Charging LiFePo4 Batteries With Just Solar

dLj · Friday at 10:56 AM

You can set up your boat any way you want to - it's your boat.

Think about the systems you will run, what each criticality is, and how much do you want to be a slave to those systems - meaning you have to keep all sorts of things in mind and care for them as they dictate....

I can tell you how my boat is set up and how much it fits my preferred lifestyle onboard. I can't tell you what your preferred onboard lifestyle should be...

dj

dLj · Friday at 11:14 AM

GeneraiT001 said:
I was thinking more in terms of the logistics (feasibility) upside/downside....practicality?

That's exactly what I was addressing - YOU define your practicality on your boat.

There are SOOOOO many ways to set up a boat. All have their good and bad points.

The systems I have set up on my boat work for exactly how I want them to work. I have refrigeration with ice making capability. I have great cooking capability. I have the ability to charge all my electronic devices like cell phones, computers, electric toothbrush, more. I have hot and cold running water. All of my systems are set up to be simple to use, simple to monitor, and simple to keep running. But there are systems I don't have.

I don't have a water maker. Instead I have the water storage capacity to go anywhere I want. That may change one day, but for the foreseeable future, no water maker insight.

I don't have a dive compressor - I do have a hooka so I can do my hull cleaning and could clear a fouled prop if needed. But while I have done scuba, I like it, I was never bitten with the bug to do it all the time. So I snorkel - that serves me.

I'm sure lots more things some folks want that I don't care about.

GeneraiT001 said:
Looking further into this it seems that unless your getting a 7,500 - 10,000 watt generator your not getting much in the way of charging amperage

That's ridiculous. I have a portable Honda e2200i - that's 2200 watts. I almost never use it, but when I do, I can take care of pretty much anything I need.... You are getting your brain twisted... (not meant to be offensive)

dj

dlochner · Friday at 11:22 AM

As @dLj alludes to, designing an electrical system is sometimes like diving down a rabbit hole into Alice's Wonderland.

According to Nigel Calder and my own experience, you can expect on average to get 3 times the nominal wattage per day from your solar panels. With a panel size of 400 watts you can expect to get 1200 watt hours per day or about 100ah per day. So, in theory running on just solar is possible, until a bad stretch of weather comes along and depletes your panels at which point it will take another 4 days of charging with no usage. Which is a pretty untenable situation for an ocean passage of several weeks.

It would also not be wise to rely on a single charging source for a vital system.

dLj · Friday at 11:58 AM

GeneraiT001 said:
LOL...my math got skewed somewhere wrt charging Amps ? Of course probably makes more sense to connect the electrical system into it via AC input

Hahaha - it happens...

GeneraiT001 said:
So, what is your setup for electrical?

You aren't going to replicate my system. But the basic philosophies of how my system is set up would be a very good guideline for you as my set up is for an off shore sailing application. Just as an FYI - it was designed by one of the best marine electrical design engineers found anywhere... So I can't take credit for any of this design. But I can say after several years living with it - it's amazingly well designed. The guy who did the design actually came to my boat and spent a day on my boat looking at everything that existed, talked with me about what I wanted to do, asked me about my preferences and then designed the system specifically for my boat and how I like to sail.

I wanted reliability, ease of use, low cost of operation, a system to be used off shore and to handle a liveaboard lifestyle. That's in a nutshell.

I have 400 Ahr of LiFePo house batteries. I have an AGM start battery, and two AGM batteries that run my windlass and bow thruster. Both of these lead acid systems are charged off my LFP house batteries through Balmar Duo-charge DC to DC chargers. This keeps my lead acid batteries 100% fully charged at all times. This fact will allow my lead acid batteries to give me 12 to 15 years of full time use before I will have to replace them.

All charging systems charge my LFP house batteries. This includes a wind generator, a 385 W solar panel (this is the best!), my alternators, shore power, or my portable generator. If I ever add in any other system: more solar, a hydro generator, whatever - I can just run the controller straight into my house bank and I don't have to worry about a thing. Hook it up and run.

I have twin 120A alternators (240A total possible output) that are externally regulated (I use a Wakespeed 500) and each has a Sterling Alternator Protection Device to guard against an abrupt current shut down (this is a redundant system as the Wakespeed also provides this). I have them throttled back to 180 A total output to keep them cool and keep them running for years.

I have a Zantrex 2kv inverter charger that I use to generate 120V AC for any AC equipment I may need - power tools, chargers for things that need AC power, my Starlink - I don't know what else....

Essentially I have redundant systems, multiple ways to charge my house batteries and the whole setup is highly reliable. I monitor my house batteries so I can see exactly how much power I'm either drawing or charging and the state of charge of them in real time.

I also have a heat pump that does both Air Conditioning and Heating but I virtually never use it. But it is a nice to have when I really want it... My hot water tank runs off my engine cooling system or off 120 AC.

I have two heads, both are composting heads. I'm a major fan - I'll never go back to a traditional marine head with holding tanks and all that... I save so much space using composting heads and have so much less hassle and NO smell... yeah, I'm a convert...

Propane for cooking. I've considered induction - it's a great system. However, induction doesn't work for how I like to cook.

dj

BarryL · Friday at 12:23 PM

Hello,

Just some of my thoughts.
A 400AH LiFePo4 battery has about 320 useable AH (80% discharge)
Adding a DC DC charger is not that difficult or expensive. That would allow your alternator to charge your engine starting battery and the engine start battery can charge the 400AH house bank.
If you plan on living aboard your boat you really need to be able to generate ALL the power you need each day. Otherwise you will eventually run your battery down and that will force you to do something strange or something you don't want to do. If you're going to have 400W of solar and you will use 150AH / day either you need to decrease your electrical usage or add additional charging (wind, more solar, alternator, etc.).Some days you will produce more solar, other days you produce less. That's why you store the energy in a battery. If you run a deficit every day you have mismatched system.
If you're not living on the boat but aboard for a few days or week, and if you'll be spending some time in a marina with AC power, then you really would want to have a battery charger.

Good luck,
Barry

GeneraiT001 said:
In an effort to avoid all the changes/complications/expense in adding a bigger capacity alternator + external regulator + wiring is it feasible (and sane) to just totally isolate the LiFePo4 batteries from the mix and just have the LiFePo4 isolated for house duty only. This should be easy to do (I think)

So, lets say I have a 400 Amp Hr LiFePo4 battery and use about 150 Amp Hrs/Day. If I have 400W of solar probably putting out a combined daily average of about 10 Amps/hr x 8hrs/day....so I might get a useable 80 Amps/day to recharge the battery....which means I am out of battery power in about 4-5 days. Does that math sound about right?

So to do that I would need a portable generator to top up those batteries or do the alternator thing? I suppose I could add more solar as well?

dLj · Friday at 12:55 PM

BarryL said:
Adding a DC DC charger is not that difficult or expensive. That would allow your alternator to charge your engine starting battery and the engine start battery can charge the 400AH house bank.

While sure this can be done. About the only thing going for it is an inexpensive initial cost. But you will destroy that LA battery in a very short length of time and it will have to be replaced - over and over again... Then you have the daily operating costs - you'll have a lot more fuel consumed in charging that system. You'll have a lot more wear and tear on your engine doing it this way.

I really don't understand why people even entertain this kind of set-up. To save some money in upfront costs? Then waste it in all the other costs associated with running this system? It really makes no sense to me...

dj

dlochner · Friday at 1:13 PM

dLj said:
I really don't understand why people even entertain this kind of set-up. To save some money in upfront costs? Then waste it in all the other costs associated with running this system? It really makes no sense to me...

I think it depends on use and long term plans. If the boat lives on a mooring and only day sails, weekend trips, or short vacations it can make sense. Another case is if it part of a long term upgrade that will last over a couple of seasons, start with just solar and DC-DC charger, then add a smart battery charger, then high output alternator. Otherwise, I agree with you, if longer term cruises are on the near horizon, then it doesn't make any real sense to go that alt to start battery to LFP route.

dLj · Friday at 1:19 PM

dlochner said:
I think it depends on use and long term plans. If the boat lives on a mooring and only day sails, weekend trips, or short vacations it can make sense. Another case is if it part of a long term upgrade that will last over a couple of seasons, start with just solar and DC-DC charger, then add a smart battery charger, then high output alternator. Otherwise, I agree with you, if longer term cruises are on the near horizon, then it doesn't make any real sense to go that alt to start battery to LFP route.

Of course - but the OP in this case has stated his long term goal - and it's not far off - like in the next year or two - will be to head off and live on the boat, sail to the Caribbean, then head over to the west coast and sail up to Canada. That plan is long term live aboard, ocean sailing....

It is specifically within that context I'm replying...

dj

dLj · Friday at 1:36 PM

dlochner said:
I think it depends on use and long term plans. If the boat lives on a mooring and only day sails, weekend trips, or short vacations it can make sense. Another case is if it part of a long term upgrade that will last over a couple of seasons, start with just solar and DC-DC charger, then add a smart battery charger, then high output alternator. Otherwise, I agree with you, if longer term cruises are on the near horizon, then it doesn't make any real sense to go that alt to start battery to LFP route.

Let me remind you - here is his stated plan:

"My plan is too take a year to get familiar with the boat then sail it down to the Caribbean, stay awhile, then through the Panama Canal and up the west coast to Nanaimo, BC."

So one year to get familiar with the boat - then off to some pretty serious long distance sailing.

In my opinion, it's a waste of time and money to go to a system of charging those LFP batteries through a LA battery.

He really should be looking at a minimum of getting his current alternator to be an externally regulated and charge directly those LFP batteries. Get the system set up from the get go with that system at least partially in place. Then he can begin building the system as need be down the road as money and time permits- but you need the correct backbone built to start with. Or you are just chasing your tail....

dj

brazenarticle · Friday at 3:00 PM

I entertain this kind of setup because it works well for my sailing/traveling life. 600 amps of lifepo4 storage (2 300 amp batteries), 1200 watts of solar (2 strings of 3 200 watt panels in series through 2 mppt controllers) and a single Victron DC to DC charger keep me powered almost all the time. For a string of cloudy/rainy days I have a 2000 watt generator but I haven't needed to use it in months. I rarely use a slip, when I do usually I don't bother plugging in to electric.
After looking at external alternators and upgraded alternators which require serpentine belts, upgraded pulleys and new alternator mounts the accumulated cost was ridiculous for the benefit gained.
Traveling the ICW is a lot of motoring or motor sailing. Charging the LifePo4 with the standard alternator and a DC to DC charger doesn't take any more fuel than moving the boat. The load on the engine with the standard alternator isn't increasing wear and tear, it is being used as designed. My AGM start battery has survived beyond "a very short length of time" without replacement.
I haven't found any "other costs associated with running this system" .

dlochner · Friday at 3:15 PM

brazenarticle said:
I entertain this kind of setup because it works well for my sailing/traveling life. 600 amps of lifepo4 storage (2 300 amp batteries), 1200 watts of solar (2 strings of 3 200 watt panels in series through 2 mppt controllers) and a single Victron DC to DC charger keep me powered almost all the time. For a string of cloudy/rainy days I have a 2000 watt generator but I haven't needed to use it in months. I rarely use a slip, when I do usually I don't bother plugging in to electric.
After looking at external alternators and upgraded alternators which require serpentine belts, upgraded pulleys and new alternator mounts the accumulated cost was ridiculous for the benefit gained.
Traveling the ICW is a lot of motoring or motor sailing. Charging the LifePo4 with the standard alternator and a DC to DC charger doesn't take any more fuel than moving the boat. The load on the engine with the standard alternator isn't increasing wear and tear, it is being used as designed. My AGM start battery has survived beyond "a very short length of time" without replacement.
I haven't found any "other costs associated with running this system" .

Your system works because the solar panels produce on average over ~~900~~ 300 ah per day (which probably exceeds your daily consumption by a lot) and you motor a lot on the ICW. The OP is planning on long offshore passages with fewer solar panels, an entirely different case.

Adding a high output alternator and regulator runs about $1500. How much did you spend on your 6 solar panels?

Richard19068 · Friday at 7:11 PM

dlochner said:
According to Nigel Calder and my own experience, you can expect on average to get 3 times the nominal wattage per day from your solar panels. With a panel size of 400 watts you can expect to get 1200 watt hours per day or about 100ah per day.

dlochner said:
Your system works because the solar panels produce on average over 900 ah per day (which probably exceeds your daily consumption by a lot) and you motor a lot on the ICW. The OP is planning on long offshore passages with fewer solar panels, an entirely different case.

Dave,

In your one post you say a 400 watt panel will provide about 100ah per day.

In the other you say 1,200 watts of solar panels provide 900ah per day.

Based on the assumption in the first post, 1,200 wats of solar panels should provide about 300ah per day

Am I missing something here or is my math bad this evening?

Thanks.

dlochner · Friday at 7:31 PM

On average a solar panel will provide about 3x the nominal power of the panel. A 100w panel will produce about 300wh of electricity. A watt is calculated by multiplying the voltage by the amperage. Do the alegebra, 300/12 =25 ah.

For the examples I used: 400 x 3 = 1200wh 1200wh/12v = 100ah

1200 w panel x 3 = 3600 wh 3600/12 does indeed equal 300ah a day. Probably still more power than most people use in a day.

So, no your math is OK, mine is off. It is always good to check my math.

I edited my post.

MFD · Friday at 8:16 PM

Isolating the house bank as part of a LifePO4 upgrade is quite common as it reduces both initial expenditures and also reliability risks.

I can not speak to your overall electrical energy consumptions needs, and requirements to replace that.

However it is quite common for people to retain AGM start batteries for their engines, charged directly via the ‘as-built’ system and simply insert a DC=>DC charger from there to the house bank to pick up the extra and not have to deal with many other things.

dLj · Saturday at 6:05 AM

MFD said:
Isolating the house bank as part of a LifePO4 upgrade is quite common as it reduces both initial expenditures and also reliability risks.

The generic "reliability risk" I'm assuming you are talking about is burning out your alternator. Isolating the house bank - you mean by going through a LA battery?

As far as "quite common" - there are a whole lot of things that are "quite common" that really are not the better way to do things...

MFD said:
However it is quite common for people to retain AGM start batteries for their engines, charged directly via the ‘as-built’ system and simply insert a DC=>DC charger from there to the house bank to pick up the extra and not have to deal with many other things.

Yes, this is a common thing to do currently. It's really penny wise and pound foolish in all but a few specific use cases. I think a lot of why this started was when LFP batteries started getting put in boats, there was not a lot of experience around and a lot of DIY'ers did this to avoid problems that we now know how to deal with. But the extensive use of this early in the game has now made this a supposedly "acceptable'" way to do this. For sure there are cases where this is perfectly acceptable way to do this, but for a liveaboard, off-shore sail boat - it is not. You'll be constantly fighting with that system and getting nickel and dimed until you really just go to where you should have been in the first place.

Running LFP house batteries, and running LA batteries (one or more) then you should begin your fundamental design aimed at an externally regulated alternator and running DC to DC charging of the LA off the LFP battery system. To efficiently build an electrical system over time, it's best to start based on the correct fundamental base design upon which you can then add in the appropriate bits, parts and upgrades.

dj