Octopus Electrical Service

Time for Lithium?

Lead-acid batteries are so 20th century; lithium’s ARE the future. Making the switch is not that costly now as cost by usable output is now less than a good Lead acid Deep cycle battery , and there are major benefits.

There’s been a lot of talk about lithium batteries in the past couple of years, and not all of it good: Lithium-ion batteries in e-cigarettes occasionally catch fire while in some unfortunate smoker’s pants pocket; airlines restrict the carriage of lithium-ion batteries for the same reason. And, in September 2019, a dive boat anchored off Santa Cruz Island in California caught fire, killing 34 sleeping passengers and crew trapped on board. One theory blames the fire on lithium batteries used in portable devices that ignited while charging. So, with all this bad press, (well there is a BIG difference between a Lithium battery and a Lithium PHOSPHATE Battery read on)   and why swap out the safe and reliable lead-acid batteries in your boat (whether flooded, AGM or sealed gel) for lithium?

The short answer is, LiFePo4 Lithium batteries perform better and last way longer than MOST lead-acid batteries. They weigh less and take up less room. They can provide a higher percentage of use-able capacity than lead-acid batteries, without shortening their life. They maintain voltage through almost all the discharge cycle. They can be recharged much faster. And their only downside is you must not flatten them to 100% EVER, but that’s more than offset by their increased lifespan. The cost and now the same or less than lead acid.  But for folks updating there existing batteries or building or buying a new boat, the downsides are negligible, especially if they spend lots of time at anchor and are tired of listening to the genset hum.

Lithium Batteries

But what about this catching fire thing? Frankly, it’s not an issue with the batteries we’re considering. Not all lithium batteries are alike, after all, and not all are “lithium-ion,” the term commonly used to describe all lithium’s, whether inserted in a tablet or camera, or mounted in an engine room. The difference is in the electrolyte. Lithium-ion batteries, which are used to power phones, tablets and other portable electronics, use lithium-cobalt-oxide (LiCoO), which provides lots of energy versus size and weight. You probably have one of these batteries in your pocket right now. Only thing is, cobalt is unstable, so if charged improperly, this type of lithium-ion battery can get hot and catch fire—not the kind of thing you want on board.

Lithium-iron batteries, on the other hand, use a lithium-iron-phosphate (LiFePO4) electrolyte that’s more stable, not combustible and can better resist mishandling during charging and discharging. It’s a trifle less energy dense than its cobalt-based cousin, but it’s also less expensive. Lithium-iron batteries can last for thousands of discharge/charge cycles—three, four, maybe five times as many as lead-acid batteries  then at the end of there cycle life they still have 80% of there original capacity . (The exact numbers depend on who you ask; some battery manufacturers claim as many as 5,000 cycles for their lithium iron batteries.) The batteries discussed here are lithium iron phosphate, and they’re fine for installing aboard boats.

Cost Versus Value

Let’s get this out of the way up front: A lithium battery can cost two or four times as much as a lead-acid AGM battery of similar nominal capacity. For example, I found a Victron 220 Ah Group 31 AGM battery at Octopus Electrical service listed for $852 Inc Thai taxes;  A 280 Ah A GRADE lithium LiFePo4 battery also from Octopus electrical service was  a drop-in replacement for lead-acid Group 31s, with a built-in battery management system, or BMS, costs $1,642 inc Thailand Taxes on the company website. (A battery management system needs to be added as this protects against high or low voltage on a cell, and it balances the charge state of the internal cells and disconnects the battery if anything goes wrong. A BMS is necessary for all lithium’s; sometimes it’s a separate component.) Of course, $1,642 is a bit of a slap in the wallet, but EVE A Grade Battery claims their lithium batteries last from 3,000 to 5,000 recharge cycles, many times more than the typical lifespan of a lead-acid battery.

The actual lifespan of a battery in recharge cycles—full discharge followed by full recharge—depends primarily on how deeply it’s discharged before recharging. Deep-cycle lead-acid batteries can be discharged to 50 percent capacity, but they’ll last twice as long if taken down by only 20 percent from the full 100% capacity, However the Lithium LiFePo4 Battery has the depth of discharge (DOD) recommended by most experts. Recommended DOD is typically up-to 80 percent, day-in and day-out, and some manufacturers, including EVE, claim 90-100 percent is okay.

So if you buy a 220 A/H Lead acid the MAX usable power is only 110 A/Hr  so the cost per Usable amp hour is $7.75 per Amp Hr  Life of the battery is 3 to 8 years Max or 500 Cycles and you then throw it away as its fully spent

However the 280 A/H liFePo4 can be taken down from 100% to 10% so that’s batteries usable capacity is 250 A/Hrs or $5.90 per USABLE amp Hour. and these batteries have 5000 Cycles so a MIN life of 15 years if cycled every day of the year  and even at the end of that time they still have 80% of there original capacity.

Bottom line cost wise  the Lithium Phosphate batteries are NOW far cheaper than Lead Acid let alone the extra life span.

Bottom line, no matter which kind of batteries you have, don’t discharge them too deeply, and recharge promptly afterwards, for the best service life.(especially Lead Acid)

Lithiums are NOT really affected if they are left in a 70% discharge state AT all,  plus they charge back to 100% very quickly as there charge efficiency or loss is less than 5%  lead acid on the other hand has a Min charge loss of 25% plus to fill them for 80% to 100 takes  4 hrs of charging, Lithium’s on the other hand as 100% full when 14.2 volts is reached and you only charge them extra so that the BMS has time to balance the cells, and you can do this balancing once a month not at every 100% charge.

(Note that the recharging system for lead-acid batteries will most likely work with lithium’s as well, . (Check with your marine electrician before buying lithium batteries.)

Lithium batteries aren’t for every onboard application. They’re not as valuable for starting batteries, but come into their own for deep-cycle house usage, and maybe as dual-purpose batteries in boats with simpler electrical needs. Starting a properly functioning engine takes maybe 5 percent of battery capacity, and it gets recharged right away, so a lead-acid starting battery will last for thousands of starts, and maybe years of service. Why pay the premium for starting batteries? Buy a good-quality AGM starting battery and use the money you save to buy more fuel.

Re Multi Grade Lithium Batteries Batteries that are out in the market place.

There are now Lithium Phosphate batteries that are being sold called B GRADE  batteries these cells  are really  substandard cells that do not meat the factories quality checks,  that’s why they are called B grade, and yes they are cheap but usually cheap for a reason,  No warranty they may not balance well.

A Grade Batteries are just that they have a warranty and they meat the Factories quality standards.

B Grades have there place as they do halve the upfront cost but you then must take the risk on yourself as to how long they last.


A BMS is super important on a LiFePo4 battery as it turns the load or the charging off if a issue occurs within a cell,  ie high or low voltage or temp, this is very important as all lithium batteries cant pass current once they are full, so a full cell has to be slowly emptied as the lower cells are filled.  If you don’t have a BMS then you could end up overcharging a cell.

Fully sealed  battery packs against separate cells.

a Sealed battery with a inbuilt bms  cant be serviced if a cell goes faulty its a throw way, and they also have inbuilt current limits and in these days of high inverter power usage ie over 200 amps then these batteries turn off, so be very careful about there specs.

A Multi cell battery

Well these are the same as the sealed ones but you can check each cell and BALANCE each cell and or replace a faulty cell, and usually they have a OVER ride that allows to to turn it back on in situations were power is VERY important.

IE on a lee shore and the batteries is flat and the anchor is dragging and you need the windlass to bring the anchor in,  well you just turn the override on,  A lithium that turns off because its flat still usually has about10% of its capacity left so no harm would be done on a short term override.  you can override a sealed battery.  in my option they are a real danger to the operation of a boat as they cant be turned back on no matter what.

Starting from Scratch

The benefits of lithium batteries aren’t lost on boat builders, and installing lithiums versus lead-acid batteries in a new boat is free (well, almost free) compared to the cost of the boat.

The batteries from Octopus electrical service use the 123 Smart BMS monitor that displays voltage, state of charge, loads on the system and other vitals. You may also need a battery monitor, not just a voltmeter, to oversee a lithium battery.

A lead-acid battery provides about 25 percent of its capacity at full performance, but then it starts to deplete—you’ll see a gradual loss of voltage until the battery’s dead, so the lead acids voltage reading at any point indicates the state of charge.

Voltage readings don’t help much with a lithium battery, which will put out full voltage until it’s about 80 percent depleted; then the voltage drops precipitously. That’s why the battery meter in your cell phone shows a full charge for a long time, you lose a bar, and then the phone goes dead in an hour. A battery monitor tracks power use more accurately; installing one is a good investment even for lead-acid battery systems as well.

Octopus explains that it’s important to match the recharging capacity to the batteries when designing a lithium system, or you lose some of the advantage of fast recharging. Although some experts suggest limiting recharge amps to maximize the lifespan of a lithium battery, he says it’s fine to pump in amps equal to the battery’s capacity, e.g., recharge a 280 Ah battery at 280 amps. Don’t worry about the 50 percent limit. Doing this often means upgrading the inverter/charger and maybe the alternator, too. You also have to match the recharge voltage to the battery; newer chargers have a switch on the back, or dip switches inside, to set them for lithiums. Installing a lithium battery system is a job for pros, so let them figure out the voltage settings.

Time for Lithium? I think we’ll be seeing systems like what Octopus use on a lot more boats before too long, especially cruising boats for folks who like to anchor out but don’t want to deal with a genset. Ah yes, lithium—the battery of the future, available today.


Advice from Front Street

The professionals at Octopus Electrical service, have installed many lithium battery systems. 

about what to consider when thinking of making the switch.

Both said that since lithium batteries can be discharged further, you can either go with smaller, lower-capacity batteries and get the same effective output, or use lithiums with the same nominal capacity as the lead-acids they’re replacing but get more usable power.

As for the battery management system, they explained that a built-in BMS is less complex, but if there are multiple recharging sources, it’s better to install a remote BMS. And you also need a battery monitor, which means installing a shunt for each D.C. power source; the shunt feeds power usage info to the monitor. While some BMS put out charging info,

All the existing charging systems have to be reviewed. Older chargers won’t have a lithium setting but still can be used if you are careful with the setup as there is not a lot of difference in the charge voltages of a Lithium to a Lead Acid Battery. Charge controllers have the same issue; they have to have a lithium battery setting or there maybe be problems. In some installations, Octopus  recommend a higher output alternator too, or a regulator setup for lithium charging. Replacing just the regulator obviates mounting issues. The genset can usually be left alone—it’s feeding the charger which is feeding the lithiums—as long as the charger isn’t dramatically changed in output that then exceeds the Generators capacity.

Finally, you don’t always have to change all the batteries. Sometimes the manufacturer of an appliance—a bow thruster, for example—will recommend a traditional lead-acid battery. “Each manufacturer has different requirements,

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