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How long will battery last in the garage?

275 Views 7 Replies 6 Participants Last post by  williamsji
We have a 2019 CR-V 2WD Touring model that’s usually driven at least every few days. I’m in the habit of replacing batteries after three years so this car’s current battery is less than a year old. We have an occasional freezing spell here in East Central Florida but we’re not subject to the punishing cold seen in much of the rest of the country. I’ve noticed posts here about CR-V batteries draining while the car sits idle in the garage but I didn’t think that should be a concern for us since our car is driven often and gets a fresh battery regularly. Recently though the primary driver, my wife, took a serious hit from the seasonal flu (she’s recovering nicely, thanks) and has been staying home. Now that I see the car may well sit idle for a week or two I’ve begun to wonder: given our circumstances, how long should I reasonably expect the car to sit idle in the garage before we risk having battery issues?
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2020 Touring Hybrid
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2,087 Posts
We have a 2019 CR-V 2WD Touring model that’s usually driven at least every few days. I’m in the habit of replacing batteries after three years so this car’s current battery is less than a year old. We have an occasional freezing spell here in East Central Florida but we’re not subject to the punishing cold seen in much of the rest of the country. I’ve noticed posts here about CR-V batteries draining while the car sits idle in the garage but I didn’t think that should be a concern for us since our car is driven often and gets a fresh battery regularly. Recently though the primary driver, my wife, took a serious hit from the seasonal flu (she’s recovering nicely, thanks) and has been staying home. Now that I see the car may well sit idle for a week or two I’ve begun to wonder: given our circumstances, how long should I reasonably expect the car to sit idle in the garage before we risk having battery issues?
I think if you get the car out every week for a half hour drive you'll be fine. If you're really worried, buy a smart battery maintainer and hook it up overnight every week to keep the battery in top condition.
 

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2009 Honda Ridgeline, 2020 CRV EXL
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43 Posts
A good drive, 1/2 hour or so, once a week is fine in most situations. Any longer than that, a battery maintainer connected the entire time it sits would be a good idea. I recently installed one on a relatives rarely used vehicle - easy to hook up and in that situation the cable could be routed outside by the grille so they don't have to open the hood to connect/disconnect the charger.
 

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2017 CRV Touring - Pearl White w Black Interior
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9,577 Posts
Let's math this a bit to help with understanding of what is going on with the battery in a parked gen5 CRV, with a 51R battery in it, and what to do about it:

The normal parasitic drain on a gen5 CRV is ~50ma. That is normal, but it does take a toll on a vehicle that is only driven short distances and infrequently. Reason: 50 ma drain will draw down 1.2 amp hours of charge from your battery every 24 hours. An OEM 51R (40 CCA) battery will generally have a saturation charge capacity of 40 amp hours. A higher CCA version of a 51R (500CCA) will generally have a saturation charge capacity of 45 amp hours.

For someone who only drives a few times a week, and/or short trips.. the battery never gets fully topped up from driving, and so you suffer slow creeping discharge (meaning as each week goes by, the state of charge of the battery declines some percentage and the lost charge is never fully restored.

If you do the math, you will realize that your CRV parked will lose ~ 3-4% of it's charge capacity per day, assuming it is a fairly new battery with no real life degradation so far. As the battery ages, you will lose about 10 amp hours of saturation charge capacity per year... so an older battery will deplete much faster than an new battery.

Now for some troubling news ... persistent low charge on a battery (ie: 80% or less) will cause the battery to chemically degrade at an accelerated rate. To give a usable data point: a battery that is mostly sitting at around 50% of charge on average, will likely fail 50% sooner than one kept well topped up persistently.

More troubling news: Honda charging systems NEVER saturate the charge on the 12v battery. Frankly, no modern vehicle brand does, because they are stingy to eek out a bit more fuel economy in their EPA certifications. Best you can expect is 95% of saturation charge, but more often due to the cycling dual mode nature of the charging systems... it will be somewhere between 85-90% of saturation charge capacity after a drive of sufficient length to restore lost charge to the battery.

If you talk with dealerships or independent service providers, they will most often simply tell you to drive the vehicle more and more often, which is one solution, but a wasteful one. Some are more helpful and will suggest you use a smart charger periodically.

The best practice if you want to get the maximum useful life from the battery is to do exactly as EXcommunicated does (as I myself do) and put a smart charger on the battery once a week overnight to insure the battery gets a good full 100% saturation charge on the battery weekly. This not only keeps the battery in a geneally high charge state, it also maximizes life of the battery as the smart charge cycles also modestly recondition the plates (removing any sulfation that has accumulated, when done periodically).

Plate sulfation due to persistent low charge state on the battery is the number one killer of batteries. Smart charging weekly mitigates most of this.

The next most common killer is mechanical shock that damages the plates (most often hydraulic shock from wet electrolyte impacting the fragile plates, such as taking speed bumps too fast and aggressively). If you are a speed bump predator, or drive off-road or on unimproved bumpy roads... the best practice is to go with an AGM battery as that eliminates vulnerability to mechanical shocks.
 
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