AGM or Gel Batteries ?

[LiFeTech Energy]

Originally Posted by Randyonr3

Two weeks ago, I pulled each battery and let it settle for 48 hours and then checked it.. All of them were above 12.8..

The voltage of the battery is quite meaningless in determining the overall condition and age of the battery.
The only real way to accurately gauge the performance and age (and likelihood of failure) of a battery (for both lead acid/AGM and LiFePO4) is to perform a load test as well as measure the internal impedance of the battery and compare the measured result with the specification of a new battery.

[Paul L]

Originally Posted by LiFeTech Energy

The voltage of the battery is quite meaningless in determining the overall condition and age of the battery.
The only real way to accurately gauge the performance and age (and likelihood of failure) of a battery (for both lead acid/AGM and LiFePO4) is to perform a load test as well as measure the internal impedance of the battery and compare the measured result with the specification of a new battery.

Life,
I'm not questioning what you are saying, I'm interested in a little more detail. If you fully charge a battery, and then leave it without load for multiple hours and then read the standing voltage, doesn't this give you a reasonable measure of the batteries health? If the spec says 12.95 is max and you read 12.8, then the batt is somewhat depleted (say 10-12%), etc.

Paul L

[LiFeTech Energy]

Originally Posted by Paul L

Life,
I'm not questioning what you are saying, I'm interested in a little more detail. If you fully charge a battery, and then leave it without load for multiple hours and then read the standing voltage, doesn't this give you a reasonable measure of the batteries health? If the spec says 12.95 is max and you read 12.8, then the batt is somewhat depleted (say 10-12%), etc.

Paul L

Of course if you measure the voltage of the battery and it reads 12.8 then 99% of the time the battery will be ok but it in no way indicates the state of health of the battery.
I remember the AGM battery I had a few years ago and it read well over 12V after leaving it standing for more than 24 hours after charging. But when a tiny load was connected (even a 12V light globe) the voltage would instantly drop to 2V and the battery would completely die. The "surface voltage" reading of 12V can be very misleading and is in no way is a reliable factor in determining the condition of a battery.

The only reliable/accurate methods of testing a battery for its age and state of health are a load test and impedance test. Since the impedance (internal resistance) of a battery increases as it ages it is easy to compare this reading with the internal impedance of a new battery to determine how closely it will perform to a brand new battery.
Often LiFePO4 cells are impedance matched to make racing batteries since each cell in the pack will have virtually identical performance in terms of charging and discharging performance. Cells can be measured and the best cells used to make a battery which will provide the greatest discharge power.
Of course this is not so important for cruising boat owners but is used for racing battery applications.
For example below is a photo showing LiFePO4 cells being assembled into battery packs fitted in a custom fiberglass case. The little yellow label stuck on the cells has written on it the actual measured impedance of the cell thereby allowing the batteries to be assembled using cells with the same performance characteristics. The battery pictured is used to power the world's most powerful/fastest electric powered bicycle which is built in Europe.

[Paul L]

How is battery impedance measured?

Paul L

[LiFeTech Energy]

Originally Posted by Paul L

How is battery impedance measured?

Paul L

With a special instument called a "battery impedance test meter". These are used for testing critical power/UPS system batteries and are not a common everyday test meter which you can buy at your local Radio Shack store.
They test the battery by injecting a 1000Hz (1kHz) test signal into the battery.

If you are going to buy one it is best to avoid the cheap Chinese meters since they are not very accurate or reliable. Buy a good quality meter made by one of the reputable test equipment manufacturers. The Hioki meters (model 3554 or 3555) are an example of a very good meter made in Japan and is an example of a top quality meter I would personally recommend. These meters aren't cheap so are only economical if you test batteries professionally (or have a big wallet).
BATTERY HiTESTER 3555

[noelex 77]

I have had excellent life out of Sonnenschein gel batteries. (18 years on my first boat and 12 with lots of abuse from the PO in my current boat)
Their solar bloc and A600 batteries are ideal for deep cycle applications on a boat.
I think Lithium batteries are the way of the future, but the technology is still a little young at this stage. If your primary charging is with a generator and weight saving (say on a Cat) is important I would be tempted by lithium batteries now, but if these factors do not apply I would stay with lead acid for the moment.

[starfish62]

This page has a pretty good overview (and some earned opinions) on AGM/Gel/Flooded.

Deep Cycle Battery FAQ

[SV Demeter]

Originally Posted by Randyonr3

You're talking my language... When I installed the batteries "7 years ago" I wanted a worry free system, no gassing off, No filling batteries, and No Leakage..
A system that would run the boat, Off the grid, and not have to worry about what the wife was using while I had the inverter running..
Opperating under the wind charger and solar pannels and to take whatever I put them trru..
I bought Lifeline 4ds, service free AGMs...
We have 10 of them on the boat, and expect them to last for ANOTHER 10 to 12 YEARS..
Our 4ds have an algarythm (sp) of being fully charged at 12.8 and 50% charge at 12.2.. ours have never been below 12.6..
The reason behind the number of batteries is that we now have over 2000 amp hours of storage.. about half of that being usefull as you never discharge below 50%.. Being ours are working in the high upper end of the charge cycle, the life expected is much higher.. they have NEVER been through a full cycle..
Two weeks ago, I pulled each battery and let it settle for 48 hours and then checked it.. All of them were above 12.8..
AGMs are a higher price, but charged properly, Just might have an unlimmited lifespan.........

Your profile shows a Beneteau 42. Where do you put 10 4D's on a Beneteau 42 and how high did you have to raise your water line?

[Mark_S.]

Originally Posted by Tinkerer007

I recently installed an LiFePO4 battery and so far it is great.

Usable capacity is double the lead batteries.
Charge is more efficient.
Weight is half of lead batteries.

Two downsides are cost and a mechanism to prevent discharge. (If your charging system can do more than 16v, you would also want to prevent overcharge).

There is a comprehensive thread not to far down...

What is your experience now after 3 years?

[Tinkerer007]

I had one cell die on the way back from Hawaii.

The company I bought the battery from went out of business and I had an issue getting it replaced. Ended up with one 180 AH cell.

Even with a low voltage cut off, the battery will go dead if sitting at the dock for too many weeks.

It seems to be very important to keep them charged. I don't think I will get 10 years out of them.

It is also hard on alternators as it draws so much current. So you will need a regulation system.

Originally Posted by Mark_S.

What is your experience now after 3 years?