Re: Q:NEDRA on batteries..

[Bill Dube <billdube@killacycle.com>]

At 10:20 AM 12/28/99 -0800, you wrote:
>Bill Dube wrote:
>> There are records at the lower voltages using flooded batteries,
>> but this is basically because no one has sought that record that
>> was running non-flooded batteries.
>> 
>> AGM and TMF type batteries have a far superior power-to-weight ratio...
>> They can deliver more watts per kg than flooded batteries can. In drag
>> racing, the most important single factor is power-to-weight ratio...
>> On the dragstrip, there is really no advantage to flooded batteries...
>> they are not as safe during a crash. They also don't recharge as quickly
>> and produce more gas when they are charged. They also tend to cause
>> corrosion on connections and on hold-down components.
>
>Gee, Bill; why don't you tell us what you really think? :-)
>
>When all-out, cost-is-no-object performance is all you want, you build
>things that are totally focussed on that one goal, and give up
>everything else to get it. This is fine if you have a vehicle that is
>purpose-built for drag racing, and used for nothing else.
>
>But, a great many people race for fun; winning isn't everything. They
>want to drive the same car 7 days a week that they race on the weekends.
>They race the "wrong" car, just because they like it. They use the
>"wrong" batteries, or motor, or controller, because they cost less.
>
>And you know what? they STILL have lots of fun, and can even win! High
>tech batteries, controllers, and other slick gadgets can blow up; old
>tech contactors and batteries work anyway. He who finishes the race
>beats those who don't!

	The fellow that asked the question owns a dragster. It is most definitely
not a daily driver but is purpose-built for drag racing. Buying flooded
batteries for this vehicle would be a waste of money. For the same amount
of money in TMF batteries or AGM batteries, the vehicle would turn better
times on the strip. 

	Notice that I didn't say the same weight or a-hr capacity. I said the same
dollars spent. 

>
>On to your battery complaints. 
>
>Flooded batteries can be just as safe in a crash; it all depends on your
>battery boxes. Can you imagine what it would take to puncture the 3/16"
>steel case of a fork lift flooded battery? Or, consider that many sealed
>batteries do not have high pressure cases; their case is no thicker than
>a flooded case. And, just how dangerous do you think battery acid is?

	Again, we are talking about a dragster, not a fork lift. The battery boxes
one would use on a dragster will deform during a collision at the speeds
that dragsters travel. If the batteries are flooded, acid will go flying.
If they are AGM or TMF type, only a few drops will get loose. Virtually no
acid spilled is safer than lots of acid spilled. 

	Also, batteries burst on a regular basis on the strip. When AGM or TMF
batteries burst, just a few drops of acid is spilled. When a flooded
battery bursts, acid leaks out everywhere. Battery boxes for flooded
batteries must be well vented. A car on it's side or back with flooded
batteries will leak a significant amount of acid out of the vents. A burst
flooded battery will likely spray acid out of the box vents.

	Safety on the dragstrip is more than just acid skin contact. Acid on the
track is quite slippery and could cause another vehicle to skid and lose
control. It could get on seat belts and other safety-related items and
cause them to fail at a later date. It can react with the track traction
compound to produce toxic vapors. It can get inside frame members and cause
hidden corrosion.

	Keep in mind that the NHRA safety rules require catch cans for all fluids
that can come out of the car. This is because an unexpected loss of
traction can be deadly. It's important to keep the context of a drag race
in mind.

>
>Floodeds can be recharged just as quickly as sealed; maybe quicker
>because gassing is a way to prevent damage from overcharging that sealed
>batteries don't have.

	All the folks with TMF type batteries charge in 15 minutes or less. I run
my pack down to about 30% DOD or more each run and thus replace at least
70% of the capacity in 15 minutes. This is completely impossible with
flooded batteries. Think how your typical 75 a-hr flooded battery would
react to a 15 minute charge at about 300 amps. You would warp the plates
and blow the tops off. Thermal runaway is a given.

 The amount of gas generated is reasonable unless
>you are in some kind of runaway charging situation (in which case, the
>sealed battery would fail, too).

	TMF batteries don't get very hot during a charge. It is possible to
thermally run away, but it doesn't happen often.
 
>
>Corrosion is a function of how well you control your charging. Floodeds
>don't make a mess if you don't overcharge them.

 Or you don't torture them during discharge. On the strip, in a dragster,
you are going to pull on them hard enough to cut the terminal voltage in
half. Weak cells will boil over and/or burst, sending acid everywhere. AGM
and TMF batteries burst, but there is practically no acid to clean up.

>
>I think racers should be free to use whatever they feel like using, as
>long as they do it safely. Rather than legislate against floodeds, just
>make sure they are used safely. They already have some built-in
>disadvantages (like higher internal resistance) that will automatically
>keep them from being used by the cost-is-no-object crowd.

	Flooded batteries can be used in closed cars (like a sedan) on the strip.
You cannot use flooded batteries in an open car (like a dragster) or a
motorcycle. 

	As far as costs go, you should do a few calculations before you make that
assumption that AGM or TMF batteries cost more for a given elapsed time. If
you pick a vehicle and then pick a target ET, you will find that AGM and
TMF batteries will cost the same or less than flooded batteries. Remember
that the amount of HP you must produce to achieve a specific ET will go up
as the vehicle weight goes up. 

	 It's not just the battery weight alone. You also have to support and
contain the batteries. (You suggest 3/16" steel on all sides of the
batteries. Also, as the HP goes up, the weight of the drive system must go
up too. Also, more HP means more money spent on the motor(s) and
controller(s) not just batteries. 

	When the drive system (including the energy source) is a significant
portion of the vehicle weight, changing the specific power of the drive
system makes a huge difference in the overall scale of the vehicle when you
fix the performance goals. 

	A good example is the "National Aero-Space Plane" (for those that may
remember it.) If slush hydrogen was selected as a fuel instead of plain old
liquid hydrogen, the energy density went up about 13%. This cut the size of
the vehicle more than in half. The gross vehicle weight was reduced by a
factor of five. The same sort of math works for dragsters too. 


Bill Dube'  billdube@killacycle.com
check my website at:
http://www.killacycle.com