question

lorenzo-accaroli avatar image
lorenzo-accaroli asked

Float VS 100% SoC

Hello again everyone, finally I can monitor my system by VRM YOU CAN SEE HERE.

I have this brand new:

1) 2 SMARTSOLAR MPPT

2) QUATTRO 48/10000/140

3) 5EpzS floaded lead acid battery 775Ah(C5) 48 V

4) CCGX

SETTINGS:

a) 59.7 Vabs, 55.2V mantain (in MPPT);

b) 85% SOC when Bulk finish, 775Ah battery capacity, 1.00 charging efficiency (inVE.Config of Quattro)

I don't have BMS and the battery monitoring is performed by Quattro Inverter.

Now, in this couple of sunny days the battery reached abs voltage then performs a couple of hours in abs and then reach float but... when it is in float the SOC is 90%-93%. I would expect to read 100% on CCGX and VRM portal.

All is updated to last firmware.

What could be the problem?

battery charging
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3 Answers
bathnm avatar image
bathnm answered ·

This video might help answer your question. I know it's title is BMV, but there is a section at around 15:50, and might be related to synchronisation


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JohnC avatar image
JohnC answered ·

Hi @Lorenzo Accaroli

Your 85% SOC wbf is too low. With pv charging you get a softer start to the daily charge and things are already well under way by the time Abs is reached. Try 95%.

Now this may seem too high, and it would be if you retain the 1.00 CE. That's to-dream-of territory. Try 0.85 there, a more practical start point.

Make sure too that the mppt's Abs V is being seen by the Quattro charge settings, as that's where it happens. If necessary, drop the Quattro's Abs setting a little so the V actually registers that it's hit Abs. The GX doesn't communicate that.

If you need more help, post a screenshot of the SOC widget graph from VRM.

But your system is big enough to justify a SmartShunt (say), and with DVCC options it will complete your system, even allowing you to optimize your Abs times. Recommended.

The SOC you're using now is really an entry-level addon, and you deserve better.. don't you?..


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lorenzo-accaroli avatar image lorenzo-accaroli commented ·

@JohnC @Bathnm Thanks a lot!

I was wondering about the fact that an efficiency of 1.00 is not phisycally possible (even if you have a Carnot machine ;) ). I will follow your suggestions about SOc wheb bulk finshed and CE.

I know that something is missing in my system and once I am able to talk with the dealer I will ask for the possibilty to install SmrtShunt..

You can find attached the graph of SoC in the last three days (sunny days), Never goes above 91% and never below 70%.

cattura.jpg

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cattura.jpg (28.1 KiB)
Alexandra avatar image Alexandra ♦ lorenzo-accaroli commented ·

@Lorenzo Accaroli

Charging a battery is basically reversing the chemical reaction in it that released the energy.

The battery is only at 100% when the battery has reversed the reaction both on its plates and in the liquid around it. (even then it never fully reverses - hence battery degradation, sulphation and eventual replacement) It will never be 100% efficient - this is a physical impossibility as some energy is lost for example as heat. All chemical reactions have losses.

Lead acid has to be held in absorption stage longer than most other battery chemistries that is why 85% is its efficiency, whereas LifePO4 does not need to be held long in absorption state for balancing etc. hence the higher efficiency.

Float is technically the state the battery is in when it has reversed to the fullest extent able to the chemistry in the battery.

https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

The linked book is quite useful for learning more especially about lead acid charging

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lorenzo-accaroli avatar image lorenzo-accaroli Alexandra ♦ commented ·

Thanks @Alexandra I will defintely study the book!


Only two details @JohnC @Alexandra..

  1. my battery is 775Ah (C5). I read somewhere that the general setting in VE.configure-> "Enable battery monitor" capacity is related to C20.. i don't have this info
  2. My Quattro don't charge battery, it only works as inverter... Do I need to set Vabs anyway in VE.configure-> "Charger" settings?

Thanks

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JohnC avatar image JohnC ♦ lorenzo-accaroli commented ·

@Lorenzo Accaroli

#1. You really should try to find the C20 rating, as it may be as high as 900Ah, and your SOC figure will improve even more. And if you do end up with a real shunt, then multiple ratings are useful to get even finer accuracy in the settings. That's a lot of batt at 48V.

#2. Yes, so the Quattro knows it's reached Abs. But it may be ok as it is. What you expect to see is a SOC 'correction' when it hits Abs. (To the 85% or 95% you have set)

I'm not a big fan of this, as on admittedly rare occasions I've seen my Smartshunt SOC reach 100% without the mppt quite reaching Abs over a full cloudy day. It might be great using the full-on charge of the Quattro on mains supply, but solar delivers differently, and it's really not adequate for all conditions.

That said, your graph actually shows a typical tailing off under charge, to a peak which is showing probably about 8% lower than it really is. So your system is likely healthy, but the SOC making you feel bad.

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nickdb avatar image
nickdb answered ·

The inverters internal battery monitoring is poor and does not work well with a SOLAR/ESS environment.

We had to install external shunts to get it to properly synchronise.

The inverters just drifted too much and SOC tended to decay with time, and poor solar.

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