battery warmth

Post by **cadetchris** » Sat Dec 19, 2009 7:28 pm

just a quicky,
seeings as its getting cold, i thought this question would be of benefit to all.

how does one keep the battery warm during this cold period? so it keeps its charge for those cold starts in the mornings

Post by **aupickup** » Sat Dec 19, 2009 7:30 pm

dont know

i keeep my car in the garage now but its still cold

i have never had a battery failure cos of the cold so long as the battery is in good condition and not on its last legs

Post by **cadetchris** » Sat Dec 19, 2009 7:33 pm

my battery is a nice new shinny one, but still keeps losing its ummph. checked all connections, but it is quite cold in lincolnshire

Post by **billlobban** » Sat Dec 19, 2009 7:34 pm

I lived in Norway for a few years and we had a block heater which fitted in place of a core plug. On the same circuit was a trickle charger and an electric fan heater on a timer. Worked great when for months on end it was well below zero. No ice started first time and the heater worked straight away.
The trickle charger might be a good idea for the British winter

Post by **aupickup** » Sat Dec 19, 2009 7:44 pm

well i have had no problems at all, allways starts with a healthy turn of the starter

Post by **PSL184** » Sat Dec 19, 2009 7:51 pm

Never had a problem either. Battery voltage is not temp dependant, ie if it gives 12 volts at +30 it will give 12 volts at -30 also. However, if a cell is down then the temp will effect the performance and the cold weather will soon finish off a battery that is not 100% in the first place.

Post by **bmcecosse** » Sat Dec 19, 2009 9:37 pm

Battery output DOES depend on low tempearture - but a nEW battery should be fine. You could always take it indoors at night - pop it in the oven ??

Post by **ssnjimb** » Sat Dec 19, 2009 9:57 pm

Not a gas oven lol

Jamie

Post by **PSL184** » Sun Dec 20, 2009 12:06 am

bmcecosse wrote:Battery output DOES depend on low tempearture

Not if it is in good condition (as you went on to say and which I already stated). Go and measure your voltage outside now then again after its been inside all night and it will be the same....

Post by **MarkyB** » Sun Dec 20, 2009 8:01 am

According to this site, and my understanding, BMC is right.http://www.mpoweruk.com/performance.htm
Temperature Characteristics

Cell performance can change dramatically with temperature. At the lower extreme the electrolyte may freeze setting a lower limit on the operating temperature, while at the upper extreme the active chemicals may break down destroying the battery. In between these limits the cell performance generally improves with temperature. See also Thermal Management and Battery Life for more details.<br>

<br>

There are other factors at work too like the oil being thicker and the petrol less volatile.
(I made the last one up but it could be true)

Post by **PSL184** » Sun Dec 20, 2009 12:40 pm

Well that is certainly a great way to confuse!
The page you linked to talks mainly about lithion batterys, not lead acid and yes, temp will effect charge and discharge rate of batterys, but that's not what the question was? The question was "how to keep a battery warm overnight to maintain its charge". Answer is simply that you don't need to if the battery is in top condition as the voltage of the battery will be the same regardless of temp!
Conditions that will effect battery votage at this time of year due to the lower temp are shorter runs esp if the car has a dynamo. As the charge rate will be lower in lower temps the battery may not be getting fully recharged and therefore the battery voltage will be down anyway (because of temp effecting charge rate - not stored voltage) and if one or more cells are underperforming they won't get an effective charge either.
Also, I fail to see how thicker oil or lower fuel volatility will effect battery voltage

I'd be happy to expand on battery technology (it is part of my core business) and can highly recommend these http://www.optima-batterien.eu/home.html but you will need an alternator

Post by **billlobban** » Sun Dec 20, 2009 2:51 pm

MarkyB wrote: There are other factors at work too like the oil being thicker

Whilst it has nothing to do with battery voltage oil viscosity does vary with temperature. When it gets very cold, below minus 15 celcius the oil in the sump gets appreciably thicker. It is therefore harder to turn the engine over. When added to the rigours of winter use (especially if you dont have an alternator) the battery may not be in the best of conditions for a cold winter start so charging the battery overnight occasionally does no harm.
I know little of battery technology but from experience I know a considerable amount about cold weather and a half charged battery is a not a good idea on a cold winters morning.

Post by **rv8** » Sun Dec 20, 2009 3:06 pm

voltage at hot or cold temps isnt the factor, current is the key(amps)

Post by **PSL184** » Sun Dec 20, 2009 4:14 pm

rv8 wrote:voltage at hot or cold temps isnt the factor, current is the key(amps)

That is correct - referred to as amp hours or "Ah" which is the ability of the battery to sustain a current draw over a period of time. Therefore, if your car always starts 1st turn of the key, no need to worry about it - If it takes a number of churns on the starter then the capacity of the battery is been diminished until the point it is "dead" if the engine has not started. Incidentally this part of the battery (its "capacity") IS temp dependant....

Post by **billlobban** » Sun Dec 20, 2009 4:30 pm

PSL184 wrote: Incidentally this part of the battery (its "capacity") IS temp dependant....

Was not the original question about whether or not the battery would perform better if kept warm which it fairley obviously does.
So right again BMC

Post by **PSL184** » Sun Dec 20, 2009 5:24 pm

billlobban wrote:
PSL184 wrote: Incidentally this part of the battery (its "capacity") IS temp dependant....
Was not the original question about whether or not the battery would perform better if kept warm which it fairley obviously does.
So right again BMC

Not quite (although continue your worshipping if you wish). It is the rate of charge which effects the capacity of the battery and it is this aspect which is temp dependant - which is why I mentioned it before about short runs and a dynamo. If you charge slower at warmer temps the capacity will be higher - and as the battery is warmed by the engine when its running it makes no sense to keep it warm when its not being charged. As you all obviously know more about my job than I do I will retire safe in the knowledge that experts will continue to progress battery tech long after I am gone * - Simples !!!

* That bit was tongue in cheek sarcasm BTW but I wasn't sure if it read that way

Post by **cadetchris** » Sun Dec 20, 2009 7:23 pm

well i believe the only thing i can say is. "can of worms"

however, as the initial question asked, how do i keep the battery warm during these cold times?

Post by **PSL184** » Sun Dec 20, 2009 7:35 pm

Put a blanket on it for as much good as it will do

Post by **billlobban** » Sun Dec 20, 2009 7:51 pm

Please dont take the hump I am really interested but confused you state in one post

PSL184 wrote: Incidentally this part of the battery (its "capacity") IS temp dependant....

so does this mean that the battery will give a higher output for a given state of charge when its warm. (excuse the ignorance I'm a simple mechanical engineer)

Post by **PSL184** » Sun Dec 20, 2009 9:12 pm

Bill, In general terms, yes, a warmer battery will have a higher capacity and vice versa. But remember, capacity relates to "Ah" not voltage so the voltage will still be the same but the ability of the battery to deliver energy for a prolonged period of time will be diminished in the cold. Hence the original statement that a "good" battery will start a "good" car without any problems whatever the weather. The original poster states his battery is new but does not state the Ah rating - this could be quite low and coupled with a problematic starting car would give the indication that the battery was going flat before the car started. Keeping the battery warm over night will not help to maintain "capacity" as capacity is loaded into the battery during its charge cycle which will be when the car is running. The reference to capacity being temp dependant is that a warmer battery will charge more efficiently and therefore gain more capacity when being charged. Hope this helps......