SOC during Float charge (First Post Please be gentle and forgive my ignorance)

[pmartin696]

OK, I recently completed installation on my Victron MultiPlus-II 12/3000/120-50 120/240V Charger/Inverter along with a SmartShunt 500A and 200AH of 12 LiPO batteries and Cerbo GX in my RV. I have not gotten a chance to install the PV system yet. Everything works great, but I am trying to tweak my settings. What I am noticing is that when I am in Bulk and Absorption, my batteries charge to 100% SOC. Once it goes to float, the parasitic drain of the 12v system (approx 23w) slowly drains the battery SOC down.. I haven't see how low, but I was wondering is this normal? Shouldn't the charger keep the battery at 100%? Is it possible I didn't correctly configure my SOC? If so what is the typical conditions to zero out the SOC? Is this maybe how the system protects the longevity of the batteries? Sorry for the rookie questions, just in all my research I haven't seen anything about this. I just want my system to be charged to 100% when in use so that if we loose or need power I'm not starting at 80% SOC. Any suggestion would be appreciated.

 

[Sojourner1]

Do you mean it drains the voltage down to the float voltage setting? If so that's normal. It should stay there while in this state. Are you charging by solor or 120v?

 

[RVLiFe]

You need to share a few more details. Namely, you need to tell us what your Bulk/Absorption and Float Voltage levels are set to in your SmartSolar. To answer your question. Yes, this is normal for parasitic drain to bleed off some voltage and reduce your SOC. The question is what is your Float voltage set to and your Re-bulk voltage offset. For example, if your Float voltage is set to 13.5V and your Re-bulk voltage offset is set to .20, expect your battery to get to 13.3V before it goes back in to Bulk mode. 13.3V is around 80% SOC. You can change those settings as you wish but there are some concerns with leaving a LiFePO4 battery at 100% SOC for extended periods of time.

 

[sunshine_eggo]

LFP float should be at 13.6-13.8V to maintain the battery above 95% SoC.

 

[pmartin696]

Do you mean it drains the voltage down to the float voltage setting? If so that's normal. It should stay there while in this state. Are you charging by solor or 120v?

120V right now... I'm wonder if its an issue with incorrectly setting SOC right after a Bulk charge? Typically do you let the batteries rest to set SOC?

 

[Sojourner1]

Depends, my system is in use 24/7/365.

Tell us your setting voltages and are you using the batteries or are they on stand by for long periods of time?

 

[RVLiFe]

13.5V is still 99% SOC and even if you get a little power draw to drop it below 13.5V, your SmartSolar should trickle it back up to maintain 13.5V. Report your numbers and we can help identify any issues. I have my Float set to 13.6V and my re-bulk to .20V. But my SOC rarely falls below 98% on a sunny day. Good enough for me and in most cases, its still considered 100% full. The higher state of the Bulk/absorption charge is there to ensure cell balance by the BMS but as far as most people are concerned, you could charge to 13.8V - 14.1V and be done. You aren't going to get much additional amperage above 13.8V anyway. Set your charged voltage setting in your battery monitor to .10V below the Bulk voltage.

 

[pmartin696]

You need to share a few more details. Namely, you need to tell us what your Bulk/Absorption and Float Voltage levels are set to in your SmartSolar. To answer your question. Yes, this is normal for parasitic drain to bleed off some voltage and reduce your SOC. The question is what is your Float voltage set to and your Re-bulk voltage offset. For example, if your Float voltage is set to 13.5V and your Re-bulk voltage offset is set to .20, expect your battery to get to 13.3V before it goes back in to Bulk mode. 13.3V is around 80% SOC. You can change those settings as you wish but there are some concerns with leaving a LiFePO4 battery at 100% SOC for extended periods of time.

Absorption voltage 14.60 V

Float voltage 13.80 V

Charge current 40 A

I just want to maintain 100% while its in use. I will be disconnecting when not in use.

 

[pmartin696]

Depends, my system is in use 24/7/365.

Tell us your setting voltages and are you using the batteries or are they on stand by for long periods of time?

Mine will not be 24/7, just for several weeks at a time while camping.

Currently set the charger at:

Absorption voltage 14.60 V

Float voltage 13.80 V

Charge current 40 A

 

[pmartin696]

13.5V is still 99% SOC and even if you get a little power draw to drop it below 13.5V, your SmartSolar should trickle it back up to maintain 13.5V. Report your numbers and we can help identify any issues. I have my Float set to 13.6V and my re-bulk to .20V. But my SOC rarely falls below 98% on a sunny day. Good enough for me and in most cases, its still considered 100% full. The higher state of the Bulk/absorption charge is there to ensure cell balance by the BMS but as far as most people are concerned, you could charge to 13.8V - 14.1V and be done. You aren't going to get much additional amperage above 13.8V anyway. Set your charged voltage setting in your battery monitor to .10V below the Bulk voltage.

Just an FYI I have not Setup my PV MTTP into the system yet.. I am charging 100% by the Multiplus.. Didnt have this issue prior to installing the multiple when I was using a 20A Victron LIPO charger and a Renogy Inverter. I'm sure its a setting, but I just want to ensure it wont drop cutoff voltage while on a trip.

 

[RVLiFe]

Mine will not be 24/7, just for several weeks at a time while camping.

Currently set the charger at:

Absorption voltage 14.60 V

Float voltage 13.80 V

Charge current 40 A

What is re-bulk voltage set to in your solar controller and what is the Charged Voltage set to in your SmartShunt or battery monitor?

 

[RVLiFe]

What is re-bulk voltage set to in your solar controller and what is the Charged Voltage set to in your SmartShunt or battery monitor?

It's definitely a setting then in your Multiplus and battery monitor

 

[pmartin696]

I'm pretty sure it has to do with this, but I'm going to have to watch 12 times, then sleep at a Holiday in before I fully grasp all the concepts..

 

[Sojourner1]

Just my opinion here bulk/ abs at 14.6 is just unnecessary.

Try setting the bulk/ abs to your voltage balance voltage or soc capacity reset. How long is your absorb set for? Your float is set a little high for me I use 13.6v but you could lower that to .4-.5.

While your home and not using the camper just turn-off the charger and trailer loads till the day before you plan to take the trailer out. If longterm storage drain batteries to 50-70% and turn all loads off but I would charge them up after a few or so months then deplete again. I might take a little time to learn your use and battery behavior.

 

[RVLiFe]

Just my opinion here bulk/ abs at 14.6 is just unnecessary.

Try setting the bulk/ abs to your voltage balance voltage or soc capacity reset. How long is your absorb set for? Your float is set a little high for me I use 13.6v but you could lower that to .4-.5.

While your home and not using the camper just turn-off the charger and trailer loads till the day before you plan to take the trailer out. If longterm storage drain batteries to 50-70% and turn all loads off but I would charge them up after a few or so months then deplete again. I might take a little time to learn your use and battery behavior.

I agree with everything @Sojourner1 says. 14.6V is unnecessary. If your really feel you need to charge that high due to the battery manufacturers recomendation, do it once every 3-6 months and you will be fine. That's what I do with mine.

 

[pmartin696]

Thanks guys, I will just keep playing with it.. I was just worried that I missed something...BTW battery manufacturer recommends:
The setting method of MPPT and inverter of 12.8V lithium iron phosphate battery pack is as follows:
Charging Charging Limit Voltage: 14.6V
Over Voltage Disconnect Voltage: 15V
Over Voltage Reconnect Voltage: 14.2V
Float Charging Voltage: 13.8V

 

[Sojourner1]

Are you using a 200ah dropin, which one?

 

[pmartin696]

Right now a CHINS LiFePO4.

 

[RVLiFe]

Right now a CHINS LiFePO4.

I have SOK 206Ah batteries. You don't need to be concerned with CHINS battery recommendations because they are just that, recommendation's and limits. I would stick with what everyone else on this board will agree with. Almost all LiFePO4 batteries operate the same anyway and there is definitely a general consensus on what people use for Bulk/Absorption/Float voltages. Stick with what the experts on here recommend and you will be fine. Get those settings narrowed down and you will be happy. If you can show us your settings of your MultiPlus we can verify that everything else looks good. We've all been in the same spot as you are in our understanding phase so you're not alone my friend! Report when you can!

 

[pmartin696]

This is the current settings on the Multiplus.. Im playing with them to get the best fit, but I would appreciate any expert/Experienced opionions.

Current configuration settings:
TAB: General
System frequency 60Hz
Shore current 50.0 A
Overruled by remote checked
Dynamic current limiter checked
External current sensor connected (see manual) checked
TAB: Grid
Country / grid code standard None: (feeding energy from DC to grid not allowed)
Accept wide input frequency range (45-65 Hz) checked
AC low switch mains off 105 V
AC low switch mains on 112 V
AC high switch mains on 135 V
AC high switch mains off 140 V
UPS function unchecked
TAB: Inverter
PowerAssist checked
Assist current boost factor 2.0
Inverter output voltage 120 V
Ground relay checked
Inverter DC shut-down voltage 10.90 V
Inverter DC restart voltage 12.00 V
Low DC alarm level 12.00 V
Do not restart after short-circuit (VDE 2510-2 safety) unchecked
enable AES checked
Load for starting AES mode 72 W
Offset for ending AES mode 48 W
AES type modified sine wave
TAB: Charger
Enable charger checked
Weak AC input checked
Stop after excessive bulk unchecked
Lithium batteries checked
Configured for VE.Bus BMS unchecked
Charge curve Fixed
Absorption voltage 14.60 V
Float voltage 13.80 V
Charge current 40 A
Repeated absorption time 0.50 Hr
Repeated absorption interval 1.00 Days
Absorption time 1 Hr
TAB: Virtual switch
TAB: Usage
Virtual switch usage Do not use VS
TAB: Assistants
TAB: Assistant ConfigurationAssistants not used