LFP on Shore Power with Inverter/charger?

[BFL13]

An inverter/charger requires that you have a battery connected (or some 12v source) so it will supply any 12v to the RV. (Unlike a converter that will do 12v with no battery)

Some say not to float an LFP. If you choose not to float yours, what do you do when on shore power? You can't isolate the battery and run 12v off the charger in the inverter/charger since it would be dead.

You could just not enable the charger, and run 120v off shore power pass through---or can you? Does 120v pass-through happen with no 12v to the inverter/charger?--- And just cycle the LFP for your 12v, thus not floating it.

What do folks do in that situation?

[BFL13]

If I am right that CCA is "power" , then an experienced RVer is looking for a deep cycle battery with LESS power. He stays away from those starting batteries, and sure would not want one with "Twice the Power".

[StirCrazy]

BFL13 wrote:

time2roll wrote:
LFP does have twice the "power" (energy?) as you don't have to stop at 50% like FLA.

That AGM Odyssey says it has "twice the power" and it would have that 50% idea, for any deep cycling it could do?

I have the notion from what I have been told here (but could have got it wrong!) that "power" would be like CCA for a battery, so one with 800 CCA would have twice the power of one with 400 CCA. I think "energy" says how long it can keep doing that cranking.

So I don't know why an RVer would be interested in a battery's power at all. How many AHs it can do, yes. And how many times it can be deep-cycled.

could be because when you buy a RV you get a cheep hybred 80AH battery in it that normaly wont even have 40AH usable as it is a starting battery with thicker plates. so a proper deep cycle could in theory have twice the available "Power" and then if you go LiFePo4 because your not hurting the battery using the full capacity you will have twice the available power again. its all what there comparing to and what words they leve out or add. not lying but letting you form your own conclusions while guiding you in the direction they want. in some paces people get confused by it..

Steve

[BFL13]

time2roll wrote:
LFP does have twice the "power" (energy?) as you don't have to stop at 50% like FLA.

That AGM Odyssey says it has "twice the power" and it would have that 50% idea, for any deep cycling it could do?

I have the notion from what I have been told here (but could have got it wrong!) that "power" would be like CCA for a battery, so one with 800 CCA would have twice the power of one with 400 CCA. I think "energy" says how long it can keep doing that cranking.

So I don't know why an RVer would be interested in a battery's power at all. How many AHs it can do, yes. And how many times it can be deep-cycled.

[time2roll]

LFP does have twice the "power" (energy?) as you don't have to stop at 50% like FLA.

[BFL13]

I think the very high discharge just for a few minutes is for UPS work to hold the fort until the emergency generator spools up.

"Twice the power" can be explained with watts and all that mumbo-jumbo, but when you see that and decide " I gotta have one of those, it has twice the power!"

What do you as an RVer, expect that 100AH battery will do that the 100AH battery you have now won't do? Run everything twice as long? Run the jacks up and down twice as fast? What does "twice the power" make it able to do for you?

So, IMO, since I have no real clue, "power" is a word that sounds great, but what I see is a 100AH battery and another 100AH battery. With FLAs, I know one night be marine/rv and the other true deep cycle and what to expect there.

[time2roll]

Take advertisements with a grain of salt. Maybe a full scoop.
Advertising is written by marketing people, not the engineering team.

[StirCrazy]

BFL13 wrote:
I have seen that where they say it maintains the same "capacity" But it still runs for less time the higher the draw.

They say 1C for an hour is the same "capacity" as 0.05C for 20 hrs like using RC instead of AH.

Peukert has it running for less time the higher the draw too, with fewer AH at the higher draws

Then they start using "twice the power" or more energy density. Makes me feel I am being flim-flammed.

However, after some digging, it turns out they just mean it can do the high draw for longer than Brand X, not that it does not take less time than a lower draw would.

Can't help it--as soon as I see "power" and "energy" in the advertisement I get all paranoid they are messing with my mind. Just give me my Trimetric monitor and AHs and let me go camping and everything will come out right 🙂

except the internet is full of people who have doen 1C tests on LiFePo4 and ran at full 1C for 58 min. doesnt seam like much of a Peukert effect. well I guess it was two min less time, but thats when the BMS shut off so it might have gone the full 60 min , or maybe they were just good cells with 5 or so extra AH... so at least for prismatic cells the 1C rate is actualy 1C. I dont know what 10C would result in but I cant imagin it would be far off, but another useless number unless your driving a tesla 😉

Steve

[BFL13]

Yes, although I also want to do more ordinary RV min with the batts , not just the high draw trick. I got the idea that Odyssey was mor like a starting battery vs a deep cycle so it would do the high draws better but maybe not the regular RV duty as well . Could be wrong, don't know.

I can't find my notes doing high draws with the ordinary AGM a few years ago. The SiO2 has a higher set of voltages than the ordinary AGM, which means it goes lower before hitting the inverter alarm. So the time an AGM can run the MW is less than the time an SiO2 can do it just from that.

Then there is any difference in energy (if any) or however you express that, where it can do it for longer on top of that voltage advantage. LFPs have even higher voltages than the SiO2.

Whatever---all the RVer wants to know is if he can do whatever he does now better by swapping battery types. No use if the new battery will do tricks he will never do.

[FWC]

If you don't understand energy, 50% more usable Ah would suffice.

You are right that the capacity is the same at the 20hr rate. But my understanding was that your requirement was to support high inverter load for longer before your inverter shut down. In which case a dual purpose AGM would be both cheaper and be able to support your high current loads for longer run times before the inverter alarms.

As shown above, a lithium would have performed much better than either lead acid batteries.

[Itinerant1]

FWC wrote:
And just to head of the next question, here is similar data for 120Ah CALB prismatic cells - these (or similar) are what most folks are using for their DIY lithium packs:

Almost looks like someone just drew with colored markers. 😉

Here are GBS 100ah cells charge/ discharge curves.




You look at enough of the lfp charge/ discharge graphs they all look very similar.

[BFL13]

I have seen that where they say it maintains the same "capacity" But it still runs for less time the higher the draw.

They say 1C for an hour is the same "capacity" as 0.05C for 20 hrs like using RC instead of AH.

Peukert has it running for less time the higher the draw too, with fewer AH at the higher draws

Then they start using "twice the power" or more energy density. Makes me feel I am being flim-flammed.

However, after some digging, it turns out they just mean it can do the high draw for longer than Brand X, not that it does not take less time than a lower draw would.

Can't help it--as soon as I see "power" and "energy" in the advertisement I get all paranoid they are messing with my mind. Just give me my Trimetric monitor and AHs and let me go camping and everything will come out right 🙂

[3_tons]

Per FWC: “IIn terms of SLA, a dual purpose AGM should also preform better than SiO2 as the Peukert is also closer to 1.0. I gave you the table for Odyssey before and it was 50% higher usable energy.”

Interesting, as the evidence mounts it suggest that in practical user terms, SiO2’s main fortay is mostly limited to below freezing weather, the sound basis of a speciality niche battery - at this juncture, pretty much hard to refute...JMO

3 tons

[FWC]

Any BMS that uses contactors as opposed to MOSFETs, or assuming you are running an inverter (at 10C), use the BMS to shutdown the inverter as opposed to shutting down the battery.

However, I seriously doubt anyone will be running at 10C, this was to illustrate that lithium retains its capacity at high discharge rates. As BFLs example illustrates, even at a 1C rate lead acid is only good for about 1/3 its rated capacity.

[pianotuna]

Which BMS allows for a 10 C discharge rate? Or do you just run without one?

[FWC]

And just to head of the next question, here is similar data for 120Ah CALB prismatic cells - these (or similar) are what most folks are using for their DIY lithium packs: