Battery charger for 2 x starter and domestic bank advice please?

[fergycool]

My twin starter battery boat has got a small battery charger for the single(105ah) domestic battery but not the starter batteries.

When not in use the boat is plugged in to shore power.

I want to buy a charger so that all three batteries are being charged.

Reasoning being that it is better for the batteries and the automatic stern bilge pump is attached to one of the starter batteries.

The existing charger is a small CTEK one.

Since the boat is always plugged in I think smaller chargers are fine as slower charging is always better for the batteries right!

My options are:

(1) buy another one of these and add a switch so that I can manually alternate between the two starter batteries.
(2) Buy a larger dual battery charger and attach to the two starters.
(3) remove the existing charger and get one of the ones that will do triple banks.

Ideally I'd do option 3, especially since I would like to double up on the batteries on the domestic bank at some point in the future. However, that's a lot more money! I could add two more of the CTEK smart chargers for less than half the price of the three battery bank chargers. Although that requires some extra 240v sockets.

I'd like some advice on what would be the best option. I'm sure there's something that this new and naive boat owner has not thought about!

Many thanks.
Chris

 

[halcyon]

I'd like some advice on what would be the best option. I'm sure there's something that this new and naive boat owner has not thought about!

Many thanks.
Chris

You could fit small VSR sensing from service battery, link in engine batteries when service is on charge.

What is your normal engine - service battery charge ?

Brian

 

[fergycool]

Thanks.

Both starter batteries are charged from respective alternators on each engine. The domestic battery is charged via a relay from one of those.

One thing that worries me about adding the VSR is that the chargers will no longer be "smart" multi stage ones. Am I correct in thinking that, or should I not be unduly worried about it?

 

[halcyon]

Thanks.

Both starter batteries are charged from respective alternators on each engine. The domestic battery is charged via a relay from one of those.

One thing that worries me about adding the VSR is that the chargers will no longer be "smart" multi stage ones. Am I correct in thinking that, or should I not be unduly worried about it?

Next time you have the engines running charging the service battery, check the voltage on the engine battery not charging, against the service battery being charged from the other engine. I have found that the charge is better if both alternators charge the service battery, as the alternator does not reach the regulation voltage due to service load on the system. As the charge voltage is low you loose recharge capacity, linking them, increase available amperage and recharge voltage.

If you link the engine batteries with a switch or VSR, connect a second mains charger to one engine battery, as soon as the charger is switched on both batteries will be linked and charged as one battery, drops out when charge voltage falls or you switch off.

Brian