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

Freep wrote:
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 could be wrong here, but my recollection is that the LFP will cause most alternators to overheat trying to keep up with the electrical load of the LFP because it will take as much current as you can give it. This could also result in a fire with overheated wire from the alternator to the battery.

Edit: I forgot to add the risk to the battery in the above scenarios. Who knows what kind of horrible electrical surges you might get from a failing alternator, plus a fire risks everything.

I believe it depends on the specific situation. Long thin wire will be self regulating. Some alternator systems are better than others.

I suggest installing the half depleted LFP and give it a go. Get your clamp-on ammeter out and see what the actual situation is. The alternator will survive just fine for a couple minutes. Then add equipment only as needed.

Testing an alternator vs LFP on a bench is very different than in an RV. Unless of course you have a converted bench as an RV ;)

“ 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...

How would a coulomb counter risk the battery?

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 could be wrong here, but my recollection is that the LFP will cause most alternators to overheat trying to keep up with the electrical load of the LFP because it will take as much current as you can give it. This could also result in a fire with overheated wire from the alternator to the battery.

Edit: I forgot to add the risk to the battery in the above scenarios. Who knows what kind of horrible electrical surges you might get from a failing alternator, plus a fire risks everything.

Well you can smile if it suites you (I’m all in for smiling :) !! ) , but it’s not clear to me how I’m risking either my alternator or battery??... maybe your suggesting that one cannot get by without a dc to dc converter, (I donno?)...I must be missing your construct...My point on meters was for awareness to the broader audience that not all SOC meters are LFP compatible - this is why I had to replace my former Xantrex LinkLite SOC meter...

3 tons

3 tons wrote:
“ You definitely need a DC-DC charger for charging from your alternator.”

Not necessarily...With 440w of solar and a single 200a/h LFP, I neutered the 7pin plug charging wire as being unnecessary - Harvest swiftly handles everything...And even with the alternator, so long as the amps are kept at a reasonable level for continuous charging (depending on battery C rate and alternator output), of say 25-30% you should not have an issue...

BTW, Victron smart shunts may be a bit pricier (than the China stuff), but so then is your LFP Battery investment, right??

3 tons

I got rid of the 7 pin a long time ago so I could charge the battery and run the fridge while driving. I'm running 6 gauge from the alternator to the camper. This was pre LFP.


You're making me smile here. On one hand you're fine with risking your battery and alternator(to save money?) but then raise the spectre of damaging your expensive battery by using a cheaper coulomb counter.

To each his own, man. But a cheap coulomb counter is fine with me because it's an inherently unnecessary device. It's just a convenience. If Victron had their smart shunt at half the price I probably would have bought it, but $200 for a fancy coulomb counter is just not a value to me. I'm glad it is for you. If I had unlimited funds I'd be all Victron all the time -- except for the battery. It's too much fun rolling my own.

“ You definitely need a DC-DC charger for charging from your alternator.”

Not necessarily...With 440w of solar and a single 200a/h LFP, I neutered the 7pin plug charging wire as being unnecessary - Harvest swiftly handles everything...And even with the alternator, so long as the amps are kept at a reasonable level for continuous charging (depending on battery C rate and alternator output), of say 25-30% you should not have an issue...

BTW, Victron smart shunts may be a bit pricier (than the China stuff), but so then is your LFP Battery investment, right??

3 tons

Gjac wrote:

I'm not sure what you mean by high quality deep cycle batteries, but I paid $74 apiece for my 2 GC batterers from Sam's Club 14 years ago and they are still doing fine and I only dry camp. If they failed tomorrow I can still buy them for $90 apiece, so I don't see a cost comparison that is close yet. I understand the weight is a lot less as well as the foot print and in time with all the EV's coming out they may be cheaper.

If you're comparing batteries by the number of batteries and price, then you probably have the batteries that are best suited to you.

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

So $600 CAD is about $580 US if I converted right. I realize everyone has different electrical requirements but 2 Sam's Club 6vGC batteries are still under $200 in us dollars so I don't see a similar cost. I'm not sure what you mean by high quality deep cycle batteries, but I paid $74 apiece for my 2 GC batterers from Sam's Club 14 years ago and they are still doing fine and I only dry camp. If they failed tomorrow I can still buy them for $90 apiece, so I don't see a cost comparison that is close yet. I understand the weight is a lot less as well as the foot print and in time with all the EV's coming out they may be cheaper.

Stay in the safe ranges, rinse and repeat, enjoy the camping.

time2roll wrote:
There is no RV converter that is a best charger for LFP that I am aware of.
I am not even convinced many of the lithium chargers are really that good including that NOCO.

I don't know but when you have two Lifepo4 battery makers recommend chargers for there Lifepo4 batteries,one would think they do just fine..Battelborn say's the Victron IP65 smart charger is there go to charger and it is just the same as the NOCO that Expert power recommends although expert power has there own Lifepo4 chargers..

Maybe some are over thinking charging...I do know there are so many opinions on lithium batteries out there,it's hard to pick out what's right and what's wrong when they differ from manufacturers suggestions..