LiFePo4 vs Lead Acid...Some points of interest.

larry cad wrote:

StirCrazy wrote:

Gjac wrote:
Jayco creek said: With the price getting so low for Lifepo4,I can't see a reason not to switch when there about the price of a quality lead acid...JMHO,.. So what is the current price comparison?

for making your own you can build a 280 usable AH for about 600 bucks now. to get that in deep cycles batteries you probably over 1000 for high quality and about the same in cheep on sale (these prices are CDN).

other advantages besides price now days is weight that would be about 46LB and it would give me more capacity than the 240lbs of 6V I have now that only have 235AH usable. also the size, this one Li battery is the side of one of the 6V batteries. so 1/6th the weight and 1/4 the size.


Steve

Do the LiPo4 batteries require a special charger? If so, you should include the price of that item also.

its kind of a mute point. unless you custom order your camper the charge in 90% of the campers shouldn't be used anyways. they are starting to get better but they will still kill your battery faster than a good one. the first thing I do is put in a proper 4 stage charger in anything I buy. so with a LiFePo4 I will just put in a proper 2 stage instead, or if you have one that is already Li compatable (which I have seen a few factory ones) your already good, just have to flip the button.

Steve

So 3 tons, who told you that the Xantrex LinkLite SOC meter wasn't accurate and the Victron is? From everything I can see, all three products do the same thing with regard to determining state of charge.

What am I missing?

Edit:
Do you think it would be more accurate if it counted Ahrs?

“ This confirms what I thought. Since the Victron Smart Shunt and the AiLi meter are both counting coulombs they should be equivalent as far as reporting of SOC is concerned. You're just getting bluetooth connectivity and some other bells and whistles with the Victron Smart Shunt.”

For LFP, Coulomb counting is just one of several parameters used - coulomb counting alone is insufficient at accurately determining LFP SOC, particularly below 50%...I know nothing about the AiLi, but this issue is why the Victron should not be compared to a simple coulomb counter...

3 tons

BTW, Heres another engineering analysis regarding calculating LFP SOC - this was provided earlier by PianoTuna and well worth one’s time:

https://youtu.be/1SeH0f8nigc

3 tons

I'm particularly fond of the amp hour counter,easy to double check and keep track of the amp hours used...It isn't always spot on to the percentage used but close...Between the amp hours and voltage it makes it interesting how the Victron smart shunt comes up with the percentage.

Freep, this for an engineering point of view:

https://www.youtube.com/watch?v=rOwcxFErcvQ

3 tons

3 tons,

This is the response I got:

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First, counting coulombs is counting coulombs, and what the source/destination is makes no difference.
Secondly, "computing SOC with LFP..." this sounds like its based on voltage instead of coulomb counting... the non-counting meters have only the current voltage to look up (estimate) the SoC. And this of course differs based on type of battery chemistry.

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This confirms what I thought. Since the Victron Smart Shunt and the AiLi meter are both counting coulombs they should be equivalent as far as reporting of SOC is concerned. You're just getting bluetooth connectivity and some other bells and whistles with the Victron Smart Shunt.

3 tons wrote:

I agree that it needs to be considered, but so long as the alternator capacity pencils out it to say 30% for continuous down the road charging it can be doable - just another data point in the vagaries of one’s considerations - in my anecdotal scenario I see no necessity to bother with the alternator because harvest has proven sufficient and swift - this, yet a third option worth one’s consideration...

I hear you. I've got 600 watts of solar and I'm seriously considering getting rid of my generator. I could just use the engine for a quick charge if I needed it. I never run the gen for more than an hour these days anyway and even that is rare. Why drag a generator around?

3 tons wrote:
“ But a cheap coulomb counter is fine with me because it's an inherently unnecessary device.”

Ok, but for clarity it should be noted here that a meter that only counts coulombs is not structly compatible with LFP, though it may be fine above 50% SOC - in practical terms with LFP, SOC only begins to get important below 50%...

As has been already noted here several times, computing SOC with LFP requires a sophisticated algorithm including a ‘look-up’ ledger which is necessary when below a 50% SOC...This is due to the extremely flat voltage curve characteristics of LFP, and why (as previously stated) I had to ditch my former meter...

This is interesting. There are a lot of people using the AiLi for their LFPs over at diysolarforum.com and I've never heard this before. I'll go ask the gurus over there and see if I can get some clarity. I've been using it for almost a year now and it has usually agreed with the BMS on SOC.

Edit: To be clear, a Coulomb counter does not rely on voltage.

“ I'm not saying your specific installation is risking your battery. I'm saying, from what I've learned from others, that you can't just drop in an a DIY LFP battery and expect it to charge from your alternator without making some changes.”

I agree that it needs to be considered, but so long as the alternator capacity pencils out it to say 30% for continuous down the road charging it can be doable - just another data point in the vagaries of one’s considerations - in my anecdotal scenario I see no necessity to bother with the alternator because harvest has proven sufficient and swift - this, yet a third option worth one’s consideration...

BTW, the most amps I’ve ever seen my 200a/hr drop-in draw was 70a (on shore power with a 100a charger) but typically closer to 55-60a...It routinely charges quite easily with 440w of solar...

3 tons