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Calibrating the Furrion Battery Monitor
Calibrating a Furrion Battery Monitor has been discussed in many threads on this forum. Having had time myself to work through the process "hands on" I now believe I understand the why behind the what. The purpose of this post is to convey that information to you along with my personal .02 (which of course you can take or toss).
The first link to the Furrion manual was provided by SoccerDad here: https://gdrvowners.com/forum/operati...0299#post80299
I've attached the PDF to this post, too, for your convenience.
IM-FEN00032_V3.0_EN-1.pdf
Bottom Line Up Front: The meter measures the amperage going into and out of the battery bank and also measures the battery's voltage. That's all the meter does (via the shunt). Period. The calculated amp hours left in a battery is determined based on the flow of amperage and the capacity of the battery bank you manually enter in the meter. The 100% SOC voltage is also based on the voltage value of the battery when the 100% SOC is set.
To repeat: to calculate a percentage ("State of Charge") the meter must know the capacity of the battery bank.
To clarify, imagine you're trying to determine how much water you can carry but have no idea of your bucket's capacity. How would you determine the amount of water your bucket can hold? Empty it out, then fill it up using a flowmeter. Then you know your bucket's capacity. If it's 5 gallons, you know when 2.5 are used and that the bucket's "SOC" is 50%.
This is exactly what the Furrion's instructions are suggesting the owner do with their battery. Empty it, set an amp hour capacity in the meter above what you think it will actually be in reality, then see how many amps it actually takes to fill the battery back up so the initial amp hour value entered in the meter can be "tweaked" to the actual number of amps the battery absorbed while charging.
IMO the steps are clumsy and, in the case of discharging the battery bank, ill-advised. (Feel free to disagree.)
So how would I "calibrate" the Furrion Battery Monitor if I had one? (What I would NOT do is discharge my battery to 0% SOC.) Remember--this is just one person's opinion (mine).
1) Get the state-of-charge information for my specific battery bank from the OEM. I'd want a voltage-to-% chart along with a specific amp hour capacity (not reserve capacity).
Example: A Trojan 12V 24TMX's datasheet can be found here. The datasheet shows that at 100% State of Charge (SOC) the battery voltage ("resting") is 12.73V. 50% is 12.1. Every battery may have a unique SOC profile, thus knowing your battery's profile must be known.
The battery's amp hour capacity depends on the discharge rate, so (arbitrarily) the 10 hour specification from the datasheet was chosen which is 78 amps.
2) Assuming a single Trojan 24TMX in the setup, ensure the battery is fully charged (by monitoring the "resting" voltage as measured by the battery monitor). Once the battery is fully charged, set the SOC percentage (using the method in the instructions) to 100%.
3) Manually set the amp hours (as spelled out in step 6 of the instructions) to 78. (What if there's two of these batteries in parallel? Set the value to 156, which is 78x2.)
Now, through regular use and observation, compare the SOC percentage against the resting voltage shown by the meter. If you notice a disparity (either high or low) based on the datasheet values, tweak the amp hour capacity up or down. In most cases the value will be tweaked down, especially as the battery ages. You may need to reset the % to 100% when the battery is fully recharged after changing the amp hour capacity value.
The key is to learn the relationship between the voltage being displayed and the state of charge percentage. By tweaking the amp hour capacity numbers the % displayed will be more accurate. Suggestion: tape a copy of your battery's SOC chart near the monitor so there's a quick reference to compare the voltage to the SOC % on the chart and meter.
Yes, this methodology will work with any battery type including lithium. There's no "special setting" for a lithium battery.
Can you set the capacity setting to 1/2 of the actual value so the meter shows 0% when it's at 50% (a common practice for those with lead-acid)? Sure. Won't hurt a thing as long as YOU understand how the meter is set up. Me? I'd set it up for the full capacity and work from there--much easier to do the math in my head when "tweaks" are required later down the road. But do as you want--no harm, no foul.
I tried to keep this short and wish I had a Furrion Monitor so I could make a short video. This topic is a possibility as an "Owner to Owner" seminar at the National Rally. I'd truly appreciate questions and inputs to help assemble the presentation.
If there's factual errors in this post, I will edit and correct as soon as they are identified.
Howard
The first link to the Furrion manual was provided by SoccerDad here: https://gdrvowners.com/forum/operati...0299#post80299
I've attached the PDF to this post, too, for your convenience.
IM-FEN00032_V3.0_EN-1.pdf
Bottom Line Up Front: The meter measures the amperage going into and out of the battery bank and also measures the battery's voltage. That's all the meter does (via the shunt). Period. The calculated amp hours left in a battery is determined based on the flow of amperage and the capacity of the battery bank you manually enter in the meter. The 100% SOC voltage is also based on the voltage value of the battery when the 100% SOC is set.
To repeat: to calculate a percentage ("State of Charge") the meter must know the capacity of the battery bank.
To clarify, imagine you're trying to determine how much water you can carry but have no idea of your bucket's capacity. How would you determine the amount of water your bucket can hold? Empty it out, then fill it up using a flowmeter. Then you know your bucket's capacity. If it's 5 gallons, you know when 2.5 are used and that the bucket's "SOC" is 50%.
This is exactly what the Furrion's instructions are suggesting the owner do with their battery. Empty it, set an amp hour capacity in the meter above what you think it will actually be in reality, then see how many amps it actually takes to fill the battery back up so the initial amp hour value entered in the meter can be "tweaked" to the actual number of amps the battery absorbed while charging.
IMO the steps are clumsy and, in the case of discharging the battery bank, ill-advised. (Feel free to disagree.)
So how would I "calibrate" the Furrion Battery Monitor if I had one? (What I would NOT do is discharge my battery to 0% SOC.) Remember--this is just one person's opinion (mine).
1) Get the state-of-charge information for my specific battery bank from the OEM. I'd want a voltage-to-% chart along with a specific amp hour capacity (not reserve capacity).
Example: A Trojan 12V 24TMX's datasheet can be found here. The datasheet shows that at 100% State of Charge (SOC) the battery voltage ("resting") is 12.73V. 50% is 12.1. Every battery may have a unique SOC profile, thus knowing your battery's profile must be known.
The battery's amp hour capacity depends on the discharge rate, so (arbitrarily) the 10 hour specification from the datasheet was chosen which is 78 amps.
2) Assuming a single Trojan 24TMX in the setup, ensure the battery is fully charged (by monitoring the "resting" voltage as measured by the battery monitor). Once the battery is fully charged, set the SOC percentage (using the method in the instructions) to 100%.
3) Manually set the amp hours (as spelled out in step 6 of the instructions) to 78. (What if there's two of these batteries in parallel? Set the value to 156, which is 78x2.)
Now, through regular use and observation, compare the SOC percentage against the resting voltage shown by the meter. If you notice a disparity (either high or low) based on the datasheet values, tweak the amp hour capacity up or down. In most cases the value will be tweaked down, especially as the battery ages. You may need to reset the % to 100% when the battery is fully recharged after changing the amp hour capacity value.
The key is to learn the relationship between the voltage being displayed and the state of charge percentage. By tweaking the amp hour capacity numbers the % displayed will be more accurate. Suggestion: tape a copy of your battery's SOC chart near the monitor so there's a quick reference to compare the voltage to the SOC % on the chart and meter.
Yes, this methodology will work with any battery type including lithium. There's no "special setting" for a lithium battery.
Can you set the capacity setting to 1/2 of the actual value so the meter shows 0% when it's at 50% (a common practice for those with lead-acid)? Sure. Won't hurt a thing as long as YOU understand how the meter is set up. Me? I'd set it up for the full capacity and work from there--much easier to do the math in my head when "tweaks" are required later down the road. But do as you want--no harm, no foul.
I tried to keep this short and wish I had a Furrion Monitor so I could make a short video. This topic is a possibility as an "Owner to Owner" seminar at the National Rally. I'd truly appreciate questions and inputs to help assemble the presentation.
If there's factual errors in this post, I will edit and correct as soon as they are identified.
Howard
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