best 12 Volt bettery in the heat

[Mwater]

We are looking for 12 V batteries in the 80-120 amp/hour range that have minimal maintenance, the battery will be used with solar systems. The systems will be installed in the desert in South California, where the temperature in summer can reach 50C or 125F .since, the temperature reduces the battery life, I want to know what batteries could be used in this type of environment and if you have a link to the manufacturer.


Thanks,

 

[ScottyUK]

Have you tried Google? What did you find?

Lithium cells are good for that temperature range but in those sizes will come at a price. You've given so little information that it is difficult to help: for example, what are the load characteristics? 120AH cells designed for low discharge over a prolonged period will be very different from cells optimised for short duration high rate discharge.

Put up as much information as you can about your application: it makes things much easier when people have all the facts.


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If we learn from our mistakes I'm getting a great education!

 

[Mwater]

the discharge is for measurement instrument with a continuous load of 20 watt. I think the 100 amp-hr battery is what I need.
I checked the ni-cd batteries and they are around $2000. from my research the ni-cd are indicated as best solution. For low maintenance lead-acid batteries the absorbed Glass mat is recommended and is around $280.

ScottyUK you mentioned lithium but I think they have short life time.
I had in mind to try multiple 12V NiMH battery back do you have any suggested related to NiMH batteries and how to charger them.

 

[ScottyUK]

Parallel batteries are usually not a good idea - ensuring equal charging and discharging is tricky. I haven't seen single NiMH cells in the size range you're considering but that might be my ignorance.

What do you mean by 'short lifetime'? 'Lithium cells' covers quite a broad range of different cell chemistries. From my admittedly limited understanding, most of the lithium technologies are pretty good in terms of low self discharge and have equal or better service life (# of charge / discharge cycles) compared to other cell types. An applications engineer at (e.g.) SAFT or Lithium Technology might be worthwhile.


Have a look at

http://www.lithiumtech.com/602050HE.pdf

for an example of one of the larger cells available.


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If we learn from our mistakes I'm getting a great education!

 

[IRstuff]

How long do these things need to last? This has to enter into your calculations in trading different types of batteries.

TTFN

FAQ731-376

 

[Mwater]

IRstuff, the system will be used for more than 5 years. the ALCAD ni-cd battery can last for 20 years but the unit price is $2000 for multiple batteries that's a lot.

ScottyUK you are right about the size range. my idea is to have 12 volt pack (10 ah) in parallel; I don't know if this will work. I so online some 12v 10amh NiMH batteries. as you said there is the problem of equal discharging and charging.

https://www.all-battery.com/index.asp?PageAction=VIEWCATS&Category=188&SetOrderBy=2

the charger:

https://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=2005

ScottyUK, I contacted GAIA by email to get an idea about there prices.

 

[sreid]

I'd consider AGM lead acid batteries.

http://www.lifelinebatteries.com/

 

[Mwater]

For the lead acid batteries the problem in temperature and where this batteries will be in an ambient temperature that could reach 60 C (140F)

Following scottyUK advice I dug more about lithium batteries. I found some information about lithium ion phosphate. Valence batteries are not bad; I don’t know the price yet but I hope is not too high.

I mentioned before NiMH battery pack solution, do you have any idea about the type of problem that I could have with that type of solution. Also, if has some suggestion about the advantage and disadvange of using lithium ion phosphate, feel free to mentioned.

 

[ScottyUK]

Have you considered using a higher voltage battery to get your AH requirements down? DC/DC converters are readily available with efficiencies >90% which could convert (e.g.) a 48V nominal battery voltage down to a regulated 12V. This would get around the problems with paralleling cells or blocs.


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If we learn from our mistakes I'm getting a great education!

 

[Mwater]

first I wanna make sure that the calculation for the battery size is right.
The battery are charged by a solar panel the maximum amp is 4.8 amps, the minimum hours of charging per day is 4, Number of consecutive days without sun is 3.
the battery will power a system that has a continuous Dc load of 3.7 watt and 0.6 watt load for one hour a day also the battery will power a gate that has a DC load of 324 watt for few minutes a day (total 1.4 hours a week).
I have 12.7 Ah a day and 3 days without sun * 1.2 = 76 Ah. (100Ah to safe)

 

[IRstuff]

It doesn't look like you have enough charging capacity to handle more than one 4-day no sun condition every 12 days. Is that adequate?

TTFN

FAQ731-376

 

[Mwater]

I think will be fine if the max consecutive days without sun is 3 days. even the 3-day will rarely happens. so to have more than one 4-days in 12 days is almost impossible. its almost a desert so the problem is more the heat than sunshine.

 

[IRstuff]

3 days without sun is actually about 4 days of battery drain. Starting at sunset of the last day with sun, until sunrise of the first day with sun, it's a minimum of 3.5 days of battery drain.

TTFN

FAQ731-376