question

schaka avatar image
schaka asked

Cerbo/Venus GX - Set maximum charge level, e.g. 90 % SOC

Hello together,

my config is:
- 3x Multiplus 5000
- 3x MPPT 250/100
- Cerbo GX
- BYD LVL 15.4
- 45 x Sunrise Energy SR-M660340HL -> 15,3 kWp

- In plan: Fronius Symo on AC-Out

Here is my question:
I would like to limit the maximum charge level. For example, to 90% SOC. I can not find this setting in cerbo gx. Is it possible that this setting does not exist at all? Why? Many other manufacturers have this option. I think this would be a good option to save the battery in the summer. Since peaks occur here from time to time. And the battery is loaded beyond its limit. Especially if you plan to add another inverter. Even if this adheres to the 1.0 rule. Here it would be better if the battery still had reserves. And from time to time, the battery could charge to 100% to balance the cells.

Are there any efforts on the part of Victron Energy here?

Thanks for help.

greetings from germany
from an enthusiastic Victron user
Schaka


cerbo gxbattery chargingLithium BatteryCCGX Color ControlSOC
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3 Answers
schaka avatar image
schaka answered ·

@Victron Support: Why no answer?

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kevgermany avatar image
kevgermany answered ·

This isn't a victron support site. It's a site for users to help other users. Occasionally someone from Victron posts. I, possibly others, refrained from answering originally because you specifically asked for a Victron reply.

But as you've found, there isn't a way of limiting by SOC. For LiFePo4 it's not needed. If you want to do it, adjust voltage settings on the charger, but be aware that LiFePo4 batteries need a regular full charge to keep the cells balanced.

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baxter avatar image
baxter answered ·

Limiting SOC for Lifepo4 is definitly a usefull function an increases cell lifetime. Best operating window would be 10% to 90%. I do not know why Victron is still not including this function at least in DVCC/ESS controlled systems. Using the charge voltage is useless as the voltage does not reflect the SOC during a wide range of the charge curve.

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nickdb avatar image nickdb ♦♦ commented ·

Because in an ESS it is mostly irrelevant. The system is in constant charge/discharge and will inherently spend most of it's life in an "optimal" range.

The specs, life and warranty of your batteries are based on this typical cycle, so hobbling your system by wasting 20% is a needless waste of money and is ultimately counter-intuitive.

An ESS and an EV have different usage patterns and requirements, so what is good for one is not necessarily good for the other.

It is also not just about individual cells, manufacturers want their packs regularly fully charged so they are balanced correctly so the battery as a whole can have a good lifespan. Some insist on batterylife being enabled for this purpose.

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kevgermany avatar image kevgermany ♦♦ nickdb ♦♦ commented ·
@Baxter

The 20-80% range comes from normal lithium ion cells like the ones used in phones, tablets etc. Many web sources assume incorrectly that this applies to LiFePO4.


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baxter avatar image baxter kevgermany ♦♦ commented ·

Wrong. Pls look at the datasheets of prismatic lfp cells, like EVE

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baxter avatar image baxter kevgermany ♦♦ commented ·

According to EVE the SoC window is 10 to 90 for prismatic LFP cells, so 80% DoD

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baxter avatar image baxter nickdb ♦♦ commented ·
  1. Again, recommended SOC window eg for EVE cells is 10 to 90. Why operating cells outside the vendor specification on a daly basis. Makes no sense to me. Regular top balancing we are talkin about once a month (depends on cell quality)
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nickdb avatar image nickdb ♦♦ baxter commented ·

The “window” is relative to their rated capacity based on a defined standard charge/discharge. This is from 3.65V down to 2.5V. Most packs don’t run them that high or down that low (10 year guarantees don’t just happen by magic), so they have effectively derated it’s capacity. So you may be charging to 100% but relative to derated capacity.


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