Jabsco Blower drawing 6 amps from House Batteries?

[BareFeet]

Hi,

Hoping the collecting knowledge can help me narrow this problem down.

My 2014 Lagoon 380 is configured such that the Port engine charges the house batteries, starboard charges the starter batteries.

When I power up the port engine, the blower starts and you see the ampage draw, but when you kick the engine over and the alternator comes online, the ampage draw remains. Is this normal? I would have thought that the blower should take power from the alternator when the engine is running, not the house batteries.

Thanks,

[Sailmonkey]

Where is your ammeter installed in relation to the alternator and batteries?

I.e...if the alt feeds the batteries directly, then the batteries go to a switch panel, and all current entering/leaving the panel is through the ammeter, you'll not see the current going into the batteries, only the current leaving.

Your blower draws 6amps when on. Let's say the alternator puts out 40 amps . That means (in rough terms) that 32 amps are being shoved into the batteries.

[BareFeet]

Cheers for the speedy response Sailmonkey.

The ampmeter as you describe and is installed after housebank and the readout shows voltage of the house batteries and current draw - whether this is the fridge, nav instruments, or in the this case the blower. If i disconnect the blower, the ampage draw is eliminated.

It seems odd to me that the blower is taking power from the house batteries and not directly from the alternator.

[Sailmonkey]

Not odd at all. And it's not taking power from the batteries when the engine is running, the current draw is simply a pass through.

[guyrj33]

if the ammeter shunt were installed so that it measured all of the current passing through the battery you would see the net current being supplied by the battery. With blower on and alternator off -6, with only 40 amp alternator on +40, with alternator and blower both on +34.
The ammeter shunt is typically installed in the single ground lead from the battery to you common grounding point.

[Sailmonkey]

Originally Posted by guyrj33

The ammeter shunt is typically installed in the single ground lead from the battery to you common grounding point.

Unless the ammeter is part of a panel. Those almost always only measure current consumed by devices fed from the panel

[guyrj33]

Originally Posted by Sailmonkey

Unless the ammeter is part of a panel. Those almost always only measure current consumed by devices fed from the panel

Good point SailMonkey.

[BareFeet]

Many thanks for the responses.

To add some further context, I've traced wiring from the blower to the alternator via a relay. This was why I thought that the blower should take power from the alternator when the engine is running, not the house batteries.

I've switched relays from the starboard engine, hoping this to be the issue without success.

Does this change your thoughts?

Cheers,

[Sailmonkey]

Originally Posted by BareFeet

Many thanks for the responses.



To add some further context, I've traced wiring from the blower to the alternator via a relay. This was why I thought that the blower should take power from the alternator when the engine is running, not the house batteries.



I've switched relays from the starboard engine, hoping this to be the issue without success.



Does this change your thoughts?



Cheers,

Nope,

That just tells me the blowers are activated by the alternator excite current, but not run by it.

Either way, the blowers are not taking power from the house battery with the engine running. Like I said before, the power is passed over the battery and is coming from the alternator. Kill the engine and then the power is coming from the battery.

[PaulinOz]

Power your engine panel up, note that you see 6 amp draw on meter. (do not start engine).

Now plug in and switch on shore power and battery charger, or start generator and battery charger. ( Do you still see 6 amp discharge or do you see a charging current that you know is going into batteries)?

If your meter still reads the 6 amp discharge, your question has already been answered above, your amp meter is not in the charging circuit only reading power usage from 12 volt distribution panel. Which is the way that the Lagoon power panel and associated amp meters are wired.

If your 6 amp is being read on a 3rd party installed battery monitor, you need to know where it's shunt is installed in the circuit before you can make any decisions based on what you are reading on said meter.

[BareFeet]

Thanks for the responses and appreciate the guidance. PaulinOz - great suggestion and will check when im next on shore power - which is likely to be a while, given prices in Croatia.

Strange the Lagoon would wire the engines different though as the Starboard engine blower doesnt show on the ammeter and I guess just runs off the starter battery/alternator.