Just completed upgrade from AGM to Lithium

[Stu Jackson]

Originally Posted by hpaabor

I'm used to the "marine" version of things being more expensive but if I understand AH at all the 8000 AH battery in my car is worth about 4 times what I paid for entire car if I go by the marine price. Anybody bored enough to explain the apples and oranges in this comparison?

8000ah car battery? What kind of car?


Answer: don't buy batteries at a marine store. Ever.



Battery makers actually sell their batteries at non-marine stores. Marine stores slap their labels on other people's products and mark the up to a ridiculous extent.

[BoatBumm]

I’m thinking of switching to lithium too. For those of you who have more of a DIY approach to this sort of thing, Will Prowse has an EXCELLENT YouTube series about all things lithium, including controllers, solar panels, sources of LiFePO4 batteries, BMSs, inverter/chargers, etc. He’s an RVer, but most of what he features is applicable to marine stuff too. I have no connection to him at all, but have learned a lot from watching his videos. He routinely disassembles LiFePO4 batteries to see what’s inside that plastic case - sometimes good, sometimes less so.

[Pete7]

Originally Posted by Captain Scott

I am choosing options on a new boat being built for me now (Completion this December!) and have looked at most of the electrical options.... I will say this; if the faster charging numbers are accurate as stated in this thread, then the numbers say 1200 hours a year on your genny compared to 244. For me, the cost of a genny works out to about $1 and hour and then fuel is about $3 (.8 GPH x $3.75 a gallon) so at $4 an hour use cost...... Cheers, Scott

Scott, there might be another advantage if your future boat doesn't have a genny. The faster charging means that you are not sat watching FLA or AGM batteries drop to a trickle for the last 10-15% even if more power is available. Or worse still not reaching fully charged frequently. So LFP don't need to be fully charged, but if the bank is full, well that's a full bank to play with not 85% and a cut off 50% ish.

I watched 18A go into the LFP and only limited due to the 20A max from MPPT, suddenly stop. Battery full and MPPT dropped to a low float voltage just supplying house loads of 2A. Previously that would have dragged on for a long time with the current dropping slowly down in single figures.

Pete

[rslifkin]

Originally Posted by Pete7

Scott, there might be another advantage if your future boat doesn't have a genny. The faster charging means that you are not sat watching FLA or AGM batteries drop to a trickle for the last 10-15% even if more power is available. Or worse still not reaching fully charged frequently. So LFP don't need to be fully charged, but if the bank is full, well that's a full bank to play with not 85% and a cut off 50% ish.

I watched 18A go into the LFP and only limited due to the 20A max from MPPT, suddenly stop. Battery full and MPPT dropped to a low float voltage just supplying house loads of 2A. Previously that would have dragged on for a long time with the current dropping slowly down in single figures.

Pete

I would think the charge curve and PSOC tolerance helps more if you have a genset but no solar. Topping off lead acid with solar is no big deal, but trying to get it topped off with a genset sucks.

In general, the bigger the boat, the smaller the advantages of lithium in my mind (unless you have tons of electric needs and want to rarely or never run a genset). Bigger boats are less likely to care about the weight of a big lead acid bank. Bigger boats also tend to have more space for big solar setups, etc. making it easier to take good care of the lead acid batteries.

On my own boat, I'm staying AGM for now for a couple of reasons: I'd love the lighter weight of lithium (or extra capacity at the same weight), but it's a lot of cost and would require complicating my charging setup a bit more (would need to do something about the internally regulated alternators and ACRs for engine charging). Plus my systems are already capable of taking decent care of lead acid and not abusing them with excessive PSOC.

[Pete7]

Originally Posted by rslifkin

In general, the bigger the boat, the smaller the advantages of lithium in my mind (unless you have tons of electric needs and want to rarely or never run a genset). Bigger boats are less likely to care about the weight of a big lead acid bank. Bigger boats also tend to have more space for big solar setups, etc. making it easier to take good care of the lead acid batteries.

Until recently I hadn't really appreciated the advantages to a smaller yacht.

Sure on a large yacht being able to run the genny, make water, do laundry and charge the batteries first thing before "kicking back for a cold one" makes LFP ideal for reducing the engine run time.

For the smaller yacht there are also some real advantages in weight saving and enabling you to run main electric items like the toaster, induction hub, wife's hair dryer etc for the first time away from shore power. Try even a medium sized inverter off a pair of FLA and the voltage drop will be horrible, the inverter liable to trip and you really aren't doing the batteries any good.

We have started cautiously with a LFP Hybrid bank of 205Ah to see how this goes during the summer, whilst having room to expand if we need more capacity next winter. When not on board the LFP is disconnected so the solar doesn't cook it, but leaves the FLA battery to run the bilge pump etc. This was also the trigger to move the house bank out of the engine space which regularly reached 32'c even in the UK.

Pete

[rslifkin]

Originally Posted by Pete7

Try even a medium sized inverter off a pair of FLA and the voltage drop will be horrible, the inverter liable to trip and you really aren't doing the batteries any good.

Right there is why I've got AGMs. I'd have to do some work on my house bank mounting spot to make it suitable for FLA anyway, and gel is no better than FLA at handling short bursts of heavy load. My house bank runs the windlass as well as the inverter, so the AGMs do a better job of dealing with those bursts of heavy load (bank is 415ah at 12v). Lithium would be even better still, but the AGMs are sufficient in that department.

[newhaul]

One thing I would like to ask .
Does anyone know of a person that ever has switched from lifepo4 to any varient chemistry of lead acid batteries?

Me neither .

[rslifkin]

Originally Posted by newhaul

One thing I would like to ask .
Does anyone know of a person that ever has switched from lifepo4 to any varient chemistry of lead acid batteries?

Me neither .

It's unlikely. Most of lead's advantages are around cost and systems simplicity, so once you get a setup together that works well with lithium, there would be little reason to switch to lead.