What is best battery power pack?

[John61CT]

I have come across a lot of misinformation at the batteryuniversity site.

There doesn't seem to be much "in dispute" other than between those willing to go without a "system" approach packaged with a proprietary BMS - and the huge cost involved - and those willing to tinker DIY, which many don't want to bother with.

If you're not wealthy nor a risk-taking tinkerer, then stick to lead.

 

[Scott7022]

It all has to be a system wide approach. It doesn't matter if you are Trojan, Lifeline, or uncle Dim Sum two.  AGM, Gel, Lithium (in the forty different configs), or over venting Hidernberg specials. It all has to be a system approach. Charge profiles, from alternator, from generator, from solar, via duck poo osmosis. No point in upgrading your alternators if your float charge is X and you 1000 dollar units are putting out Y.. The problem is understating what the system is. 500 amp at idle super SUPERMAN branded krypton alternators and four gauge cable for 15 feet is going to keep you warm. For 20 minutes or until the bucket boys arrive and put out your rig. But this is not really what the OP was asking she wanted people to just tell me what will do X. I don't want to be concerned with x variables. This is really an honest question and indicative of 80% of the people out there. They don't get it and they don't want to get it. They want an Apple computer, works out of the box. I respect and applaud it. They want the experts to give them the answer. Problem is most of the so called experts don't know shit. They go on about voltage drops and other half cocked notions. Please show me the temperature drop in a water filled hula hoop sitting on an ice rink. Blah blah blah.
I have researched this for hours and hours, over the course of 8 years,  and I was going carbon foam two months ago and changed back to lithium for a ton of reasons. All of which globally eclipse the OP's question. Start a lithium thread and I will share and post. But, I fear, it will go the direction here as it does on sailing and overland and big cruiser forums, boils down to pedantic differences between people who can't afford to do it, arguing if/what they c/would do it if they won the lottery. With experts chirping in from armchairs. I am sorry and I apologize if this seems a little curt. No disrespect is intended or directed to anyone. This is a forum about cheap RV living and I love it as such and it is why I read it as such. You want info on Lithium, Bruce Schwab is the guy,  google him and lithium. Keep in mind his watch is worth more than most of our rigs. That is not my world and I don't wish it was my world. But because of what I am doing I need power, so I am taking a system wide approach to achieve that goal as cheap as I possibly can... Like I said, if people are really interested in lithium and someone  starts a thread I'll post into it. Yes you can run a 15000 BTU 110vac  A/C  off Lithium in Quartzite, no issue. Yes you can pull down to 80% and still recover your investment.

 

[John61CT]

Yes, in the context of

https://vanlivingforum.com/showthread.php?pid=315225#pid315225

I concede paying the $1,000+ for the 80AH Yeti is good value, for him.

And getting into the weeds on LFP is not what this thread is for, sorry for contributing to the derail.

 

[frater secessus]

all depends on where YOU set the shoulders.

My understanding of the term shoulders is areas on the voltage curves where the voltage rapidly rises or drops off.  Are you referring to setpoints here?

 

[frater secessus]

Sources I have read claim longest life for the smallest discharge cycles. "[font=Arial, Helvetica, sans-serif]Cycling in mid-state-of-charge would have best longevity."[/font]
http://www.batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Thank you for pointing out my error.

My "longest life" word choice was poor.  I was referring to using practically all the LFE's capacity, as one does when going to 50% DoD on lead-acid.  Meant it in contrast to a poster referring to 100% DoD on LFE.

 

[IGBT]

Essentially I think you are supposed to use about 50% max of a lead acid and about 80% max of a lithium

So 100AH of lithium does not equal 200AH of lead acid but more like 160AH.

Taking a quality lead acid like a Lifeline down to 50% regularly will yield you about 1000 cycles or last about 6 years

Taking a lithium (maybe LFP) down to 10% and recharging to 90% will yield you at least 2000 cycles or last about 10 years

That last part is important for some people.   Age is going to eventually attack both batteries capacities.   If you use 20 cycles per year on the lithium, you are only going to get about 200 cycles out of it before the capacity has dropped to around 80% of what it was new.

 

[frater secessus]

But, I fear, it will go the direction here as it does on sailing and overland and big cruiser forums, boils down to pedantic differences between people who can't afford to do it, arguing if/what they c/would do it if they won the lottery. With experts chirping in from armchairs.

There are people on the forum already running LFE house banks with no drama.  Blars comes to mind.

Currently (ha!) I have 2 x 6v in the van and I will use those until they croak.  When that happens I'll install ~200AH of LFE for "fractional C" use according to wisdom gleaned from the sailing forum and elsewhere. 
No lottery winnings or histrionics required.

 

[John61CT]

My understanding of the term shoulders is areas on the voltage curves where the voltage rapidly rises or drops off.  Are you referring to setpoints here?

No. These are continuously sloped curves, grey areas, not right-angled discontinuities.

Some above talk about stopping charging at 90% and stopping discharging at 10%.

They have chosen those restrictions somewhat arbitrarily, IMO a bit too conservative.

But that is up to the owner, assuming the protective gear allows custom programming.

At which I suppose they do become setpoints.

My understanding is that defining Full as "charging at 3.45Vpc until current drops to .01C" is usually within a few percentage points of the rated capacity, going any higher is then "pushing the shoulder" at the expense of longevity.

Stopping a low-amp discharge when the bank voltage drops below 12V is likely also well below the 10% theoretical level? Of that I'm less sure.

But the overall effective capacity is IMO closer to 90% of rated capacity rather than 80%.

And calendar life in storage only, no cycling, seems to already have proven closer to twenty than ten, and I think will end up being maybe double that, but we just don't know.

People selling "new stored only" banks aren't discounting much for unused years.

Stored properly means cool, dry and at very low SoC.

 

[IGBT]

Well actually lead acid if stored property (drain the acid and put it in a sealed container) probably outlast stored lithium batteries.  I imagine you could store one for 50 to 100 years.

 

[frater secessus]

These are continuously sloped curves, grey areas, not right-angled discontinuities.

We agree on that. I maintain an attentive owner can look at the curves and discern shoulders for themselves:

from this page.  

Children with crayons could probably mark the rise at fully charged.   There would be less kindergarten consensus at the other end but they'd probably be in the same ballpark.  If I was still substitute teaching I'd run the experiment and bribe them with graham crackers!

I agree that using 90% of capacity is fine, going between 3.45v/cell and disconnecting at something like 3.00v/cell.  As with the crayon crew the hard choices come at the end.  In practical terms I doubt I'd see the bottom end of a 200AH LFP bank very often.

 

[John61CT]

Relevant recent thread with actual curve posted by Maine Sail (CMS on that site)
http://www.trawlerforum.com/forums/showthread.php?p=577554

 

[frater secessus]

The curves agree. We agree. The literature agrees with MS's observation that the voltage curve is flatter with more pronounced shoulders when discharging at Fractional C rates. Multi-C discharge curves are more linear with less defined shoulders.

[Edited: MS' curve is C/13 and plots closely to the chart I posted]


We agree so much that, as douglas adams said, "I could not possibly fail to disagree with you less".

 

[RVTravel]

Another electrical thread that was supposed to be about smallish portable battery packs, goal zero/anker/suaoki/jackery.

 

[frater secessus]

It was, and the OP bought an Anker in the first couple of days.

 

[John61CT]

Decent AH capacity and portability pretty much demands LFP.

People looking for making a DIY luggable powerpak should check out eBay seller:ru2014_bere

 

[user 37446]

It would be nice hear from the OP how her Anker powerpack that she received and charged is doing for her needs.  That was post #25 on page 3, everything else has been a lithium charging/discharging discussion which is probably Mandarin Chinese to her...

[font=Verdana, Arial, sans-serif]"My Anker Powerpack just got here and is charging up. I can't wait to use it. I love the size too. It is super small."[/font]

 

[RVTravel]

The recharge time may be the limiting factor. I'd love the feedback too.

 

[ZacLee]

The 24V Telecel brand LiFePo4 batteries I use have this cycle life rating

80% depth-of-discharge, 2000 cycles
70% depth-of-discharge, 3000 cycles
25% depth-of-discharge, 8000 cycles

The Telecel batteries include battery management electronics so can be used more-or-less as drop in replacements for lead acid batteries. They are intended for telecom use and sometimes can be found surplus at reasonable prices on ebay. I paid $200/kwh including shipping for my set from ebay. These were new, but had been stored for a year or 2. That ebay seller also had alphagen 48VDC generators which are based on the honda eu3000. They were offering those generators, brand new, for $350 each, but wanted $250 for shipping.

 

[ZacLee]

Looking at the total amp-hour yield over the cycle life of the battery provides some insight. The 24V Telecel brand LiFePo4 batteries I use have this cycle life rating. For simplicity, the calculations for ah over lifetime below are for a 1 amp-hour rated battery. These calculations assume the capacity remains constant over the life of the battery though it would be slowly declining over that time. End of life is defined by most manufacturers as the point when the battery loses half of its rated capacity. If I get a chance, I redo the calculation on a spreadsheet to account for the diminishing capacity.

80% depth-of-discharge, 2000 cycles (1600 ah over lifetime)
70% depth-of-discharge, 3000 cycles (2100 ah over lifetime)
25% depth-of-discharge, 8000 cycles (2000 ah over lifetime)

There is minimal (5%) difference in ah yield over the lifetime of the battery for 25-75% depth-of-discharge, but the yield drops by 25% when the depth-of-discharge is extended to 80% and likely drops even further with deeper discharge. It would be interesting to see cycle life data from other LiFePo4 batteries for comparison. In a nutshell, this data indicates discharge depth between 25% and 75% yield roughly the same cycle life while extended discharge depth to 80% reduces life by 25%.

PDF Datasheet for the Telecel batteries:

https://www.google.com/url?sa=t&rct...t%20Spec.pdf&usg=AOvVaw2oh_OgVsddBlXgg8bcumIy

 

[John61CT]

> End of life is defined by most manufacturers as the point when the battery loses half of its rated capacity

Maybe you're talking LFP only, or some specific market segment?

In the lead world, 80% capacity is the industry definition of scrap.

Some owners of course push until "unexpected failure", but those wanting predictability, or with mission critical use cases, should not go much below 70-75% SoH.

But treated as I've outlined, LFP capacity simply isn't declining much at all, I know early adopters after 5-7 years are still getting 90-95% out of their standardized 20-hour load tests.

Of course quality vendors tend to deliver new cells at 105-110% to start with, but the decline is very slow in normal House bank usage as kong as charging voltages have been kept below 14V.

In much harsher EV usage, they often fail long before even the rated 1500-2000 cycles, sometimes under three years.