Now laptop batteries are very expensive, however I have a slightly beefy Dell Inspiron 1525 laptop with a half year old battery that works fine.
Other than complete depletion, of which I have heard ruins the life of a battery such as this, the charging will be done by the laptop itself plugged in to at least prevent over/improper charging.
Could I use this type of battery (after regulating to 9/12v if necessary) to draw maximum 100-300mA to allow for a fairly extended battery life of one of my circuits?
I'd hate to waste it, being over a hundred dollars if I recall. Information is scarce on the web and people often just rip out the battery array inside and use them, which I assume is very hard if not impossible to maintain/recharge without the original charger.
I could of course buy some rechargables and put them in to an array, however those are costly (4-12 to have enough voltage in series) and I do not
even think (possibly in the future I will obtain) a "9V PP3 L-ion" battery exists, which could be helpful.