Chub Cay Project
Zeiss Battery was contacted by a Solar Contractor who designed and installed an off-grid solar system on Chub Cay, Bahamas. After only six months, the homeowner experienced total battery failure. This system being located on one of the more remote islands of Bahamas, the homeowner was not connected to the grid, and nor did he want to rely on his generator when the sun isn’t shining. Who wants to live on an island paradise and have to deal with a noisy, dirty, smelly generator? Not to mention pay for all that fuel. So the owner relied on batteries (cells) for power at night to supply energy to the main house and two guest homes. The number one maintenance drivers on the solar energy system are the batteries, although they are a far more cost effective solution to running a generator or even paying $.50 kwh for being tied to an electricity grid (average price throughout the islands). This customer made the wise decision to make, store, and use all of his own energy. But what gives? How did this system become a nightmare and go upside down in a little over 6 months? There were a few factors that caused this but none is more important to battery performance then system integration and charging profile. Here’s how Zeiss Battery optimized the solar energy system and unleashed the power in the batteries.
Cell Shrinking Sulfation
Upon being contacted by the Solar Contractor for the Chub Cay project Zeiss surmised there was a sulfation issue. All lead acid cells (batteries) are subject to sulfation in as little as 24 hours of non use. The rate of self discharge of an AGM is about 3% per month (the higher the temperature the quicker the self discharge). So under the supposition the cells were manufactured in China and they took a boat ride to the main distribution center in the US, then to the battery distributor, then to the Solar Contractor, and then finally to Chub Cay. It’s safe to say that the batteries were sitting idle for 4-6 months doing nothing but self discharging and creating sulfation (#1 battery killer). Zeiss procured 6 new cells from the original battery distributor foreseeing that when he arrived a Chub Cay a few of the batteries would be unrecoverable. Zeiss tested the new cells and deemed they needed to be conditioned due to that they were only at 70% of capacity (sad truth is many battery manufactures ship their batteries at 80% capacity). It was safe to estimate that the original two strings of cells installed at Chub Cay were at about the same 70% of manufacturers said capacity. When Zeiss arrived at Chub Cay the cells were in fact performing at 25% capacity. The initial condition of the cells was evaluated with an impedance analyzer to see their current state of health, a load across cells (SAE test) and open circuit voltage. 44 cells were in good condition, however all suffered from deep, heavy and hard sulfation. In layman terms, sulfation just makes the cell smaller by limiting the area of reactive lead. 4 of the cells were deemed unrecoverable. Zeiss determined that the cells were good candidates for Impact Charger. Zeiss Battery uses the only impact charger recognized by the U.S. Navy. Zeiss treated the 44 cells removing sulfation, grid corrosion, and other impurities inside the battery, thus opening the battery up so it could accept a regular charge and restore its charge capacity.
Is your Smart Charger smart enough?
There was more to Chub Cay then just the state of charge of the batteries as they moved down the supply chain to the end user. There had to be another culprit, but what? Zeiss knowing that chargers are one of the major culprits of premature battery failure suspiciously eyed the top shelf Xantrex WX6048 inverter/smart charger. With Zeiss knowing the cells were sulfated from the beginning he knew they were about to open a whole other can of worms. Estimating that the cells were operating at about 75% capacity when they were installed the Xantrex WX6048 would not be able to break through the sulfation causing the cells to lose performance immediately. The problem starts when the smart charger does not compensate for the sulfation causing the charging profiles/charging algorithms to be completely out whack. The charger can’t operate properly when it thinks the cells are at 95-100% capacity when in fact they are at 70-75%. The result is chronic undercharging, and what does that cause? You guessed it more sulfation. The cells overall capacity went down hill rapidly from the estimated capacity of 70-75% when installed to the actual capacity of about 25% when Zeiss did the actual testing upon arrival in Chub Cay. Furthermore the property was outfitted with a powerful induction water pump to deliver water from the cistern and reverse osmosis system to the main house and guest cottages. When the water pump goes on the Xantrex WX6048 does not handle it well. Meaning if the inverter/charger is working hard (large load and charging at a high current) and when the pump goes on the Xantrex WX6048 bails on the bulk charge and goes right to absorption mode. This causes the cells to be undercharged even further, and causes more, you guessed it sulfation. Maybe that smart charger isn’t so smart! To be fair it’s not fully the Xantrex WX6048’s fault alone. Without the proper inputs for the charging profiles smart chargers never work as advertised, and some just don’t work at all. As you can see it becomes a vicious cycle of sulfation and ultimately causes premature cell failure.
There is a happy ending
Upon completing the Chub Cay project all systems were a go, and the owner couldn’t have been more thrilled. His solar energy system was running as designed, supplying his island home with quiet, green, and free energy. No more loud, smelly and expensive generator running through the night or when the sun wasn’t shinning. No more wondering if an expensive fuel delivery was going to be delivered on time. Not to mention being the envy of every home owner on the island. Zeiss was able to fully optimize the Chub Cay solar energy system first by use of the impact charger to condition the batteries, clear sulfation and balance the three strings of batteries. By balancing the 3 strings of batteries Zeiss was to keep all cells in the strings in family (cells discharge and charge at the same rate). The only changes Zeiss made to the actual system was to the Xantrex’s charging profile to properly match the cells needs and to add a finishing charger to pick up the slack when the Xantrex gets overloaded and decides to bail. With a semi-annual maintenance program from Zeiss Battery, the Chub Cay solar energy system will run day and night like a finely oiled machine for years to come, minus the oil and fuel of course.
Closing Thoughts
Just because AGM and Gel battery manufactures put a sticker on there product saying “maintenance free” do not believe it. Nothing could be further from the truth. All that really means is you don’t have to add water to the cells. All batteries in a solar energy system should under go some sort of semi-annual maintenance to keep them doing there job year after year. When procuring cells have Zeiss perform tests for sulfation, cell dry out, and impedance in order to assure the state of health of the cell, and if necessary condition said cells. At Zeiss Battery we have the solutions to ensure your batteries have a long life and are always mission ready. Nobody knows batteries like Zeiss.
