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Old 22-06-2018, 07:04   #1
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Connect MPPT to Isolator?

Should I connect the MPPT charger to the battery isolator?
If I do so, then the MPPT will only deliver energy and we wont be able to keep it connected to the Switchboard, as it is now.
Please see the diagram of the current setup in the sailboat (attachment). And if you see anything wrong let me know as well
Thanks in advance
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Old 23-06-2018, 05:51   #2
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Re: Connect MPPT to Isolator?

All charge sources should output direct as possible to the bank.

Especially sensors to the batt post itself.
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Old 25-06-2018, 02:35   #3
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Re: Connect MPPT to Isolator?

no. connect to house battery direcit. I don't know why it's in the panel wires?. an MPPT needs a battery connection as reference to work. it probably won't even work when connected to the iso. plus you lose power through it.
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Old 25-06-2018, 03:00   #4
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Re: Connect MPPT to Isolator?

this leaves all your house wiring live even if the positive battery isolator is disconnected.
as the negative battery side is still connected to the mppt ,solar controllers use the negative side to control charge.

connect both pos and neg mppt wires direct to the house battery with inline fuses.
install a breaker on the pos wire from solar panel to mppt.
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Old 25-06-2018, 03:23   #5
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Re: Connect MPPT to Isolator?

I take all my loads from the battery. I have all my charge sources directly to the battery. As far as your diagram, I don't see any fuses on the battery positive.
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Old 25-06-2018, 07:01   #6
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Re: Connect MPPT to Isolator?

Quote:
Originally Posted by Zil View Post
I take all my loads from the battery. I have all my charge sources directly to the battery. As far as your diagram, I don't see any fuses on the battery positive.
They all have inline fuses next to each device. I will update the diagram, thanks.
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Old 25-06-2018, 07:11   #7
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Re: Connect MPPT to Isolator?

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Originally Posted by smac999 View Post
...I don't know why it's in the panel wires?...
The previous owner explained me that you can connect up to 15A to the Load Output of this specific MPPT. Do you mean that I should not connect anything to the MPPT Load Output?
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Old 25-06-2018, 07:42   #8
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Re: Connect MPPT to Isolator?

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The previous owner explained me that you can connect up to 15A to the Load Output of this specific MPPT. Do you mean that I should not connect anything to the MPPT Load Output?
no need to use "load"function on boat wiring as your main switch panel controls your loads on board.

it might be usefull if you wanted an automatic anchor light coming on at dusk and off at dawn as the function is programable on most solar controllers for one device of upto15amps in this case .
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Old 25-06-2018, 07:51   #9
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Re: Connect MPPT to Isolator?

Also useful as LVD, non-essential device you want isolated when batt gets low.

Limited to 10? Amps though
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Old 25-06-2018, 08:07   #10
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Re: Connect MPPT to Isolator?

I think the load output is meant to be used with loads that are always connected to the battery and are live when you are not on the boat. The manual states that the load output on the controller is turned off when the battery voltage goes down to a certain level, thus you don't discharge the battery too deeply while you are away.

You have to decide which is more important as to what to connect to the load output -
Run bilge pump until batteries are destroyed or let boat sink to save battery.
Keep food good in fridge until batteries destroyed or let food go bad.

I suppose you can leave it on the switch panel and have everything on the boat turn off (nav lights, vhf) when it decides to save the battery from low voltage.
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Old 25-06-2018, 08:49   #11
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Re: Connect MPPT to Isolator?

Usage of any LVD circuit obviously mean you bypass with critical "always on" loads.

And of course with such loads the boat must be regularly checked that all is well.

None of which is specific to SC load terminals, they are not inherently good or bad, just need to understand their issues.
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Old 26-06-2018, 14:06   #12
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Re: Connect MPPT to Isolator?

You need fuses at the battery positives. On each battery positive, sometimes called catastrophic fuses. Protecting the cables, not the devices.
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Old 30-06-2018, 07:43   #13
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Re: Connect MPPT to Isolator?

New diagram attached.
Thank you guys for all the input. REALLY
The work is almost complete and I found another bus onboard that splits the energy to different devices after the switchboard - not sure if I should kept it as like that. I also tried to map the fuses on the new diagram attached.
The main breaker is installed right after the battery on the black wire. Does this matter? (I installed a breaker from the solar panel to the MPPT on the red wire.)
All loads go now directly on the battery and the energy splits to different devices via a 2 or 3 BUSSES as you see in the picture.
Looks good? Let me know!
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Old 30-06-2018, 08:56   #14
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Re: Connect MPPT to Isolator?

It looks like you are using a diode isolator. Are the battery charger and alternator designed to be connected to an isolator? The problem is a diode isolator has a .2 - .7 volt drop across it. A regular alternator with internal regulator senses the voltage at the alternator on the output wire. If it's voltage setpoint is 14.1 volts, the battery would be charging at 13.9 - 13.4 volts. It would take much longer to charge the battery.

A battery charger would go into float too soon.

If they have a voltage sensing wire that connects directly to the battery then there is no issue. Or some alternators had a second output post that accounted for the voltage drop.

Fuses that are at the device are intended to protect the device. You need fuses (or circuit breakers) as close to the battery as that size wire exists.

The fuse just off the house battery is theoretically sized to protect that big wire. When you get to the smaller wires it won't help.

The fuse at the device only works if the device shorts. If the smaller wire leading to it shorts, it can cause a fire without a fuse on that wire closest to the battery end.
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Old 02-07-2018, 01:12   #15
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Re: Connect MPPT to Isolator?

Quote:
Originally Posted by cal40john View Post
It looks like you are using a diode isolator. Are the battery charger and alternator designed to be connected to an isolator?
The alternator I dont know but the CTek battery charger I got an email from them saying that I should connect it to the Isolator. I cannot find any specs about the Isolator itself. Here is a picture of it attached to this message. As you can see on the picture, some loads were actually connected to the isolator instead of the battery. I have moved them all to the bus splitter. This is correct, right?

Quote:
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The fuse at the device only works if the device shorts. If the smaller wire leading to it shorts, it can cause a fire without a fuse on that wire closest to the battery end.
Yes, there is a big fuse on the main cable right after the battery, on the wire going to the first bus splitter.
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