Zorlac
Well-known member
"battery voltage down slightly from hot soak"
That actually acts to increase the battery's voltage.
That actually acts to increase the battery's voltage.
Failure to start when hot!? Battery or Starter?
- Thread starter slapnpop
- Start date
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radman
R.I.P. Our Motorcycling Friend
Battery University
Though a warm battery generally performs better than a cold one, extremes at either end are detrimental to both performance and life. The hot soak a FJR battery receives every time the bike is shut down does the battery no favors. It's location is bad for several reasons. Increased internal resistance due to heat does not increase voltage-in cars, the blanket and insulators one sees on batteries is for heat resistance, not cold.
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Zorlac
Well-known member
Agreed on the detriments of heat, but from a pure chemical reaction standpoint, the battery's terminal voltage increases with temperature.
That is why good battery chargers compensate the charging voltage based on ambient temperature.
"Increased internal resistance due to heat."
The internal resistance will decrease allowing for more cranking amps out of a hot battery, but it's lifespan is considerably reduced.
https://www.windsun.com/Batteries/Battery_FAQ.htm
Temperature Effects on Batteries
Battery 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.
Charge voltage vs Temperature for AGM and Flooded batteriesBattery 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.
Click to see larger graph of Battery Capacity vs 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.
That is why good battery chargers compensate the charging voltage based on ambient temperature.
"Increased internal resistance due to heat."
The internal resistance will decrease allowing for more cranking amps out of a hot battery, but it's lifespan is considerably reduced.
https://www.windsun.com/Batteries/Battery_FAQ.htm
Temperature Effects on Batteries
Battery 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.
Charge voltage vs Temperature for AGM and Flooded batteriesBattery 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.
Click to see larger graph of Battery Capacity vs 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.
radman
R.I.P. Our Motorcycling Friend
I stand corrected, and shall inform the batteries that come into the shop here to read the article, and behave accordingly.
Zorlac
Well-known member
It's not about ego, it's about accuracy.
In any event, all batteries have a finite lifespan that is shortened by elevated temps.
https://www.ibsa.com/www_2001/content/about...ap_zones_lg.jpg
In any event, all batteries have a finite lifespan that is shortened by elevated temps.
https://www.ibsa.com/www_2001/content/about...ap_zones_lg.jpg
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