Cocos2d: how to add anchor points to CCSpriteBatchNode

I am doing some tests with animations in Cocos2D using sprite-sheets. The animation works ok except that the anchor-point is in the center. I need to put it in the bottom. With the code below i am not able to add an anchor-point to my sprites, after quite a few tests.

Would someone nice be able to help me with this?

-(id) init {

if((self = [super init])) {

CCSpriteBatchNode *spriteSheet = [CCSpriteBatchNode batchNodeWithFile:@"ratHammer.pvr.ccz"];
NSMutableArray *walkAnimFrames = [NSMutableArray array];
for (int i = 0; i <= 5 ; ++i) {
[walkAnimFrames addObject:[[CCSpriteFrameCache sharedSpriteFrameCache] spriteFrameByName:[NSString stringWithFormat:@"ratHammer_anim%d.png", i]]];
}

CCAnimation *walkAnim = [CCAnimation animationWithFrames:walkAnimFrames delay:0.1f];

CGSize winSize = [CCDirector sharedDirector].winSize;
self.bear = [CCSprite spriteWithSpriteFrameName:@"ratHammer_anim0.png"];
_bear.position = ccp(winSize.width/2, winSize.height/2);
self.walkAction = [CCRepeatForever actionWithAction:
[CCAnimate actionWithAnimation:walkAnim restoreOriginalFrame:NO]];
[_bear runAction:_walkAction];

}
return self;

}


You can modify the anchor point location by setting the anchorPoint property of your sprite.
The anchor-point should be given as CGPoint and is normalized to 0..1 for both axes. Per default it's at 0.5, 0.5. The lower left would be 0.0, 0.0.
[spriteSheet setAnchorPoint: ccp(0.0f, 0.0f)];