extra 12v battery

[njamesphoto]

we have one engine battery and two leisure batterys along with a smart mains charger. If i was to add a third leisure battery and put it in parrallel with the other leisure batterys would the smart charger need anything done to it? does it need seperate connections to the extra battery? also the same goes for the alternator? the two existing leisure batterys are being replaced at the same time as the capacity has diminished and they were not deep cycle.
its a 2003 jeanneau standard spec.

 

[pvb]

No problem, just wire it in parallel with the other two. No changes needed to charger or alternator.

 

[CPD]

If you have a battery monitor fitted it will need to know about the increased capacity.

 

[njamesphoto]

i have not got a battery monitor fitted but whilst i am changing things around is it worth the £100 to fit the nasa unit? has anyone got one and are they impressed? the boat is on the marina 80% of the time on shore power with 2-3 days away max.

 

[SvenglishTommy]

You may also need to inform the charger of the extra capacity for it to increase the length of the absorption charge cycle.

 

[tobble]

If the existing bank is over 6 months old I would avoid connecting a new battery to it. as batteries age they loose capacity in the form of a lower 'peak' voltage, i.e. when charged. if this voltage is lower than the healthy 12.8 of the new one, the old ones will suck out charge until the new one is of the same voltage. this will quickly age your new battery to the same state as your existing ones. I think you could get around this by using a blocking diode, but you would then need isolated outputs from your charger... I think