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I just bought a brand new car (Honda Accord Touring 2017). Its battery recharge characteristics are:

- loses 1/3 of its charge in 4 days (if the car is resting. See test attached)
- loses 1/3 or its charge even after medium trips (photos in test attached)
  (For example: after 28 miles, battery goes from  12.61 V to 12.31 V).
- thus, would require manually-charging nearly every day 
 (because my daily trips are typically less than 28 miles.
 by not charging in one week, I had a flat battery after 1 week of normal driving). 

In contrast, I believe (let me know if you disagree) "maximum" recharge characteristics should be to:

- lose 1/3  of its charge in ~12 days (if the car is resting)
- lose 100% of its charge in 1 month (T = C/i = 45/0.05 = 900 hours)
- alternator-charging by driving 6 miles every ~4 days, or
- manually-charging once a week or once a month.

My Honda Dealer looked at the car and dismissed the problem by saying:

- There is nothing wrong with the car
- This battery discharge amount is normal because the car has many computers  
- We would only replace the battery if it was not charging 
- We only follow Honda tests which do not show any issues.

MY QUESTIONS IS: In your experience, what are "normal" recharge characteristics of modern cars (are they different or about the same as my belief above)? The answer would indicate if I am stuck with a problem car. In that case, suggestions on the next course of action are appreciated.

My full test steps, methods, and photos are at http://bit.do/BatteryTestAccord2017 . enter image description here

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    You're really over exaggerating the computers in your car. They're, at best, simple microcontrollers that draw a few mA. Nothing even close to rolling a window up and down. I don't see what problem you're trying to solve since voltage isn't linearly proportional to remaining capacity. – justinm410 Mar 28 '17 at 5:18
  • if you are leaving the car sit for long periods and itching to replace the battery look for one that is tolerant of deep discharge. – agentp Mar 28 '17 at 11:10
  • Thanks for the help @justinm410 I have added "Clarification" to the post. The dealer (not me) blamed on computers. Thanks for confirming computers are not the likely culprit. In your experience, do you believe the recharge characteristics I listed for the new car are normal? – sambaMan Mar 28 '17 at 14:47
  • Thanks for the help @agentp I have added "Clarification" to the post. I found one that fits and is Dual Purpose: Starting/Deep Cycling. But it does not list its Recharge Capacity (important in this case). That seemed a bit fishy to me. Is it normal for Deep Cycling not to list RC? – sambaMan Mar 28 '17 at 14:48
  • Thanks @Chenmunka. I have added "Clarification" and edited the post. – sambaMan Mar 28 '17 at 14:49
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PROBLEM SOLVED. Many thanks to all who helped! DETAILS: 1) Comparison with new better multimeter showed old one was underestimating readings (by 0.22 V); 2) A 7-day car rest showed normal discharge (from 12.6 V to 12.44 V); 3) Measurements taken with car completely "sleeping" (30 minutes after engine was OFF), showed battery charge increased as expected. So, I am now comfortable enough with the car. Albeit I'm still not sure why battery died. Perhaps it was a fluke, as I was trying all features. Just in case, I bought a "battery monitoring gage" (to know when to manually charge, if needed) & a portable lithium battery (to jump start, if needed).

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@sambaMan; So, I had a similar issue with my '17 Accord Touring. The car acted as if the battery was dead; lights on and off on the dash, clicking at the starter. My OBDE reader said it was at 9.6 volts. Hooked up my Noco lithium jump starter. It displayed 10.1 volts. I turned the Noco on and it read 11.1 volts. Then I noticed one of the battery fill lids was half cocked and only covering one of the three fill ports. There is also evidence of spillage/leakage on top. The last time it was at the dealership was April. I will be calling them today to find out what inspections were done and if the battery was one of them. TBH, I never really look under the hood. I learned how to work on cars a long time ago. But I hate it...so back to the dealership.

I digress...As soon as I got it started, the Noco said 14.6 volts. The battery is an OEM 550CCA. I was told by a coworker to just refill it. I'm just going to break down and get new one however (if the dealership isn't found to be responsible.) The battery did open up, so I don't know what contaminants worked its way inside and I need to get it out of the battery housing to see if any other damage has been done. Hopefully, the fluids simply evaporated/off-gassed.

  • Hopefully the dealer will be responsive. My battery has been good so far. But, just in case (to jump start car or to charge your phone/laptop), even with a new battery, I like the peace of mind of having a portable lithium battery – sambaMan Aug 20 '18 at 17:54

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