Charging the 12 Volt Battery

We have a 2007 Prius and a 2015 Prius. I recently installed new 12 volt batteries in each. I wasn’t sure that these batteries were fully charged and we also don’t drive our cars long distances very often at this time. So I thought I should buy a Noco Genius to charge them from time to time. I bought the Genius5.

After receiving the Genius5, I did more reading and I have a few questions regarding charging.

Some say to remove the battery when charging in order to vent the hydrogen gas that the battery will emit. Especially with the 2007 Prius, it is not so easy to remove the battery. Do you think it is fine to charge the battery from under the hood hooked up as you would for a jump-start? I would do this outside (not in a garage) and with the trunk open if necessary to vent the gas.

In the manual for the 2007 Prius, it says “if recharging the battery installed on the vehicle, be sure to disconnect the ground cable.” With the battery in the back and difficult to access, how important is this if recharging from under the hood?

According to the manual, the 2015 Prius can be charged with 5 amps so the Genius5 should be fine. However, for the 2007 Prius the manual states a charge of 2.5 amps maximum. Now I feel I should also buy the Genius2. I don’t want to charge it incorrectly. I wonder how many people make this mistake and what the consequences are. Probably a shorter life on the battery so probably better not to charge it at all unless you won’t be using the battery for long periods.

I also have a 2011 4runner and plan on using the Genius5 to charge it from time to time. This battery would be much easier to remove, but I don’t plan on doing that unless there is a good reason.

Thanks very much for your suggestions.

Kent