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John Russell
Master Marine Consultant

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USA
3444 Posts

Initially Posted - 07/05/2012 : 16:26:00

Is it a good idea to occasionally completely drain a deepcycle series 24 battery? Why?

John Russell
1999 C250 SR/WK #410
Bay Village, Ohio
Sailing Lake Erie
Don't Postpone Joy!

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 07/05/2012 : 17:42:37

From marineelectronics.com:

7.5. Shallower average depth-of-discharge. (DoD), increases the battery life. For example, a battery with an average of 50% DoD will last twice as long or more as an 80% DoD; a 20% DoD battery will last five times longer than a 50% DoD. For example, golf cart batteries will average 225 cycles at 80% DoD and increase to 750 cycles at 50% DoD. Try to avoid DoD that is less than 10% or greater than 80%. Industrial traction and stationary deep cycle batteries are designed for 80% DoD and most marine an RV deep cycle batteries are designed for 50% DoD.
(This life/% discharge is from Concorde Battery, but all lead acid batteries are similar)

7.9. Never discharge below 10.5 volts.

From wind sun.com:

Lead-Acid batteries do NOT have a memory, and the rumor that they should be fully discharged to avoid this "memory" is totally false and will lead to early battery failure.

Summarized from multiple sources:

Sulfation occurs in all batteries in normal operation, and most of it is converted back in recharging. A deeper discharge causes more sulfation. About the same percentage of lead sulfate remains unconverted after recharge, but it is the same percentage of a larger amount and leads to earlier failure. Sulfation continues to increase until the battery is fully recharged. Optimum life is achieved with a daily discharge of at least 10% with immediate recharge and no discharge beyond 50%.

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 07/05/2012 : 19:17:30

Thanks, Dave. It was that "memory" thing that I was confused about. I remember hearing about that for other rechargeables. I remember when I was in the Air Force working with "bricks", aka radios about the size of a brick with rechargable batteries. They kept dying because we never depleted the batteries enough. Must have taken 6 month or more to get to the bottom of that problem. I just didn't remember if that applied to lead acid batteries.

It came up today because we had a prolonged power outage today and used a 120VAC/12VDC fan to move a little air around for a few hours until the AC came back on.

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Voyager
Master Marine Consultant

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USA
5368 Posts

Response Posted - 07/05/2012 : 19:53:48

I visited a local chapter of the TV Engineering Society meeting at Anton Bauer batteries. They make battery packs for portable TV cameras. The lead engineering sales person gave us a complete description of the varying battery technologies:
1. Lead Acid - they only use Gel technology. They have installed an automatic cutoff to prevent depletion.
2. Nickel Cadmium - still in use, as they are efficient and economical, however disposal is expensive. Suffer from memory effects.
3. Nickel Metal Hydride - very popular, do away with battery memory charging effects and can deliver a great deal of power. Charging must be done carefully, so as not to overheat the battery. Heating will shorten battery life.
4. Lithium Ion - provides a greater power vs weight (power density). FAA and Homeland Security do not allow Li-Ion batteries to be carried as check in or carry on for airline flights. Have been known to short out and cause a fire. You don't want a fire on a plane. He also mentioned that there were several varieties of Li-Ion batteries.

Anton Bauer focus on battery technology for camera and lighting uses. They also were contracted by Apple to make the batteries from MAC notebooks.

Their website is provides a great deal of info about their battery products.

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 07/06/2012 : 06:11:32

An Aside: Did you ever crack open a laptop battery? It"s just a box full of double A's with a tiny bit of distribution circuity. Talk about wasted space and disguising a product to make it proprietary and more expensive! The newer Mac laptop batteries are actual batteries shaped to the space available, one of the many reasons, including profit, that even the least expensive Macs are high end products in their class and cost more.

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Stinkpotter
Master Marine Consultant

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Djibouti
9080 Posts

Response Posted - 07/06/2012 : 12:30:13

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Voyager
 FAA and Homeland Security do not allow Li-Ion batteries to be carried as check in or carry on for airline flights.<hr height="1" noshade id="quote"></blockquote id="quote">Really? Aren't these standard on most newer laptops, tablets, and such?

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vipermagic
1st Mate

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USA
69 Posts

Response Posted - 07/07/2012 : 08:28:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stinkpotter
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Voyager
 FAA and Homeland Security do not allow Li-Ion batteries to be carried as check in or carry on for airline flights.<hr height="1" noshade id="quote"></blockquote id="quote">Really? Aren't these standard on most newer laptops, tablets, and such?
<hr height="1" noshade id="quote"></blockquote id="quote">

This rule can't exist. I carried 3 lithium batteries (two laptops, iphone) on 4 domestic flights this spring.

Not to hijack, but I'm reminded of http://xkcd.com/651/ :)

Edited by - on

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