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Old 09-04-2013, 04:10 PM   #1
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FYI - Temperature Effects on Batteries

Has anyone checked the temperature of their battery boxes in the sun?
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In the morning sun, the temp of my battery box was 168 degrees F., probably higher in the afternoon sun.
I wonder if I should paint the tops a ligther color? I will check with Trojan and see what they say...
Yes, that is a manual crank.. my Atwood died on the trip out west :-(

Temperature Effects on BatteriesBattery capacity (how many amp-hours it can hold) is reduced as temperature goes down, and increased as temperature goes up. This is why your car battery dies on a cold winter morning, even though it worked fine the previous afternoon. If your batteries spend part of the year shivering in the cold, the reduced capacity has to be taken into account when sizing the system batteries. The standard rating for batteries is at room temperature - 25 degrees C (about 77 F). At approximately -22 degrees F (-27 C), battery AH capacity drops to 50%. At freezing, capacity is reduced by 20%. Capacity is increased at higher temperatures - at 122 degrees F, battery capacity would be about 12% higher.
Battery charging voltage also changes with temperature. It will vary from about 2.74 volts per cell (16.4 volts) at -40 C to 2.3 volts per cell (13.8 volts) at 50 C. This is why you should have temperature compensation on your charger or charge control if your batteries are outside and/or subject to wide temperature variations. Some charge controls have temperature compensation built in (such as Morningstar) - this works fine if the controller is subject to the same temperatures as the batteries. However, if your batteries are outside, and the controller is inside, it does not work that well. Adding another complication is that large battery banks make up a large thermal mass.
Thermal mass means that because they have so much mass, they will change internal temperature much slower than the surrounding air temperature. A large insulated battery bank may vary as little as 10 degrees over 24 hours internally, even though the air temperature varies from 20 to 70 degrees. For this reason, external (add-on) temperature sensors should be attached to one of the POSITIVE plate terminals, and bundled up a little with some type of insulation on the terminal. The sensor will then read very close to the actual internal battery temperature.
Even though battery capacity at high temperatures is higher, battery life is shortened. Battery capacity is reduced by 50% at -22 degrees F - but battery LIFE increases by about 60%. Battery life is reduced at higher temperatures - for every 15 degrees F over 77, battery life is cut in half. This holds true for ANY type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever. This is actually not as bad as it seems, as the battery will tend to average out the good and bad times. Click on the small graph to see a full size chart of temperature vs capacity.
One last note on temperatures - in some places that have extremely cold or hot conditions, batteries may be sold locally that are NOT standard electrolyte (acid) strengths. The electrolyte may be stronger (for cold) or weaker (for very hot) climates. In such cases, the specific gravity and the voltages may vary from what we show.

For additional Battery information:
http://www.solar-electric.com/deep-c...ttery-faq.html
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2013 Jayco Eagle 284BHS
250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller
1500 Watt Ramsond PSI, 2 Trojan T145 Batteries (260Ah)
2 - AirSight Wireless IP Cameras (used as rear view cameras)
EnGenius WI-FI extender, D-Link wireless (n) modem
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2012 Ford F150XLT, EcoBoost w/3.73
157" Wheel base, HD Towing Package

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Old 09-04-2013, 06:06 PM   #2
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It's 4 PM in west Phoenix.... It is 108 deg F ambient. My 27 series deep cycle twin 12VDC batteries (same type cases that you have) are running 126 deg F (as measured on the top of the black plastic cases). I keep them covered with a burlap moving blanket as "insulation" This has proved to be very good for longevity and capacity (for the given conditions).
BTW...The wall of my house that is in direct sunlight at present is running 172 deg F. Inside of that wall in garage is 113 deg F. Inside of that wall in house is 84 deg F. (I am researching cool-wall Tex cote). (OK...doesn't have anything to do with battery temps, but since I had my ray gun out, I got curious!)
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Old 09-04-2013, 07:20 PM   #3
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It was interesting, I just happened to touch the battery box an thought that it was pretty hot. Hence the 168 degrees. I will be covering the battery boxes. Thanks.. So I then pulled the ladder out and took a few more temps that day. The first picture is the roof 116 degrees (not bad), 2nd is the front cap (should be dark brown, but has taken on a white bleached look after 1 year and 2 weeks), yes that is 199 Degrees.. it has been over 200 earlier this month, and unfortunately that radiates heat into the trailer for the 3rd picture, the closet behind the front cap is 141 degrees. If you close the sliding doors, the bedroom heats up to over 115 degrees. Is there a wonder as to why the AC units in these trailers can not properly cool the camper. I have contacted Jayco to see what can be done to clear up the bleached look on the top portion of the cap.
Here they are with pictures:
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__________________
2013 Jayco Eagle 284BHS
250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller
1500 Watt Ramsond PSI, 2 Trojan T145 Batteries (260Ah)
2 - AirSight Wireless IP Cameras (used as rear view cameras)
EnGenius WI-FI extender, D-Link wireless (n) modem
MagicJack Internet Phone
2012 Ford F150XLT, EcoBoost w/3.73
157" Wheel base, HD Towing Package

Our Solar Album https://www.jaycoowners.com/album.php?albumid=329
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