Update on Battery Choices

[Seevee]

Bigger boats with 24 v use more current, smaller boats with 12 v less current, generally, so I can't see how that matters. If you are a liveaboard and plugged in, then you don't need Lithium, or if your cruising is from one dock to another, ditto. An inverter/charger is commonplace on trawlers, where charging is powered by a genset or shore power. If you end up using the genset, then of course less run time is a virtue. How could it not be? And if you are using a genset, then in addition to a fairly common 100 amp charging capacity from the inverter/charger, you can daisy chain Sterling chargers to get extra capacity. That is how I get 180 amps without the CAT running.

My installation used everything I already without modification, so was essentially drop in. I chose to add additional charging capacity, which was about a three hour job. 3,000 charge cycles from now, and a few thousand hours less genset runtime I'll let you know whether I'm still happy, because that would be the minimum lifespan I would expect.

Dumb question....


Should one convert to a 24v system, so the charger is 24v and the battery bank is wired for 24 volt, how does one wire for the 12v appliances/radios, etc?

 

[ksanders]

Bigger boats with 24 v use more current, smaller boats with 12 v less current, generally, so I can't see how that matters. If you are a liveaboard and plugged in, then you don't need Lithium, or if your cruising is from one dock to another, ditto. An inverter/charger is commonplace on trawlers, where charging is powered by a genset or shore power. If you end up using the genset, then of course less run time is a virtue. How could it not be? And if you are using a genset, then in addition to a fairly common 100 amp charging capacity from the inverter/charger, you can daisy chain Sterling chargers to get extra capacity. That is how I get 180 amps without the CAT running.

My installation used everything I already without modification, so was essentially drop in. I chose to add additional charging capacity, which was about a three hour job. 3,000 charge cycles from now, and a few thousand hours less genset runtime I'll let you know whether I'm still happy, because that would be the minimum lifespan I would expect.

The idea of reducing generator run time for many with a 12 volt charging system and “standard” inverter/chargers made by folks like magnum, outback, Xantrex is in my opinion not reality, and here is why.

Lets take my battery bank and charging setup, as it is pretty typical, and it represents the largest charger that I have seen on a 12V boat.

My FLA L16 batteries are rated by the manufacturer for bulk charging at 100 amps. My bank consists of four batteries in a series parallel configuration equaling 860 amp hours. Since I have a series parallel setup my max charging current is now 200A

My charger is rated at 150 amps, and in addition to that while cruising I have a 150 amp BALMAR alternator.

My loads are averaging between 30 and 50 amps DC at any given time. This is the reality of my 47’ Bayliner running all LED lighting, three fridges/freezers, icemaker, and three displays for the navigation system, plus my KVH VSAT system.

With this setup which again represents equal to or larger than the largest charging capability I have seen on a 12 volt boat I do not exceed the 200 amps of maximum charging current into my batteries. That is if I am running Both my generator and my main engine, which is not how I generally run.

If I just run my generator my 150 amp charger maxes out at around 120 amps of actual battery current.

Going to a LIFEPO4 solution would NOT help unless I bought another high capacity charger and ran it in parallel.

Yes theoretically when my bank reaches about 85% charge my chargers go from bulk to constant current mode, and that might reduce my generator run time a little, but in reality most boaters, (myself included) do not run their generator long enough just to charge batteries in the constant current mode. They generally just chase the approx 50 to 85% window.

You posted that your FLA battery system was over 1300AH at 24 volts.

I would submit that if your rating of your old battery bank is correct then you never exceeded your charge acceptance capacity with your 180 amp charger capacity either, and therefore going to LIFEPO4 technology would not reduce your generator run time significantly.

I might stand corrected on that last statement as I do not know your exact FLA battery configuration, but I do not think so as I thought out how you would build a 1300 amp hour bank at 24 volts pretty extensivly.

 

[Woodland Hills]

Dumb question....


Should one convert to a 24v system, so the charger is 24v and the battery bank is wired for 24 volt, how does one wire for the 12v appliances/radios, etc?

I have a 32v house battery bank and I use 12v “buck” converters to drop the voltage to 12v for instruments and electronics. They are available on Amazon and are reasonably priced. I’ve never had one fail yet. I have 4 8v Rolls FLA batteries and a Victron Bluetooth monitor to keep an eye on them. BTW each battery weighs 127 lbs: more lead means more capacity!

My inverter bank is 24v and I use 8 AGM batteries and another Victron Bluetooth monitor. This bank is also used for the 24v bow thruster as well as the 110v loads: lights, tv, fridge, freezer, etc. we shut the generator off last night at 9:00pm and had 58% capacity remaining at 11:00am today when I fired up the generator again. The 32v bank had 82% remaining.

 

[Delfin]

The idea of reducing generator run time for many with a 12 volt charging system and “standard” inverter/chargers made by folks like magnum, outback, Xantrex is in my opinion not reality, and here is why.

With the AGM bank, IF I wanted to fully recharge them, which is the only way to make them last, charging with genset + alternator was a daily 5 hour process. This is because LA batteries have such a huge taper of charge acceptance when they get over 85% capacity. LFP batteries don't have that problem. My run time on a daily basis now is 2 hours, which replaces the 300 Ah we daily use.

While I respect your opinion, I guess I'm surprised that it seems resistant to actual data derived from actual usage of a technology I gather you have no experience with.

 

[ksanders]

With the AGM bank, IF I wanted to fully recharge them, which is the only way to make them last, charging with genset + alternator was a daily 5 hour process. This is because LA batteries have such a huge taper of charge acceptance when they get over 85% capacity. LFP batteries don't have that problem. My run time on a daily basis now is 2 hours, which replaces the 300 Ah we daily use.

While I respect your opinion, I guess I'm surprised that it seems resistant to actual data derived from actual usage of a technology I gather you have no experience with.

Thanks! My experience is with AC and DC power systems, on a professional and personal level. Thats why I ask the questions and derive the opinions i have.

You have shed some significant light on the issue, that being the charge time between 85% and 100% where the charge acceptance rate of the LIFEP04 exceeds the FLA batteries. That is an area more difficult to quantify.

I really respect your hands on experience and am glad that LIFEPO4 works for you to lower generator run time. Myself I have not seen up fronty data that justifies the several times increase in cost VS FLA

 

[Delfin]

Thanks! My experience is with AC and DC power systems, on a professional and personal level. Thats why I ask the questions and derive the opinions i have.

You have shed some significant light on the issue, that being the charge time between 85% and 100% where the charge acceptance rate of the LIFEP04 exceeds the FLA batteries. That is an area more difficult to quantify.

I really respect your hands on experience and am glad that LIFEPO4 works for you to lower generator run time. Myself I have not seen up fronty data that justifies the several times increase in cost VS FLA

Value is in the eye of the beholder. I've posted the attached before, but it illustrates why LFP has fans, who feel the cost is worth it. The bank, in the chart, was at 35% SoC, or 380 amps down.

 

[roddy]

Have 6 6 volt GC2's at 220 AH for house loads and 1 8D start battery.
All were new last year.
Use appox 100 - 160 AH overnight main variable is ambient temperature and fridge and freezer run time.
NEMA 2000, WiFi booster and one chart plotter runs on low brightness if anchoring.
Have sleep apnea so my machine runs off inverter all night.
Plus 5 minute run of microwave to get baked potatoes primed for barbecue
and 2 coffees in morning.
Batteries had there work cut out!
Installed 620 watts of solar 3 weeks ago with Victron MPPT Bluetooth controller.
This was best boat bucks I've ever spent!
Peak production in clear sunshine is 542 watts. However don't get stuck on peak power. What is important is kilowatts produced daily.
it starts off at daybreak with 10 watts and finishes at twilight. This averages out to 11 kilowatts per week. Even if its raining there still pumping out 100 - 150 watts. Probably could produce more kw but eventually controller goes into float mode by 1400 dropping current to 2 or 3 amps.
PV carries entire house load in float mode no problem!
Getting back to batteries using gen-set to get bulk charge in and letting PV do absorption is the smart way to operate.
My next batteries will be two or three, 200 Ah, LifePO4's at 55 lbs. At 66 I cant manhandle the 8D and don't want to fight with GC2's.
https://www.lynaclithium.com/product/12v-240ah-ltt/

 

[ksanders]

Value is in the eye of the beholder. I've posted the attached before, but it illustrates why LFP has fans, who feel the cost is worth it. The bank, in the chart, was at 35% SoC, or 380 amps down.

What you have posted is REALLY interesting!

you have went from 35% to I’m assuming 100% in about two hours, replenishing from your post 380 amp hours.

That is REALLY cool!

Now lets do some math and pretend you had the same 600AH FLA bank and see where it takes us. As a FYI I hasve no pre-concived notitions as I write this. It will end up where where it ends up

so...

85% of 600AH is 510 AH. Since we started at -380AH we are looking at 130 AH on a FLA where the charger would transition from max output to a constant current mode. Lets call that 45 minutes.

so... if you had FLA batteries after 45 minutes you would have reached 85% and switched to constant current mode.

Now is where it gets fuzzy for me but generally from 85% to 100% is about 2.5 hours on my bank which is admittedly different than yours.

so... We are looking at .75+2.5 or 3.25 hours of generator run time for a FLA system to theoretically do what you were able to accomplish in 2 hours.

That is a BIG savings in generator run time, and I see your argument for LIFEPO4 on the basis of generator run time all other things being equal.

All that said, what I do is run most of the time between about 50% and 85% specifically to reduce running the generator when the charger is in constant current mode, but on the flip side of that I recognize that I need a larger bank to be able to run within that range without reducing battery life. Also to be honest in the evening I often run my generator to “top off” my bank so that I only go to 50% by morning.

Again... THANKS for sharing. You have enlightened me.