I have to replace my batteries this year due to their age and not holding charge. This will be my third replacement in 15 summers with the boat. I have three house 4D AGM’s (200Ah each x 3 = 600Ah) and a group 31 AGM starter battery and monitor them with a Victron. We commonly anchor several days at a time. I understand I can safely let them go down to 50% charge, but generally don’t let them drift down past 75%. I don’t like starting a voyage with depleted batteries, since I do not have either solar or wind generators.
All my cabin lights are LED. About 10 years ago, I replaced my refrigeration to a Frigi-boat system, using a brass through hull fitting for heat exchange, one of the best improvements I ever made to the boat. I can stay at anchor for about 3 days before I get anxious to recharge, while in reality, I tend to recharge and replenish hot water using a portable Honda EU2200i generator for about 45 minutes once per day.
I have often considered changing from AGM to Lithium ion, because they are supposed to last 10 years, are about 50lb each compared to 120lb, can be discharged to 80% without damage, and they are supposed to recharge 6 times faster. The expense always held me back, but I see online that I can now buy 200Ah 4D size lithium ion batteries for about the same price as AGM’s ($600-$800 each).
I have a 4 year old high capacity Electromax programmable alternator/regulator and a 5 year old Mastervolt 40 amp 12/40-3 44210200 dockside charger which I believe are both programmable for Lithium ion batteries.
My greatest fear is fire. I read that the new Li batteries have built in regulators to prevent them from being over charged, and that properly setting the alternator and dockside charger to Li specs should also prevent this. If I make the change, I will have my boatyard mechanic do the work, since they installed the alternator and dockside charger, and would be responsible for ensuring that they are programmed correctly.
Does anyone have any thoughts to offer me on this?
The LiFePO4 batteries used in marine systems are not the chemistry that raises concerns about fire. They are very (very) safe, and aren’t subject to the kind of thermal runaway that can happen with other lithium chemistries.
I’m not an expert on marine conversions, but just someone who as been looking at the same conversion for much the same reasons, and I have some experience with the other, less safe chemistries in other applications. From what I gather you do need to make sure your alternator/ regulator system will handle the load and provide an appropriate charging profile. Here are some links I found helpful.
I have switched to LifePo4 batteries. I charge mine via solar and very infrequently a regular multiphase car battery charger, both set to flooded. The chemistry is safe, there is no problem in damaging with over charging or discharging, as the batteries have inbuilt battery management electronics that isolate the cells if necessary. It also does the cell balancing. Different batteries have different parameters but the key issues are max charge and and discharge rate. I have no starter but do have with a 24v emergency electric outboard. I have 2 50Ahr 12v batteries in parallel for my electronics and cold box and switch them in series for the motor, which draws about 20A.
Prices have come down significantly since I got mine. But quite happy with them anyway.
I am now 3 years into my LiPO4 batteries and love them. I have 3 200 ah batteries and I can easily anchor out for 3-4 days without worrying about using up all the juice. Solar would be an easy addition, but I don’t need them for what I do. I highly recommend them.
Good to hear. I have now doubled my capacity and never need anything but solar input. Even on cloudy day sails they never run below 80%. And on sunny days stick at 100%. Never needed my backup electric propulsion but have plenty of power if needed.
Another nice feature about LiPO4 is that they do not need to be charged over the winter. The cold does not bother them. I just disconnect the negative cable for the winter and they stay fully charged.
I have had LiFePo for my motor power for two seasons now. They are pouch cells instead or AA cell. I’ve seen demos where they drilled through the pouches with zero effect. Storage is dead simple. Charge to 70% and the put into shelf mode for the off season. Also, I have a 120v AC charger that can top up the 12v house battery from the motor bank through the inverter if needed.
I am contemplating a new set of batteries because I keep adding creature comforts. A portable fridge/cooler (fantastic BTW, I have a 30 qt Bouge RV cooler) and a diesel heater, and a bunch of rechargable cabin lights and a bunch of USB outlets and on and on.
I currently have 3 120 AH AGMs with 200 watts of solar on the pushpit. I also have a deployable 100 watt flex panel which I place wherever on the boat is getting good sun if current or wind foul up my pushpit orientation. I get about 80% of spec out of the panels in very good conditions.
This is great in summer months but in winter I sometimes have to do a little engine charging. Note: one of my batts is dedicated start so I really have about 120 amps of useable battery and, like another poster I really dislike going below 30% discharge.
The problem I have had with lipo is the need to substantially alter my power system. I have a Balmar regulator which does not support lipo so I need to replace that. Then I have to buy a DC to DC charger to keep the start alive.
If I were to go to lipo i would like to ditch propane and go to induction cooktop but that requires a large inverter.
So, as I white boarded out a system it just got bigger and bigger, esp the inverter.
The issue related to fire is also on my mind. While I understand the BMSs these days are pretty effective. I think there is still some risk, especially if the system is DIY. I also worry about the BMS randomly triggering a shutdown which would deprive the vessel of power.
One thing that could simplify the system for you (and is required now by ABYC) is keeping the AGM start battery. So your existing alternator charges the AGM and use a DC-DC charger (like this one from Victron) to charge the Lithium bank.
A combination inverter/charger could replace an existing shore power charger, so at least you’re not just adding components.
You definitely want to do your research before attempting a DIY battery bank. I have one that’s made up of 32 LFP prismatic cells for 48V/608AH (30kW) to power my electric drive. It was a massive tradeoff between time and energy, vs cost of a pre-built system (a difference of $5k vs $20k+). I was also concerned about the BMS shutting down the system at the wrong time, so I’ve included an emergency bypass switch in my system that will re-engage the battery to motor connection no matter what the BMS wants. Understanding that could be a tradeoff of ending up on a lee shore vs causing permanent damage to the battery, when I’d definitely choose the latter.
It is not good for AGMs to go down to 30% while LiPO4 can go to 5%. AGMs drop voltage linearly from 100% to 30% while LiPoO4 maintaining full voltage until it gets to 5%.
. When I had 3 house AGMs plus AGM stater, (200 aH each) my frig would shut off at 80%, providing me with 120aH of juice. Now with 3 LiPO4 I have over 500 aH of usable juice.
I agree with the suggestion below of keeping an AGM for starter battery and use a DC - DC inverter to charge the Li house bank. I also upgraded to a 250 amp alternator which charges the system quickly.
There is no fire risk from LiPO4 batteries as there is with lithium ion batteries.
Li last 10-15 years, while I could never get more than 3-4 out of my AGms
Make the switch, you will not regret it. But be sure you know what you are doing or get someone who does know to help you
I was not being clear about my AGM discharge limits.I completely agree with you re this issue. What I was trying to say is that I rarely discharge below 70% SOC and I would not go below 50% absent an emergency. That has never happened, fortunately. The other constraint on AGMs is that most of them, if not all, want to be fully charged once charging starts. This is really difficult to accomplish on a sailboat. This probably hastens the batteries demise.
With regard to durability. I had lifeline AGMs from 2007 through 2020. They were beginning to show signs of deterioration so I swapped them out with a cheaper brand (VMAX tanks) because I suspected I would want to take advantage of lithium. Well, looks like the VMAX tanks are beginning to deteriorate after 4.5 years so, sure enough, here I am thinking about lithium.
I have done the math on a variety of possible configurations and it is amazing the jump in useable power I could extract from lithium while reducing significant weight.
I think I need to make a decision fairly quickly before tariffs arrive to increase the cost of lithium batteries and, probably, all the rest of the equipment and supplies I will need to do the conversion. That is one way to convince yourself it’s time for a big project.
One of my colleagues here on the forum has lots of experience with these systems and many of you are actually using systems on your boats so I figure I have and adequate competent advisors to steer me clear of making any major mistakes. I did do a very successful upgrade to AGM batteries, charger, alternator, regulator, etc. 15 years ago so I have a pretty good idea what I am getting into.
That makes more sense. I must have misunderstood your post. I don’t think you can run anything on 30% charged AGM’s.
I put a big investment into this in 2022, so I have 3 years of experience with it. It was worth every dollar. I replaced everything in my system. I probably could have gotten by doing a bit less. I had it all done professionally by my boatyard in Sackets Harbor, NY, which is an excellent boatyard that I implicitly trust. They subcontracted much of the work to Electromaxx who sent a worker down from Toronto.
I installed:
two 12.8V/200 Ah smart Victron batteries in 2022 and added a 3rd one year later in 2023, all for my house system.
one group 31 AGM starter battery
Lynx Victron smart BMS, blue seas safety disconnect switch
30 amp DC-DC Victron to charge starter AGM battery.
Genmaaxx x 250 amp alternator
Orion-Tr smart 12/12/30A isolated DC-DC charger
various associated parts to make it work such as battery temperature and voltage sensor
It was expensive, and one can probably do it for less on your own, but after a lot of study and participations on this forum and Cruisers’ forum, I did not have the time or inclination to try a DIY. It was too complex to trust my own brain to design and install it myself. It took several days for the Electomaxs worker to do the work. I do not think I was charged all the labor Electromaxx put into it nor the travel and lodging costs to send someone down from Toronto for a few days.
The only problem I had was that the BMS was initially incorrectly set for one 200Ah battery instead of 2, and my percentage charge that it read out on my monitor was way off. That was frustrating because we went on a 2 week trip and I could not trust the readings. Once the BMS was reset to two 200 Ah batteries it worked fine. The following year, when I installed the third battery, we knew to reset the BMS.
Now, when I anchor out for a few days, I may run the engine for 1 hour every other day or so, mainly to heat up some water. I have never gone below 50% charge and expect I could go ~5 days without having to recharge. During the time I haul anchor and raise the sails, the high capacity alternator adds significant charge to the system, so I can sail all day without worrying that the electronics will drain the batteries.
I am not saying this is the only way to do it, but this is how I did it and I am very satisfied with the results. I would never go back to AGM house batteries.
Yes, that is very helpful. I am retired and my boat is my main hobby, so I have lots of time on my hands and I find these kind of projects very interesting. Also the cost of professional work out here is around $150 an hour so that would make it very expensive to farm out.
Having said this, It does need to be done properly for sure.
Also interesting is your use case which is almost identical to mine. I do quite a bit of motoring on a 130 amp alternator (tuned down to 70 amps at the regulator) because I am located up in the California Delta and I must motor through some narrow channels on my way to SF Bay where my race venues are located.
So I am headed to the boat to start measuring and planning…
The project cost me about $14,000. It was expensive, but I don’t regret it. I am pretty handy with mechanical, electrical, plumbing, and carpentry (I once ran a farm), but this was more than I felt I could safely do. It would have taken most of a summer for me to do it, and our sailing season on Lake Ontario, (a vast body of water) is short. I am sure you can do it yourself if you take your time, ask for help/guidance when you need to, and are completely confident of your design. I was semi-retired working about 20 hours per week at the time. Now I am fully retired.
I am lucky to say that my boat, Freedom 40/40 #16 built in 1995, has never tasted salt. That makes a huge difference in a boat aging.
Re salt. It sure does make a difference. I live on the California Delta so my boat is in fresh water 95% of the time.
It works out well in the sense when I spend time in salt water I wind up getting a good freshwater flush on the way home.
It also goes lighter on fouling.
Unfortunately someone released invasive water weed species into the Delta years ago and we have to contend with that. It is also shallow in many areas so you need to keep an eye on the sounder. I have lost count how many times I have gone aground in mud. I have become an expert extracting myself or chilling out until the flood tide floats me off.
I grew up on salt water and know that rule. Of course tide is not a factor on Lake Ontario and the St. Lawrence River, at least until you get 350 miles down river to Quebec City, far from where we cruise. Sailboats can only go about 180 miles downriver. Once you get to Montreal, you cannot turn around and go back upstream because the current is so strong. If you get to Montreal, you have no choice but to go another 200 miles to the ocean.
Lake Ontario itself is very deep, like 800. Most of the open water we sail in is 100’+. However, we try to anchor in at least 25’ because the weeds do not grow at that depth. Below 20’ hauling anchor becomes a pain because of all the weeds in the shallower water. We have 10’+ at our dock, which is nice.
We also cruise on the inland waterways of the Canadian coast and the St. Lawrence River. When you go aground there, you are on granite. When you hit a granite shoal you are stopped dead in your tracks. There are a lot of places in the St. Lawrence that it is 80’ deep 10 feet off shore. You really need to watch yourself there.
That sounds interesting all right. I have visited the Great lakes once up in Traverse City. Absolutely beautiful in August. It was really strange being in that ocean of water and not tasting salt.
I too grew up around salt water. Having said that, my father was a master mariner and sailed the great lakes early in his career. What? They have full sized ships in the great lakes?
We also have current on Delta rivers but , worst case, 3 kts or so. It is possible to move, but mighty slowly, against that current. I always depart home just after high tide and return on the flood. If I time it just right, I can ride the tide “bubble” 45 miles to SF Bay at 8 kts, same on the way home I feel like I am driving a Lamborghini
There is major shipping on the Great Lakes every day all day long. They come up from the ocean from all around the world, up the St. Lawrence River, come through Lake Ontario, then lake Erie, then Lake Huron, then Lake Michigan and Lake Superior. These are very big freighters. You have to watch very carefully for them because they can’t stop. It is especially an issue on the River where the channels are relatively narrow.
The river has about a 2-3 knot current, but down at Montreal when it becomes very narrow it is 4-6 knots. That is why sailboats cannot go upstream once you pass Montreal.
The Great Lakes are very treacherous. Major squalls come up quickly without warning. The ports are generally 20-30 miles apart, so if you are out there, you simply have to weather the storm. We have been hit twice 8-10 miles off shore by 60 knot winds and 10 foot waves, thunder and lightening with rain so hard that we couldn’t see the bow of the boat. You can see it coming, but you can’t outrun them. Just have to get the sails down before it hits and head into it.
