STrRedWolf wrote:That said, I dug into a bit of googling and got 288 hp out of a 1000 lbs lithium ion battery, spec'ed for 56 kWh 375 V, on a Tesla Roadster 2011.
Scaling to 4400 hp (that of a Siemens Charger SC-44) you would need about 15,278 lbs of battery, or nearly 7.7 US tons of battery. In comparison, the SC-44 weighs 264,556 lbs (or 132.3 US tons) and an AEM-7 is 102 US Tons.
Your calculation (288 HP from a battery weighing 1,000 lb) is OK as far as it goes. However it neglects one key parameter: For HOW LONG can this battery produce 288 HP?
Let’s do some calculations:
Assuming Tesla's published battery energy storage capacity of 56 kw-hr for a 1,000 lb battery is valid, then
56 kw-hr/.746 hp per kw = 75.1 hp-hr.
75.1 hp-hr/288 hp = 0.26 hours.
In other words the Tesla battery can deliver 288 hp for only about 15 minutes until it is fully discharged. (In reality duration will be somewhat less on account of internal battery heating, etc)
Now let’s take your Tesla battery example and scale it up for a 4,400 hp locomotive. For sake of argument I’ll assume the battery-electric locomotive must have endurance equivalent to an SC-44 Siemens diesel-electric with a full fuel tank (1,800 gal).
1 gal diesel = 40.7 kw-hr (US Dept of Energy data)
1,800 gal diesel x 40.7 kw-hr/gal = 73,250 kw-hr.
Assuming an overall energy conversion efficiency of diesel to electrical of 40% (best, state of the art diesel engine). Then the actual kw-hr available for traction from a full tank becomes
73,250 x 40% = 39,300 kw-hr
So we need a battery that can store 39,300 kw-hr in order to match the performance and endurance of the SC-44 diesel. Using your 56 kw-hr per 1,000 lb of battery as basis, the weight of this hypothetical battery becomes:
39,300 kw-hr / 56 kw-hr per ton = 702,000 lb.
That’s 351 tons of battery(!)
Imagine the tender necessary to carry 351 tons of battery…..figure (4) 125 gross ton cars. Or the additional locomotive power required just to lug the battery tender cars along in the train.
So much for the weight. Now let’s examine battery cost…
From Tesla’s web page we learn Li-ion batteries currently run about $190 per kw-hr of storage. So the price for a battery pack for our hypothetical locomotive:
39,300 kw-hr x $190/kw-hr = $7,467,000
To this you must add the cost of several “tender” cars required to carry 351 tons batteries – perhaps another $½ million?
Bottom line: Using state of the art Li-ion batteries, our hypothetical battery powered locomotive is going to need 351 tons of batteries priced in excess of $7 million PLUS a 4 or 5 car tender - in order to offer performance competitive to a modern diesel locomotive.
Will we be seeing a battery locomotive in commuter service anytime soon? I submit not likely....