Latest Lithium Battery debate for C 24

wtsawyer

Active member
Joined
Nov 28, 2013
Messages
25
Fluid Motion Model
C-32 CB
Vessel Name
GUARDIAN
I'm buying a 2018 C 24 and am wondering what the latest discussion is regarding installing Lithium batteries and IF I can operate my AC while underway with them?
Several C 24's for sale are listing the Lithium's as a beneficial upgrade.
Thoughts?
Thanks!
TomS
 
Yes indeed you can run your AC from lithium batteries. Just not for very long. Underway you might be able to run a bit longer if the engine has a big enough alternator and it is configured properly to charge the lithium batteries at its full capacity without damage to the alternator. Note that you can run your AC from lead acid batteries if you have enough of them. There are several advantages to lithium batteries over traditional lead acid batteries.

First they come in at about 35% of the weight for the same amp-hr rating.

Second, and this is the big one, you can draw a lithium iron phosphate battery all the way down to zero without significantly damaging the battery. That is a big contrast to lead acid batteries where drawing the batteries down much below 50% of rated capacity on a regular basis significantly shortens battery life. Running a lead acid battery down to zero may effectively kill it.

Third, lithium batteries maintain voltage at near 13 volts for about 85% of total discharge. Furthermore they don't suffer anywhere as much voltage sag at high discharge rates as do lead acid batteries. This is good for your electronics.

Now the down sides.

First, lithium batteries can not put out really high currents for more than a few seconds. Most Lithium batteries are limited to 1C maximum discharge rate where C is the amp-hour rating of the battery. In other words a 100 amp-hr rated lithium battery will not put out more than 100 amps for more than a few seconds before its internal electronics (battery management system) turn the battery off. So high draw loads (windlass, thrusters, engine starting, windlass, etc.) can only be managed with a sufficient number of lithium batteries in parallel (think 4-6 or more for engine starting). A consequence of this is that you will need to maintain lead acid starting and thruster batteries with a separate charging system from any lithium batteries.

Second, lithium batteries have much lower internal resistance than do lead acid batteries. The consequence of that is that when the lithium batteries are discharged, they will draw a lot of power from the charging system. For example, if you have two (2) 100 amp-hr lithium batteries in parallel, they may draw up to 200 amps from the charge source. What this does is stress alternators by pulling as many amps from the alternator can supply from it. That will cause the alternator to run hot and can destroy the alternator, particularly at lower engine RPM. As a consequence, a lithium battery system requires an alternator with a sophisticated (external) regulator to prevent alternator over heating or an isolation system such as a DC to DC charger to limit the current that can be drawn from the alternator to a safe level. Furthermore lithium batteries require different charging profiles than do lead acid batteries, so the alternator's regulator needs to be capable of being set to the lithium profile. Also, due to the different charging profile of lithium batteries, you may need to change your shore power charger to one that has a lithium battery profile, or change the charging profile of your existing charger if possible. All these changes require the influx of MONEY.

Third, and this can be a big negative, there is a perception that lithium batteries can spontaneously catch fire and that it can be almost impossible to put the fire out. This issue is almost exclusively a problem for the lithium battery chemistry used in electric vehicle batteries. Marine lithium batteries are a different chemistry (lithium iron phosphate) where this problem is minimal. However, many insurance companies have a very negative view of lithium batteries because of this perception. As a consequence the insurance companies will likely require rather stringent installation requirements (compliant with ABYC standards) and also require that the batteries be UL listed. Most consumer grade lithium batteries are not UL listed. The cells in the battery may be UL listed, but the batteries a a whole unit generally are not. There are some fully UL listed batteries available, but at considerably higher cost. Again apply money.

The result is that lithium batteries, when properly installed are a good option for a house bank to increase usable capacity from the same battery foot print. Basically by switching to lithium batteries for the house bank you will effectively double the usable battery capacity. Lithium batteries are not a simple drop in replacement for lead acid batteries for the reasons outlined above. Yes you can run your AC from a lithium battery bank, but you will need a lot of batteries and after an AC run you will need a way to recharge the batteries.
 
We have a 2018 C24 and I thought about switching to Lithium but never did. We use our boat in Maryland on the Chesapeake Bay and here in Punta Gorda. Maryland gets extremely hot in the summer and what I did first was to have the windows tinted which help a bunch. If you open the windows, back door and one portal in the v birth you get a lot of air flow. I also have a Ridgid cordless fan which helps. The AC won’t work much over 13-15 mph because the water intake comes out of the water and the AC shuts down. I can run my AC with my 2000 watt generator when I’m cruising slow and and also while at anchor. $500 for a Harbor Freight generator is not a bad deal.
KKRCRACE
 
KKRCRACE":2uxmgefs said:
We have a 2018 C24 and I thought about switching to Lithium but never did. We use our boat in Maryland on the Chesapeake Bay and here in Punta Gorda.
KKRCRACE
Where are you on the Chesapeake? We are in Virginia on the lower Chesapeake just below the Potomac.
 
We keep our boat at Herrington Harbor North located on Herring Bay about 1 hour south of the bay bridge. We will be down your way this summer with our yacht club.
KKRCRACE
 
We ordered our 2021 R-23 with A/C under way, which included a soft start A/C system (FCF 10,000 platinum), 2000W pure sine wave inverter, scoop intake, and an extra FLA battery (total of 3 90Ah batteries for the house bank). Had about 1.5 hours of A/C while cruising. I installed 400Ah of LiFePO4 and now we have about 5-6 hours of A/C while under way.

We can cruise at any speed with the scoop intake - never had a problem with the water flow while cruising.

I would store the boat for the summer if we couldn’t have A/C running.


Sent from my iPhone using Tapatalk
 
I believe we are taking about a C24. The way my C24 has been outfitted we have never had a problem with the heat. The double step hull lets air under the boat which effects the AC. A scoop intake might help but at that speed we have plenty of air flow and do not need AC. We use the boat on the Chesapeake Bay in the summer and in Florida.
KKRCRACE
 
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