Lithium for the love of God

[barnakiel]

Yep. Those who need and can afford a 400Ah lithium bank are in one basket, those to whom a 35Ah lithium @ USD 650 gives second thoughts may be in another.

There is always a policy gap between high consumption / high production boats and low consumption ones. I am at the lower end of consumption spectrum in our own boat (our house battery is only 100Ah and our primary source is solar panels.

b.

[john61ct]

I have a disabled van-dwelling, otherwise homeless veteran acquaintance unable to lift and carry a 100+AH battery to be recharged in the church letting him live in the car park.
The vicar won't let him install solar.

He does need that capacity, sits on his Samsung phablet and old gaming laptop all day long to keep from going nuts, the more portable little power packs only last a couple hours.

With LFP I think he could manage it. I sure wish I could afford to buy an ArkPak 730 for him fitted with one of these https://www.campervan-hq.com/collect...tery-100ah-12v

[Pizzazz]

I like the idea of using a second battery (or your starting battery) to accept charge the large battery bank. You don't even need LiFePo4 for this. You can just cycle the starting battery from 85-to-15% through a DC upconverter to accept charge the main battery bank. It has benefits (short engine charging times, more cost efficient than buying and installing solar, much longer life for the main battery bank). The drawback or cost to the exercise is throwing away a $100 battery every two years or the cost of buying a new lithium battery. Great idea, I will look into it. You do not even need large switches since the currents will be small.

[john61ct]

Originally Posted by Pizzazz

I like the idea of using a second battery (or your starting battery) to accept charge the large battery bank. You don't even need LiFePo4 for this. You can just cycle the starting battery from 85-to-15% through a DC upconverter to accept charge the main battery bank. It has benefits (short engine charging times, more cost efficient than buying and installing solar, much longer life for the main battery bank). The drawback or cost to the exercise is throwing away a $100 battery every two years or the cost of buying a new lithium battery. Great idea, I will look into it. You do not even need large switches since the currents will be small.

What is this "accept charge"?

I'd not use a cheap Starter, since you'd likely murder it long before 2 years, really should be a true deep cycle, 2xGC2 at $180 much better value for a throwaway.

Main bank being LFP to me is the key to this, since it actually prefers to not sit at full.

Probably best if the target​ bank is smaller than source, not other way.

For me the target is a backup/reserve Lead bank, could always be used also for cranking, for me I have a self-jumping switch to House when needed and also keep a little PowerPack charged. But I still wouldn't intentionally Starter down, whole point is to reduce the odds of getting stranded.

[Pizzazz]

Here is the idea in more detail. You have 230 amps house and one 80 amps starter both at 20% state of charge. Start the engine, say typical 80 amp alternator and bring them up to 80-85% (when the Accept phase starts). Should take two hours or so. Then stop the engine and connect the starter battery via a DC upconverter set to 14.4V to charge the house in Accept mode. Should take 4-7 hours and use about 50 amps. Meanwhile the start battery (and the house can provide power as needed). At the end of the period you have the starter at 20%. Eventually this will kill your starter battery. May be one year, may be two, it depends. It is worth experimenting with a disposable $100 battery (it could be a third battery) to perfect the process and see if it is not too much of a hassle before buying a 7x costlier lithium battery which admittedly is far better suited for the application.

Such a setup allows you to do away with solar. Compare the cost of the disposable battery to the cost and lack of esthetics of installing solar panels. The idea makes sense but is a hassle.

[StuM]

Originally Posted by john61ct

I don't understand, isn't the specific issue there large vs small? What about a huge FLA s
vs small AGM?

Does the chemistry itself have a major difference wrt Peukert? Or does it vary by make & model like CAR?

AGM generally has a lower Peukert exponent that FLA. (Roughly 1/2 way between FLA and Lithium).

[john61ct]

Originally Posted by Pizzazz

80-85% (when the Accept phase starts). Should take two hours or so. Then stop the engine and connect the starter battery via a DC upconverter set to 14.4V to charge the house in Accept mode.

OK, I call that Absorption stage, CV constant voltage. Note depending on variables like charger ampsvs bank size and bank's CAR, you may need to stay in Absorb for some time to get to 85% when amps really drop down, like where I'd get solar to take over.

Originally Posted by Pizzazz

Should take 4-7 hours and use about 50 amps. Meanwhile the start battery (and the house can provide power as needed). At the end of the period you have the starter at 20%. Eventually this will kill your starter battery. May be one year, may be two, it depends. It is worth experimenting with a disposable $100 battery (it could be a third battery) to perfect the process and see if it is not too much of a hassle before buying a 7x costlier lithium battery which admittedly is far better suited for the application.

Such a setup allows you to do away with solar. Compare the cost of the disposable battery to the cost and lack of esthetics of installing solar panels. The idea makes sense but is a hassle.

The actual numbers would need to be tested and adjusted for each situation.

In my case I will have LFP anyway, this "topping up lead from LFP" is a side note, not to me a reason to go that way.

And I will still want solar, just won't necessarily have enough to reliably get to 100% as often as I'd like.

Again, if a Starter is involved, any smaller battery, it should be the target, not the source. $100 may be cheap for some, but I try not to throw money away, prefer to use the right tool for the job even when experimenting, and don't think a cheap starter would last even one year in the source role.

For me, my reserve/backup lead bank is deep cycle already, and I can crank off either that or the larger LFP House bank at will.

[leftbrainstuff]

Originally Posted by 44'cruisingcat

Is this a joke?

How about the double to quadruple cycle life?
The lack of self discharge?
The lack of sulphation?

No joke.

I've been dealing with bleeding edge battery technology off and on for 30 years. When someone else is paying for it then great i'm quite happy to be an early adopter.

Flooded lead acid still work fine for house battery use at a much better price point than all other options. I'd rather spend time and money on tech refresh that makes sense. Replacing pwm with mppt and tripling our solar capacity is where I'm spending my money this year.

Now if we're talking camera, drone, uav etc the fla is a very poor choice. Horse for courses.

I work for a major tech corp all week. I'm quite happy going old tech for my own vessel when the cost benefit of new tech warrants it

[leftbrainstuff]

Originally Posted by redpointist

Why would that be a joke? Maybe youd feel better if he specified "functionality that I actually need"? How many extra years would the extra cycles of lithium get him above fla if he's only cycling once per day? My 650ah of golf cart batteries cost under $600 so itd probably have to be a lot longer to be remotely competetitive (how much $ would 400ah lithium cost?). Your sulfation point is also basically about lifespan, and likely isn't a big factor if his solar panels get him back up to full charge daily, as ours do? Self discharge is also not an issue for us since the solar tops the batteries up daily.

Nicely put.

[downunder]

ExitStrategy

So much to your interesting post. It is worth a thread on its own.

[john61ct]

Originally Posted by StuM

AGM generally has a lower Peukert exponent that FLA. (Roughly 1/2 way between FLA and Lithium).

LFP is usually vanishingly close to zero right?

Does that mean splitting banks doesn't lose efficiency?

[exitstrategy]

Originally Posted by downunder

ExitStrategy

So much to your interesting post. It is worth a thread on its own.

Hehe, yeah I noticed the thread has taken a life of its own. I think I will wait a day or so and then try to re-post it again...

[exMaggieDrum]

Originally Posted by Pizzazz

I have looked and while I acknowledge the 20-25% capacity reduction for lead acid when supplying large currents, such situations on a sailboat are rare. Hence you are getting something that you do not need.

Yes, lithium is better and for some people having the best is a priority. But you cannot justify it this way unless you have some special high current need.

I don't know of any one going to lithium, with the exception of electric or hybrid electric boats, who put the need for high current availability anywhere on their list of requirements. You just don't have any gear on a "regular" propulsion cruising boat that needs that.

One of the big drivers is the available capacity along a much larger PSOC than with l-a or agm. With AGMs you have to start recharging at 50% PSOC. Lithium more like 20%. So a small Ah bank of lithium can replace double the Ah of lead acid. So that figures in to the economic, weight, space equation, which some leave out of their calculations.

And the hassle of disconnecting, moving, replacing, and reinstalling flooded cells is something I truly hate. For others it is not a big deal. I just want to do other things with my time. You can't really put that in dollars and cents unless my time and hassle can be put in dollars and cents. Or I have to pay someone to do it. I did it for a living for quite a while and it was something I hated to do even when getting paid for it.

This thread is becoming more of a conversation like those for anchors and religion. The bottom line is that lead acid flooded, or AGM, or lithium are perfectly good for some people and not for others. I did great with AGMs before in multi-year cruising mixed with multi-year marinas. There are some distinct disadvantages for them on sailboats though unless you have substantial charging that exceeds daily use in Ah. The advantages compared to the disadvantages of lithium are great for me but not for everyone.

[Oceansailor]

Originally Posted by 44'cruisingcat

The batteries in question were not LIFePO4.

And I wonder why in the hell Boeing engineers did not understand to use LifePO4 in the first place?

[Dave_S]

Dumb question.........

When a lithium battery is at 20% is it's output the same as an AGM at 50% or at 20%

Will the lithium batteries run the electrics, start engines etc at 80% discharge.

In other words, is it functional at that level of charge.