Good luck with that. As would be the case if you ignore the brake sensors on your car and have a crash when the brakes fail entirely, you do have a warning there's a problem. Dealt with properly, it's not a safety issue. Ignore the symptoms at your own peril (chances are the system will self-destruct long before a fire erupts).
Do you really want to sacrifice the entire system for the cost of a replacement battery (a part that by design isn't going to last the life of the system any more than the brake pads in your car will last the life of the car)?
Batteries are wear items. Replace.