Author Topic: Re: Battery Safety  (Read 2642 times)

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Offline cabbage

Re: Battery Safety
« on: Jul 28 2011 17:06 »
NO NO NO NO NO!!!!!

John....

You seem to have an extremely cavalier attitude to stored power systems.

When charging or discharging batteries get hot. This causes them to expand. Normally the air around them is sufficient to keep them cool whilst charging or discharging. BUT there can be no coolant air around your cells since you have stuck them together. You are EITHER going to have to take them out and charge them in a coolant draught from a fan -or pre-cool your battery pack in the fridge?!?!?!

Please tell me that this configuration method is your own unknowing idea and not another potentially lethal one from Messrs "Strikealight"?

PLEASE Take your stuck together battery pack to bits and rebuild it in a sponge honeycomb sleeve system.  The sponge sleeves are easy to find and stick together with UHU or similar. This will allow air to move between the cells.

From my background I do know an awful lot about stored power systems, the sponge tubes are cheap...

regards

ralph

« Last Edit: Jul 29 2011 09:16 by John Candy »

Offline John Candy

Re:Battery Safety
« Reply #1 on: Jul 28 2011 18:41 »
Ralph,

Thank you for your concern but I have used the same method in all my locos and I can assure you the batteries do not get hot.
I use a "smart charger" but I guess if one were to force charge them at a fast rate then they would get hot.

When charging, I always remove the false "coal load" from the tender or bunker and the batteries get no more than luke warm.
The cells are 2100mAh AA size with a nominal 1.2V rating.

I was concerned they might get hot when I first used this method but preliminary tests showed they became just slightly warm.

Regards,
John.

P.S. Messrs. Strikalite supply their custom battery packs "shrink-wrapped" so there is no air circulation between the cells.


« Last Edit: Jul 29 2011 09:17 by John Candy »
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline cabbage

Re: Battery Safety
« Reply #2 on: Jul 28 2011 19:01 »
Ok.....

If you would like a second opinion then I would suggest you e-mail Tony Walsham of Messrs RCS Australia. Although I do warn you his reply might not be as "polite" as mine would be...

regards

ralph
« Last Edit: Jul 29 2011 09:17 by John Candy »

Offline John Candy

Re: Battery Safety
« Reply #3 on: Jul 28 2011 19:49 »
Ralph,

Attached is a photo of a "Strikalite" cell pack.
Below is the "blurb" from their website relating to the "Smart Charger"....

Type: Nicad / NiMH Smart charger   
 
Capacity: 500mA
Voltage: 90-240v
Description: This is a battery charger that will charge 14.4volts up to 24volts (12-20 cells) worth of Ni-Cad / NiMH batteries so it will do anything from 500mAh cells and up.QUESTION Will it damage the battery? No its a -Delta V pulse charger so it will automatically cut off when battery is charged. It charges at 500mA then drops to a trickle charge so it will not get your battery hot through excessive input current


My models are insured against damage (all risks) and "Strikalite" have warranted their procedures to be safe.

If something goes wrong and it is due to their lack of "duty of care" then I will claim from my own insurers and they can make a decision as to whether or not pursue a subrogated claim against "Strikalite" and their Product Liability insurers.

Regards,
John.
« Last Edit: Jul 29 2011 09:17 by John Candy »
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline cabbage

Re: battery Safety
« Reply #4 on: Jul 28 2011 20:41 »
Ok...

Let me put simply.

You block up the vent holes of the battery with glue the Hydrogen they produce does not vent to the atmosphere -they explode.

Sticking batteries together with glue is a VERY BAD IDEA.

I honestly hope that you have no cause to regret your method of assembly. I do not know what the English Law term is -but the Scottish Law defence term is "Applied Stupidity"...

You have just had the benefit of 25 Years of power system design given to you free. The normal rate 2 years ago would have been £250 per hour or part there of.

PLEASE TAKE IT.

regards

ralph

 

Offline John Candy

Re: Battery Safety
« Reply #5 on: Jul 28 2011 21:23 »
Ralph,

What vent holes?
These are not acid cells they are NiMh and have no vent holes.
The parts which are glued are the long cylindrical (solid) sides...as with a standard AA battery used in all manner of domestic items from clocks to TV remote controls, etc.
I agree that when charging automotive type cells with H2SO4 content they need to be vented and hydrogen build-up can be ignited by a spark from the terminal blocks when connecting/disconnecting the charger.
Radio control transmitters (e.g. Futaba) are supplied with sealed NiMh cell packs which are recharged in situ via a socket in the transmitter case.

Regards,
John.
« Last Edit: Jul 29 2011 09:17 by John Candy »
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline cabbage

Re: Battery Safety
« Reply #6 on: Jul 28 2011 22:14 »
OMG....

Ok....

Follow the URL below and read the section marked 4.4 SAFETY.

http://en.wikipedia.org/wiki/Nickel-metal_hydride_battery

Now do you understand?

regards

ralph
« Last Edit: Jul 29 2011 09:18 by John Candy »

Offline John Candy

Re: Battery Safety
« Reply #7 on: Jul 28 2011 23:22 »
<Quote>Modern NiMH cells contain catalysts to immediately deal with gases developed as a result of over-charging without being harmed (2 H2 + O2 ---catalyst ? 2 H2O). However, this only works with overcharging currents of up to 0.1C (nominal capacity divided by 10 hours). As a result of this reaction, the batteries will heat up considerably, marking the end of the charging process.............................................There is an inherent risk with NiMH chemistry that overcharging will cause a buildup of hydrogen, causing the cell to rupture. Therefore, cells have a vent. Hydrogen will be emitted from the vent in the event of serious overcharging.

I construe this as meaning that only in the event of serious overcharging will there be hydrogen emitted and the cell may overheat and/or rupture.
The "smart charger" I have is designed to prevent that situation from arising.

O.K. so the "fail safe" could itself fail but then so could many other "fail safe" devices around the home, in the car, etc.
Only recently there were reported incidents of Beko refrigeration devices causing house fires when a cutout failed.
I take your point but I conclude the risk to be manageable.

Regards,
John.

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« Last Edit: Jul 29 2011 09:29 by John Candy »
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