Chapter 1: The Lithium Revolution Has Begun
(Reader Advisory: If you are only here for pure tech, you might want to skip to the next chapter.)
That most ominous of clocks was ticking down. It was a clock consisting of months, rather than hours, but the time it took to tick its way to the end felt far, far shorter.
Every year, as though on schedule, our 180Ah lead acid battery would fall over dead. Although I had bought the lead acid based on its guarantee period of three years, this was the third time I’d had to replace it in just that time. Nervously, I had started looking for another solution — traction batteries, AGM, just anything different to this hopeless lead acid truck battery.
We use very little power — 20-40 Ah per day if we are sensible — and our 200W solar array typically floats us through half of this, with the remainder recharging by midday the next day. It would seem that this system would be great in summer, but in truth it only worked in theory. Why?
Each cycle, large loads would inevitably kick the battery in the guts.
It never had usable voltage below 20-40Ah.
The way lead acid charges means that the amperage is strangled in the last 10% of capacity.
I noticed that as the capacity dropped off each cycle, the smart meter was having to recalibrate each time.
This was all very depressing. I started to see the lead acid as a huge, black, chemical dead weight. It lurked in the back of the engine bay, weighing more than my Volvo Penta, and I dreaded the day I would have to summon my inner Viking to haul it out again!
Then it happened. I typically waste way too much time trawling the private ads for unloved and rejected boat parts, but this time it payed off. Facebook Market’s algorithm worked its magic, and there, shining like the holy grail, was a Lifos battery!
I looked at it sideways, upside down, backwards, its neon green somehow slowly drawing me in. Then I saw the price tag. No. Obviously, no. It’s just a 68Ah battery, how could it cost so much? No.
I made a coffee and tried to forget about it. That night, however, I started a process I call “expert for a day, fool for the rest of a lifetime.” When I want to find out about something new, I’m relentless — I will dive into the deepest depths of Google to search out any scrap of information.
At first, I was a skeptic.
Lithium batteries are dangerous, right?
Lithium explodes and will burn through a plastic hull, right?
They require specialist chargers, right?
All my brand new, carefully assembled solar systems, my wind generator, alternators, shore charger, none of them would work with a lithium battery…right?
But then I found an amazing resource, http://www.marinehowto.com, and learnt a few things. First of all, there is such a thing as a lithium ion battery, but that’s not the same as lithium iron phosphate.
And lithium iron phosphate doesn’t explode?
It’s self extinguishing?
And non toxic?
Ah, but you need to build a special thing called a BMU (battery management unit). Oh, OK, that puts me off. And, yes, you definitely need lithium specialist chargers. Oh well, that kills it then. And, oh my God — the expense!
Then I found the Sterling tests. Day after day, the testers would fully charge and discharge this LiFePo4 battery and look for fade. Typically, a lead acid battery will exponentially curve from about 50% of its stated capacity (if it’s a really really good one), eventually becoming a pointless object that will never take a charge again, leaving you staring unhappily at the £10 the scrap yard will give you for the lead.
Now I watched in awe as other cruisers built cells, made management systems, and installed unfathomably huge capacity LiFePo4 systems to their boats, all of which costed slightly less than twice the purchase cost of our entire ancient catamaran!
I tried to sleep.
I called Lifos the next morning, armed to the teeth with questions so keen and cutting that, had they been on the subject of, say, Brexit or NHS funding, they would have sunk even the most stalwart Conservative politician.
“Wait, what? You mean I CAN use my normal chargers? Are you sure? I know it’s early, but…oh OK. Wait…I can let the battery sit at any percentage of capacity, and it will be OK? Even at 100%? Even at 0%? Oh, I see. But it won’t really get to 0% because the onboard BMU will turn it off? And I can’t overcharge it? And I can’t overload it? And I can’t damage it at all? And it has a Bluetooth interface-amperage, percentage, voltage, wattage, charge state and temperature gauge built in? And it weighs just 7kg? And, based on my usage, it would actually give us enough power, even more than replacing my 180Ah lead acid. (Note: the company I bought the lead acid from actually promised 120Ah, but I never got past 40Ah.) And, going by those specs, the Lifos would theoretically last 20 years!?! (OK, the 20 years applies if I don’t often go past 50%.) And, it has constant voltage? No sag? And no fade? And wait, what? It takes in 40A constantly from flat to full? So does that mean that Ohms law is finally applicable? It’s bench tested to 2750 cycles to 100%? 5 year guarantee? Uh……thanks for your help… Oh, and I can call back anytime…? Oh um..thanks…”
I tried to take it all in. I’m a huge sceptic — surely, this was just sales banter? Nope. Even the pioneers who built their own lithium iron phosphate systems 9 years ago have observed no loss in capacity!
Ok, the price was still worrying: a huge, ugly figure I can’t even mention here. Fate smiled on me that day, though, since the battery I had found on Facebook Marketplace had been won by an old couple who just didn’t want it. It was remarkably cheaper than a new one, still boxed, never opened, except, well, it was a 6hr round trip away.
Was that the last nail in the coffin? I looked up the hopelessly long trip distance on Google Maps and sheepishly asked Sarah, “Hey…um…I know we don’t need a battery right now and… err…I know we don’t have money to burn, but…uh…how do you feel about spending £XXX on a tiny weird battery that, if I’ve done my sums and research right, and if it lives up to the sales pitch, might keep us from ever having to worry about the battery ever again?”
“Sure,” she said. “Sounds great!”
“It mean, it’s a 6hr road trip, btw.”
I sent a message to the Facebook couple. They instantly knocked £150 off their already very fair price! I bolted the broken starter motor back on our van, and we bolted to Nottingham!
Chapter 2: Reality
(If you’re looking for the tech stuff, you have arrived.)
The Lifos V2 is a new generation of onboard BMU LiFePo4 batteries. They will charge from any standard Lead Acid charger.
There are a few things to be aware of:
The maximum input of the 68Ah battery is 40A. It’s about double that for the newer 110Ah version.
The battery can suddenly disconnect to 0V to protect itself.
It cannot be used as a starter battery.
This was of concern in my set up as the battery on our boat had been set up as a starter/leisure battery, hence its high capacity. I discovered the boat had never been set up with a separate leisure system, and I had hoped to find a separate circuit lurking somewhere in the wiring. This necessitated a complete and, as it turned out, timely rewiring of the high amp side of the electrical system.
I discovered a local school had scrapped several small 35Ah AGM batteries, along with their cycle data. I bought these for just £8 each! My theory was that they would be perfect as starter batteries. That dealt with the starting issue, but the amperage from the alternator was way too much at 90A (with Advac). I discovered Sterling were selling B2B chargers remanufactured on eBay with a full guarantee. The 60A version can run in half power mode. I needed to separate the battery chemistry somehow, and this was perfect. The older relay system just wouldn’t cut it.
So, although I could run the solar and later the wind gen regulator straight to the Lifos, it made as much sense to route all of the charging to the AGM side, and use the B2B purely as a Lifos charger. Otherwise, if the Lifos should suddenly disconnect for any reason, the solar charge controller would be damaged, as it needs a battery connection at all times. This also meant that the starter batteries would always be in condition to start. Also, the alternators would not be stressed, and the current would be managed out to the Lifos should the engines be running.
During this installation, I discovered a very easy way to re-circuit the leisure side. Instead of a dreaded three way switch (if you don’t know, these have a reputation of destroying alternators!), we have four main switches. Previously, a clever emergency crossover system worked through the port and starboard switches, and the house bank simply tapped from our starboard battery. I broke this link and ran a new high current cable to the Lifos and added suitable fuses to that and the B2B charger.
This refit uncovered a few hidden horrors. Car terminals used on the batteries were causing corrosion to creep up the cables, all of the terminals were the wrong size and badly peened on, and none of the terminals were sealed.
To rectify this situation, I bought a cheap 10 ton hydraulic lug press, as well as correct terminals and decent adhesive shrink tube. *See link to video!
In total, this entire refit cost less than £160 and took about two to three easy afternoons to complete. Plus, now I know everything is correct and in working order, which is worth a great deal! I even got super carried away and labelled each cable.
Chapter 3: Results
The results have been truly incredible. I had read other converts saying the Lifos battery delivered more than expected, but it truly is the greatest modification we’ve made to the boat so far — to the extent that I would now flinch much less about the price. Partly because of its small capacity, it recharges very fast (in around two hours). Finally, the Ohms law has become a reality!
The slightly higher and smoother voltage also seems to have cheered up a few of our electronics. The diesel heater has a more confident whine, the fridge a stronger buzz, and the inverter is much quieter. Even in the middle of a UK winter, we are able to run for three to four days off the battery alone, and on the rare occasion the sun stays out on consecutive days, we have fully recharged without resorting to mains power. The wind gen is currently disconnected, but I have every confidence that, with its help, we could stay disconnected from shore power for weeks at a time.
You have to forget everything you know about lead acid if you want to change to lithium iron. Instead of fretting that you’ve fully recharged, you can merrily let a lithium iron phosphate battery drop to 50%, 30%, or even lower — and still sleep worry free. You can let it do its thing— if and when it fully recharges, it’s great, but so what?
The solar array also becomes far more efficient. With lead acid, the solar squeezes out power like a lemon until the last few amps are pushed in; with lithium, whatever the panels can produce rushes straight into the battery.
The weight is a revelation. I could lift the battery out with my little finger. (Check out the video here.) The Bluetooth app beats our Merlin multi-gauge, and I can watch it from bed! (I do!) It’s just worry free. There is so much more room in the engine bay suddenly. Even I still can’t believe it’s real — there is no way that this could be our house battery!
We are liveaboards, and although it seems impossible to live comfortably off a house battery of less than 68Ah, this technology is like having a perfect supercapacitor. We still have a fridge freezer running 24/7, we still have lighting and charge our iPads, phones, etc., every night. In fact, during the long, dark winter nights, we are using more power than we ever did in summer, but it’s totally worry free. I estimate this has improved our daily capacity crossed with our recharge rate by a factor of 4-8times.
Only time will tell how good the Lifos will really be, but I’ve waited nearly three months before writing this, at the worst time of the year, and I’m still in awe of this system. I do realize most cruisers use much more power than we do, our previous house battery being 180Ah, but these recommendations can be scaled up to fit your needs. There are alternative LiFePo4 manufacturers, and I’m sure the price is going to cascade sooner or later. Remember, you are listening to someone whose car is a pre-computer, mechanical Diesel, and it’s the newest car I’ve ever owned. I’m a true Luddite, but if I can improve a system, I will do my best — even if it means converting to Lithium.