Lithium ion house battery bank disappointment

[JC Reefer]

Originally Posted by Hans Etter

> >
> >Bulk 14.4V
> >Absorb 14.6V
> >Float 13.6V

Don’t float lithium batteries. They like to be cycled or stored around 50%. Read a few different packs and you see some warnings about floating and storage.

[JC Reefer]

Here is a great place to start reading if one wants to start learning about LFP -https://marinehowto.com/lifepo4-batteries-on-boats/

[ronstory]

Ok, quoting Maine Sail is almost cheating. But you would be right.

[CatNewBee]

When used while sailing, they are both - cycled ( during the night ) and in float ( during the day, when solar has filled them up and continues to feed the on board systems ). This is the normal use pattern when cruising. You should just configure your gear to the right voltages.

If you go to float after finishing charging at 14.4...14.6V, and the charger switches to float, they discharge down to the float level, there is no charge current going in, they just stop discharging at float and keep this cell voltage, the cell modules stop equilizing, everything is fine, excess energy goes to the on board devices.

In the evening the battery discharges while supplying the fridges / freezers / ac / nav lights / instruments / fog horn / party equipment / under water lights / radar / hot water boiler...

[arsenelupiga]

Originally Posted by CatNewBee

When used while sailing, they are both - cycled ( during the night ) and in float ( during the day, when solar has filled them up and continues to feed the on board systems ). This is the normal use pattern when cruising. You should just configure your gear to the right voltages.

If you go to float after finishing charging at 14.4...14.6V, and the charger switches to float, they discharge down to the float level, there is no charge current going in, they just stop discharging at float and keep this cell voltage, the cell modules stop equilizing, everything is fine, excess energy goes to the on board devices.

In the evening the battery discharges while supplying the fridges / freezers / ac / nav lights / instruments / fog horn / party equipment / under water lights / radar / hot water boiler...

i observe my victron mppt and after going to float, starts cycle again after larger energy consumer turned on and voltage falls under certain level in same day.

So it appears one can get multiple cycles of charging in a day. That would not be good for lithium....

[CatNewBee]

you have 5000+ cycles down to to 20% SOC, what is not good about it?

LFP are not made forever, but they last 10+ years with heavy duty cycles. It is OK to use them.

We mount them not to pamper them all day long, but to use them all the time heavily, so set up and forget.

[Pizzazz]

Originally Posted by CatNewBee

you have 5000+ cycles down to to 20% SOC, what is not good about it?

Do you notice that 5,000 discharge cycles is approx. 15 years, cycling the batteries every day. No marina stays, no refits, just cycling every day. It is not bad but few of us will keep a boat/live that long. If someone told you the car engine is good for 1 million miles and typically you sell your car after 100K miles, would you pay 5x for the longer lasting engine? It is a hard sell. You can argue about resale, etc. but still.

[44'cruisingcat]

Originally Posted by JC Reefer

Don’t float lithium batteries. They like to be cycled or stored around 50%. Read a few different packs and you see some warnings about floating and storage.

I've seen these blanket statements too. But you CAN float lithiums. It's simply a matter of setting the right float voltage, where the batteries are not being charged, but loads are mostly being carried by the solar.

Typically this would only happen for a few hours per day, then the solar will no longer meet loads and the batteries will start to be used.

Doing this will result in shallower cycles and longer battery life.

[contrail]

Would firefly's work the same way? If so, what would the recommended voltage be

[missourisailor]

Originally Posted by contrail

Would firefly's work the same way? If so, what would the recommended voltage be

Before I bought mine, I researched FireFly's for several years.

And the answer is MAYBE.

The factory says it's okay to float, but recommend to avoid if possible.
After pushing the issue, they admitted short term floats (a few hours to a couple of days) would likely cause no harm. But they stressed for longer times (weeks or months), they need to be removed from charging sources.

[john61ct]

Originally Posted by contrail

Would firefly's work the same way? If so, what would the recommended voltage be

Firefly's marketing dept raised the **acceptable** float voltage up to 13.5V maximum, but 13.2V is still recommended for longevity, and engineering recommends no Floating at all as the ideal, just like with LFP.

It really doesn't take much to isolate your super-expensive bank from further charging while a cheap batt+charge source carries loads.

A simple adjustable LVD then reconnects the loads buss once voltage drops a bit.

[john61ct]

Originally Posted by Pizzazz

Do you notice that 5,000 discharge cycles is approx. 15 years, cycling the batteries every day. No marina stays, no refits, just cycling every day. It is not bad but few of us will keep a boat/live that long. If someone told you the car engine is good for 1 million miles and typically you sell your car after 100K miles, would you pay 5x for the longer lasting engine? It is a hard sell. You can argue about resale, etc. but still.

I have multiple off-grid living spaces, some mobile some not, that are serviced by LFP.

I plan on my LFP banks lasting much longer than most of their current "vehicles", and they are easily moved, along with the critical chargers and protective gear, all part of the design.

So really a better analogy than a vehicle-specific ICE, would be a portable Honda gennie, and yes I do spend more on those, rather than a $300 knockoff at Home Depot.

[daletournier]

As I previously stated I'll be heading the lithium way down the track (5-7years).

Im not sure if a link to Mainesails article as been posted before, it's a long read but a good one.

https://marinehowto.com/lifepo4-batteries-on-boats/

I'm not an earlier adopter, yes I understand Lifepo have been around for quite sometime BUT for marine they still fall under the early adopter umbrella in reference to the cruising world.

As in the above article Mainesail points out that a Diy application is a great way to loose alot of money, he dosent 100% understand them yet (his own words) and this guy has probably forgotten more than I'll ever know when it comes to batteries and 12v systems.

Good on all the guys that have them up and running well. Personally I'm waiting for them to get to a point where they are very mainstream, plug and play and even more heavily discounted.

IMHO there's many cruisers that don't understand traditional battery charging and setups, batteries are getting murdered in all the seas and oceans of the world everyday.... what can the masses do with Lifepo?

[fxykty]

Is our NZ price of batteries reasonable? We’ve got an AGM 12V 660 AH house bank that is going to need replacing soon. Usable AHs are 330 and sufficient for our usage.

6 Volt Trojan T-105 225 AH batteries are 282.61 NZD ~200 USD each, so 6 batteries for 12V 675 AH about 1200 USD.

12 Volt AGMs 100 AH are ~ 250 USD each, so 7 batteries for 700 AHs about 1750 USD. Is the extra cost over the Trojans worth not having to water batteries?

400 AH LiFePo with integrated BMS would be about 5000 USD.

All three solutions provide 320-350 AH of usable power.

Will I get 3-4x the cycles with LiFePo?

Space and weight not really issues as we’ve already got the existing AGMs in there.

Other considerations?

[44'cruisingcat]

Originally Posted by fxykty

Is our NZ price of batteries reasonable? We’ve got an AGM 12V 660 AH house bank that is going to need replacing soon. Usable AHs are 330 and sufficient for our usage.

6 Volt Trojan T-105 225 AH batteries are 282.61 NZD ~200 USD each, so 6 batteries for 12V 675 AH about 1200 USD.

12 Volt AGMs 100 AH are ~ 250 USD each, so 7 batteries for 700 AHs about 1750 USD. Is the extra cost over the Trojans worth not having to water batteries?

400 AH LiFePo with integrated BMS would be about 5000 USD.

All three solutions provide 320-350 AH of usable power.

Will I get 3-4x the cycles with LiFePo?

Space and weight not really issues as we’ve already got the existing AGMs in there.

Other considerations?

Your price for lithiums seems to be very high. In Australia my lithiums cost 150% of what AGMs would have. So my financial break even time span is 9 years.