# hymer charging system



## wub (Mar 16, 2011)

On a 1990 merc hymer 660, when on hook up, should it charge the main started battery? I thought it would, so over winter left my hook up in thinking it would keep the main battery up, but when i went to start it, it was flat? 

And whilst on batteries, mine has a lead linking the earth terminals on the leisure battery and the started battery. It looks like something the previous owner has added. But the started battery is earthed to chassis and the leisure battery has everything coming back to the earth terminal, why link them? 

Does anybody know?


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## jhelm (Feb 9, 2008)

It may be that the older version of the Electroblok did not charge the starter battery you should check the manual or ask the company. Perhaps the ground side of the leisure battery wasn't getting a good connection thus the direct link.


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## Westkirby01 (Jan 25, 2009)

I have a Hymer 670. 

I believe Hymer made the installation that way. They both share the same earth. My problem was the same as yours.

Two batteries. The leisure battery receives the charge from the electric hook up (EHU). I left the van static for some time this winter and the main battery went flat as it has a drawn from the clock. However, with no hook up at home the leisure also went flat. The radio is connected.

I always carry cables so that I can connect both batteries if one goes flat. It is an inconvenience as I have to remove a number of items that normally sit over the battery cover.

I do have solar panel to charge the leisure battery, but the winter daylight in Scotland is not long enough to overcome the discharges from the leisure battery.

Solution. 

I installed a mains line from my house that allowed EHU. Connected and charged the flat leisure battery. Connected the live from both with a heavy cable that has an on/off rocker switch. Both share the same earth. The switch cable I have extended up to the fuses in the cab and the on/off switch is easily accessible. I have put marks on the rocker, one for when I have the leisure battery connectect only. Two marks indicates both are connected. Very visible. 

Now on EHU I charge both batteries and when travelling and remaining on a site without EHU I flip the switch and the use of the leisure battery does not discharge the main cab battery.

I had the system installed/checked by a qualified auto- electrician, before anyone makes a comment. Cost £40. But if I had done it myself, about £5. But I'm not qualified and I prefer safety.

Hope this helps


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## veevee (Nov 6, 2011)

Westkirby01 said:
 

> I have a Hymer 670.
> 
> I believe Hymer made the installation that way. They both share the same earth. My problem was the same as yours.
> 
> ...


I think you'll find the the clock is an equal culprit for a continuous current draw, it is on our S670 anyway.

I just pulled the No. 2 fuse which (again on ours) feeds the radio and the clock, the current draw is almost nil now.

We have just about enough sunlight for a 70W solar panel to keep the vehicle and leisure batteries topped up with a trickle charge, also fitted one of those relays which transfers charge from the leisure battery to the vehicle battery once the leisure battery is above a certain voltage.

This system including the removal of the fuse worked very well over the entire winter, the batteries are now in better condition than when we bought the MH in November, and haven't used either a EHU or taken the MH out for camping yet.


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