Now it comes to one of the main reasons we moved Utopia to St. Petersburg…Lithium Batteries. As we speak, Utopia is sitting over at “The Yacht Rigger” having the old lead acid house batteries pulled and having new lithium batteries installed. This project that has been on the project list from the very beginning will absolutely be a game changer for how we live on the boat and anchor in remote places. I might toss out some terms that might not be obvious so if you have any questions please shoot me a message and I will try to answer them. I just did not want to make this into a super long, and possibly boring, post. I will try not to get too much into the weeds but the “trifecta” constitutes
Lithium Batteries,
High-Capacity alternator, and
Upgraded solar capacity.
So without further adieu let’s get to…
Lithium Batteries
Utopia's present house bank is 800 amp-hours (AH) of 12 volt lead acid batteries (4 X 200 AH batteries). We will be replacing the house bank with the same AH (800) in the same location. Why is this such a big deal? Well, lead acid batteries really should never be discharged below 50% capacity of the battery due to possible damage and shortening of life of the battery. In addition, lead acid chemistry makes it where once the battery is charged over 80% (either by solar, alternator or shore power), the rate of charge from 80 to 100 slows down considerably. If you have a house bank with a battery monitor you can see this slowdown as it seems to take forever to get your battery from 95% to 100%. On the other hand you can discharge lithium down to a conservative 15% (probably 10% or less) and the battery absorbs as much energy as you can give it, so they charge much faster than lead acid batteries.
With a usable capacity for lead acid of 30% (i.e. between 50% and 80%) and a usable capacity of 85% for Lithium (15% to 100%) you get a usable capacity for lead acid at only 240 AH and 680 AH for Lithium (almost triple). Knowing that the amp-hours is the tank your 12 V system uses to run the system, the triple capacity sort of speaks for itself.
I would be remiss if I didn’t at least address the safety factor. I know a lot of people think of fire when they thing of lithium batteries. Lithium batteries that go into laptops and phones are different chemistries than the batteries that go (or should go) into boats and RVs. Laptops use Lithium Cobalt Oxide (LiCoO2) and house batteries for boats should use Lithium Iron Phosphate (LiFePO4). The laptop batteries are more power dense (more power for the weight) but less stable. On the other hand, the LiFePO4 are a bit less dense but much more stable. That, and the fact that each battery has it’s own Battery Management System (BMS) built into the battery, makes me quite confident that they will be as safe as a lead acid battery bank. The BMS will pretty much shut the battery off it there is anything significantly out of spec with one or all the batteries. As a side note, the lithium batteries are half the weight of our lead acid batteries, so instead of having 600 lbs. of batteries we will have about 300 lbs. of batteries. That’s a lot of beer in the bilge.
As stated before, your batteries are the fuel tank for running all the electronic systems on the boat. That's all well and good but, without a quick and efficient way to fill the tank, you will always be power starved since you will never be able to fill the tank, no matter how big that tank is. That brings us to…
High-Capacity Alternator
With the lithium system’s ability to take in (receive a charge) as much power as you can toss at it, we decided to upgrade our old 100 A alternator up to a 255 A alternator. Most boats have an alternator that uses the engine to charge the house bank. I really don’t like to run the engine to charge the batteries. We are a sail boat and we do prefer to sail and running the engine at anchor really is not ideal. Having said this, it becomes necessary to use the engine at times when all other forms of charging is not available. With a high power alternator you can push a lot more power into the house bank in a short period of time and reduce the amount of time the engine needs to run. Also, this new alternator (American Power 255 A) and regulator will play nicely with the lithium batteries.
Since it’s sort of related I wanted to mention that I do have a stand alone lead acid battery that I intend to keep for starting the engine. Lithium and lead acid chemistries do not play nicely with each other but there are some good reasons to keep a lead acid starter battery in the system. With an AC-AC charging you can separate the battery systems and in case the lithium battery BMS shuts down the lithium batteries while the engine is running, the alternator will not be ruined since the power from the alternator would be directed to the lead acid battery. Also, if something shuts the lithium batteries down, you always have a lead acid battery to at least start the engine. There is a LOT more to this, but basically this is the reason for keeping a lead acid starter battery.
And since I said I hate the run the engine to charge the batteries, we are also getting upgraded…
Solar Panels
Utopia presently has 350 watts of solar panels. With the upgrade we are bumping this up to 800 watts (over double). Taking in mind what power we expect to use on anchor or on a normal passage, we feel this capacity will be able to keep us off the grid. This will allow us to top up the batteries on a normal usage basis while still having the engine as a back up if we have several days of cloudy weather. We won’t be wasteful, but we do want the ability to run our boat systems without worrying about running out of power.
When you are thinking about your boat system load, a good thing to do is work out a power budget for each of your items that consume power. You do this for a few different scenarios and figure out which one is critical. An example of this would be doing a power budget on anchor and then a power budget for sailing. At anchor, our biggest power consumer is the refrigerator. That compressor is on probably about 50% of the time and pulls about 7 amps. Knowing this, you could say this item withdraws (7 x 24 x .5) 84 AH of that 680 AH bank per day. Doing that for each of our items, you can figure out how much you use a day and compare it on how much you expect the solar panels to deposit to the battery bank. As a side note, on passage the biggest power consumer is your autopilot, followed by your refrigerator (if you decide to keep it running during a passage). Sondra was surprised to learn that typically more energy is used during passage than at anchor.
Now for the drawbacks.
So with that you might say, this is too good to be true! Well, there are drawbacks, and they are:
It’s flippin’ expensive. Make no mistake, there is a large upfront capital expenditure by a factor of many if you are upgrading the power systems like I am doing. If you are not planning on keeping the boat for a long time or if you are not doing long term cruising off the grid, this might not be the right choice. Prices are coming down but they are still quite pricy.
It’s more complicated. There are a few items like new chargers, including a DC-DC charger and other safety items that are needed to make this system run smoother. Very important to keep the lead acid (if you keep it) isolated from the Lithium.
If you have insurance, you “probably” need to have it done by an ABYC certified technician. I could have probably done most of this myself, but it very well might have negated my boat insurance. Research this!
The next step is doing trouble shooting once all this work is complete. I am sure there might be some bugs to work out, but with this addition, it is our hope that we will not be having any major power issues moving forward.
23-17
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