Help with MOV Design Guidelines - Convert to 240VAC from 200VAC

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dwl

371 posts

Ultimate Geek

#190723 10-Jan-2016 15:01

I have very recently purchased a Nissan Leaf. The car has an on-board charger (100-240V rated) and uses a EVSE (Electric Vehicle Supply Equipment) which connects the car to the household supply. The EVSE signals to the car the available capacity (e.g. 8A or 15A) and passes through the mains power. The dealer has supplied a NZ certified EVSE which charges at 7A but I am trying to work out whether the Nissan Japanese unit which is rated for 200V 15A might be safe to use as charge times are an issue.

There is a separate thread Nissan Leaf and EV Imports - any experience with them? which has some detail with caution about using these 200V devices in NZ and questioning the modifications that are done by some dealers. The Gen1 cars had a different unit and there is a linked post in a Sri Lanka forum what shows how to change out the transformer.

I have a Gen2 which has a different EVSE with the board potted:

Many of the components seem rated for 250V although the transformer would be over voltage. There are 12V relays that might then get 14+V but these have an over voltage allowance on the coil of +170% so not too worried there. However, there seem to be MOVs that are confusing to me. They have this label:

From what I tell from datasheets K175 this means 175V operation and the next model up may be 230V so perhaps Panasonic choosing a 175V for 200V operation makes sense? On one datasheet the K175 has a max clamping voltage of 455V while the K230 is 595V. Both seem to have headroom to 240VAC peak of 339V but is the K175 too marginal for NZ operation?

These EVSEs are quite expensive and the ones that come with the car are surplus so would be good to use them but with the potting I don't think components here can be modified. Any suggestions or comments welcomed and appreciated. Thanks.

Aredwood

3885 posts

Uber Geek

#1467140 10-Jan-2016 18:18

The dealer probably supplied a 7Amp charger so they won't have to deal with people overloading their household wiring. Either due to other loads or due to flaky wiring.

Do you have a 15Amp power socket installed? As a few people have probably just cut off the Jap plug and wired on a 10A NZ plug. This would appear to work as alot of houses have 15A or 20A circuit breakers on power point circuits. So the circuit breaker won't trip despite the power point being 50% overloaded.

As for the MOV check what voltage it will drop out at after a spike has passed. As if the drop out voltage is less than Mains. Then it would be fine until the first spike, where it will stay conducting even after the spike has gone.

dwl

371 posts

Ultimate Geek

#1467222 10-Jan-2016 19:55

Aredwood: The dealer probably supplied a 7Amp charger so they won't have to deal with people overloading their household wiring. Either due to other loads or due to flaky wiring.

Do you have a 15Amp power socket installed? As a few people have probably just cut off the Jap plug and wired on a 10A NZ plug. This would appear to work as alot of houses have 15A or 20A circuit breakers on power point circuits. So the circuit breaker won't trip despite the power point being 50% overloaded.

As for the MOV check what voltage it will drop out at after a spike has passed. As if the drop out voltage is less than Mains. Then it would be fine until the first spike, where it will stay conducting even after the spike has gone.

The 8A unit (which charges at about 7.2A) is the safe answer with standard plug. I would install a 16A outlet with the IEC connector - there is growing agreement that this caravan style round plug (see EV group poll) is the best approach for > 10A.

The MOV stuff is confusing. If I look at the spec sheet at SIOV metal oxide varistors it seems to be saying:

S10K175 - P/N B72210S0171K101 - Vrms=175V, Vv(1mA)=270V, Vc(max)=455V
S10K230 - P/N B72210S0231K101 - Vrms=230V, Vv(1mA)=360V, Vc(max)=595V

If I understand correctly, the Vv is the start of conduction so I don't understand why a 175V rated MOV might be used on a 200V system (which should have crest voltage of 283V) if conduction starts at 270V. Have I got this right? If only they had used 230V that would be one problem out the way :-(

Unfortunately the potting is far enough up the components that no lead is showing so not possible to work out the circuit but I assume these MOVs see the full mains voltage.

Thanks for the feedback. Any further insights welcomed.