Voltage sensing relay trouble

[Kidnmeiieh 0]

Hi guys,

New to this forum...so any help will be appreciated

 

I am having trouble with my house batteries when running off the alternator. I am not getting a charge.

I have a Monterey 330 2008 with 2 5.7 GXi. There is a power distribution set of relays. From what I can tell, one relay for port motor, one relay for starboard engine, one relay for house batteries and one voltage sensing relay (VSR 710-300A) connected to the starboard engine and the other side connected to house. The whole setup is factory and are manufactured by BET. Each relay including the VSR has a switch on top Off-Auto-On.

My trouble shooting has narrowed; On shore power everthing charges ok 13.4 to 14.5vdc, from generator all seems ok also (same readings). Under engine power I am getting full charge to starboard batteries but the house are going down fast...12vdc to 11vdc in about 3 hours...No charge happening. All relays are on Auto including the VSR. If I swith the VSR to ON, it gets a charge from the alternator.

 

Context:

New boat and had same problem from day one back in may 2013...The marina rep replaced all 4 batteries.

Two different mechanics said that the switch on the VSR should be ON and not on Auto...The manufacturers handbook says the opposite...it should be on Auto.

 

When I check the voltage on the VSR when it is switched to ON I am getting identical voltages on both legs (House and Starboard)...It seems to bridge the batteries in parallel. Good if I am in trouble and I need the extra power to start engine, however, I am concerned that under normal conditions, I am potentially going to overcharge my starboard battery or kill it if I am at anchor because of the paralleling and drain form the House power consumption...

 

Dilema, I communicated with BET in UK and they said the 710-300A is discontinued and replaced by a 720-MDVSO which retails for about 350$ US...Yikes!!! So, before I make that move, does anyone have any experience with this type of problem. Also, do I really need a 500amp VSR when my alternator will never pump more than 70Amps even If I am running off of Shore or generator It will never even come close to the rated VSR amps. BET has a 125Amp version with very similar specs on everything else and sells for only 199$ on amazon.

 

Urgent Advice would really be helpfull as we are preparing a two week trip to lake champlain and we plan on running off batteries for most of our nights...

 

Many thanks in advance!!!

Fred