Paris Air Show

787 Battery Modification Kit Hits Performance, Weight

 - June 13, 2013, 11:05 AM
The FAA has approved a modification kit for the Boeing 787 batteries to be practically exempt from a risk of fire.

The FAA-approved Boeing service bulletin for the 787 calls for modification of the charger and battery monitoring unit to narrow the acceptable level of charge. In essence, this means lowering the maximum charge allowed and raising the minimum level of discharge allowed. In other words, it cuts the performance gain the lithium-ion technology is supposed to bring.

Even worse, the additional weight of the modification kit is close to 185 pounds. A large part of it is the stainless-steel enclosure meant to isolate the unit from the rest of the equipment in the electronic equipment bays. Each of the two 787 batteries weigh 63 pounds, versus 107 pounds for one less-performing nickel-cadmium battery on the 777.


If they had stuck to the standard 24/28 volt electrical system, the option to retrofit 4x standard SLA 12v batteries [not to mention Ni-alkaline equivalents] would have been available in January 2013.......
Reducing the cycle-depth of the [electrically excellent] LVP-65 cells currently in use, must have reduced the capacity to about 50 Amp-hours, and there would actually have been a weight saving by fitting SLA batteries. There would have been a cost saving of about $20,000 per 787 battery, not to mention the saving of about $500M in trying to 'solve the thermal problem'.
The improvement in safety and reliability would of course have been priceless............

The difference in weight they are trying to save in the batteries could be the difference between an overweight passenger like 'Joe Blogs' who weighs 140 lbs, and 'Fred blogs' who weighs 225 lbs.

I could understand if the weight was more like a ton they were trying to save, but in this case I would stick with the heavier but much safer batteries that they have used for years before.

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