LiFePO4 Install

[DaveInDenver]

I don't think LFP is really all that bad for handling care, not really much worse than AGM for trying to keep alive for long term. AGM has a fairly tight window, not too little to avoid sulfating, not too harsh as to cause them to vent.

Plain old flooded batteries are cheap, tolerate a lot of abuse and are pretty easy to repair if you do damage them. So it'll be a while before they get supplanted on a cost analysis. If they just didn't weigh so much and had to be kept upright.

 

[dreadlocks]

yeah its hard to beat flooded batteries for cost vs performance..

but, at this point w/lead batteries if I had a failure.. all I would get is pro-rated for another one (more likely multiples since it would be a 4x battery bank) and would still be out of pocket unlike getting this fixed for no expense other than a bit of time.

For lead batteries to give me the performance I need out of this rig, my weight would not be 40lbs but like 250lbs+.. since this is a toy hauler and just inherently tongue heavy, that was not really a good option and would had required at least more tow vehicle.. which makes the premium cost for this moot.. Lots of overloaded overlanders here spending a ton of money to loose weight, same old story eh?

 

[DaveInDenver]

The weight reduction is very real, no doubt, so the individual situation drives how valuable that is. I don't see a potential weight saving like you get when I do my estimations but I do see around 50% when I look at reworking things. Maybe a bit more if I really sharpen the pencil on being able to push out to 80%, 85% discharge to use of the capacity from LFP compared to the AGM I have now. But the 2x cost resets daydreaming and I stand pat for now.

 

[luthj]

For off grid applications where every watt hour counts, the lithium packs have a significant advantaged. No long absorb where harvested energy drops. 5-20% higher coulombic efficiency. Minimal peukert effect.

 

[john61ct]

6X is overblown

My calc, usually comes out just under half the weight and space

 

[67cj5]

It really is a tough choice, Li and LC will take a high fast charge rate and FLA and AGM are slow, Li are light as, LC, FLA and LC are all heavy weights, FLA and AGM are easy to charge from solar, Li and LC need about 800w or more to put the power back or some type of DC to DC Charger to provide a 30% charge rate or more.

Putting the higher cost aside, FLA and AGM can be found in any Auto Store world wide which makes them the safer choice for those who want peace of mind,, I like what Lead Crystal can achieve and they cost about half way between a Deep Cycle Battery and Lithium battery, So there are three price ranges to choose from So there is something for everybody.

 

[dreadlocks]

right now I'm doing ~65-70ah dusk til dawn, and able to recharge it daily with minimal fuel/sunlight.. thats not including any of my day time loads I run off the big solar.. I'm able to get by with 100AH just fine with LFP, but Ive had ~250AH of AGM then GC batteries in my Westfallia, with a couple 100W portable panels and had to keep my diet ~25-35AH over night to keep things good for the long haul and still took more effort when solar didnt cooperate and stuff.

I dont think I'd of been satisfied w/anything less than ~400AH and my 650W of solar panels if I'd of stuck w/heavy ass lead honestly.. not being able to fully recharge without 8 solid hours of sunshine or driving has been a huge pain in my ass over the last few decades of trying to survive off lead tech.. I was just looking at some NP Campgrounds, only 2h of genset usage a day limit.. I'd be fine w/that even with no solar, if I had FLA.. ouch, thats not enough to do much of a charge.

Intermittent big loads throw off the calculation, if I use 10AH of power running my microwave @ 950W in LFP, how much AH did I just suck out of FLA? much more than 10AH until you get up to a rather sizable bank.

 

[67cj5]

right now I'm doing ~65-70ah dusk til dawn, and able to recharge it daily with minimal fuel/sunlight.. thats not including any of my day time loads I run off the big solar.. I'm able to get by with 100AH just fine with LFP, but Ive had ~250AH of AGM then GC batteries in my Westfallia, with a couple 100W portable panels and had to keep my diet ~25-35AH over night to keep things good for the long haul and still took more effort when solar didnt cooperate and stuff.

I dont think I'd of been satisfied w/anything less than ~400AH and my 650W of solar panels if I'd of stuck w/heavy ass lead honestly.. not being able to fully recharge without 8 solid hours of sunshine or driving has been a huge pain in my ass over the last few decades of trying to survive off lead tech.. I was just looking at some NP Campgrounds, only 2h of genset usage a day limit.. I'd be fine w/that even with no solar, if I had FLA.. ouch, thats not enough to do much of a charge.

Intermittent big loads throw off the calculation, if I use 10AH of power running my microwave @ 950W in LFP, how much AH did I just suck out of FLA? much more than 10AH until you get up to a rather sizable bank.

Do you seriously have 650w of panels ??

Your microwave might be rated at 950w but if you are only using it for 5 minutes you are only using about 79.16w from the inverter ? does that sound about right ??

 

[luthj]

Watts are not watt-hours.... In the same way that miles are not miles per hour.

 

[dreadlocks]

yes I have a 325W fixed roof panel and a 325W "portable" panel that I've yet to mount vertically to the side of the trailer for when the fixed panel isint cutting it.. both combined can fully recharge me in ~2h, which is pretty easy to get in all but the most dense forest.. and then in overcast/shady conditions they both combined output more than I need for base loads..

its designed to go indefinitely in the worst case scenario, and when sun is abundant I just burn energy like its nothing at all.. I tried to build a couple previous systems for average and best case, I was not happy with results during extended boondocking trips..

950W is what my microwave inputs, its rated for like 700W output, its just a lil dorm microwave..

 

[dreadlocks]

some simple calculus here, lets throw Solar out the window because its got such an advantage on LFP its not even funny.. lets pretend we're using an Engine as our primary charge source, either Generator use or Driving.

~70AH day diet, I run Engine ~2h day to recharge, burning gas.. 100AH of LFP @ ~40lbs is fine and can daily cycle like this for eons practically.

FLA battery takes ~8h to do a proper absorb and get em up to full.. thats 4 days FLA needs to go to require same amount of engine time.. thats 280AH, and now double it for the FLA penalty of 50% DOD.. that means I need 560AH to make it the same equivalent engine time.. but instead of a bunch of short charges, like 100 miles down the coast or a few hours of generator use when not at camp every day, your looking at 500 miles of driving or a full day of generator usage every 4 days.. Two GC2 Batteries are ~125-150lbs, times that by three is like ~375-450lbs to get me >600AH.

with solar the advantage LFP has being so efficient at charge/discharge, and being capable of taking whatever the sun is willing to give it, at 20% or 90%, allow you to hookup far more solar then would ever be reasonable on FLA.. 650W of Solar w/my 100AH LFP is a comfortable ~0.4C charge rate at ideal conditions, which its happy to take.. if I pull 10-20Ah out of the bank in the middle of the day w/good sun, its replaced PDQ like I never even used it.

Amp Hour to Amp Hour is not the only way to measure LFP with FLA, IMO its a rather bad way to compare them honestly and makes FLA look better than it really is.

 

[67cj5]

My 115Ah deep cycle batteries weight 23.7kg / 52.24 Lbs each but I don't see that as too much of a problem,

 

[dreadlocks]

A Duracell 215AH 6v GC2 battery is 68lbs, with FLA.. more weight the more lead, and the more lead the more robust capacity you have at your disposal, I can use that 52lbs vs 68lbs to argue how much more a GC2 is a deep cycle than whatever your 12v "deep cycle" claims.

so 136lbs for 215AH, plus a few more pounds in heavy gauge cabling connecting em together... tho only $200 vs $1k if all you care about is usable AH and ignore everything else LFP brings to the table.

 

[67cj5]

A Duracell 215AH 6v GC2 battery is 68lbs, with FLA.. more weight the more robust, I can use that 52lbs vs 68lbs to argue how much more a GC2 is a deep cycle than whatever your 12v "deep cycle" claims.

so 136lbs for 215AH, plus a few more pounds in heavy gauge cabling connecting em together... tho only $200 vs $1k if all you care about is usable AH and ignore everything else LFP brings to the table.

Yeah well I do link 2 of them together which gives me 230Ah but to be on the safe side only 115Ah of usable power at around 105 Lbs, Never had the need to hook up the 3rd one to the pair, I did think of buying 2 or 4 X 230Ah but they weigh too much for one person to move around.

 

[LivinDaDream]

~70AH day diet, I run Engine ~2h day to recharge, burning gas.. 100AH of LFP @ ~40lbs is fine and can daily cycle like this for eons practically.

FLA battery takes ~8h to do a proper absorb and get em up to full.. thats 4 days FLA needs to go to require same amount of engine time.. thats 280AH, and now double it for the FLA penalty of 50% DOD.. that means I need 560AH to make it the same equivalent engine time.. but instead of a bunch of short charges, like 100 miles down the coast or a few hours of generator use when not at camp every day, your looking at 500 miles of driving or a full day of generator usage every 4 days.. Two GC2 Batteries are ~125-150lbs, times that by three is like ~375-450lbs to get me >600AH.

with solar the advantage LFP has being so efficient at charge/discharge, and being capable of taking whatever the sun is willing to give it, at 20% or 90%, allow you to hookup far more solar then would ever be reasonable on FLA.. 650W of Solar w/my 100AH LFP is a comfortable ~0.4C charge rate at ideal conditions, which its happy to take.. if I pull 10-20Ah out of the bank in the middle of the day w/good sun, its replaced PDQ like I never even used it.

You've nailed it...as I touch on in the thread I posted a couple days ago, the biggest advantage for my situation, is the potential to charge LFP safely, in a hurry, without substantial long term degradation. Someone show me their 80-100AH (useable) FLA system that they can put 50-75AH into in 3- hours of good sunlight during a day, often by noon if I've got all 4 of my 100W panels active.

Yes, it's a bigger initial expense, but I have no doubt that for me, it will be a one-time expense that greatly simplified my power management scheme and in the long run, may end up costing less. And even if it did end up costing more, my time and aggravation is certainly worth something...it's not a system that needs to be pampered or monitored to the nth degree, especially since I've got a fair amount of overhead for my normal usage. I looked hard at staying with FLA, but in the end it just didn't make sense.

Cheers!