#152091  by freddagg
 Mon Jun 10, 2019 5:36 pm
Hi all.
Can anyone advise what the relay in the picture does? It is a standard automotive type. Particularly the brown/green wire.

Initially I thought it was the habitation relay but after testing, it appears to be built into the main power module. I think it has something to do with the main power battery charging but would like to know for sure as I'm installing a DC-DC charger and want to integrate it correctly.

Abbey Spectrum 2004 Wiring.PNG
 #152097  by mattn
 Mon Jun 10, 2019 10:44 pm
Looks like its there to charge the house battery from the car when the engine is running

When the fridge circuit is off (engine not running), the relay directs the cars 12V feed to the ESM 2004 via the Brown/Green wire. When energized via the fridge circuit (switched on by the running engine), the relay connects the car 12V to the house battery (for charging), which is connected to the ESM 2004 via the brown/blue wire.

I presume the ESM 2004 provides the habitation relays, and its likely it also directs power from the car to the house circuits if the house battery is absent or flat.

As your installing a DC-DC charger, you certainly want to remove this relay from the system. The DC-DC charger has low voltage disconnect - hopefully around 12.6V, so you can simple replace the relay with the DC-DC Charger. If you want to keep the relay so the tug can power the house (in even of flat house battery), install the DC-DC charger so its powered from the battery side of the relay and the existing wire from teh relay to the battery goes into the Dc Dc charger output.

You do not want to leave the relay as is and install the DC-DC charger in parallel.
 #152098  by freddagg
 Mon Jun 10, 2019 11:30 pm
Thanks very much for that helpful reply. I think you are bang on.

Looks like once the relay is removed, the brown/green can be used as the load output from the solar MPPT which should now show the correct load.

Currently it is connected to the brown/blue so I didnt want to use the builtin charger for fear of backfeeding and damage to the MPPT.
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