Bow Thruster Battery Charging

[Papawads]

I have a 2001 Jeanneau with aftermarket bow thruster fitted; but don’t know when.

Just noticed that the two bow thruster batteries are only charged by the alternator. This is interesting, because the original charger has three outputs, with two currently doubled up to charge the three leisure batteries, and the other for the starter battery.

As it would be such a simple job (all wiring in same location) to use the third charging wire for the thrusters, I’m wondering if there’s a good reason they didn’t…

(As usual) the three outputs from the alternator diode box? run to three terminals, but with the 240v/DC charger outputs only running to leisure and motor terminals.

Thoughts most welcome :-)

[hjohnson]

It’s likely because the bow thruster is only likely to be used while the engine is running. There needs to be a lot of amps to run the thruster, but it actually doesn’t take much capacity (since you’re only running it for a few seconds at a time usually). Having the alternator on there helps it both in terms of amps, and makes up the difference pretty quickly.

[smac999]

I would hook up the charger if you don't motor a lot year round. it's good for storage. if you motor a lot then less of an issue. (in which case you don't need the engine battery on a charger either...)

most boats sit 7 months a year in that case having the charger maintaining them would be good.

[GreenWave]

I will add that boats which REQUIRE the motor to be running in order to use a windlass or bow thruster are DANGEROUS IMO and just silly. I get the why, but I would not live with that. I can think of numerous scenarios where I would want and need to use either of these without a running or working engine.