diy solar

diy solar

LARGE Marine Solar + LifePo4 System

mlwohls

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Jan 31, 2020
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11
I hope this long of a post is OK :)

Hi all. Glad this forum exists! I've been watching tons of Will's videos and have been lurking here for a bit.

Background: we're a boat family that's been full-time live-aboard for the last 2 years. We're currently in a 48' sailing catamaran but we are in the process of buying a "new to us" 55' power catamaran. One of the big goals is to outfit the new boat with a very large solar/wind, lithium, and inverter setup. Based on our cruising style, where we make large hops, then sit on a mooring ball / anchor for 2-6wks (while exploring an area, primarily in the Caribbean), we've found that our biggest diesel usage is running the generator while sitting still.

I'd love your thoughts and feedback on my current rough sketch of a system!

BOAT: Large power catamaran that is very house-like (while still being a blue-ocean capable boat). It's interior living space is 2 full levels as the 2nd level is a fully interior skylounge with interior staircase (instead of the more common open air flybridge with exterior stairs). Total interior is approx 1,200 sqft.

GOALS:
With Solar/Wind + LifePo4 + Inverters, on NICE DAYS in the Caribbean, handle:
- 100% of all day-to-day loads (excl AirCon). Exlcluding AirCon, estimated daily load is 10-12kWh (the boat has a large, residential styled refrig, deep-freeze, washer, drier, and water heaters)
- Handle a reasonable amount of AirCon usage without the generator. Using an efficient centralized chiller system by Frigomar (the only variable inverter tech marine AC I've found), the hourly load is approx. 2 kWh per hr of AirCon. So estimating 3hrs/day of renewable energy driven AirCon would add 6kWh
- Total System Daily Capacity = 16-18 kWh

CURRENT SKETCHED SYSTEM:

SOLAR
:
PANELS:
12 Panels of either (both choices cost approx $350-400/panel):
- LG 350W NEON2 Panels (LG350N1C-V5): Nomiinal Capacity = 4.2kW. Well respected, yet more accessible/affordable than rigid panels that use Sunpower cells.
- Panasonic 340W HIT Panels (PAN340HITMONO): Nominal Capacity = 3.9kW. Might not be as popular as LG/SunPower, but has the absolute best Temp. Coefficient which could be critical in the Caribbean (Temp Coefficient of 0.25 vs LG's 0.36)
My estimate (accounting for the impact of the difference in Temp Coefficients), is that both of these arrays would generate 16-20 kWh on an average "nice day"

ARRANGEMENT: These will all physically be in a single, large array on the roof of the 2nd level. Low risk of direct shading as the roof will be "clean" (radar, antennas, etc will be relocated to an arch on the back of the boat)
- LG (each panel is VOC=41V, ISC=11A) would likely be 3s4p (actually 2 parallel 3s2p arrays, each array with its own MPPT)
- Panasonic (each panel is VOC=71V, ISC=6A) would likely be 2s6p (actually 2 parallel 2s3p arrays, each array with its own MPPT)

CONTROLLERS:
2 x Victron MPPT 150/70 TR Ve.Can - These can handle VOC = 150V, ISC=30A and can charge at 2,000W @ 24V (assuming 24V battery setup below)


WIND: To be determined. Likely 2 decent sized wind generators. I'm mostly looking at wind as 2 things (a) some small potential bonus capacity on a normal Caribbean day, (b) backup-plan for stormy/windy days


BATTERIES:
STATUS:
This is where I'm currently the most stuck. I'm very interested in building my own DIY setup as (a) it's much more affordable and that's a big impact at the size I'm shooting for and (b) I'd love the intimate knowledge I'd gain by building it myself (then if/when things go wrong, you likely know where/why).

TARGET SIZING / SPECS: 30kWh of storage (150-200% of estimated daily need). Likely go 24V as it balances the benefits of high voltage (less MPPTs, smaller gauge wires, etc) vs the challenges of addressing the 12V needs of the boat. NOTE: 24V components in the marine industry seem to be picking up steam, but I'll still have quite a bit of 12V.

OPTIONS I'M CONSIDERING (and I may be way off base?):
1) Just bite the bullet and buy a bunch of ReLion batteries. This would require 8 x 300Ah / 12V batteries (2s4p) and would cost $28,000. I think I'd likely need a BMS to manage the 4 parallel sets (each set with 2 in series).
2) Go the DIY route, but have the tackle the significant challenge of figuring out the BMS for a very large system (costs below don't include the BMS(s) that I would need):
2 a) Use Fortune 3.2V 100Ah cells. This would require 96 cells, 12 parallel sets, with each set being 8 cells in series (8s12p). Cost for cells is $11,000
2 b) Use XCell 3.2V 240Ah cells. This would require 40 cells, 5 parallel sets, with each set being 8 cells in series (8s5p). Cost for cells is $11,000
3) Go the somewhat crazy route of buying something like a BMW I3 battery (currrent generation is 40 kWh). This would require dealing with a large step-down converter needed to drop from the 360V battery voltage, but it would be a rock solid system physically and would have more than my targeted capacity. Torquedo is charing $32,000 for these (with a huge markup I think), but I think I've heard that it may be possible to buy one for $16-20,000 from a BMW dealer?
EDIT: 4) I just came across www.ohmmu.com/group31 . 12V 150Ah LifePo4's. Supposedly very popular with Tesla owners for replacing their 12V batteries (can't believe Tesla puts lead acid in their cars???). Chatting with their rep online, he said it would be possible to do 2s8p with their batteries (which would get me my targeted capacity).


INVERTERS:
Current thought is 2 x Victron Quattros 5000W @ 24V. This may be a bit oversized, but my thoughts are:
- I'd like a large amount of headroom to handle spikes (from AirCons, etc, in case I don't go with AirCons like Frigomar that have lower startup draws)
- Redundancy is always great, especially at sea in remote areas. I might be able to get away with ONE larger inverter (maybe a Quattro 8kW), but then if it goes down, I'm pretty stuck, and getting an inverter of this size/type in the Caribbean can be quite difficult/expensive/delayed.


OTHER / MONITORING:
-
I'll likely add in a Victron Venus GX for full system monitoring / integration. NOTE: I know I've listed a bunch of Victron stuff, but for a system of this size, I'd like as many components to be able to talk to each other. PLUS, the boat will have a full (current generation) Garmin system, so they integrate quite well.
- We are exploring adding in some CZone systems to handle digital switching / monitoring


HELP/QUESTIONS/IDEAS
If you've made it this far, a HUGE thanks already. I'd love any of your inputs, questions, ideas, advice, etc. I know this is going to be a BIG project, but the end goal is worth it to me... AND I'm excited about knowing my "new" boat's electrical system so much better than if I just had someone else install everything.

THANKS!

Michael
SV Tortuga... soon to be on MV Proteus (fingers crossed)
 
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Looks like a great setup. My only concern would be if the 4kw of solar can handle both daytime loads like the AC and charge the batteries back up at the same time. I'm sure space is a concern, but if there's room you might want to add 1k more, as panels are the cheapest part of the system. Hopefully the wind generators can make up for that though. I'm also a big fan of 48v for systems that size, DIY or from an EV. Looking forward to seeing the progress!
 
SolarRat, thanks for the encouragement!

2 responses:
1) I'd love to add more solar. The 12 panels is the absolute max I can fit on the existing roof. However, if we find that we def need more, there is room for at least 4 more (350 * 4) if I build a hard top / "solar canopy" over the aft rear deck (see pic attached)
2) 48V system. My only concern here was stepping down from 48v-12v (as opposed to 24v-12v). I guess I just guessed that would be harder / less efficient. And I'd lose the option of running some 24V components on the boat (smaller wiring, etc) as 24V is picking up in popularity in the marine world (I guess I could step down from 48->24 AND 24->12?)
 

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Winston makes a 1000ah cell, you could put 8 in series it would vastly simplify the wiring, I'm thinking about using these for a 4s 12v system, just trying to find a supplier at a reasonable price for shipping to Canada.

 
@NobodyOfNaught Those look quite interesting. My issue is shipping speed. We're trying to shove off to the Bahamas in the next 2 weeks. Thanks for sharing though!
 
Hi, our family is in a similar situation as yours. How did your system end up coming together?
 
That's a big setup.
I thought we were doing well getting 9x250w on top
 
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