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CAUTION! LiFePO4 Battery Capacity!
I've had a couple of different topics recently on the Aerovoltz/Ballistic LiFePO4 batteries and also on alternator wiring connectors overheating. I just got some information from EarthX that is very interesting.
What I've found out is this: While the 12-cell Aerovoltz/Ballistic (same battery - different brand names) is easily capable of starting my Jabiru 3300, it only has a capacity of maybe 3 amps. Therefore, the battery gets pulled down quickly by the starter, and the Jabiru does not produce charging current until it hits 1900 rpm. That means all the electrical systems during taxi, run-up, etc. are running on battery only. (The Jab has dual magnetos so it doesn't depend on the battery once started.) During take-off and revving the engine beyond 1900 rpm, there is a sudden in-rush of alternator current to replenish the battery. Lithium batteries naturally have low internal resistance and allow the in-rush of current. I've been told the "20 amp" alternator might actually be putting out as much as 32 amps!
Technical support at EarthX said my 12-cell Ballistic was seriously under-sized in terms of capacity. He said my previous Odyssey PC680 had about 12.8 amps capacity. An EarthX ETX36D has 12 amps of capacity and was what he recommended. It's roughly the same size as the PC680, so it'll fit my battery box, and only weighs 3.5 lbs - 1 lb more than the 12-cell Ballistic. He assured me this would work well in my application and eliminate the in-rush of current from the alternator.
An added plus is that the EarthX has an on-board battery management system to balance charge the cells, prevent over and under charge, and protect the battery from excessive charging current.
So ... lesson learned - consider the capacity of the battery when choosing one for your application!
BTW, EarthX has great customer service and technical support - they quickly got me information I needed!
(Looks like the Ballistic moves to my '84 Honda Nighthawk!)
John
N750A
Replies to This Discussion
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Permalink Reply by Louis W. Ott on
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In talking to EarthX myself about the difference between C, D, and E, that's it. Size. internals are the same.
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Permalink Reply by John Austin on
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By offering multiple case sizes of the same battery, EarthX is trying to address one of the most-frequent complaints about LiFePO4 batteries ... that they are too small! Apparently, it takes a lot of spacers or padding, etc., to keep some of the batteries securely mounted since they are much smaller than the original battery that fit in the battery holder/compartment. Probably the biggest problem is with motorcycles since it's not unusual to have a battery compartment deep within the frame and very limited-length battery cables - the smaller lithium battery has to be elevated with a spacer to reach the cables..
As I previously pointed-out, the ETX36D is pretty close to the size of a PC680. I did have to elevate the new battery just a bit with some of the provided self-adhesive foam pads so the bottom would clear the up-turned lip of my battery support shelf on the firewall - it was a bit too-deep to fit between the lip and the firewall..
John
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Permalink Reply by Randy Boykin on
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The reason ask is I have the Aerovolt batteries in my plane, I switched to them because of weight savings, but I have found they are so sensitive to draw down to low voltage and when recharging my electrical management system says over voltage and shuts the alternator off, so I am looking for alternative batteries but my battery compartments are sized for the Aerovolt batteries and I was hoping to not have to resize them. Thanks for all the help and input.
Randy
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Permalink Reply by Mark Maltais on
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One of the reasons I avoided the Aerovoltz... :( The EarthX batteries have a built in balance charger AND a built in low voltage protection. If the cells get too low then the battery won't allow any more discharge to occur. The small extra price for them evened out when adding those features up... that and the fact, like John's issue, that they can take a massive initial charge.
I also just bought the smallest battery physical size I could find, which was the "C" version I believe and built a battery box out of scrap aluminum. Took maybe an hour... I made it a hair bigger so I could use the foam inserts as a cushion in the box. I'm sure there is an Earth X battery size that would fit the Aerovoltz size.
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Permalink Reply by Paul Saccani on
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Beware of the usage of "AH Pbeq", meaning Ampere Hours lead equivalent. What that means is that the AH is about a third of the stated AH. This reflects the lower internal resistance of the battery, which allows it to crank to quite a low state of charge. But if you are relying on the battery to power other loads (particularly if you have an engine dependant on an electrical supply, as many auto conversions are), you are going to need a bigger battery.
Cheers,
Paul
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The ETX36D is working well, however, my 20 amp alternator output breaker still occasionally trips. My theory is that even though the ETX36D has 4 times the capacity than the Ballistic/Aerovoltz did, by virtue of it's lithium chemistry, it still has very little internal resistance so it readily "accepts" whatever charge the alternator can muster! I've been told the Jab 3300 alternator can produce up to 32 amps or so current, and the ETX36D can take charging current up to 60 amps.
I initially installed a 20 amp alternator breaker because the Jab's alternator was rated at ... you guessed it! - 20 amps! However, that's faulty logic - the breaker is there primarily to protect the wiring! Since my output wire from the voltage regulator to the Composite Design Mini Power Panel is 12 ga, according to Composite Design's spec sheet that's good for about 41 amps peak and can be protected by a 35 amp breaker. So, I just installed a 35 amp breaker - hopefully that'll be the end of my chasing electrons for a while!
John
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Curious now to fire mine and see the charging rates. I have the "EXPBus2" as a main switch bus and it recommends a single 40 amp breaker from the alternator line prior to feeding the bus. I'm guessing it shouldn't trip at that size. My main cables are all 6 gauge. I have a 40 amp InterAv alternator on my Lycosaur...
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I've got several flights on the 35A breaker and it hasn't tripped a single time - I think you'll be fine with the 40A breaker!
John
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Permalink Reply by Ken Ryan on
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EarthX says that the Ballistic has a capacity of 3 amps. I can only assume that this is meant to be 3 amp hours (at what discharge rate?). EarthX also says that their battery has a capacity of 12 amp (amp hours?) which is FOUR TIMES what they say the Ballistic has.
Given that the batteries are the same chemistry, it makes sense that there is a direct comparison between battery weight and battery capacity. Unless EarthX has some sort of magic dust they sprinkle on their batteries, their 12 amp (hour) lithium iron battery should weigh approximately 400% what the 3 amp (hour) lithium iron battery weighs. But in fact it weighs only 40% more, not 400% more.
Something here does not pass the sniff test.
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Ken,
The comparisons are "Usable amp hours at a 10-hr rate."
I by no means am an expert on lithium battery technology, but as I understand it, while all LiFePO4 cells certainly have the same chemistry, not all are of equal quality and I don't think the capacity is strictly related to cell weight/mass. As I understand it, the cell's crystalline architecture (surface structure and nanoparticle morphology) is the "magic dust." Crudely restated, finer particles perform better!
I've submitted your question to EarthX because it's a good one! If they respond (with all the proprietary technology out there who knows?), I'll certainly relay the answer. However, it's not all smoke and mirrors - the EarthX ETX36D completely resolved the problems I was having with the 12-cell Aerovoltz/Ballistic - and you are correct that it only weighs about 40% more.
John
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John,
Thanks for the clarification that the comparison is amp hours at 10 hour discharge rate. Something to keep in mind is that the 1 hour rate (which is probably closer to what one would experience with alternator failure) could be significantly less than the 10 hour rate. Thanks also for forwarding my question to EarthX. It will be interesting to hear their response. I am not an expert either, but I do have some experience with batteries and have learned that capacity correlates closely with weight for the obvious reasons. The huge difference claimed by EarthX defies all my previous experience with batteries.
You say that the EarthX resolved the problems you were having with the 12-cell Aerovoltz/Ballistic. Am I correct that the only problem was the overheating of the alternator wires where they terminate (at the alternator)? In reading your other thread it sounds like this is not an uncommon problem and has been blamed on inferior connectors and not necessarily the lithium battery. Can you say for certain that this problem was caused by the battery and not the inferior connectors? Is it possible that the connectors had been deteriorating all along and that failure was coincidental with the battery swap? Or that the connectors had been deteriorating all along and that the additional draw from the lithium battery was the straw that broke the camel's back? Is it not possible that the same thing would have happened with an EarthX battery?
Aside from the giant (and suspicious) discrepancy of weight-to-capacity ratios, another thing that has me puzzled is why 32 amps (the limit of the Jab alternator) would be a problem. If the alternator is capable of putting out 32 amps I would think the wiring and connectors would be sized to handle it. Are the wires and connectors properly sized for 30 amps? I'm just having a hard time putting these puzzle pieces together and reaching the same conclusions, i.e that the smaller capacity battery (combined with the lower internal resistance of lithium batteries) caused such an inrush of current as to melt properly sized connectors. Again, it seems if the alternator can put out 32 amps, the wiring should be sized for that.
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Ken, this is going to be a lonnnngggg reply! Bear with me!
First, the "easy reply." (I think!) EarthX responded right away and here's the entire response:
Hi John,
I am very happy to hear you are a satisfied customer! And I do know that you were “responsible” for additional purchases of our batteries based on your forum postings so I thank you in return!
This is a great question and I do actually have a great answer. J But I am not sure where someone thinks it is 4X the capacity….it is not quite double.
The weight of an Ballistic/Aerovoltz 12 cells battery is listed as 2.5 pounds and has a true tested capacity of around 7.8ah.
The ETX36D weighs in at 3.6 pounds and a true capacity of 12ah.
The actual battery we would consider comparable to the 12 cell would be our ETX24 battery that weighs 2.4 pounds and has 8ah of capacity.
The chemistry is the same, lithium iron phosphate, but the construction of the cells is very different. The Ballistic/Aerovoltz battery used K2 cylindrical cells that are each wrapped individually in an aluminum casing which is much heavier than a prismatic cell in a foil casing. Secondly, the Ballistic/Aerovoltz needs metal tabs to connect each of the cylindrical cells together whereas you do not need this in a prismatic cell. Again, this adds more weight. Thirdly, the casing. As the weight of the battery is very important, we spent a lot of R & D to develop the casing to be as strong as if needs to be, and no more as this only adds weight. When you compare apples to apples, we are only .1 pound lighter and only have .2ah more capacity plus a BMS.
Hope that answers your question.
Sincerely,
Kathy Nicoson
EarthX Lithium Batteries
Global Sales Director
(970) 301-6064
Fax: (970) 674-9544
Facebook https://www.facebook.com/earthxbatteries
Website: www. Earthxmotorsports.com
Email: sales@earthxmotorsports.com
OK, the "3 hour capacity" of the Aerovoltz/Ballistic and the EarthX ETX36D having "4 times" the capacity was information that EarthX sent to me! So, obviously, I'm now getting different information and that would square more closely with your thoughts, Ken. Nonetheless, the increased capacity works for my situation!
Now, the alternator/connector/battery mystery theory is as follows.
- Regardless of anything else, the OEM Jabiru 3300 female alternator connectors were too light for the intended application (per Pete Krotje, Jabiru USA) and needed to be replaced with heavier, quality connectors (I used AMP and they are working well).
- When I switched from the Odyssey PC680 to the Aerovoltz/Ballistic 12-cell, the lack of capacity started inducing surges of charging current, frying the OEM alternator connectors.
- Not having figured-out #2 yet, repairing and replacing the connectors was akin to removing a resistor from the charging circuit. So then, the 20 amp alternator breaker began popping.
- At that point, I went to the larger capacity (at this point, who knows how much? HA!) EarthX
ETX36D. It mostly, but not totally, reduced the instance of the 20A breaker popping. - Even with the larger capacity, I learned/realized that since it was still a lithium battery, it has low internal resistance and that contributes to the charging surges.
- Reviewing my bus wiring and realizing that I could safely go to a 35A breaker for 12ga wiring (per Composite Design Mini Power Panel installation instructions), I installed a 35A breaker and now there are absolutely no breaker trips at all now. (And the ETX36D is good for up to 60A charging current, so no worries there!)
So that's my story and I'm sticking to it! ;>)
John
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