question

lucasnowak avatar image
lucasnowak asked

LiFePO4 Quattro charging doesnt go to float

Hi all!

A bit strange thing to me, but probably an easy riddle for some of you guys.

The installation has 60kWh of LiFePO4 batteries and 3x Quattro 8000 (three-phase install).

When the system is charging, it always stays in Bulk mode, never gets into float or absorption. That means that always whenever the SoC is below 99% and ready-to-charge relay is set Quattros drain abruptly full power to charge the batteries. The configurator is set for default LiFePO4 settings - bulk should stop at 95% of charge and charging current is limited to 80A per Quattro, which gives us 240A => C/5 (60kW/50V= 1200A). See attachment - charging current is set to 80A, not 52A as per picture.

Questions, is that a normal that once "ready-to-charge" is set, Quattros push all power to quickly charge it up? Or should it pass throu float mode instead. If such, where the issue may be based on?

On the picture you can see the green spikes (current) and the battery voltage (red). You can see the loading process - positive spikes and peak shaving - the negative spikes.

battery chargingLithium Battery
1565768078938.png (1021.8 KiB)
1565769006015.png (154.5 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

3 Answers
Mike Stasko avatar image
Mike Stasko answered ·

@LucasNowak Your Float value seems too low. I don't have a Quattro but I do use the 250/100 MPPT charger & BMV-712 for my battery bank, Chevy Volt pack 31KWH. My Absorb is 48.6 and Float is 48.4 with the Absorb time set to 1hr.. Usually I do not hit 100% SOC until I go into Float mode, based on the BMV712 setting (48.4). Note - Volt batteries are 12s (3.7*12=44.4v is nominal).

I wonder if the 2.8V difference between the two is too great?.?

Good luck.

2 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

adev avatar image adev commented ·

Your float and absorb settings are far too low also for 48v system, I expect that was a typo but that’s a dangerous mistake to be making here ;)

The default victron connect settings for a 48v LiFePo4 battery are: absorb 56.8v, max 6 hours; float 54.0v.


have a look at this very informative piece on LLiFePo4 charging parameters...

0 Likes 0 ·
Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ adev commented ·

Please don't mix up settings for different batteries, this topic is about a 16s LiFePO4 battery
Mike is talking about 12s Li-ion batteries

different chemistry, different voltage, different charge curves.

0 Likes 0 ·
lucasnowak avatar image
lucasnowak answered ·

@Mike Stasko I think the battery packs are quite different on our installations. I've got Victron LFP ones giving 48VDC voltage. The recommended voltages are 53,2/55,6V float/absorption, which is around the values I've got programmed. But true, maybe the difference between those two is too wide - could Victron help out?

After reading the manual again I've notices that the assistant needs to be set to "Disable charger", NOT "Force to float". Would that be the cause of having only Bulk mode only? I've got the Lynx Ion BMS and the manual states those assistant settings.

What I am missing then?




1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Mike Stasko avatar image Mike Stasko commented ·

@LucasNowak

Sorry. I would not know the answer.

0 Likes 0 ·
Mike Stasko avatar image
Mike Stasko answered ·

@Daniël Boekel (Victron Energy Staff)

Correct. The number of cells (12, 13, 14, etc) regardless of stated battery voltage, 24v, 48v will determined a charger’s setting. Critical this is taken into consideration if you are not using an off the shelf battery.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Related Resources

Additional resources still need to be added for this topic