Now that we have upgraded our battery bank for long life, we need to be able to monitor it, so we know how many amp hours we are depositing, and how many we are withdrawing. Today we are installing a FLEXnet DC to replace our Trimetric. This will allow us to monitor the performance of our battery bank and wind turbine with the same display we use to monitor our solar panels, and inverter. This unit monitors the power to and from the batteries on three current shunts, one on the pv charge controller, one on the inverter, and one on the wind turbine.
Archive for September, 2008
The Quest for maximum battery life continues
A quick recap. The battery bank consists of 8 L-16′s, which are a 6v, 420ah battery, in two parallel 4 in series strings. This gives me 24v @ 840ah.
After cross-tying (massively paralleling) my battery bank, by connecting the positive posts across parallel banks, it was time for more drastic measures.
I installed a second hand BattEQ that originally came from http://www.abrahamsolar.com, but it wasn’t functional. One phone call, and 4 days later, a new one from http://www.smartsparkenergy.com arrived, and is now installed and functional. The BattEQ equalizes the charge and discharge to each battery in the string, and the cross tie cables distribute that functionality to the second string.
The next item on the agenda was a pulse desulphater, from http://www.pulsetech.net. The PowerPulse extends battery life by minimizing the size of the lead sulfate crystals. Again, because of the cross-tie cables, the effect is distributed across both strings. Installed and functional.
The next item I will evaluate is an automatic watering/degassing system, to prevent spills and corrosion, and prevent water loss. These steps should ensure I get maximum life from my battery bank.
By Mick Abraham
Solar power has been romanticized as a “green technology”, but truly in-dependent power also includes lots of “black technology”. An off-grid energy system may have clean non-polluting solar modules smiling at the sun, but it also includes heavy chemical batteries containing toxic substances like lead and sulfuric acid. Batteries are the dark industrial underbelly of off-grid renewable energy systems.
I’ve had a love/hate relationship with deep cycle batteries ever since buying my first one in 1984. Chemical batteries will remain essential to in-dependent energy for many years to come, but they also represent the number one problem area. Performance gradually degrades in ways that are barely noticeable at first, but the pack eventually reaches an “avalanche point” where the battery capacity falls off a cliff. This causes a crisis for the system owner which requires emergency money transfusions to their battery vendor.
Batteries are so problematic that those who rely on them can get discouraged. I’ve become acquainted with many “off gridders” as customers who later developed into friends, so I know a bit about their frustrations. Many have reached the point of selling their homes, bringing in costly line extensions from the grid, and taking other drastic measures. To me, each of these events represented a failure for myself, for the off-grid energy industry, and for its technology. Watching my friends and customers endure their battery disappointments, I gradually developed a personal quest to learn more about batteries and to look for ways to reduce these problems. My quest has now been under way for more than ten years, and it has changed my alternate energy business more than once.
In 1997 I introduced the PowerPulse® electronic sulfation dissolver to the alternate energy world, and I’ve shipped over 7,000 of those units since that time. Since independent power systems sometimes can’t recharge their batteries promptly, lead sulfate compounds can develop a covalent bond to the battery plates which cannot be reversed with normal recharge methods. The sulfate busters use a well understood means to resonate and dissolve the crystal form of lead sulfate.
PowerPulse (and the competing clones which soon followed) is now a common battery enhancement, but battery longevity has continued to disappoint. Even my PowerPulse customers still come up against battery surprises. It’s also not easy to confirm what the pulse device is doing or if it’s still working. I’m a believer but others have attacked this product category as “snake oil”.
In 2005, I began testing a new battery enhancement device which may prove more significant than the sulfate dissolver. This is an automatic battery balancer called BattEQ™. The product is based on research work at the University of Illinois. SmartSpark® Energy Systems, Inc. has licensed this and other patents, and www.abrahamsolar.com serves as a distributor & factory rep for Smart Spark.
SSES builds several different versions of their equalizer. The first one that I rolled out is optimized for 6-volt batteries, such as the popular “L-16 floor scrubber” or “T-105 golf cart” batteries. Other equalizers balance to the 12 volt increment for different type battery banks.
BattEQ rapidly switches a bank of energy storing capacitors from one increment of the battery string to the next. When the capacitors encounter a segment which exhibits voltage above the average, a bit of energy is absorbed. When the caps encounter a segment which is below the average voltage, they dump their stored energy. The result is a “flywheel effect”; each segment tracks the others with nearly identical voltage—with important effects on battery health and performance.
Alpha Telecomm has also licensed the same “flying capacitor” technology from the university; search www.alpha.com for the AlphaGuard™. In some ways, AlphaGuard is more “civilized” than BattEQ, but the balancer bandwidth with AlphaGuard is too low for house sized battery banks. BattEQ pumps more energy per dollar than any other balancer that I’ve seen.
Voltmeter tests are an easy way to confirm equalizer function; if a clamp style DC ammeter is available, one can clip around each balancer lead to read the energy throughput. The amperage readings are typically highest when the balancer is first installed; even on brand new batteries off the same shipping pallet, I never fail to observe a few amps of energy transfer.
Combining all my various prior efforts, my gleam in the eye is pack level sulfate dissolving (easy & relatively cheap), combined with balance at the level of individual two volt cells. The last part of this is much more of a challenge, so my next step is to just try for cell level information.
I’ve now got the ball rolling on a special version of the PakTrakr, to capture the voltage of each individual cell in a battery string (this assumes that one has access to the individual cell terminals, of course). www.paktrakr.com shows their standard offering (which I can also supply for battery users who have 6 volt or 12 volt monoblocs). I plan to post a flyer on the two volt version on my Top Floor before long. The Paktrakr products should particularly appeal to battery professionals who want a simple way to highlight battery balance issues for their customers.
The elephant in the room is this: since there is no BattEQ for individual two volt cells, what actions can we take if PakTrakr points up a single weak cell? I’ve got varying ideas in mind…of varying quality. As mentioned above, this won’t be easy but I do think it is worth working on and the next thing to do is get cell level data.
I extend my thanks to green-trust.org for publishing this article, and I hope to see fewer battery problems down the road. Charge!
Mick Abraham, Proprietor
Voice: 800-222-7242 or 970-731-4675
Skype username: abrahamsolar
Abraham Solar Equipment
124 Creekside Place
Pagosa Springs, CO 81147
In larger battery banks, where you have multiple series – parallel strings of batteries, you run the risk of some batteries getting more “used” than others, and this degrades your pack performance. A simple way to reduce this effect is to cross-tie your batteries. This is a rarely used but important method of getting extreme life out of your expensive batteries. Here is an example:
The dotted lines are the cross tie cables. It’s also important to make sure your cables are heavy enough, that you are not losing power as heat through resistance. If you have caps on your batteries, not maintenance free, check the water levels once a month and top them off during charging. Do not overflow. Next we will discuss pulse desulfators as another method of extending the life of your batteries. Stay tuned.