Replace genset with lithium batteries and a inverter...

One other issue in going to a 24 or 48V system...how do you charge it?

Not only where do you get a 24V or 48V charge source on a 12V boat, but the power available from the OEM sources (both AC & DC) isnt enough to charge these large battery banks quickly enough, unless you install large alternators/charge controllers. You could augment with some solar, but if you build one large enough to do the job, the whole boat will be in the shade!

It can be done, but its very expensive
 
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Another pro for staying 12v is that victron makes this 12v -> 120 inverter/charger that seems perfect for my size boat.
https://www.victronenergy.com/inverters-chargers/multiplus-ii-2x-120v

If I ever expand the system to exceed that capacity, I can always parallel a second inverter and battery system.

Using dtfield’s 8 cell 4s2p battery, it should be capable of dumping over 500A, so it should run the bow thruster.
 
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jmauld said:
I don’t have the paperwork at the house with me, but the thruster is a side power 12V version of a thruster that was a available in 12 or 24V. It might be worth while for me to see if I can easily convert it to 24V.
Click to expand...
How many AH do you really need for the thruster? Could it make sense to use a smaller LiFePo that is capable of the surge current for the thruster, then charge that with a ~30A DC-DC converter from the house bank? Even if you typically used the thruster for a whole minute at a time (which seems like EONS to me), that would only be about 5AH. (@300A). You could probably mount a 5AH battery anywhere (likely much closer to the thruster(s) ).
 
The concern with the thruster isn’t really the AH capacity, it’s the discharge rate. The batteries that DT uses have a ~300ah capacity and a 1C discharge rate. The 1C indicates that it can discharge at 1 times the capacity. Bonus that he has 2 packs in parallel, which means his capacity is around 600ah. So they should easily handle the 250A current draw of the thruster. In the scenario that you listed, that battery is likely only able to handle a 5A discharge safely. The thruster would eat that battery.

But taking your point, I’ve been focused on the thruster, when the bigger issue is probably the windlass. In terms of time usage, it gets used far more than the thruster does.

You also bring up another question that I’ve been meaning to research.

Let’s say I wanted to build two packs like DT has built. If I mounted one pack in the forward bilge with the thruster and windlass, mounted the other pack and the inverter in the back of the boat and joined them with whatever size cable is needed for 250A, is there any concern there? If both packs were charged with the same charger, mounted in the bilge, would the forward pack eventually get less charge?

In my golf cart this issue is addressed by running the positive wire from one battery pack and the negative from the other battery pack, with two wires running between each battery. This forces the batteries to share the load equally. However that use case is different, it is constantly dumping a very large discharge current and is draining the batteries in about an hour. I don’t think that’s really representative of what would happen on a boat. In a boat, you may pull more from the closest battery, but they should have time to stabilize each other at the same voltage.
 
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jmauld said:
The concern with the thruster isn’t really the AH capacity, it’s the discharge rate. The batteries that DT uses have a ~300ah capacity and a 1C discharge rate. The 1C indicates that it can discharge at 1 times the capacity. Bonus that he has 2 packs in parallel, which means his capacity is around 600ah. So they should handle the 250A current draw of the thruster. In the scenario that you listed, that battery is likely only able to handle a 5A discharge safely. The thruster would eat that battery.

But taking your point, I’ve been focused on the thruster, when the bigger issue might actually be windlass. In terms of time usage, it gets used far more than the thruster does.
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It doesn't sound to me that you really know/understand the loads nor the load durations you intend to place on the battery system. The load analysis must consider both worst case concurrent as well as duration. I had my electrical engineer do a complete load analysis on the boat's existing systems then add the inverter to understand both the amperage and amp hour baseline then add margin to that.... This baseline not only established the battery bank but also the charging requirement.
 
jmauld said:
Another pro for staying 12v is that victron makes this 12v -> 120 inverter/charger that seems perfect for my size boat.
https://www.victronenergy.com/inverters-chargers/multiplus-ii-2x-120v

If I ever expand the system to exceed that capacity, I can always parallel a second o inverter and battery system.

Using dtfield’s 8 cell 4s2p battery, it should be capable of dumping over 500A, so it should run the bow thruster.
Click to expand...

If your boat (mine is this way) has twin 30 shore power inlets, you have to choose which AC bus your going to power off the inverter, or make some changes to you MDP AC wiring to limit what loads can be powered off the inverter. Its actually fairly easy to do. This is one of the limitations of the Victron Energy inverters, and the main reason I chose to go with a Magnum Energy MS2812 (it is capable of switching dual 30A AC shore power). And I really like the Victron stuff. I purchased a 24V Multiplus to replace the Magnum, but in the end, it was just a little to much to deal with to make it work. Like I said, lots of sub optimal choices...

I'm not following your comment about "capable of dumping over 500A, so it should run the bow thruster"??

One of the design criteria is you have to account for your largest load and design the battery system to handle it. Usually LiFePO4 batteries are limited to about 200A continuous, and 250 intermittently (like a few seconds), depending on the BMS you choose. You can parallel/series to account for this, but again, space, and proximity to all the components becomes an issue.
 
ttmott said:
It doesn't sound to me that you really know/understand the loads nor the load durations you intend to place on the battery system. The load analysis must consider both worst case concurrent as well as duration. I had my electrical engineer do a complete load analysis on the boat's existing systems then add the inverter to understand both the amperage and amp hour baseline then add margin to that.... This baseline not only established the battery bank but also the charging requirement.
Click to expand...
I actually started that spreadsheet last night. I don’t have the windlass information to add to it, because documentation is at the boat and I don’t know the current that it draws.

Keep in mind that I’m brainstorming in these posts, and the system is being thought out at the moment.

My MAIN goal is to get that damn thruster off the engine packs because I don’t think those battery banks were ever properly designed to handle that load. Everything else is secondary.
 
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dtfeld said:
If your boat (mine is this way) has twin 30 shore power inlets, you have to choose which AC bus your going to power off the inverter, or make some changes to you MDP AC wiring to limit what loads can be powered off the inverter. Its actually fairly easy to do. This is one of the limitations of the Victron Energy inverters, and the main reason I chose to go with a Magnum Energy MS2812 (it is capable of switching dual 30A AC shore power). And I really like the Victron stuff. I purchased a 24V Multiplus to replace the Magnum, but in the end, it was just a little to much to deal with to make it work. Like I said, lots of sub optimal choices...

I'm not following your comment about "capable of dumping over 500A, so it should run the bow thruster"??

One of the design criteria is you have to account for your largest load and design the battery system to handle it. Usually LiFePO4 batteries are limited to about 200A continuous, and 250 intermittently (like a few seconds), depending on the BMS you choose. You can parallel/series to account for this, but again, space, and proximity to all the components becomes an issue.
Click to expand...
The discharge rate is based on several factors, one being the specification of the battery. Most battery specs that I’ve seen specify a 1C discharge rate. Which is one times the capacity. If the battery is rated at 250ah, then it can discharge at 250a. It can exceed that, but you will shorten it’s lifespan. If you put two cells in parallel then a 250a load should split evenly between those two cells and each one would only see 125A. Which would increase their life expectancy. The way that you built your battery pack has a large safety factor built into it that protects the cells from discharging too quickly.

The other limitation is the BMS and associated bits. In your case, you put a single BMS on a 4s2p system, so the BMS is the limitation here. But if you were to duplicate your pack, and the associated wiring, etc, now you have also doubled the safe discharge rate of your total system.
 
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jmauld said:
If you put two cells in parallel then a 250a load should split evenly between those two cells and each one would only see 125A.
Click to expand...
In actuality they do not discharge equally. 2C can actually be 1.2C on one battery and 0.8C on the other. Resistance in the wire lengths that connect in parallel are one example that contributes the variability. Consideration in configuration limitations is needed and, again, must be evaluated as a system from a demand aspect.
 
ttmott said:
In actuality they do not discharge equally. 2C can actually be 1.2C on one battery and 0.8C on the other. Resistance in the wire lengths that connect in parallel are one example that contributes the variability. Consideration in configuration limitations is needed and, again, must be evaluated as a system from a demand aspect.
Click to expand...
That's why I like what DT did. He has a huge safety factor for the individual cells in his battery pack. Which should prolong the life of the pack.

Even something as simple as not using a torque wrench on the battery terminals will contribute to a mismatch.
 
dtfeld said:
If your boat (mine is this way) has twin 30 shore power inlets, you have to choose which AC bus your going to power off the inverter, or make some changes to you MDP AC wiring to limit what loads can be powered off the inverter.

.
Click to expand...
I haven’t really started looking at the inverters too much. But take a look at the inverter I linked. I think it handles L1 and L2 in an appropriate manner for a smaller boat that does not have 240v loads. When you’re plugged in or running the generator it passes L1 and L2 normally. When you’re running off of the battery it bridges them.


You would still need to limit which devices you switch on, but you can do this manually.
 
I didnt read all the post's so this might have been covered.
The couple in this video just changed over to high amp alternator and controller, cool idea. first min of video has the majority of details
 
jmauld said:
I haven’t really started looking at the inverters too much. But take a look at the inverter I linked. I think it handles L1 and L2 in an appropriate manner for a smaller boat that does not have 240v loads. When you’re plugged in or running the generator it passes L1 and L2 normally. When you’re running off of the battery it bridges them.


You would still need to limit which devices you switch on, but you can do this manually.
Click to expand...


The Victron inverters are set up to take a single shore power and then split it into things that are always powered like AC and Hot water heaters, and other things that are inverter powered.
 
dtfeld said:
The Victron inverters are set up to take a single shore power and then split it into things that are always powered like AC and Hot water heaters, and other things that are inverter powered.
Click to expand...
Then there is the Victron Quattro which senses three power sources and determines the active source prioritized as Shorepower, Generator, Batteries for inverting and charging. The Quattro is an inverter/charger so if it is operating on either Shorepower or Generator it charges the batteries concurrent with passing the AC source through. My plan is to use dual Quattro's, set up out of phase so the 240 Volt split phase systems in the boat (Air Conditioning) can be operated. Supplemental to the inverter/chargers the two engines will have high output alternators externally controlled and configured for lithium charge profiles. So, essentially there four battery charging sources. Now in my case I'll have a small AGM battery to start the generator and it is charged by a separate standard marine charger and the generator's alternator. Department of redundancy department. The big difference between my configuration and others (yours) is the lithium bank (1200AH) is also the engine start battery.
If your @jmauld boat is 120 VAC then you need only one Quattro.
 
Just seems insane to design in 100 times the capacity than that you will ever use.
jmauld said:
The concern with the thruster isn’t really the AH capacity, it’s the discharge rate. The batteries that DT uses have a ~300ah capacity and a 1C discharge rate. The 1C indicates that it can discharge at 1 times the capacity. Bonus that he has 2 packs in parallel, which means his capacity is around 600ah. So they should easily handle the 250A current draw of the thruster. In the scenario that you listed, that battery is likely only able to handle a 5A discharge safely. The thruster would eat that battery.
<snip>
Click to expand...
But that rate is for continuous discharge, isn't it? Seems like for thrusters, or even winches for that matter, you should factor into the design that there is a duty cycle or max rate per min or per hr that the device would ever be used, and can adjust the design around that factor. Not any different than the primary motor start circuit and wiring.

I was thinking more a battery like this:
https://www.batterymart.com/p-nlp30-noco-lithium-powersport-battery.html
700A max discharge capacity and only 10AH. There are probably better options, but that's just a quick link I found. Of course it would have to be sized relative to the actual draw of the actual thruster, but I would think this would handle the 250A that you suggest above. How many times would you need to use it, for how long and (roughly) what intervals in between each use would all be factors? Just seems crazy to me to purchase and install 100 times as much capacity as you'd EVER use just to get a function (continuous use) that you'd NEVER use. Most thrusters I see marketed also have time limitations on how long you can run them (i.e, 4 min max, 4min each hr), so why have a source that would deliver orders of magnitude more than that?
 
I'm not sure I would trust that battery in that application, but maybe it would work.

The bow thruster is just one item on the list. For example, the battery that DT built could supply my entire DC load (including the fridge and freezer) for most of the day, while also operating the bow thruster.

His battery is a great size for a house battery. It's a little small to tackle the HVAC, water heater, etc, but everything else it could handle fine.

I'm heavily leaning towards my Stage 1 to be a copy of his battery with no inverter functionality, just have it take over all of the non-mission critical DC loads. Just leave the DC at the helm and the bilge pumps on the starter banks.
 
jmauld said:
I'm not sure I would trust that battery in that application, but maybe it would work. <snip>
Click to expand...
Not saying that exact battery, but more along the lines of that concept. You could locate one like that at the bow, which could provide power for both the thruster and the winch and eliminate the need to run large cables all the way back to the house battery. It also eliminates the surges from thruster or winch operation from affecting any other house loads.
 
I don’t currently have a house battery. Everything is powered off of one of the engine starter banks.
 
@ttmott Is your boat is dual 50A shore power? A dual inverter setup would work very well in my boat with the dual 30A shore power except for space and money...

I have also considered external transfer switches, but this added complexity, and finally I just decided to stick with the Magnum Energy MS2812 as it has a bult in ATS rated 2 x 30A.
 
Dt, look at the Victron that I posted. Doesn’t your boat already have manual transfer switches? You can stack the victron in parallel to expand capacity over time.
 
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