Artisan Power RB-4040-N Polycom / SpectraLink Kirk 3040, 4020, 4040, & 4080. Replacement Battery. 730 mAh $21.00 Battery works for Kirk 3040, Kirk 4020, Kirk 4040, and Kirk 4080 phones. Battery replaces OEM battery number 84743411. The 730 mAh capacity rating is 22% higher than the OEM's 600 mAh capacity rating. Add to Cart Compare