Recharge batteries individually or parallel ?

I have an ER1 robot from Evolution.com.
I have 2 additional batteries for it. I plan to hook them all up in parallel to provide longer lasting power.
1) With regards to recharging them, should I recharge them all hooked together, or individually ? 2) Assuming they all drain equally, would the recharge time be 3 times that for one ?
Does it make any difference ?
Thanks !
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If all three batteries are identical you could get away with it. The best way, however, is to charge each one individually and isolate them from each other with diodes. Your charger would need to supply the charging current for all three batteries. If you supply only the original charging current the charge will take longer. ( Three times is approximate) Tom

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Thanks for the info !
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Lead-acid yes, NiCD probably, LI-ion ABSOLUTELY NOT.
Read this about battery charger design:
http://www.national.com/appinfo/power/files/f19.pdf
                John Nagle
jc-Atl wrote:

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Thanks for the PDF link !
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