Batteries

[WJM]

Just a very general question; the performance of my battery bank is a little disappointing just now. They were installed brand new in June and have worked totally to expectations ever since - until this weekend. They seem to reach near empty very quickly. They sit on top of the swim where I guess it must be very very cold!

 

Would I be right in assuming that such very cold weather will reduce heir performance?

 

 

 

(As an aside, this cold weather allows much higher engine revs without the engine overheating)

[Naughty Cal]

Batteries almost always fail in the winter. They cant hold as much charge in the cold.

[alan_fincher]

Removed.

 

Slightly misread the post, which made my question less relevant.

Edited December 22, 2009 by alan_fincher

[David Schweizer]

Just a very general question; the performance of my battery bank is a little disappointing just now. They were installed brand new in June and have worked totally to expectations ever since - until this weekend. They seem to reach near empty very quickly. They sit on top of the swim where I guess it must be very very cold!

 

Would I be right in assuming that such very cold weather will reduce heir performance?

 

 

 

(As an aside, this cold weather allows much higher engine revs without the engine overheating)

I am sure that an expert could give the technical information, but battery performance does drop significantly at sub-zero temperatures. One of the reasons why your battery bank should be bigger than the thoeretical (normal ambient temp)requirement.

[alan_fincher]

Just a very general question; the performance of my battery bank is a little disappointing just now. They were installed brand new in June and have worked totally to expectations ever since - until this weekend. They seem to reach near empty very quickly. They sit on top of the swim where I guess it must be very very cold!

 

Would I be right in assuming that such very cold weather will reduce heir performance?

What batteries do you have, (how many and what capacity), and what are you attempting to run off them, and for how long?

 

I'd not expect ones bought as recently as you say to be causing problems yet, unless you are either close to the edge on total capacity for your needs, or simply not charging them enough.

 

Stating the bleeding obvious perhaps, but in winter you will spend a lot less time boating, (I'm guessing), and need to run lights and the like a whole lot longer. The whole balance between how much you are charging, and discharging the batteries can get very distorted, even if their performance were in no way degraded by the cold.

[Robbo]

Can you provide any reliable scientific source to actually support that statement?

 

Wikipedia is your friend http://en.wikipedia.org/wiki/Battery_(electricity) .

 

Batteries are just a chemical reaction, so temperature does effect them.

 

Storing batteries at lower temperatures will prolong their charge, but there discharge is also slower, room temperature is best for charging and discharging.

[barge sara]

Would I be right in assuming that such very cold weather will reduce heir performance?

 

Yes,

Have a look here Curtis Battery book

Figure 13 seems to indicate that capacity at freezing (32F) is about 70% of capacity at 80F.

[casper ghost]

Yep, I suffer from lack of battery power through the winter, the lights are on more, stay inside boat more, watching rubbish tv or on this laptop..

[Keeping Up]

Also, the lower the temperature the higher the charging voltage you must apply. If your charging system does not have any temperature compensation built in, you may not be charging yuor batteries fully when it is very cold.

[WJM]

"battery performance does drop significantly at sub-zero temperatures"

 

That is really the info I was after, thanks. There is no actual problem, they last long enough for their purpose, it is just that they have been getting closer to empty than they normally do. I wanted to be sure there was no more likely problem that I need to think about.

[bottle]

Just a small question, when you say empty you do mean 50% soc? I hope. (state of charge).

[NB Alnwick]

Batteries almost always fail in the winter. They cant hold as much charge in the cold.

 

I always used to think this was 'Sod's Law' because my old car batteries always failed when needed most but, in truth, it is a fact that at low temperatures they perform less efficiently and the same low temperatures often mean that we are demanding more from them and it is the combination of these elements that leads to premature failure.

[Naughty Cal]

I always used to think this was 'Sod's Law' because my old car batteries always failed when needed most but, in truth, it is a fact that at low temperatures they perform less efficiently and the same low temperatures often mean that we are demanding more from them and it is the combination of these elements that leads to premature failure.

 

Thats why there are so many cars with failed batteries in the winter. They may just scrape through the summer but come winter they are useless.

[Keeping Up]

The one in my car always fails in the summer - because it goes flat while I'm away boating

[WJM]

"Just a small question, when you say empty you do mean 50% soc? I hope. (state of charge)."

 

 

 

I just use a voltmeter - the voltage has dropped to 9v at times.

[Keeping Up]

"Just a small question, when you say empty you do mean 50% soc? I hope. (state of charge)."

 

 

 

I just use a voltmeter - the voltage has dropped to 9v at times.

That is too low if it's a no-load voltage, it is effectively empty. Your batteries will be suffering at that voltage

[WJM]

"That is too low if it's a no-load voltage, it is effectively empty. Your batteries will be suffering at that voltage"

 

 

Yip - that was my interpretation of a 9volt reading - on my £4.99 eBay Voltmeter!

[Justme]

"That is too low if it's a no-load voltage, it is effectively empty. Your batteries will be suffering at that voltage"

 

 

Yip - that was my interpretation of a 9volt reading - on my £4.99 eBay Voltmeter!

 

 

OK I guess you dint get the hint.

 

YOU ARE KILLING YOUR BATS

 

Never go below 12.2v ish

(off load)

[WJM]

Thank you. I did know that.

 

Before I started into an investigation into the cause, I wanted to be clear if the cold weather was playing an important part. Clearly it is.

[Sir Nibble]

My word!

I have known for many years that the cold slows down the electro chemical reaction in batteries. That's why their starting performance suffers, they're not any less charged; they just cannot output FAST enough. I have never heard before thet the actual capacity would be effected, though it naturally follows I suppose that overall efficiency would fall. Even "winter" settings for charge ring a bell in distant memories of split field dynamos with four bobbin regulators.

Nonetheless, if there is (and I do not doubt it) a factor in this directly attributable to the cold effecting the battery chemistry, then it is so slight as to have escaped my notice in 35 years working with this sort of stuff.

Almost certainly the difference is in a seasonal imbalance of charge and discharge. After all, we all know don't we that the fuel bill for a winter quarter is larger than in summer don't we?

[johnjo]

The one in my car always fails in the summer - because it goes flat while I'm away boating

 

Have you tried one of these on Ebay £9.99 inc:

 

Granny & eggs may come to mind, but please don't bite

 

http://cgi.ebay.co.uk/12v-Solar-Battery-ch...=item3ca89c49fe

[Keeping Up]

Have you tried one of these on Ebay £9.99 inc:

 

Granny & eggs may come to mind, but please don't bite

 

http://cgi.ebay.co.uk/12v-Solar-Battery-ch...=item3ca89c49fe

Thanks for the suggestion, but I do actually have a solar charger - and it's a good one, made by Exide. It seems that my car just consumes so much current when it is left that the charger, which I had placed on the rear parcel shelf to get the maximum amount of sunshine, still could not produce enough current to keep the battery topped up (and yes it was connected directly to the battery terminals). Having wrecked two batteries in two years, it seems the only answer is for me to disconnect the battery when I leave - although that does cause its own set of problems. Apart from the fact that the alarm automatically goes off when I reconnect it, there are more things than you could imagine that are controlled by the engine management computer and which need to be manually reset or recalibrated, not just the radio but also including all the door locks, all the windows and the even seat positions.

[nb Innisfree]

Our batts perform no differently in the winter, guess it's down to them being inside.

[Smelly]

Thanks for the suggestion, but I do actually have a solar charger - and it's a good one, made by Exide. It seems that my car just consumes so much current when it is left that the charger, which I had placed on the rear parcel shelf to get the maximum amount of sunshine, still could not produce enough current to keep the battery topped up.

 

A dicky bird told me on another forum that glass is quite bad at transferring the radiation that PV panels like. I'll leave that open to the floor.

 

As to the OP, our batteries may be knackered but they seem more reluctant in colder climes... I wonder whether they'll sulphate as quickly in near zero temps...

[ditchcrawler]

"That is too low if it's a no-load voltage, it is effectively empty. Your batteries will be suffering at that voltage"

 

 

Yip - that was my interpretation of a 9volt reading - on my £4.99 eBay Voltmeter!

If you are relying on a £4.99 meter to tell you that you areonly down to 12.2 volts in warmer times you could well be pushing your luck, how do you work out you have fully recharged them?