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Piston Slap: Deep Cycles, Battery Charging, and Leafy Bolts
Scott writes:
My mother is 79 years old, so she (wisely) doesn’t drive further than three miles on any trip. It is usually more like one mile. As expected, this means the battery on her 2018 Honda CR-V (1.5T 2WD EX) dies every three to four months.
I got her a battery meter that plugs into the cigarette lighter and told her to rev the engine while parked for 20-30 minutes every few weeks or when the numbers are low. She does that and it’s worked so far but it’s a hassle. Her apartment complex doesn’t have power outlets so no trickle charger is possible, and she wouldn’t want to fiddle around under the hood anyway.
Any other thoughts on what can be done here to make life easier for my mother?
Sajeev answers:
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Hi Scott, this is a great question! I have a quick answer that I would like to throw out: How about installing a battery cutoff switch?
Is this something your mother would use if installed? They are straightforward and come in several different designs. Tell me what you think.
Scott replies:
Interesting. That would stop the parasitic drain but my assumption has been that the main problem is that driving one mile doesn’t recharge the battery enough from starting the engine—is that not right?
Sajeev answers:
(EDIT: I forgot to mention the possibility of using in-car solar chargers, which have merit, and would work if Scott’s mom parks her car outside.)
I am confident that the reserve capacity of a healthy battery means it will have no problem with only one mile of driving, once the drain is addressed. My confidence stems from the fact I’ve stalled a manual transmission vehicle less than a mile after having jumpstarted it a few minutes before, and the vehicle still fired back up.
It’s possible (probable?) that I am wrong, as one data point does not make an irrefutable law, and my car’s battery is much bigger than the one in the CR-V. Peukert’s Law says that a lead-acid battery loses reserve capacity as the rate of discharge increases. Logical enough, and it suggests two things:
- Have a local mechanic ensure there’s an acceptable amount of parasitic drain (i.e. no more than what is needed to keep the engine computer and stereo memory alive) and fix any deviations from acceptable.
- Consider getting a deep cycle or dual-purpose battery: the CR-V has a pretty small battery and (checks Google) often has a reserve capacity of 45 minutes. I found one with a more impressive 105 minutes.
If you can get a battery with a huge reserve (deep cycle, or dual-purpose) and teach Mom to use a cut off switch, I am very confident the problem will be solved. It will likely be solved with just the battery upgrade. If all else fails…
While I generally dislike telling people to punt their current car and pick another one, your mother sounds like the perfect use case for small, nicely depreciated EV. The best part is that a cursory glance at Bolt EV vs. CR-V values suggest you would make money trading the Honda in for a Chevy that’s newer with low mileage.
And I don’t mean a few bucks in profit, but like, thousands of dollars. EVs generally crater in value when used, and folks who do short commutes would be wise to consider one.
Of course that requires you convincing your mom this is a good idea, then spending time horse trading with local dealerships (but they will be keen to get a hot Honda for a cold Bolt). If that happens, you will need to ensure that someone tops off the Bolt every few months at an off-site charging station.
I recently had the pleasure of meeting an older woman with a (heavily depreciated) Nissan Leaf at an EVgo charging station that was a quarter mile from a series of apartment complexes: she had no regrets in her vehicle purchase and politely declined my offer to help her with the charging interface. (That particular station had an odd layout that made parking your charging port to the correct machine a little confusing for first-timers like me, hence my offer.)
So to wrap it up, consider these three things:
- Fix a potential drain
- Get a battery with a deeper reserve
- Try in car solar charging
- Give up and get a used EV from depreciation darlings at Chevrolet or Nissan, and use the extra cash for something else in Mom’s life.
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Just a quick thought. How about using one of the solar battery charger/tenders? I can’t say I know much about them. However a guy I knew had a Chevy pickup that was discharging and the dealer could not find the problem. That was his stopgap solution and from what I recall it worked well enough.
Seems a reasonable option!
That is such a good idea I can’t believe I didn’t remember it from the last time we covered it:
https://www.hagerty.com/media/advice/piston-slap/piston-slap-in-car-solar-charging/
I would say that it does not matter how big the tank is if you take more out during a start than you put back during the run. My mother had the same issue. For paul s murray’s comment, I tried the solar charger trick and it really didn’t help. Not sure if it was the product or her not using it correctly. She eventually stopped driving and it became a non-issue. One thing I would do from time to time is stop out and take mom’s vehicle out for a good run but even this didn’t really solve the problem.
The parasitic drain is a high probability but also if it is the original battery it could be failing to. Just a battery change could fix this.
Check for a drain if none change the battery. My 2017 truck sits over winter and did fine till this year. It would drain sitting a short while. A new battery fixed it.
As for a drain it could be a simple accessory or wire issue.
I have read technical service bulletins from several manufactures that state if a vehicle sits for longer than approximately two weeks or so the battery will lose charge.
A battery pack jump starter is very safe, easy to use and use friendly. Given all the pros and cons of this situation, its the most cost effective solution.
I understand the reluctance of the writer’s mother to “dabble under the hood” but with a little guidance, patience and practice her fears and confidence in performing a jump start on her own could be easily accomplished.
These devices are excellent and you can’t mess up even if you incorrectly attach the clips to the wrong terminals. If he demonstrates and allows her to perform the task herself a few times under supervision, is a no-brainer. In light of the costs for the alternative solutions, this makes the most sense.
It’s too easy to assume someone or is incapable of learning new things. I’m sure she’s more capable of learning a new skill than her son assumes especially after it’s demonstrated and she’s allowed to try on her own…
If your mom’s apartment complex lacks outdoor outlets for a trickle charger, how would she charge an EV’s battery? Answer: move in with you.
Or just visit a third party charging station 1-2 times a year?
EV isn’t going to work. She can’t even plug in a trickle charger. Where is the EV going to charge?
Trickle chargers go under the hood, EVs are plugged in like filling up at the gas station. I wouldn’t be surprised if she can make the lateral move from a Texaco to an EVgo.
Well I figured if “Her apartment complex doesn’t have power outlets so no trickle charger is possible” that the wall plug for a really slow charge on an EV isn’t an option either since this is an apartment. Sure she could go to a charging station somewhere but would she want to is the question and how far away would that be. A few blocks, miles?
Sadly we do not know where she lives, but given how much she drives and how quickly gas goes bad, going to an EV charging station every year (or every two years, TBH) sounds like a pretty good idea.
Legit question: a fully charged EV can sit for a year or two with no bleed-down of charge?
From what I have read, it can go for months without needing to be charged. Given the duty cycles mentioned here, I bet it could break a year without causing significant stress to the battery pack.
But there are conditions, namely the external temperature and the state of charge (preferably around 80%, not 100%). The EV would need to be topped off (i.e. charged to 80%) more frequently in times of freezes or heatwaves. There is no perfect answer, but this one still makes a lot of sense.
Even if a bomb cyclone hit every month and an EVgo is 10 miles away, going EV sounds like a legit option for the OP. Not to mention the cash you generate by switching from ICE to an EV commuter car.
So, there’s no EV version of stale gas, eh?
Switching to an EV will not make 12v battery issues go away and in fact it is likely to make them worse. Since the battery only has to boot the computers and close the contactors many HEV, PHEV and EVs use a tiny 12v battery. Because many EVs have telematics of some kind their normal resting drain is higher than that of an ICE vehicle. The other problem is that since it isn’t crancknig an engine there can be no warning that the battery is dying, works fine one day and won’t boot the car the next.
The above is what happens to my Leaf.