MPPT Solar Controller Install

[Greg A]

As part of my continuing progression towards putting two 100ah Battleborn lithium batteries under the DS dinette bench and replacing the 2 original flooded 6v on the tongue, I purchased the Victron MPPT smart controller 100 | 30 today.
I keep reading the controller should be mounted as close to the batteries as possible.

Dilemma: I currently have the factory 160W panel on the roof(rear) with the PWWM controller over the fridge in our 2015 19. Probably about a 6' run of 10Ga from the panels to the controller thru the fridge vent and then on behind the bathroom to the DS Bench and then out to batteries on the tongue.
I could put a DC PV isolator at the current solar controller location and then mount the new controller on the battery board under the DS bench which will put it right next to the new batteries. Since it has the Bluetooth app, I never need to see it and it would be in the optimal location.
I know the 10Ga run from the panels to the DS bench isn't optimal, but it's what the factory installed and I'm not going to go through changing out the cable due to it's location.
My question is, will I gain from placing the new controller close to the new lithium batteries or should I just replace the controller in it's original location over the fridge?

[padlin]

I never saw over 10 amps from my 160w panel, so I don't see a problem with a 6' run of 10g.

[BruceW]

I agree. In my E19 I have two 6V AGMs mounted in the tongue storage box and a Renogy MPPT controller mounted under the dinette. Probably 6’ of 10 AWG between them which should be good for 30A. Best case conditions I’m probably getting only 10 amps. Even though I do have a BT connected app to monitor things, I still like being able to see the basic indicator lights to see at a glance when it is getting enough solar to still function and can see that it is working.

[Greg A]

So if I understand correctly, both of you would leave the new controller over the fridge and not bring it down next to the new batteries?
Bruce, you put the solar controller where I’m thinking of putting it.
I’m confused why the install instructions keep saying to mount it as close as possible to the batteries.
If I relocate it from the fridge to the DS bench, then I’ll be 1 ft from the new batteries and the long 10ga run approximately 12 feet would be from the panel to the controller. Currently, it’s about 6 ft from panel to controller over the fridge and another 6+ ft to the DS bench.

[Vermilye]

The reason you want the controller as close to the batteries as possible is because the controller senses the battery voltage to determine the charging stage. Since it does this while the charging current is going between it & the battery, the voltage at the controller should be as close as possible to that of the battery. The longer the wire between them, the more resistance caused voltage drop occurs, and the less accurately the controller will sense battery voltage.

As a temporary solution, I don't see a problem locating it at the current position, but when you switch to lithium batteries, I'd move the controller to the battery location.

[padlin]

We have folks here that know more then I and I'd just be guessing as to why they want it as close as possible to the batteries.

As long as the cables are the right gauge for the length of the run and it's fused correctly, I don't see any issues. Same goes for the panel to controller run.

This is the chart I use. https://www.bluesea.com/products/200...election_Chart

[tdf-texas]

Three reasons.

One: the solar controller has battery temperature compensation for the battery charge rate. The temperature is measured at the controller and should be close to the battery so it measures a temperature closely matching the battery temperature.

Two: A MPPT solar controller puts out a battery charging current that is greater than the current coming from the solar panels. The higher the current, the higher the loss due to wire resistance. Mounting the controller close to the battery minimizes the overall loss due to wire resistance.

Three: What Jon Vermilye said.

Originally Posted by Vermilye

The reason you want the controller as close to the batteries as possible is because the controller senses the battery voltage to determine the charging stage. Since it does this while the charging current is going between it & the battery, the voltage at the controller should be as close as possible to that of the battery. The longer the wire between them, the more resistance caused voltage drop occurs, and the less accurately the controller will sense battery voltage.

For the temperature compensation issue alone, mounting the controller over the fridge would not be an optimal choice as the temp there would be very different than the battery temp.

[Vermilye]

Originally Posted by tdf-texas

Three reasons.

One: the solar controller has battery temperature compensation for the battery charge rate. The temperature is measured at the controller and should be close to the battery so it measures a temperature closely matching the battery temperature.

Two: A MPPT solar controller puts out a battery charging current that is greater than the current coming from the solar panels. The higher the current, the higher the loss due to wire resistance. Mounting the controller close to the battery minimizes the overall loss due to wire resistance.

Three: What Jon Vermilye said.

Just a minor point - Temperature compensation should be turned off with lithium batteries, so that shouldn't be a problem once you switch. That said, if you add a Victron Smart Shunt or a 712, you can run a temperature probe between the battery post & the shunt. Using the Victron software link between the shunt & solar controller, you can set a shut off for the solar controller based on battery temperature. While the Battleborn BMS should do this, it is a simple additional safeguard.

[Greg A]

Thank you, great explanations. I was just reading a statement that was saying to take any power loss from the panel run to the controller and then be “short and fat” on the run from controller to the battery.
This would seem to be exactly what Jon and tdf are relaying. I think I know where to head on this now, new controller mounted on battery platform under DS bench.
Thank you all for your responses.

[Effie]

If you install the Victron battery monitor 712 or the smart shunt you can set up a wireless Bluetooth communication to the solar controller with Victron VE.Smart networking. The battery voltage (and temperature if you have the sensor) will be transmitted to the solar controller, a bit more distance between the controller and the batteries will not be a problem.

[UncleTim]

Hey Greg,

Would you mind taking pictures so we can see your handiwork too?

Thanks.

[Greg A]

Originally Posted by UncleTim

Hey Greg,

Would you mind taking pictures so we can see your handiwork too?

Thanks.

I definitely will, Tim. All the parts are coming in slowly but surely and I'll probably be adding some of the items over the next month. May not actually hook up the BMV-712, shunt, DC to DC converter until I actually place the new batteries. Not worth running wiring from the old batteries on the tongue when the new batteries are going to be right next to all the equipment.
Here is a pic of the install for the Blue Sea battery shutoff switch(Live) and the BMV-712 Battery Monitor(Not Live yet). Battery/Equipment board will be going in to the right of the black tank forward.

[dstreight]

FWIW, I use Victron's Smart Battery Sense and its ability to set the low temperature cut-off of charge current to my LFP system from the Victron controller...