jmdirt said:
If you keep it plugged in for a few days and it still says 90%, you could try taking to someone who will "deep" charge it for you, and then use the float charger to keep it there. I used a regular charger on a low battery one time and it still didn't get to 13 volts. I took it to the moto shop and they used their "sonic" charger, and I got two more years out of it after that.
Check with local auto parts stores, I think that O' Reilly might offer this service for free (in hopes that when you buy a new one, you will remember them).
This had me a bit concerned, if the floater charger won't charge a car battery to 100% I'm not sure what good it will do mom. (And, as Jay had mentioned earlier, I don't trust my elderly parents around a floater charger that is hooked up to a live battery non-stop even if the battery is at only 90%.)
So I went back to the store and exchanged it for this charger (slightly more pricey), currently the indicator is saying the battery is bad and it's trying to de-sulfate it. And if the de-sulfating doesn't work the battery needs to be taken to an actual professional.
So yeah, that's how well my latest DIY project is going. Thanks for your help, nonetheless, jmd!
PS - Apparently you're supposed to ground these chargers to a metallic part of the chassis, not the negative terminal of the battery. YMMV, I suppose.