An observation on batteries

[pianotuna]

Hi,

I'm blessed to have three banks of batteries. They are all the same size (marine 12 volt) but not all the same age.

Bank one is the chassis and is nearly 4 years old
Bank two is three in the OEM battery tray purchased at the same time as Bank one
Bank three is four in a reinforced compartment behind the OEM tray. This bank is eight years old.

Banks two and three are charged from the alternator by heavy duty relays, which can be manually switched. (They also can be charged by the solar system and converter). Bank one has recently had a trik-l-start unit added for maintenance between trips.

As an experiment I chose to run the water heater after a day of rain. I was driving at city speeds, and up to 70 amps were being transferred to the "house" circuits.

The observation was that the chassis battery sent a good deal of that 70 amps and actually discharged from about 12.9 down to 12.4 volts.

I will try at some time in the future to do a more "disciplined" back yard experiment on what is really happening to the chassis battery.

At some point in time I'll be replacing all eight batteries. I'm torn between Marine trolling and biting the bullet and going AGM. I'll be staying with 12 volt jars, so as to have no "mix" of battery types.

[Almot]

pianotuna wrote:
Hi,

I wonder about low cycle life for AGM. Sounds like battery abuse to me.

500 cycles @50% for Deka - low. 1000 cycles @50% for Lifeline - low? Quite a range...

Abuse? Definitely. Charging it from running engines - you know how good this can be. True, there are generators on yachts and cabin cruisers, but then, there is still an question of low SOC before they start charging. I suspect that onboard fuel capacity is also a limiting factor. Shore charging from 120V at berth in marina - don't know how often, if you sail a lot then you obviously can't charge it in marina a lot. Solar is not much of a help either, they don't have enough roof for substantial solar.

pianotuna wrote:
The salt water marine folks would prefer sealed batteries. Sulfuric acid + salt water = Chlorine gas = makes you very dead very quickly.

I would think so too. Though know a lot of - well, let's say, fair weather sailors - who use flooded batts, but this I can understand, given water conditions.

[time2roll]

How about get a water heater with engine assist. I think the coolant runs through the water heater. Just unloads the radiator.

[mena661]

westend wrote:
I would bet that AGM vs flooded in a blue water environment is all about the tolerance for continual abuse.

In which AGM does not do well. They have to be properly cared for in order for them to do well. I bet the military takes proper care of them or they just buy more of them. I wouldn't compare them to Joe Average Sailor/RVer.

[westend]

I would bet that AGM vs flooded in a blue water environment is all about the tolerance for continual abuse. Remember, the boat doesn't plug in at the pedestal unless at the dock and charging with the main engines or generator uses fuel, also not abundant off shore, and extremely expensive at the dock. That leaves solar and you have to have the correct gear and capacities to get it right.

Heck, if AGM wasn't fairly durable, the military wouldn't use them. They are putting AGM in all of the new vehicles.

[mena661]

pianotuna wrote:
Hi,

I wonder about low cycle life for AGM. Sounds like battery abuse to me.

I would agree especially given that blog on the sailors that were having problems with Lifeline batteries BUT others reported better battery life when switching to flooded. Don't know what's going on honestly.

pianotuna wrote:
Hi,

The salt water marine folks would prefer sealed batteries. Sulfuric acid + salt water = Chlorine gas = makes you very dead very quickly.

Not what I read. People are using T105's, L16's in boats. Seriously.

http://www.cruisersforum.com/forums/f14/trojan-t-105-6v-batteries-98311.html

[HiTech]

Here are the Deka MK series AGM curves. You can take the batteries to 100% discharge 200 times. For 50%, if you discharge daily, there are not enough cycles at 500. Obviously the cycles are much better at shallower discharge.

Cycles

Jim

[pianotuna]

Hi,

I wonder about low cycle life for AGM. Sounds like battery abuse to me.

[pianotuna]

Hi,

The salt water marine folks would prefer sealed batteries. Sulfuric acid + salt water = Chlorine gas = makes you very dead very quickly.

[HiTech]

Absolutely for really heavy cycling it's critical to look at the cycles vs. depth of discharge curves for each battery.

Jim

[mena661]

Almot wrote:
You lost me with that "marine or AGM". "Marine" are usually AGM - either deep cycle or hybrid. I wouldn't imagine anybody using flooded batts in marine environment.

The marine crowd uses flooded primarily with some going to lithium ion (mostly the sailing crowd). There are AGM marine users but it seems they're umm not popular due to low cycle life. There's not much good said about them at least not on marine forums. I was surprised too as they would be the perfect customers but that's what I read.

[pianotuna]

Hi Almot,

My existing batteries are what are now called Marine Hybrid and are flooded batteries. What I may end up with are AGM or Marine trolling (with the MT being flooded batteries).

[wa8yxm]

Almot wrote:
You lost me with that "marine or AGM". "Marine" are usually AGM - either deep cycle or hybrid. I wouldn't imagine anybody using flooded batts in marine environment.

Battery Termnology

Starting or Automotive = Battery rated in cold cranking amps (ZERO F)

Marine = Starting battery only rated down to freezing.

The above batteries should be kept near full, the are designed to provide a lot of amps, very fast, but only for a max of 30 seconds, They do not survive a deep discharge (50%) well.

Marine/Deep Cycle = worst of both types
Can provide a lot of amps, like all starting batteries, but may survive one or two deep cycles, I;'d worry though.

DEEP CYCLE, not so many cranking amps but designed to survive routine discharge to 50%.

NOTE that the term AGM has yet to be mentioned.

All of the above battery classes can be made in all the following types.

Flooded wet cells, you remove the cap and add Distilled water from time to time.

Maintenance free: No removable cap, this is a Valve Regulated Sealed Lead Acid battery with a liquid electrolytic.

AGM This is a special type of Maintenance free (See above) with the liquid absorbed into a fiberglass cloth between the plates.

Optims Optima is a sprial wound AGM instead of flat plates, there are only two plates and they sprial.

And lastly, And I serously recommend you AVOID these batteries: GEL.

This is a sealed lead acid where the electrolytic is jellied (Hence the GEL like Gelatin) They are very fussy eaters and easily damaged.


So when you talke about switching from Marine/Trolling (May be Marine Deep Cycle or ... Well if he means "Trolling" those generally are deep cycle) to AGM.. You are talking about switching from apples to potatoes.

[HiTech]

I'm a little puzzled by the chassis battery getting pulled down to 12.4v? Hmm I am guessing the bank being charged was pretty low? Ah you said after rain so low solar that day. Ok makes sense. Also I wonder did the chassis battery being in such a high state of charge tell the alternator not to go to full output initially?

One thing I would look at is cycle life for your normal use across types. You cycle a lot.

I've had good results form marine/hybrid designs for high amp loads. If you want to get even more complicated, I think they make true deep cycle AGMs that have both the thick plates of true deep cycle, but the low resistance and high amp capability of AGMs.

Jim

[Almot]

You lost me with that "marine or AGM". "Marine" are usually AGM - either deep cycle or hybrid. I wouldn't imagine anybody using flooded batts in marine environment.