2002 Prius, replaced auxiliary battery

all. Long-time lurker from way back, but first time posting here. The auxiliary battery in my 2002 Prius gave up last Sunday. The car was in a parking lot and wouldn't start. The AAA service person jump started the car and tested the battery, said it was low at 12.0v, that it should ideally be at 12.8v or 12.9v, and recommended that I take it in for a test and replacement. I drove about 30 miles home after that, and while in Costco's parking lot (wanted to get gas, was down to two bars), the Triangle of Death and Check Engine lights came on, and within seconds the screen went black and the car stalled. Had to ask the friendly folks at Costco's auto dept for another jump start, drove to the gas station, filled up, restarted the engine, and got home fine. By Monday morning, pushing the power lock button in the driver-side door couldn't unlock the other doors. We jump started it a third time Wed night to park it at the closest dealership's lot, and then a fourth time yesterday to take it from that lot to another dealer that had a 12v battery in stock. Interestingly, after the fourth jump start, all the warning lights cleared. The second dealership installed a Toyota TrueStart battery, and we hope all's well now.

My two questions:
1. Is it typical for the warning lights to go away by themselves?
2. We're not 100% certain, but we think that this may have been the aux original battery. I'm the original owner, and we don't remember ever replacing the aux battery. in the almost 18 years we've had the car. It says S34B20L on the top and GS on the side. Are we likely to run into problems size-wise, the next time we need to replace the aux battery, since we don't have the battery tray kit that came with the Panasonic upgrade that we never got? The technicians who put in the TrueStart yesterday didn't seem to have a problem, and they didn't mention anything about adding a tray, but I wonder if we look around for a used tray kit from a scrapped gen 1 car for future use.

 

Thanks for responses. Not sure all's well with the new 12v battery. Twice in a week now, when I turned the ignition, the fuel gauge went down to one blinking bar, even though I knew it had a full tank. The first time, I turned it off and restarted a couple of times, and it went back up to full. The second time, I drove for about 3 mins with the one blinking bar, pulled into a parking spot, shifted into park, and the gauge returned to full, without turning off the engine. No warning lights, and haven't had any trouble starting up, or winding windows up or down, so not sure what to make of it.

Also, I have a bluetooth transmitter with a voltage reader that plugs into the cigarette lighter, and it's been reading between 11.8V to 12.6V after the car's been sitting without being driven for a couple of days. It goes up to 13.8 when the engine's running. I don't know how accurate the reader is. Am wondering if what TMR-JWAP wrote about needing several hours of driving to get it recharged to a suitable level applies to a brand-new aux battery too, and if I just have to keep driving it.

 

On a happier note, it was reading 12.4v - 12.5v this week. I don't know what could be the source of a parasitic draw, if there's one. It was on its original battery till a couple weeks ago, and there hadn't been any issues all these years. We have our 150k service appointment at a local shop this week; I'll mention it to them and ask if they can figure it out.

I remember reading about solar trickle chargers back in the day, on the Yahoo Prius owners' group. Does this forum have a favourite brand of trickle chargers?