LiFePo battery test results

After doing some research, I bought one of the new generation lightweight batteries for my 8A project, knowing that the e-bus performance would probably be poorer than the Odessey PC680 batteries that we currently use. Today I tested the duration of both the Odessey and the new Lithium Iron with a controlled 5.36 amp discharge to compare them side by side. Actually, the Odessey is a 3 year old battery with over 400 flight hours. The LiFePo is a Shorai LFX36A3-BS12, claiming "36 Ah Lead Equivalent". The Odessey is rated at 17 Ah. Here are the results:



The 3 year old Odessey survived 10 mins longer than the new LiFePo with twice the quoted Ah at this discharge rate.

My conclusion: the new gen Lithium batteries are light weight, crank the motor like crazy, but don't have the same capacity at low discharge rates, such as in an e-bus application. Per the graph, the are also less linear in their low current discharge characteristics than their lead acid bretheren, and tend to 'fall off the cliff' pretty quickly when they finally run out of juice.

Still, at 10 lbs weight savings and 90 minutes of e-bus performance, which I deem acceptable, it's going in the 8A.

About the test: to discharge the batteries I used a Optim Engineering CBAIII unit hooked to my laptop. This configuration allow one to precisely select a discharge current and a low voltage cutoff threshold; I chose 11v, which is where Garmin stuff tends to fall off. I charged both batteries fully before running the tests.

Here is a pic of the two batteries, close to the same size, the Shorai is slightlly smaller in height and length, but about 1/2" wider than the Odessey.
The weight difference is substantial: 15 lbs Odessey vs. 5 lbs for the shorai. The photo also shows the Shorai charger, a slick little unit that balances the individual cells as well as charges and stores the battery. My overall impression of the Shorai quality is good: well built, lots of hardware and self adhesive foam pads included. I''ll probably use some of this foam to dampen vibration. Total cost of the battery and charger is under $300 online.

Thanks

Great info. I'm interested in the shorai batteries for main and backups.

Your results correlate well with data I saw from Bob Nuckoll's - they drop off a cliff and don't last quite as long. My answer is that so long as you pick one big enough to last as long as you want, you're OK - so maybe don't go for the smallest that will crank your engine.

It appears that another conclusion one can draw is the LiFePo battery holds a higher voltage for a longer period than the lead acid. I guess a person could calculate the energy differential using the area between the two curves. As a guess, from a total power (watts) perspective, it appears the Li battery wins. But against it's advertised rating of 36ah falls very short.
I wonder how their smaller AH battery would fare

Great data point and proves that one really needs to consider the battery duration at emergency condition loads.

I am thinking the term "lead equivalent" is actually a 10hr rating not 1hr like we would like to see. It is typical when looking at raw LiFePo cells to see 10 hr ratings listed.

Amp hour claims

In defense of the battery manufacturers, these guys are in the business of supporting the powersports industry - motorcycles, 4 wheelers, and the like - who don't give a hoot about e-bus performance, they just want to crank their engines. I suspect that their claims of "lead equivalent" amp hours is probably close to true if you compared them to lead acid under heavy load (engine cranking) and not lower discharge rates. I think these batteries still make sense for us as long as we understand all of the implications. I agree with Ironflight, buy one big enough for your mission if e-bus performance is important to you. The "36 Ah lead equivilent" is the biggest battery that Shorai currently sells.

Thanks for providing some real data. The LiFePO, in this size capacity, just seems to provide a 10 pound weight savings. Actually pretty cheap for that. Compare a composite CS prop to the aluminum. Higher cost per pound.

Also, I am quite surprised that we say the Garmin drops performance at 11 volts. Industrial electronics on heavy mobile machinery is designed for total performance down to 8 volts, sometimes less. I suppose if one wanted to use one of these as a backup power, then a DC-DC converter should be used to maintain buss voltage until the last of the battery is exhausted.

Last thing, repeated deep discharge of PbA batteries will quickly degrade performance, while the LiFePO will continue to function for orders of magnitude more cycles.

Thanks again for taking the time to perform this test and share the data. Too bad the battery companies won't do the same.

Most of my Garmin panel starts dropping out at 10 V, GRT/Dynon after that.

Let us know how it is doing a year from now.

Consider Ballistic...

Thanks for the performance testing information!

If you're going to look at LiFePO4, don't forget about Ballistic. I don't hear them mentioned very often. Good performance, made in the USA, excellent service, 3 yr warranty.

I have been using the 16 cell EVO2 for a little over a year. While I've not done the quantitative testing, I have seen where it will perform well in a deep cycle situation. Had to go 10-12 start tries once and it kept spinning the engine with no perceivable decline in performance.

http://www.ballisticparts.com/products/batteries/batteries.php

Steve, thank you for posting this. Doing this kind of test routinely seems to be a good idea for an all-electric setup. I'm looking at ordering a CBA IV right now.

It will be interesting to compare the discharge rate with a dual Shorai LFX18 setup.

Over time it would be interesting to see what kind of trends there are as the battery ages.

Manual links for Shorai, Ballistic and EarthX at your finger tips

Just thought I would put some links in here so you can easily review what the manufacturer's manuals are putting out there for technical data. We are working with Bob Nuckolls among other professionals to provide the information that is geared toward aircraft as well as power sports so you can make an educated choice in which battery is best for you.

This is for Shorai: http://shoraipower.com/installation-guides

This is for Ballistic's: they don't have a manual that I could find after searching their website, this is the most technical piece of data they have: http://www.ballisticparts.com/tech/charging.php

This is for EarthX: http://earthxmotorsports.com/wp-content/uploads/2014/01/ETX_Manual_111017_G.pdf

We also have on the Experimental aircraft page, a direct comparison of the Odyssey battery and the EarthX battery so you can see for yourself the differences and what would be the best fit for your use. Sometimes we are better, and sometimes we are not, depending on the model and we list them all so you know what you are gaining or losing. Here is that link: http://earthxmotorsports.com/product-category/experimental-aircraft/

And I do realize we are a competitor of Shorai, but I can't help but point out they specifically point out in their warranty that use in aircraft is not covered.
Here's that link: http://shoraipower.com/Customer-Service.html

And this is a total plug for our batteries, I apologize in advance, but we are only patent pending technology battery in this market that has over discharge, over charge and cell balancing built into our battery. You do not need a special charger in order to balance the charge/discharge of the cells and this also ensures that while your charging system is charging the battery, it is doing so evenly. And if you read ALL of our competitor's warranties, if you over discharge or over charge their battery it is not covered. Other than cost, the other down fall of a lithium battery is they are much less tolerant to being over discharged or overcharged than a lead acid and doing it one time, you can kill the battery. This type of protection and safety built into our batteries was not an option in our opinion, but a requirement.

Kathy (EarthX)

That's great info Steve!

I'd love to see other LiFePo batteries tested. Maybe we could convince the other manufactures to send you comparable (36ah) batteries for a good comparison between vendors.

EarthX
Aerolithium
Aerovoltz
Antigravity
Ballistic
etc.

I dont understand the EarthX discharge curves from their manual (see link in their previous post). What are "C rates"? The format of the discharge curve posted by Steve in the first post on this thread is more intuitive and gives me the info I want to know. Would like to see a few more like this at lower and higher amps.

erich

"C" in this case stands for Capacity. For example, if a battery is 10AH then a 1C discharge rate is 10 amps. 1C is always nominally 1 hour to full discharge, 2C a half-hour, and so forth.

- John