Just realized I had never posted this here and a trip into the shed early this morning remindind me I needed to finish this article..
December 11, 2012
After having a discussion with one of my customers about leaving his battery charger on all winter, a practice I am certainly not a huge fan of, I decided to do this article.
On December 11, 2012 I charged this deep cycle battery, that had just ended its sixth year of use, using my bench top DC power supply. I charged the battery to 14.8V and 0.2A of "accepted current" which essentially means this battery was full.
December 11, 2012 @ 10 Minutes
I then carried the battery out to my garden shed, which is unheated, to mimic a boat during the winter here in Maine. I suppose I could have just carried it up the ladder, and into my boat, but no sense in breaking my back, the temps are the same.
At this point I took my first open circuit voltage reading about ten minutes after discontinuing the charge. It read 13.77V and represents a "surface charge" that has not yet dissipated.
December 11, 2012 - Shed
This is a shot of the shed with the battery sitting on the green box. The temps in here mimic that of our boat quite well.
In cold weather the self discharge of lead acid batteries slows dramatically to the point of nearly stopping. The colder the temps the slower the self discharge. In an area that has more temperate winters the rate of self discharge will be slightly faster.
December 14, 2012 - Resting Voltage
I placed the battery in the shed on Tuesday the 11th and on Friday the 14th I remembered to go take a voltage reading. As we can see here the temp was 19F and the open circuit resting voltage, after 4 days, was still reading well above full. This battery, when at full charge, reads about 12.72V to 12.73V. The 24 hour "rest" to get an open circuit voltage reading does not apply well when battery temps are below 77F....
The cold Maine winter temps have not even allowed the battery to drop to a "resting voltage" over a period of four days... As I mentioned cold weather drastically slows the effects of self discharge. I have noted this for years and years and years with the many boats in Maine that store batteries on-board all winter.
February 26, 2013 - Resting Voltage
OK so much for my "article".... Yes, I promptly got ADHD and totally forgot about the battery in the shed until today. Doh'..........
When I remembered about the lonely battery in the shed I shoveled a path through the snow and took a voltage reading.
As you can see this battery is still resting at 12.72V (which is FULL for this battery) after two and half months! December 11, 2012 to February 26, 2013 and still reading technically "full"... Ideally I wanted to get bi-weekly readings, but so much for that.
My point here is to illustrate why leaving your batteries on-board your boat, in the winter, does not lead to their instant demise, as many on the net would have you believe. I, and many in the cold Northeast, have done this for years and years. Our bank longevity is tremendous, and always has been very, very good.
A broken back, hip, leg or other mishap can end your season or sailing career. Lugging batteries on and off boats can be very dangerous, can ruin clothes, and is simply unnecessary unnecessary, if your reason for doing so is cold weather.
Some boat yards like to remove batteries because they can charge you for it! They do not do this because it is good for the batteries. Heck, MANY yards I go in use SUPER DUMB chargers in the battery storage rooms to keep your expensive batteries "topped up" in the heated building.. Most yards are doing you no favors by removing the batteries and "cooking them".... When doing so yards also know the batteries are in-fact disconnected from the vessel and it gives them peace of mind. Some insurance policies for boat yards require stored boats have the batteries 100% disconnected.
This particular Wal*Mart battery had recently ended its sixth year of deep cycle use and still performs at better than both CCA & MCA specifications based on both Argus and Midtronics analyzers. It also still puts up 94-96% of the stated Ah rating when 20 hour capacity tested. This battery had lived every winter on-board our boat uncharged except for the occasional "top up" charge a few times per winter. One winter I purposely did not charge it.
Cold weather is actually a good thing for the batteries, provided they are fully charged when entering storage. A fully charged battery will not freeze until approx -70F. I lived in Alaska, Fairbanks to be exact, and they have been using flooded lead acid batteries up there since they were invented. In most parts of this country we will never see the -60F they see in Fairbanks.. I Fairbanks you can spit and have it hit the ground frozen, not so in the rest of the country.
Lead acid batteries (AGM, GEL and FLOODED batteries are all lead acid) will lose very little voltage/charge in colder weather. If leaving batteries on board I much prefer to see them 100% disconnected from the vessel. They only occasionally need to be topped back up, if at all (depending upon how long your dry storage is).
I find this safer and more reliable than being left on permanent charge and unattended. I see far more problems when batteries are left charging, without any supervision, than I do when left fully charged, disconnected and resting (in cold weather). Perhaps once per month, if that, hit them with some good "bubbling" voltage then disconnect them again. If your temps moderate, or warm up into the 60's, feel free to hit them again.
Self discharge rates are directly dependent upon temperature. As the temperature climbs the self discharge rates also climb. As temps drop the self discharge rates and chemical reactions also slow. When the temps go sub 30F the self discharge crawls to a very, very slow pace.
When I say hit them with a good "bubbling voltage" this applies to flooded batteries. A good gassing voltage of 14.6V to 14.8V will get the electrolyte moving and minimize any stratification going on inside the battery from it sitting idle. It is a common misunderstanding that a constant float charge prevents stratification & sulfation. It will not always do this depending upon battery temps. The floating voltages are often too low to keep the electrolyte moving. This gassing or movement of the electrolyte is what helps limit stratification. Smart chargers that revert to absorption voltages every few weeks will get it moving. Sadly most "smart" chargers don't do this and are not really as "smart" as they think they are.
Still leaving batteries on-charge, connected and unattended can often result in dead banks, which is the exact opposite of the intended goal.. Power outages occur, cords get unplugged, breakers get tripped and not reset and the parasitic loads then go to work killing your bank.
Also be wary of some of the "trickle chargers" out there. Some of these, when un-pluged but still connected to the battery, will actually drain the battery they are connected to. I have had this happen to two customers. They would have been better to 100% disconnect them and not charge. Both banks were ruined.
Most "smart" chargers, or any smart enough to even consider leaving connected full-time, while unattended, will not restart if the battery voltage gets too low. This is a built in safety feature to prevent charging into an internally shorted battery but can mean the charger will not fire back up if the bank voltage has dropped too low..
So, power goes out, or the solar panel becomes occluded in snow/ice, and the parasitic loads of the charger, controller or other "always on" devices suck the bank down. Power comes on or the snow melts but now the battery voltage is below the safe turn on threshold and the battery continues to discharge until fully dead. This is not as rare an occurrence as it would seem. Power had been out three or four times over the winter here in Maine due to winter storms. Will your charger automatically re-boot? Have you tested this?
With a fully charged and 100% physically disconnected battery bank noting except time & temp can discharge it, and when it is cold, you've got plenty of time....
Oh Sh*t...........
This morning, September 9th 2013, I walked into the shed and realized a gas can had been set in front of my "experiment" and I had totally forgotten about it. Arghhh that damn ADHD.......:cussing:
What this means is the battery sat from Dec 11, 2012 to September 9, 2013 100% un-charged!!!!!!!!!!!!!! Doh'..........
Really, It Was Not My Fault...........
After seeing my battery sitting there I immediately went to the barn and grabbed my DVM. I was honestly figuring this battery was a goner. It tested with an open circuit voltage of 12.54V! This after sitting in a freezing cold then blistering hot shed throughout an entire Maine winter and hot summer.
I was a total disbeliever at the resting OCV of this flooded battery that had sat 100% uncharged for nearly 8 months. I grabbed my refractometer and performed specific gravity checks on each cell. To my amazement they all agreed, meaning each cell was still well balanced, and all agreed with the DVM about the SOC..
So, this perhaps causes one to wonder why there is all the concern around self discharge? Perhaps the reality is that due to the cold winter temps this battery really only saw two to three months of self discharge?
I have to assume that nearly 20-30 days of this summer saw the shed temps over 100F. It is uninsulated with a black roof and every time I went in to grab the mower it was a sweat box....
If we are to believe OCV and SG readings it puts this battery at approx 90% SOC after at least 8 months. Makes for interesting n=1 data, to say the least......
OK I'm off to charge and equalize this battery... Face palm.............
December 11, 2012
After having a discussion with one of my customers about leaving his battery charger on all winter, a practice I am certainly not a huge fan of, I decided to do this article.
On December 11, 2012 I charged this deep cycle battery, that had just ended its sixth year of use, using my bench top DC power supply. I charged the battery to 14.8V and 0.2A of "accepted current" which essentially means this battery was full.
December 11, 2012 @ 10 Minutes
I then carried the battery out to my garden shed, which is unheated, to mimic a boat during the winter here in Maine. I suppose I could have just carried it up the ladder, and into my boat, but no sense in breaking my back, the temps are the same.
At this point I took my first open circuit voltage reading about ten minutes after discontinuing the charge. It read 13.77V and represents a "surface charge" that has not yet dissipated.
December 11, 2012 - Shed
This is a shot of the shed with the battery sitting on the green box. The temps in here mimic that of our boat quite well.
In cold weather the self discharge of lead acid batteries slows dramatically to the point of nearly stopping. The colder the temps the slower the self discharge. In an area that has more temperate winters the rate of self discharge will be slightly faster.
December 14, 2012 - Resting Voltage
I placed the battery in the shed on Tuesday the 11th and on Friday the 14th I remembered to go take a voltage reading. As we can see here the temp was 19F and the open circuit resting voltage, after 4 days, was still reading well above full. This battery, when at full charge, reads about 12.72V to 12.73V. The 24 hour "rest" to get an open circuit voltage reading does not apply well when battery temps are below 77F....
The cold Maine winter temps have not even allowed the battery to drop to a "resting voltage" over a period of four days... As I mentioned cold weather drastically slows the effects of self discharge. I have noted this for years and years and years with the many boats in Maine that store batteries on-board all winter.
February 26, 2013 - Resting Voltage
OK so much for my "article".... Yes, I promptly got ADHD and totally forgot about the battery in the shed until today. Doh'..........
When I remembered about the lonely battery in the shed I shoveled a path through the snow and took a voltage reading.As you can see this battery is still resting at 12.72V (which is FULL for this battery) after two and half months! December 11, 2012 to February 26, 2013 and still reading technically "full"... Ideally I wanted to get bi-weekly readings, but so much for that.
My point here is to illustrate why leaving your batteries on-board your boat, in the winter, does not lead to their instant demise, as many on the net would have you believe. I, and many in the cold Northeast, have done this for years and years. Our bank longevity is tremendous, and always has been very, very good.
A broken back, hip, leg or other mishap can end your season or sailing career. Lugging batteries on and off boats can be very dangerous, can ruin clothes, and is simply unnecessary unnecessary, if your reason for doing so is cold weather.
Some boat yards like to remove batteries because they can charge you for it! They do not do this because it is good for the batteries. Heck, MANY yards I go in use SUPER DUMB chargers in the battery storage rooms to keep your expensive batteries "topped up" in the heated building.. Most yards are doing you no favors by removing the batteries and "cooking them".... When doing so yards also know the batteries are in-fact disconnected from the vessel and it gives them peace of mind. Some insurance policies for boat yards require stored boats have the batteries 100% disconnected.
This particular Wal*Mart battery had recently ended its sixth year of deep cycle use and still performs at better than both CCA & MCA specifications based on both Argus and Midtronics analyzers. It also still puts up 94-96% of the stated Ah rating when 20 hour capacity tested. This battery had lived every winter on-board our boat uncharged except for the occasional "top up" charge a few times per winter. One winter I purposely did not charge it.
Cold weather is actually a good thing for the batteries, provided they are fully charged when entering storage. A fully charged battery will not freeze until approx -70F. I lived in Alaska, Fairbanks to be exact, and they have been using flooded lead acid batteries up there since they were invented. In most parts of this country we will never see the -60F they see in Fairbanks.. I Fairbanks you can spit and have it hit the ground frozen, not so in the rest of the country.
Lead acid batteries (AGM, GEL and FLOODED batteries are all lead acid) will lose very little voltage/charge in colder weather. If leaving batteries on board I much prefer to see them 100% disconnected from the vessel. They only occasionally need to be topped back up, if at all (depending upon how long your dry storage is).
I find this safer and more reliable than being left on permanent charge and unattended. I see far more problems when batteries are left charging, without any supervision, than I do when left fully charged, disconnected and resting (in cold weather). Perhaps once per month, if that, hit them with some good "bubbling" voltage then disconnect them again. If your temps moderate, or warm up into the 60's, feel free to hit them again.
Self discharge rates are directly dependent upon temperature. As the temperature climbs the self discharge rates also climb. As temps drop the self discharge rates and chemical reactions also slow. When the temps go sub 30F the self discharge crawls to a very, very slow pace.
When I say hit them with a good "bubbling voltage" this applies to flooded batteries. A good gassing voltage of 14.6V to 14.8V will get the electrolyte moving and minimize any stratification going on inside the battery from it sitting idle. It is a common misunderstanding that a constant float charge prevents stratification & sulfation. It will not always do this depending upon battery temps. The floating voltages are often too low to keep the electrolyte moving. This gassing or movement of the electrolyte is what helps limit stratification. Smart chargers that revert to absorption voltages every few weeks will get it moving. Sadly most "smart" chargers don't do this and are not really as "smart" as they think they are.
Still leaving batteries on-charge, connected and unattended can often result in dead banks, which is the exact opposite of the intended goal.. Power outages occur, cords get unplugged, breakers get tripped and not reset and the parasitic loads then go to work killing your bank.
Also be wary of some of the "trickle chargers" out there. Some of these, when un-pluged but still connected to the battery, will actually drain the battery they are connected to. I have had this happen to two customers. They would have been better to 100% disconnect them and not charge. Both banks were ruined.
Most "smart" chargers, or any smart enough to even consider leaving connected full-time, while unattended, will not restart if the battery voltage gets too low. This is a built in safety feature to prevent charging into an internally shorted battery but can mean the charger will not fire back up if the bank voltage has dropped too low..
So, power goes out, or the solar panel becomes occluded in snow/ice, and the parasitic loads of the charger, controller or other "always on" devices suck the bank down. Power comes on or the snow melts but now the battery voltage is below the safe turn on threshold and the battery continues to discharge until fully dead. This is not as rare an occurrence as it would seem. Power had been out three or four times over the winter here in Maine due to winter storms. Will your charger automatically re-boot? Have you tested this?
With a fully charged and 100% physically disconnected battery bank noting except time & temp can discharge it, and when it is cold, you've got plenty of time....
Oh Sh*t...........
This morning, September 9th 2013, I walked into the shed and realized a gas can had been set in front of my "experiment" and I had totally forgotten about it. Arghhh that damn ADHD.......:cussing:
What this means is the battery sat from Dec 11, 2012 to September 9, 2013 100% un-charged!!!!!!!!!!!!!! Doh'..........
Really, It Was Not My Fault...........
After seeing my battery sitting there I immediately went to the barn and grabbed my DVM. I was honestly figuring this battery was a goner. It tested with an open circuit voltage of 12.54V!
This after sitting in a freezing cold then blistering hot shed throughout an entire Maine winter and hot summer.I was a total disbeliever at the resting OCV of this flooded battery that had sat 100% uncharged for nearly 8 months. I grabbed my refractometer and performed specific gravity checks on each cell. To my amazement they all agreed, meaning each cell was still well balanced, and all agreed with the DVM about the SOC..
So, this perhaps causes one to wonder why there is all the concern around self discharge? Perhaps the reality is that due to the cold winter temps this battery really only saw two to three months of self discharge?
I have to assume that nearly 20-30 days of this summer saw the shed temps over 100F. It is uninsulated with a black roof and every time I went in to grab the mower it was a sweat box....
If we are to believe OCV and SG readings it puts this battery at approx 90% SOC after at least 8 months. Makes for interesting n=1 data, to say the least......
OK I'm off to charge and equalize this battery... Face palm.............
