Last time I replaced a 12 volt battery on my Subaru, lost several settings, and it was a PITA. Various online sources tout memory savers, while other tout jumper cables. Looks like apples/oranges to me, but I already have jumpers... Suggestions?
If we're talking about the Prius; use another car and the jump point under the hood - unless you have another good freestanding battery to hook up to while messing round in the trunk.
@Stevewoods hasn't been a Prius driver in years, he's just here for the community. He also needlessly/senselessly kills yellow jackets and other bees every Summer despite them wanting to avoid him and do no harm.
I find Toyotas and definitely my Prius v have little or no problems with a 12v disconnect. I don't lose window or radio settings and my engine's throttle body is clean enough that there is no noticeable change as the engine automatically relearns fuel mixtures. I don't like to use jumper cables on modern ecu intensive vehicles and especially not on a hybrid. The 12v outlet memory savers won't work because those circuits are off when the car is off. However I have used a 4 amp hour $25 alarm battery with 18 awg electronics jumpers on some cars. I have also used the same battery to ready a hybrid with a disconnected aux battery. I expect the obd2 memory savers are probably the safest because that circuit stays hot and it is virtually fool proof from an ecu safety standpoint. As long as the ecu and lighting loads are off. Which means waiting for those loads to sleep first. But for me, its out with the old and in with the new. Even if I had a Subaru that needed its windows and radio reset. No memory savers needed.
Last year, I replaced the 12-volt in our 2017 Prius and used this contraption....just plugs into the OBD2 and gets power from a USB charger. I didn't notice any settings or changes in the car afterwards. Links is not working for me....search Amazon for this USB Powered Vehicle OBD II Connector Memory Saver with Buzzer, Car ECU Emergency Power Supply Cable, Automotive Battery Replacement/Disconnect Tool, Save Settings During Battery Removal
IMHO; those 9V ones are the safest and most stupid-proof to use. Don't know if those clamp-on ones has reverse polarity protection built-in. 9V is more than enough to retain memory settings.
If I was concerned about memory saving I might get this one or similar They claim reverse polarity protection, 7 amp capability (externally fused at 3 amps) and voltage/current monitoring. Which allows plenty of ecu headroom. It could have other applications such as parasitic draw testing.
