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Old 10-08-2018, 16:04   #16
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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Originally Posted by Catapault View Post
Suggestion.

1. Install Victron SmartSolar MPPT Controller in current location.
2. Install Victron 712 Battery Monitor Shunt at the Battery. With Monitor itself wherever you like nearby.

Configure both on wireless (bluetooth) VE.NET , the Battery monitor shares accurate voltage and temp with the Solar controller so don't need to use its own sense wires. (Can also be done on wired VE.Net).

Both devices have Bluetooth for control from your Phone.

Regards

Mark.
That sounds like a cool way to do it. How well does the Bluetooth net work when the sensor is in the battery cabinet and the solar controller far aft?
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Old 10-08-2018, 17:14   #17
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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It depends on the cause of the error. If it is a calibration error then the offset should work. If it is caused by wire and connection resistance then I don't see it working. If you have a .2v drop at 10amps then you'd have a .02v at 1amp.
At 1 amp you don't care the offset is not affecting it. Its only going to matter between 14.7 and 15 volts or whatever you have. The amps don't matter its the volts your trying to get up.
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Old 10-08-2018, 21:58   #18
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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At 1 amp you don't care the offset is not affecting it. Its only going to matter between 14.7 and 15 volts or whatever you have. The amps don't matter its the volts your trying to get up.
Precisely, the voltage drop at 98% SOC with cloud cover is no issue. It is negligible.

The voltage drop with hungry batteries, and full sun is what you need to address for setting the transition from bulk to absoprtion. The voltage drop in float mode is negligible because the charge current is so low.
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Old 10-08-2018, 23:08   #19
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

Thanks everyone for the suggestions... much appreciated.

Mark - do you have any feel for the range that the VE.direct bluetooth connection can work over?
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Old 10-08-2018, 23:14   #20
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

A controller turning off would be useless. It's trying to control the charge voltage. Not the stooped charged voltage. When the controller shuts off. It's see battery voltage. And says. Oh it's not charging. Guess I better turn back on. The voltage reading it took while off would be meaningless
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Old 11-08-2018, 08:59   #21
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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At 1 amp you don't care the offset is not affecting it. Its only going to matter between 14.7 and 15 volts or whatever you have. The amps don't matter its the volts your trying to get up.
You could be pushing 100amps at bulk charge and 10amps at absorption. If the .2v measurement was at 10amps then you'd get 2v at 100amps.
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Old 12-08-2018, 09:30   #22
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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You could be pushing 100amps at bulk charge and 10amps at absorption. If the .2v measurement was at 10amps then you'd get 2v at 100amps.


I have 425 watts using hard panel, mono cell solar panels. The most I can get in is 22-24 amps. With 800 watts of semi flexible panels, I would guess his limit is 50 amps based on my experience.
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Old 12-08-2018, 09:39   #23
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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I have 425 watts using hard panel, mono cell solar panels. The most I can get in is 22-24 amps. With 800 watts of semi flexible panels, I would guess his limit is 50 amps based on my experience.
Certainly limited with solar. AC chargers can easily be 100 amps.
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Old 12-08-2018, 09:54   #24
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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(...)



The catch is that the controller is located a fair distance from the house bank that it is charging, so voltage drop between controller and batteries is a concern.


(...)

Imho, your regulator-to-battery wires are just way TOO THIN.


Why not use fatter cables, get rid of voltage drop???

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Old 12-08-2018, 10:02   #25
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

No way one gets 100A on an Outbound 44. Unless you are decked with solar panels perhaps.


And if it is 100A indeed then my comment on your wires being mickey mouse is twice as valid.



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Old 12-08-2018, 10:05   #26
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

barnakiel has it exactly right.
As I've added solar, I have doubled up my regulator to battery feed wire size.
It started with two small panels and 12 gauge, but I went to 8.
After adding more, it's on the list go to 6 gauge.

The distance from the MPPT to the LiFePo4's is only about five feet, but the drop is small, but still noticeable at 20 + amps.
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Old 12-08-2018, 13:15   #27
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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No way one gets 100A on an Outbound 44. Unless you are decked with solar panels perhaps.


And if it is 100A indeed then my comment on your wires being mickey mouse is twice as valid.



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Huh, If you were replying to me I specifically said 100amps with an AC charger but not with solar.

Either way, it was just an.example of Ohms law. The votage drop is dependent on the current, i.e. it is not a fixed offset.
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Old 12-08-2018, 15:41   #28
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Re: MPPT controller that senses actual battery voltage (w/o separate sense lead)?

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Huh, If you were replying to me I specifically said 100amps with an AC charger but not with solar.

Either way, it was just an.example of Ohms law. The votage drop is dependent on the current, i.e. it is not a fixed offset.
Yup. 100A from a charger far more common. Still, it is a major charger.

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