Hard-case LiPos are safer. Right?

[LongRat]

This is my only pack with an injection moulded plastic case. In a hard forward shunt the wires have been pressed into the casing, with hard sharp edges, causing the insulation to be split in both the positive and negative wires. Now they are separated by millimetres with no insulation. I will call this a (very) near miss.



Lithium batteries in cars do not fail by structural rupture or penetration. I have yet to witness any failure that has not been caused electrically. In which case, containing the cells actually presents more hazard. In the instance above, the hard case is actually the cause of the failure.

[neiloliver]

Yep, you were lucky you did not get a short.

The failure of a laminated Lithium ion cell can occur in various ways (internal fault, overcharging, over discharging, poor assembly, external damage, over current, over temperature etc). Casing the cells in a hard plastic is one of the best ways of protecting the soft pouch assembly that is easily damaged by mechanical abuse. Out of the hundreds of battery designs I have been involved in the number of uncased laminated Lithium ion designs is.. zero.. because it is mostly only the hobby market that use them in user replaceable applications.. this is because, in general it is a bad idea to allow uncased cells to be put in the hands of the general public... but we all know we use them in aircraft due to the lighter weight. In cars it is vital that we maintain the hard case.

In this case photographed it is a poor design of the wire exit that is to blame, you cannot say that hard casing is a bad idea. The designer of the casing should have highlighted this as a weakness in the design and addressed the weakness by creating insulation between the wires or providing some strain relief.

I feel your financial pain - There is really not a lot you can do about it apart from insulate the wires as best you can, discharge the pack and then take it to your local recycle centre. Do not attempt to post/ship it to anyone as it is damaged and doing so would contravene a number of international shipping regulations.

[blue_pinky]

Def a poorly designed lipo case.

I've never been a fan of lipo's with cables coming out of them like that myself, and that is something that is generally typical of the cheaper brands.

As for lipos failing due to puncturing/mechanical failure...I've seen a hard case lipo fail catastrophically as a result of a drive pin coming out of a centre shaft/CVD in a 4wd...and rupturing the cells...

Equally I've seen a few saved by the hard case when the same thing has happened as well...proving that the hard case is a very sensible feature of lipo batteries! I would always prefer hard cased ones personally...although in micro, I do use soft cased ones as there are no hard case ones available for the car/chassis I have.

Annoyingly for you, I suspect here is no easy fix for that pack...unless you can pursuade some heatshrink down over those cables and well inside the case...a very tricky ask without opening the case.

[LongRat]

Interesting debate.
I have repaired this pack with heat shrink. Personally I still prefer packs with wires rather than sockets in the hard case. With sockets, it is easy to plug them in reverse, or get some metal (like a chassis) across the terminals.
The WORST thing about hard case packs though is the open invitation for resellers to charge twice the price for the same cells, because they are 'car specific'. And often inferior.

[bodgit]

Heat shrink will offer less protection than the origional silicone wire had if you get a similar heavy shunt. Also there will be a lot of flex at that point which will may over time crack the heat shrink as you plug in and out. If you are going to carry on using it at least get some silcone sealant between the wires or you could end up with a burnt out car.
Any pictures of your repair?

[LongRat]

This heat shrink isn't going anywhere. It is the twin layer type (plastic/glue), almost as thick as the silicone it is over, once shrunk.
Plus, I will not be using this for racing, it will go into my crawler truck so no more hits. It is one of my weaker packs.

[terry.sc]

As has been said above that's down to the design of the case, not because it's a hard case.

Originally Posted by LongRat

Lithium batteries in cars do not fail by structural rupture or penetration. I have yet to witness any failure that has not been caused electrically. In which case, containing the cells actually presents more hazard. In the instance above, the hard case is actually the cause of the failure.

Would you run soft pack on a touring car, where half the battery hangs over the side of the chassis? Unless you can guarantee that there would never be a pack failure due to impact, penetration or bending in any accident and that a soft pack being hit by a car would never be damaged then a hard pack is always the safer option and the only ones that will be passed by the EB.

If your argument is that they are overpriced because they are in a hard case, as the case adds pennies to the cost of the pack do you honestly think they would charge less if we used soft cased packs. There are cheap alternatives, several Gens Ace packs are BRCA legal and available for around £25.

[LongRat]

Originally Posted by terry.sc

If your argument is that they are overpriced because they are in a hard case, as the case adds pennies to the cost of the pack do you honestly think they would charge less if we used soft cased packs. There are cheap alternatives, several Gens Ace packs are BRCA legal and available for around £25.

Yes. The fact is that performance-competitive 2S packs have been available for over 5 years at less than £20, but they aren't BRCA legal. A good example is the Loong-Max Tipple 4000 - I have run them in touring cars for years, without failure, and they have compared (very) favourably with others running packs costing 4 times as much. I agree that now, the Gens Ace packs are good value. The cells of this quality have been around for years but not with a hard case. The car scene is ALWAYS the last to catch up.
I have not run a touring car where the battery overhangs the chassis side. But I have folded packs like a banana without failure. The fact that my pack above has a poor case design I completely agree with, but this battery was BRCA legal when I bought it.

I guess what I am getting at is that it would be good to see battery enclosure as part of the vehicle, not the battery. If a car design makes a battery vulnerable (overhang touring example) maybe the car designers should incorporate a case for the battery. Not really sure why I am saying this as I know it isn't going to happen. It just annoys me that 'racing' hard cased packs are so much more costly than the equivalent battery without the case that I use in planes etc.

[terry.sc]

Originally Posted by LongRat

Yes. The fact is that performance-competitive 2S packs have been available for over 5 years at less than £20, but they aren't BRCA legal. A good example is the Loong-Max Tipple 4000 - I have run them in touring cars for years, without failure, and they have compared (very) favourably with others running packs costing 4 times as much. I agree that now, the Gens Ace packs are good value. The cells of this quality have been around for years but not with a hard case. The car scene is ALWAYS the last to catch up.

The car scene has usually been at the forefront of technology but cars have much higher requirements than aircraft, we needed to see lipos capable of supplying currents and capacity that were never needed in aircraft before they were suitable for widespread car use. Whether you or I think soft packs are safe is irrelevant, you've got to think that adding a hard case has to be an improvement in general safety considering the impacts r/c cars take in normal use compared to planes, so it makes sense to only allow lipos when they started making them in suitable hard cases.

Sure the Loong-Max Tipple 4000 is cheaper than a BRCA legal pack, but then there are requirements that cheap packs don't meet before they are race legal and that they must be widely available in the UK and have proper product support, I'm sure product insurance isn't particularly cheap for a lipo supplier. One supplier importing and selling direct isn't classed as widely available, and it also means the importer doesn't have to allow the cost and profit margin for any retailer in the final price so they can sell them cheaper. If they were to be BRCA legal the retail price of these cheap cells would end up being the trade price, with the model shops profit margin and vat added on.
I'm not justifying the high price of legal batteries here, I think the prices are pretty ridiculous myself but I can see the reasons behind them.

I have not run a touring car where the battery overhangs the chassis side. But I have folded packs like a banana without failure.

Just because it has not happened to you with the particular packs you use doesn't mean soft packs are inherently safe in a crash, just look through the plane and helicopter forums for tales for lipos going up after an accident.
I've raced with nicad and nimh cells for 32 years now and never had one pop or explode, doesn't mean it doesn't happen.

It just annoys me that 'racing' hard cased packs are so much more costly than the equivalent battery without the case that I use in planes etc.

It depends what you mean by "equivalent battery".

If you want a Team Orion 4000mah 35C aircraft soft pack it will cost you £65, all of Team Orions car packs of similar capacity, even with much higher current rating, are cheaper than their aircraft pack. At the other end of the scale the Gens Ace hard and soft lipos are also pretty comparable in price between their hard and soft packs as well.

Claiming that a race legal pack from an R/C car specific company is more costly than a Chinese manufacturers relatively mass produced soft pack just because they have the same capacity and C rating isn't really a direct comparison. Batteries for racing are a tiny minority of the r/c car market, only around 5% of all r/c cars sold are raced and having gone through the necessary procedures to make them race legal a supplier might end up only selling a few thousand worldwide as bashers will stick to nimhs or cheap lipos. This means race legal batteries are never going to be as cheap as mass produced soft packs that are used in planes, helicopters, airsoft guns, power tools, etc.

[LongRat]

Yeah we will have to live with legal racing battery prices, nothing we can do about that. At least it is still cheaper than the bad old Nickel days.

By 'equivalent', I mean spec equivalence - voltage and capacity. I never pay attention to C ratings as in my experience they have been generally BS. I've got 25C packs with lower IR than 35C packs, for example. Then again if you discharge any 50C pack at 50C continuous, the pack will not survive - whoever made it.
In the case of hard cased packs having uncased equivalents, many times it turns out the cells are not actually the same. Not sure about Orion, but once the cells are encased in hard plastic who is to tell what the manufacturer of them is? An extreme example was a guy at our club who bought a 2S LiPo pack which wasn't performing well from new. He split the case apart only to find a rack of 6 low-budget 2/3A NiMhs! Quite funny and not that relevant, but you get my point.

[Origineelreclamebord]

...Another reason to use bullet connector-style LiPos then I guess?