Boat Batteries & Charging Them Boat Work Tech

Lithium Batteries on a Boat Review

lithium batteries loaded on a small boat

Lithium batteries have been an enormous improve on our boat, Barefoot Gal. Simply over two weeks in the past, Alex Miller of Sea-Tek put in 300 amp-hours of Dragonfly Lithium Batteries on our boat. It has been a complete recreation changer.

Alex Miller coming to put in our Dragonfly lithium batteries

We had considered switching to lithium batteries three years in the past once we modified batteries. However on the time, they have been simply too costly and required the installer so as to add a battery administration system to stop overcharging or over discharge. We’d need to improve a few of our chargers and regulators. Our battery compartment had restricted area. Backside line was that it simply didn’t appear to be a great answer.

Lithium Battery Modifications in Final Three Years

Let’s simply say that lithium batteries have come a great distance prior to now three years. Each Dragonfly and Battle Born now have 100 amp hour batteries which might be replacements for Trojan 6-volt golf cart batteries. They’re the very same measurement and comparable in measurement to most Group 27 batteries. Since many boats have battery compartments designed for golf cart batteries or Group 27, it’s an enormous plus.

They’re additionally a easy drop-in alternative on your present batteries. Assuming that you’ve respectable voltage regulation out of your shore energy charger, alternator, photo voltaic and or wind, together with a great battery monitor, you gained’t have to switch any of it. The Dragonfly Lithium Batteries have an inner mechanism (Battery Administration System) that may minimize off charging earlier than overcharging and minimize off masses earlier than overdischarging. I consider the Battle Borns have an identical battery administration system. The one issues that you simply’ll want to vary are the charging parameters on the regulators and probably your battery cables.

In years previous, hearth was a priority with sure forms of lithium batteries. With LiFePO4 know-how, that may be a factor of the previous. Actually, LiFePO4 batteries are safer than wet-cell lead-acid batteries that may spill acid.

Value of Lithium Batteries

Lithium batteries nonetheless aren’t low cost — $1050 per 100 AH battery — however have come down significantly in worth from three years in the past. Not having to exchange charging gear helped with the general worth of the challenge, as did the truth that set up is far easier. It solely took Alex two hours (together with making new jumper cables from battery to battery and to our bus bars), at $100 per hour. He says most installations take two to 4 hours.

Lithium batteries ought to final a minimum of ten years, or about twice so long as wet-cell lead acid batteries. So simply on that foundation, they’re not going to pay for themselves. However when you think about their different benefits, they’re attending to the purpose the place they do make sense.

Benefits of Lithium Batteries

Conversations with Alex (Sea Tek) advised me that there have been extra benefits to lithium batteries than I noticed. In simply the brief time we’ve had them, I’ve come to see that they’re all true.

Want Fewer Amp-Hours

Lithium batteries may be dischanged 100%, though 80% is best for them long-term. So that you don’t want almost as giant a battery financial institution. Our earlier battery financial institution was 345 amp-hours of lead acid batteries, which we might discharge not more than 50%. This meant that we had 172 usable amp-hours. Now, with 300 amp-hours of lithium batteries, we now have 240 usable amp-hours. However that’s simply the distinction when each banks are new.

Lead acid batteries lose some capability over time; lithium lose far, far much less. Consequently annually down the street there can be a much bigger distinction in usable amp-hours between lead acid and lithium batteries.

Lighter Weight

Lithium batteries additionally weigh significantly lower than any batteries used on a ship. Our new lithium batteries weigh about half what the deep cycle lead acid batteries did. That’s good for the load of the boat, however the greater deal may simply be in making an attempt to maneuver them out and in of the battery compartment.

lithium batteries being installed

Greater Resting Voltage

Full charged lead acid batteries will “relaxation” at 12.6 to 12.eight volts. As a load is positioned on them and in addition as they’re discharged, the voltage will drop. Consequently, issues like fridges, watermakers, microwaves and inverters don’t run as effectively and find yourself drawing extra amps, inflicting a downward spiral.

Lithium batteries relaxation at 13.2 volts and that doesn’t notably change with the load positioned on them or how far discharged they’re. Our fridge takes about 10% fewer amps when operating; our watermaker places out extra water in the identical period of time.

Can Run Heavy Masses on Lithium Batteries

Lithium batteries can put out lots of amps with no injury to the batteries, in contrast to deep cycle lead acid batteries. Lead acids merely can’t maintain pumping out the amps and keep the voltage.

With lithium batteries, there isn’t any want for a separate beginning battery with totally different know-how. If you would like a separate begin battery only for redundancy, effective. However the batteries gained’t be harm by the heavy load that the starter or windlass place on them. As a result of Barefoot Gal’s engine is small, we did away with a separate begin battery way back and simply used our home battery financial institution. Nonetheless, we’d all the time see a noticeable dip within the battery voltage once we began the batteries. Not so with the lithiums; in reality, I used to be slightly stunned as how shortly the engine began — and I hadn’t although it was sluggish earlier than. The voltage is noticeably greater, inflicting it to start out extra simply.

If the lithium battery financial institution and inverter are giant sufficient, you’ll be able to even run an AC excessive capability watermaker from lithium batteries. I do know of a number of who do right here in Boot Key Harbor and Alex is doing a demo to the Rainman Watermaker guys this afternoon to point out how properly they will work collectively. In fact, in case you do one thing like that, the subsequent query is the way you’ll recharge the batteries.

A lot Quicker Charging

Lithium batteries can take greater charging amps for a far larger proportion of their capability than lead-acid batteries. Lead acid batteries will solely take full amps to about 80% of capability, then taper off the amps. This makes filling them utterly very time consuming and for those who’re operating a generator or utilizing photo voltaic or wind energy, you’re more likely to be “throwing away” a few of the energy generated because the batteries are between 80% and 100% full.

Lithium batteries, in distinction, might be fast-charged virtually to 100% full. The Dragonfly web site says that when you can cost at a price of 100 amps per 100 AH battery, they advocate 50 amps. So in case your charging supply will put out this a lot energy, they might go from 100% discharged to full in two hours. And, in fact, we actually solely need to take them to 80% discharged. They usually don’t want (and even need) to be absolutely charged, in contrast to lead acid batteries.

So, our 300 AH lithium battery financial institution might take 150 amps charging. We don’t have that enormous a photo voltaic array (it should put out 20+ amps in the fitting circumstances) and our shore charger (used with the Honda 2000 generator) is 75 amps. Our alternator will put out about 30 amps max. Briefly, no matter we may give the batteries, they’ll take. No energy shall be wasted.

From an environmental standpoint, we wish to run the generator as little as potential. However typically climate circumstances are such that it’s mandatory. With the ability to cost at 75 amps all the best way till the batteries are nearly full as an alternative of the tapering quantity that lead-acid batteries require signifies that we’re operating the generator considerably much less.

Observe About Some Chargers

One essential factor to notice about charging from a generator or shore energy. Some chargers or cost regulators, like ours, will solely put out full amps for a restricted period of time after which will routinely ramp down. For us, that happens after 30 minutes. However the lithium batteries will take the complete amps for much longer. Ramping down signifies that we’ll should cost longer, one thing we don’t need. So our work round is to flip the shore energy off, wait 30 seconds or so, after which flip it again on. And we’re proper again as much as full charging for an additional 30 minutes.

No Wasted Power

One other charging benefit of lithium batteries is that you would be able to get out 99% of the power you set into them, versus about 85% with lead acid batteries (and the share drops annually). This equates to getting about 15% extra out of your charging sources. For us, that’s like including one other 50 watt photo voltaic panel to our present 345 watts. For those who use a generator, it takes one other 15% off the generator run time.

Zero Upkeep

I don’t need to water lithium batteries! Okay, it was fairly straightforward to do with our battery watering system, however it had taken a day to set the system up and I needed to keep in mind to do it. Simply not one thing I’ve to even take into consideration any extra.

Backside Line

We’re very glad we made the change to lithium batteries. One of many fundamental causes we upgraded was to hopefully keep away from the necessity for extra solar energy. Once we had added an Engel fridge to our Isotherm final spring (largely resulting from my diabetes), the additional power required was simply sufficient to tip us from often getting full from photo voltaic day-after-day to often not.

Life with Lead-Acid Batteries

Each couple of days — or every single day if it was cloudy or wet — we’d need to run the generator with lead-acid batteries. And we’d often run it for at the very least an hour, typically extra. We hated the noise, reliance on fossil gasoline and air pollution.

We talked to Alex at Sea Tek about including extra solar energy however couldn’t discover a good place to mount one other panel on the boat. And it will be a bit extra weight and windage. Then he advised that we take a look at getting lithium batteries resulting from their tremendously improved efficiency and charging. We took a deep breath and stated sure.

Life with Lithium Batteries

In just a little over two weeks with the lithium batteries, we’ve run the generator as soon as for about an hour and a half. On reflection, we in all probability didn’t have to run it fairly as quickly as we did however, coming from lead-acid batteries, we have been nervous when the state-of-charge stated we have been 60% down after a number of cloudy days.

It’s now been 10 days since that one time we charged with the generator. Our energy utilization hasn’t decreased a bit: we’re nonetheless operating two fridges and a watermaker, plus every part else on board. We haven’t all of a sudden had sunnier days or higher photo voltaic circumstances. It has simply been the larger capacity to make use of all the facility that any power supply places out, plus the improved charging effectivity. The upper resting voltage additionally performs an element as does the power to discharge the batteries additional. A deficit in the future doesn’t should be made up instantly.

10 days since we final ran the generator and the batteries are nonetheless over 13.2 volts and solely 13% discharged


For us, the longer lifespan, higher usable amp-hours and lighter weight of lithium batteries are the best-known advantages however simply the beginning. The higher charging profile has made an enormous distinction in our lives. The power to run bigger masses by way of an inverter as an alternative of the generator can be good when we have now the necessity. The power to make use of the windlass with out the engine or generator operating might sometime permit us to get out of an untenable anchorage in Three-foot seas and a lifeless engine. Sure, the lithium batteries have been costly however we’re avoiding the price of one other photo voltaic panel and regulator and/or the price of operating the generator.


Lithium batteries are a big upgrade on any boat. Are they worth the price? What advantages do they offer? Review and comparison to lead-acid batteries. Some hyperlinks above (together with all Amazon hyperlinks) are affiliate hyperlinks, which means that I earn from qualifying purchases. Study extra.