View Single Post
Old 09-28-2011, 09:51 PM   #20 (permalink)
IamIan
Master EcoModder
 
IamIan's Avatar
 
Join Date: Dec 2010
Location: RI
Posts: 692
Thanks: 371
Thanked 227 Times in 140 Posts
Quote:
Originally Posted by thingstodo View Post
Maybe with 3 times the battery, the battery draw would be lower and the kwh would rise a bit, maybe not.
Peukert effect are exponential ... for example:
For instance the same batteries with a Peukert k value of 1.2 and 180Ah at a 20 hour discharge rate will give.

~80Ah when discharged at ~500Amps.
or
~111Ah @ ~100Amps
or
~176Ah @ ~10Amps

etc.... etc.

The thing to keep in mind about Peukert Effects is that the Wh of energy are not really all lost ... it is just that the chemical reaction of the battery can not keep pace with the faster rate of the electronics ... for example if you discharged these same batteries at ~500Amps ... you might expect to estimate running out of ~500 Amp load ability in about ~80 Ah ... but if you were to then let the batteries rest for an hour or so you will be able to pull more from them again ... as the chemical reactions inside the battery that produce the electrical potential take time to catch up with the faster electronics ... Some old time BEV people call it 'growing Amps'.

Not all batteries have the same Peukert effects ... some handle high discharge rates much better than others ... A123 is among the best ... Lead Acid is among the worst... but even in Lead acid there is a significant variation from battery to battery.

Quote:
Originally Posted by thingstodo View Post
I guess it's a start.
Sure it's a start ... and with that many inverters you could power a whole house from your battery pack in case of power outages... ~30kw of Inverter AC is well over 200 amps of house 120 level AC ... easily an entire houses 100% full electric load running just about everything in the house at once.

Quote:
Originally Posted by thingstodo
I have a 1250 lb 'budget' for batteries.
Using that weight as your battery budget we can work backwards ...

Unless you can test and confirm better than the gross estimates.
~12V ~180Ah per ~150 Pound Battery = ~8 batteries max = ~17kwh
~17kwh from Batteries into 85% efficent Inverters = ~14.4kwh output
~14.4kwh from inverter to ~90% efficient VFD = ~12.9 kwh output
~12.9 kwh from VFD to ~90% efficient Motor = ~11.6kwh to wheels....

Unfortunately the batteries are not ideal batteries ... and you will have Peukert effects to deal with making this less than ... and you will have cold temperature effects to also deal with in the winter also making it less ... and it is not a good ideal to run 100% Do, also making it less.

Sorry ... I don't see this setup of batteries and components getting you ~15kwh to the wheels in ~40 minutes or less.

Maybe look at ways to reduce that ~15kwh ...

Or get some tested numbers on batteries that have more than ~180Ah @12V @ ~150 Pounds @the Discharge Rate you are aiming for ( not at some ~20 Hour Rate )
  Reply With Quote