Battery Temperature vs Cycle life

Home Power mag is a great resource for folks going cruising , as their info is excellent and slanted to the "off the grid" folks.

The new issue brings up a fact that it would seem many boaters (and Naval Arch) never bothered to contemplate.

Battery Location,

" Chose a location with moderate temperatures (77F is ideal) is critical for battery longevity.

For every 18F increase in temperature the battery experiences ,the number of available cycles drops by HALF!

For example a battery rated at 3600 cycles at 77F (or approx 10 years , at 1 cycle per day) it would then be expected to last 1800 cycles or about 5 years if installed at a climate of 95F"

A good marine engine space will be under 110F with GREAT! powered ventilation , many go far higher.

Since many folks have the batts inside the engine space that is probably closer to 125F , its is no wonder that our batt sets die early.

For folks doing a rebuild , that have a chance to locate the batt sets out of the engine spaces , it would seem a grand idea!

FF

Temperature is a concern, but I think for most boats, weight distribution, ease of access for maintenance, adequate ventilation, and short cable runs would be the main concerns.

FF: Some interesting numbers on how the battery temperature affects the number of duty cycles. I'm not sure how often we cycle our batteries in a hot engine room though. We spend more than 90% of out time at anchor and the engine room is probably close to the water temperature which in most cases is cooler than the ambient/cabin temp. When we are under way our DC loads are being powered off the alternator so we aren't drawing them down.

My guess would be just sitting in a hot location speeds the internal decline of the batt.

Few hours of ER heat per year might be enough for early death , might not.

A ventilator could be added to the battery box. It would keep the box cooler than the engine room when motoring, like this one Zephyr Industries Battery Box Ventilator.

A cheaper option could be to buy a bimetallic switch at Grainger, which turns on a computer fan to ventilate the battery box.

here is another cheap home made ventilator:

http://www.pssurvival.com/PS/Batter...ery-Box_Ventilation_Fan_Construction_2010.pdf

When my engines are running, the fresh air drawn in through the engine room vents keeps the temperature in there very close to ambient. The problem is when I turn off the motors and the heat soaks out of the blocks.

automotive manufactures are getting more conserned over battery temp and duty cycles as they try to minimise battery size for packageing and cost

Here is another good ventilation solution from Smartgauge, it reduces the fan speed to half once the float begins:

SmartGauge Electronics - Battery compartment venting - The new way

Battery temperature also signficantly affects battery charge acceptance rates. That is why the best battery chargers and alternator regulators are equipped with battery temp sensors. It is true that engine room temps typically rise once engines are shut down, as Maike at post #7 says. Running exhaust fans after shutdown for 30minutes or so is a very good idea