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marekp avatar image
marekp asked

2 signal BMS conected to EasySolar-II GX. What stops internal MPPT from overcharging when GX fails?

Recently I asked the question, how to stop external MPPT150/35 charging battery equipped with "2 signal BMS" connected to MP-II, when "external control" of said MPPT fails.

Got the answer but I also have EasySolar-II GX with internal MPPT 250/70.

How to solve the same problem with this internal MPPT?

How to stop its charging the battery when "external control" fails?

There is no way to connect to it ATC signal from BMS

MPPT ControllersBMSEasySolar All-in-One
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2 Answers
wkirby avatar image
wkirby answered ·

In that case, adjust the MPPT Voltage settings in the MPPT it's self to a lower value.
If there is a communications failure then the MPPT will revert to its internal settings. Lower value setting will then prevent continued charging at the upper Voltages of the charge cycle.

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marekp avatar image marekp commented ·

Hi @WKirby

What voltages would you suggest I use for 16 LFP batteries?

That would take care of too high voltage (maybe), but what if the temperature is below freezing and BMS sends the signal do not charge?


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Mark avatar image
Mark answered ·

I have not seen inside one of those Easysolar-II units to know how accessible the solar charger is, but it should just be a regular 250/70-Tr solar charger and that model has remote on/off terminals that you can simply wire into your BMS ATC signal for backup control.

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marekp avatar image marekp commented ·
Hi @Mark

In the other topic I was told that that on/off terminal is used by internal GX device.

What is Victron solution for the situation when GX device fails and there is noting stopping MPPT from charging battery when BMS is telling the system no to.


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Mark avatar image Mark ♦♦ marekp commented ·

Hi Marek,

Again I have not looked inside a Easysolar-II unit, but even if that is the case you should still be able to wire the BMS ATC signal in series with the existing wiring to achieve what you want.

Once there is an open circuit between the solar charger remote on/off terminals (or alternatively, if there is no HIGH or LOW signal), charging will stop, regardless of which device has triggered it.

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marekp avatar image marekp Mark ♦♦ commented ·
Hi @Mark ,

A you sure this is OK with Victron?

I would not want to find out later that I do not have warranty anymore.

Is there some kind of whitepaper, made by Victron, describing this connection?

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Mark avatar image Mark ♦♦ marekp commented ·

Hi Marek,

I think you will find that is the only way to achieve what you want.

If you want to be certain about any warranty implications, you might want to ask that question through the official channels (through your dealer) and await a formal response from Victron.

Providing the solar charger remote on/off terminals are easily accessible, I see this as fairly straightforward, but of course this is your unit, and you need to be comfortable and confident.

I don't know of any documentation describing this specifically for the Easysolar-II unit, but you can look at the the solar charger manual for information on how the remote on/off terminals function. In summary you can open/close the circuit between the two terminals or provide a HIGH or LOW signal direct to the respective terminal. See https://www.victronenergy.com/media/pg/Manual_SmartSolar_MPPT_150-60_up_to_250-70/en/features.html#UUID-20ac1af2-7925-4279-27cc-d14249d09217

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marekp avatar image marekp Mark ♦♦ commented ·
Hi @Mark ,

Thank you for the info. If it is so easy, as you say, I will try to implement this.

My BMS provides two dry contact signaling the ATC and ATD states.

And a general comment to Victron designers.

Shouldn't that connection be implemented by you in the EasySolar-II from the start?

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Mark avatar image Mark ♦♦ marekp commented ·

No problem Marek.

I think the first step is just to take a look to see how accessible everything is and what the current wiring arrangement is.

If there is already Easysolar specific wiring connected to the solar charger remote on/off terminal it might just be a single wire providing a HIGH signal (as opposed to a loop between L & H); in that case just make sure that voltage is compatible with your BMS ATC contacts and anything else you may have connected to the same BMS ATC contacts. Otherwise you may need to add another small relay or similar to provide isolation.

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marekp avatar image marekp Mark ♦♦ commented ·

Hi @Mark ,

I do not know where I can find info about it.

I found this info about relays in my BMS.

screen-shot-2021-07-01-at-12719-pm.png


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