LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[ebaugh]

Originally Posted by Talbot

It also shows that the AGM batteries are not the panacea that their advocates claim.

Others on this forum have reported experiencing exactly that! So maybe there is something behind the data.

[goboatingnow]

It also shows that the AGM batteries are not the panacea that their advocates claim.

AGMs are a complete waste of time on a boat over normal flooded LA.

dave

[Maine Sail]

Originally Posted by Talbot

It also shows that the AGM batteries are not the panacea that their advocates claim.

Those of us who work with them on a daily basis have known about this for many years..... They can last but you need to take really good care of them....

[CharlieJ]

Amen, Maine Sail. As always; "The Devil is in the Details...and so is Salvation!"

[T1 Terry]

It would be interesting to find out the brand of flooded cell lead acid that survived 500 discharge cycles to 80% DoD and the price per useable Ah. A life of not much more than 700 cycles with DoD to 50% seems to be the norm. I can't say I've seen any deep cycle lead acid batteries deliver 80% DoD for much more than 100 cycles, but then actually measuring the depth of discharge on a lead acid battery is near impossible in anything outside lab controlled tests, the Peukert’s value needs to added to the equation.
The chart indicates a 0.5C discharge rate was used, what would the battery terminal voltage of a 12v 100Ah lead acid battery under a 50 amp load @ 80% DoD? I'm guessing not a useable 12v.

T1 Terry

[dlentz]

Check out EVTV 's recent videos dated April 5 in the "video Archives" . It describes overcharging cells, but more interesting is his discussion of a Swedish Doctorate paper studying LifePo in a city bus. Basically it shows that when cycled form top to bottom at a cc the cells were delivering 2000 +/- cycles. When cycled in smaller cycles at lower SOC and high C's they were getting 9000 cycles. Plus higher temps (30-45c) produced significantly higher cycles.
Not saying it's true just saying, interesting!

[hellosailor]

Since Balqon's primary business is traction batteries, one might make the rash assumption that their tests are for some type of traction battery use. Golf carts, cargo cube mules, something in between?

Their stock is still in the toilet compared to 2011 (10c on the dollar) but spiking all over like someone is playing penny stock games with them (12c to 20c overnight??). Which may reflect a lack of confidence in their patent problems rather than in their product line.

[nimblemotors]

Originally Posted by dlentz

Check out EVTV 's recent videos dated April 5 in the "video Archives" . It describes overcharging cells, but more interesting is his discussion of a Swedish Doctorate paper studying LifePo in a city bus. Basically it shows that when cycled form top to bottom at a cc the cells were delivering 2000 +/- cycles. When cycled in smaller cycles at lower SOC and high C's they were getting 9000 cycles. Plus higher temps (30-45c) produced significantly higher cycles.
Not saying it's true just saying, interesting!

haven't seen the report or data, but using 1/2 the capacity per cycle vs full capacity per cycle, would it be any surprise if using 1/2 meant you could do twice as many cycles? But this effectively doubles the cost of the batteries because you only use half their capacity.

[dlentz]

Originally Posted by nimblemotors

haven't seen the report or data, but using 1/2 the capacity per cycle vs full capacity per cycle, would it be any surprise if using 1/2 meant you could do twice as many cycles? But this effectively doubles the cost of the batteries because you only use half their capacity.

The video is a bit long, but the point being, most cases aren't going to cycle a battery from 100% to 20% at a CC, but the bus application was a more "realistic" use. And while we're not using these for EV purposes, who here is cycling down to 20% for every cycle in a house bank. I would suspect most cycle their bank down to either low point but most likely a point in time that it's convenient to recharge (ie: motoring, solar available, shore available)
I have a 700 amp bank, I don't plan on going to 20% very often, but I CAN.

[hellosailor]

The video, and the graphic itself, seem to indicate 1500 cycles on the 100-10% charge cycle, versus 9000 cycles on a 50-22% cycle. Back of the envelope, 1500*90%=1350, where 9000*28%=2520, so it is more like you are getting twice more useful capacity, not 4X+, when you "sip" on the batteries and just keep them at mid-depth.

That's more in line with conventional quotes and "light" cycling lead acid, not as amazing as "2000/vs/9000". And of course assuming you have a conventient mains charging source or can break twice as often for recharging.

[dlentz]

Originally Posted by hellosailor

The video, and the graphic itself, seem to indicate 1500 cycles on the 100-10% charge cycle, versus 9000 cycles on a 50-22% cycle. Back of the envelope, 1500*90%=1350, where 9000*28%=2520, so it is more like you are getting twice more useful capacity, not 4X+, when you "sip" on the batteries and just keep them at mid-depth.

That's more in line with conventional quotes and "light" cycling lead acid, not as amazing as "2000/vs/9000". And of course assuming you have a conventient mains charging source or can break twice as often for recharging.

Your right only 1500 cycles to 10% DOD @ 3.76C! Pretty poor. Let's see that would be discharging my bank at 2632 amps down to 10% DoD, 1500 times to get to 80% of initial capacity. I'm not sure that's much better that a safe and proven LA bank. I wonder if I might do better at my modest .05 C discharges and shallower DoD? Maybe my $1900 investment can be babied to get near a ROI similar to LA.
Your funny.
CHEERs!

[hellosailor]

dl, you misread me. I'm not saying 1500 cycles isn't great, just that the EVTV guys could be seen as suggesting that 1500 "cycles" can be turned into 9000 cycles. In fact they DO suggest exactly that, and that's not accurate. Turning 1500 into 3000 (equivalent watt-hour) cycles is a good trick. But that isn't 9000 cycles.

All the "facts" seem plain, lithium is the best thing since sliced bread.

I wonder how long it took to get sliced bread a majority market share?

[dlentz]

[QUOTE=hellosailor;1232061]dl, you misread me. I'm not saying 1500 cycles isn't great, just that the EVTV guys could be seen as suggesting that 1500 "cycles" can be turned into 9000 cycles. In fact they DO suggest exactly that,

Sorry if I misread your intent. I think you'll find if you watch some of Jack R"s editorial comments on the business side and players in the Li and EV fields, he's very condescending and forthright about it/them. Much like what some are saying here , however, I don't find him prone to hyperbole regarding performance of the chemistry. Sure 9000 cycles are ridiculous, and I don't see him claiming that. Who has a boat that's going to last that long? whose going to live that long? and besides the chemistry will be obsolete in a few years anyway!
I don't think he was suggesting anything other that the cycle life on these "maybe" much higher than indicated by the Standard CC 100% -10% cycle testing. But again I'm not a mind reader so I don't know his intent, I also know he's a loTTTT more knowledgeable than I!
Gotta go play with my Li.

[mcarling]

Originally Posted by dlentz

I don't find him prone to hyperbole regarding performance of the chemistry. Sure 9000 cycles are ridiculous, and I don't see him claiming that. Who has a boat that's going to last that long? whose going to live that long? and besides the chemistry will be obsolete in a few years anyway!

That's a good point. Many LiFePO4 batteries bought today are likely to be replaced because something better is available before they reach the end of their life cycle.

[ebaugh]

Originally Posted by mcarling

That's a good point. Many LiFePO4 batteries bought today are likely to be replaced because something better is available before they reach the end of their life cycle.

Maybe, but LFP was "invented" in 1996 and took till the late 2000's to be commercially available in a format suitable for marine, and only recently dropped enough in price to generate some interest. That's almost 20 years!

We will see newer and better, but I would not count on anytime soon.