We have a Mercedes Sprinter Campervan with 2 house batteries with their own 240v smart chargers. 1 is also connected through a VSR to the truck battery & also to the 3 way fridge whilst travelling. Works well & we also have 80w portable solar panels)
When connecting to 240v power can I still have the engine running or will it damage the alternator or smart charger?.
The reason for asking is that if the truck battery remains above 12.8v the 240v charger through the VSR will keep it charged up but if I forget to change the fridge over to 240v or gas before turning the engine off the voltage will drop bellow 12.8v & the VSR will disconnect & not reconnect until the truck battery has 13.5v.
If I can do this all 3 batteries can be kept on float charge at home without the need for another charger for the truck battery.
Hi David Running the car engine with 240V charging the van batteries will not be a problem & some charge MAY also go into the crank battery. However they may not all function ALL the time as each will have slightly different settings for the multi stage charging While the batteries are in a low SOC all will put something in, but as they approach full charge some will cease to charge until/unless the battery voltage drops
The VSR should automatically isolate the fridge from BOTH the crank & hose batteries AS SOON AS the engine is switched OFF. The fridge should not pull either battery down If that is not happening, either or both your fridge & the VSR have not been wired correctly!
If you wish to keep the crank battery fully charged from the house battery charger at home you will need ensure that:
[a]: the fridge & VSR are correctly wired,
A separate switchable charging circuit from the house charger/ batteries the crank battery
But you would need to ensure it is disconnected when not using the chargers as it could end up flat or in low state of charge
That could be done with an EXTRA VSR depending on how the fridge & 12v to house battery from the crank battery are wired
-- Edited by oldtrack123 on Thursday 25th of February 2016 04:20:57 PM
The VSR is only wired between the truck battery & house battery with the fridge wired to the house battery so that if the engine is turned off it will disconnect the truck battery at 12.8v but the fridge will still draw down the house battery until turned onto 240v or gas. This has not been a problem to me as it may only be 1-15 minutes before I remember but the truck battery may be isolated from the VSR by then & not be able to receive any charge from the 240v charger.
Your advice that connecting to 240v whilst the engine is running will not cause a problem is the answer I was hoping for so now I only have to train my old brain to not turn the engine off before I connect the 240v cord & all batteries will be receiving a charge or on float.
