Best battery chemistry for high ambient temps?

[Charlie]

I'm specifying components for PV installations in equatorial Africa
where temperatures can routinely approach 100 F.

I have seen operating ratings for AGM batteries at 140 F Tmax, but am
having a hard time finding Tmax for both Gel and flooded cell deep cycle
designs.

I'll take the obvious steps to minimize temperature, but I'm still
concerned about thermal runaway and shortening the life of the battery
system.

Can anybody point me to an unbiased resource that I can use in design?

Thanks in advance!

Charlie

 

[Charlie]

Thanks for that link - it's VERY interesting stuff!

Very high initial costs, with astronomical claims of cells still
delivering full rated power at *50* years old.

I don't know whether commercially available charge controllers know how
to deal with them though.

I'll investigate further, though I think in the African market, the high
initial cost might rule them out.

Charlie

 

[danny burstein]

One of the huge problems with NIFE batteries is their very poor
efficiiency - you can lose 50-60% of your power just charging them. Much of
what they say is true, but the size, weight per amp-hour, and grossly
inneficient charge/discharge cycles make them pretty unpopular.

In the Bad Old Days they were used as power levelers in
streetcar runs. They'd be hooked up in a shed along
the track and get charged up between car runs.

While they weren't, as you've mentione, the most
efficient, they were very low maintenace and
lasted just about forever, even in the middle of
nowhere with no one checking on them.

When the train came by, they'd partially discharge
and supply part of the power. Made it
much more practical than providing a grid arrangement
for full maximum power for the whole track run..

(since these were stationary and used by railroads,
the weight and size was secondary compared to the
long term reliability).

They've also been used in remote arctic weather
stations such as Drift Station Zebra - again, for
the very low maintenance and high reliability.

 

[SJC]

I'm specifying components for PV installations in equatorial Africa where temperatures can routinely approach 100 F.

I have seen operating ratings for AGM batteries at 140 F Tmax, but am having a hard time finding Tmax for both Gel and flooded
cell deep cycle designs.

I'll take the obvious steps to minimize temperature, but I'm still concerned about thermal runaway and shortening the life of the
battery system.

Can anybody point me to an unbiased resource that I can use in design?

Thanks in advance!

Charlie

I would use the AGM. I use an Johnson Controls and it holds a charge for
a very long time and can deep cycle very well. There are never any water
levels to worry about and we get days of 100-110F in the summer months.

 

[Landline]

Polyethylene plastic cases with gasketed removable lids with built in one
fill water level that can be re-built locally by locals.
You do not say what size the systems are, but if they are for housing, then
stick on a Morningstar SHS controller.
These Polyethylene plastic case batteries are made in China. They have
replacement cell kits and the batteries are easily rebuilt.
I will see if I still have the name of the Chinese manufacturer. They are
in popular use around the Pacific.

 

[Bill Darden]

I'm specifying components for PV installations in equatorial Africa
where temperatures can routinely approach 100 F.

I have seen operating ratings for AGM batteries at 140 F Tmax, but am
having a hard time finding Tmax for both Gel and flooded cell deep cycle
designs.

I'll take the obvious steps to minimize temperature, but I'm still
concerned about thermal runaway and shortening the life of the battery
system.

Can anybody point me to an unbiased resource that I can use in design?

Thanks in advance!

Charlie

Hi Charlie,

Can you bury the batteries? or least partially bury them in a cellar?
Thermal runaway is a big problem for AGM and Gel Cell VRLA when you
get over 120 degrees F. The wet chemistries will handle the heat, but
require more watering and experience accelerated positive grid
corrosion. In Africa, almost every power generation plant and
telephone exchange has batteries, may they have some tricks to keep
them cool.

Kindest regards,

BiLL.....

www.batteryfaq.org

 

[Bill Kaszeta / Photovoltaic Resources]

Hi Charlie,

Can you bury the batteries? or least partially bury them in a cellar?
Thermal runaway is a big problem for AGM and Gel Cell VRLA when you
get over 120 degrees F. The wet chemistries will handle the heat, but
require more watering and experience accelerated positive grid
corrosion. In Africa, almost every power generation plant and
telephone exchange has batteries, may they have some tricks to keep
them cool.

Kindest regards,

BiLL.....

www.batteryfaq.org

Thermal runaway is generally not a consideration in PV
systems that have a limited current out of the PV array.

If you have a thermal runaway problem when backing
up with a generator, you could simply detect the situation
(excessive current when battery is hot) and terminate the
the charging until the battery cools.

I know from experience that temperatures in some of
equatorial Africa (Gabon) do not generally exceed 100F
or drop below 85F.

A real problem in Africa is planning the end of battery life
recycling that some agencies require.

I have seen GNB Absolyte IIP batteries last for 5-6 years in
Saudi Arabia whic makes equatorial Africa seem relatively cool.

You may want to consider a smart battery enclosure in which
the batteries are ventilated only at night when it is cooler. Worked
well in Arizona.
Bill Kaszeta
Photovoltaic Resources Int'l
Tempe Arizona USA
[email protected]

 

[Anthony Matonak]

Charlie wrote:
....

The other alternative is flooded cell, but given that the populations I
hope to serve don't have the technical savvy to maintain batteries, nor
do they have access to distilled water, flooded-cell doesn't seem like a
good choice either.

....

Do they have access to sunlight? You might consider a solar still.
http://www.epsea.org/stills.html

You're going to be asking for disaster if there is no local support
for whatever technology you try to install.

Anthony

 

[Charlie]

Charlie wrote:
...
...

Do they have access to sunlight? You might consider a solar still.
http://www.epsea.org/stills.html

You're going to be asking for disaster if there is no local support
for whatever technology you try to install.

Anthony

Doesn't AGM seem like a better solution than the added complexity of
maintaining flooded cell batteries - especially with the addition of a
solar still?

I suppose it's not if thermal runaway in AGM is a realistic threat -
that's what I'm still trying to find out.

To your final point, there is some support available, but in this
situation, I believe it is imperative to minimize end-user maintenance
because technical support will be difficult and expensive due to sparse
population (greater distances between installations).

Charlie

 

[[email protected]]

http://www.eirbyte.com/T105.html

The Trojan company says they'll last four to eight years. But they
don't say under what conditions that the battery will last this long.

Sure they do. Check out their "Lifetime Energy Units" graphs and tables.

Nick

 

[Anthony Matonak]

Lead acid batteries last about 200 charge/discharge cycles when cycled
every day with solar panels to 50% capacity.

Are you sure about this? If off-grid system batteries would
self-destruct after 200 cycles then people would have to
replace their batteries every year.

Anthony

 

[Anthony Matonak]

Depends on how deeply they are discharged and how they are constructed.
The bulk of lead acid batteries made are for starting automobiles and
aren't designed for deep discharged, but designed for cranking power.
So, in an application where they are deeply discharged daily, yeah,
they'd self-destruct in no time.

Seems unfair to compare state of the art, prototype sodium sulfur
batteries against automobile starting batteries. Clearly, the
comparison should be against state of the art, prototype deep cycle
lead acid batteries.

Anthony

 

[[email protected]]

http://www.creativeenergies.biz/products/docs/Trojan/Deep-Cycle.pdf

Note the total lack of numbers on the ordinate or abcissa...

I haven't looked lately, but they used to show actual numbers. The T-105
DOD vs #cyc curve they faxed me shows about 750 cycles at 100% DOD (LEU
= 473 kWh), 1000 at 70% (441), 1500 at 42% (397), 3000 at 20% (378), and
5500 at 10% (347), so fewer batteries with larger DODs optimize the LEU
and cost per kWh, even with a 0% interest rate and no shelf-aging.

Nick

 

[Landline]

So you are attempting to use totally misleading and wrong information in a
poor attempt to try and prop up some other type of battery.
To suggest user are using starting batteries for cars is misleading and
fraudulent in your case.
Why not tell the truth!!!

Have three locations (installed within days of each other) left on lead acid
that are discharged every day to 40% that have done 1,421 days and still
going strong. Now we use VRLA sealed and have batteries that are 1,240 days
and still going strong.

There are lies, damn lies and statistics.

 

[[email protected]]

... 20 cents per kWh is a lot less expensive than $8.00 per kWh -
which the bulk of lead-acid batteries deliver.

How do you figure that?

Nick

 

[Anthony Matonak]

How do you figure that?

He is figuring car batteries.

Anthony

 

[Anthony Matonak]

No I'm attempting to put relevant data out there to show why lead-acid
batteries (no matter how their plates are designed) won't ever deliver
power for less than about $1 per kWh.

You compared state of the art deep cycle sodium sulfur batteries
against car cranking batteries used as deep cycle batteries and you
don't see this as misleading?

Discharged 60% each day. That's cool. That suggests they're
super-batteries of some sort!

....<snip flood of irrelevant questions>...

It suggests that they are the proper battery for the job and that
ordinary deep cycle batteries last longer than 200 cycles.

But remember, they only last 200 days at 80% discharge recharge.
Typically. Even 'state of the art' batteries. The physics doesn't
change that much between cranking batteries and deep discharge
batteries.

I don't know about the physics but I do know that deep discharge
batteries are built very differently than car batteries.

So, for a $90 lead-acid battery like the T-105 with a capacity of 0.9
kWh being used to only 20% of its capacity, means that it stores and
retrieves 0.18 kWh each day. Multiply that by 1500 days and you have a
total amount of power 'handled' by the battery of; 270 kWh. That's
$0.33 per kWh for direct battery costs alone! With replacement every 5
years or so.

Hmm, he claimed 40% discharge, not 20%. So, assuming your other numbers
were correct, that would be $0.16 per kWh.

Now, it's not my job to do your homework for you but I was curious
enough to see just what good deep cycle batteries are like.

It's a bit of a long link, and might wrap, but I found this website.
http://store.altenergystore.com/Bat...-4-Ks-25Ps-4V-1350Ah-20Hr-Flood-L-Acid/p1640/

They sell the 4-KS-25-PS for $852.53 with free shipping on large orders.
It's a 4V battery with a 20 Hour capacity around 1350 for a total
capacity of about 5400 Watt-hours. It's warrantied for 10 years with
the first 3 years free replacement. The graphs on the webpage, while
very general, seem to indicate that at 50% depth of discharge it will
last at least 3000 cycles and at even 80% discharge it'll last nearly
2000 cycles. It seems even if you abuse it and discharge to 100% it'll
still outlast the 3 year free replacement terms.

Let's assume 50% dod or 2.7 kWh a cycle. Over 3000 cycles this would
amount to 8100 kWh. $852.53 / 8100 = $.105 (approximately).

That's nearly $0.10 per kWh for direct battery costs alone! With
replacement every 8 years or so. Of course, if you replace it under
10 years you get some of your money back (pro-rated).

Anthony

 

[[email protected]]

20 cents << 800 cents

How do you figure it?

I asked first. Where does the 800 cents come from?

Nick

 

[Landline]

William Kook you have a barrow to push, but you need to go to the kiddies
newsgroup, and not a group that people know what you are talking about.
How do I know how much the batteries are discharged everyday, they are
unmanned industrial monitoring and processing sites that do the same
function everyday. The new sites have larger battery banks that daily go to
30% DOD and expect minimum 2,500 cycles from the batteries, and expect 3,000
cycles - NOT 200. The company that supplies the batteries according to your
ridiculous statements will be out of business as they batteries carry a 5
year REPLACEMENT warranty if used to their guidelines.
You need to go and do some basic homework on the availability of quality
deep cycle lead acid purpose built batteries - NOT automotive cranking
batteries.

Yes William Kook, you are a fraud - go away and do some studying prior to
coming back.

--

Why? Exactly why do you say that?


I have, why don't you accept it? Do you realize that you are calling
me a liar? Why?

MAJOR diatribe snip!