Mumbai: Nokia has warned users that 46 million batteries used in its phones could overheat and said it would replace them free of cost. Nokia is negotiating with battery maker Matsushita over who would bear the costs.

Nokia said replacing millions of batteries would have some financial impact, but Matsushita would pay part of the costs. Analysts, however, estimate the total charge on Nokia at a maximum $137 million.

"Nokia has identified that in very rare cases the Nokia-branded BL-5C batteries could potentially experience overheating initiated by a short circuit while charging, causing the battery to dislodge," the world''s top cellphone maker said in a statement.

The `BL-5C'' is Nokia''s most widely used battery, powering among others low-end 1100 series phones and multimedia handsets N70 and N91. Several manufacturers have supplied a total of more than 300 million of them for Nokia.

Nokia said about 100 such incidents had been reported globally but no serious injuries or property damage had been reported.

The batteries in question were made between December 2005 and November 2006, Nokia said, adding it is working closely with Matsushita Electric Industrial Co to investigate the problem.

Each battery would cost around $4 on an average and analysts estimate the total cost to Nokia at a maximum of 100 million euros ($137 million).

Nokia''s brand is valued at $33.7 billion, according to Interbrand, making it the world''s fifth most valued brand after Coca-Cola, Microsoft, IBM and GE.

Matsushita, meanwhile, said there had been a rare problem in the manufacturing process rather than in the design of the batteries.

"We are still in discussion with Nokia about how to divide the replacement cost," said a Matsushita spokesman.

Last year, Sony Corp was hit by hefty costs to recall 9.6 million laptop PC batteries that could catch fire from overheating.