Deep Cycle batteries

wa8yxm wrote:



NOTE that Marine/Deep cycle, are far closer to starting batteries.

Not true at all. Deep Cycle is deep cycle. it doesn't matter if it has marine, RV, or both stamped on the case.
Dual purpose batteries are closer to starting batteries but with heavier plates and will be OK for intermittent light loads like cabin lights or stereos. They are not suitable for repeated deep discharges.

Uh, first the figures I saw said 50% not 80% though some claim 80% for AGM.

And Though I'm not sure of single digit discharge cycles, (Someone else suggested they are not that good an idea, I won't argue with him, I also won't agree with him, I have very simply not researched that thought well enough)

If you discharge to say 25%,,, Well you will be happy, let's just put it that way.

With nearly all batteries the deeper the discharge, the greater the damage. And the relationshiup is not linier.

That is at 25 percent you do damage, at 50 Percent you do more damage, clearly, but it is not 2x. It is greater than 2x (as in 2.y) and in the case of some starting batteries is "Many x" (how many varies brand to brand)

If you run em down 75 percent, that is perhaps 2x as bad as 50 for a deep cycle, (And many many times for a starting)

I've run my GC-2's (Deep cycle) down to .. Well I'd be embarassed to say (Lights won't) a few times over their 8.5 year life and .. Well they now need replacement... 8.5 is within the 7-10 year life expencentcy of the batteries, dead center in fact.

With starting batteries every time I've taken them that low.. NEW BATTERY TIME.

NOTE that Marine/Deep cycle, are far closer to starting batteries.

Any time you simplify and say that "best practice is" and do not qualify it, does a big disservice. I bought a Lifeline AGM battery because of a number of factors but one of them is that they do not self discharge at the same rate as a conventional wet plate led acid. I can use the master disconnect switch and leave it for the winter. The only thing left on is the Victron battery monitor so that I can check SOC and make sure it is at or very near the 100% SOC mark.
Most battery(s) can be disconnected (no parasitic loads) once they a 100% fully charged. There is no need to check water/level and a malfunctioning or poorly functioning converter poses no danger.
Knowing your batteries and what will work for them is important. Before I chose the Lifeline AGM I talked with one of their engineers and we discussed the Progressive Dynamics converter and the Morningstar solar controller. Ignorance is curable!

skipnchar wrote:
All flooded cell batteries last longest when kept at a constant state of charge. Battery life is directly proportional to the number of charge / discharge cycles

X2

I keep my inverter/converter turned on 24/7 since I'm connected to shore power whenever I'm not on the road, except obviously when boondocking. My house batteries seem to last 7 years or so before needing replacement.

So, as long as your charging system doesn't over charge your batteries, keep them plugged in and charged up.

All flooded cell batteries last longest when kept at a constant state of charge. Battery life is directly proportional to the number of charge / discharge cycles

Hi spindrift,

Cycling less than 5% may not be a good idea. There is some limited evidence for this.

Cycling to 80% IS a *bad* idea. Life of the batteries will be much shorter.

Most folks aim at no lower than 50%.

The chart below is for batteries that are intended to be used for 20 years. (and they are the best of the best, and I can't afford them)

spindrift wrote:
Since deep cycle batteries are designed to be repeatedly discharged as much as 80%, does that necessarily mean that if you don't it will decrease battery life?

No. Less deep cycling increases battery life.

Stay plugged in in storage?
Stay plugged in roast batteries?
disconnect? Oct 2013