Lithium battery system thoughts

[msmith10]

I'm considering a changeover to a Lithium battery system. I currently have 2 Trojan T125 deep cycle 12 V batteries (12V golf cart, somewhere around 200 amp hrs combined) with shore power to an old charger which I'll need to replace going to Lithium. No separate starting battery. 55 amp Mando alternator with internal regulation (from Moyer).
My average use is about 5-7 amps/hr for autopilot, instruments, radio, AIS; lighting is all LED, and for most of my sails I have way more than enough power. However, do 1 or 2 long distance (300 miles) singlehanded races each summer. I really can't cut down much on my power consumption during these. I converted to an icebox rather than refrigeration which helped, but the autopilot is a necessity and that's by far my largest power drain.
During those races I can't avoid running the deep cycle batteries down to 12 volts and sometimes a little less before I can charge them off the engine (in neutral, of course). I usually have to charge about 1 hour every 4 hours or so after the first day to keep the batteries above 12 volts, but obviously this really stresses the batteries and really limits my power. Alternate charging (wind, towed generator) is not an option and I think Lithium would be my best solution as it would allow me to drain much lower and charge much faster. Lithium batteries are becoming much more affordable, and considering my Trojans last only 3-4 seasons, the payback could be pretty quick. And I could get rid of 100+ pounds of weight, and with smaller batteries which weren't positional, get that weight a lot lower in the boat.
The questions I have for this esteemed group are:
Other than a shore-power charger made for lithium, what other components do I need? Battery monitoring? Do I need to change the regulator on the Mando? Should I have a small lead acid starting battery (lawnmower type), and if so, can I tie it into the charging system easily?
Can anyone recommend a good guide/ book that would address these issues and any I haven't thought of?
I have time to study the problem as I'm not doing it until my current set of Trojans is shot, but I want to know what I'm going to do ahead of time.

[ndutton]

Fire risk would give me the willies. The risk/benefit assessment would have to heavily favor the latter for me to ever consider lithium. Read up on how you put a lithium battery fire out. My understanding is fire extinguishers don't work.

[msmith10]

I agree that it's a concern, Neil, but one which can be mitigated with proper component selection and installation, which is why I'm taking time to study the issue now. The risk wouldn't keep me from owning a Tesla (were some generous persons willing to donate one to me), and I certainly would be keeping said Tesla in the garage attached to my home which is worth about 50X the value of my boat.

[ndutton]

Originally Posted by msmith10

I agree that it's a concern, Neil, but one which can be mitigated with proper component selection and installation . . . .

Unforeseen damage is another matter and after all, isn't all damage unforeseen? As for the Tesla analogy, we come from polar opposite positions. For my driving pleasure I prefer classic gas guzzling Detroit muscle.

However, I have no doubt you'll analyze it thoroughly. Please follow up with what you find and best of luck sourcing the Tesla. Their acceleration is beyond belief.

[Dave Neptune]

Mark, if you are really close to the limit of your power perhaps AGM's will do the trick. For the same amp hours you get about 20~30% more available power. They will also require a bit of tweaking to the charging system however without the fire danger.

I have a new Duramax Colorado and it has a so called AGM smart charging system In the first 2 weeks I had my meter out a lot and took it to the shop twice to check the system because as I cruised around and checked the gages I would see only 12V's and at others I would see 14+ as it should be. Drove me nuts!!! Well the "system" looks at voltage and engine "driving" loads at the same time. So while driving under load up hill the alt cuts back to 12v's to aid in fuel economy and when heading back down the hill and there is little load on the engine the alt kicks in at full charge. Watching the volts go up and down is something I am not used to at all however it is just the "system" taking advantage of the additional discharging capacity of the AGM's. Sometimes I shut down at 12v's and others at 14+v's. It really does a nice job!!!! This system uses the advantages of the AGM whereas the LA batteries are constantly maintained at voltage and little of the "capacity" is actually used.

Another consideration is the Li also operates at an even higher voltage and charges even higher (at times) and some sensitive instruments the voltage is at the limit. I have heard of frying some electronics when not being very careful.

Dave Neptune

[joe_db]

I have been seriously considering this. There are a LOT of issues to contend with.
Fire is not really one of them unless you are salvaging a battery from a car. The chemistry used in almost all boat batteries is not anywhere near as fire-prone as car batteries. I am not saying it isn't a worry at all, but it is a lot worse with cars.
Here is what you will be dealing with:
1. Lithium batteries are NOT drop-in replacements no matter what the ad says.
2. You will need more stuff to make a viable system.
3. It requires more hands-on minding than any variety of lead-acid.
4. The marketplace is quite confusing.
5. To do it at the most professional level with all USA sourced parts and batteries is hugely expensive.
6. The cheaper ways to do it require a lot of research.
7. This is NOT remotely doable for non-technical people, you will need to pay someone if you are the type that can't wire up a regulator or battery charger.
8. Even "cheap" batteries are expensive, mistakes cost money.
9. Many batteries will be badly damaged if charged below 32 degrees.

I'll expand when I get a few minutes.

[msmith10]

Originally Posted by ndutton

best of luck sourcing the Tesla. Their acceleration is beyond belief.

I enjoy the gas engine experience too, Neil. My pride is an 84 Alfa Spider I've had for 35 years and has never been in the shop (that doesn't mean it hasn't been repaired- Alfas have innumerable idiosyncrasies which must be attended). The radio is never turned on because I just love to listen to the engine.
Since the beginning I've been impressed with the design and engineering of the Tesla. And you're right, the acceleration is incredible. When the price becomes more competitive with internal combustion vehicles (this will no doubt be a different marque), I'll be a convert.

Yes, Joe, I understand that this is a major conversion involving all parts of the electrical system and some I'm not aware of, not a drop-in. That's why I'm starting to analyze the problems involved. You're also right that you can't trust the manufacturers' hype. That's why I'm looking for a good source. My favorite technical source is Calder, but he needs to update to cover Li.

[edwardc]

Wow, a subject that's near and dear to my heart! I'm in the middle of what's turned into a years long project to convert our boat to Lithium batteries. Its a DEEP rabbit-hole!

DISCLAIMER: I am not an expert, just an engineer who's read the opinions of a lot of real experts.

One of the foremost of these is Rod Collins, also known to those of you who frequent the sailboatowners.com forums as "Mainesail". Rod has a lengthy document on his marinehowto.com website titled "LiFePO4 Batteries on Boats". Its a must-read for anyone considering converting to Lithium.

ASIDE: Rod recently suffered a major stroke, leaving him paralyzed on his left side. He's had to shut down his business which is his sole source of income. For details, see https://marinehowto.com/.


Anyway, the first thing to discuss is chemistry. Regular Lithium-Ion, or Lithium-Polymer, batteries are NOT suitable for a boat. These are the normal chemistries that are used in most consumer products, including Teslas. As Neil mentioned, the risk of fire is just not acceptable.

But there is another, less-known Lithium battery chemistry called Lithium Iron Phosphate (aka LiFePO4). Although these have somewhat less energy density than regular Lithium-Ion batteries, they will not burn like a magnesium flare, making them the best choice for marine use.

Keep in mind that, whenever you have a large amount of energy stored, fire as a result of short-circuits is always a possibility. This is true of lead-acid batteries as well.

The next thing to discuss is "Drop-In" replacement 12v Lithium Batteries. In short THERE IS NO SUCH THING. Lithium batteries have completely different charging requirements than Lead-Acid batteries, and are MUCH more sensitive to violating then than L-A. Even a single bad event can destroy a Lithium battery, not just reduce its life. As a result of this, all Lithium batteries have what is known as a "Battery Management System" (BMS) that monitors the health and charge state of each individual cell in a Lithium battery pack. (In a 12v pack, there are four cells). The BMS forms a "last ditch" defense against unacceptable charging or discharging. It does this by immediately disconnecting the battery from its charging sources, its loads, or both.

In a boat, this can be a real problem. If the Lithium battery is being charged by the alternator, and the BMS disconnects without warning, this will cause the alternator output to spike very high (80V or more!) blowing the alternator diodes and frying every piece of sensitive electronic equipment on the boat! The BMS can disconnect for many reasons: High voltage, Low voltage, High Current, Low Current, High Temp, Low Temp.

In order to avoid this, you need to have a BMS that has external communication outside of the battery (usually CANbus) so it can signal "Hey, I'm about to shut down!", and an alternator charge controller that can be shut down by this signal. AFAIK, none of the "Drop-In" replacement batteries have this capability. It should be clear by now, that Lithium conversion is part of a "system" that involves almost every part of the boat's electrical system, not just the batteries.

One of Lithium's attractive features is their ability to charge or discharge at high currents. But on an Atomic-4 powered sailboat, you are just not going to get more than 40 or 50 amps out of the alternator. There's just not that much power to be had. And even if there were, the alternator does not spin fast enough to reach high power levels. Fortunately, Lithiums will remain in bulk charge, accepting large charge currents, right up to almost 100% charge. This is unlike L-A batteries, which taper off to a small "Acceptance" charge at 80%.

So now, let's talk about capacity. Lead-Acid Batteries shouldn't be discharged below 50% of their rated capacity. Thus, the usable capacity of a 200AH L-A battery bank is only 100AH. But on a sailboat, its worse than that. L-A batteries will charge up to the 80% level quickly. But once they reach that "Absorption" phase, it will take hours more to get that last 20%. So, unless you're plugged into shore power overnight, its unlikely that you will want (or be able to) run the engine long enough to get the batteries past 80%. This means that for all practical purposes, your USABLE L-A capacity is only 30% of of your rated capacity! That 200AH L-A bank only has 60AH of usable capacity when you're on an extended sail!!

Contrast this with Lithiums. Although various experts disagree on the exact top and bottom limits, what I've found is that LiFePO4 batteries can be brought down to about 20% of capacity without long-term harm, and will quickly charge up to almost 100%. This means that a 200AH LiFePo4 battery bank will have a usable capacity of about 80% or 160AH!!! This is over 1 1/2 to 2 times the usable capacity of L-A, in about the same volume and at half the weight.

But it's not all roses. LiFePO4 batteries are much less tolerant of temperature extremes than L-A. Typically, A LiFePO4 battery should not be operated above 140 deg F. This precludes mounting them in the engine compartment, which is a common (but poor) location for sailboat batteries.
In addition, LiFePO4 must NOT be charged below 32 deg F. This is a real problem for those of us who live in climates that regularly go below freezing. And many of the "bargain" "Drop-In" batteries have a BMS that does NOT include a low-temperature cutoff!!

In conclusion, there's a lot of stuff to consider. Unless you stay within one manufacturer's "System", (i.e. Victron, one of the few who got it right) , which is very expensive, the only other functional solution is to "roll your own" starting with bare prismatic LiFePO4 cells, a separate BMS that implements all the limits and communication, and an alternator controller/regulator that is both programmable for a proper LiFePO4 charging profile and capable of being controlled externally by the BMS.

[msmith10]

Thanks, Ed. I'm really sorry to hear about MaineSail. He was a source of information I trusted on almost every aspect of sailing and from which I've learned a lot- the benefits of butyl caulk not the least. I'll check out the document you referenced.
In the end, I may find that the whole idea is just too expensive for me to undertake. If I were 50 years younger it would make more sense, but I don't know how many years of competetive sailing I've got left in me. However, I want to make an informed decision on this before I am forced to lay out another $400 for replacement LA batteries which don't meet my requirements very well anyway.

[joe_db]

I'll start with my first issue - the actual batteries.
USA based companies like Battleborn are very expensive.
It takes quite some doing to research the best options among the China based outfits.
Trying to make your own batteries is a fraught enterprise. On the good side you can pick your own BMS, which will likely be a lot better than most batteries have built in. If the BMS dies you can replace it and likewise with the cells - maybe.
On the down side, from what I have been reading, there is a voracious demand for cells, so if you go buy your own odds are VERY high you are getting rejects no battery company wanted, poorly matched cells, or both

Once you start looking at batteries, you soon discover the BMS is the heart of them and they come with the following options:
1. Some have low temperature disconnects
2. Some are connected to internal heaters to warm the batteries for charging.
3 Some have neither.
4. Some have wired data ports.
5. Some have Bluetooth data connections.
6. Some have both and some have none.

To make it more fun the BMS may not do what the ad says it does.

[tritonyawl2]

[QUOTE=edwardc;127610]Wow, a subject that's near and dear to my heart! I'm in the middle of what's turned into a years long project to convert our boat to Lithium batteries. Its a DEEP rabbit-hole!

That was a very helpful explanation of why i can't use a Lithium battery as a replacement in my car or my boat. Requires an entirely new system.

Thank you!