battery system legal for international flights

I am researching the practicality of building an e-bike that can be carried on international flights. I have a folding Bike Friday.
As described on other ES posts there are strict rules on what lithium batteries can be carried on flights. As I understand it batteries of under 100 Wh are allowed to be carried in cabin baggage. I am considering ordering a battery that is split into units of less than 100Whrs. These could be disconnected from each other to comply with airline regulations.
Does anyone have experience of whether such an arrangement would be acceptable to airlines?
I note that Nycewheels (http://www.nycewheels.com/electric-brompton-split-battery.html) are offering a similar arrangement to power a Brompton (they use two 160whr units connected in parallel, however this size of battery pack requires pre-flight approval).

My preference would be to use several 48V units that can be connected together in parallel. One important question would be whether this could be done with just one BMS (either in one of the packs, or as a separate unit). The power and balance lines would be plugged into the BMS for use and charging. I understand that there would be a danger of damage to the BMS if the different packs were at different states of charge. If the units were only disconnected for brief travel times would such an arrangement still endanger the BMS?

The danger would be exaggerated if I wanted to use a different number of packs at different times. Hence a smaller pack could be used for short journeys with a lightly laden bike. One solution to this might be to have two sets of connectors wired to each pack. When connecting a new pack then the initial connection could be made through a specially made connector wire that had suitable resistors in each wire, including balance wires. Could this adequately limit the current and voltage if the cells were of different states of charge? Would it protect the BMS? The procedure would be to either leave the cells for a while to ensure equalizing, or to measure the voltage across the resistors. When satisfied then the other connector on the two cells would be connected. The temporary connector with the resistors could then be removed. This could be done again to add a further pack to the main pack with it's BMS.

Such parallel arrangements seem to be quite common with Lipo systems. However perhaps this is only where the system is run without a BMS. Cell-man's concern was the risk of damage to the BMS.

I would also consider having the first pack made from higher 'C' rating cells so that it could be run on it's own, and then the additional packs made with higher capacity cells for endurance with heavy loads. With the proposed precautions could such an arrangement be practical?

Glad of any assistance: a confessed noob and dreamer.

I've had a similar (domestic USA) interest in this for a while. It's one of things where the goal posts constantly move around. I would love to regularly carry 4qty 5Ah (75Wh) 4S, hardcase bricks in my carry-on bag. Check my Swift folder and simply ride to/from the airport for my regular transcon flights. I'd have the range with 4qty 75Wh bricks.

It seems like RC enthusiasts, camera pros and divers have probably dealt with this in the past and searching through their forums reveals some interesting anecdotal evidence of it being "possible". The recent growth in "drones" is just another potential ally in this sort of thing? I also wouldn't be surprised if many mainline pilots enjoy the hobby of RC flying so they shouldn't be totally ignorant about RC battery packs?

It's all theory at this point but sub-100Wh packs broken down to simple leads, insulated connectors and secured in a sturdy camera type bag/case might be allowed? Of course, we never know with such things until we try and with long haul air travel, that can be a potentially expensive lesson if you're denied boarding?

anyone tried?

the only way you can steer around the regulations is to totally discharge the battery so there is no charge left in the pack. then prove to the regulator there is no charge left so that it falls under the maximum charge allowed.

If you had a CPAP you might be able to press the medical device angle.

Lithium is awesome, but you're at the mercy of minimum wage inspectors in each country who may not even understand what Lithium is. NiCad or NiMh batteries wouldn't give you the same trouble. Sure they're old tech, but they are reliable and Airline safe.

I can find nothing regarding SOC per regulation:

http://www.tsa.gov/traveler-information/safe-travel-batteries-and-devices

In fact, it sounds as if it's probably very doable on Domestic flights/carriers.

Ykick said:

I can find nothing regarding SOC per regulation:

http://www.tsa.gov/traveler-information/safe-travel-batteries-and-devices

In fact, it sounds as if it's probably very doable on Domestic flights/carriers.

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TSA seems cool with them, but the FAA isn't.
FAA-PDF-File-long-ass-link-made-shorter

Thanks for that DS. Turnigy 5Ah 4S hardcase calculate 74Wh per the label so they would actually fall under the "multiples" allowed "consumer" lithium batteries.

cwah said:

anyone tried?

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Yes. I have taken nearly two dozen international flights with <100 Wh lithium battery packs in the past 4 years, in Europe, Asia, and North America. At this stage most airport security/checkout people are well versed in the requirements and know exactly what to look for when it comes to battery specs. Always take the battery(s) out of your bag and present them on their own like you do with a laptop, and make sure that the battery label shows the volts and amp-hours, and preferably watt-hours too. Generally they'll pick it up, look at the label and let it through. If asked what they are for I almost always say backup batteries for my bicycle headlight, which is 100% correct since I do run the bike light from the main ebike pack. I'm worried that if I say the word ebike, they may have been told that ebike batteries are an example of a typical battery that can't be allowed onboard for having too much capacity.

They don't give a hard limit on the quantity of packs you can have, but I would say 3 batteries is the safe upper count. Once you have 4 or 5 packs with you, then that causes some extra scrutiny, and I had an inspection guard in Munich need to call over her supervisor to see if it was really allowed to have that many batteries in the bag.

The only time I have had batteries confiscated was in China, with a pair of fairly old 18V 5Ah turnigy lipos. When I tried to protest that the packs were <100 Wh, the lady effectively said "yeah no I know, but there's no way I will let this puffy old battery on the plane". Then I thought to myself, she's totally right, WTF am I doing bringing a non-bms protected non enclosed hobbycrap lipo battery on a flight in the first place? I get nervous just having one in my backpack now, let alone on the carry-on baggage of an international flight where one incident of a ~100Wh pack battery fire would likely mean the end of any stand-alone packs on board. So after that I only ever did 18650 assemblies with BMS.

And as with anything at the airport, always be prepared to forfeit your goods at the whim of security checkout without protest. If you're not prepared to have your batteries confiscated, then don't attempt to fly with them. I always took the attitude that my batteries would be confiscated, and then everytime they made it through checkout, I'd let out a big "phew".

Might be handy to have a buddy or wife along. You carry on a few, they carry on a few more. 400wh is enough to have some fun.

I'm so close to giving this a shot for my frequent Tcons... 4-5 miles to my home from SAN.

Next hurdle would be how to haul the large 31-33" suitcase needed to check my Swift folder? I suppose nearly empty it could be towed? Probably need good quality skate wheels though...

Thanks to all for comments. It seems such an arrangement could be acceptable to airlines.

Technical questions:
???? Is it considered safe to carry battery units which do not have their own BMS? (but always connected to a BMS for charging or use) I plan to use 18650 units (thanks justin_le)

???? In the posting I proposed a 4*parallel system. This allows for carrying different capacity batteries for different journeys. I proposed a method for safely reconnecting the units to one central BMS. Is this safe for the BMS? Any advice on this method of safely reconnecting?

justin_le said:

Yes. I have taken nearly two dozen international flights with <100 Wh lithium battery packs in the past 4 years, in Europe, Asia, and North America. ... I would say 3 batteries is the safe upper count.

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How have you set up your system? Do you separate the packs into series packs? or parallel packs? Do you have a separate BMS with each?

Ykick said:

I'm so close to giving this a shot for my frequent Tcons... 4-5 miles to my home from SAN.

Next hurdle would be how to haul the large 31-33" suitcase needed to check my Swift folder? I suppose nearly empty it could be towed? Probably need good quality skate wheels though...

Click to expand...

@Ykick You might want to check out the Bike Friday trailer arrangement. (http://www.store.bikefriday.com/product_info.php?products_id=972) It is not as light weight as it could be but seems to have a good track record.

I would be interested to hear how you move forward and what battery setup you choose.

Drunkskunk said:

TSA seems cool with them, but the FAA isn't.
FAA-PDF-File-long-ass-link-made-shorter

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DK, you say that FAA is not cool with such batteries. I looked at the FAA page you linked to. I have specifically designed the battery pack in OP to meet the requirements described in such an FAA document. The battery is separated into units that are less than the 100Wh maximum. The idea is that these packs should be allowed, according to these rules, in the carry on baggage. Am I reading this right? What specifically do you feel the FAA would not be cool about in this design?

African cargo biker said:

justin_le said:

Yes. I have taken nearly two dozen international flights with <100 Wh lithium battery packs in the past 4 years, in Europe, Asia, and North America. ... I would say 3 batteries is the safe upper count.

Click to expand...

How have you set up your system? Do you separate the packs into series packs? or parallel packs? Do you have a separate BMS with each?

Click to expand...

When I traveled with LiPo packs they were two 18V 5Ah units which I series connected to 36V for my application. These didn't have any BMS or rigid casing, so I was careful to tape over the balancing header and the power connectors and wrap them in foam to reduce the chance of shorts if they were mechanically crushed in the overhead bins. They started puffing a bit over time as those hobby lipo batteries are prone to do, and hence got confiscated.

The more recent flights I've done were with 36V 2.5Ah batteries (10s x 1p of 18650's), each of which had its own BMS circuit and so was intrinsically protected against shorts in the wiring. These were then parallel connected to make a 36V 7.5Ah battery on arrival, and I had way less jitters about having them on the plane.

African cargo biker said:

Technical questions:
???? Is it considered safe to carry battery units which do not have their own BMS? (but always connected to a BMS for charging or use)

Click to expand...

The airline people don't know anything about BMS circuits or whether a pack should have them or not. I wouldn't consider a non-BMS protected lithium battery as "safe", but you won't have any issues about there not being a BMS when it comes to the airline checkout, unless you accidentally short the leads around the security gate .

In the posting I proposed a 4*parallel system. This allows for carrying different capacity batteries for different journeys. I proposed a method for safely reconnecting the units to one central BMS. Is this safe for the BMS? Any advice on this method of safely reconnecting?

Click to expand...

It can work, you'd just need to have a header board that parallel connects all the individual cell tap points from each of the 4 batteries. Straightforwards to do on a PCB, and doable but tedious to make as a multi-connector wiring harness.