Are my batteries being used while on shore power?

[mitiempo]

Originally Posted by TitoSoto

Gooooot it! That's basically what I was wanting to figure out

I just see my battery monitor not going to 100% anymore every time I go out sailing and disconnect from shore and was wondering if this was why (e.g. batteries being used even while at the dock).

Thanks!

Battery monitors will accumulate errors over time. When you know the batteries are fully charged, for example when on shore power for a day or so, synchronize the monitor to full.

[StuM]

Originally Posted by mitiempo

The batteries are in the middle but as long as the charger is capable of supplying any amperage needed by the loads they are not cycled.

Conceptually, the batteries are not "in the middle".

As far as current flow is concerned, batteries, house loads and the charger are three separate circuits connected to a common positive and negative.

If you disconnect the batteries, current will still flow from the charge source to the house loads.

[StuM]

Originally Posted by mitiempo

As long as the current being used is less than the charger's max output.

True.

[mitiempo]

Originally Posted by StuM

Conceptually, the batteries are not "in the middle".

As far as current flow is concerned, batteries, house loads and the charger are three separate circuits connected to a common positive and negative.

If you disconnect the batteries, current will still flow from the charge source to the house loads.

As loads increase on the batteries the charger will provide current, but not instantly.

In many cases a charger will not output current if there are not batteries present. Only some chargers will function as a power supply.

[leftbrainstuff]

Your inverter is typically also your battery charger. When on shore power AC is supplied by shore power whichnwill also power your house battery charger.

You can set so that you use both house and shore power on some inverters.

What make and model of inverter do you have?

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[Stu Jackson]

Originally Posted by leftbrainstuff

1. Your inverter is typically also your battery charger. When on shore power AC is supplied by shore power whichnwill also power your house battery charger.

2. You can set so that you use both house and shore power on some inverters.

3. What make and model of inverter do you have?

1. Not quite. In one of his earlier posts, he asked "What is I/C?" And I explained it. There are TWO possible configurations: a) an I/C and b) separate inverter and separate charger. "Usually" has NOTHING to do with it.

2. NEVER. You can NEVER have two separate sources of AC power to the same circuit. Yes, you could have shorepower feeding some circuits and the inverter feeding others, as one possible wiring scenario.

3. Good question.

Please be careful when writing answers. You might want to preview them first.

[MarkSF]

Originally Posted by ramblinrod

IMHO if you need to ask these rudimentary electrical questions before starting an electrical refit, you should be studying electrical and electronic theory, ABYC (or appropriate marine electrical
standards for your region) and building some practical skills, or
Hiring a sparky, before attempting a boat electrical refit that will otherwise probably end up in an unsafe electrical system that will not pass a marine survey and will devalue the vessel.

Sorry for
Being so blunt, but I witness unsafe DIY electrical mods every day, including the absolute worst I've ever seen, about a month ago, where the surveyor correctly declared the electrical system a "mess" and the owner was pissed cause I'm all his years of boat ownership he had only had one blown fuse. Just because faulty wiring hasnt caught fire yet, there's always tomorrow.

Be safe, you don't know what you need to know until you do know.

Like he said. How can you undertake an electrical refit without understanding boat electrical systems?

[TitoSoto]

Originally Posted by leftbrainstuff

What make and model of inverter do you have?

Its a black Xantrex inverter, 1500w I think.

It must be a pretty basic one (a "modified sine wave"), since it doesn't run my induction stovetop (which are known to require pure sine wave inverters).

[Stu Jackson]

For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

Link-series Charging Algorithms -- The "Gotcha" Factor!

DEFAULTS are factory settings that are made to be modified to suit your setup.

Also read this one:

Programming a Battery Monitor (by Maine Sail)

Keeping Your Battery Monitor More Accurate Photo Gallery by Compass Marine How To at pbase.com

[nigelmercier]

Originally Posted by MarkSF

Like he said. How can you undertake an electrical refit without understanding boat electrical systems?

What I thought on day one.

[Beausoleil]

Originally Posted by Stu Jackson

2. NEVER. You can NEVER have two separate sources of AC power to the same circuit. Yes, you could have shorepower feeding some circuits and the inverter feeding others, as one possible wiring scenario.

3. Good question.

Please be careful when writing answers. You might want to preview them first.

Don't say "never". Some inverter/chargers, like the Victron Quatro, can pull some current from the batteries to assist shorepower during temporary brownout situations. Never the less, you can't have multiple un-synchronized AC sources connected to the same load circuit...

[Stu Jackson]

Originally Posted by Beausoleil

Don't say "never". Some inverter/chargers, like the Victron Quatro, can pull some current from the batteries to assist shorepower during temporary brownout situations. Never the less, you can't have multiple un-synchronized AC sources connected to the same load circuit...

Quattro literature:

PowerAssist – Extended use of your generating set and shore current: the Quattro “co-supply” feature
The Quattro operates in parallel with the generating set or the shore connection. A current shortfall is automatically compensated: the Quattro draws extra power from the battery and helps along. A current surplus is used to recharge the battery.

What this means is that it is taking power from the batteries to add to the incoming AC power. That is certainly NOT a second source of AC power on the same circuit.

Originally Posted by Beausoleil

Never the less, you can't have multiple un-synchronized AC sources connected to the same load circuit...

I agree with you here.

I still say NEVER.

Because they are two separate things/methods of providing AC power. One is AC and the other is the inverter providing "support" AC from a DC SOURCE, NOT another AC source.

Especially for the OP.

[thinwater]

Originally Posted by artisanmach

if you are using anything 12 vdc while on shore power...yes, your batteries are being used.

No. There is power coming off the buss, but the charging voltage is greater than the battery output voltage at the same state of charge. So with a tiny draw like a fridge, you are still net charging when at dock. In effect, the charger power is skimming across the buss to the fridge.

Obvious, right? Only false if the combined draw is greater than the charger output, which is not the case I think.

[Beausoleil]

Originally Posted by Stu Jackson

...
What this means is that it is taking power from the batteries to add to the incoming AC power. That is certainly NOT a second source of AC power on the same circuit.

...

Because they are two separate things/methods of providing AC power. One is AC and the other is the inverter providing "support" AC from a DC SOURCE, NOT another AC source.

Especially for the OP.

Not to pick nits, Stu, but when viewed from an engineering point of view, the output of the Quattro's inverter (a separate AC source) is synchronized and bridged to the shorepower/genset input. It wouldn't work unless it's synced. Granted, it's a special case, but it certainly is two separate AC sources.

You also can look at the case of stacked inverters, which are usually synchronized via a sync cable, in order to deliver more power - e.g. two Magnum Energy 2800 watt inverters to deliver 5600 watts. So again, never say never...

[Stu Jackson]

OK, we both got it.

DC source

Synched AC output

Again, for the OP, who seemingly didn't understand maybe even the differences between AC & DC: two separate external sources of AC power, i.e., a generator and your shorepower, should NEVER be mixed. On boats, these two sources are rarely "synched" although means to do so do exist in the industrial world.

Jon, thanks for the ineresting sidebar.