Suspected split charge not working on 1999 SO 32.2

[robheath]

Hi

My domestic battery is not charging when the engine runs, but the engine start battery does charge. However both batteries charge when using the twin battery charger that is connected to shore power.

I think the split charge relay, or associated circuits, may have failed. It is part number Hella 12v 4RA 003 437-06.

Does anyone know please:
1) The current equivalent replacement?
2) Is there any intelligence is the split charge, or does it simply parallel the batteries when the engine is running?
3) Any other tips?

Regards Rob

[rene460]

Hi Rob,

It is possible that your relay contacts have failed, or that the wiring to the coil or even the coil itself has failed.  A few simple checks with a multimeter should enable a diagnosis. 

I have checked the circuit diagram for my SO30i many times and the relay seems just to be a switch to parallel the batteries when the engine is running, a remarkably simple concept to reserve one battery for engine starting, but devoid of any real intelligence.  I would suspect that a good automotive headlight relay would be a suitable replacement.  It needs a high contact current rating to handle the charging current.  If yours is a plug in type, you want a plug in replacement to save making any wiring connections.  Hella should be able to tell you where to buy a direct replacement or advise you on a type with heavier contact rating.

I suspect that a voltage sensitive relay (VSR) which makes the connection based on a voltage could potentially be a better option, but the suppliers web sites are remarkably obscure about how they operate (switching voltage etc), especially the dual sensing type.  The example circuits never seem to be quite what I want.

Of course any system that charges one battery first then the other, potentially never charges the second (house battery) if you only use the engine for a short time before sailing, so simple parallel connection may be the best solution, combined with a good charge at the marina on shore power.

I have a solar panel connected to charge the house battery so it is always good when I get to the boat, but potentially leaves the engine battery flat after a long absence, as our marina rules prohibit leaving shore power connected when you are away from the boat.

rene460

[aussieodyssey]

Hi Rob
 The relay you need has a 60 amp rating according to the hella cataloge i looked up . It is just a relay nothing special apart from the high current it can handle .The relay just plugs in so it shouldn't be hard to change


 Regards Greg