My battery monitor says '100% charged' all the time

[PWLexorOwner]

Hi, I've been full-timing in my 2016/17 Pleasure Way Lexor for about 1.5 months now. I noticed something with the battery monitor while dry camping and wanted to see if anyone has experienced a similar situation.

The Lexor came with ducal 100AH Eco-Icon lithium batteries and one solar panel (95w) and there is a Go Power monitor. The setting on the monitor does not have a 'solar' option and it is set to 'AGM'. I can see the battery percentage, voltage, and the ampage the solar panel is charging.

The monitor shows '100%' all the time. At first, I thought that the solar panel is doing a great job that the batteries are 100% full all the time. I then dry camped for 2 nights and didn't drive the van and didn't use the generator. While I didn't use the power much (inverter to charge my phone and laptop, LED lights, fantastic fan) for 2 days, I noticed that the battery monitor remained 100% while the voltage dropped to 12.9V.

Is it even possible that the batteries were actually charged 100% the entire time? I used lights and fan at night and the monitor stayed 100%. If the monitor is not giving me the correct reading, is this normal with Pleasure Way vans? Also what voltage is considered 'low'? I don't know when I need to turn on the generator.

TIA!

[rowiebowie]

Welcome to the forum PWLexorOwner!

Sorry, I know nothing about your monitor or lithiums, but someone here will know.

[markopolo]

The monitor is likely meant for use with lead acid batteries and not for use with lithium batteries. A lead acid battery at 12.8V would be seen as fully charged (100%) by a basic monitor but a LiFePO4 (lithium) battery at 12.8V (at rest) probably only has about 20% of its charge left.

[jon]

I had this same issue. It could be two items.
1. A state of charge meter requires a shut with all the loads connected to the battery side of the shunt with no loads going directly to ground without traveling through the shunt.
2. My Victron manual said to set the 100% charge for lithium's with solar to 14.1 volts. That was actually less than 14.(4 or higher) volts that are actually 100% charged but it says it keeps the solar panels from resetting the meter.
I don't know if it helps but that's what I did.

[PWLexorOwner]

Originally Posted by markopolo

The monitor is likely meant for use with lead acid batteries and not for use with lithium batteries. A lead acid battery at 12.8V would be seen as fully charged (100%) by a basic monitor but a LiFePO4 (lithium) battery at 12.8V (at rest) probably only has about 20% of its charge left.

Thank you! I'm afraid that that might be what's happening as the battery type is set to 'AGM'. I bought it used but it's a Pleasure-Way van. I don't understand why they didn't install a monitor that works with lithium ion batteries.

[PWLexorOwner]

Originally Posted by jon

I had this same issue. It could be two items.
1. A state of charge meter requires a shut with all the loads connected to the battery side of the shunt with no loads going directly to ground without traveling through the shunt.
2. My Victron manual said to set the 100% charge for lithium's with solar to 14.1 volts. That was actually less than 14.(4 or higher) volts that are actually 100% charged but it says it keeps the solar panels from resetting the meter.
I don't know if it helps but that's what I did.

Thank you. It sounds like it's more than what I can handle on my own

[BBB]

The manual for our 2019 Lexor TS says AMG setting works for the lithium batteries. After 3 months, I’m still trying to figure out the solar/battery panel.

[K Pearce]

I bought one of these to monitor battery health on my 2015 RT CS.
https://www.amazon.com/Battery-Charg.../dp/B07422ZPT4
Best and simplest tool I have ever seen. I too am not confident in the Roadtrek panel. This gives me great reasuance in my system especially when boondocking.

[wpshivers]

Originally Posted by markopolo

The monitor is likely meant for use with lead acid batteries and not for use with lithium batteries. A lead acid battery at 12.8V would be seen as fully charged (100%) by a basic monitor but a LiFePO4 (lithium) battery at 12.8V (at rest) probably only has about 20% of its charge left.

As markopolo stated, the percentage SOC (State Of Charge) reading you see is based on the voltage levels of a lead acid battery (Wet Cell or AGM) to calculate the SOC, which are much lower than the voltage levels for Lithium batteries.

An AGM centric battery meter will show a Lithium battery to be at 100% charge pretty much 100% of the time. This is true of most battery meters meant for automotive use on the market today. They assume you have a standard automotive style Lead-Acid battery, Including meters mentioned in this thread that give a percentage amount for the SOC or display a Red, Yellow or Green LED to indicated battery status.

Best to just read the actual voltage level number, ie; 12.9vdc, and compare it to the chart below for a Lithium based battery's SOC.

I have a Roadtrek CS Adventurous with four EcoTrek 200 Lithium batteries and have found the chart to be close enough for determining the SOC of my Lithium based battery bank... I believe it will be pretty close to you voltage levels also for a close enough SOC...



EcoTrek_Voltage_State_of_Charge_Chart.jpg

[svIntuition]

We spend about six months a year in our 2018 Lexor. Lots of folks have questions about the electrical system, so I wrote a blog post sharing what we have learned.

https://www.svintuition.com/2019/03/...e-this-on.html

[RossWilliams]

Voltage is a very poor way to evaluate state of charge for lithium batteries since the voltage almost flat lines after an initial drop and then drops rapidly when the battery reaches about 20% remaining charge. You can see that in the chart posted above.

Moreover, voltage is hard to use and not very accurate for any battery that is in actual use. To get an accurate measure of voltage requires the battery to be rested for a day and even then the voltage measured may not accurately reflect its actual state of charge depending on the conditions. So its not clear getting a more accurate reading of voltage will give you any more accurate a measure of state of charge. The vagueness of "idiot lights" may just accurately reflect the uncertainty around any measure.

The solar charger adds to this confusion for our Roadtrek. Whenever we are in the sun, the voltage reading reflects the voltage the solar panel is putting into the battery, not what is available. Roadtrek labels this idiot light level "charging", but it is the same as when the battery is fully charged.

So two things may be going on:

1) You are reading the voltage during the day while the battery is being charged by your solar panel.

2) Your "idiot lights" are set to reflect 100% charged while voltage is anywhere in the flat part of lithium batteries' voltage curve.

There is an alternative way to monitor lithium battery state of charge that involves tracking actual usage. I am not sure how practical that is for an RV.