Here in lies the problem. Nobody, with all of their measurements and lab equipment have shown that I am going to significantly lower the life expectancy of my batteries by connecting them with whatever length cables work best for my boat. Yes, they make great measurements, and nifty looking graphs, but not one of them has shown any significant real world difference in my batteries that have what, a 5,000 cycle lifespan?
[/QUOTE]Re: Nigel Calder's video on parallel battery banks. He doesn't talk about the number of connections required for the various configurations (neither does this print article). Some examples show what looks like a single cable running between the batteries. I haven't seen lug fittings that would do that. My experience is that there would be 20 crimped-on lugs and 20 connection points used in the buss bar system, which gets you "closest" to perfect in theory. What are the chances of 20 fittings/connections all having the same resistance? I would think that a crimp/attachment point would likely be a larger factor than the resistance in a few extra inches of cable here and there. In the print article I cited, about the last paragraph states that for a two battery bank wired "fore and aft," there is no issue.
At the current cost.. the "smoke em if ya got em" view is much easier to adopt and I also subscribe to this view. Even though my batteries are not budget batteries, they arent deal breakers if I have to replace them at around $1500 each x2. Its very likely they will outlast my ownership of this boat. I am really not concerned about milking the last 100 cycles at all.I'm beginning to see the wisdom of Will Prowse's recent statement to "smoke 'em if you got 'em" (that's my interpretation). It made sense to worry and baby-sit lithium batteries when they cost 5 times lead-acid. Now, I'm just as likely to see Davy Jones before I wear out 4 lithium batteries.
That is definately a consideration.I also looked into solid bar stock between the batteries. What makes me pause is having looked at a couple tear downs of the lithium batteries. They use solid bars between the individual internal cells, but the bars are slightly corrugated to allow for vibration and heat expansion that will occur between the cells. A solid bar between external battery posts might have the same issue. Slight push and pull on the battery posts over the years even if the batteries are perfectly secured. Might be a non-issue, but the posts on lithium are skimpy in comparison to lead. I've used the old-school battery handles for lifting out lead batteries that attach to the posts. Would never think of lifting lithium by the terminals.
I've been thinking a bit more about an accidentally depleted bank. I have the NOCO jump starter aboard. I have the dinghy battery and jumper cables. I have a separate 120Ah lithium for the stove (and the jumper cables). But the main reason an "accidentally depleted bank" is of little concern is because of our usage. We check the SOC meter several times in the evening and morning when at anchor. From anchor drop to anchor up (dinner and breakfast), we tend to use 100-120Ah of our 245Ah available from or present lead-acid. That is a little tight, and was another reason for moving to lithium.But your thinking may not be optimal. Mainly because an accidentally depleted bank will leave you stranded. And as we all know..that does happen from time to time for reasons we never predict.
Redundancy #1 is switch to one bank when anchoring and saving 560Ah in second bank. Redundancy #2 is NOCO portable jump starter good for multiple starts of a 7 liter diesel. Redundancy #3 is dinghy battery and jumper cables. Redundancy #4 is stove lithium with jumper cables. I can also mix and match these redundancies for more options.Marco, you will be OK until you are not
Then you will share with others what not to do.
Carry on.
I'm sticking with my original plan of a 4d agm for start with on/off switch and lithium bank for house and bow thruster. When I get to my destination, start battery is switched off and no worries about starting up the next time. Pretty simple. All I have to think about is if I have enough power to run my coffee maker,refer,and blender!!I don't see the difference between accidentally depleting your lithium batteries, and accidentally depleting your flooded lead acid batteries.
It can happen if you're inattentive or if your boat becomes unplugged while you're gone, and you don't have any monitoring system in place.
But I don't see any difference between the two technologies for reinitializing.
If the battery voltage on my inverter charger goes below 10.5 V, then my inverter charger will not work. I have a backup charger. That is the one that keeps my engine and generator batteries topped off that with the flip of a breaker will connect to my house bank as well.
I also have a on off switch that I can use to connect my house battery to my port engine start battery. This would immediately provide voltage to the system and allow the chargers to come online.
But again lithium doesn't change that.
The difference for me is that my present lead-acid banks can run my primary bilge pump for maybe 8 hours straight. My proposed LFP bank about 15 days straight. So if one is has amperage anxiety, LFP is the way to go.I don't see the difference between accidentally depleting your lithium batteries, and accidentally depleting your flooded lead acid batteries.
I understand. And when I say "your thinking may not be optimal" I really mean optimal. That's different than acceptable or even adequate. How many people ran around for years and years on their large 8 D banks used for everything. Tons. Sounds like you have several back up sources too. I think you generally have all your bases covered.I've been thinking a bit more about an accidentally depleted bank. I have the NOCO jump starter aboard. I have the dinghy battery and jumper cables. I have a separate 120Ah lithium for the stove (and the jumper cables). But the main reason an "accidentally depleted bank" is of little concern is because of our usage. We check the SOC meter several times in the evening and morning when at anchor. From anchor drop to anchor up (dinner and breakfast), we tend to use 100-120Ah of our 245Ah available from or present lead-acid. That is a little tight, and was another reason for moving to lithium.
To "accidentally deplete" a 1,120Ah lithium bank on our boat would be very difficult. I would likely hear the crackling of the arcing short or smell the burning of wire insulation. Since we got rid of the generator, there is nothing aboard that makes any noise at anchor. Again, our boat/use specific, but accidentally using 1,000Ah isn't too concerning. I guess I'll find out. Hopefully the jumper cables will continue to sit unused for another decade.
Mark, It's a 5hp marine hardware unit. I talked with Epoch about using 4 100 amp lithium batteries in parallel and said it wood work fine, which it has. I believe it's because each battery has it's own bms. I recall the amp draw was 300 amps for the thruster. The boat was originally set up with a battery bank in the bow but the 2nd owner didn't want to sleep on the batteries and moved to the house bank (6 6volt cc batteries) powering the thruster. Cheers J.T.The difference for me is that my present lead-acid banks can run my primary bilge pump for maybe 8 hours straight. My proposed LFP bank about 15 days straight. So if one is has amperage anxiety, LFP is the way to go.
Having the boat accidentally disconnected from shorepower is something I'm still thinking about. LFP doesn't like to stay at 100%, so I'm wondering if turning off the charger while not at the boat is better. Will have to see what the charging parameters actually do and whether connected or disconnected is better. That will probably cause some anxiety, but I lived aboard for years without shorepower, so I guess it isn't as worrisome to me.
JT: What is the draw of your bow thruster on the lithium bank? More than a starter?
Just heard that a 2024 Tesla just exploded in Las Vegas, killing one. Blame lithium.
Some thinking out loud for storage or sitting at the dock longer term.....Having the boat accidentally disconnected from shorepower is something I'm still thinking about. LFP doesn't like to stay at 100%, so I'm wondering if turning off the charger while not at the boat is better. Will have to see what the charging parameters actually do and whether connected or disconnected is better. That will probably cause some anxiety, but I lived aboard for years without shorepower, so I guess it isn't as worrisome to me.
That's the kind of logic I was looking for. The thruster draws 300A. Epoch 100A each probably have a continuous discharge rating of 100A, for a total of 400A continuous. Epoch says it is okay because there is enough cushion between thruster draw and the 4 battery's discharge rating; a 300 amp momentary draw on 400 amp continuous rated supply. My LFP battery bank will have a 1,000A continuous discharge capacity on a starter motor that has a momentary draw of 500A. The wild assumption that I am making in my install is that an electron doesn't know the difference between a thruster motor and a starter motor.Mark, It's a 5hp marine hardware unit. I talked with Epoch about using 4 100 amp lithium batteries in parallel and said it wood work fine, which it has. I believe it's because each battery has it's own bms. I recall the amp draw was 300 amps for the thruster.
I think this says you have different fuses on order, some ClassT are only rated at 10kA AIC and that you ordered 35/50k breakers.The existing fuses are an 250 ANL fuse for each bank, and that won't be enough for LFP batteries, so I have different fuses on order. In researching Class T fuses, I was surprised to find some 10k interrupt Class T. I thought they were all 20K, so be careful when ordering. I ordered 35/50k breakers.