it lists the "initial" SG of each battery type and for the most part a lower SG is recommended for "tropical" use.

A major source of confusion is that a float type hydrometer will, as you noted, give different hydrometer readings at different temperatures for exactly the same electrolyte. Heck, the SG of pure water also changes with temperature, leading to the novelty thermometers that consist of a bunch of temperature numbered floats in a liquid.

And the casual references in most literature (and here) refer to the SG after temperature correction, whether that correction is built into the hydrometer mechanism or not.

[Soulearner]

Heck, the SG of pure water also changes with temperature, leading to the novelty thermometers that consist of a bunch of temperature numbered floats in a liquid.

I always wondered how that worked - thanks.
Archimedes never mentioned SG changing with temperature.

[inetdog]

I always wondered how that worked - thanks.
Archimedes never mentioned SG changing with temperature.

One way of defining SG would be to take the ratio of the mass/volume of the liquid in question to the mass/volume of water at the same temperature. But that is not the definition used, so SG varies with temperature even for water.