OBC AC Input fuses: are they ubuiquitous?
Posted: Sat Mar 07, 2026 6:17 pm
A question for those who may know: Does the OEM OBC that you're most familiar with have AC input lines fused inside the OBC?
The reason this question arose is that I am active in a niche community of Toyota RAV4 EV (Gen2, 2012-2014) owners, a vehicle with a Tesla powertrain based on pre-production Model S parts. Though few Model S parts interchange directly with the RAV4 EV, one part that is identical is the OBC, which was used in the 2012-2013 Model S only, plus all the first generation Superchargers, which ran several of these 10kw OBCs in parallel. Wiki article
This OBC is large, heavy, and has at least two common failure modes. The DIY-repairable failure mode is its propensity to blow one of the two AC input fuses. Tesla spec'd semiconductor fuses (ie very fast reacting), 50A for a circuit that should never draw more than 40A. The de-rate is probably due to their hot, non-ventilated location, but still . . . in both the early Model S and the RAV4 EV, they fail frequently. I've replaced this fuse three times in 130k miles/14 years in my car, and we have members regularly post that their OBC has failed, and its about 70% one of these fuses.
On this OBC, the fuses are located inside the OBC. There is no authorized service procedure to access them, and whilst under warranty Tesla replaced the entire OBC when a fuse failed. Outside of warranty, we replace the fuse(s), of course.
Do other mfgrs locate their OBCs' AC input fuses internal to the OBC?
The reason this question arose is that I am active in a niche community of Toyota RAV4 EV (Gen2, 2012-2014) owners, a vehicle with a Tesla powertrain based on pre-production Model S parts. Though few Model S parts interchange directly with the RAV4 EV, one part that is identical is the OBC, which was used in the 2012-2013 Model S only, plus all the first generation Superchargers, which ran several of these 10kw OBCs in parallel. Wiki article
This OBC is large, heavy, and has at least two common failure modes. The DIY-repairable failure mode is its propensity to blow one of the two AC input fuses. Tesla spec'd semiconductor fuses (ie very fast reacting), 50A for a circuit that should never draw more than 40A. The de-rate is probably due to their hot, non-ventilated location, but still . . . in both the early Model S and the RAV4 EV, they fail frequently. I've replaced this fuse three times in 130k miles/14 years in my car, and we have members regularly post that their OBC has failed, and its about 70% one of these fuses.
On this OBC, the fuses are located inside the OBC. There is no authorized service procedure to access them, and whilst under warranty Tesla replaced the entire OBC when a fuse failed. Outside of warranty, we replace the fuse(s), of course.
Do other mfgrs locate their OBCs' AC input fuses internal to the OBC?