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Old 04-05-2020, 10:15   #1
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Premature Flotation? Two controllers one one bank

We have two 200W panels, each with its own Victron 75/15 controller. Usually by mid day one of them has dropped into float and is delivering zero amps while the other continues bulk charging at max power. It seems like this implies we're not getting all the current we could be, especially considering that we have house loads that are still pulling power during the day.

Is there a fix for this situation? Or is it not even an issue to be concerned about?

Thanks for any thoughts.
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Old 08-05-2020, 06:50   #2
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Re: Premature Flotation? Two controllers one one bank

A Combiner 100 between the banks will make use of the unused capacity of one charging source when the one is still needing charge.
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Old 10-05-2020, 04:17   #3
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Re: Premature Flotation? Two controllers one one bank

Thanks for answering. I looked at the product you referred to but it seems designed for a different problem.

I have *one* battery bank and *two* charge controllers. What is happening is that one controller is in "float" state even though the battery can still accept plenty of current. The controller that is still charging is generating, say 10 amps, but much of that is lost to intermittent house loads like the refrigerator. So the battery is only getting an amp or so even though there is much more charge capacity available.

I'm trying to see if there is a way to convince both chargers to 'stay in the game', so to speak. Also, I'm planning to add another 600W of solar in the next few weeks, and want to make sure there won't be any similar "gotcha's" when adding yet another controller to the mix.
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Old 10-05-2020, 06:20   #4
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Re: Premature Flotation? Two controllers one one bank

DUH, I should READ the posts before jumping to conclusions.

No two charge controllers will have exactly the same transition thresholds, even identical models. While both will start out in the bulk stage on low batteries, sooner or later one will get to the next stage first. When it switches to the next stage it leaves the other one carrying the load which looks like there is unused capacity.

Although it looks like one charger is not being used the fact is that for the existing battery voltage the total charge current going in would be just about the same for one carrying (most of) the load as compared to both carrying less load on the next stage.

Make sure that the charger leads connect directly to the battery terminals and are not sharing any common ground or positive connections. It only takes a very small voltage drop over a ground buss to favor one charger.
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Old 10-05-2020, 08:28   #5
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Re: Premature Flotation? Two controllers one one bank

Victron smart mppt’s will sync. Must be the Bluetooth models...

I have 3 mppt’s that used to do exactly as you describe. Added the Bluetooth battery dongle (keeps the battery voltage constant for all the mppt’s) and latest firmware- now all sync as they should - and drop back as needed - all as if one large panel.

The controllers don’t need to be near the battery as well, or need any special wiring considerations as mentioned above.

There are other brands that do this, but I really like all my victron gear.
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Old 10-05-2020, 11:19   #6
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Re: Premature Flotation? Two controllers one one bank

Thanks two-rocks! I've also been really pleased with the Victron kit, but it can be hard to figure out all the different parts. Are you talking about the SmartShunt to get the controllers to sync?
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Old 10-05-2020, 11:38   #7
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Re: Premature Flotation? Two controllers one one bank

Quote:
Originally Posted by Off Trail View Post
Thanks two-rocks! I've also been really pleased with the Victron kit, but it can be hard to figure out all the different parts. Are you talking about the SmartShunt to get the controllers to sync?
It's the smart battery sense

https://www.victronenergy.com/access...-battery-sense
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Old 11-05-2020, 10:06   #8
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Re: Premature Flotation? Two controllers one one bank

Thanks. Looks like an inexpensive solution! Will give it a try.
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Old 18-05-2020, 17:01   #9
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Re: Premature Flotation? Two controllers one one bank

Just wanted to follow up. Installed the bluetooth battery sensor and it seemed to make the two controllers stay in lockstep. Whether I'm getting significantly more power will take some time to tell.

Kudos to Victron for developing such an effective and easy to use set of products! The latest version of their software seems to perform this function natively as well as report total power across multiple controllers. Very cool:

https://www.victronenergy.com/blog/2...ures-and-more/
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