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Old 11-04-2018, 14:50   #76
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Re: Inverter/Charger Recommends

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Originally Posted by john61ct View Post
Then I don't even understand your point.

I thought you mean a combi unit can't be simultaneously charging the bank (charge source, AC input / DC output)

and servicing other (AC) loads at the same time (from DC or upstream AC input)

Maybe if you specify more clearly what you mean?

Keep in mind my preference is to use AC power, in or out, as little as possible.
You said, "....simultaneously charging the bank (charge source, AC input / DC output) and servicing other (AC) loads at the same time (from DC or upstream AC input)

If I'm understanding you correctly, you are describing the system I mentioned in post #73.

As far as I know, very few recreational marine combo unit will function this way.
For the inverter to be the only source of AC power it will have to have a line rated capacity. Meaning for a normal 30A service, the inverter would have to have a 3.6+Kw rating. 6+Kw for 50A.
I'm not even sure you can find a inverter/charger the is rated at 3.6Kw, that operates on 12vdc.
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Old 11-04-2018, 15:37   #77
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Re: Inverter/Charger Recommends

(transmitterdan beat me to it...)

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I don't think power assist is an important requirement for many.
Agree generally because most boats aren't designed with this function in mind, that is, they have a generator with an output to cover the max load. A boat built with power assist in mind means you only need -- roughly -- half the generator capacity, resulting in less weight, size and cost. With power assist, I regularly pull 3kws from a Honda 2k.

Fwiw, best of both worlds ought to be a gang of two combis :-)
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Old 11-04-2018, 15:42   #78
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Re: Inverter/Charger Recommends

Double post.
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Old 11-04-2018, 15:54   #79
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Re: Inverter/Charger Recommends

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If I'm understanding you correctly, you are describing the system I mentioned in post #73.
Is that good or bad?

I really don't want to argue for the fun of it, honestly just want to make sure I understand what points of disagreement remain, so I can increase my own understanding.

Were/are you saying it's normal for a combi unit to stop charging the battery bank or feeding the DC loads, just because you want to start using your convection oven?

That to me would just be mind-bogglingly idiotic design at a fundamental level.

The idea that DC-only loads and charging couldn't happen concurrently, even more so.
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Old 11-04-2018, 16:14   #80
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Re: Inverter/Charger Recommends

John,

A combi unit stops producing AC and begins charging the batteries when there is AC input. If it has power assist feature it can stop charging and produce extra AC to help supply a peak demand in excess of the available mains power. But in that mode it make no sense to be charging because that would just further load the AC mains which defeats the purpose of power assist.

When there is no AC input it does not charge the batteries.

There is no mode where a combi charges and produces AC power simultaneously. It would make no sense to do so.
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Old 11-04-2018, 16:16   #81
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Re: Inverter/Charger Recommends

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Were/are you saying it's normal for a combi unit to stop charging the battery bank or feeding the DC loads, just because you want to start using your convection oven?

.
You are not giving enough info to answer the question.

But let me fill in the gaps.

Were/are you saying it's normal for a combi unit to stop charging the battery bank or feeding the DC loads with shore power energized, just because you want to start using your AC convection oven?

No.
Because the power for your convection oven is coming from shore power through the inverter.

Now lets go the other way.

Were/are you saying it's normal for a combi unit to stop charging the battery bank or feeding the DC loads with no shore power or other AC source, just because you want to start using your AC convection oven?

Yes.
Because, 90% of all inv/chg once switched on with out an AC input will go straight into invert mode.
The charge mode won't start until a steady source of AC is sensed on the AC input.
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Old 11-04-2018, 18:52   #82
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Re: Inverter/Charger Recommends

OK, distinction between "through" and "by" is the source of the confusion. Power assist does further muddy those waters.

Just for the sake of completeness, it is still the case that my battery protective systems require the ability to isolate each bank from charge sources while loads continue to be serviced, and vice-versa.

Which alone eliminates the ability to use such a combi unit.

But even without that, I would continue to prefer separates, each sized as needed and easily swapped out / added to as I like, without having to replace both at once. Plus easier redundancy.

Truth is I try to avoid AC as much as possible anyway, which bias I'm sure is a factor here.

Thanks for the inputs and feedback y'all!
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Old 12-04-2018, 01:13   #83
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Re: Inverter/Charger Recommends

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I'm not even sure you can find a inverter/charger the is rated at 3.6Kw, that operates on 12vdc.
Victron quattro 12/5000 does it.
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Old 12-04-2018, 04:42   #84
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Re: Inverter/Charger Recommends

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Just for the sake of completeness, it is still the case that my battery protective systems require the ability to isolate each bank from charge sources while loads continue to be serviced, and vice-versa.

Which alone eliminates the ability to use such a combi unit.

???

Ya got me again.

Do you mean AC loads, or DC loads, or all loads?

If you mean AC loads... our combi is either charging (from shorepower or genset) and all AC loads are serviced by the shorepower or genset AC (not by the combi)...

Or it's inverting to service AC loads, and can't be charging because shorepower or genset AC aren't present.

Doesn't that mean it's effectively isolated from "from charge sources while loads continue to be serviced, and vice-versa." ?

???

Or do you mean DC loads too? If so... why's that?

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Old 12-04-2018, 06:01   #85
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Re: Inverter/Charger Recommends

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???

Ya got me again.

Do you mean AC loads, or DC loads, or all loads?

If you mean AC loads... our combi is either charging (from shorepower or genset) and all AC loads are serviced by the shorepower or genset AC (not by the combi)...

Or it's inverting to service AC loads, and can't be charging because shorepower or genset AC aren't present.

Doesn't that mean it's effectively isolated from "from charge sources while loads continue to be serviced, and vice-versa." ?

???

Or do you mean DC loads too? If so... why's that?

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John is mostly talking about the DC side of the circuit.

Think of it this way, all of your charge sources + leads are connected to a single terminal stud. And all of you loads + leads are connected to another terminal stud. Your battery's + is connected to another terminal stud.

Now connect your charge terminal stud to your battery terminal stud through a switch (a solenoid is really used but a switch is easier to understand) and connect you load's terminal stud to the battery stud through another switch.

Now with both switches closed, current can flow from the charge sources to the battery and from the battery to the loads.

Now lets say your battery charger goes wack-o, you can open the charge source switch and eliminate the problem while still keeping all of the loads connected to the battery.

Vis-versa if a load starts to draw the battery down too much, you can open the load switch while still keeping the charge sources connected to the battery.

Where most people have problems with combo units is how and where do you place them in the system above. Be cause they are both a charger and a load. So do they go on the charge source terminal or the load terminal?
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Old 12-04-2018, 06:05   #86
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Re: Inverter/Charger Recommends

DC loads, which of course includes the inverter.

I'm not sure what to say that could make the meaning clearer, maybe go back and revisit it?

OK, a visual metaphor:

Think about the bank as a castle with a moat. One drawbridge for traffic In, another for Out, each must be one-way only.

No more room for more people, raise the In bridge, still want people to be able to leave. And V/V.

Combi is a guild that insists it needs a single bridge to be two-way.

Sorry, not allowed.
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Old 12-04-2018, 06:05   #87
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Re: Inverter/Charger Recommends

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Originally Posted by john61ct View Post
OK, distinction between "through" and "by" is the source of the confusion. Power assist does further muddy those waters.

Just for the sake of completeness, it is still the case that my battery protective systems require the ability to isolate each bank from charge sources while loads continue to be serviced, and vice-versa.

Which alone eliminates the ability to use such a combi unit.

But even without that, I would continue to prefer separates, each sized as needed and easily swapped out / added to as I like, without having to replace both at once. Plus easier redundancy.

Truth is I try to avoid AC as much as possible anyway, which bias I'm sure is a factor here.

Thanks for the inputs and feedback y'all!
I also agree that dual buss and separate units are the way to go.
Especially in LiFePo systems.

But for 99% of boats, converting over is an expensive proposition.
And where combo's start to look really good..
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Old 12-04-2018, 06:08   #88
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Re: Inverter/Charger Recommends

Yes

Quote:
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Where most people have problems with combo units is how and where do you place them in the system above. Be cause they are both a charger and a load. So do they go on the charge source terminal or the load terminal?
Neither.

To keep the required functionality, they realize a combi is not suitable, and therefore buy the two functionalities as separate units.
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Old 12-04-2018, 06:13   #89
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Re: Inverter/Charger Recommends

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I also agree that dual buss and separate units are the way to go.
Especially in LiFePo systems.

But for 99% of boats, converting over is an expensive proposition.
Even for contexts where LFP is not currently planned, I design the permanent infrastructure and choose components so that everything is suitable for whatever bank chemistry the owner may want in future.

Batts are consumables.

And this approach has other benefits beyond making such transitions much **less** expensive.
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Old 12-04-2018, 07:10   #90
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Re: Inverter/Charger Recommends

Next week after I install my new combi unit to replace the 17-year working combi unit, I'll post an on topic update :-)
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