Battery survey
Ocean Navigator|November - December 2020
We asked a group of voyagers about their vessel’s batteries and their future battery plans

What type of battery setup might make sense for your voyaging needs? We reached out to a selection of active liveaboard voyagers to get a sense of what they are using to power their vessels. Here are their answers to our survey questions.

Jon and Sue Hacking

Jon Hacking has lived aboard the Wauquiez Kronos 45 catamaran Ocelot with his wife and fellow voyager Sue since 2001. Their travels took them through the eastern and southern Caribbean, through Panama, across the Pacific, through Southeast Asia, and across the North Indian Ocean to South Africa in 2007. In 2009, they sailed back across the Indian and have been rattling around Southeast Asia ever since. They document their travels on their website (not a blog) at svOcelot.com, and their information for other cruisers is at svocelot.com/ Cruise_Info/cruising_info. htm.

Ocean Navigator: What type of batteries do you have installed on your boat (i.e., lead-acid flooded cell, gel cell, AGM, or Li-ion or other)? Jon Hacking: We started with gels but have now moved to lithium iron phosphate (LiFePO4). When we bought Ocelot in 2001, she had gel cell batteries but they were shot. So, we paid $500 for 660Ah (three 8D batteries) of “factory-second” gels. Apparently, they’d been on the factory floor too long to sell as new. These lasted well for us, but we replaced them seven years later in South Africa, having to pay $3,000 for 660Ah of top quality Sonnenschein gels.

In theory, these Sonnenschein gels should have lasted 2,500 cycles, almost seven years, if cycled down to 50 percent. We only ever cycled them down about 20 percent (130Ah) and usually much less than that (typically 80Ah/night, mostly from our fridge/ freezer), so they should have lasted even longer. When they were eight years old in 2016, however, while motoring across the South China Sea from Singapore to Borneo, the engine started showing low oil pressure. I switched over to the port engine, but the alternator on that engine only had a “dumb” regulator. I’d set the voltage to 13.8v, and that had always been fine, but the regulator didn’t have a temperature sensor. There were 8 amps going into the batteries, but I assumed that number would go down and all would be fine.

Wrong! 8 amps at 12v is 100W, which made the batteries slightly warmer, which caused them to accept more current, which made them warmer, which caused them to accept even more current, etc. It’s called “thermal runaway” and is not talked about much, but it’s one reason why all lead-acid batteries should have temperature sensors connected to their charging circuits. When I checked an hour later, I had 45A going into our already full batteries, and they were too hot to hold my hand against. In one hour of overcharging, we’d ruined 660Ah of expensive gel batteries, and they only had about 240Ah of capacity left. Lesson learned: Always use a temperature sensor when charging lead-acid batteries.

While researching what to replace my cooked gels with (from the back of nowhere in Indonesia), I came across some Chinese LiFePO4 batteries that we could get delivered to us. We’d been looking at LiFePO4 for a while, but still considered them “bleeding-edge” and not yet suitable for a cruising boat, but some of the specs were compelling. Discharging lead-acid batteries below 50 percent will start doing permanent damage to them, so our previous 660Ah gels really only had 330Ah of usable capacity. LiFePO4 batteries can be discharged down to 10 percent without ill effects, so we’d only need a much smaller bank. So, they’re smaller, lighter, and they claimed 5,000 cycles, or over 13 years lifetime. So, in 2017, we bought 300Ah (270Ah usable capacity) of LiFePO4 batteries manufactured by the Chinese company Hi-Power, which now appears defunct.

ON: How satisfied are you with your battery setup?

JH: Not very, but some of that is my own fault. Initially, we loved our LiFePO4s! They were considerably smaller and much lighter than our gels. They charged up really quickly, and the voltage hardly dropped at all as they discharged. Amazingly flat charge/ discharge curves, and they sucked up as much current as we could throw at them. Our Blue Sky Energy SB50 Maximum Power Point Tracking (MPPT) solar controller was flexible enough that I could reset the charge- and float-points, so that was easy. I’d recently installed new (and very smart) external alternator regulators. They were both fully programmable and had a LiFePO4 setting. Perhaps more important, they connected to our amp-hour shunt to sense the current going into the battery, so they knew exactly when the batteries were full and when it was time to switch down to Float. We never plug into shore power, so I didn’t worry about our ancient Heart 1500W inverter/charger. I checked each cell’s voltage periodically. They were always within 0.01v of each other, so eventually I stopped checking.

Our new LiFePO4 batteries came with an expensive Batrium Battery Management System (BMS) that never worked well and eventually corroded into oblivion. Our battery compartment is under the helm and therefore protected — although certainly exposed to salt air — and the BMS board wasn’t sealed to protect it. My research at the time showed that the LiFePO4s would last longer if only charged to 13.9v. This is true to a point, but LiFePO4 cells were (and are) still new enough that it’s very hard to make them absolutely identical, especially in internal resistance. Since the cells aren’t exactly the same, they don’t accept the same amount of charge, nor do they discharge at the same rate, so the voltage across each cell tends to drift a bit. Therefore, LiFePO4 cells need to be balanced periodically, and this has to happen at higher voltages, typically 14.2 to 14.4v. Since our cells never got to those elevated voltages, the BMS never triggered a balance cycle, and after two and a half years of excellent performance, one cell drifted low — while we had friends on board in a storm. Of course. This eventually triggered an alarm, but not before some possibly permanent damage was done. The Australian dealer that we bought the LiFePO4s from said that we only needed to rebalance the cells.

Eventually, we received and installed some active balance modules from Electric Car Parts Company. I programmed our MPPTs to bring the batteries up to 14.0v for a couple of hours each day to let the balance modules do their thing. After a week, I’d crank the voltage up by 0.1v and let them sit there for a week or so. I eventually got them up to 14.4v (3.6v/cell), which is the maximum recommended charging voltage for these LiFePO4 batteries. As I write this, we’re still using these cells, but I haven’t done a complete discharge test, so I don’t know how much real capacity they have left. My gut tells me not to trust them too far.

ON: What is your usual recharging routine?

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