Is there any difference in lifespan for a battery that's mounted in the trunk vs. in the engine bay where it'd be much hotter? My thought is that there should be noticeable difference, for the same reason that people in hot climates can only get 2-3 years from their battery but people in moderate climates get 5+ years. Has anyone noticed a difference in their own cars?
lifespan of trunk mounted car battery
- Thread starter xfactor9
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This has come up before and many members claim longer life for a remotely mounted battery.
I'm not sure that I agree based upon my personal experience.
It doesn't matter either way, though, since unless you want to ghetto engineer something, the battery lives where the car maker put it and it lives and dies based upon how hot it gets and how often it's left at less than full charge.
I'm not sure that I agree based upon my personal experience.
It doesn't matter either way, though, since unless you want to ghetto engineer something, the battery lives where the car maker put it and it lives and dies based upon how hot it gets and how often it's left at less than full charge.
I have 2 cars with trunk mounted battery MB E430 and Volvo V70 and 2 cars with battery under the hood. The batteries in the trunk are big size 49, the battery of LS400 is 27f and S2000 is 51
The E430 is 15 years old and it has third battery in it, the original lasted about 6-6.5 years, the second is MB battery lasted 4.5-5 years and the current battery is 3.5 years old.
The Volvo V70 bought used 2 years ago, I don't know how old is the battery.
The LS400's batteries lasted about 4-6 years and so is the small 51 in the S2000.
I can't say the batteries in the trunk will lasted longer than under the hood. It depends on the battery quality and size.
PS Lately I added insulation(reflective roll from Lowes) for under the hood battery, it seems to add few months to the life of under the hood battery.
The E430 is 15 years old and it has third battery in it, the original lasted about 6-6.5 years, the second is MB battery lasted 4.5-5 years and the current battery is 3.5 years old.
The Volvo V70 bought used 2 years ago, I don't know how old is the battery.
The LS400's batteries lasted about 4-6 years and so is the small 51 in the S2000.
I can't say the batteries in the trunk will lasted longer than under the hood. It depends on the battery quality and size.
PS Lately I added insulation(reflective roll from Lowes) for under the hood battery, it seems to add few months to the life of under the hood battery.
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Heat is unkind to batteries, to the trunk seems like a more hospitable environment.
My Volvo has an 8-year old battery in the trunk that is original to the car - still working perfectly. Wife's Lexus goes thru batteries (in the engine compartment) every 3 years.
I recently learned that it's a good idea to top off a battery with a good quality charger a few times a year, especially if the battery is tired or gets short-tripped. Sometimes an overnight trickle charge will breathe new life into a weak battery. The alternator does a good job of keeping a battery charged but not necessarily topped off.
I like the insulation idea that HTSS_TR posted. I might do that in my Durango. Next batt in the 'rango will be an AGM.
My Volvo has an 8-year old battery in the trunk that is original to the car - still working perfectly. Wife's Lexus goes thru batteries (in the engine compartment) every 3 years.
I recently learned that it's a good idea to top off a battery with a good quality charger a few times a year, especially if the battery is tired or gets short-tripped. Sometimes an overnight trickle charge will breathe new life into a weak battery. The alternator does a good job of keeping a battery charged but not necessarily topped off.
I like the insulation idea that HTSS_TR posted. I might do that in my Durango. Next batt in the 'rango will be an AGM.
The heat does affect them so the trunk should be a lot better. But if the car never came with a truck Mount battery then I'm sure not only one time but more frequent costs.
Watched an episode of Wheeler Dealers where Ed China repaired the battery cooler fan on an old XJ6 with an underhood battery. It pulled air in from the cowl into the battery box. Tells us something I suppose.
I'm still on the original battery for our Miata, which rolled off the factory floor in Hiroshima in December 1999 and some 85K miles ago. The battery is trunk-mounted. I don't know if there's any correlation, but it is something to think about.
Gary
Gary
I think it is just the Japanese batteries. The original Panasonic battery (underhood) lasted 12 years in my ECHO, it was still starting the car but was cranking slower so I replaced it. No battery ever lasted that long in my BMW which has it under the rear seat.
Originally Posted By: mxhdroom
I'm still on the original battery for our Miata, which rolled off the factory floor in Hiroshima in December 1999 and some 85K miles ago. The battery is trunk-mounted. I don't know if there's any correlation, but it is something to think about.
Gary
Originally Posted By: mxhdroom
I'm still on the original battery for our Miata, which rolled off the factory floor in Hiroshima in December 1999 and some 85K miles ago. The battery is trunk-mounted. I don't know if there's any correlation, but it is something to think about.
Gary
Hello, I say this from HUMOR and my "mild techie persona".
This thread EPITOMIZES a batch of completely unrelatable data points except MAYBE for a "HOT vs. COLD" argument.
I love it.
My V70's (rear mount) battery just turned 7.
By the way, are Excide batteries OK? Kira
This thread EPITOMIZES a batch of completely unrelatable data points except MAYBE for a "HOT vs. COLD" argument.
I love it.
My V70's (rear mount) battery just turned 7.
By the way, are Excide batteries OK? Kira
Stay away from Excide, my brother,put 3 of them in his car and all were DOA. three of their executives went to prison for selling defective product to Sears.Their biggest retailer now is Home Depot. Go figure?
Exide works for me. I actually worked one shift at the plant nearby. The have a warehouse nearby that sells them at good prices. I bought one that had a maintenance free sticker on it, but had water caps on it. I was driving 60-75k miles a year and in the spring I added water, but forgot to in the summer and ended up cooking it.
My Buick LeSabre has its battery mounted under the back seat. It stays cool back there and super clean. If I ever get a different kind of car someday, I'm gonna mount the battery in the trunk.
Originally Posted By: Wolf359
If you're using the 49 battery, try getting an AGM battery. At this point it might be too late, but over on the Mercedes forums some people report getting 8-12 years out of them. Mine is a little over 7 years and it's still going.
I got AC-Delco AGM 49 for E430, the 3 years old Motorcraft battery from E430 is in Volvo to replace the unknown age group 65. Keep the old 65 in garage, charge it once a month and keep it as a spare for either E430 or V70.
If you're using the 49 battery, try getting an AGM battery. At this point it might be too late, but over on the Mercedes forums some people report getting 8-12 years out of them. Mine is a little over 7 years and it's still going.
I got AC-Delco AGM 49 for E430, the 3 years old Motorcraft battery from E430 is in Volvo to replace the unknown age group 65. Keep the old 65 in garage, charge it once a month and keep it as a spare for either E430 or V70.
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JHZR2
Staff member
Heat kills batteries. So does undercharging them, so hard sulfate forms. Trunks are obviously cooler, but might the battery have a charge issue if the longer cabling run creates greater losses and higher voltage drop. It is harder to charge into a higher impedance battery, especially if current controlled.
I want to say that the trunk mounted battery in my bmw is from 2008, but the underhood battery in my saab was from the same time,.. Both seem fine,
I want to say that the trunk mounted battery in my bmw is from 2008, but the underhood battery in my saab was from the same time,.. Both seem fine,
What I have noticed on my 10 year old Japanese cars, is that the battery is insulated from the rest of the engine compartment, and air is drawn around them through the cowl vents. One has an AGM battery and one a regular battery. In our BMW, the AGM battery is in the trunk. All of our car batteries last between 3 and 4 years. The longest I have ever had a battery live was 6 years, that was in a garage, with an AGM battery on a Deltran battery tender almost full time.
Here in Florida, the ambient air temperature is higher than a lot of other places, and even the trunk mounted battery sees ambient temperatures in the trunk of well over 100 degrees F. The one time I measured it was after the car had been sitting in the driveway for a number of hours, the trunk interior measured 140F, which was probably lower than what it was before I opened it.
Here in Florida, the ambient air temperature is higher than a lot of other places, and even the trunk mounted battery sees ambient temperatures in the trunk of well over 100 degrees F. The one time I measured it was after the car had been sitting in the driveway for a number of hours, the trunk interior measured 140F, which was probably lower than what it was before I opened it.
This brings back memories
One of my first professional gigs was with Johnson Controls for their Interstate and Sears’s brands doing controlled testing.
Regardless where a wet celled battery resides (and external influences such as impact or overcharging) there are 4 things fatal to any battery.
Heat- The individual battery’s tolerance varies based on design parameters but a good rule of thumb is that if it is any warmer than about 90°F under full load then there is a potential problem. A wet battery must have adequate ventilation for gassing and thermal dispersion.
Shock/vibration- this is impact and high frequency/resonance. Put a pad under it and secure it.
Electrolyte balance- they really do mean that 65/35 ratio (if you still have one using acid). Only add DI/distilled water because if the chemistry or conductivity of the fluid changes it will damage the cell.
Running undercharged- all batteries need a load/topping every once in a while.
The last thing (not listed because this is a system issue, it affects the battery) is system load and electromotive force during operation. The main reason this exists is because QS 9000 and the SAE are not under or subject to the NEC and IEEE.
(Remember an automotive engineer designed that system, not a licensed Electrical Engineer to any industrial code or standard)
Granted the voltage drop and impedance of a DC circuit given the run distances in a car is negligible in one realm, it can have an endothermic effect on a battery and greatly reduce service life.
In layman’s terms (not literally accurate but illustratively accurate for general conversation purposes and a good fundamental understanding)
A battery is a chemical storage device- you don’t actually charge a battery, you “excite” it. So during cycles you continuously “excite” it.
Understanding also that anytime you have heat- you have a loss.
So, when you pull power from a wet cell battery, it’s similar to squeezing a soaked sponge and several things happen concurrently.
The chemistry between the metals and electrolyte changes (back and forth depending on charge/discharge amounts)
Heat builds up in the fluid all the way to the poles and backs up due to resistance during flow- this extrudes chemicals and flexes the plates.
That’s the way they are designed to work so eventually even in the “perfect world” the chemistry will wear out and the plates will either develop micro fractures or the coatings on the plates will calcify and the reaction is weakened enough to kill the cell. This cannot be stopped because that’s just physics but it can be reduced drastically with a few simple tricks that every non SAE type application uses.
Battery- they make them smaller now to save space and weight (and BCI changed their metrics for ampacity). If your application allows, put the largest size battery possible and preferably a deep cycle. (Greater mass dissipates heat and handles those issues better and deep cycle batteries by design have thicker plates and greater spacing)
Ampacity- get the strongest possible (look at the reserve capacity) the bigger those numbers, the less potential it loses and reduces the effects in the charging/ discharging cycle.
Wire- There’s a lot of mystery and misunderstanding here. When you remove the skin effect and RF (which really don’t apply except in AC and signals) total resistance and ampacity is based on cross section because electrons flow on the OUTSIDE of a conductor. So, all of these SAE type connectors that flatten the wire create high resistance points. You will greatly enhance everything if you solder/braze the end solid (and if possible) use marine connections and solder the wire in with the greatest possible surface contact at the battery terminals. Obviously get the largest conductor you can fit based on physical size relative to the current load of the conductor. (See non SAE conductors crimp to the circumference, they don’t squash the wire like hitting a pipe with a hammer)
Connections- use dielectric compounds and as much surface contact as possible.
I do tons of thermography on switchgears, busses, transformers and panels- when you can actually SEE these issues, it will amaze you.
These methods and techniques although not common in the automotive industry are the standards in industry and they work well.
Hope that helps anyone wanting to experiment.
One of my first professional gigs was with Johnson Controls for their Interstate and Sears’s brands doing controlled testing.
Regardless where a wet celled battery resides (and external influences such as impact or overcharging) there are 4 things fatal to any battery.
Heat- The individual battery’s tolerance varies based on design parameters but a good rule of thumb is that if it is any warmer than about 90°F under full load then there is a potential problem. A wet battery must have adequate ventilation for gassing and thermal dispersion.
Shock/vibration- this is impact and high frequency/resonance. Put a pad under it and secure it.
Electrolyte balance- they really do mean that 65/35 ratio (if you still have one using acid). Only add DI/distilled water because if the chemistry or conductivity of the fluid changes it will damage the cell.
Running undercharged- all batteries need a load/topping every once in a while.
The last thing (not listed because this is a system issue, it affects the battery) is system load and electromotive force during operation. The main reason this exists is because QS 9000 and the SAE are not under or subject to the NEC and IEEE.
(Remember an automotive engineer designed that system, not a licensed Electrical Engineer to any industrial code or standard)
Granted the voltage drop and impedance of a DC circuit given the run distances in a car is negligible in one realm, it can have an endothermic effect on a battery and greatly reduce service life.
In layman’s terms (not literally accurate but illustratively accurate for general conversation purposes and a good fundamental understanding)
A battery is a chemical storage device- you don’t actually charge a battery, you “excite” it. So during cycles you continuously “excite” it.
Understanding also that anytime you have heat- you have a loss.
So, when you pull power from a wet cell battery, it’s similar to squeezing a soaked sponge and several things happen concurrently.
The chemistry between the metals and electrolyte changes (back and forth depending on charge/discharge amounts)
Heat builds up in the fluid all the way to the poles and backs up due to resistance during flow- this extrudes chemicals and flexes the plates.
That’s the way they are designed to work so eventually even in the “perfect world” the chemistry will wear out and the plates will either develop micro fractures or the coatings on the plates will calcify and the reaction is weakened enough to kill the cell. This cannot be stopped because that’s just physics but it can be reduced drastically with a few simple tricks that every non SAE type application uses.
Battery- they make them smaller now to save space and weight (and BCI changed their metrics for ampacity). If your application allows, put the largest size battery possible and preferably a deep cycle. (Greater mass dissipates heat and handles those issues better and deep cycle batteries by design have thicker plates and greater spacing)
Ampacity- get the strongest possible (look at the reserve capacity) the bigger those numbers, the less potential it loses and reduces the effects in the charging/ discharging cycle.
Wire- There’s a lot of mystery and misunderstanding here. When you remove the skin effect and RF (which really don’t apply except in AC and signals) total resistance and ampacity is based on cross section because electrons flow on the OUTSIDE of a conductor. So, all of these SAE type connectors that flatten the wire create high resistance points. You will greatly enhance everything if you solder/braze the end solid (and if possible) use marine connections and solder the wire in with the greatest possible surface contact at the battery terminals. Obviously get the largest conductor you can fit based on physical size relative to the current load of the conductor. (See non SAE conductors crimp to the circumference, they don’t squash the wire like hitting a pipe with a hammer)
Connections- use dielectric compounds and as much surface contact as possible.
I do tons of thermography on switchgears, busses, transformers and panels- when you can actually SEE these issues, it will amaze you.
These methods and techniques although not common in the automotive industry are the standards in industry and they work well.
Hope that helps anyone wanting to experiment.
My 1994 Miata battery made it more than 10 years. It was trunk mounted, not sure if gel/AGM but it was a nonspillable type battery.
I'd guess that it was a very high quality battery, but that it would never have lasted as long "under the hood".
I'd guess that it was a very high quality battery, but that it would never have lasted as long "under the hood".
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