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Scheduled vehicle maintenance is one of those damned if you do, damned if you don't car owner responsibilities, as recently reported by one 2023 Rav4 owner who, while in for a regularly scheduled maintenance service, was told his auxiliary battery was low and that it needed a charging service for only $107.
Wait…WHAT?!
"Hi, I took my 2023 prime for 30k factory service and the dealership is telling me that the auxillary battery is at 69 percent of full capacity and recommend a recharge service priced at $107. Is this necessary? If so is there a good DIY option?" —OP
Yes, that is what the service department wanted for just hooking up their battery charger to the OP's Rav4 auxiliary battery.
What's Going On?
First, as a reminder, the auxiliary battery in a Hybrid vehicle is designed to power accessories, the computer(s), locks, lights, and other components.
The 12-volt battery wakes up the computer when you turn the key, signaling it to draw power from the hybrid battery to the electric motors responsible for propelling your car, as well as starting the gasoline engine half of the hybrid system.
If your 12-volt battery is dead, you won't be going anywhere until you can get a jump start on the battery to initiate everything for the startup.
According to the OP, during his scheduled maintenance, the service techs told him that they checked his 12-volt battery, and it read at only 69%.
That "69%" typically refers to the State of Charge (SoC), not the health or capacity of the battery. So, it just means the battery is partially discharged—not necessarily failing or in need of replacement…or an over-priced charging session to raise the battery's SoC.
In fact, this is a normal reading for practically any hybrid car's 12-volt battery if it has not been driven much in the non-EV mode, such as with multiple short trips in town or has sat parked for too long in cold weather and/or has a parasitic draw slowly sucking charge out of the 12-volt battery.
Was the OP Being Scammed?
This is one of those grey areas that I believe falls under "sin of omission" when it comes to what the service department says and does.
A $107 service charge will help but is likely not necessary:
- The 12-V battery recharges automatically when you drive the vehicle. If they had told him to take the car for a longer drive than usual and stop for a retest, the battery SoC would have improved.
- Using a basic 12-V battery charger at home is much cheaper AND some chargers offer a health analysis of the battery. If the service techs said the auxiliary battery is at 69% and did not explain what this means, it could be easily misconstrued as a battery going bad problem that they are willing to "fix" for $107.
- $107 is steep for something that takes only minutes and doesn't require any parts. The garage should have done it anyway if they believed it was a true maintenance concern and then guided him appropriately if the battery or the car's charging system was suspected. Since the car was relatively new, the warranty should cover the charges.
What Options Does the OP Have to Prevent This from Happening Again?
While the majority of the thread posts point out that this is a scam to add a charge to an otherwise "free" regularly scheduled maintenance check, only a couple of posts commented on what the OP should do to ensure this does not happen again.
One option, as I mentioned earlier, is to understand and test the health of your 12-volt battery to avoid unnecessary services from a garage.
That, and investing a small amount of money in a 12-volt battery charger/health checker, such as the type I depend on, recommended by some Toyota mechanics.
A second option is to prevent 12-volt battery drain by using a trickle charger. The Rav4 models are notorious for having subpar batteries. They would benefit from either a better battery for hybrids or investing in a solar trickle charger—especially for Rav4 owners concerned about their battery, which was discovered dead in an airport parking lot while they were away on vacation.
Related article: Is It Safe to Keep A Portable Jump Starter in Your Car? "I Keep Mine in My Wife's Toyota RAV4 All the Time.
Yeah, the 12v battery is definitely underpowered and is drained relatively quickly. Even 20 minutes of the radio going in accessory mode is enough to drain it. It's actually quite common for this to happen when the car is being serviced, it happened to me as well. And yes, the airport dilemma is a common concern and I've quite a few people post that their battery was dead after a long trip away. The solar trickle charger seems like the best solution in that situation —sherv19
The Trickle Charger Solution(s)
While the trickle charger does sound like the best solution, it is not always an easy one.
Weeding through multiple forum topics about solar-powered trickle chargers for the Rav4 model raises more questions than answers.
Some discuss using the OBD2 port or tapping into the 12-volt line and wiring it directly to the solar panel. Others recommend simply using one of several trickle charger plug-and-play systems, where a single cord connects from the solar panel to a charge monitor, and the other cord plugs into an accessory (e.g., cigarette lighter) port.
Difficulties arise when it is unclear whether plugging into or tapping the OBD2 port will initiate the "waking up" of specific systems, potentially leading to a parasitic drain. Or whether or not the accessory plug ports are directly tied to the 12-volt battery and are accessible when the ignition is turned off.
K.I.S.S. (Keep It Simple Stupid) Advice
There is a lot to be said for the K.I.S.S. acronym, which, unfortunately is not part of the automotive industry.
However, this does not mean that car owners have to follow suit when it comes to adding a feature or accessory to their car.
A good example can be found in the Toyota Owners Club forum in which the thread titled "Powering from Cigarette Lighter When Parked" where post commenter dervdave applied the principle of KISS:
It was simplicity at its best. Two wires: a red one (for positive with a fuse) and a black one (for negative) to connect to their respective 12-V battery posts at each end, with the other ends terminating into a port that matches the appropriate plug coming from the "plug and play" solar panel/voltage monitor system (trickle charger) used.
Suction cups would attach the solar panel inside the cabin to a suitable spot on the windows to catch sunlight. When not in use, the entire setup could be fitted into the cubby space just above the 12-volt battery.
Do You Have a Solar Panel Trickle Charge Solution That Works for You and Your Rav4 or Other Model of Car? Tell us about it in the comments section below, and be sure to mention the year and model of your car.
For more about potential scams the dealership service department might try on you, here are three useful articles to learn a few of their "tricks of the trade" tactics:
- Top Car Mechanic Scams to Avoid in 2024
- Our Daughter's First Car Scam Experience
- I am a retired GM Master tech of 50 years doing alignments. After doing alignments in a dealership, I will tell you that most (90%) did not need an alignment, they needed the tires aired up.
COMING UP NEXT: “Two Used Luxury SUVs to Avoid and What to Buy Instead,” Advises Consumer Reports
Timothy Boyer is an automotive reporter based in Cincinnati who currently researches and restores older vehicles with engine modifications for improved performance. He also reports on modern cars (including EVs) with a focus on DIY mechanics, buying and using tools, and other related topical automotive repair news. Follow Tim on Twitter at @TimBoyerWrites as well as on Facebook and his automotive blog "Zen and the Art of DIY Car Repair" for useful daily news and topics related to new and used cars and trucks.
Image Source: Deposit Photos
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