Should I connect my bilge pump to the starter or the leisure battery?

[Alway Swilby]

As it says in the title.

At the moment my automatic bilge pump runs off the starter battery. This is how the boat builder connected it. I've been thinking though. The starter battery is 110 ah and is only charged by the starter alternator on the engine. The leisure bank is much bigger and as well as being charged by the domestic alternator it is also charged by the inverter charger and a 500 watt solar aray. We are soon to leave our boat in a marina for the winter for the first time and it seems to me it would be better being supplied by the leisure batteries because they are less likely to run down if the bilge pump starts running lots. Even if it does run them down due to failure of shore power and the sun (and the stern gland) then I would still be able to start the engine.

[Jen-in-Wellies]

If it is on a shore line over winter and that is being used to charge the leisure batts, then having the bilge pump connected to them would seem to be sensible.

How often does your bilge pump run? Is the stern gland a bit on the leaky side and tripping the pump regularly? If so, then if the auto switch fails the boat will likely sink unless someone spots it in time and the bigger battery bank will make no difference. If it is to cope with rain leaks via deck boards, then having someone check it after a storm is a good idea.

Bilge pumps take around 4A, so will run a 110Ahr batt flat in 27 hours ish, or a day.

 

Jen

[TheBiscuits]

Mine is connected to the domestic bank now, not to engine battery as it was when I bought it.  It's more to do with tidying up the wiring than any great concerns about flooding though - the boat is dry.

 

If you are leaking that badly you should fix the leak though, as there's no point having a well charged engine battery a couple of feet below the water!

[Grebe]

Whichever battery you choose to use:

 

Make sure the dedicated feed from the battery has a fuse in it.

Make sure the fuse is OUTSIDE the battery box.

 

Battery gases can go BANG, so you do not need a potential ignition source.

[Alway Swilby]

30 minutes ago, Jen-in-Wellies said:

If it is on a shore line over winter and that is being used to charge the leisure batts, then having the bilge pump connected to them would seem to be sensible.

How often does your bilge pump run? Is the stern gland a bit on the leaky side and tripping the pump regularly? If so, then if the auto switch fails the boat will likely sink unless someone spots it in time and the bigger battery bank will make no difference. If it is to cope with rain leaks via deck boards, then having someone check it after a storm is a good idea.

Bilge pumps take around 4A, so will run a 110Ahr batt flat in 27 hours ish, or a day.

 

Jen

The pump rarely auto runs, sometimes during a stint of reversing but once i've moored up and tightened the greaser it stops, the stern gland hardly leaks at all, Rain is unlikely to get in there, Semi Trad with a pram cover. Any water on the very rear stern drains over the side or into the weed hatch and hence not the engine bay.

 

29 minutes ago, TheBiscuits said:

Mine is connected to the domestic bank now, not to engine battery as it was when I bought it.  It's more to do with tidying up the wiring than any great concerns about flooding though - the boat is dry.

 

If you are leaking that badly you should fix the leak though, as there's no point having a well charged engine battery a couple of feet below the water!

Not leaking, see above.

 

I'm just trying to be ultra safe.

[WotEver]

To answer the topic title - the Leisure bank for all the reasons that you list and which have been confirmed above. 

[Jen-in-Wellies]

20 minutes ago, Grebe said:

Whichever battery you choose to use:

 

Make sure the dedicated feed from the battery has a fuse in it.

Make sure the fuse is OUTSIDE the battery box.

 

Battery gases can go BANG, so you do not need a potential ignition source.

Do I hear the voice of experience? ? ?

Edited September 15, 2020 by Jen-in-Wellies