# Hawker genesis-agm discharge rate vs battery life



## Quark (Jul 27, 2011)

I have built a tube chassis classic mini with a composite body, complete roller weight, sans drivetrain, is right around 800 lbs, using a motor plate with a manual transmission. The last car i built was bike engined, so i really like lightweight.

I intend to autocross ( i can charge in between runs) and drag the car, so i want to put the cheapest controller/pack together to be able to run 144v with as much amperage as the battery pack will survive. I have no real concern over the ah of the pack, so long as it discharges sufficiently . I can parallel another string of batteries if i later intend to drive on the street

Weight is a huge concern, i am looking at a warp 9, but would like the lightest/cheapest pack to start with (speed costs money, i understand this is a contradiction). 

What are the effects going to be of running 500 plus amps thru maybe a 13 or 26ah pack? Ive searched on this, nothing much on the discharge rate of these batteries, thanks for helping an ev newb.


----------



## Quark (Jul 27, 2011)

Maybe i have answered this myself, found an old post in the battery section, with a link to the hawker specs, showing current discharge rates, looks like the 13 ah will survive 500 amps for 10 seconds, and the 26 will do almost 900 amps.

Next question- what is happening at this cutoff-overheating? Will better cooling to the pack give me more headroom?


----------



## nedrapr (Mar 9, 2011)

With the Hawkers I don't recall people taking extra efforts to cool the packs. Hopefully someone can pipe in on this. If the battery box is sealed it's good to have it vented for charging. Use a brushless fan for the boxes for cooling/venting. Most of the heat is generated within the speed controller. That's where I would pay attention to the cooling. In AutoCross you aren't taking the vehicle up to it's max speed, very often, unless the course is long enough to have a straightway. You gun it from the start but then coast through many of the turns and brake to keep from going off course. I've run in quite a few AutoCross courses and it's alot of short acceleration bursts and brake type action. You don't usually get to the point where you need alot of the available power you have on board like in drag racing. But that all depends on how the course is set up. I would keep the batteries as low as you can. A 9-inch motor with a 144 volt pack for a small car would make it pretty nimble for AutoCross. My car has a 9 inch motor and 144 volts. I start in first gear and quickly shift into 2nd and leave it in 2nd most of the way through.


----------



## EVfun (Mar 14, 2010)

If you are pushing the Hawkers to the edge you will need to cool them. I've manned the fans on the old White Zombie configuration with Hawkers. Mind you, he was demanding 700 amps from the little 16 amp hour cells for a quarter mile at a time. It took several runs before cooling was needed. The heating actually made the car faster (sag less) but John didn't want to take that all the way to destruction.


----------



## Bags (Jun 20, 2010)

I ran my new-to-me car in autocross this season. What a blast! And without the roar!

However ... using Optima YTs ... (evalbum.com/120) I apparently killed the pack in less than one season, plus regular (spirited) commuting. My controller can pull 1000A+ out of these batteries with a twitch on the accelerator pedal. I guess I couldn't hear the batteries screaming.

I don't think there is much good data about battery life at high discharge rates. How often do the drag racers actually race? I probably have 20 runs at 3/4 mile each. Plus maybe 1000 miles of "spirited commuting" with limited (i.e., good) DoD. Plus two episodes of "100%" DoD.

I would be curious to hear about your experiences.


----------



## electrabishi (Mar 11, 2008)

We've got 3 hard seasons on the XE-16's. In the process there are 2 batteries blown up and 4 more that vented and maintain little capacity. So all in all we've put maybe 150 runs down the track pulling 750 amps from each of two strings. I cannot comment on longevity yet because there are still 54 of the original batteries that are still pretty stiff and ready to pull. I suppose we could drop back a couple voltage classes and still race. These Enersys batteries like to pull, and they will take a pretty quick charge too. They are truly 50C lead acid batteries. Still more power density than Thundersky LiFePO4 cells. Slightly less power density than Headway LiFePO4 cells. Once we find a set of lithiums to go in these Enersys batteries still living may wind up in motorcycles or pit bikes.

Mike



Bags said:


> I ran my new-to-me car in autocross this season. What a blast! And without the roar!
> 
> However ... using Optima YTs ... (evalbum.com/120) I apparently killed the pack in less than one season, plus regular (spirited) commuting. My controller can pull 1000A+ out of these batteries with a twitch on the accelerator pedal. I guess I couldn't hear the batteries screaming.
> 
> ...


----------

