Idea for lipo cases?

Hey Guys,

I have a number of customers who are interested in Lipo packs. While I screen my clients to make sure they are familiar with them, I still have concerns about people using large Lipo packs in bikes. So, to that end I had an idea. What do you guys think about a billet aluminum Lipo case for safety? Now, I know the first question will be "For how much?" That I do not know yet. I have to calculate the material cost and machining time. However, especially for the high-end customer (I have quite a few), adding a case to a $600 to $1000 pack is not out of the question. Also, remember, Lipo packs are very small. A 48 volt 5AH pack is roughly 7 inches long by 3.5 inches wide by 2.25 inches thick. They can be machined from a solid block, or be made in pieces and bolted together.

Anyway, again, I do not know the cost as of yet. But, assuming it is not out of reach, what do you guys think about this? I know the cost is always a factor. But, if that is the case for a particular customer, Lipo would not be considered anyway.

So, does this sound like a waste of time?

(oh as a side note, these cases will not stop the development of my drive unit clamps. Those are already scheduled to be machined mid July). :wink:

Matt

I've always thought that a case made from an alloy extrusion, like the Infineon cases, but with nice CNC machined billet end caps would be neat. Only challenge would be finding a source for extrusion of a suitable size.

The main advantage is that it'd cut down on machining time, plus would provide a fair degree of protection to the pack.

Might be very popular if it looks good. If it was modular, say different extrusion lengths, or perhaps stackable extrusions for multiple packs, that'd be nice.

My local alloy stockist seems to have some case-type extrusions in their printed catalogue, but no prices or other info.

Jeremy

I think you will have to be very careful putting li-pos into a semi sealed ridged case wont you be making a sort of potential large grenade.. :| just a thought..

recumpence said:

Hey Guys,

I have a number of customers who are interested in Lipo packs. While I screen my clients to make sure they are familiar with them, I still have concerns about people using large Lipo packs in bikes. So, to that end I had an idea. What do you guys think about a billet aluminum Lipo case for safety? Now, I know the first question will be "For how much?" That I do not know yet. I have to calculate the material cost and machining time. However, especially for the high-end customer (I have quite a few), adding a case to a $600 to $1000 pack is not out of the question. Also, remember, Lipo packs are very small. A 48 volt 5AH pack is roughly 7 inches long by 3.5 inches wide by 2.25 inches thick. They can be machined from a solid block, or be made in pieces and bolted together.

Anyway, again, I do not know the cost as of yet. But, assuming it is not out of reach, what do you guys think about this? I know the cost is always a factor. But, if that is the case for a particular customer, Lipo would not be considered anyway.

So, does this sound like a waste of time?

(oh as a side note, these cases will not stop the development of my drive unit clamps. Those are already scheduled to be machined mid July). :wink:

Matt

Click to expand...

That kind of money for a case seems quite ridiculous and I think even the well-healed would balk at that. If you simply want a case to protect a battery that's placed inside a bag then something like Batteryspace uses is all you need.





If you're designing an enclosure that will mount on a downtube for example then appearance is more important but it can still be done for a far lower cost than you mention.

-R

I never mentioned cost. I mentioned the price typical Lipo packs cost. It pays to read close. :wink:

An extrusion would be nice.

Also, the case would not be totally sealed. The wires would exit out a hole that would have a rubber gromet. That hole would act as a vent if needed.

Hmm, I need to look into extrustions more.

Matt

recumpence said:

I never mentioned cost. I mentioned the price typical Lipo packs cost. It pays to read close. :wink:

An extrusion would be nice.

Also, the case would not be totally sealed. The wires would exit out a hole that would have a rubber gromet. That hole would act as a vent if needed.

Hmm, I need to look into extrustions more.

Matt

Click to expand...

Oops my bad

The cases I mentioned run 10-20 dollars which is a small price to pay for some extra protection. An enclosure also makes it easier to handle a battery if a person is constantly placing it in a trunk bag and removing it for charging.

AmpedBikes is working on coming out with a downtube mounted battery box like the one Bionx and Crystalyte have and has talked about a $40 price point or less when purchased with one of their batteries. It is going to be plastic and their battery is LiMn (same one as eZee uses) so not as volatile as LiPo.

ItsElectric currently sells the empty Crystalyte NiMh downtube battery box for $55 but it's also plastic.





-R

I've sourced enclosures from
xtech or extrusion technologies.

rose-bopla sells black anodized extrusions by the meter
with different cover options...

Using billet aluminium just sounds like an awful lot of machining and shavings on the floor, for what is essentially a hollow container.

I like the extrusion idea better.

Grinhill said:

Using billet aluminium just sounds like an awful lot of machining and shavings on the floor, for what is essentially a hollow container.

I like the extrusion idea better.

Click to expand...

+1

Matt

Hi,

Russell said:

That kind of money for a case seems quite ridiculous and I think even the well-healed would balk at that. If you simply want a case to protect a battery that's placed inside a bag then something like Batteryspace uses is all you need.

Click to expand...

Matt is concerned with protecting the rider from the potentially explosive Lipo.

recumpence said:

Hey Guys,

...However, especially for the high-end customer (I have quite a few), adding a case to a $600 to $1000 pack is not out of the question. Also, remember, Lipo packs are very small. A 48 volt 5AH pack is roughly 7 inches long by 3.5 inches wide by 2.25 inches thick. They can be machined from a solid block, or be made in pieces and bolted together.

Anyway, again, I do not know the cost as of yet. But, assuming it is not out of reach, what do you guys think about this? I know the cost is always a factor. But, if that is the case for a particular customer, Lipo would not be considered anyway.

Click to expand...

I think the ideal enclosure (particularly for the high-end customer would be something like the box on D's Stinky) that is aesthetically pleasing and protects the batteries from physical damage and moisture. If you come up with something that serves those purposes as well as protecting the rider from the Lipo even if you only use them with your high-end bikes its a good idea. If its something affordable and usable for a wider market so much the better.

Extrusions with end-caps sound like a potential winner. But I think there needs to be provision for mounting. I also think modular will be better if you can figure out the mounting issues for multiple boxes.

BTW Box or no box I'd seriously consider having customers sign a waiver before selling bikes with Lipo packs. I just listened to a lecture on health where the Doctor said when he gives the patient their dosages he uses a red pen to write it at the top of the form and circle. Then he has the patient read it back to him out loud and about 20% still don't get it right! He called it his attempt to cure dumb-brain syndrome.

recumpence said:

(oh as a side note, these cases will not stop the development of my drive unit clamps. Those are already scheduled to be machined mid July). :wink:

Matt

Click to expand...

Do you think the clamps will work with down-tubes which decrease in size as the tube gets closer to the BB (a fairly common configuration)?

I'm all for it, especially if you video the *testing* of them

For custom orders, I think this would be great. For more general purpose, I'd just point them (or get them yourself) to small 'Pelican' type cases.

I've found that Casesbysource.com has a great search feature. You can input your desired interior dimensions, and they will list every case available that is within a user-defined size range (slider adjustable).

http://www.casesbysource.com/

this is why i dont use lipo, the thought that i may get a vent is enough to make me steer well clear, not that i'm bashing lipo i'm not, it just isn't for me is all.
I think you'd be better off giving your non lipo savvy customers headway or 123's and save yourself the worry?
That said it would be fairly easy to make ally cases for the lipo packs and so i would ask the question.......
if you case the lipo with ally what thickness would you need to contain a vent? and moreover is it possible to make a lipo case and incorporate an "exhaust" so that in the case of a vent it could be channeled well away from the rider?

Cheers,

D

It would be very hard to contain a vent.

I think the best option would be a blow-off pannel, or an intentionally thin and weak wall somewhere that is designed to fail in a vent, and is oriented to direct the venting gasses away from the rider.

However, it's not like LiPos are all just little bombs. Use good cells, charge them right, never break the golden rules, and LiPo isn't going to cause you any hassles. Of the million RC toy users around the world running LiPo, there are about 15 documented LiPo horror stories, and about 12 of them were from gross user charging errors.

Gasoline tanks have caused 10000x the troubles of LiPo, yet nobody seems to mind, because they know if you don't set it off, it's not a problem. LiPo is really no different, people fear it because they don't see breaking the golden rules as the equilivant of touching a match to the gasoline, which is otherwise safe enough.

liveforphysics said:

It would be very hard to contain a vent.

I think the best option would be a blow-off pannel, or an intentionally thin and weak wall somewhere that is designed to fail in a vent, and is oriented to direct the venting gasses away from the rider.

Click to expand...

If you use an extrusion with end panels, you could make one end panel intentionally weaker to make it function as a blow-out. Hopefully this never happens anyway, but it is wise to plan for every possible event.

It always sort of concerns me to package batteries inside a metal case due to the possibility of shorts. Over time, vibration can cause insulation to wear through. I suppose you just need very good insulation material and you need to restrain the cells so they don't vibrate around inside. The insulation should also be tough enough to prevent shorts in the event of a crash that dents the case.

I totally understand Luke, although that said the point was for the "no experience users" who are more likely to make the mistakes/abuse them through lack of knowledge, in which case you need a failsafe of some sort for the event....errrr of a vent :lol:

Shorts were a concern of mine too Richard but my cells are shrink wrapped in fairly robust shrink and the box is lined also, so far so good, plus it's easy to line with thin plastic or whatever.
i think the blowable panel (leave it) is excessive and difficult to get right (who knows the pressures involved?) why not just have a section which flows down aforesaid "vent exhaust" ? that way you could channel to a completely safe area (rear of bike) without having to think about where the blowable panel would blow to?

All could be avoided with alternative batts tbh, i know lipo is best bang for weight but I'd rather carry the little extra weight and avoid the bang altogether

Cheers,

D

Hi,

liveforphysics said:

It would be very hard to contain a vent.

I think the best option would be a blow-off panel, or an intentionally thin and weak wall somewhere that is designed to fail in a vent, and is oriented to direct the venting gasses away from the rider.

Click to expand...

Isn't a blow-off panel potential shrapnel? Would a vent (as in duct, flue, outlet etc.) be better?

In addition to Cases I think if you sell bikes with Lipo you should include idiot-proof LVC's and Chargers. An LVC with a hard shut-off of the entire pack if any cell gets within 0.2v of the minimum. Maybe a custom single cell charger (or something doesn't depend on the user selecting the correct menu settings) that cuts off the entire charger if it detects a problem with any Cell. I'd consider using proprietary connectors to make it difficult to use different chargers.

If I was going to sell Ebikes with the option of Lipo I'd also consider making the default pack A123 and offer the option of a no battery purchase so customers who want Lipo could add their own batteries. This should absolve you from any liability and hopefully weed out customers without the proper knowledge. You could still provide Lipo cases.

liveforphysics said:

However, it's not like LiPos are all just little bombs. Use good cells, charge them right, never break the golden rules, and LiPo isn't going to cause you any hassles. Of the million RC toy users around the world running LiPo, there are about 15 documented LiPo horror stories, and about 12 of them were from gross user charging errors.

Click to expand...

I don't disagree with your contention that Lipo can be used safely but I'd like to point out a couple of issues:
1. Part of the issue is on Ebikes (larger packs than RC) they are potentially medium sized bombs.

Its pretty easy to make gross charging errors, even for a smart knowledgeable user:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=10739&p=164559#p164559

Warning, user error trumps smart chargers!

Postby johnrobholmes » Wed Jun 03, 2009 11:14 am

So I just ruined a perfectly good 5ah 6s zippy pack the other day. I drop my car off to get the tranny fixed and feel pretty slick riding my ebike home. Halfway through the ride the voltage starts to sag. Weird, maybe there are some bad cells or I forgot to charge the pack fully? Got home and went to charge up the packs and one was near dead flat at 8v. Seems that I forgot to hit synch mode on my charger, so it just charged one pack. Only about 20 cycles on that pack too

Click to expand...

I've been thinking about improving safety for LiPo on ebikes too and thought of covering the packs with the fireproof fabric used in those safe charging bags.
I would prefer to simply have the batts in a metal container for the good thermal conductivity but perhaps a fabric cover with a generous cooling vent at each end that are kept closed with velcro during charging would give the best of both worlds.
If cooling is not an issue then a fabric covered batt inside an Al box would offer max protection.

MitchJi said:

Its pretty easy to make gross charging errors, even for a smart knowledgeable user:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=10739&p=164559#p164559

Warning, user error trumps smart chargers!

Postby johnrobholmes » Wed Jun 03, 2009 11:14 am

So I just ruined a perfectly good 5ah 6s zippy pack the other day. I drop my car off to get the tranny fixed and feel pretty slick riding my ebike home. Halfway through the ride the voltage starts to sag. Weird, maybe there are some bad cells or I forgot to charge the pack fully? Got home and went to charge up the packs and one was near dead flat at 8v. Seems that I forgot to hit synch mode on my charger, so it just charged one pack. Only about 20 cycles on that pack too

Click to expand...

Click to expand...

That could've been prevented by the use of some sort of LVC monitor. It seems insane to run lipo without one and I would think the "smart LiPo users" would have their bases covered.

Personally, I don't like the idea of metal cases for any batteries. It increases the possibility of a short exponentially, and a short pretty much guarantees a significant problem with lipo. Just think about these packs or cells which are covered in only a thin layer of plastic getting bounced around in a metal box for thousands of miles. What we need as a material for battery boxes is one with good thermal conductivity without electrical conductivity. Sure there's a market for custom batt boxes, just not metal ones.

that's my 2 cents , which with the 582:1 exchange rate here is about $.00003

John

swbluto said:

That could've been prevented by the use of some sort of LVC monitor. It seems insane to run lipo without one and I would think the "smart LiPo users" would have their bases covered.

Click to expand...

LVC doesn't catch when all cells in series are not charged properly. When LVC hit the uncharged pack would already been around 13v while the charged pack was around low 20s.



I have made some styrene and Polypropylene boxes for my lipos. 1/8" thick seems to do the job well.

johnrobholmes said:

swbluto said:

That could've been prevented by the use of some sort of LVC monitor. It seems insane to run lipo without one and I would think the "smart LiPo users" would have their bases covered.

Click to expand...

LVC doesn't catch when all cells in series are not charged properly. When LVC hit the uncharged pack would already been around 13v while the charged pack was around low 20s.



I have made some styrene and Polypropylene boxes for my lipos. 1/8" thick seems to do the job well.

Click to expand...

I meant a cell-level LVC which I believe the cells can be accessed through the balancing connectors? Full "series" LVC seems like it'd only be ideal for a small enough number of cells in series (I'm somewhat comfortable with 2, max). I know if I were operating with a chemistry that is known to completely hit the dust (lest you risk explosion) once it goes under a given voltage, I would have some kind of voltage detection.