lipo misinformation

[ozzie-crawl]

i was talking to some guys yesterday that hadnt long gotten acouple of fe boats.
one of them raised the concern that if his lipos got wet it would blow his whole boat up.
i was told the same thing from a lhs when i first brought lipos for a boat.
story i was told.
guy driving down the road in his station wagon,electric helicopter in the back
a bottle of water tips over and spills water on lipos,the resulting explosion is that big it blows the rear hatch of the station wagon.
anyone else heard any crazy lipo stories

[m4a1usr]

i was talking to some guys yesterday that hadnt long gotten acouple of fe boats.
one of them raised the concern that if his lipos got wet it would blow his whole boat up.
i was told the same thing from a lhs when i first brought lipos for a boat.
story i was told.
guy driving down the road in his station wagon,electric helicopter in the back
a bottle of water tips over and spills water on lipos,the resulting explosion is that big it blows the rear hatch of the station wagon.
anyone else heard any crazy lipo stories

Well that story is an easy one to debunk. Stick a lipo pack in a bucket of water. If it explodes you know the stories are true. But I bet after hours of being dunked your going to find they are just wet and slightly drained. Water does not conduct well enough to "shorten" out a pack. Back when we ran brushed motors one of the burn in or seating the brushes methods was to immerse a motor in a cup of water. Salt water is more conductive but still not enough to short out a pack.

Over charging is the only credible story I have heard that causes a lipo pack to burn or become unstable.


John

[egneg]

I haven't seen anything personally but I did read all the horror stories about how they went up in flames if you looked at them funny.

[ozzie-crawl]

john wasn't saying it was something i believed,just a couple of stories i have heard people say.

[westbeach]

Time to call in MythBusters. I call this Busted!

[m4a1usr]

Just remember one of the disposal methods for bad/ damaged/ at risk lipo packs is to what? Dunk it in a bucket of water, right?

Now packs going going high order is something that happens. Usually due to damage from a crash, deformation, shorting the connections, charging at abnormal rates, etc. Abuse.

But really getting a pack wet? That alone will not cause lipo packs to become time bombs or become unstable. Water alone is not the effecting factor. Got to be something else.

John

[Rex R]

not to suggest that high output batteries shouldn't be treated with respect, but I haven't heard of any 'mysterious' explosions after lipos got ejected into the pond I run at. I have seen/heard NiMH cells 'venting'(after being abused) though.

[properchopper]

Let's be fair to the clerks at our LHS - these poor folks are the ones who previously applied for work at the 99 cent store but failed the price-check test.

[ozzie-crawl]

i think these stories started at lhs,most of them no nothing about lipo battries.
plus they have the old "i dont stock it so its voodoo magic" attitude.
just out of my own couriosity a few weeks ago i rang 4 local hobby shops,my question was simple do they stock any neu or castle/neu motors.
none of them had even heard of such things,one shop put me on to there resident electric expert,this is his answer "none of us have ever heard of such motors as we dont stock cheap chinese rubbish"

[Fluid]

Salt water is more conductive but still not enough to short out a pack.

Actually salt water is a fine electrical conductor, and it is for that reason that many LiPo pack makers recommend putting a discharged pack in a bucket of salt water (not fresh water) prior to disposal. The salt water makes a direct short between the + and - leads, draining the pack safely by controlling any heat generated.

LiPo cells are watertight, meaning no water can get into the chemicals unless the cells are cut. Water damage from wet cells is usually due to corrosion of the tabs and leads.


.

[m4a1usr]

The salt water makes a direct short between the + and - leads, draining the pack safely by controlling any heat generated.


.

Incorrect. Actually a salt solution is no where near a direct short. It takes days if not weeks to discharge any pack immersed into a salt bath. While a faster discharge will occur using a salt solution both will eventualy do the job. The electrical conductivity of a salt solution improves with the percentage of salt ions being suspended but it will never be a direct short. That would only occur with a conductor such as metal.

http://www.rctoys.com/pdf/thunder-power-disposal-of-old-damaged-lipo-batteries.pdf

John

[Simon.O.]

Dangerous lipos.......dangerous users more like.

Here is a copy of my post form another thread.

In all fairness to the "dangerous and explosive" lipo grenades that we like to power our models with I have tried a few things.

Over the last few months I have puffed a few cells and they are no longer considered safe for me (by me) to charge or use.
These are some of the tests that I did.

Run over by the tyre of my Hilux (Four-runner) and was squashed. It vented and that was it. Just a bit of gas
Repeatedly thrown across the concrete driveway. Nothing happened so I ran that over too.
Hit with a crow-bar pointy end first. A small flash and vent
A near full 4S pack that vented a cell in the boat due to water ingestion.
This one was left with a 100W lamp to dump the pack to zero. No puff or anything. That got run over too.
.

QUALIFIER
I will say now that all of these events occured under quite safe and controlled conditions.
I know what risk minimisation and hazard control is.
There is very little chance ( you can never say no way ) of me being hurt or any property being damaged.

DISCLAIMER
I did this so that I might know how "dangerous" lipo cells are.
I DO NOT advocate anyone trying this. If you do and get dead don't blame me.

Lipos are fine if handled with a bit of care and common sense.

Don't get me started on how dangerous petrol is.

btw you should have seen some of the destructive testing I have done to Nimh cells...........BOOOOOOM !!

[andym]

Run over by the tyre of my Hilux (Four-runner) and was squashed

Simon are you going to tell the truth now???? You and I both know you forgot to take the lipo out of the boat

[Simon.O.]

Simon are you going to tell the truth now???? You and I both know you forgot to take the lipo out of the boat

I have never run over one of my hulls while the battery was in it.

[785boats]

I've got one for Ya. And yes it was my fault.
My little 25" mono (Bulletproof) has an anti spark resistor soldered across the terminations of the safety loop inside the boat. (See the Pic.)
Even though I disconnected the safety loop one day, I forgot to disconnect the batteries inside the boat. The batteries were HiModel 2 x 2s 3600mah 25c in series.
After I got home late from a days sailing & unpacked the half a dozen boats & gear, I forgot about the batteries until 5 days later when I was going to start charging some packs for the weekend.
When I measured the voltage they were down to 0.69V per cell in one pack & 0.70V & 0.71V in the other pack.
Now most misinformation would say that they were stuffed & should be thrown away. But as they were discharged under such a light load & were in no way puffed I figured they were worth saving.
Now as the lipo charge cycle would not recognise the low voltage to start charging I placed them on the NiCd cycle at 0.5A. One pack at a time.
It took about 8 minutes to bring the voltage up to 3.3V.
I let them rest for about 30 minutes & the voltages had dropped to 2.19, 2.12, 2.55, 2.79. so I charged them again on NiCd up to 3.5 V, then plugged them into a balancer to balance them & left them for a day.
As they were still pretty closely balanced I then did a full balance charge on each pack.
Pack one cutout after 112 minutes at 4.11V/cell taking on 3960mah.
Pack two cutout after 118 minutes at 4.14V/cell taking on 3876mah.
I then topped them up to 4.18V/cell with an extra 200 or so mah.
Their first run in the boat I stopped at 3.81V/cell (resting voltage) and they both took on 2182mah & 2188mah respectively, topping off at 4.18V / cell.
And they are still running fine after half a dozen more runs.
No heat or puffing problems & just as much kick as they always had.