Battery for Bow Truster?

[Tim Good]

This was discussed recently but I have an added dimension. I have 4 house batteries, 1 starter and a bow.

I have a switch for House, House + Bow, House + Starter and All. This allows me to send my mains charger or solar to some or all of the batteries.

But it does mean bringing together some or all with the house bank. With that in mind does I need to ideally have the same batteries all round or can I have a certain type for my house banks idea of regular discharging and then a different type for my Bow idea for high output bursts?

 

[Tranona]

Perhaps better to have all 3 banks independently switched and a 3 output battery charger - that is how my boat is wired. A parallel switch to link the house bank with the starter is useful for emergency starts, although rare for the start battery to fail if it is only used for starting. Don't see areal need for solar to go to anything other than the house, although guess it might be useful to have it to the start if you go for long periods without running the engine. If you are not using the engine or bow thruster you only have to consider the self discharge of these batteries as all your consumption will be from the house bank.

I have the same size and type of AGMs for all three banks. Seems to have plenty of power for the bow thruster which you normally only use in short bursts.

 

[William_H]

The domestic services batteries should be deep cycle type expensive but necessary. They will deliver a lot of current for engine start because they are big.
The engine start battery may be a smaller cheaper type designed for engine start delivering a lot of current for a short period despite small size and cost.
The Bow thruster battery is a variable question. If you only thrust for short periods then an engine start type might be suitable. For real long period operation a deep cycle might be better but all this depends on the size of the charge cable and alternator in that some current will be supplied by the engine alternator and engine battery via these cables. I would go for no thruster battery but very heavy cables if fitting a thruster. But you have a battery so use it.
Meanwhile charging all batteries in parallel while not ideal for different types of battery in terms of charging voltage etc is probably OK providing it is not too high. olewill