Battery Room Venting 2

[peterpylon]

Can anyone give me a quick rule of thumb method/ formula to calculate the minimum safe (below the lower explosion limit LEL) ventilation rate required to ventilate a battery room whilst boost charging both valve regulated and lead acid batteries?

 

[rcw retired EE]

CFM given off by battery at maximum charge rate= (Amps x # of Cells x 0.000269 CFM/amp-cell).

From IEEE 484 "Recommended Practice for Installation Design and Installation of Large Lead Storage Batteries for Generating Stations and Substations."

That formula gives the amount of H2 the battery releases during an overcharge. Use the current limit setting of the charger for the amps.

Size ventilation rate for the maximum H2 release to be conservative. Then talk to someone who knows more about HVAC than me.

 

[itsmoked]

Nice equation rcwilson. I hadn't seen that before.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[alehman]

Some of the battery manufacturers have a handy Excel spreadsheet for this.

Alan
----
"It’s always fun to do the impossible." - Walt Disney

 

[sibeen]

The pertinent Australian standard for this states that to keep the hydrogen concentration below 2% in a battery room or enclosure the following equation should be used:

qv = 0.006nI

Where qv = minimum exhaust ventillation rate, in litres per second.

n = number of battery cells

I = charging current.

 

[alehman]

U.S. code is 1%. 4% is the lower explosive limit.

Alan
----
"It’s always fun to do the impossible." - Walt Disney

 

[cherry2000]

I had developed a simple spreadsheet which calculates the Hydrogen volume generated by GU-9 Enersys Wet cell battery. The no. of hrs required for the dangerous built-up is calculated. The sheet is attached for your use. The hydrogen evolution figure should be taken from the battery vendor.

Another method used in the IEC regulated countries, is the one given in IEC 60079-10. See the document at:

http://www.tchouvelev.org/Documents/UpdatedDocs/HazLocs_Code_Requirements_Comparison.pdf.

Here a hypothetical volume is calculated and then the correct conclusions are drawn.

The LFL of Hydrogen is well known at 4%. The restricted concentration of 1% comes from NFPA 30. In IEEE 418, is is in Sec 5.4 Ventilation that a value of less than 2% is mentioned.

One useful article is located at:

http://www.battcon.com/PapersFinal2008/ODonnellPaper2008PROOF_6.pdf

 

[peterpylon]

Many thanks to you all. All comments, formulae and links are very helpful.

Regards
peterp.