REPLACING A BATTERY BOX

Rust holes in the battery box? A new aluminium replacement riveted in place could outlast the original

Defender and earlier Ninety and One Ten battery compartments are known for rusting at the underside rear corner where they’re exposed to road spray. The corrosion is usually hidden by underseal, and only visible from above when the battery is removed.

Corrosion here lets water in, and I’ve seen one so bad the battery was dropping out. Removing the battery to weld patches on is one option, but the best long-term remedy is to completely replace the battery compartment with a new aluminium box, riveted into the seat box assembly.

Replacing the battery compartment is easier with the seat box removed from the vehicle; though that incurs obvious extra work but gives the opportunity to check other potential corrosion areas and to replace body seals. The seat box assembly is bolted across the rear bulkhead behind the seats, and down the B-posts and along the steel structural sill beams, plus two bolts at the front secured to chassis brackets. The two bolts on each B-post can give trouble if they’re seized in their captive nuts, or if the nuts break free. As an alternative, the old battery box can be removed with the seat box in position by drilling the heads off the rivets that hold it in, but then it’s necessary to cut the steel box in order to work it out over the chassis crossmember.

Our Ninety’s front seats and floors had already been removed during our rebuild, so it made sense to remove a few more bolts and get the seat box assembly onto the bench to replace its rusty battery box. So, let’s get on with the job, ably carried out by development mechanic Steve Grant in the Britpart workshop.