An idiot's guide to building a big lithium bank

[Simi 60]

The predominant charge sources will be 20*250w solar panels

I would love to see how you get that many panels on your roof
I would have thought we had similar roof real-estate, we got 9 on, could probably fit 3 more but 20?

 

[GoneDiving]

I would love to see how you get that many panels on your roof
I would have thought we had similar roof real-estate, we got 9 on, could probably fit 3 more but 20?

I've got an essentially flat roofline the full width of the vessel. See my previous photos. It's only interupted by the paravane supports, A/C condenser and aerial mast. All these run east west. So it's 4 wide, 4+8+8.

I bought 250w panels specifically because larger units actually reduced the total wattage that would fit

Paint goes on this week then I'll post photos of the completed roof

 

[SteveandZoila]

solar

Gone Diving, what size are you 250w panels? 3 years ago I put four 380 watt panels , barely fit. You don't get much over 25% most of the time. Can peak to 50%, but that may be according to battery needs.
When I bought this 3years ago, I was going to do what you did, Very long story, but I canceled order of panels and batterys from Alibaba Company, they were late and bought AGMs. I also found out at the time I would have have to pay very high Tariffs. Solar provides enough power, don't use genset. Except today, its been cloudy and raining today.
I will follow you and others here to continue my education on LFP systems.
Nexr change out or boat will be lithium.

 

[GoneDiving]

Each panel is a little over 700*900mm.

Yes they are rated at 250w but actual performance remains to be seen. They are just basic rigid residential chinesium panels but I'm fortunate that I dont have much shading and I'm wiring in 5 parallel strings of 75v so losses should be minimal.

Battery size and a small generator should provide all the back up I need.

I'll keep posting here but the solar generator project is competing with the 900 other jobs in my refit so updates may be sporadic as the various stages are completed.

I bought the panels from a domestic reseller so no duties (I assume these are the Tarrifs that you refer to). I think I paid a couple of hundred dollars for the cells.

Cheers

 

[twistedtree]

Each panel is a little over 700*900mm.

Yes they are rated at 250w but actual performance remains to be seen. They are just basic rigid residential chinesium panels but I'm fortunate that I dont have much shading and I'm wiring in 5 parallel strings of 75v so losses should be minimal.

Battery size and a small generator should provide all the back up I need.

I'll keep posting here but the solar generator project is competing with the 900 other jobs in my refit so updates may be sporadic as the various stages are completed.

I bought the panels from a domestic reseller so no duties (I assume these are the Tarrifs that you refer to). I think I paid a couple of hundred dollars for the cells.

Cheers

Crap, you are down to 900 projects? I need to get cracking

 

[BCRyan]

Great thread and it's motivated me enough to place an order for 16 cells to replace my boat's house AGMs. I've poured through this thread several times and am now working my way through Off-Grid Garage's uber-informative videos.

What are your plans for physically housing and securing the cells? I'll be removing four 8D batteries and am looking for some trays to secure 4 LiFePo4 cells per former 8D space, ideally with the possibility to expand to 8 cells per.

 

[GoneDiving]

What are your plans for physically housing and securing the cells? I'll be removing four 8D batteries and am looking for some trays to secure 4 LiFePo4 cells per former 8D space, ideally with the possibility to expand to 8 cells per.

I've got the luxury of also being in the middle of a full refit so mine are going into the base of a custom built pilot berth/bench seat with the inverters and breakers etc directly above

 

[Mako]

What are you doing for ventilation - relying solely on convection or installing a small CPU fan?

 

[GoneDiving]

What are you doing for ventilation - relying solely on convection or installing a small CPU fan?

Convection initially but there is plenty of room for a thermostat and forced ventilation should the inverters and wiring pump out too much heat.

I'm expecting the VFD to produce the most heat but it will only run for short periods at time.

 

[twistedtree]

Convection initially but there is plenty of room for a thermostat and forced ventilation should the inverters and wiring pump out too much heat.

I'm expecting the VFD to produce the most heat but it will only run for short periods at time.

What's the VFD driving?

 

[GoneDiving]

What's the VFD driving?

It's acting as a single to three phase converter to drive my 7.5kw hydraulic power pack for my anchor winch.

 

[twistedtree]

It's acting as a single to three phase converter to drive my 7.5kw hydraulic power pack for my anchor winch.

Got it, thanks.

 

[Mako]

@GD, so you’re converting DC to AC1ph to AC3ph to hydraulic.

I assume this is how your boat is already equipped. So if you were to start from scratch wouldn’t you just install a 3ph motor in your windlass and drop the hydraulics?

 

[GoneDiving]

@GD, so you’re converting DC to AC1ph to AC3ph to hydraulic.

I assume this is how your boat is already equipped. So if you were to start from scratch wouldn’t you just install a 3ph motor in your windlass and drop the hydraulics?

Yes and no. The vessel is ex commercial, the existing windless is a carryover and is grossly over engineered. I'm very comfortable with this so that's why it's staying.

If I was starting from scratch, the 3ph would go but I'd keep the hydraulics, all be it smaller. It's essentially maintenance free, stalls at over load rather than burns out and is very tolerant of seaspray and being unloved. I have removed all the other 3ph from the vessel and did look at converting the power pack to 1ph but it introduced too many one off parts where as a 10hp 3ph motor can be sourced anywhere. The same for the simple hydraulics.

Supplying the 3ph via the VFD also has the big advantage of essentially eliminating any startup inrush so the electrical supply/generating equipment can be dramatically down sized. Batteries and Inverters would need to be truely huge to reliably operate a 7.5kw DOL or even Star Delta starter.

There is obviously a loss of efficiency with all the conversions vdc to 1ph to 3ph to hydraulics but this is trivial when balanced against the minutes per day that the windless is working and the systems capacity is already there for other house/diving loads.

I've found VFDs, batteries and Inverters to be very reliable and near maintenance free in the past. Certainly more than large generators. I severely doubt I will miss the noise, vibration, fuel burn, spares inventory and sheer space requirements of the removed generators.

Cheers

 

[GoneDiving]

@GD, so you’re converting DC to AC1ph to AC3ph to hydraulic.

I assume this is how your boat is already equipped. So if you were to start from scratch wouldn’t you just install a 3ph motor in your windlass and drop the hydraulics?

I should also mention that i also considered using 3ph inverters but then i would still have the inrush concerns and would loose the headroom that i will have on the 1ph system.

 

[Snapdragon III]

This is a great thread. Thanks for sharing.

 

[Wood]

<snip> It still running today about 18 months later with very little deviation between cells.

Thanks for that information.

What amount of deviation are you experiencing and under what conditions?

 

[GoneDiving]

.... I severely doubt I will miss the noise, vibration, fuel burn, spares inventory and sheer space requirements of the removed generators.

Cheers

Before

 

[GoneDiving]

After.

What generators?? ?

Ready for paint

 

[twistedtree]

Thanks for that information.

What amount of deviation are you experiencing and under what conditions?

Almost always less than 10mv, and more typically less than 5mv. And I've seen plenty of times where they are within 1mv of each other.


Most handheld meters can't even measure less than 10mv.

 

[diver dave]

Gosh; I might look at a 3 ph bilge pump and a 3 ph fire pump as well on a ship that size.
You know how those crazy divers are, with their own Li scooters and flashlights and 100% oxygen, and...

 

[BCRyan]

After.

What generators?? ?

Ready for paint

What a satisfying day that must have been!!!! Gotta love the purge...

 

[GoneDiving]

Gosh; I might look at a 3 ph bilge pump and a 3 ph fire pump as well on a ship that size.

Bugger, looks like I need to put the gensets back now. ?

On a serious note. It did indeed have a 3ph deck wash/fire pump but I'll be putting in 1ph versions.

You know how those crazy divers are, with their own Li scooters and flashlights and 100% oxygen, and...

That's what the Helium is for: fire retardant. ?

 

[GoneDiving]

What a satisfying day that must have been!!!! Gotta love the purge...

Oh, I can beat just a couple of generators:

 

[Mako]

Bugger, looks like I need to put the gensets back now. ?

On a serious note. It did indeed have a 3ph deck wash/fire pump but I'll be putting in 1ph versions.

3ph is great for megayachts and fishing boats, but I don't think there are any loads large enough on a typical 50-65ft recreational boat to warrant it. In particular, soft starts are more effective at reducing the high inrush on 1ph instead of 3ph, and likely you'll want to be able to power all your motors via an inverter.

Plus to have a 3ph system would require 3 separate inverters which sync. If any one goes down then you lose a leg.

So IMO, 3ph advantages don't outweigh the disadvantages.

A local exception might be the VFD creating 3ph to run your windlass.

 

[diver dave]

Agree for the most part. Three phase motors have the inherent simplicity of no caps, no start winding, no centrifugal switches. Prolly will work for a while immersed in salt water. True, you can drive them with a vfd, but so much for simplicity.

Lightning takes a strike and holes the hull and/or starts a fire. What still works?
Is there a significant power source beyond the giant Li bank? Maybe have a 80/20 split?

Usually lots of ways to design for crisis.

 

[GoneDiving]

Plus to have a 3ph system would require 3 separate inverters which sync. If any one goes down then you lose a leg.

So IMO, 3ph advantages don't outweigh the disadvantages.

A local exception might be the VFD creating 3ph to run your windlass.

We could also distinguish between benefits/faults of 3ph supplies and loads.

In my case, a major benefit to converting to 1ph supply was leg loading and headroom. By this I mean that it wasn't unusual to have one leg loaded at 10x the current of the others. Also, 3ph only permits 33% of the current per leg whereas 1ph allows 100%. Even with large 10kw 3ph inverters I would only have ~3kw per phase available, a problem when my galley and dive equipment will have numerous loads in the 2 to 3kw range. With 10kw of 1ph I have more than enough to run multiple loads simultaneously.

I've kept the one 3ph induction load for several reasons: $$$$ to replace; 10hp 3 ph motor's are available everywhere, 1ph of the same size not so; simple speed, inrush and current control; I've found VFDs very reliable in the past with spares are cheap/easy to source.

 

[GoneDiving]

Agree for the most part. Three phase motors have the inherent simplicity of no caps, no start winding, no centrifugal switches. Prolly will work for a while immersed in salt water. True, you can drive them with a vfd, but so much for simplicity.

I'd argue that the 3 phase motor and VFD is the simplest solution to give speed control and current limiting under startup and running.

Carrying a spare $600 VFD and dcdc converter when far from home is hardly onerous for a vessel this size.

Lightning takes a strike and holes the hull and/or starts a fire. What still works?
Is there a significant power source beyond the giant Li bank? Maybe have a 80/20 split?

Usually lots of ways to design for crisis.

A lightning strike is certainly a low probability/high consequence risk, the same as any vessel.

I'd suggest if the strike is large enough to hole a 10mm, 3/8" hull I'm going to have some pretty big problems to deal with regardless of what electrical design I use. ?

While the inverting and storage of vdc do present single points of failure, any event would have to simultaneously take out 2 inverters or 3 parallel battery packs to totally stop the system. Possible yes but highly improbable.

Yes I will carry a generator, all be it small, more for when the sun doesn't co-operate, but it will offer disaster recovery too.

Cheers

 

[diver dave]

I'd argue that the 3 phase motor and VFD is the simplest solution to give speed control and current limiting under startup and running.



Carrying a spare $600 VFD and dcdc converter when far from home is hardly onerous ….

Yeah, I’d do the same.

 

[Simi 60]

Oh, I can beat just a couple of generators:

Found ya. (-;


So how do you rate the slipway and trades ?
It's one we have on our list for our 60 ft, 65 tonne and 7.5ft draft