SMB on Ford 2019: engine battery disconnect size/features

[Lyngby]

Hi all, we have a Sportsmobile built on a 2019 Ford Transit. It's great, but one persistent problem has been a possible "parasitic load" on the Ford engine battery that causes the battery to be dead after sitting in the driveway for a week or two. Our engine battery is AGM rated at 720 CCA.

To deal with this, 6 months ago we had an engine battery disconnect switch installed by a local Ford dealership service department. Although I asked them to install a Blue Sea switch, they instead installed a cheap one (https://www.autozone.com/ignition/ki...tch/422687_0_0). It worked fine for awhile -- we switch it off when we get home from a trip, and it has kept our engine battery from draining while the van sits unused for a few days or weeks.

But this week the disconnect switch quit working -- that is, turning the switch to "OFF" doesn't disconnect the engine. Weird and worrisome, since it might also fail to connect someday, leaving us stranded in the boonies somewhere. I'm also concerned this indicates the switch is not adequate for the load; it appears the cheap switch is only rated at 700 amps maximum, 20 less than our battery's CCA rating (thanks, Ford dealership ). Maybe this could even be a fire hazard?

Anyway, I'm planning to buy a better quality switch and have it installed by a marine electronics specialist. I'm thinking of this "Blue Sea" e-series model: https://www.bluesea.com/products/900...Battery_Switch.

Anyone have experience with this cutoff switch, with engine battery disconnect switches in general for the Ford Transit, or this one in particular? (I have already reviewed the other thread on this topic, ) and it didn't help me much.)

Also, might the cutoff switch also serve as a theft deterrent if we got one with a removable knob? Blue Sea doesn't sell an e-series switch with a removable knob, but they do sell a lower-rated m-series switch with a removable key: https://www.bluesea.com/products/600...with_Key_-_Red. However I would worry that its amperage rating (300A continuous, 500A intermittent, 900A cranking) might be a bit low.

Thanks much for your thoughts, SMB friends!

[mgmetalworks]

paging Scalf77...

...Scalf77, please report to the battery switching thread...

[JWA]

IMHO even a battery disconnect switch is not a huge deterrent to thieves, either those just breaking in to steal stuff or those intent on taking the whole van. So many use sort of disconnect the thieves have learned to check for them during their first entry.

[Scalf77]

I take it we are talking about disconnecting the van battery from the van electrical system. The 720 CCA rating would be important for fusing information ,specifically for AIC rating. It does not really have a direct correlation on what size switch you would choose. The major factors for that choice would be the actual loads, in this case the largest being the starter. I am not sure what the starter is rated at, by I expect to be below the 900 amp (30 Sec) cranking spec of Bluesea switch. I suspect that you are also OK on 300 amp continuous rating. What is your Alternator rating?

The other key thing to look at is the size of wire in the circuit. The switch requires 4/0 wires to meet their specs, you could contact Bluesea for their derated values. But in general the cable is most likely the limiting factor in this circuit.

When using this switch i wouldn't expect I high level of arcing during the transition, do to low current at the time.

I have not seen how sportsmobile connects to the Transit electrical system, but I would focus more in that area. Ford provides various level of protection for van battery. What other kind of equipment was added van, stereo , etc.

-greg