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Power on a Sailboat, how do "we" do it?

April 13, 2016




I thought I would take a few minutes and talk about our electrical power and the battery bank that we have on board Saltair 3.

We don’t have a generator, and we don’t need one.



 When we were researching Catamarans and the transition to life aboard a sail boat, our biggest thing was that we didn’t want to feel like we were camping. Krista especially, wanted our boat to feel like a home. To that end there were numerous things we did to and changed aboard Saltair 3 to that end, but a big part of making the boat feel like a home was that we did not want to have to ration our electricity. 

I know we all turn off our lights at home when we leave a room (or at least we should) and we turn off the appliances when we aren’t using them etc. That’s just good sense and we continue to do that while living on our Boat. But a boat has limited electricity. 

Many compensate for this lack of electricity with a diesel generator. Not a bad option, and popular for sure, but they tend to be loud, both for the occupants of the boat and for the boats at anchor next to the generator in the anchorage. Generators are large and take up valuable and limited space on a sailboat. They use diesel of course, and as many times as I have heard of good generator stories I have heard just as many bad. Stories about them breaking down. Albeit you hear more often about the bad news than the good news. 

But that’s what you hear.


Our Cat didn’t come with a generator. Many boats do. I’m glad ours didn’t because you can buy a boat with a generator and you inherit it's problems. If we had gone that way, it would have been nice to have bought and installed a new one. Either way, budget for your electricity needs on your next boat purchase. 


As space is a premium on sailboats, many don’t have a generator. There just isn’t the space to install one. Lots of sailors use portable Honda 2 stroke generators and they seem to work good enough, but when used they must be left out on deck or in the cockpit and they are the noisiest ones of all.


So what did we do about our electricity. Let’s continue talking about it before we let the cat out of the bag on what we do.


Batteries are most sailboats main source of power. There are two different types of batteries used out there that I know of and variations of one of those. 

Lead Acid and Lithium Ion

AGM batteries, Gel Cel batteries and Wet Cell are the 3 main types of Lead Acid batteries commonly used, and then there a Lithium Ion Batteries. I do not know of any different types of Lithium Ion batteries at this time.

We use Lithium Ion Batteries.


Here is what I’ve learnt and been told about both batteries;


First Lead Acid batteries. 

These are the batteries you can top up with distilled water or they can be the sealed type. The cheapest of the Lead Acids are the type you can fill up with distilled water. They are heavy, and they would leak acid everywhere through their filler caps if they were ever tipped over.

A scary thought.

The other Lead Acid batteries are AGM batteries and Gel Cell batteries. these are considered low maintenance and can be tipped over without catastrophe.

The AGM and Gel Cell are the more expensive types of the Lead Acid battery. I wont go into their specific construction details, suffice to say that they are Lead Acid batteries and in my opinion the best of the Lead Acid, and most suited to Sailboats.


Batteries come in amp hour ratings. The amp hour rating is how long you can use the battery before it is drained. All electrical things use a certain amount of Amps per hour, this Amps per hour is used to calculate your boats amp hour usage and how many Amp hours your batteries onboard need to be. 

An Amp hours rating is basically how many Amps the battery holds. An Amp hour rating on a appliance or the like is how many Amps it will use if used for a complete hour, give or take.


Here’s the low down on Lead Acid Batteries;

Lead Acid batteries need to be looked after. 

They should not be drained lower than 50% but 40% is acceptable. 


When they are used they sulfate and the lead plates inside begin to break down, a natural occurrence in the battery. The lower the battery is drained the more the lead plates sulfate and as they sulfate the less charge it begins to hold. This is commonly called a memory.

Time after time, as it is used, this continues to happen until they won’t hold a decent useful charge anymore. The end of the batteries life cycle.

If these batteries are looked after and not consistently drained past the 40-50% levels, it could take a few years, even 5 years, maybe more, before they will not adequately hold their charge, but it will happen, and most people I have spoken to say their batteries have lasted them roughly 3 years. Battery Warranties are generally this length of time. 

Charging a Lead Acid battery is problem some. They will charge quickly but only to about 80% of their total capacity. When the hit the 80-85% levels they go into what is called a “Float mode” and continue to trickle charge the remaining 15-20% to full. This trickle charge is low, around 2 amps, typically your boat will be using more than what is going into the battery, thus never really allowing you to fill them up. 

So these batteries with 150 amp hours that can only be drained to about 40% and only really charge up to about 85% (these are the best case numbers) leave you at best with only about 45% of their total rating available for use, a third of what you thought you were purchasing.


These Lead Acid batteries tend to be about $500 US dollars for 150 amp hours, generally speaking.

Different qualities of battery can change this cost, plus or minus of course. (You get what you pay for?)

This applies to all Lead Acid batteries, AGM, Wet Cell and Gel Cell. It does not make a difference.


Lead Acid batteries are also heavy. Lead is very heavy. I can’t tell you exact specifications, but of course more amp hours equals a larger battery and a larger battery equals more lead and lead again, is HEAVY! Simple math.


Let’s talk about Lithium Ion batteries. These are the ones we have on our boat.

Lithium Ion batteries are amazing to me. They can be drained to just 5% of their total level.

They don’t sulfate so they don’t have a memory.

That means I can use 95% of the total 150 amp hour rating. That gives me more than twice as many Amp hours in one Lithium Ion battery than in one Lead Acid battery, and because they don’t have a memory they last a lot longer than Lead Acid batteries. 

Lithium Ion batteries don’t sulfate.

In fact the warranty with our Lithium batteries is for 20 years.


Lithium Ion batteries don’t go into a “Float mode”. They charge full blast right up until they are full! No trickle charge. If my Solar panels can put 60 amps into them, then they are taking 60 amps until they are full. 

We use as much power as we want, when ever we want to and we NEVER run out. 

We don’t use our engines to charge our batteries, only our Solar panels, well that’s a bit of a white lie. . .

There was a time when the weather went bad, completely overcast, for almost a week and by day 6, our batteries were getting quite low so I started the engines to help them out. Our alternators can put 80 amps each into the batteries at idle speed until they are full, add a few amp from the Solar panels when the sun peaks through and in about two and a half hours they go from dead to full, with both engines running. Wow.

Yes we do have a water maker. An 8-10 gallon per hour 12 Volt water maker, our battery bank has no trouble running it.

Now Lithium Ion batteries are relatively new and in past there have been some problems with this new technology but as far as my research goes, and those of Maz Ocean in Florida, our installer, these problems have been resolved. 

Lithium Ion batteries are incredibly LIGHT and they are incredible SMALL in comparison.

Put a Lead Acid of 150 amp hours next to a Lithium Ion of 150 amp hours and see what you see. 

Lithium are 2/3 rds the size and half the weight. Exact measurements aren’t available but I did put them side by side and I picked them both up one by one on the day the Lead Acid left the boat and the Lithiums arrived. I was amazed.


There is the Green factor with Lithiums too. Lead acid batteries are for the most part recyclable but how many Lead Acid have you seen sitting around waiting to find a recycling home. 

I’m sure the recycling happens, but as often as it should… maybe… but what about the rest of the battery? The case? The acid? I don’t know enough about the recycling aspect of batteries but I do know a battery recycled every 3 - 5 years isn’t as good for the environment as a battery recycled every 20-25 years.

Lead VS Lithium.


We have changed all our lights over to LED and I’m sure this helps out with our power consumption, but judging by our daily battery levels, I don’t think we needed to.


We have 980 Amps of Solar Power set high in the unencumbered sky on a purpose built Solar arch, a splurge for sure, but necessary for what we wanted.

FYI; Cover just 15% of your Solar panels with shade and you eliminate it's energy output.

That's why we had an arch built. Rarely is there any shade on the arch up above the boom.


One last thing.

Our Lithium batteries come with monitoring software that connects the batteries up to our computer. I like tech geeky things and this is one of them. Our Laptop runs a program that tells you everything you would ever want to know about the batteries and more, it also keeps a log that goes back months, showing you all you need to know, right there on your laptop screen. 


One more last thing Lol : )  The support I have received from the Lithium Ion battery company Valence has been great. we don't get any compensation for saying this at all. ( I really should forward this post to them )

Any time I have had any questions about my batteries or even a refresher question on the info I learnt back when we bought them, the company has been there for me. Try buying your batteries at West Marine and then going back to ask them why things are doing what they are doing…

I’m just saying’...


So what are the down sides?

I can think of just one and I’ll elaborate a little.

The Lithium Ion batteries are EXPENSIVE.

A comparable (but really not) Lead Acid battery (same amp hours) is about, as I said $500. 

The same amp hours in a Lithium Ion will set you back (depending on brand and quality of course) about $2,000.oo Ouch.

Yes, that’s 4 times as much for Lithium vs Lead Acid. That’s a lot.

But if you don’t have a generator or don’t like your generator and you need power, we all do, Lithium Ion is my choice.


P.S. Even while docked next to other boats in marinas, while they are paying out money daily to be hooked up to 110 Volt metered shore power, we have never had need to. 


I think, as far as Lithium Ion batteries go, they are the way of the future.
















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