Deep cycle batteries

[SteveC]

How do you tell if an SLA is deep cycle or not? None of the batteries at Battery Plus say they are.

Thanks,
Steve

 

[cool_hardware52]

How do you tell if an SLA is deep cycle or not? None of the batteries at Battery Plus say they are.

Thanks,
Steve

No battery benefits from being deeply discharged.

Know how SEARS makes a "DeepCycle" marine starting battery?

They start with a standard automotive DieHard, reduce the warranty period, and increase the price.

My point is try to avoid deepcycling wether or not the battery you are using claims to be a "deepcycle"



Tobin

 

[Sideband]

For longest life, only discharge to ~80%. That's true of "deep cycle" batteries as well.

Joe

 

[MrConclusion]

True deep cycle batteries are different. And Battery Plus probably isn't dishonest enough to claim that any of theirs are deep cycle, like some other battery sellers mentioned above. Most marine/RV/golf cart "deep cycle" batteries are actually semi- or hybrid-deep-cycle, and still suffer from full discharging. This isn't usually a problem, because one almost never runs a golf cart or trolling motor until the battery is 100% dead!

True Deep cycle batteries will have heavier, solid lead plates (instead of "sponge" plates) and the best manufacturers to check are Concorde and Rolls-Surrette.

 

[pipedope]

This is one of those questions that does not have one simple answer.

You did say SLA so we are talking about sealed batteries and you are limiting to lead acid chemistry.

What is the application?
How much current draw, maximum and average?
How much run time do you need?

The lead acid, sealed batteries that are best in most deep discharge tasks (as opposed to starting a car) are absorbed glass mat, AGM. These are not hurt by deep discharge nor by sitting in a state of discharge. They are most easily damaged by too high a voltage during charge.

The spiral cell batters from Optima are of this type, ... sorta. They do have different models that are made for deep cycle or for starting. Their deep cycle batteries will work just fine in a starting battery job but the starting batteries die very quickly if deep cycled.

Depending on the job you might be better off with NiMH or LiIon or LiPoly batteries. Each has advantages and disadvantages including different charge requirements and cost.

 

[SteveC]

I'm making a dive light, and just wanted to keep it simple. I'm not sure how much they will be discharged, but I would think that it would be more than a 20% drop. If there truly is a deep cycle battery that is small enough for a dive light, then I would like to use it, but I have not see any. I'll probably get a couple 12v 3 amp from E-bay or something and just see how they work.

Steve

 

[cool_hardware52]

This is one of those questions that does not have one simple answer.

You did say SLA so we are talking about sealed batteries and you are limiting to lead acid chemistry.

What is the application?
How much current draw, maximum and average?
How much run time do you need?

The lead acid, sealed batteries that are best in most deep discharge tasks (as opposed to starting a car) are absorbed glass mat, AGM. These are not hurt by deep discharge nor by sitting in a state of discharge. They are most easily damaged by too high a voltage during charge.

The spiral cell batters from Optima are of this type, ... sorta. They do have different models that are made for deep cycle or for starting. Their deep cycle batteries will work just fine in a starting battery job but the starting batteries die very quickly if deep cycled.

Depending on the job you might be better off with NiMH or LiIon or LiPoly batteries. Each has advantages and disadvantages including different charge requirements and cost.

Micheal,

I agree with your take on Lead Acid batteries.

I should point out that neither NiMh, or any of the rechargeable Lithiums are a good choice for deep cycle apps.

Given the energy density and specific energy advantages of NiMh and Lithium over SLA's it might be practical to over size the battery for the application, and that way reduce the depth of discharge. The penalty is cost.


Tobin

 

[pipedope]

The least expensive solution is to us gell cell or AGM lead acid batteries and make them big enough that you never use more than 50% of capacity before recharging. The price you pay here is size and weight.

Radio control airplane people are getting great service out of LiPoly but there are serious hazards during charging that make these not so great for our use. They are also light and might need balast in the canister to make the pack neutral.

Every choice has ups and downs and unless you are doing the whole thing as a learning excersize it is probably better to use the R&D of the light makers to get a good one and enjoy using it rather than spending lots of time building your own.

I suggest checking with alarm companies and the maintenance people at local hospitals as you can often get one year old gell cells for free. In much equipment the batteries are replaced every year even though the battery has years of life left.

Free batteries or low price ones bought locally are usually best as shipping adds up quick.