Starting Engine Whilst On Ehu

[ojibway]

When I had my first van - a 2003 Rapido - I started the engine a couple of times whilst still hooked up and there was a nasty "KLIK KLIK" sound so I immediately turned the engine off.

 

[eddie]

My Hymer wont start with the EHU plugged in. I don't know if it was built that way, but there is a hook up warning light on the interior control panel. Whilst that's lit, no starto.

That's to stop you driving off with the lead in, causing damage.

We have a 6kw genny built in, which we often run whilst driving to power the roof A/C when driving when on the continent. The multi stage mains charger bows down to the alternator DC power

 

[TERRY&PAULINE]

Easy, just switch the mains charger off before you start the van, don't think the hook up makes a difference

 

[jockaneezer]

My panel beeps if the ehu is plugged in and you start the engine, but, and it's an important but, only if the supply is switched on. Found out the hard way

 

[Scattycat]

Not knowing much about these things, but when we picked up our first mh the guy doing the, run through, of all the vans components etc made a big thing of explaining that running the engine when plugged into the mains will likely cause the van's mains system to go pop. Also the repairs would not be covered by the warrenty.

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[Autowbars]

Simple, if is says don't do it, DONT DO IT

 

[MR. FUSION]

Look, lets look at this carefully and not perpetuate more internet myths, or in layman's terms, bollocks!

Built in charger is switched on. It applies voltage to your batteries.
You start your engine, the alternator applies voltage to your batteries.
Now, one of these, probably the alternator, will supply more voltage than the other. The provider of the lower voltage will cease to provide charge.
There is no conflict, sparks will not fly. 240v AC will NOT come into contact with your 12 volt system!

How many of you worry about disconnecting your solar before you start your van or connect the EHU lead?

My elektroblock is supplying a 2 amp float charge to the cab battery (new versions of elektrobloks supply 2.5 amps) whilst on EHU. You may think it's OK to put extra amps through the engine ECU but I dont, which is why I follow the manual and disconnect the EHU before starting the engine. As for solar, one of the reasons I am buying the correct solar adaptor for the elektroblock is that it protects the cab battery from a solar overcharge!!! It's not an internet myth it's common sense, and I would encourage everybody to follow what it says in the manual!!

 

[tonyidle]

My elektroblock is supplying a 2 amp float charge to the cab battery (new versions of elektrobloks supply 2.5 amps) whilst on EHU. You may think it's OK to put extra amps through the engine ECU but I dont, which is why I follow the manual and disconnect the EHU before starting the engine. As for solar, one of the reasons I am buying the correct solar adaptor for the elektroblock is that it protects the cab battery from a solar overcharge!!! It's not an internet myth it's common sense, and I would encourage everybody to follow what it says in the manual!!

See jonandshell and eddievanbitz. No more amps go anywhere no matter how many regulated supplies attempt to charge the battery. The advice is, I suspect, to prevent moving off with the EHU tether still in place.

 

[MR. FUSION]

I will expect all this to be recorded in the MHF classifieds, when the time comes.
'I ignored everything it said in the manual but rest assured my motorhome has been lovingly cared for'

 

[Teuchter]

In case you drive away with the hook up post

Been there - done that!!

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[movan]

My Hymer wont start with the EHU plugged in. I don't know if it was built that way, but there is a hook up warning light on the interior control panel. Whilst that's lit, no starto.

Likewise my Burstner Tootles. I guess there is a sensible reason for that being the case.

 

[Nirvanauk]

@movan Joy could you change your avatar for something prettier please? It's scary!

 

[movan]

Lol. Just for you when i arrive home from Meet will do thst. Does your lovely little dog like cats .. I may do one just for him/her.

 

[Tootles]

@movan Joy could you change your avatar for something prettier please? It's scary!

Joy decided to have that poor little chimplette as her AVATAR, in order to highlight the plight of all primates in this world, suffering climate change, degradation of their habitat, the vicious slashing away of the rain forests, and the callous way we, as humans, treat our closest relations....

Also, it was the very first selfie she ever did.

 

[Nirvanauk]

Lol. Just for you when i arrive home from Meet will do thst. Does your lovely little dog like cats .. I may do one just for him/her.

Lovely little dog is now 2 and a real teenager. Surprisingly we only have one cat in the village and the dog has never seen her so doesn't know what a cat is so don't scare her as we are about to set of for Italy and I don't want her stressed.lol!

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[Tootles]

Surprisingly we only have one cat in the village

Not surprising really. You never see a cat wandering uneaten around Bradford. Maybe the penchant for feline fur is traveling North??

 

[TheCaller]

From the discussion above, there would appear to be three potential reasons why starting the engine might be a bad idea while on EHU.

1. Driving off with the lead still connected.
2. Causing damage to the on-board charger.
3. Causing damage to the base vehicle electrical system

The first one is obvious. This is on a par with leaving the step out & a warning buzzer would seem to be the obvious answer. It’s the driving off that causes the damage, not starting the engine, so preventing the engine from starting seems to be overkill. In the OP’s case, the engine isn’t prevented from starting, he is just warned against doing it. You would expect the warning to say ‘Don’t drive off with the EHU connected’, rather than ‘Don’t start the engine’.

The second one is the case raised by @Gromett . If you have a control system where you have to manually direct the charger output to one battery or the other, then this becomes a possibility if the charger is poorly protected from overload. Given a flat, or nearly flat starter battery, trying to start the engine would produce a near short circuit across the charger output. If the charger is not protected from overload or short circuit & if you hold the key in the start position for any length of time, damage could well occur.

Could the charger damage the base vehicle electronics? Some multi-stage chargers, at certain stages, could produce a higher output voltage than the alternator. Would this damage sensitive electronics? I honestly don’t know, but if it was the case, the warning in the OP’s manual is the wrong one – the damage would be done by turning on the ignition key – there would be no need to start the engine.

So the warning only seems appropriate to the second situation. I thought that continental converters generally fitted control systems that supplied a current restricted top-up charge to the starter battery – an incorporated equivalent to the VanBitz Battery Master. Does the Rapido have a manual change-over switch?

 

[shawn&emma]

I don't need to, because I never forget But if your ok at a bit of wiring buy a male and female hook up connector and make up a lead just long enough to loop through the stearing wheel and clip together. Keep it with your main lead, plug into site and put the shorty around steering wheel. Then it's there if you go to drive of. Connectors very cheap. Or just by a spare male connector and put it on the drivers floor when you plug in.

If you still forget at least you'll have a replacement socket to hand.

 

[Rapphil]

Does all the above also apply to jump starting the engine battery? I'm sure I was told this was not good idea as would have similar affect.

 

[Allanm]

I have a battery charger and on it, there is a sticker saying not to start the engine with the charger connected as it may blow the output fuse
So, I connected it to my ride on mower battery and after an hour or do, started the engine
Sure enough, it blew the output fuse. Luckily, there are spare output fuses in the box, because they know you will do what I just did!
Oh, and if I start the van engine with EHU connected, a get a very loud warning beeping.

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[scotjimland]

Always found it better driving away unplugged..

only tried it once still plugged in, the cable took a sapling tree out by the roots.. before ripping the cable off the RV

you only do that once..

 

[Enword]

I wish hook-up plugs would disconnect more easily. I'm sick of carrying my bungalow the length of the street every time it follows me out of the drive (which is looking very scuffed now).

Best thing is get one of these, your on permanent hookup so you can drive off & the lead comes with you, Oh & keep it running day & night

 

[madgeD]

We had to once so we could get the van to a garage for a new battery I was on tender hooks in case it stalled when we came to a halt! just got there it stopped just before the garage boy were we lucky.

 

[Lenny HB]

In case you drive away with the hook up post

Been there done that - on the drive at home.
Thank goodness for solar never plug it in now.

 

[iandsm]

I have read all of the various options and have come to the conclusion that I dont give a monkey's about the technical issues and that if my manual says don't do it I am perfectly happy not to.

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[jockaneezer]

Whatever you do, if plugged in, don't set off backwards as you'll be entering reverse polarity territory.

 

[MR. FUSION]

Whatever you do, if plugged in, don't set off backwards as you'll be entering reverse polarity territory.

Yes the fridge will turn into an oven

 

[Larby]

Best thing is get one of these, your on permanent hookup so you can drive off & the lead comes with you, Oh & keep it running day & night View attachment 103142

And you can run your coffee maker, hair dryer, kettle, iron, 50" flat screen TV etc. and not an inverter or leisure battery in sight!

 

[Reallyretired]

If I start, or attempt to start my Mercedes Rapido on ehu or immediatly after disconnection it sometimes comes up with a string of errors. ESR fault, ABS fault and of course it won't start. Aftr a few minutes these errors disappear and all is well. The problem can be avoided by turning on the headlights before starting.
I wondered if the higher than expected battery voltage may cause an ecu problem, though it doesn't seem to happen with solar charging.