My 2016 Toyota RAV4 hybrid has a strange location for the 12V battery. Usually, the battery is installed under the hood. Well, in this case, the battery is installed under the trunk. This is true although there's plenty of space under the hood. Although the car is a hybrid (and thus there's plenty of equipment under the hood), it has a really large hood, and because the car is a hybrid the 12V battery is quite small, so I believe space is not an issue here.
What is the reason for such a strange location? I understand that this is not the only car model having battery under the trunk.
I can identify several drawbacks in this arrangement:
- The cables from the trunk to under the hood must be quite big. Most of the power is consumed under the hood (and even if the power is consumed in the rear like for the rear window heater, the fuse is still under the hood), and the current can be as big as 100A if all electric heaters of the car are on. Thick and long cables have voltage loss, weigh a lot and cost much. For non-hybrid cars, the cables must be think enough to crank the engine even when cold.
- Storage space is wasted in the trunk. The battery compartment could be used to store some small items.
- A separate jumper terminal is needed under the hood, because the electric rear door doesn't open if needing to jump. There is such a jumper terminal in a fuse box, but it could be eliminated if the battery was under the hood.
- The trunk needs to be emptied in order to change the battery or to test its cold cranking amps performance. Only an open circuit voltage test can perhaps be performed without emptying the trunk.