State of health
A code reader
cannot see it
Generic OBD-II cannot read an electric car's battery health at all. It was written for emissions, and a battery car has none.
At a glance
- The standard was written for emissions, and an electric car has none of them
- State of health is an estimate the car makes, not a measurement it takes
- Two tools disagree on the same car for five specific reasons
- LeafSpy is the best consumer tool there is, and it only works on a Leaf
Why the number moves
State of health is capacity now divided by capacity when new. The number hides which quantity was measured. A pack can still hold nearly a full charge and have lost the ability to accept it quickly, and that shows up as a slow fast charge rather than as a lower kilowatt hour figure.
Five reasons two tools disagree
- The figure the car reports is a model based estimate, not a measurement, and it drifts.
- Buffer capacity is not exposed, so the gross and net numbers differ.
- The car relearns capacity after a full charge or a deep discharge, so a reading taken after a 100 percent charge differs from one taken after months of shallow cycling.
- Temperature at the moment of reading shifts the result.
- Different tools read different registers and apply their own corrections.
And one nobody mentions
Several manufacturers show 100 percent of original range after five years. Recurrent's own explanation is software updates that improve efficiency and release reserved capacity over time. That is a vendor admission that a displayed number can be an artifact rather than a measurement.
What a real test does differently
A physical discharge test is different in kind. It measures the energy actually delivered between a full charge and a low state of charge, rather than asking the car what it believes.
What you can buy
- LeafSpy Pro
- $19.99Nissan Leaf only. The best consumer battery tool there is, and it reads state of health, amp hours, cell voltages and the quick charge count.
- OBDLink CX
- $79.95Bluetooth adapter, iOS and Android.
- OBDLink MX+
- $139.95Bluetooth adapter, iOS, Android and Windows.
- Recurrent
- $60 a yearNot a physical test. It connects through telematics and compares your car's daily readings against a fleet of more than 50,000 vehicles. Their own words are that they cannot see into your battery.
A US buyer today can hire Recurrent, which is an estimate rather than a test. AVILOO's quick test is sold through dealers and fleets in the US rather than to the public, its full test is priced in euros for the European market, ClearWatt is UK only, and Altelium sells to insurers rather than to drivers. That gap is the reason this site exists.
Can you see the fast charge history
- Nissan Leaf
- YesLeafSpy reports the quick charge connection count.
- Hyundai and Kia
- ProbablyA well maintained community project documents the identifiers, and whether a cumulative fast charge count is among them was not confirmed.
- Tesla
- Not for a buyerSupercharging history lives in the previous owner's Tesla account, which a used buyer cannot see.
- BMW, Chevrolet, Volkswagen
- UnknownNo evidence either way was found, so this site does not claim one.
Questions people actually ask
Can my mechanic just plug in a scan tool and tell me the battery health
Why did two apps give me different state of health numbers
The Kind of Tech We Send
Meet Matthew Bolen of Wrench Services in Rio Rancho, New Mexico.
Matt has worked on engines since he was seven or eight. He learned from his dad, and from a brother who is a heavy diesel tech. He passed his Advanced Level Certification in Nevada in 2007 and became a G2 emission testing tech.
He carries scan tools, an oscilloscope, a hybrid battery tester and meters. He is also the first to say the tools are not the point. Reading the numbers right is.
Don't sell someone a $3,500 battery unless it needs it.
That is the rule a battery test is for. A pack with one weak module often needs that module, not a whole new pack. Matt will tell you which one you are looking at.
His Record
- EV and Hybrid credential on MechanicRank, scored 100 percent
- Advanced Level Certification, Nevada, 2007
- G2 emission testing tech
- Covers Rio Rancho and the surrounding area
And in Michigan, Ron at Manko
In Westland, the tech is Rani Taki, who goes by Ron. He owns Manko Mobile Automotive.
Ron has ten years in the trade. He spent two years at Ford as a diagnostic and drivability technician and a year on the road as a race mechanic. For the last six he has run his own mobile repair business across Wayne County.
Pre purchase inspections are one of his specialties. Electronic diagnostics are the other. A battery test needs both, a scan tool read the right way and a straight answer on what the car is worth.
His Record
- Ford diagnostic and drivability tech, two years
- Ten years in the trade, six of them mobile
- Pre purchase inspections and electronic diagnostics
- Covers Westland, Dearborn, Livonia, Canton and the rest of Wayne County
Who comes out depends on where the car is parked. Matt and Ron are the standard we hold every tech to.
Buying a Used EV or Hybrid?
Get the battery measured before you pay for it. A PPI Auto inspector tests the pack on the car you are looking at and sends you the numbers. Starting at $225.