Are auto-batteries suitable to wind or solar charging applications?

[Usman]

Hello everybody,

I would like stir a very basic argument here i.e. suitability of automotive batteries in wind charging applications, especially in hot climate.

I know that auto batteries are not recommended in deep charging/discharging applications. However, I recently meat someone working for BP Solar's engineering department and he dismissed any such verdicts. He said that auto batteries (flooded) can very well operate as good as deep cycle batteries, at ;least for 12-18 months, as long as they are not deeply discharged or overcharged (in other words are well taken as their expensive deep cycle counterparts),after then they would need replacement. I suppose if auto lead-acid could be used as efficient as lead-Acid deep cycle batteries for 12-18 months, they would give a better value for money.

On the other hand, I have heard people say that automotive batteries are not suitable in any sense: Main reasons:

1. -They discharge very quickly!
   
2. -They last only a month or two!
   
3. -They wouldn't hold up charge and would lose 50% of charging amps- no where etc.
   
   

I have no practical experience with using auto-batteries vs. deep cycle batteries, but suppose such claims against auto-batteries are not valid.

I would like seek advise on this issue whether I could use auto batteries in my application, (wind/solar hybrid 3KW/48V), running lighting, 1 kW induction load; how long could I realistically expect these to perform satisfactorily before replacement is required?

Thanks, Usman.

[richhagen]

I would not use an auto battery for an re application if one needed more than a few percent of discharge from the battery.  They have plates designed to maximize surface area for starting amps, and are not well suited for repeated deep discharging.  I have, however used a free starter/lighting/ignition battery for a small solar lighting project that has been in place now for quite a few years.  It does not discharge more than a couple of percent before the small lights go off.  

See the battery FAQ from this site here:  http://www.otherpower.com/otherpower_battery.html

Rich

[wooferhound]

I used a plain old car battery on a 12 watt solar system. Used a small incandescent bulb on it for about 3 hours every night. This is before I discovered the Fieldlines.com Forums. Well I totally abused that battery for 3 years before it became unusable. In the end I had a 12vdc fluorescent light on it for about 4 hours every other night.

[ghurd]

Maybe this is a rant.

Was the "someone working for BP Solar's engineering department" the janitor, the webmaster, or in the PR dept?

Remember, BP makes PVs, not batteries.  If they want to test PVs, they will use new batteries to limit errors.

Main Reasons #1, 2, and 3.

No on #1.  

Longer than a month or 2 for #2.

For #3, I can't even guess where that came from.

I'm not sure what you are looking for, or what a hybrid 3KW system actually means.

And "Lighting and a 1KW inductive load" don't tell anything.

A wind system battery, around here, would be subjected to severe discharge conditions, or the battery bank would have to be crazy oversized.

I do have some practical experience.

A small PV and a larger CCA lawn tractor starting battery ($30?) lasted a few months, only charging a cell phone.  The same setup has run for a couple years with a 7.2AH SLA ($25).

A $40 (on sale at the end of boating season) Wally-World 85AH deep cycle and a 53W PV has run a copier in an off-grid school for 3 years, in a less than great insolation area.  I doubt a $100 starting battery would have lasted a year.

Or a 7AH SLA running a sonar (fish-finder) for 8 years, though I have reservations about it this year.  No signs of failing, simply 8 years is a very old battery.

And a highly abused pair of Sam's Club 6V golf cart batteries ($63 each/$126 a pair) is maybe 4~5 years old, run below 12.0V at least once a week, occasionally go a week or more with never being up to 12.4V including surface charge, sometimes go a week below 12.0V, still work fine, and there are no plans to replace them at this time.

No offence to the BP dude, but has he used batteries for years, charging them with wind or solar?

Almost anyone who has will not recommend a starting battery for a "Hybrid 3KW" system.

The factory battery in my truck was subject to his conditions of well taken care of, and it lasted ~7 years, IIRC.  And it was garaged for a year with a chronically undercharged battery.  The 12 to 18 month thing sounds like the battery warranty, which is void under RE conditions.

Rich may be talking about an LED light.

Woof is talking about a few watts.

You mention 1KW, or 100+X more...  Is 100 car batteries cheaper than good batteries?

They are simply not the same.

How much apple juice can you get from an orange?

G-

[Flux]

True deep discharge batteries are the traction type with massive plates and they will stand cycling for years at about 80% discharge. They have a lot of self discharge and cost an arm and a leg.

Other batteries are a compromise and some manufacturers make the compromise in different ways.

To reduce size and weight, the modern auto battery has very thin plates to give a high discharge current for a short time, with no significant overall energy removal.

The most compromised of these will only give a few cycles of discharge to about 20%.

So called leisure ( RE, Marine ) batteries have thicker and more robust plates but the worst examples of these are probably no better than the best examples of auto batteries.

I suspect there is more difference in the brand names than in the actual type.

Some starting batteries intended for heavy use ( Caterpillar for one) actually survive RE duty much better than cheap nasty so called leisure batteries.

Unfortunately unless you know someone who has tried these various types you are really at a loss to know what is good and bad.

Over the years I have used car batteries for battery operated amplifiers in PA systems and found them more cost effective than leisure batteries, but the average currents are low. If you run high currents to inverters you may not find them much use unless you choose the better makes.

In the end what you pay for the battery may be a better indication of its possible life than its intended use description. The weight is also a significant indicator. Two batteries with identical claimed spec but totally different weight will not behave the same. The heavy one with more material will be more expensive and will give better service.

If you must try auto batteries than avoid small ones ( that seems true for any battery) and choose ones intended for arduous use ( tractors,trucks, with heavy diesel engines).

I suspect that if you choose wisely the cost per discharge cycle in the long run will not be much different. You will need more auto batteries for the same duty and need to replace them more often, if they come cheap enough it may pay off.

Flux

[TomW]

ghurd;

Was the "someone working for BP Solar's engineering department" the janitor, the webmaster, or in the PR dept?

Darned good point! If there is one thing I fear it is people who "know" facts that just ain't so.

Lots of folks like to play "expert" and, like rumors from a "highly placed source", without documentation or more specific information, I tend to discount such statements as fertilizer from intact male cattle.

Mainly tho I wonder at people who will spend several hundred dollars on panels or a turbine then cheapskate the batteries or tower / mountings. They must have never heard the ditty "penny wise and pound foolish".

Your point about the difference between toys and real power production is valid, also.

In my opinion, you should use what you have or can get and accept the fact that not everyone can afford the perfect system components. My next battery purchase will be fork truck [traction] batteries and I will just eat the self discharge in favor of long life. Unless a load of nickel iron batteries fall off a truck in my yard.

WRT this particular post I felt it was a troll because no specifics are mentioned and we have covered this area at least a few hundred times with the commonly accepted consensus that automotive batteries are a poor value.

One mans troll is another mans stimulating discussion so here it remains.

Cheers.

TomW

[wooferhound]

Here is Too Much information about taking care of Batteries

http://www.batterystuff.com/tutorial_battery.html

http://www.backwoodshome.com/articles2/yago95.html

http://72.14.209.104/search?q=cache:HMvi3rXKQxUJ:www.wholesalesolar.com/pdf.folder/Download%2520fold
er/battery_maint.pdf

http://www.oasismontana.com/batteries.html

http://www.batteryuniversity.com/partone-21.htm

http://www.rebelwolf.com/downloads/BattMan.pdf

[mtbandy]

Just from experience here...

Back in 2001 and 2002 I bought 2 car batteries from the local scrappers, second hand ones taken from cars. They save the batteries which have been recently replaced, so they were both of similar age. This was way before I knew anything about what I was doing, and the batteries were to power tent lighting and a small inverter running a TV and various other loads. I used to go camping with these batteries, and completely flatten them every time. The small cheapo one totally failed about a year later, it wouldn't hold a charge. However, the other one is a good quality 'Lucas' brand, 59Ah. It is still going strong today after all this abuse! Since 2002 it has been out with me several times in each year to camps, and it has also been borrowed a few times now along with the little 150w inverter, taken away and flattened, returned to me a week later etc etc... but the point is it's still working quite well. So I reckon if you can obtain good quality large car batteries cheaply, as in cheaper than anything else, then go for it! I bet there is quite a bit of overlap between top end car batteries, and cheaper 'leasure' batteries.

It'll be going away with me again in a couple of weeks, and yes it'll be flattened again! (but only so that I don't have to discharge one of my nice SLA batteries too much!)

[luv2weld]

Hey wooferhound,

Just to make sure we overload their brain, here are a few more---

http://www.sandia.gov/pv/docs/BattIntro.htm

http://www.trojan-battery.com/Tech-Support/BatteryMaintenance.aspx

http://www.otherpower.com/otherpower_battery.html

http://www.batteryfaq.org

Ralph

[Usman]

I agree with mtbandy over most of the other comments, as the practical experience outsmarts any theoretical one, in my opinion. I have seen guys in desert, running up televisions, fluorescent lights and swamp coolers from 200Ah Truck batteries, and they last over years of abuse and still sell out well as scrap. I suppose anything to do with automotive industry is well-built and low-priced, due to mega high volumes.

I respect all the theory in place, but the fact that auto batteries are as bad as widely understood, doesn't seem to hold up to me. I think if auto batteries are taken care of in a similar manner to that of RE batteries, i.e. temperature controlled, max. 60% discharge and 90% charge, equalized, desulphured, period check-ups for low fluid level etc, they would survive as well as any other RE batteries. The capital investment in RE batteries is much more than auto batteries.

I wish if there was a low-cost supplier of RE batteries or if auto-industry starts to use them for their hybrid applications, so the price could go down.

I think I will use a combination of both (separately) - two turbines charging two banks, one RE and the other one auto, and would give a verdict, perhaps a few years from today.

[spinningmagnets]

I am always frustrated when the proponent of anything excitedly promotes the benefits of some new "thing", but fails to describe some of its weaknesses. When I read about  the latest advance in technology in "Popular Science", I always wonder why the new gizmo isn't sweeping the nation, and it usually just takes a little reading to find out. Not that its weakness isn't solvable, but I'd just like to know up front.

A while back, I wondered why electric car conversions weren't more popular. They are a viable option, especially as a second car for the family member that drives the fewest miles each day (I drive 30 minutes each way, my wife drives 5 minutes)

You may eventually use some exotic future battery like Li-ion or Li-po, but the cost of the conversion ($10,000ish) means you'll probably use lead-acids the first time around.

The power/weight ratio of lead-acids mean you'll probably settle for less range initially than you'd like, but at least you'll be rollin in an EV.

The big difference in car starter batteries and deep-cycle batteries is the thickness of the plates. Every time the battery is deep-cycled, some of the lead melts away. The battery eventually providing slightly less voltage is the result of holes forming in the plates, so there are fewer plate square inches to provide for the chemical reaction.

The longer you leave the battery in a discharged state, the harder it is to pry the sulphate coating off the plates. Also, the longer you have to put charging current into the battery to reverse the chemical imbalance, the more resistance you'll get, and the more heat you'll put into it, with some of the current electrolyzing the water into hydrogen (don't smoke next to a charging battery!).

I have read about "pulsing" chargers that can bring some of the life back into old "long-discharged" batteries (sulphates deeply imbedded) and also chemicals that can also reverse a small portion of sulphated battery plates (EDTA?)

Lead-acid provides a certain amount of volts per square inch of plate that is exposed to the electrolyte. Plates are attached together in 12 volt series sets, then more 12-volt sets are attached together in parallel to get the maximun Amps in a small package. Big 6-volt "deep-cycle" golf cart batteries have plates as thick as your finger. A 12-volt car starter battery has plates that are barely thicker than a manila folder. The plates usually have a grid pattern of dimples to increase surface area. Drain a couple of dead batteries (wear eye protection and gloves!) neutralize the electrolyte with baking soda (slowly, and with caution) then bust the housing open.

Buy the thickest plates you can afford, buy enough batteries for the load you expect so that you'll only dip into it less than 50%, and charge them full up right away.

If you buy twice as many batteries, they may last 4 times as long.

Instead of going cheap on the size of the battery pack, cut way back on your usage. An LCD TV uses much less than a common CRT, Compact fluorescents/LEDS are much better than regular light bulbs, common fridges and A/C use a lotta Watts, etc...