I have an electrical question.

[Kopfjager]

My wife and I decided to get a lithium ion battery for our house bank. We are going to keep the lead acid starter battery under the stairs for the etec. Now, because the two batteries are completely different in size and composition, I decided to keep them completely separate with the lithium bank near the bow.

Here is the question. Do I still need to ground these two separate banks together? If so, is that the only connection that would need to be made to be safe? The reason I didn't do a perko switch is because the charging profile of a lithium is different and can be dangerous if overcharged. The battery has interior circuity to prevent that but I like foolproof solutions. Also, I wasn't sure if this would confuse the alternator in the etec or fry the EMM. I simply don't know. Thanks guys.

[Tomfoolery]

All the grounds should be tied, and tied to the equipment ground (not the grounded, aka 'neutral', terminal) in the 120V distribution panel.

If an ungrounded (hot) lead were to touch something on the DC side, everything DC could potentially become energized, including the water around the boat. That can (and does, far too often) lead to electric shock drowning (ESD) of folks in the water in close proximity to the boat when energized with shore power (in fresh water).

So yes, they should all be tied. Just tying the "-" posts won't cause anything weird to happen between batteries, as long as the "+" terminals have no continuity between them.

[Kopfjager]

Awesome. Thank you for the explanation.

[Russ]

Interesting.

How are you going to charge this battery?

What loads are you placing on it?

Why lithium? Those things are spendy.



--Russ

[dxg4848]

The reason I didn't do a perko switch is because the charging profile of a lithium is different and can be dangerous if overcharged. The battery has interior circuity to prevent that but I like foolproof solutions. Also, I wasn't sure if this would confuse the alternator in the etec or fry the EMM. I simply don't know.

perko switch should not be a problem. Battery chargers are connected directly to batteries (not through perko switch). perko switch has four positions: off, battery 1, battery 2, and both. If it is in bat1 or bat2 position then etec alternator will only be connected to that battery (not both) which is also safe.

If you lose starting battery while out how are you planning on starting etec with house battery without perko switch?

[Kopfjager]

Interesting.

How are you going to charge this battery?

What loads are you placing on it?

Why lithium? Those things are spendy.



--Russ

Yes sir. They are spendy. I'll explain why we chose them. I get 300 ah in 83 lbs. I can store it in any configuration. I should still be able to get 80% efficiency after 2000 cycles and should get maximum 3000 to 5000 cycles. Long term, it's cheaper. Before we made the lithium decision I was going with 3 Trojan 30 xhs batteries. That's 198 lbs. of battery for only 195 ah. Even on Trojans website they claim a 600 cycle lifespan. We are power hungry but we still want to keep weight down to go faster with the Etec 90. We have a ridiculous stereo system, fridge, AP, VHF, lights, water pump, GPS, USB ports, etc. I can draw the lithium battery down to 10% without damaging anything. Hypothetically I could draw it dead and the BMS would shut the battery off to protect it. They also accept charge as fast as you can throw it without the need for an absorption stage. The benefits outweighed the cost for us. I like no maintenance. We just want to enjoy our boat.

[Kopfjager]

The reason I didn't do a perko switch is because the charging profile of a lithium is different and can be dangerous if overcharged. The battery has interior circuity to prevent that but I like foolproof solutions. Also, I wasn't sure if this would confuse the alternator in the etec or fry the EMM. I simply don't know.

perko switch should not be a problem. Battery chargers are connected directly to batteries (not through perko switch). perko switch has four positions: off, battery 1, battery 2, and both. If it is in bat1 or bat2 position then etec alternator will only be connected to that battery (not both) which is also safe.

If you lose starting battery while out how are you planning on starting etec with house battery without perko switch?

I'm not, lol. I plan on pull starting that joker or hoisting some sails. Seriously, the problem with using the Etec alternator to charge the lithium is that if the BMS circuitry inside the battery shuts off before I notice the battery is full, it could cause EMM issues especially if there are loads on the alternator when that happens (ie. Stereo, fridge, AP etc.). The alternator is not designed to pull that kind of weight. Now I could still wire it up with a perko but I have to be vigilant EVERY SINGLE TIME and make sure I switch off before the lithium is full. I don't know if that's being realistic. My plan is to charge the house bank with a charger which puts out the required 14.6 volts for lithium on a genset or shore power.

[Russ]

I get 300 ah in 83 lbs. I can store it in any configuration. I should still be able to get 80% efficiency after 2000 cycles and should get maximum 3000 to 5000 cycles. Long term, it's cheaper. Before we made the lithium decision I was going with 3 Trojan 30 xhs batteries. That's 198 lbs. of battery for only 195 ah. Even on Trojans website they claim a 600 cycle lifespan. We are power hungry but we still want to keep weight down to go faster with the Etec 90. We have a ridiculous stereo system, fridge, AP, VHF, lights, water pump, GPS, USB ports, etc. I can draw the lithium battery down to 10% without damaging anything. Hypothetically I could draw it dead and the BMS would shut the battery off to protect it. They also accept charge as fast as you can throw it without the need for an absorption stage. The benefits outweighed the cost for us. I like no maintenance. We just want to enjoy our boat.

I can see the advantages. Especially the draining them down to 10%.

So what do you charge them with?

[Tomfoolery]

How do they compare to real deep-cycle lead-acid batteries, like golf cart/forklift 6V deep-cycle units, not 12V "marine deep-cycle" which don't go as deep?

[Kopfjager]

@RussMT

Right now shore power but when we stay on the hook I'll use a generator on the deck. I know that's not ideal but the outboard is not an option for me.

The cost is the main drawback but if you average out how many sets of lead acid batteries you will go through, lithium comes out cheaper long term. I'll be honest though, the weight savings were what caught my interest. 83 lbs. for 300 usable amp hours is pretty impressive. They are sealed and the lifespan is up to 10 times that of what we were using. You don't have to float them during the off season either. Actually, it's recommended to store them at 50 to 60% charge. I know I sound like a battery salesman but I'm not. Im always looking for ways to make our time on the water more enjoyable and this battery fit the bill.

One complaint I kept reading during my research was the safety concerns. I would definitely recommend you buy from a reputable brand with a good warranty. Also, the charger is critical. It needs to be appropriate for Lithiums due to their charging voltage. I'm aware of the drawbacks of lithium and have weighed the risks and for us it makes sense. They are not for everyone and that's ok. The great thing about these boats is you can customize and accessorize to your heart's content. I'm still keeping the lead acid starting battery though.

[Kopfjager]

How do they compare to real deep-cycle lead-acid batteries, like golf cart/forklift 6V deep-cycle units, not 12V "marine deep-cycle" which don't go as deep?

I was comparing these directly to the deep cycle Trojans. Even on the company spec sheets they state a life of approximately 600 cycles. They're cheaper than lithium definitely but still not what I would call cheap. I needed three of them too so it adds up quick in our boat.

[1st Sail]

Found this on Facebook, MacGregor Sailboat Owners. Definitely a definitive read. I wouldn't touch Lithium without a significant amount of research or purchasing the entire system from a recognized marine source. The power to size/weight ratio is tempting.
Safely controlling the system leaves me nervous. I don't know if pounding down the highway on a trailer would play into the safety of the cells and control systems but I would serious pose the questions. I haven't stayed current over the past year. However, previously charge regulation, temperature, load balance per cell must be insanely accurate or there are serious consequences. I believe the later iterations are not as subject to exploding or catching fire.

Enjoy.
https://marinehowto.com/lifepo4-batteries-on-boats/

[Québec 1]

My wife and I don’t buy batteries,sailing gear,anything that touches a sail or anchor together. I do that by myself. You must have an interesting wife if you discuss new tech battery gear.

[Russ]

Enjoy.
https://marinehowto.com/lifepo4-batteries-on-boats/

Wow! This technology scares me. I don't know enough about it. I still charge my LiPos outside on concrete patio.

--Russ

[sailboatmike]

Lippos are fine just as long as you use a GOOD charger, not one of those cheapos.

The good chargers have proper profiles for the particular type of battery chemistry you are using.

I mess about with radio control stuff and just about the first thing I bought was a high quality charger, not only will it in general charge the batteries in around 1/3 the time of a cheap charger it will have options such as balance charge and fast charge, mine also has space so you can make up your own battery charging profile and store it.

For example a cheap balance charger for a Lippo will take around 3 hours to charge my drone battery, my good one does in in less than a hour and you can monitor whats happening on the LCD screen