Sea Change
Active member
We've got about 1200w total on a 39ft mono. The foredeck panels go in to storage for serious passages.
Lithium fears
- Thread starter Neeves
- Start date
We've got about 1200w total on a 39ft mono. The foredeck panels go in to storage for serious passages.
lustyd
Well-known member
Looks pretty tidy, we're thinking of a similar arch for our 36' instead of a bimini as I like the idea of shade and think the alternative is a full hobo looking boat with panels everywhere
Unless, of course, we can actually find a 45 footer that's for sale and doesn't need major work! None we could find in the last year though B27
Well-known member
That's how I treat my lead house battery.
It still works after 3 seasons of my use and it was at least a couple of years old when I got the boat.
Neeves
Well-known member
Sea Change - Thanks for the effort to offer the picture. You have excelled in offering detail.
As I mentioned the commonest comment is the difficulty of committing to a solar display that is big enough. It will be interesting to see how others addressed the problem.
Jonathan
B27
Well-known member
That sounds like nonsense.
Anyone changing from a simple lead-acid boat needs to be buying some sort of charge controller? a few tens of pounds worth of cables at least? A DC/DC charger?
A proper job is going to cost a lot more than £80 even before you import any cells from China.
lustyd
Well-known member
"still works" is all relative though. Lead needs to float constantly or it'll degrade. Have you tested the remaining capacity, or are you content that the lights come on? When I was using lead it look me a while to do the maths and realise they were massively degraded. I even thought my fridge was broken at one point and only later with the lithium realised it was just the low voltage on the lead causing issues. I've also had to replace starter motors due to dead or dying lead batteries, not that I'd go lithium for that, but it made me realise how short the real life of these things actually is in the real world.
Sea Change
Active member
We needed to add a bimini so it seemed to make sense to combine this with the solar panels. I don't think there's much difference in price per m² between solar panels and Sunbrella.Looks pretty tidy, we're thinking of a similar arch for our 36' instead of a bimini as I like the idea of shade and think the alternative is a full hobo looking boat with panels everywhere
Waterproofing was a bit of a conundrum. I ended up finding some lengths of twinwall polycarbonate in a marina skip, and I cut these to a T profile to fit the gaps between the panels, then sikaflexed them in place. They started to lift after a couple of years but overall it's worked well and I can't think of a better solution.
The obvious downside to a fixed solar bimini is that it restricts access to the boom. But if you fold down the sprayhood you can reach everything. It also restricts visibility of the main, but no more than a conventional bimini. I have a perspex window in it, which helps.
The other concern is windage. The boat is currently on the hard on the Caribbean, so I took the precaution of dismantling the bimini for the summer while we're away. The frame is still up but the big panels are lashed on deck and the smaller ones went in the cabin.
Sea Change
Active member
I was specifically talking about just the battery.
If you think it's nonsense, here are my numbers:
Four cells and a BMS, direct from China, £407 delivered. 271Ah capacity at 12v. Equivalent to 542Ah lead acid. That's a price of £0.75/Ah, or £82.60 for a 110Ah (I'm just picking this number as it's a very common battery size).
These numbers are from early 2021, I believe lithium is even cheaper these days.
You're entirely correct that there are additional costs, but the poster I was replying to was starting from the point of view that the batteries themselves cost more than lead acid, which is not really true.
GHA
Well-known member
Depends what solar & charger you have already. A good solar system should be adaptable no matter what batteries you have. Same for a decent charger. I had to change nothing but a few settings switching to LiFePo4. Don't use the engine to charge, though there is a 25A dc/dc off ebay still to be fitted which would do a bit but never needed it. If you are changing a boat to one which can survive off grid it will cost no matter what batteries you use.
PaulRainbow
Well-known member
Those figures are a little distorted though. You would not continually cycle Lithium from 100% to 0%. In reality it would be more like 60%-70% at the most (regularly).
There is no doubt that for some people Lithium is the best solution, especially for those living off grid, but LA works perfectly fine for millions of others.
Suggestions on here (by others) that LA only last for a very short time are nonsense. Looked after properly they last for several years.
B27
Well-known member
Like thousands of others, my boat is completely 'off grid', has a cheap solar controller and makes significant use of engine charging.
I think that's pretty typical of the yachts I see in the South West, a lot are kept on moorings and very few have large arrays of PV panels.
GHA
Well-known member
Does your regulator not do float? You're trashing your lead acid batteries otherwise. Why bother changing to LiFePo4 anyway with that usage if lead acid works already?
PaulRainbow
Well-known member
That's not off grid in the context of this thread (if at all), off grid is living aboard without shore power. Whilst you are away from your boat a smallish panel should charge the batteries ready for your next trip out. Try sitting at anchor for a few days with no charging other than your solar panel.
lustyd
Well-known member
Assume by this you mean down to 30-40% SOC? If so I'd definitely agree. I'd be starting to think about purposefully charging by 20% if I got that low either engine or shore power. With lead I would start getting to that same stage at 80% SOC to make sure we didn't drop too low. One of the things I quite like is that it's hard to do damage to lithium as it'll just switch off and protect itself so I feel less concerned than before.
I'm sure everyone has their different comfort zones with the different batteries, and mine are certainly influenced by being a relatively small bank so SOC drops more quickly when used. This makes "usable capacity" quite a personal thing I think because for me a lead bank was only 20-30% usable capacity while the lithium is 70-80% usable. For others I'm sure they'd be closer to 50% on both.
lustyd
Well-known member
Engine charging isn't off grid (unless you mean regen on electric!). Diesel infrastructure is very much "on grid" and you can't venture away from that infrastructure.
Sea Change
Active member
Yes, you'd be sacrificing cycle life, although AFAIK you could treat them like this and still expect them to outlive any sort of lead acid that is cycled to 50% on the same basis.
I was generally cycling between 20-100% on a not quite daily basis and have not noticed any change in capacity.
Absolutely! I'm not sure who these mythical lithium zealots are, I think they are a figment of the imagination.
Mine haven't lasted very long at all. You do have to be pretty careful with lead acid, a few deep cycles can knacker them.
In warmer climates and with liveaboard use, five years seems to be a good innings. I've not been nice enough to mine and they haven't managed three.
Obviously for weekend use in the UK the same batteries could easily last over a decade.
Trident
Well-known member
Prior to Lithium on our last boat we had Trojan 6v batteries which were happy for 15 years - a PITA to top up with water etc but deep cycle (I know you know all this of course) and exceptional quality and I guess if you have mind set to care for them they last like most things - and if you don't you can kill them in a year
B27
Well-known member
I was replying to a claim about it being cheaper to go lithium than to replace a single 110Ah battery.
I spent several periods of a few days last year with the solar panel and a few engine hours on passage completely adequate to run my fridge and other essentials.
Total investment, £45 for a 50W solar panel, £15 for a so-called 20W panel complete with regulator, £200 for the fridge.
I'm looking to add a portable lifepo4 pack, to run the heater into the Autumn.
I'm also open to the idea of an electric outboard for the tender which might complicate things.
Trident
Well-known member
And don't forget my current set up is 2100 w and 700ah - the aspiration for bigger (which I do have room for on a 50 ft cat) is only to be off grid in UK winters at 50 degrees north. There are lots of other solutions that work. If you move around under engine lots then do you need electrically made hot water ? If you are not totally against gas then you can have a gas oven and induction hob - my wife sometimes wishes we still had the size of the gas oven (which I have said I may address with a full sized domestic electric oven but I'd need a 5kw inverter for that - I installed that set up on a customers boat a couple of years ago and it ran fine but in hindsight I'd want to do it at 24v or 48v for the inverter as the heavy cable for a 5kw 12v inverter is a nightmare and now hugely expensive )One constant theme of many owners is the inability to add more solar.
Trident who is solely independent, in terms of his power usage - he is exclusively 'off grid' has, or will have 2.5 times (in watts for solar) of his Lithium battery capacity in amps.
2500 vs 900.
Trident's Law - perhaps.....?
So, very crudely
True for Trident but if you have 'too small' a battery bank you will need a greater proportion of solars, more than 2.5 times. Or, and more likely, if you cannot have 2.5 times the solar - you will need a bigger battery bank.
Jonathan
The biggest install I did was 1200ah lithium, 5kw inverter, 2400w solar , 5 MPPT chargers, and two 60a DCDC on a 44 foot cat but the owner really wanted to treat it like home, run everything at once and do whatever he liked - it almost worked but he was leaving the hot water on all the time with a 2kw element in an 80l tank which he had to stop doing as it ate power. But small changes to how one allocates power allows you to be independent with plenty of hot food, hot water and refrigeration etc.
By the way we make bread in the air fryer or oven very successfully - not sure how power compares to a dedicated bread maker but can't be much different. And few people run a 240v boat with the associated losses on the inverter - we have a 110l 240v fridge, a 110l 240v freezer and our tv, internet, PCs etc all on 240v simply because the fridge and freezer together from a domestic supplier cost 1/3 of what a 12v 45l Dometic fridge would cost and are better made.
The best thing for me is cooking a meal at lunchtime - using the induction hob or Ninja Foods and maybe other bits and pieces , drawing power for 30 or 40 minutes and when its sunny the batteries are full again before I've finished eating! We can "divert" 90 or 100 amps in the middle of the day direct to the domestic draw without taking anything from the battery - we normally see -5 to -15 amps from the battery if running the air fryer then - in the dark it -110 amps .
Neeves
Well-known member
If you are going to invest in Lithium in a big way, dispensing with gas, there are other costs - simply because of the opportunities that Lithium offers.
The inverter to start with, then the induction stove (that never crossed your mind when you had Lead) and maybe new saucepans. If you did not have an inverter already - you will now need 240v ac circuits and sockets (or you will not, conveniently, be able to use the power, almost, at your finger tips. Maybe, like us, you had an instant gas hot water system - that now needs replaced with a calorifier and an immersion heater (instant electric hot water heaters seem to need too much power). The B2B charger, though I note some don't use them. Solar might be cheap - but you need a decent display - or you cannot dispense with gas. One comment made - if you are being serious then you should consider 24v, rather than 12v. Suddenly all your 12v appliances are incompatible
We already carried an electric kettle, toaster and bread maker, for use in a marina when on shore power.
Some costs may be considered 'unfair', not considering 'like with like' but they are often costs you would be less likely to incur with Lead.
Jonathan
And I note now, our posts crossed, Trident is considering a full sized domestic oven!
Last edited:
