Float Voltage too High?

[skynet]

I recently installed a Victron system in my camping trailer. I am using a Multiplus 1200 Inverter/Charger. The data indicates that the set Float voltage for all battery types is 13.8V. Other sources suggest that it is too high and should be 13.6V or lower preferably. Unfortunately, with this model, it's not a setting that can be modified. There is a dip switch setting for LifePO4. But, there is no way to set a specific float voltage. Of course, this is only a problem when connected to shore power. I can set the float voltage in the solar controller when charging from that source. The trailer has a conventional DC charger that is common in RVs, designed for Lead Acid and AGMs, and has a lower float voltage (13.6V I think). But, it also has lower voltages for charging than the Victron. I'm curious as to which is worse for the battery in the long term, the higher float, or the lower charging voltage.

Thanks

Multiplus 12/1200/50-16 120V Inverter/Charger
SmartSolar Charger MPPT 100/50
2x EcoFlow 100ah LifePO4 batteries. (12V 200ah in total)

 

[Q-Dog]

If you use a MK3-USB and a computer with Victron Connect you can change any setting you want, including float voltage.

5. Configuration

www.victronenergy.com

 

[skynet]

OK, I'll try that. Currently, I have that dongle, but it's connected to an RPi 'GX' that doesn't offer that ability. I'll try connecting from a laptop to the inverter directly with that dongle. Thanks for the tip!

 

[skynet]

Confirmed, that worked perfectly. I was able to set the voltage lower and change the charger priority to favor Solar. It looks like there are several settings that can be configured that way where the 'GX' doesn't have access to them. Thank you for pointing that out.

 

[timselectric]

13.8v is the lowest I would recommend for a 4s LFP battery.
Unless you are reaching fully balanced cells (above 13.8v), before floating.

 

[sunshine_eggo]

OK, I'll try that. Currently, I have that dongle, but it's connected to an RPi 'GX' that doesn't offer that ability. I'll try connecting from a laptop to the inverter directly with that dongle. Thanks for the tip!

With an RPi, you have the option to do remote VE.Configure3 with VRM.

You will need VEConfigure3 installed on a Windows PC.

From VRM select device list, Remove VEConfigure, download the file, edit it, save and upload.

VEConfigure3 also allows installation of Assistants if you want any specialized functions.

 

[skynet]

Where are you seeing that information? I haven't found any source of info that indicated 13.8V float for these batteries. Most of them stated no higher than 13.6V. Battleborn stated that a float charge was not even necessary for this type of battery at all. Not trying to be argumentative, it's just that 13.8V is higher than anything I have seen thus far. To be fair, Victron did have 13.8V as the default in this specific inverter/charger.

The Ecoflow specs don't indicate a specific voltage for float, but I did find an entry in the EcoFlow Blog that indicated between 13.5 and 13.6 V.

Guide to LiFePO4 Voltage Chart

Unlock the secrets of LiFePO4 battery voltage with our guide. Learn optimal usage, charging tips, and performance optimization. Click to explore.

blog.ecoflow.com

When I'm not camping in the trailer, I do tend to keep it connected to shore power. It has a continuous load of around 30-50 watts for my Starlink dish and router. It's sort of a UPS for my internet in the event of a grid power failure. Perhaps, I should not keep the shore power on continuously, and just let the system cycle.

 

[42OhmsPA]

13.8V ÷ 4 = 3.45V. Aka the balance start voltage.

 

[sunshine_eggo]

Where are you seeing that information? I haven't found any source of info that indicated 13.8V float for these batteries.

13.8V is on the high side for float; however, if one is trying to balance their batteries, it's not unreasonable.

Most of them stated no higher than 13.6V.

13.5V preferred as you can still get a little bit of low current over-charge at 13.6V.

Battleborn stated that a float charge was not even necessary for this type of battery at all.

Which is moronic without context.

The outcome of the above statement is more often that folks set a very low float voltage, and rather than the solar supporting their loads after the battery is full, the battery discharges after it's fully charged even when there's available PV. The other option is that folks set float the same as absorption which is not good for them, and can result in capacity loss due to lithium plating. The morons at Bigbattery did this on several of their models.

Float in context:

1. A LFP battery in storage does not need float and should not be put on float.
2. An LFP battery in a cyclic PV power system absolutely, positively needs a float voltage to ensure the battery is not discharged when PV is available to power loads. 3.375V/cell preferred.

 

[stuarts]

13.8V ÷ 4 = 3.45V. Aka the balance start voltage.

My BMS balances from 3.2V. Although due to it not being able to generate much balance current, I now have a full time balancer. Rarely see more than 5mV difference between cells.

 

[42OhmsPA]

My BMS balances from 3.2V. Although due to it not being able to generate much balance current, I now have a full time balancer. Rarely see more than 5mV difference between cells.

3.2V is way to low to start balancing LiFePO4, 3.42V minimum.