Renogy lithium battery incompatibility issue

[fdsaevad]

I have two of these

12V 300Ah Core Series Deep Cycle Lithium Iron Phosphate Battery w/Self-Heating

that I had pro installed inside a van with a Victron Multiplus-II

I am charging them either with an exterior outlet in the parking lot at my work (through the day while I work, charging at 7amps) or with a generator I have attached to a hitch mounted cargo carrier behind the van (charging at 28amps).

The outlet at work is not reliable and often turns off throughout the day, so often I use the generator.

My issue is that generally I cannot tell what voltage the batteries are at, and I am worried the incompatibility between the two will eventually damage the batteries.

I have both the bluetooth victron connect app on my phone, and the usb version to my laptop (which often makes the mouse jump around crazy on my laptop).

The VictronConnect app usually always shows 85% capacity even when in the 12v range.

When I return to the van after working, if it is still charging, it shows the battery voltage jumping around between 13v and 15v all crazy, while still in the 2nd stage of absorbtion, with the wattages in/out doing weird things too. (see vid) It shows 85% full, but I know they are full because they end up at 13.6 after unplugging.

Twice I returned and the voltage had gone from above 13v to 12.4 (it had been reduced weirdly to almost dead throughout the day). Often times the outlet looses power because they use the line to plug in the trucks when not in use and it seems unreliable generally.

I know the voltage the victronconnect app is reading is generally not accurate, and since the charger cannot read the batteries correctly, I fear the batteries eventually become instable because they are charging them wrong (not going into the 3rd stage of absorption, shoving power in there when they’re full etc, or doing other weird things).

I just charged the batteries with the generator at 28amps for a couple of hours. VictronConnect now shows the batteries at 13.25V, but it never went into the 2nd stage of absorption, but I did notice the wattage coming in when from 2400w to 1800w shortly before I shut down the charger.

… Is there a way to always read the battery voltage without the VictronConnect app (which doesn’t seem to read it properly for whatever reason)?

Have a multimeter permanently attached to the batteries?

Is there any possibly of damage or injury by continuing to use the charger in these ways?

Is there any changes to the settings that I should do? I have the latest firmware on everything. I have the float voltage at 14.4 (as per Renogy), and the other setting above that (in the app) is always 0.1v above the float voltage, so it’s at 14.5v. The one setting at ‘adaptive’, I forget which setting that is.

I have been talking to both Victron and Renogy support for weeks with no result.

I have attached a couple of videos of the charger doing weird things after returning to the van after work, and one other video of it starting to charge.

Why is a new user restricted to 5 uploads lol.

[fdsaevad]

[Ludo]

As the heater current doesn’t run over the smartshunt your’e flying blind.

[pwfarnell]

Have you set up battery monitoring in the Multiplus otherwise it has no idea what it is measuring. Let us se your battery monitor settings. Secondly a Smartshunt would be better but the heaters can mess with this as noted above.

[fdsaevad]

Thank you for replies. All settings I use (re battery monitoring) I have posted above in the Multiplus2 settings. I’m not sure if you are referring to some other type of monitoring

I need a bit more clarification, please forgive my ignorance.

I assume a smartshunt is preferred so as to also measure the heater and fan usage, as these are not run through the inverter,

But if the Multiplus2 is a multimeter (which is how it shows the voltage of the batteries in the victronConnect), what does it matter how much power is being used outside the inverter by the heater/fan, if the multimeter (Multiplus2) is accurately showing the voltage of the batteries? If it knows 13.6v is full, 12.6 is empty, so 13.1v is 50% no?

If the battery voltage is not reading correctly, or the Multiplus2 cannot ascertain how full it is for whatever reason, how does the charger know when to stop pushing power in there? Are the batteries like a balloon that will blow when too much air is pushed in?

Is my issue not a common one with every single van build? If so, why is the answer as to how to set this up not apparent and obvious?

If I didn’t have a heater, would the Multiplus2 being showing the exact % SOC and be going into the correct absorption stage while charging? It is not doing that currently, so I am concerned the batteries will become unstable due to the Multiplus2 not being able to read them for whatever reason and charging them weirdly.

Every day while charging the victronConnect is showing something new and different, please advise

[Ludo]

The problem is that there is no reliable coincidence between voltage and soc for a lithium battery.

[fdsaevad]

Is the voltage of the batteries shown in the victron connect app at least accurate? (My mobile Bluetooth app shows slightly different voltage than the USB computer app).

Does everybody else’s victron charger go into the proper stages of absorption?

If so, do you also have a bunk heater?

Do the stages of absorption matter?

If the charger is inaccurately reading the batteries, what determines when the charger stops charging, and or what if the charger does not stop charging?

[pwfarnell]

I missed the small bit of the image with the battery settings. One change you should make is set the capacity at the end of bulk to perhaps 95% as lithium usually only go into absorption for a limited SOC.

The voltage on the Multiiplus 2 is usually accurate AS LONG AS you have good wiring, isolators and fuses in your DC circuit but you can still get voltage drop resulting in higher indicated voltages during charging.

The SOC calc is not voltage based, it counts the current vs time to calculate Ah in and out and uses the end of bulk to set a known figure. If you have a lot of voltage drop or intermittent loose connection, the charger thinks the batteries are at 85% before they actually are, meaning the SOC is too high.

A SmartShunt would get around these issues.

Check your battery and inverter voltages when charging with a multimeter to see how different they are. Check your wiring. Check if the battery is stopping charge on a high cell voltage using the battery Bluetooth.

[fdsaevad]

Thank you. So my SOC is wrong all the time because I use a bunk heater and don’t have a smartshunt, but the voltage is likely correct, as I had the rig installed by pro commercial truck outfitting company.

I assume every Victron sold for van conversions is bought with a smartshunt, and somehow I missed this memo; the need for a smartshunt along with an inverter/charger not being recommended by Victron, the battery company, the company installing the rig, or anywhere previous on the internet during all of my research.

So since the charger charges the battery based on the SOC, and the SOC is wrong (the SOC is less than the charger thinks it is due to heater running 8-10hrs a day (Canada)), I guess the batteries will never reach true max capacity, since the inverter will stop the charge early based on the faulty SOC. I just need to go by the voltage for now until I can install a smartshunt.

Should be an option to base charging on voltage maybe, not seeing the advantage of it being otherwise.

Or at least sell the smartshunt as part of the inverter/charger.

Or at least mention in the manual - “Your unit will not charge right if you have devices being charged by the batteries outside the inverter without a smartshunt”. I’ll write to victron IMMEDIATELY to let them know

I’ll also mention it to the 6 customer service people I talked to over the last 2 months.

Basically this is a critical piece of information that everybody should know about, finally we know why chargers are doing weird things. Might write the local news to help spread the word

[pwfarnell]

The SOC is not used to control the charging, the charging control is voltage based, the SOC is just an indication so a wrong SOC has no impact on the charging. If you have high voltage drop that will affect charging.

The charger knows nothing about DC loads, that is why you need a SmartShunt. It is basic electrical knowledge. If your battery heaters are internal to the batteries and can run off the battery power then they will not show on a SmartShunt even, you need to work off the battery SOC, in that case.