Batteries

[motion30]

Do batteries need to be exercised or.are they happy staying on a float charge for an extended. Of time ?

[btrayfors]

Most lead-acid batteries (flooded, AGM, gelled) will benefit from being exercised.

New batteries off-the-shelf, for example, cannot provide their rated capacity output. A 225 AH-rated Trojan T-105, e.g., may only be able to provide 200AH or even less until it is "exercised" a few times and, preferably, undergone an equalization cycle (with 15.5V or so applied for several hours).

Thereafter, batteries will benefit from frequent full charging at absorption-voltage levels and, for flooded and some AGM batteries, occasional equalization.

Also, they will last longer and retain their high capacity capability much longer if they are floated at, e.g., 13.6-13.8VDC for flooded batteries.

The above is not an opinion. Over three years of battery testing, including on 10 of my own T-105s and four AGM golf-cart batteries, support these statements.

MaineSail or others who have done careful testing may wish to chime in here.

Bill

[Kettlewell]

I have not done "careful testing," but in my experience older batteries can often be rejuvenated somewhat with a fairly deep discharge and then a full charge. I think more batteries die from prolonged periods of sitting undercharged than die from prolonged periods of float charging, as long as you don't let the water level get too low.

[btrayfors]

Originally Posted by Kettlewell

I have not done "careful testing," but in my experience older batteries can often be rejuvenated somewhat with a fairly deep discharge and then a full charge. I think more batteries die from prolonged periods of sitting undercharged than die from prolonged periods of float charging, as long as you don't let the water level get too low.

Yes, the operable conditionality being, "rejuvenated somewhat" :-)

Sitting undercharged results in sulfation of the plates, i.e., buildup of PbSO4 crystals on the plates. Over time, these become embedded in the plates so that even vigorous charging won't dislodge them. The result is to deny a portion of the plates the ability to store and release energy....i.e., reduction in AH capacity.

Other things happen as well, including stratification of the electrolyte which can also result in a loss of capacity.

The voltage level during the float cycle is important. For example, a battery floated at 13.2VDC over a long period of time will still result in some level of sulfation and loss of capacity. If the time period isn't too long, some of this can be mitigated by exercising and equalization.

Once again, to be perfectly clear, we're talking here about battery capacity which is not the same thing as "holding a charge" or "maintaining a voltage". Many folks mistakenly believe that just because their batteries will "maintain a charge" they are not losing capacity.

Bill

[Forever Freedom]

Smart chargers, such as the higher specification CTEK and Victron models, use a pulse charge system after every 10 days or so at Float, specifically to prevent stratification of the electrolyte and attendant sulphating.

[btrayfors]

Originally Posted by Forever Freedom

Smart chargers, such as the higher specification CTEK and Victron models, use a pulse charge system after every 10 days or so at Float, specifically to prevent stratification of the electrolyte and attendant sulphating.

I'm not sure about all chargers, but my programmable Victron MultiPlus 120/2500/120 has what they call a "repeat absorption" phase, not "pulse charging".

After a specified period of time, the charger reverts to the absorption voltage for a specified time, then reverts to the float charge voltage.

And, to further complicate things, there are two levels of "float charge". One of these is programmable and is the one the charger goes to after finishing the absorption phase. The other is reverted to if there has been no activity for a given time period, and is not adjustable in the latest software version. I believe Victron calls this the "storage" cycle and is fixed at 13.0VDC.

My Victron is set to do the "repeat absorption" cycle every other day for 30 minutes.

Bill

[tartansail]

Originally Posted by btrayfors

Most lead-acid batteries (flooded, AGM, gelled) will benefit from being exercised.

New batteries off-the-shelf, for example, cannot provide their rated capacity output. A 225 AH-rated Trojan T-105, e.g., may only be able to provide 200AH or even less until it is "exercised" a few times and, preferably, undergone an equalization cycle (with 15.5V or so applied for several hours).

Thereafter, batteries will benefit from frequent full charging at absorption-voltage levels and, for flooded and some AGM batteries, occasional equalization.

Also, they will last longer and retain their high capacity capability much longer if they are floated at, e.g., 13.6-13.8VDC for flooded batteries.

The above is not an opinion. Over three years of battery testing, including on 10 of my own T-105s and four AGM golf-cart batteries, support these statements.

MaineSail or others who have done careful testing may wish to chime in here.

Bill

I have seen this statement about the need for new batteries to be "exercised" in this and other threads. What is the "exercise" actually doing that improves the battery's performance? (I'm not disagreeing with the need. I'm just not clear what is happening inside an LA cell that makes a few deep cycles increase the battery's capacity.)

[btrayfors]

Originally Posted by tartansail

I have seen this statement about the need for new batteries to be "exercised" in this and other threads. What is the "exercise" actually doing that improves the battery's performance? (I'm not disagreeing with the need. I'm just not clear what is happening inside an LA cell that makes a few deep cycles increase the battery's capacity.)

Very good question. I don't have any precise data on this, but can speculate a bit, especially with respect to batteries which are in service.

For new batteries, I believe that the less-than-full-capacity results from their being inactive and usually not under charge since they were filled at the factory warehouse.

Once filled, batteries begin to sulfate unless kept under a healthy charge and exercised. There is a wide variation in time from manufacture to warehousing, to shipment to the distributor, to actual sale, to installation and use. Nigel Calder has measured as much as a 30% difference in capacity of "new" lead-acid batteries.

Flooded batteries have a high self-discharge rate and, unless kept under full charge, will begin to sulfate. I have personally measured wide variations in AGM batteries new on-the-shelf at West Marine, and these have a very low self-discharge rate.

In any case, there is plenty of evidence that letting batteries sit under less than full charge and without "exercising" isn't good for them. Here's what Trojan says re: the capacity of new batteries:

Quote
06

What to Expect from your Trojan Battery

î
A new deep-cycle battery will not deliver its full rated capacity. This is normal and should be expected as it takes time for a deep-cycle battery to reach maximum performance or peak capacity.

î
Trojan’s batteries take between 50 – 100 cycles to work up to providing full, peak capacity.


Unquote

Wow...50-100 cycles!!

Bill

[tartansail]

Originally Posted by btrayfors

Very good question. I don't have any precise data on this, but can speculate a bit, especially with respect to batteries which are in service.

For new batteries, I believe that the less-than-full-capacity results from their being inactive and usually not under charge since they were filled at the factory warehouse.

Once filled, batteries begin to sulfate unless kept under a healthy charge and exercised. There is a wide variation in time from manufacture to warehousing, to shipment to the distributor, to actual sale, to installation and use. Nigel Calder has measured as much as a 30% difference in capacity of "new" lead-acid batteries.

Flooded batteries have a high self-discharge rate and, unless kept under full charge, will begin to sulfate. I have personally measured wide variations in AGM batteries new on-the-shelf at West Marine, and these have a very low self-discharge rate.

In any case, there is plenty of evidence that letting batteries sit under less than full charge and without "exercising" isn't good for them. Here's what Trojan says re: the capacity of new batteries:

Quote
06

What to Expect from your Trojan Battery

î
A new deep-cycle battery will not deliver its full rated capacity. This is normal and should be expected as it takes time for a deep-cycle battery to reach maximum performance or peak capacity.

î
Trojan’s batteries take between 50 – 100 cycles to work up to providing full, peak capacity.


Unquote

Wow...50-100 cycles!!

Bill

Thanks, Bill. It makes sense that the batteries are going to be at differing states of charge and may have been sitting for an extended time. However, that sounds like an argument for "equalize", not "exercise". (There's a slogan in there somewhere.)

Interesting to read that statement from Trojan. It speaks to their expected longevity that they're not even broken in for 50-100 cycles.

[FlyingCloud1937]

Originally Posted by btrayfors

Very good question. I don't have any precise data on this, but can speculate a bit, especially with respect to batteries which are in service.

For new batteries, I believe that the less-than-full-capacity results from their being inactive and usually not under charge since they were filled at the factory warehouse.

Once filled, batteries begin to sulfate unless kept under a healthy charge and exercised. There is a wide variation in time from manufacture to warehousing, to shipment to the distributor, to actual sale, to installation and use. Nigel Calder has measured as much as a 30% difference in capacity of "new" lead-acid batteries.

Flooded batteries have a high self-discharge rate and, unless kept under full charge, will begin to sulfate. I have personally measured wide variations in AGM batteries new on-the-shelf at West Marine, and these have a very low self-discharge rate.

In any case, there is plenty of evidence that letting batteries sit under less than full charge and without "exercising" isn't good for them. Here's what Trojan says re: the capacity of new batteries:

Quote
06

What to Expect from your Trojan Battery

î
A new deep-cycle battery will not deliver its full rated capacity. This is normal and should be expected as it takes time for a deep-cycle battery to reach maximum performance or peak capacity.

î
Trojan’s batteries take between 50 – 100 cycles to work up to providing full, peak capacity.


Unquote

Wow...50-100 cycles!!

Bill

I can shed some light on the subject of commissioning a battery bank. A new battery have formed plates.

If you were to cut open a brand new battery and pull a set of plates they will be very smooth and shiny.

Now if you dissect the same battery after a 100 plus cycles you will see that there the lead is very pores and rutted, the plates will have almost twice as much surface area for the chemical reaction to take place.

When I install a new battery bank, I do two commission cycles, followed by a equalize cycle. I set the bank up for the 20 hr amp load load, and draw the bank down to 20% state of charge, then re-charge, then another 20 hr amp load down to 20% SOC followed by a recharge. Then I do a temp compensated equalize cycle. I time it based on cell needs to become equal.


I see all the time where new battery banks are injured before they are even broke in. From poor charging setups, careless owners/installers or any other reason that might lead to an early death.

Now on to condition of new batteries. I am a Trojan Dealer , and I can tell you this. Every Trojan that I install has a build date of less then 45 days old.

My Trojan distributor brings in fresh batteries weekly, and anything with a build date exceeding 60 days goes back to the manufacture, where they are sold off in auction lots.

So it's possible to buy old and dated battery from some locations, be careful where yo buy.

Lloyd

[Forever Freedom]

Originally Posted by btrayfors

I'm not sure about all chargers, but my programmable Victron MultiPlus 120/2500/120 has what they call a "repeat absorption" phase, not "pulse charging".

After a specified period of time, the charger reverts to the absorption voltage for a specified time, then reverts to the float charge voltage.

And, to further complicate things, there are two levels of "float charge". One of these is programmable and is the one the charger goes to after finishing the absorption phase. The other is reverted to if there has been no activity for a given time period, and is not adjustable in the latest software version. I believe Victron calls this the "storage" cycle and is fixed at 13.0VDC.

My Victron is set to do the "repeat absorption" cycle every other day for 30 minutes.

Bill

Bill, My apologies for being less than specific in the use of the word "pulse". . .
I was merely indicating that there are certain battery chargers which will raise the charge voltage above the Float voltage, for a set period of time and at set intervals, to combat stratification and sulphating. I was anticipating that this might encourage further research on the matter by the initial poster.

[tartansail]

Originally Posted by FlyingCloud1937

I can shed some light on the subject of commissioning a battery bank. A new battery have formed plates.

If you were to cut open a brand new battery and pull a set of plates they will be very smooth and shiny.

Now if you dissect the same battery after a 100 plus cycles you will see that there the lead is very pores and rutted, the plates will have almost twice as much surface area for the chemical reaction to take place.

When I install a new battery bank, I do two commission cycles, followed by a equalize cycle. I set the bank up for the 20 hr amp load load, and draw the bank down to 20% state of charge, then re-charge, then another 20 hr amp load down to 20% SOC followed by a recharge. Then I do a temp compensated equalize cycle. I time it based on cell needs to become equal.


I see all the time where new battery banks are injured before they are even broke in. From poor charging setups, careless owners/installers or any other reason that might lead to an early death.

Now on to condition of new batteries. I am a Trojan Dealer , and I can tell you this. Every Trojan that I install has a build date of less then 45 days old.

My Trojan distributor brings in fresh batteries weekly, and anything with a build date exceeding 60 days goes back to the manufacture, where they are sold off in auction lots.

So it's possible to buy old and dated battery from some locations, be careful where yo buy.

Lloyd

Thanks, Lloyd. That makes a lot of sense and explains what happens during break-in.

[The Garbone]

Lead acid batteries left on the shelf will discharge roughly 20% per year. Floating is a good idea to keep them charged fully but you need a good charge controller that will not cook the batteries, ideally one that compensates for ambient cell temperature as colder cells hold less than warm cells. I have seen more battery strings go into thermal runaway during a cold snap than during the heat of the summer.

A rule of thumb for lead acid is they are going to need replacement after 5 years, any time after 5 years should be considered a bonus.

[seandepagnier]

also sailing in rough weather is good for the batteries since it stirs up the electrolyte

[NewMoon]

Our 12v g31 AGM's (Deka, same as West Marine) are perfectly happy not being exercised, for 5-6 months over the winter. They are connected to a smart charger that floats them as necessary, but are unused except for the occasional brief use of cabin lights during that time.

The first pair lasted 11 years of all-summer cruising, anchoring w/o generator most of the nights.