Sealed batteries, particularly the AGM (Absorbed Glass Mat) battery, is becoming increasingly popular for off-grid applications and have always been preferred in RV or trailer applications due to their safety attributes.

The AGM battery is a lead acid battery, but unlike its traditional counterpart it is sealed tight and offers a number of advantages that more and more users are recognizing.

Sealed batteries with their technology advancements are capable of good performance in many demanding applications from RV battery power to off-grid living.

The technology of sealed batteries (the AGM type is the most popular) has been improving and there are some significant benefits to consider:


Improved Cycle Life

While every charge / recharge cycle reduces the life of a battery, and while regular occurring deeper discharges will worsen the overall cycle life, substantial improvements have been made to some of the AGM sealed batteries designed for deep cycle use.

For example one of the current deep-cycle AGM battery models from Trojan Battery Company, the Trojan “SAGM 12 135” (branded as “Solar AGM”) has the following specified cycle life:

4500 cycles (12 years!) if discharged daily by 20% (80% SOC)
3250 cycles (9 years!) if discharged daily by 30% (70% SOC)
2700 cycles (7 years) if discharged daily by 35% (65% SOC)

This has improved from when I purchased my Trojan “31-AGM” batteries several years ago which had the following cycle life specifications:

2800 cycles (~7 years) if discharged daily by 20% (80% SOC)
1800 cycles (~5 years) if discharged daily by 30% (70% SOC)
1500 cycles (~4 years) if discharged daily by 35% (65% SOC)

Note: The estimates above depend on good storage conditions and proper charging.

Note: Trojan Battery Company is not an advertiser with us.

Note: I use these batteries for my solar-powered battery bank which keeps the house “powered” when the sun goes down or during very cloudy or stormy days. They are 12-volt batteries which I have configured in groups of four in series (48-volt), each group then being tied in parallel to create an adequate reserve of storage capacity.


No Maintenance

You read that right. There’s no maintenance at all for AGM sealed batteries. They are sealed and therefore require no added water like other flooded lead acid batteries. So long as you charge them properly, they’re good to go…


No Gas Release While Charging

This is a substantial attribute of AGM sealed batteries. Because they are sealed and release no dangerous gases while charging, they are safe to keep indoors, in the RV, or in your trailer as a power source. Other batteries require proper enclosure and ventilation of those gases.


No Terminal Corrosion

Because they don’t leak, they won’t contaminate or corrode battery terminals. This is particularly important in any off-grid application where good connectivity (and longevity thereof) is essential for proper system balance and performance.


Standard Ground Freight Shipping

Because they are sealed, there are no hazardous materials costs and shipping restrictions for these batteries. When I purchased my batteries, I drove to a dealer with the truck, however for some of you this may be an advantage.


Battery Mounting Any Orientation

Again, because these batteries are sealed and are filled with “all glass mat’ (rather than liquid) they can be mounted in any orientation without issue.


Better Battery Performance Indoors

Most all batteries perform poorly when exposed to temperature extremes, especially cold. This performance hit can become quite severe when we’re talking about winter temperatures. Since the AGM sealed battery is safe indoors, it’s ambient temperature is such that its performance will be in the ideal zone…

Duracell Ultra Deep-Cycle Marine

I have been experimenting with another 12-volt AGM sealed battery, the Duracell Ultra deep-cycle marine. This particular branded battery is actually made by DEKA (part of East Penn Manufacturing) here in the United States, one of the largest battery manufacturers in the world.

This battery also has an impressive set of specs., and it costs a bit less than the Trojan equivalent. We’ll see how it goes as I test it (them) out…

Note: They are not an advertiser with us, I’m just putting it out there…


Drawbacks with AGM sealed batteries

To be fair, I also want to point out the drawbacks.

1. They are lots more expensive than traditional flooded lead acid batteries. As much as double.

2. They can be damaged from overcharging, so attention must be given to charging parameters and the right charger for the job.

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