joining up my two bats, KAD44

[simonfraser]

i have two Wilco CA 31DC 12 volt 105Ah 800EN

separate at the moment, always join them up with the battery switch when starting and when using the boat.

the KAD is sensitive to low voltage, during starting the two bats above drop to 12.0V
it stands to reason the voltage is going to be more reliable using both bats ?

so why not just join them up with a suitable wire 24/7

risk is running them both down vs the KAD not receiving sufficient voltage and damaging the ECU

comments pls

 

[Portofino]

Sounds like you need a new "engine " bat and or a new domestic bat -

or set of the above ?

Idea generally is keep ENG and DOM seperate

Reasoning is - via a split diode your charging systems ( alternator (s) + bat charger ) prioritise the ENG over the DOM,s
Thus you Allways have enought juice to fire up , in the ENG bank
So you can never run down the ENG -eg leave a heavey DOM load on by accident ---cos they are NOT connected
However most 1/2decent boats fit at the dash a cross over or parallel switch -idea is that what ever reason the ENG bats cannot fire up -you can temporarily nick a bit from the DOMs to get off .

Linking the two ENG +DOM's in an allready split system ( by the sounds of things ?? ) --- is madness
If you are finding you need to use the cross over / pararell --frequently then

1- your starter ENG bats are knackered
2- your charger is Knackered *

Address one or both of the above .

* chargers are not like light bulbs ,they don,t go pop -Making it obvious they are knackered instead -they slowly decay with time -what was pumping out say 40 W /hr brand new is now 20 Yrs on only giving out 3-5 W /h ---- hence knock on effect on what seems bat power to start engines -now having to rely on cross over /pararell -robbing juice from DOM,s

 

[robrennie]

Connecting your two batteries in parallel with your engines running may not be a good idea.

The sensing bits on the Alternators will get confused by the different voltages, although in reality they will probably just read the higher voltage.

This may have the effect of not charging the weaker battery.

Perfectly OK to connect to start, but disconnect when running.

If you are in doubts about one of them, simply connect the batteries to the opposite engine - and see if problem persists