looking for a design overview input
- Thread starter sandog
- Start date
400bird
Solar Wizard
It looks like you've got 48v and 370v packs (96s3p) paralleled at the top left.
Currently you have the 48v system (with solar) charging the 24v. The 24v is then keeps the 12v starting batteries full/charged? I think you'd be ahead to charge the 12v directly from the 48v system. There probably isn't much to gain there.
But, what I'd want to see is some way for your generators/alternators to charge the 48v pack.
I don't know the duty cycle on a windlass or bow thruster, if my math is right you'd have 23 minutes of run time at 400 amps running those 1.23kw packs for their full capacity. I assume the DCDC chargers are ok to take a while to recover/recharge?
Edit: I missed the two 24 volt sub panels, are your going to run those straight off the DCDC? No storage to support large load changes, like a motor? What do you run on those sub panels?
Currently you have the 48v system (with solar) charging the 24v. The 24v is then keeps the 12v starting batteries full/charged? I think you'd be ahead to charge the 12v directly from the 48v system. There probably isn't much to gain there.
But, what I'd want to see is some way for your generators/alternators to charge the 48v pack.
I don't know the duty cycle on a windlass or bow thruster, if my math is right you'd have 23 minutes of run time at 400 amps running those 1.23kw packs for their full capacity. I assume the DCDC chargers are ok to take a while to recover/recharge?
Edit: I missed the two 24 volt sub panels, are your going to run those straight off the DCDC? No storage to support large load changes, like a motor? What do you run on those sub panels?
Thank you for the input. I believe I have the BMS mislabeled. Those packs will be 48VDC, total capacity of ~60kwh. There are an additional 4 packs, at 51.2V, at about 40kwh of additional capacity.
The 48V system is being charged by Solar, or the 5.5kw genset, if needed. The 12v charging batteries are fed by the alternators on the motors then go into a charger into the 24V rail to charge that line, which I would like to be able to take that line and charge the 48v as to have the alternators charging the 48v line, if possible.
Duty cycle on the bow thruster and stern thruster is maybe 1 to 3 minutes per 4 to 8 hours. Windlass will be 10 to 20 mins every 8 hours or so. Windlass will have two Fortress FX85 attached to about 700ft of 10mm chain each. Mostly anchoring in 20 to 40 ft of water, but good to have extra just in case. The davit crane and hydraulic lift motor for swim platform are also large loads, but relatively brief run times (less than an hour)
The 12v and 24v subpanels will run IT gear (starlink, kvh h7-hts, 2 peplink cell coms systems, routers, etc), Navionics, Ships computers (2 of them with 8 monitors and amplifiers), Radar, Flir, Nav lights, Etc.
AC loads and charging are the most important for me on this. The headway cells will allow me to replace the 6 8D AGM's being used for high current loads. Locations for the three are separated out from where the main electrical gear will reside, but have 4AWG wire ran to the locations for charging.
400bird
Solar Wizard
Well, overall it looks well thought out. Lots of pretty Victron gear.
For the 24 and 12 electronics loads (i think you've got one portion of the 12v mislabeled 24v) I'd want a small battery or capacitor to stabilize the voltage, but I don't know how tolerant your electronics might be. But, with Victron gear, it's probably fine.
Do you know how much current the windlass draws? 400 amps for 20 minutes is a lot for juice needing big wiring and your close enough to running that battery flat that I'd be concerned.
When I asked about generator/alternator, I was looking at the 4 components off to the right connected to the starting batteries.
For the 24 and 12 electronics loads (i think you've got one portion of the 12v mislabeled 24v) I'd want a small battery or capacitor to stabilize the voltage, but I don't know how tolerant your electronics might be. But, with Victron gear, it's probably fine.
Do you know how much current the windlass draws? 400 amps for 20 minutes is a lot for juice needing big wiring and your close enough to running that battery flat that I'd be concerned.
When I asked about generator/alternator, I was looking at the 4 components off to the right connected to the starting batteries.
For the 24v and 12v loads, most are tolerant of voltage variations, as they are built for this application. Some, for example wifi routers, put in a regulated 12v output regulator. It will take +/- volts and give me a constant 12v, 24v and 48v (POE equipment).
The windlass I believe draws about 100 to 150 amps, but need to measure to verify. If it appears it will get close, I will add another headway or two battery there. Windlass and scuba compressor are the only items of unknown current draw at this time.
For the alternators, they connect directly into the AGM starting batteries. Was trying to run a 12v charger to charge into the 24v bus bar so I can get some use out of the alternators running all the time without trying to add in a second alternator, as cost for that is quite high. I did think about leaving two of the starter batteries for the generators, and then updating the main engines alternators to 24v 200amp units. But trying to decide if it is worth the time and cost of it, as the engines are currently V-belt, and going to high output alternators require me to go to a serpentine belt system.
For the fancy victron gear, wish there was an easier, cheaper alternative, but it seems that the victron stuff links in pretty well to a nmea 2000 backbone. I am all ears if you have better ideas.
Equipment will be purchased by the end of this month.
400bird
Solar Wizard
Definitely worth more investigation.
Yeah, you better know your usage and duty cycle. Do you need "high output" what if your ran standard output alternator at 48 volts? You wouldn't get tons of charging, but it might be worth it.
I think it's also huge on the reliability side. I fully support the decision. I was mostly just realizing how much Victron gear was involved. I'm sure the boat is expensive enough that the cost of the Victron equipment isn't too significant, but it blows my budget out of the water.
I'll look up nmea 2000, I'm not familiar.
Party time!
I looked at the alternators, but it would add significant cost, around 8~10k to update alternators. Not worth it, to me. I have 8kw+ of solar, and a 5.5kw and 33kw genset onboard already. No need to add additional cost for something that will not generate a good enough ROI for me.
My concern is the Victron gear layout and design. Looking for help on this, as it is a great deal of gear and would prefer to not f' something up. As the amount of gear, power and storage is immense.
You have Li-Ion, NMC, and LiFePO4 all on the same boat, and massive amounts of Li-Ion and NMC. Most (All?) marine electricians would flatly not allow that for the dangers it brings. So first off, consider all LiFePO4. If you don't then you need to spend a whole lot of time designing the safety systems. A box on a diagram labeled "BMS" isn't going to cut it. The specific BMS, contactors, relays, fuses, temperature sensors, construction of the box they are it all become the difference between success, and a boat at the bottom of the ocean, possibly with dead people on board.
I would also suggest you work out a very thorough energy budget. You have enough battery for several large homes. Probably more than the largest superyachts would need. It sort of looks like you found a deal on some used EV battery packs, and though "oh, I could do this much, and it would be cool" without any thought about what you actually need, or safety.
The drawing is otherwise an "ok" rough draft, but you need to add a lot more detail, wire sizes, fuses, BMS selection, contactors/relays, BMS control of charge sources, shunts, metering, Victron cerbo wiring. All of this, along with an energy budget, needs to be done before you spend a dollar buying anything.
Maybe @Goboatingnow will chime in. He has spent a lot of time working on Lithium battery design on boats, and could probably provide some valuable detail about what you need to do.
I would also suggest you work out a very thorough energy budget. You have enough battery for several large homes. Probably more than the largest superyachts would need. It sort of looks like you found a deal on some used EV battery packs, and though "oh, I could do this much, and it would be cool" without any thought about what you actually need, or safety.
The drawing is otherwise an "ok" rough draft, but you need to add a lot more detail, wire sizes, fuses, BMS selection, contactors/relays, BMS control of charge sources, shunts, metering, Victron cerbo wiring. All of this, along with an energy budget, needs to be done before you spend a dollar buying anything.
Maybe @Goboatingnow will chime in. He has spent a lot of time working on Lithium battery design on boats, and could probably provide some valuable detail about what you need to do.
Thank you for your input. It is a block diagram, from there, I intend to make a much more detailed wiring diagram. All systems on the boat are/have been done that way.
For the energy audit, unfortunately it the 6 AC units with a combined capacity of 10.5 tons, and going through tropics for a bit consumes enormous amounts of energy. The NMC's are misplabeled, as those lifepo4 as well as the headway units.
And the 40kw of LG ESS I did get a good deal on. I need to have about 100kwh of storage unless I intend to use the genset more frequently.
You're really tight or even a bit short on solar. That is going to matter more than battery capacity if you hope to minimize generator use. I am guessing you will get 30kWh-35kWh per day from your 8 kW of panels.
10 tons of A/C is about 3.5kW x 10 hours per day (assuming you don't run it 24/7) is 35kWh. You have just barely enough, assuming you don't run anything else on your boat.
I would target enough solar for 1.5x to 2.0x your daily consumption. So, 12-16 kW. That way you cover your needs and charge your battery which can cover you on cloudy days. Your battery only needs to be large enough for overnight, when you won't be using the A/C, so it can be much smaller than you have. Even if you want enough for a few days of clouds, 60kWh would probably be enough.
If you want to run 10 tons of A/C 24/7 your solar is majorly undersized, and your battery size won't matter, you are going to run the generator daily.
And holy cow. How big is this yacht? 10 tons of A/C is enormous for a yacht, or even a large house. More like 4 homes, or 6000 sq feet of space. That's what, 150 or 200 foot yacht?
10 tons of A/C is about 3.5kW x 10 hours per day (assuming you don't run it 24/7) is 35kWh. You have just barely enough, assuming you don't run anything else on your boat.
I would target enough solar for 1.5x to 2.0x your daily consumption. So, 12-16 kW. That way you cover your needs and charge your battery which can cover you on cloudy days. Your battery only needs to be large enough for overnight, when you won't be using the A/C, so it can be much smaller than you have. Even if you want enough for a few days of clouds, 60kWh would probably be enough.
If you want to run 10 tons of A/C 24/7 your solar is majorly undersized, and your battery size won't matter, you are going to run the generator daily.
And holy cow. How big is this yacht? 10 tons of A/C is enormous for a yacht, or even a large house. More like 4 homes, or 6000 sq feet of space. That's what, 150 or 200 foot yacht?
Goboatingnow
Solar Enthusiast
- Joined
- Jul 3, 2022
- Messages
- 1,325
Wow this is a big system
Goboatingnow
Solar Enthusiast
- Joined
- Jul 3, 2022
- Messages
- 1,325
Wow this is a big
My comments
1. Way too many batteries doing little , starters etc could all power thrusters etc. or vice versa
High power alternators charging starters that are likely to be fully charged anyway. Hence output is wasted
Big dc dc to get alternators to main battery banks
My reccomendatiobs
1. Merge thrusters starters etc to one suitable lead acid bank. These will likely always being used when engines are running anyway
2. Convert alternators to charge main bank directly , dc dc from main bank to lead acid
3. Verify this number of LiFePO4 batteries can be paralleled many have limits.
4. I’d would question the utility of 48 volt I would agree 24v.
The system needs networked BMS , and you need to examine each failure mode and options did bypass and protection.
And yes the diagram is over simplified. You need to look at interconnected BMS shutdown of all Lithium. You need to look at load disconnection strategies , both normal and priority.
You need to examine charge control mechanisms including “ no float “ charge control
Lots more thinking needed.
My comments
1. Way too many batteries doing little , starters etc could all power thrusters etc. or vice versa
High power alternators charging starters that are likely to be fully charged anyway. Hence output is wasted
Big dc dc to get alternators to main battery banks
My reccomendatiobs
1. Merge thrusters starters etc to one suitable lead acid bank. These will likely always being used when engines are running anyway
2. Convert alternators to charge main bank directly , dc dc from main bank to lead acid
3. Verify this number of LiFePO4 batteries can be paralleled many have limits.
4. I’d would question the utility of 48 volt I would agree 24v.
The system needs networked BMS , and you need to examine each failure mode and options did bypass and protection.
And yes the diagram is over simplified. You need to look at interconnected BMS shutdown of all Lithium. You need to look at load disconnection strategies , both normal and priority.
You need to examine charge control mechanisms including “ no float “ charge control
Lots more thinking needed.
I am know I am very tight on solar. I do wish I could add more, but unfortunately, I cannot, unless I want to get rid of my dinghy or remove seating from the bow.
A/C needs are high, but the dark hull, going through the Caribbean and Gulf will add enormous amounts of heat. The goal is to switch out living areas as needed with AC. So each of the 3 bedrooms have its own cooling units, then the midship bath/laundry area has its own cooling, and the upstairs, which is the helm, kitchen, and living area has 2 units. So at night, hopefully, shut off upstairs, and only use A/C's in the bedrooms when are in there. One of the bedrooms is a bunk room/office. The boat is 70' and a 19' beam. About 1000 to 1100 sq ft of living area. Lots of glass, none of it is double pane.
Solar is going to try and be backed up with the two engines alternators, as this is a motor boat and not a sailboat.
The Generator running is fine, if needed, there is no way to get around it. Luckily there is a 5.5kw generator that outputs 120v and a 33kw that outputs 240v.
My last boat had 17 type 31 AGMs, and a 80k BTU chiller system. It went from St. Maarten to Ft. Lauderdale from Sept to Nov and tried not using the A/C a lot as the generator had to run, and was not worth it. This trip is longer (~8000miles) and I want to be in comfort, and not worry about a generator running 24/7.
The A/C was also sized by two different companies that specialize in that arena, as I thought it was an enormous amount of A/C as well.
AnarchyJet
New Member
- Joined
- Feb 22, 2021
- Messages
- 65
AC on solar/battery is tough to do and your case is really challenging. Could you live with the fact that the 240v panel required running the generator and size your solar/battery to run everything else? Agree with a single 24v bus for windlass and thrusters to simplify things. Also you plan to run 60kwh of LFP and 40kwh of li-ion in parallel? I know it has been done but not sure about it at this size and on a boat.
Thank you for the input.
1.
I agree on the too many batteries not doing lots. Unfortunately, they are dispersed throughout. The AGM starters are in the engine room. The batteries for the windlass and bow thruster are in the forward bedroom. The batteries for the stern thruster are in the back bedroom.
Currently, those battery locations are for the starters 4 8d batteries (overkill), stern 2 8d batteries in series, bow 2 8d batteries in series.
To combine those locations would be extremely expensive for wire. The batteries need to be replaced anyways, so I figure lugging around some headways is way easier than lugging around 8d's. And cheaper.
I was looking at the alternators to charge the main bank, but it looks like upgraded high output chargers and wakespeed controllers, about a $6k price tag on top of everything else.
For the paralleling, was not aware that there was limit. Will definitely have to check this out.
I have been going back and forth between 48v and 24v, and I am more leveling towards 24v as well, as it would be easier to integrate the headways into the system, as well as the ability to charge off my current alternators.
I do have an additional question is it possible to run two different LiFePO4 battery banks at different locations?
Issue I am running into is the space for the batteries would be needed in two different locations, and would need to run larger battery cables for the longer run. Or do both sets of battery cables need to be the same length going into the Multiplus
Running the A/C's off separate panels I have put a lot of thought into it. I do not want to run the generator to power all my 240 loads, and do not want to run it anytime I have to run the A/C's. If running all of them, then yes, on the generator.
For the headway cells, yes, I can run them all back to a single charging/power bus to the main Victron "wall", but the batteries would be essentially remote to that location due to the high current loads they need to power. This is one of the main reasons I have been considering going to a 24v system is to simplify this setup, and it allows the headways to add some additional storage "juice" into the system.
I'm not sure you recognize the scale of what you are proposing, or that you've done any math. The 100kWh battery you propose will take 20 hours to charge with your generator. Usually people size a generator to charge a bank in an hour or so.
You are not the only person with a 70 ft. cat. And most are in the tropics. I seriously doubt even a single one has the battery and A/C load you propose.
Maybe bounce over to cruisersforum.com where others with a similar sized boat can offer solutions. I spent several years in the tropics on a boat, fwiw. Your time and money will probably be better spent on good insulation and window shades. A shade tent outside can counter the effects of a dark hull. Might be hard on a cat but many monos use them. 3 tons of AC will handle 2000 sf. That would be more than plenty for your 1000 sf in the tropics, especially if you close off unoccupied areas.
Anyway, at cruisersforum you will probably find help from others that have a similar boat and already engineered a working system.
You are not the only person with a 70 ft. cat. And most are in the tropics. I seriously doubt even a single one has the battery and A/C load you propose.
Maybe bounce over to cruisersforum.com where others with a similar sized boat can offer solutions. I spent several years in the tropics on a boat, fwiw. Your time and money will probably be better spent on good insulation and window shades. A shade tent outside can counter the effects of a dark hull. Might be hard on a cat but many monos use them. 3 tons of AC will handle 2000 sf. That would be more than plenty for your 1000 sf in the tropics, especially if you close off unoccupied areas.
Anyway, at cruisersforum you will probably find help from others that have a similar boat and already engineered a working system.
If you are looking at a battery that size, and 10 tons of A/C, you can't consider saving a few bucks to reuse crappy alternators or trying to save money on wire.
Put some energy into what the BMSs will be. Budget $15,000 for all the BMS and control equipment, don't be surprised if it goes over that, and don't stress the money for wire and few hundred for external regulators.
I really suggest you need to reconsider the size of batteries, size of A/C, and work up a complete and proper energy budget.
Goboatingnow
Solar Enthusiast
- Joined
- Jul 3, 2022
- Messages
- 1,325
I would suggest 20-30 metres of thruster compatible cabling is going to be a hell of lot cheaper then your proposed battery system. More reliable and easy to maintain too.
This design needs significant rationalisation. The configuration is not technically justifiable nor based on sound principles , you are wasting money also.
Rationalise and simplify it. One big AGM bank will happily support your AGM demands.
Have one boat system voltage
Then you need to do a inch by inch design review looking at cabling size , fuses , manual overrides safety review, and ABYC and or ISO suggested practices.
This design needs significant rationalisation. The configuration is not technically justifiable nor based on sound principles , you are wasting money also.
Rationalise and simplify it. One big AGM bank will happily support your AGM demands.
Have one boat system voltage
Then you need to do a inch by inch design review looking at cabling size , fuses , manual overrides safety review, and ABYC and or ISO suggested practices.
Last edited:
