Best battery for full-time boondocking: LiFePO4

[blars]

After a year of using them, I continue to be impressed with how good LiFePO4 batteries are for boondocking. My latest blog posting is at http://techno-viking.com/posts/lifepo4-best/ and my resources page for them is at http://techno-viking.com/posts/lifepo4-resources/ . I'll be at the RTR, and will be glad to discuss them if anyone is interested.

 

[jimindenver]

Very cool but Wow, those things cost the bucks.

I'm not sure my banks will last another season, I've been fairly hard on them with all of the testing I've put them thru. I've been looking at the newer battery tech, there is a Edison battery factory here but I can't afford them either. Someday.....

 

[sushidog]

While LiFePO4 batteries may be state of the art now, there's a new battery technology that will be out soon - graphene. http://www.graphene-info.com/revolutionary-graphene-polymer-batteries-electric-cars According to this article it appears they will be mass producing these batteries for electric cars in China starting this year. http://www.wantchinatimes.com/news-subclass-cnt.aspx?id=20150104000004&cid=1202

They appear to offer all the benefits of "conventional" (I can't believe I said that) lithium with twice the energy density. Plus they promise to be 77% cheaper, which is the biggest drawback of lithiums to date.

Since I'm planning on building a large (2000w solar/10kw usable battery bank) off-grid boondocking system (with a 12,000 Btu super high-efficiency heat-pump providing sustainable off grid air conditioning and supplemental heating) in a TT in the next 3.5-6.5 yrs. I think I will wait and see what the future holds. Like everyone, I'm on a budget, so the cost of such a system (even over weight, which is also important) is the determining factor as what components I use. Right now, the most economical battery choice for me is a bank of 8 flooded lead acid Rolls/Surrette S-550s. They will give me 214 usable amp hrs @48v if I cycle them 50% (1,400 cycles) with the option of cycling them 70% to get 300 usable ah @48v if needed occasionally (1,000 cycle life) for an identical cost/cycle/amp hour ($0.00868) which is currently about 1/2 the cost of lithiums (though at a huge weight penalty). If I could get a high-tech battery (with all their inherent advantages) at about 1/2 of their current price it would be a game changer. Since I won't be buying these batteries for a while yet, I'll just wait and see, putting off any purchasing decisions for now.

Chip

 

[blars]

When you consider you need half or less the amp-hours of Lead-Acid, they are about twice what flooded lead-acid would cost or near the same as AGM. Considering the life is at 2-4 times (or more) that of lead-acid, are smaller, lighter, and more efficent, they wind up cheaper in the long run.

 

[sushidog]

Blars, here's a comparison chart I did for another website that takes into account their superior life cycle (2000 cycles at 80% discharge vs the S-550s 1,000 life cycles at a 70% discharge.) The only thing that might be off is the current Lithium battery price, as I got this info from an older post off of Technomania's site.

Lithiums (using their numbers) $3,100 140lbs usable ah 400 Cycles 2,000 cost/cycle $1.55 Cost/cycle/amp hour .003875
AGM's (using their numbers) $1,840 535lbs usable ah 400 Cycles 500 cost/cycle $3.68 Cost/cycle/amp hour .00736
GC-2s (priced at my Sams) $704 528lbs usable ah 400 Cycles 500 cost/cycle $1.41 Cost/cycle/amp hour .00282
S-550s (4- priced at Whsle Solar) $1360 492lbs usable ah 428 Cycles 1,400 (at 50% discharge) cost/cycle $0.97 Cost/cycle/amp hour .00227
S-550s (4- priced at Whsle Solar) $1360 492lbs usable ah 599 Cycles 1,000 (at 70% discharge) cost/cycle $1.36 Cost/cycle/amp hour .00227

According to this, Lithiums cost about 171% of S-550s long term. Please correct me if the price of LiFePO4s have dropped in price recently (and the source) and I will update my post on the other site too.

Here's the link showing sources of info: http://www.rvnetwork.com/index.php?showtopic=115068

Chip

 

[ccbreder]

1000 KM per 10 minute charge. It isn't going to happen.

 

[sushidog]

1000 KM per 10 minute charge. It isn't going to happen.

You cant do it with a traditional battery, but you could with a supercapacitor. An engineering challenge for sure; but impossible, no.

The theoretical limit for supercapacitors is an amazing 550 Farads/gm. For comparison, a normal capacitor big enough to store a 150 Farad charge would weigh 600 lbs. Scientists can currently build supercapacitors that can hold this same 150 Farad charge for each gram of weight - the weight of a single paperclip! Superconducting graphene has virtually no internal resistance, so capacitors built with them can store power as fast as you can feed it to them.

"Vehicles that utilize supercapacitors are already prevalent in our society. One Chinese company is currently manufacturing buses that incorporate supercapacitor energy recovery systems, such as those used on Formula 1 cars, to store energy when braking and then converting that energy to power the vehicle until the next stop. Additionally, we will at some point in the next few years begin to see mobile telephones and other mobile electronic devices being powered by supercapacitors as not only can they be charged at a much higher rate than current lithium-ion batteries, but they also have the potential to last for a vastly greater length of time."

Here's a link: http://www.graphenea.com/pages/graphene-supercapacitors#.VKms_uk5CUk

Chip

 

[ccbreder]

And you believe this will be available to the general public, especially small users?

 

[blars]

Balqon prices have gone up a bit since I last looked

Balqon 700 Ah $3,280 188 pounds usable Ah 560 Cycles 2,000 cost/cycle $1.64 cost/cycle/Ah 0.0029286

The LiFePO4 life and amp-hours are at a 1C rate, lead acid at 1/20 C rate. So under house-battery use, you will find that LiFePO4 perform better than quoted, and lead-acid worse.

Is your time checking the flooded lead-acid's worth anything? Do you realy do full cycles? Are you ever charing via generator?

 

[RogueRV2]

"GC-2s (priced at my Sams) $704 528lbs usable ah 400 Cycles 500 cost/cycle $1.41 Cost/cycle/amp hour .00282"

The Costco deep cycle golf cart batteries are said to be good for 700 cycles, so the cost for these might be 29% less, or about .00200, yet in the real world these low cost batteries according to other estimates might only last 2 to 5 years. Same goes for the now popular L-16 Trojans. Trojan estimates 7 to 11 years life span, yet in other of Trojan literature, the average life span is supposedly about 5 to 6 years. Some have report that the Surrette/Rolls batteries last 20 years. Of course this was the quality and design of battery as it was 20 plus years ago. Who knows what is today. There is more to longevity that potential cycles per lifetime.

 

[Almost There]

Balqon prices have gone up a bit since I last looked

Balqon 700 Ah $3,280 188 pounds usable Ah 560 Cycles 2,000 cost/cycle $1.64 cost/cycle/Ah 0.0029286

The LiFePO4 life and amp-hours are at a 1C rate, lead acid at 1/20 C rate. So under house-battery use, you will find that LiFePO4 perform better than quoted, and lead-acid worse.

Is your time checking the flooded lead-acid's worth anything? Do you realy do full cycles? Are you ever charging via generator?

Dumb blonde question - what is the "C" an acronym for. So far I've managed to find (and mostly understand) just about everything else - this one has eluded me so far?

 

[sushidog]

That sounds great, blars. I'm having trouble finding those exact prices. Can you provide a link?
I went to the Balqon website and found a 3v 700ah cell for $840 x 8 (to make 24 volts) = $6,720 for 560 usable ah @24v and 376 lbs. for .006 cost/cycle/ah
The chart that I listed is for a 24v battery bank. Maybe you're thinking my chart represented 12 volts systems.

Actually I will need to build a 48v system to run the heat pump, which is a 48vDC appliance, for which I need 200 usable ah @48v.
If I use 8 flooded lead acid S-550s in series, for $340 ea = $2,720 They are rated at 428ah at 6 volts.
If discharged to 50% for a 1,400 cycle life they will yield 214 usable ah at a cost/cycle/ah of $0.009
If discharged to 70% for a 1,000 cycle life they will yield 300 usable ah at a cost/cycle/ah of $0.009

If instead I chose to use 16, 400ah 3v lithuims from Balqon in series for $490 ea, they will cost $7840
If discharged to 80% for a 2,000 cycle life they will yield 320 usable ah at a cost/cycle/ah of $0.012
If discharged to 70% for a 3,000 cycle life they will yield 280 usable ah at a cost/cycle/ah of $0.009 - the same cost as lead acids

The only problem is they cost over $5,000 more initially though they roughly equal the cost of the best FLAs (less than 1/2 the cost of AGMs) in the long run.
They only weigh 30lbs ea x 16 = 480lbs vs 132lbs ea x 8 = 1056lbs for the S-550s saving 576lbs.
If one considers the time value of money a 20 year payback and I'd have to borrow the $5,000 (and pay interest on this amount) they would cost a little more than FLAs even in the long run. But this money buys 576lbs of additional cargo carrying capacity, a little more available space, zero maintenance (a biggie), and the advantages of low internal resistance (faster charge and discharge without heat or invoking Mr. Peukert.)

BTW, yes I would be recharging occasionally with a EU2000 Honda generator, but would only be charging at a low amp rate (25a or less) which would not make a difference, only if recharging at a high current rate.

Like the saying goes, "All it takes is money."

Chip

---

Dumb blonde question - what is the "C" an acronym for. So far I've managed to find (and mostly understand) just about everything else - this one has eluded me so far?

The only dumb question is the one that's not asked.

I believe c= the batteries capacity, for instance a 100ah lithium rated at 1c means that it could be discharged at the rate of 100 amps for 1 hour. Lead acids cannot sustain such a high rate of discharge because of their high internal resistance. Look up the Peurkert effect.

Chip

 

[AuricTech]

Note that, for renewable energy purposes, most people use the C/20 Amp-hour capacity rating, which is the capacity of a given battery when drawn down over a 20-hour period. At faster rates of discharge, the capacity in Amp-hours is lower. As an example, this AGM battery has a C/20 of 100Ah, a C/10 of 93Ah, a C/5 of 85Ah and a C/1 of only 60Ah.

 

[sushidog]

Most RVers use their battery capacity slowly to make it last for 24hrs, which necessitates a low current draw under the 20 hr rate by definition. With a system like I am proposing with 428 total ah (at 48v), the 20 hr. rate is 21.4 ah. Even my 12,500 BTU air conditioner, the largest continuous power user I will have will only draw 11.5 amps @48v running full blast (good for 480 ah of battery capacity if this is the only thing using power). Of course it would not run wide open all the time as the variable rate compressor will scale from around 12k-7k Btus (11.5 down to under 8 amps.) One could operate an inverter powered microwave for a few minutes (drawing 20-25 amps) but this draw will be for a very short duration. The problem that lead acid battery users face is when trying to run a large inverter off of an undersized battery bank. Then Peukert takes its toll, and lithiums make lot of sense, especially for van dwellers with severe weight and cube limitations.

Chip

 

[SternWake]

I'm pretty much waiting on the sidelines for prices of Lithium to drop. The Initial expenditure is hard for me to confront, though I know thinking in the long term it is much more palatable.

I think it might take implementation of another battery chemistry to make the lithium no longer the latest and greatest before that happens.

For now, I'll maximize the life of my current, and likely future lead acid batteries, as feeble and fickle as they are, and await technological improvements while Studying newer technologies to some degree or another.

It will be interesting to see it all unfold once Elon gets his mega battery factory up and running, and the competition with Toyota and their hydrogen fuel cell route.

I just harvested 9 Lithium 18650 cells from my old laptop battery. Only one cell was questionable, but the battery management system in the pack took out 3 cells entirely and the other 6 were struggling to provide, but these 8 cells give my Nitecore HC50 headlamp hours and hours of strong light.

Way more light duration than the 2 top of the line higher capacity protected Panasonic NCR18650B cells I spent more money on.

 

[cdiggy]

I am waiting for one of these puppies to get invented:

http://www.damninteresting.com/the-mechanical-battery/

Perhaps in another 20 years they will have it perfected! If only we could wait that long...

 

[Toes]

Wouldn't lithium batts still off gas?

One advantage to AGM is that they're sealed and can be used in confined spaces. So wouldn't this still make an AGM the better choice when it comes to living in a vehicle?

 

[RogueRV2]

Getting it done cheap can be fun. Salvaging 18 vdc nicads battery packs is often successful as one can remove up to 4 cells and still have 12vdc battery pack. It can then be charged via a solar system charging system or even off of a fully charged 12vdc battery, albeit slowly.

---

Lithium, AGM or Gel cell will not off gas. If you cant afford the AGM, look at a deep cycle gel cel. If you are in a car, smaller AGM batteries can used instead of a full sized one and placed under the seat.

 

[blars]

LiFePO4 and other lithiums do not offgas unless majorly overcharged. (Then they are dead.) This gas is corrosive and flamable.

 

[IGBT]

I went back and forth on going with lead acid or LiFePO4 in our build and ended up going with Lifeline AGM lead acid.

The Lifeline AGM can handle a faster charge than most other lead acid, actually they highly recommend a large charging current to keep the battery happy (pumping 40 to 50 amps into a 125AH battery during bulk charging). This brings them a bit closer to Lithium in ability to recharge, at least up to 90% or so.

According to the life cycle charts by Lifeline, which have a much longer testing period than any LiFePO4 technology, you can get 1000 cycles at 50% DoD and 500 cycles at 80% DoD.

page 38: http://www.lifelinebatteries.com/manual.pdf


Taking 500 cycles and 80% DoD, you can get 100AH out of a 12V 125AH class 31 Lifeline 68 pound AGM which costs $330 shipped ( I know, I bought four).

So about $1320 for 24V at 250Ah with 200AH useable for 500 cycles or 125AH useable for 1000 cycles.

The problem is a lot of days, you will not be draining them much at all, especially if you have tons of solar like we do. You may wake up in the morning to find they are still at 85%, so 15% DoD. This makes life cycle calculations harder, but essentially it will be greater than the 500 or 1000 depending on how much heavy use you have on the rainy days.

The Lifeline came with a warranty from a USA distributor, that was a bonus. I didn't have to order from China and worry if I got a swollen battery or dead cell. I also do not have to sleep with one eye open during charging...to date no Lifeline has been reported to catch fire or explode during overcharging (shorting a battery can cause fire but that can happen with every battery technology).

I do want to eventually switch to another technology that is lighter. It has to be bulletproof though and preferably available with warranty from several USA distributors at a good value. I was not able to find that with LiFePO4 last year.