HV Battery Calibration Procedure

First, I'll mention there is no official procedure from Ford for battery calibration. However I think it helps to do this periodically, especially in vehicles that don't get the pack exercised very regularly. Some Mach-E owners have reported up to a 5% improvement in battery State of Health (SoH) after performing this procedure. As in most of my articles, nerd content warning applies here, just focus on the procedure below if you aren't one.

2026 Update: Ford now recommends charging LFP packs to 100% at least once every two weeks (previously it was once a month). Following the full procedure below will further enhance accuracy.

2024 Update: Separate instructions have been added for LFP (Lithium Iron Phosphate) packs.

Background: Like virtually all lithium-ion battery systems, the Mach-E uses a battery management system (BMS) to estimate the amount of energy in the battery pack, which is used to display the state of charge % and the range. The system does a pretty good job, but over time the calibration of the BMS can drift, especially in vehicles where the battery is always kept in the middle of the range (which is good battery practice). This can cause the capacity estimate to become more inaccurate with time, which affects the displayed % and range. Most BMS systems are programmed to be conservative, which means the capacity and range is typically underreported when the BMS has drifted. Similar battery calibration procedures have been successful in improving range estimates in other EVs such as Teslas.

Please Note: The displayed range on the Mach-E GOM is heavily affected by driving habits and outdoor temp, BMS calibration is a much smaller factor compared to these. Do not do this just because your range dropped suddenly, that's almost certainly because the outdoor temp decreased and calibration will not help that. Range drop due to temps below 55ºF is perfectly normal has been well documented elsewhere on the forum.

Benefit: You may see a 0-5% capacity/range indication improvement (not verified or guaranteed) after a BMS calibration.

It's important to understand that performing a BMS calibration does not physically restore lost battery capacity (which is gone forever), it merely updates the computer estimate of capacity only so that it is more accurate. The battery has whatever intrinsic capacity is currently has regardless of what anyone says, does, or thinks (including the GOM), so you could argue it's best to not think about BMS drift and just go about life unless you are concerned with accuracy.

I recommend you perform this procedure every 6 months, especially if you never charge to 100%. Every spring and fall is a good time. It's not necessary if you take regular trips where you hit extremes of charge.

Which pack do I have?

• All Extended Range packs (and GTs) are NCM type
• The LFP pack (72 kWh) is only found in MY 2023.5 and newer Standard Range Mach-E's
  • If the 8th digit of the VIN is a 4 or 5, it's a Lithium Iron Phosphate (LFP) battery
  • Any other digit or letter besides 4 or 5 means NCM battery

Procedure (NCM packs):

1. Charge the vehicle to your normal level (e.g. 90%).
2. Drive the vehicle (without charging) until the battery is down to 5% or less.
3. Park the vehicle and let the battery rest for at least 5 hours (preferably overnight)
4. Level 2 charge all the way to 100% in one session without interruption.
5. Leave the vehicle plugged in and let the battery rest for 3+ hours after 100% is reached.
6. (Optional) With a scan tool, read the kWh to empty and state of health parameters.
7. Drive without charging until battery is below 50% (10% recommended)
8. Charge the vehicle back up to your normal level.
9. Repeat if desired.

Procedure (LFP packs):

1. Charge the vehicle to 100%.
2. Leave the vehicle plugged in and let the battery rest for 3+ hours after 100% is reached.
3. Drive the vehicle (without charging) until the battery is down to 40%.
4. Level 2 charge all the way to 100% in one session without interruption.
5. Leave the vehicle plugged in and let the battery rest for 3+ hours after 100% is reached.
6. Drive the vehicle (without charging) until the battery is down to 10% or less.
7. Park the vehicle and let the battery rest for at least 5 hours (preferably overnight)
8. Charge the vehicle back up to 100% in one session without interruption
9. (Optional) With a scan tool, read the kWh to empty and state of health parameters.
10. Repeat steps 5-9 if desired.

It's fine if you do this over a period of days, just observe the steps and don't charge in between. FYI it can take several hours to charge from 95-100% if the pack is out of calibration, so plan for an extra long time to reach 100%. Do not use remote start or preconditioning during calibration. The rest periods (bold) at low and high SoC are very important to wait for so the BMS has time to read all the cell voltages accurately. It's best to do this when the temperatures are moderate (60-85ºF) in the spring and fall. Try to drive moderately, avoid heavy accelerations while calibrating. Parking the vehicle overnight at 10% will not harm the battery, the cell voltages are still plenty high so nothing detrimental will happen. After you charge to 100% and wait several hours, you do want to drive the vehicle within 24 hours so it doesn't sit at 100% for longer than necessary since that is stressful on the cells.

More Background: The BMS assumes the average user will charge up to 100% occasionally for trips, and also drains the battery below 20% periodically. When this doesn't occur regularly, the BMS drift can increase due to the very flat nature of the lithium discharge curve (see below figure). It's very difficult to estimate the actual state of charge in the 10-60% region, it could be off by upwards of 10% based off voltage alone. The BMS employs coulomb counting (via a current sensor) to improve the accuracy here, but that's the aspect most affected by drift since small errors in current measurement accumulate over time. Therefore spending some time above 90% and below 10% where the voltage curve has the greatest slope is important for the BMS to get a good read on the battery SoC. Some cell balancing will also occur during the rest periods at high and low SoC, which improves the estimates of total pack capacity.



The capacity error is even worse with LFP batteries, which have an EVEN FLATTER voltage curve than NCM. This is why they must be charged to 100% regularly. Ford recommends charging the LFP pack to 100% at least once a month, I recommend every week or two. Failure to charge a LFP to 100% for several months can result in you running out of energy MUCH sooner than expected (e.g. you might see a sudden drop from 40% to 1%).

Last, a reminder that outside of calibration and trips, it's good practice to always keep the battery between 20-90% for maximum longevity, and charge to the lowest level you need for everyday use. Users that follow good charging practices actually have the most need to do a battery calibration periodically as explained above.

So a possible increase in Guess O Meter accuracy of 2.7 to 18 miles while possibly degrading battery. I guess if the accuracy was that important it could be of value but as it is a Guess O Meter why do something that potentially degrades battery life? Essentially more accurate but reduced range.

If I have to wait for reliable 55° temps, I’ll bookmark this until June.

Mach-Lee said:

First, let me say this is somewhat controversial, as there is no official procedure from Ford for this.

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There is a procedure but I don't believe it is published or available to the dealer technicians. If they believe they have a qualifying case then a Ford engineer will usually perform the test remotely. From what I hear it takes a few days and sounds a lot like what you posted here.

This is why I question that State of Health figure that is provided by some of the 3rd party scanners. As far as I know, there isn't a state of health value in the BECM so I am not sure where that figure comes from. Probably just some arbitrary calculation that is based on some basic values.

Mach-Lee said:

Procedure:

1. Charge the vehicle to your normal level (e.g. 90%).
2. Drive the vehicle until the battery is down to 10% or less.
3. Park the vehicle and let the battery rest for at least 5 hours (preferably overnight)
4. Level 2 charge all the way to 100% in one session without interruption.
5. Leave the vehicle plugged in and let the battery rest for 2 hours after 100% is reached.
6. (Optional) With a scan tool, read the kWh to empty and state of health parameters.
7. Drive without charging until battery is below 50% (10-20% recommended)
8. Charge the vehicle back up to your normal level.

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Items 4 through 8 sounds like my daily routine. Well, pretty close anyway. Most days I get back home with around 60% remaining but some days it is 30-40% but that only happens 2-3 times per month.

For what it is worth......my GOM is very accurate. 2-3% optimistic but I consider that to be close enough for my needs.

SnBGC said:

This is why I question that State of Health figure that is provided by some of the 3rd party scanners. As far as I know, there isn't a state of health value in the BECM so I am not sure where that figure comes from. Probably just some arbitrary calculation that is based on some basic values.

For what it is worth......my GOM is very accurate. 2-3% optimistic but I consider that to be close enough for my needs.

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I'm not sure where the SOH in Car Scanner comes from either (perhaps other Ford EVs), but it seems real and aligns with what I expect. Maybe it's just not enabled in FDRS since there is a separate tool for reading the individual cell capacities.

2-3% GOM error is pretty good actually. Mine seems to always be off by 10%, sometimes more.

Mach-Lee said:

I'm not sure where the SOH in Car Scanner comes from either (perhaps other Ford EVs), but it seems real and aligns with what I expect. Maybe it's just not enabled in FDRS since there is a separate tool for reading the individual cell capacities.

2-3% GOM error is pretty good actually. Mine seems to always be off by 10%, sometimes more.

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After performing this calibration routine - did you see the SOH value reported by Car Scanner change? Mine is concerningly low (92.5%) but has never changed (At 18k miles now and started using car scanner at 6k).

I didn't really think anything of it until carscanner didn't give any signs of the 91kWh upgrade after I received the 91kWh upgrade. Like most things on this forum, it gave me something new to obsess over! If it's worth a weekend FDRS subscription I would run the supposed battery health routine but I don't know squat about it.

jbirdzee said:

After performing this calibration routine - did you see the SOH value reported by Car Scanner change? Mine is concerningly low (92.5%) but has never changed (At 18k miles now and started using car scanner at 6k).

I didn't really think anything of it until carscanner didn't give any signs of the 91kWh upgrade after I received the 91kWh upgrade. Like most things on this forum, it gave me something new to obsess over! If it's worth a weekend FDRS subscription I would run the supposed battery health routine but I don't know squat about it.

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I didn't take a before and after, but I will next time it's due. Mine reports 98.5% SOH with about 5k. It's probably worthwhile to try the calibration, but not really worth the FDRS subscription unless you notice it's still low after calibration.
Here's what you can see, 288 Ah is pretty much 100% health on the extended pack: https://www.macheforum.com/site/threads/battery-cell-voltages-on-fdrs.10475/

@Mach-Lee: My daily routine (Sunday night thru Friday afternoon) is really close to procedure. I charge to 100% Sunday night; charge ends around 3am. Car rests for 3 hours and I leave for my trip to work. I travel 79.3 miles each way to work plus 10-20 miles in local trips around where I work. I have a 22 Select SR AWD model. Lowest GOM at 100% has been 209 miles (overnight temperatures were in high teens (F)). With overnight temperatures normally in high 30s to mid 40s this time of year, my GOM has been averaging 221 miles. My routine is charge to 100% Sunday, Monday, Tuesday, Wednesday, and Thursday nights; drive my 158.6 mile minimum round trip to work and back home Monday thru Friday. On Friday night I charge to 80% for running around town over the weekend. My GOM has been pretty accurate as well. Most days, even coldest ones so far, my actual miles travelled and GOM drop have been within 4-6 miles of each other when I get home. For the last four weeks I have had Carscanner Pro app linked to my OBD MX+ and have monitored several parameters while driving to and from work. I have put 14,400 miles on MME since July 1st of this year. During the summer, my GOM at 100% charge averaged 245 miles (3.9 to 4.3 mi/kwh). With cooler weather here at the house, I have been averaging 3.3 to 3.5 mi/kwh with lowest trip value at 3.1 mi/kwh. My SoH per Carscanner is 95.5% but I have not noticed any appreciable loss of range or capacity. Energy to Empty parameter in app at 100% has been between 66.8 and 67.9 kwh. Unfortunately I wasn't doing any monitoring during the summer or fall so no info prior to it getting cooler here. Just some data from West TN with our relatively mild winter so far.

Subscribing. I need to do this...I'm pretty much driving my GT between 60-90% all the time.

Scooby24 said:

Subscribing. I need to do this...I'm pretty much driving my GT between 60-90% all the time.

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I am planning to do it on Friday when I come home from my commute to DC. I think I can plan an arrival at 10-20%, and do some local driving to bleed off the difference. I definitely will report back what happens with my SoH, as I have been tracking it.

I'm hoping mine is accurate as it's still showing 100%. Not that it really matters lol I'll probably only have it another year as I have two more EVs on order.

Scooby24 said:

I'm hoping mine is accurate as it's still showing 100%. Not that it really matters lol I'll probably only have it another year as I have two more EVs on order.

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Wow. Mine is around 95%, and it really annoys me. It shouldn't, but it does.

The first time I looked at the HVB state-of-health value, with only 2,000 miles on the odometer, it seemed low at 96.5%. Within the next 2,000 miles, it dropped to 94%. It then went back up to 95.5% and stayed there past 20,000 miles. At 26,000 miles, it is showing 93.5%. I have no idea what it is actually measuring, and I am not going to be obsessed with it.

@Mach-Lee - I am starting the procedure, and I am at 10% SoCD. Should I run it down to 10% SoC, or is 10% SoCD good? My SoC is just over 14%.

mkhuffman said:

@Mach-Lee - I am starting the procedure, and I am at 10% SoCD. Should I run it down to 10% SoC, or is 10% SoCD good? My SoC is just over 14%.

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To keep things simple for non-techies, let's just say below 10% indicated. If you want to run it down to below 10% real SoC that would be slightly better.