caravan wireing soleniod spyke

zacc,
I don't believe there will be any spike. I bought a solenoid charging kit for my camper from Derek of Affordable Batteries and there was no spike protection included. The solenoid activates when the charging system reaches 14 v I think it it and turns off when the primary vehicle battery drops below a certain voltage.

Pretty sure he advsertises on this site his web address is www.sidewinder.com.au. The kit is simple to connect and reasonably priced if you haven't already got one.

I also bought his dual battery set up kit again I don't believe there was any spike protection as I don't believe one is needed due to the way the system works. I'm sure Derek wil advise you anyway I've always found him to be very obliging and happy to give advice.

Your starter motor draws 200 amps and is a very inductive load. When this current is interrupted there will be a massive back-emf surge.

I have no idea why people think that connecting/disconnecting two 12 volt batteries will cause a surge anywhere near that big.

Just another example of Battery Isolator marketers trying to come with "you must buy this one" features.