SSB Lithium Iron batteries

[Bruce Tuncks]

Model aircraft lithium batteries all have a balance plug as well as the power plug. My latest ( and cheap ) Chinese battery charger will only work if the balance plug is used.

 

I was surprised that the e bike battery does not have this feature. This means that the life and performance of the battery must be compromised. I have no idea what is in the battery-management system of these motorbike batteries, does anybody know if they contain balancing electronics? Franky's experience indicates that they do not, but I reckon you would need to take one apart to see.

 

 

[Franky]

Hi

 

Bruce

 

The ETX680 does have cell balancing circuitry and other stuff, see excerpt from manual below. I think the problem is that there spec for minimum charge voltage is a little low.

 

ETZ - BMS

 

All EarthX integrated BMSs continuously monitor each cell’s voltage as part of the cell balancing and over-charge protection. If the voltage of a cell exceeds the others, the BMS circuits will work to reduce that cell’s charge level. This ensures that the charge level of all the cells remains equal, even with the high discharge (> 100Amps) and charge current (>10Amps) of your vehicle.

 

A cell can be permanently damaged if over-charged (over-voltage) just one time. The BMS has circuitry to disconnect the battery from the charging system (plug-in charger or your vehicle) if the voltage exceeds 15.5 volts (an over-charge condition). The ETX Hundred Series batteries have enhanced over-charge protection; see the ETX - Hundred Series section below for more details.

 

The ETZ BMS has short circuit protection, but it is not resettable or repairable.

 

ETX - BMS

 

The ETX series BMS has all the features of the ETZ series, plus over-discharged protection (completely draining the battery), excessive cranking protection, and short-circuit protection.

 

The BMS disconnects the battery from the load if it is drained to less than 5% remaining charge (an over-discharge condition). An over-discharged battery typically has a voltage less than 11.5V. If the BMS disconnects the battery, the voltage reading of the battery will be zero volts. Excessive cranking protection logic includes temperature monitoring to limit “high current use” (engine cranking) to 10 -30 seconds in any 60 second period. If the battery terminals are “shorted” (or a low impedance load is connected across terminals), which causes the battery volts to instantaneously drop to a very low level, the battery will disconnect from the load to protect the cells and BMS from damage (short circuit protection). If the BMS disconnects due to excessive cranking protection or short circuit protection, the BMS will automatically reconnect after a cooldown period (typically 1-3 minutes). The ETX series is designed for short circuit protection > 1000 Amps.

 

Franky

 

 

[skippydiesel]

Model aircraft lithium batteries all have a balance plug as well as the power plug. My latest ( and cheap ) Chinese battery charger will only work if the balance plug is used.I was surprised that the e bike battery does not have this feature. This means that the life and performance of the battery must be compromised. I have no idea what is in the battery-management system of these motorbike batteries, does anybody know if they contain balancing electronics? Franky's experience indicates that they do not, but I reckon you would need to take one apart to see.

I hesitate to respond, as I am the one looking for information - however it would seem that SSB is claiming a BMS for its Lithium motorcycle batteries very similar/the same as EarthX . For experimental aircraft it would seem that the SSB range offers all that the EarthX has, at a much reduced up front cost.

 

 

[Head in the clouds]

................ However, the electronic battery management system does not tolerate high charging currents...so if you do substantially discharge one, you can damage it by charging with a standard lead acid battery charger/regulator and particularly by 'jumper' connecting it to a charged lead battery or running car's battery. I'm no expert in this, but this is what the battery suppliers say. I think my Lithiumax 400 battery has a maximum charge current of 8A, but it easily delivers 60A plus to crank the Jabbie 2200...real fast. So the one downside of the Lithium batteries are no jump starting.

I guess they probably vary between manufacturers because the information that came with mine is quite different.

 

I have a Shorai Powersports 18AH LiFePO4 battery which weighs just under 1kg with 270CCA (compared with the 8.5kg lead/acid it replaced which had 220CCA). The general advice that came with it is that their Lithium Iron batteries can be charged quite fast from any state (i.e. from either flat, or half, or nearly fully charged) and the maximum rate of charge should not exceed, in Amps, the Amp Hour rating of the battery up to 30A. Batteries with higher than 30AH rating should be charged at maximum 30A.

 

So since mine is 18AH, apparently it is happy to be charged at 18A from any state of charge. I spoke with the distributor about the actual condition in the aircraft, since the output of the 912ULS charge circuit is 20A, and he said to just keep some load on the circuit other than just the battery being charged. Since that's not always easy I have a ceramic wirewound resistor which can be switched in and out of circuit. It can get a bit warm but not enough to cause any damage to anything.

 

I also have electric anti-ice carby heating so that can be switched on at any time too because since it heats the carbies rather than the air, it does not cause an engine power reduction. It has variable temperature settings so it can pull up to 12A at full power.

 

Mine cost $250, BTW, you can see their range and info at the Shorai site. And they send them to you by airmail because they're not considered to be dangerous goods because they CANNOT catch fire. You can send them back for testing cell-balancing etc, also by air satchel and they return them the same way next day (apparently - I've not had to do that).

 

 

[Franky]

It looks like the SSB batteries are all Lithium Ion Phosphate not Lithium Iron Phosphate batteries

 

They are very different beasts.

 

Franky

 

 

[skippydiesel]

It looks like the SSB batteries are all Lithium Ion Phosphate not Lithium Iron Phosphate batteriesThey are very different beasts.

Franky

About 5 responses in, I quoted the following from SSB:

 

"SSB PowerSport Lithium Ion Phosphate Batteries (also known as Lithium Iron Phosphate Batteries) ..................................................................."

 

Make of this what you will but it is clear that SSB believes that in this context Ion & Iron are one in the same

 

 

[horsefeathers]

About 5 responses in, I quoted the following from SSB:"SSB PowerSport Lithium Ion Phosphate Batteries (also known as Lithium Iron Phosphate Batteries) ..................................................................."

 

Make of this what you will but it is clear that SSB believes that in this context Ion & Iron are one in the same

Ion and Iron are (obviously) NOT the same

 

The most common lithium-ion cells have an anode of carbon © and a cathode of lithium cobalt oxide (LiCoO2)

 

The chemistry is different to a Lithium IRON battery (LiFePO4) (Fe=Iron, for all you physicists out there )

 

Don't EVER use a Lithium Ion battery in your aircraft

 

 

[skippydiesel]

Ion and Iron are (obviously) NOT the sameThe most common lithium-ion cells have an anode of carbon © and a cathode of lithium cobalt oxide (LiCoO2)

 

The chemistry is different to a Lithium IRON battery (LiFePO4) (Fe=Iron, for all you physicists out there )

 

Don't EVER use a Lithium Ion battery in your aircraft

I have, this day, writen to SSB technical advisor asking for clarification on this point. I will pass on advice received.

 

 

[Markdun]

I am no battery expert, but ALL lithium batteries have lithium ions and can be referred to as lithium ion batteries. All (or nearly all) lithium batteries on the market have porous carbon anodes. Lithium iron phospate batteries are one type of lithium ion batteries, where the cathode is made of compound containing lithium ions; there are others, eg. Lithium cobalt oxide, lithium titanate etc. My understanding is that the term "lithium ion' is used to distinguish these types of batteries from early lithium batteries that had metallic lithium in the cathode....and these batteries had a particularly high fire risk because during recharging you would get dendrites of metallic lithium growing on the cathode and these dendrites could reach the anode, resulting in a short circuit and thermal runaway leading to a fire. This is not to say other lithium batteries are immune to fire. And of course lead acid batteries can also develop internal shorts from lead dendrites (but no thermal runaway). Have a look at this site for more info Lithium-ion Batteries Information - Battery University

 

I would suggest that SSB are correct in referring to their batteries as both lithium iron phosphate and lithium ion. What would be good is if the battery manufacturers published the detailed specs of the battery management systems so we can compare.

 

Skippy, you may want to check Lithiumax batteries....similar price to SSB, and they are advertised as suitable for aircraft. I have both and I can't really tell any difference but the vibe I get is that the BMS on the Lithiumax could be better...but that is just a guess in the absence of specifications and measurement.

 

 

[skippydiesel]

Great information from Markdun and very similar to the responce I have quoted below from SSB technical:

 

"In short;

 

Lithium Ion is an umbrella term that categorises quite a few types of lithium batteries.

 

Examples of Lithium Ion Chemistries:

 

Lithium Iron Phosphate - LFP

 

Lithium Cobalt Oxide – LCO

 

Lithium Manganese Oxide – LMO

 

Lithium Nickel Manganese Cobalt - NMC

 

Many lithium ion types are not recommended for use in automotive applications because they become unstable when raised to certain temperatures – this is called thermal runaway. Lithium Cobalt Oxide has this issue.

 

So to answer your question – Yes our batteries are Lithium Ion batteries – Specifically they are Lithium Iron Phosphate Batteries (LiFePO4).

 

Our batteries are completely safe and have been used in Motorcycles since 2010."

 

 

[skippydiesel]

On this topic, there is an advisory document on the RAA  web site . Anyone contemplating the fitting of a Lithium iron phosphate battery  should read this.

 

In short;

 

• Jabiru do not recommend this type of battery.
   
   
  
• Rotax are more  circumspect - throwing the responsibility onto the air frame manufacturer.
   
   
  

 

 

 

 

 

 

 

[Old Koreelah]

Very interesting, Skippy. The RAA notice doesn’t specify the type of Li battery and seems to be be saying only knuckleheads will have a problem.

 

 

[skippydiesel]

Very interesting, Skippy. The RAA notice doesn’t specify the type of Li battery and seems to be be saying only knuckleheads will have a problem.

Hi OK,

 

My reading/interpretation is a little different - I suggest RAA are saying  - make sure you exhaustively research the comparability/suitability of this type of battery to your aircraft. In particular the battery charging system.

 

Pilots should also be aware of  the impact on weight & balance, that the fitting of such a light weight battery might have.

 

 

[Bruce Tuncks]

You have to consider the context in which RAAus and Jabiru make these statements. They could well be held legally liable for whatever somebody did even though the details would be way outside their control.

 

The nearest I personally know of a fatality caused by a battery was due to a lead-acid one exiting the aircraft in severe turbulence and just missing the pilot's head as it went past him before going out through the canopy.(We paid better attention to hold-down systems after that.) 

 

The point is that lead-acid is not completely safe either but being the standard battery, it is legally safe, so of course Jabiru and the RAAus would specify it.

 

If I had my way, we would be able to do lots of things at our own risk. And that is just what we have here... if these batteries are warned against but you put one in anyway, then you are doing so at your own risk.  As far as insurance is concerned, I reckon you would need for the insurance company to agree that this battery change would not negate any claim , at least where the event was unrelated to the battery.

 

 

[Markdun]

I think the big practical issue is the charging of the Lithium batteries. If you forget to turn off your master switch and find you've a flat aeroplane battery you can't just 'jump' start from your car as you will exceed the charge rate for the lithium battery (depending on the battery management system in the lithium battery). Or if you hand start, or manage to get a start from a nearly flat lithium battery, the standard Jabiru voltage regulator will also not regulate the charge current and this could see the battery's charge rate exceeded, or the Jabiru's stator destroyed (if you have no fuse in the AC side), or both.  The Jabiru/Kubota voltage regulator might also have a too high upper voltage .... one of mine was at 14.4V which was a bit over the 14.0V recommended for the lithium battery.  I've installed the Powermate regulator -- it regulates the charge current to a max of 8 Amps and my voltage never goes above 13.9V now.

 

The big difference I've found in use is that on a cold morning when you press the 'start' button the starter rotates the engine to the first compression and really struggles to move it through TDC, this occurs on the second compression too, but then the battery seems to finally wake up and gets the message that it is required to deliver lots of Amperes and voila, the engine spins like crazy & starts. And it does deliver lots of Amps....I had to increase my battery fuse from 100A to 125A.

 

 

[Old Koreelah]

I guess you're right Skippy, but all the search in the world is of little value if it goes over your head.

 

I'm intelligent enough to have achieved a lot of things, but electrics have always caused my brain to fade.

 

I designed and installed all my wiring and it works and I did lots of research before fitting my LiFePO4 battery. Apparently their cells can only take up to 3.2v.

 

I spent months trying to find a regulator that would keep the Jab engine's charge below 12.8v -to no avail.

 

I then stumbled on a business selling LiFePO4 batteries to rally car people (he had not thought of other markets such as aviation). He supplied a battery that is said to cope with a 16v charge, so I suspect it has 5 cells.

 

I presume this means my Jab alternator can't ever fully charge it. What do you think?

 

 

[Old Koreelah]

 ...As far as insurance is concerned, I reckon you would need for the insurance company to agree that this battery change would not negate any claim , at least where the event was unrelated to the battery.

Good luck with that, Bruce!

 

 

 

[Old Koreelah]

...(if you have no fuse in the AC side)...

Can you show us how to install one?

 

 

[Old Koreelah]

...Pilots should also be aware of  the impact on weight & balance, that the fitting of such a light weight battery might have.

Excellent point, Skippy. My new battery cost $400 to buy, but nearly 400 hours to install. It saved 2.8kg, which was a welcome  reduction in MTOW, but I couldn't mount it any further forward to maintain balance. Even after remounting toolkit, spare etc. just behind the firewall, I had to move the wing back 18mm. 

 

 

 

[Markdun]

I just splice in an automotive blade fuse holder on one of the two wires that go from the engine's alternator to the voltage regulator, and put in a 15A fuse. These fuses are designed for vibration. I don't use the glass tube type fuses in an aircraft as the unsupported fuse wire inside the glass tube can fatigue break from vibration. The Powermate website probably has a diagram of the details.

 

 

[Markdun]

I assume you have installed a sliding track from a front car seat for your wing attachment so you can easily adjust your CoG. I wish I thought of that when i installed a lighter Jab engine to replace a VW, requiring moving the engine forward 50mm, new engine cowls, and then 1kg of lead in the tail because 50mm forward was too much!

 

 

[Bruce Tuncks]

My system is to suit a cheapskate. A $100 Hobbyking 8.4 A-h LiFe battery with a $10 digital voltmeter on the panel. The engine is started and as soon as the voltage reaches 14.2, the master is switched off so no overcharging can take place. ( capacitors act as the "battery " for the radio etc )

 

I don't really recommend this setup for others. If you forget to turn off the master you can overcharge the battery, and some people get alarmed at the non-standard idea.

 

But it has gone well for years now, and the old Odyssey ( $260) battery is going fine in the farm buggy.

 

 

[Kyle Communications]

One of my mates is developing a new reg for Rotax engines to take any battery including the lithiums. He is a genius at this stuff. It will have max charging rate and also a voltage cutout . It will never allow the horrible spikes that come from the Rotax generator to ever reach the battery. He has a prototype running now and it is looking spectacular so far. We may end up producing them. They will be able to be used for any engine but it is specifically designed to take into account the Rotax charging issues

 

 

[skippydiesel]

I..................................................................................................................

The big difference I've found in use is that on a cold morning when you press the 'start' button the starter rotates the engine to the first compression and really struggles to move it through TDC, this occurs on the second compression too, but then the battery seems to finally wake up and gets the message that it is required to deliver lots of Amperes and voila, the engine spins like crazy & starts. And it does deliver lots of Amps....I had to increase my battery fuse from 100A to 125A.

Its "news to me" that Lithium batteries need to have a "wake up" period.

 

If true  for all/most it concerns me  - with my minuscule understanding of electrical /automotive starting systems it seems to me that with a low current delivery,  you will be heating up your circuitry (especially starter motor wiring). This will inevitably shorten the life of your starter motor, if a Rotax, the sprag clutch and in the worse case scenerio, start a fire.

 

Current draw should be the same, whatever battery you install, ergo fuse size should not need to be increased - this is a symptom of an over loaded starting system, not a more powerful battery.

 

Most pilots will be looking for an instant, high energy, turn over & start. Lazy cranking must be addressed ASAP

 

 

[skippydiesel]

One of my mates is developing a new reg for Rotax engines to take any battery including the lithiums. He is a genius at this stuff. It will have max charging rate and also a voltage cutout . It will never allow the horrible spikes that come from the Rotax generator to ever reach the battery. He has a prototype running now and it is looking spectacular so far. We may end up producing them. They will be able to be used for any engine but it is specifically designed to take into account the Rotax charging issues

 

Great news Kyle - hope you keep us all informed of this development.