When we think of batteries used
for a renewable
energy system the three that first come to mind are golf cart (GC),
L-16 and heavy duty industrial batteries. Of these three
different styles the L-16 batteries are probably the most promoted and
used of the three.
Though available in gel and AGM they are normally flooded lead-acid and the amp hour capacity at the 20 hour rate usually will range between 350 and 420. They are commonly referred to as floor scrubber batteries but can also be found with "solar" and "Alternative Energy" in their title descriptions.
The L-16 is a compelling battery for use in a renewable energy system. They have several positive traits that put them a comfortable spot right in between the golf cart (GC) and forklift. However, like most other battery styles, their initial purpose was not for storing solar or wind energy though you may get that impression by the way they are promoted. They do fit into the renewable energy niche but you need to really take a hard look at what you getting for your money.
What makes them attractive for such a use is their size, storage capacity and perceived low initial price. At a weight of between 100 and 120 pounds, though heavy, they can be easily move by one or two people without the use of any special equipment.
Dimensionally, they are about the same width and length as the golf cart but just under twice the height. When compared to a golf cart battery, the L-16 gives you approximately 70 to 80 percent more amp hour capacity in the same floor space. The price is such that compared to the GC they are approximately 50 percent more expensive per amp hour capacity but are close in price when compared to the much heavier duty industrial style.
The attraction for L-16 batteries is the fact that you can add up your amp hour capacity quicker which results in fewer parallel connections. For example, three banks of 220 AH GC's will result in a total 660 AH capacity where as two banks of 390 AH L-16's will offer a 780 AH capacity. With the L-16 you have fewer cables and better Peukert Effect since you are drawing off a larger AH capacity. This results in an overall smaller percentage draw which will effectively give the L-16 bank a few more AH's of capacity in comparison. You also need less floor space to house L-16 batteries.
The life span of the two will be variable. The numbers that are generally used to describe life expectancy are just that, general, but in an attempt to make comparisons we will use the ones most commonly accepted. The golf cart has a predicted life span of 3-5 years while the L-16 is 4-7 years. If the two batteries are discharged and treated in a similar manner, the L-16 will have a longer life due to the thicker positive plates.
One thing that works against the L-16, in this case, is the cost and availability. The golf cart battery is much more widely available than an L-16. Even the big warehouse clubs carry the 6 volt golf cart battery (though it may be difficult to learn who actually makes it). Also, you typically get more amp hour capacity for your money in the golf battery. If you purchase a Trojan brand golf cart the costs will probably be comparable to the L-16 but with a brand like Interstate or U.S. Battery. the cost can be up to 50 percent less per service amp hour.
The best way to find out how the GC and L-16 compares in your area is to get local prices and figure out the cost per amp hour over the expected service life. As a general guide, the golf cart typically is good for 500 discharge cycles of 80 percent DOD while the L-16 is 700 cycles. Though it takes a little work, you can get a real dollar figure of the cost based on current prices.
The industrial battery is typically referred to as a "forklift" battery. In the renewable energy field you will find there are batteries marketed specifically for off-grid systems. The most popular one in this category is the Solar-One.
There is a big difference between forklift and L-16 batteries. Where as each L-16 comes as three 2 volt cells internally wired in series to supply 6 volts, the forklift will be 6, 12 or 24 individual 2 volt cells all packaged together in a metal housing. This usually makes for a heavy package especially if you choose a single 48 volt bank, which can weigh over 3,000 pounds. For most of us, moving that kind of weight requires heavy equipment, and once in place they tend to not get rearranged very often. It may not always be the case that you have to move the whole bank as one piece since some have the option of removing the individual cells from the case then reinstalling them.
The cost per amp hour capacity is where the comparison gets interesting. The Solar-One is 50 percent more expensive than the L-16 per amp hour, but should have three times the life with a published 2100 cycles of 80 percent DOD . If you go with a general forklift brand, the price will be the same or less in comparison to the L-16, but again with a much higher life expectancy.
L-16 batteries have found their way into the heart of many renewable energy systems. They do have a certain appeal based on general appearance and perception. They can be arranged into an impressive looking battery bank that appear substantial compared to the smaller golf cart style but still remain managable for the owner/operator.
While the L-16 style is attractive, we have to wonder if you are really getting your monies worth. This is what you will typically find - golf cart batteries are described as good for energy storage but the L-16 is the way to go for the off-grid battery solution. We have to wonder if installers like them because they are easier to aquire and handle than the industrial battery but look better than a pile of golf cart batteries sitting on the floor.
Also remember that not everyone selling renewable energy products have practical experience with the products they promote. This makes it tough for someone new to the RE scene to get a handle on the difference between what works best and what a saleman wants to sell you.
We place L-16 batteries right in the middle of the
issue. Understanding the strenghts and weakness of each type
battery will help you navigate this part of your renewable system and
get what will work best for you. We also realize that
available space and budgets are a factor in making the decision
regarding your battery bank. It is just our opinion that if
you have a limited budget, the golf cart battery seems to give you the
most bang for your buck but if the cash is available the industrial
forklift style battery is the most cost effective way to go.
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Installed a Trace 3500 inverter, and 12 Interstate L16 batteries in 1999 for Y2K. Just recently had to discard four of the L 16's and am now in the position …
This article is good insofar as it goes, but it leaves a couple of important points out. The life of batteries can be extended by reducing the cycle discharge …
Do you currently own or have had first hand experience with this turbine? We would love to here about it. Voicing your opinion will help others choose one that's best for them.
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Jonathan Cole, Founder, Light on the Earth Systems Not rated yet