SPS1 portable speaker system does not keep 12V battery charged even with AC adapter plugged in continuosly. Once the battery goes dead after about 2 - 3 hours, it never charges back up to a usable state even when plugged in and left off overnight. However, I can charge it with an external 12V battery charger, and the battery will last another 2 - 3 hours. I bought a new battery thinking that was the problem, but the problem is still there. When purchased new, I could run the system continuously beyond 5- 6 hours and never had a problem.
Borrow a multimeter and check the voltage (and current if you can) going to the battery while the unit is turned off. It should still be charging the battery if it's still plugged into the wall socket. If it is not getting about 13 volts, it's not going to charge the battery. If that's the case, then there's something wrong with the transformer, or another part of the charging circuit. The downside is you can't use the unit without the battery being connected. If the unit still works and sounds good even though it's not charging the battery, then just put the battery on a separate charger every week or so.(I use the SPS1 for my computer and love it!) Good luck with it. H.
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