Storage batteries and heat

[redsky49]

My house bank is located low in the engine compartment of my boat, so it regularly sees high temperatures. Is there a battery type that is less affected by high temperatures, or the corollary, is one type of battery particularly affected by high temperatures?

Is there any analytical data out there, or is it all anecdotal?

TIA

[redsky49]

Hmm... Lots of views, but no insights.

My suspicion is that during elevated temperatures all batteries suffer degradation regarding life cycles, but also enjoy momentary increases in capacity; and that all battery types act pretty much the same. From what I can discover, that seems to be the consensus.

Doesn't appear to be any actual testing data available on-line to dispute this.

[sailinglegend]

At 25 Deg C batteries gas at 14.4 volts, at 40C they gas at 13.98v - so no sealed batteries should be anywhere near the engine as temperatures of over 40C are soon reached.

Open wet lead acid batteries would be better as they can of course be topped up with water.

[belizesailor]

Cooler is better. Not only do they off gas more at higher temps, but batteries can be charged faster at lower temps. Is your charger temperature compensated? If not, you could be cooking your batteries.

[GordMay]

Batteries intended for high-temperature applications often use a lower initial specific gravity electrolyte (weaker acid) than those intended for use at normal temperatures.

Batteries can be discharged over a large temperature range, but charge temperature should be limited to between 10°C and 30°C (50°F and 86°F).

Heat is the worst enemy of most batteries, including lead acid. Adding temperature compensation on a lead acid charger, to adjust for temperature variations, prolongs battery life by up to 15 percent.

The recommended compensation is 3mV per cell, per degree Celsius, applied on a negative coefficient; meaning that the voltage threshold drops as the temperature increases.

Typically recommended Float Voltage thresholds, representing a 30mV correction per cell per 10°C (18°F):
Normal 25°C (77°F): 2.30V/cell (13.8V)
Hot 35°C (95°F): 2.27V/cell (13.62V)
Cool 15°C (59°F): 2.33V/cell (13.98V)

[GordMay]

Excerpted from ➥ Float Charging - Batterytender.com

“... Battery Charger Output Voltage vs. Temperature (Temperature Compensation):
This battery charger characteristic probably has more influence on the battery than line regulation. Even if a battery is kept at its ideal float voltage, and if that ideal voltage is compensated properly for temperature, an increase of only 7 °C to10 °C can still cut the battery life in half, assuming that the higher temperature remained for the entire observation period.
Short-term fluctuations in temperature have little impact on battery life, unless the temperatures are extreme. In general, cold is good, hot is bad, very cold is better (but too cold can be worse), and very hot is worse.
At the extreme cold end, bad things can happen as well, but those bad things are just dramatic reductions in the battery performance.
At the extreme hot end, while the battery is charging, it can emit dangerous gasses. The ideal temperature compensation range for lead acid batteries is typically in the range of 2.5 to 4.0 millivolts per 2-volt cell, per degree Centigrade. The temperature compensation coefficient is also negative, meaning that the change in charging voltage is in the opposite sense as the change in temperature. If the temperature goes up, the charging voltage comes down and vice-versa ...”

Some more light reading about Battery Temperature Compensation

➥ Battery Temperature Compensation

➥ http://www.global-download.schneider-electric.com/852575A6007E5FD3/all/2C44FF0BC409DA0D852576F0006997F0/$File/sp3.1_qa_v3.pdf

➥ http://www.tekrispower.com/pdfs/xant...20Charging.pdf

➥ http://www.boatelectric.com/VictronD...0and%20AGM.pdf

[redsky49]

Originally Posted by belizesailor

Cooler is better. Not only do they off gas more at higher temps, but batteries can be charged faster at lower temps. Is your charger temperature compensated? If not, you could be cooking your batteries.

Yes, charger utilizes temperature compensation.

"This battery charger characteristic probably has more influence on the battery than line regulation. Even if a battery is kept at its ideal float voltage, and if that ideal voltage is compensated properly for temperature, an increase of only 7 °C to10 °C can still cut the battery life in half, assuming that the higher temperature remained for the entire observation period."

The key here is that the elevated temperatures are only for the period when the engine is operating. In my case, my diesel auxiliary sailboat only sees engine operation, on average, less than 2% (probably far less) of the time on an annual basis. Additionally, my batteries are lower than the engine and extend away from the engine in an end-to-end arrangement so heat soak is less of an issue than it might be.

This year I am going to monitor the actual engine room temps at both high and low heights and see what actually is occurring. I am in the process of changing over from gel cells to wet, and will try to record my experience for anyone who might be in the same boat

My sense is that there is an overwhelming amount of anecdotal information, second hand opinion, and outright misinformation circulating out there regarding batteries. If you exercise some common sense, any battery will work remarkably. Case in point, my current Prevailer gel cell 4Ds range in age from six to eleven years. The oldest batteries have diminished in capacity and are now starting to bulge/leak. I have certainly gotten my money's worth!

[CharlieJ]

My sense is that there is an overwhelming amount of anecdotal information, second hand opinion, and outright misinformation circulating out there regarding batteries.

True enough. However; the battery manufacturers' websites generally have detailed information and will often provide graphs showing loss of cycle life as a function of environmental temperature.

Charlie

[Florida Mike]

Why not just add power ventilation to the battery box? It seems that with so not only the heat problem but would also get rid of explosive gases. Just my two cents, Mike.

[btrayfors]

Mike beat me to it: definitely think about engine room ventilation; even a 3-4" muffin fan (like on a computer) blowing across the batteries would help.

Also, borrow or buy a laser temperature meter (they're cheap these days). Measure the temp of the batteries at various points, including: engine off, engine running for 15 minutes, engine running for several hours. Record also the ambient temperature.

That will give you a pretty good idea of what's going on.

And....if your gels lasted as long as they have, I'd say you really don't have a problem to worry about the way you use your boat.

Just be careful to watch the electrolyte levels on the new flooded batteries. I use WaterMiser caps to reduce water loss; well worth the investment and they don't have to be removed when equalizing batteries as do the HydroCaps.

Bill

[redsky49]

One of the nice things about an older center cockpit boat is the possibility to have a real engine room, small certainly, but adequate. It also allows, in my case, for no less than five access doors to the engine, one of which is usually open when motoring for extended periods.

Despite that, a small supply air fan, wired in to the engine start wiring makes sense. I will just have to think through the location so as not to introduce a path for noise into the boat, or to create any incidental problems.

I do have an IR thermometer. It just needs to move from work place to play space. It will be interesting to see the results.

Do watermiser caps raise the height of the batteries substantially? How much do they reduce the need to water the batts?

My past experience with paralleled Trojan SC225 flooded batteries was that water needed to be added every couple months. Not a terrible burden, but my current battery installation is more difficult to access, and if I could lengthen the service periods, that would be good. I also am going to try to raise (very slightly) the charging voltages, so I may use more water than planned.

Appreciate all the input!!!

[FlyingCloud1937]

I have my batteries connected to a voltage switch, as soon as the voltage reaches 14.4 volts an outside fan comes on and stays on until the battery voltage drops to 13.2.

I also have a temp switch that comes on and ducts a seperate outside air fan to my alternators, as soon as the temp rises abvoe 120 F , and off at 100F.

In this day and age it is very simple to extend the life of most heat sensitive devices.

Lloyd

[RUSTYNAIL]

If you like following engine room temperatures for a long period, or short period, one thing I use is a LASCAR EL-USB data logger, temperature monitor. It's a USB probe, very small that you set up on a computer, it has a small battery, and it will take thousands of samples. Every second, 5 seconds, minutes, hours, days, etc. They also have current and voltage monitors. Just another toy, but it gives you an idea what's happening if you are trying to fine tune a battery system at the engineering level.

[redsky49]

Two great suggestions from Flyingcloud and Rusty.

As a retired engineer, never pass up on a chance to make things overly complicated, or add a new gadget

I am looking forward to seeing what the actual temperatures - both engine space and batteries - are during extended motoring. For some inexplicable reason, I have not checked this before. Logging the temps should be interesting, and hopefully, informative.

Having had some exposure in the past to industrial ventilation (though on a much bigger scale) this will be a nice project.

Thanks!!