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Old 06-16-2016, 10:33 AM   #1
Join Date: Sep 2015
Posts: 94
TV battery replacement

Hello All,

I didn't quite see my question in a search, so sorry if it has been discussed a lot in the past.

I was wondering when you all change your TV battery?
We tow with our Sienna minivan. It is a 2011 with original battery. When car is on, the battery measures 13.8 volts. After you shut it off, it starts to drop. I let it sit for an hour or so, and when I recheck, it drops to 12.47-12.49 range. I have been checking this everyday for the past 5 days. The water level is perfect.

I see from the helpful chart someone posted on this site, it is between 80-90%.
Is it time to start thinking about replacing it? Should I just do it? Not sure how must faster it will continue to drop. Or will that take a lot longer.

Thanks for all your thoughts.


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Old 06-16-2016, 10:50 AM   #2
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Join Date: Oct 2014
Posts: 3,187
5 years is a while, but what you are seeing is normal for lead acid batteries. The 13.8 is the charging voltage and will always be around there if the charging system is working properly. The mid 12V reading is the charged or close to it voltage. You should always let a LA battery rest for a few hours before checking the voltage if you want anything close to an accurate reading. See the chart below for details.

Approximate state-of-charge

100% 12.65
75% 12.45
50% 12.24
25% 12.06
0% 11.89


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Old 06-16-2016, 11:09 AM   #3
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Most auto batteries die slowly, and give you enough warning that they need replacement. Slow cranking speeds are the usual symptom.

In maybe 15% of the cases they just die suddenly, and leave you stranded.

My replacement rule of thumb is 5 to 6 years.

My logic is this:

By putting off replacement, I am not saving $150 for a new battery, since I will have to spend that money at some time anyway. I am just trying to stretch out the last few dollars of battery life and taking a chance of getting stuck.
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Old 06-16-2016, 11:12 AM   #4
Join Date: Jun 2016
Posts: 46
where are you located?

Most likely the battery will be just fine over the summer. If a battery is nearing the end of its life you will find out when it starts to get cold and you lose your CCA.
(but if you live in the S then maybe you don't notice this)

If it is still firing up right away when you turn the key then you are fine.
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Old 06-16-2016, 11:34 AM   #5
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Location: N. Illinois
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Clean the terminals good with a wire brush, clean off the top of the battery and terminals with baking soda and water, check the water levels. Check voltage at the terminals with engine running @ approx 14.7 VDC run it and see what you've got. Any evaluation beyond that is done by putting the system under a load test and measuring individual cells with a hydrometer for uniformity. That's what will tell you if your battery is toast. Hint.. if when you looked at the cells for water level, if you saw the plates not covered by electrolyte in 1 or more, that isn't a good sign. Buy a new one!
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Old 06-16-2016, 11:18 PM   #6
Join Date: Sep 2015
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Thanks everyone for the replies.

We live 10 miles due north of the White House, in MD. So we won't have any cold weather anytime soon, bummer.

Luckily, none of the plates were even close to being exposed. It starts right up every time. I'm just used to changing them out after 4-5 years. But this one has been a good one so far.

I will give it a good cleaning and keep an eye out. Our oldest finally gets out of school this week, so off to Elk Neck state park for a few days.

Safe travels to you all. Thx again, mark

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battery, replacement

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