Battery question

[GerthT]

Casita says deep cycle marine battery group 27. I know nothing about batteries....is a size 27 a size 27 is a size 27? I see prices ranging from $75 to $350. What should I consider/look at when buying a battery? (there was no battery in my '99 SD when I bought it...) Thanks in advance!

[MCDenny]

Size 27 is size 27. Dollar differences are due to quality, technology, marketing.

Basically the cheapest is a wet lead acid battery (like the one in your car). Some have caps that let you add water to the acid, some are "sealed for life" as they die when the acid is gone.

Next would be Gell (not too popular anymore) or AGM (Absorbed Glass Mat). These are 2 to 3 x the cost of a wet battery but can be discharged deeper without damaging the battery. The acid is a paste that doesn't boil when charging so they don't need water. They should last longer than a wet battery, even if you keep the water topped up. Concorde Lifeline is an excellent AGM brand. Optima batteries are AGM.

Other more high tech batteries like Nicad, NiMH and Lithium are all smaller, lighter and much more expensive than an old fashioned lead acid battery.

Batteries also come as "starting" batteries or "deep cycle". You want deep cycle for your trailer.

I'm putting a pair of 6v Lifeline batteries in my new Lil Snoozy.

[Darwin Maring]

Consumers rates the Costco Kirkland battery as a best buy.

[Thomas G.]

I just bought a size 27 at Walmart -106 amp hours for $68 plus $9 core charge, if you don't have a trade in.

[honda03842]

Denny,

Why you putting a pair of Lithium batteries in your trailer? I looked up the Lifeline 6V and it seems to be the same weight as a Trojan 105 and to have the same current rating.

I assumed the advantage of Lithium would be weight.

As to battery life of wet cell batteries, we had a set of Trojan 105's in our motorhome and they still worked great after 14 years when we sold it. True you do have to add water but that's easy.

[Rene]

I also seem to recall that the Costco Kirkland battery is made by the same manufacturer as the Walmart deep cycle. Both are marine deep cycle batteries for boats or RVs. They are cheaper because they are a light duty deep cycle with spongier plates that allow for starting outboard motors or RV's in milder temperatures. A group 27 deep cycle that is more expensive is more likely to have the same capacity in amp hours but heavier plates that should last longer. I have a kirkland battery group 27 deep cycle marine that is now 6 years old and still going.

[honda03842]

Denny,

Sorry, I'm getting old.... Some how I read Lifeline Lithium....

[Darwin Maring]

I also seem to recall that the Costco Kirkland battery is made by the same manufacturer as the Walmart deep cycle.

I've been told there is only a couple of battery manufactures so it boils down to the specifications the battery are made to.

Consumers Reports rate the Costco Kirkland brand as best.

[RogerDat]

I seem to recall that deep cycle plates have more clearance from the bottom, prevents shorting out from precipitate.

Good to know about that Costco rating by Consumers.

[Carol H]

Originally Posted by Darwin Maring

Consumers rates the Costco Kirkland battery as a best buy.

I purchased my last one from Costco and so far so good! Yup the price was very right as well.

Oh & take your old battery into Costco or they will charge you an extra $10? fee

[MCDenny]

Norm, I've built some electric boats and have been very happy with the Lifeline batteries, including great tech support from the manufacturer.

A 6v battery weighs 65#, has a C20 of 220 a-h and has a reserve capacity (how many minutes it can provide 25 amps) of 492 minutes. I think reserve capacity is a better measure of battery capacity than the C20 rating as it is a more real world load.

Two of these in series give a 12v bank with Rc of 492 minutes and weigh 130#. A single 125# 12v battery has an Rc of 390 minutes. Same weight, same money, 26% more energy storage. All data from Lifeline's web site.

AGM batteries have a much lower self discharge rate, can stand deeper discharges and can charge and discharge at higher rates without derating capacity (lower peukert exponent) as much as wet batteries. They don't need to be watered and don't give off gas when charging. That justifies their higher price to me.

Any battery can live a very long life if care is taken to keep it charged and not draw it down much below 50% too often.

[RogerDat]

Not giving off gas is important for those folks who decide to put the 12 volt storage inside instead of on the hitch. At least those that don't want an explosion. Have seen pictures of under couch, under sink and in closet battery & converter installs. If memory serves they were all AGM style batteries.

[Kip in Ga.]

Obviously a battery living in the same space as people should not give off gasses or fumes. So an AGM would be the better choice.

They cost more than Flooded batteries and require no maintenance.
However, according to this page from Trojan Batteries they don't have the reserve capicity of same size flooded batteries. And actually weigh a tad more.

When choosing batteries for my Electric boat, I read on Trojan's web site that flooded batteries will take more charges than AGMs. That was several years ago, and unable to find that info now.

Scan to the bottom of this page for info on flooded and AGM batteries.
http://www.trojanbattery.com/pdf/TRJ...dSpecGuide.pdf


This page specifically deals with Marine and Rv Batteries.
Again the Flooded batteries outperform AGM and Gel.

http://www.trojanbattery.com/pdf/TRJN0175_RECColl.pdf

FWIW: The battery inside our home that stays constantly charged by a solar panel, for emergency lighting, is an AGM. The ones in the boat, golf cars, and camper are flooded. May go with an AGM next time depending on cost.

I haven't read this new Trojan website thoroughly, so whether or not AGM batteries are harmed less by being deeply discharged is a mystery to me. Maybe someone can supply a source for that information.

Here is another source for comparison of the 3 types of battery. This source does say that AGM batteries are more subceptable to being ruined if the charger is not in tip top shape.
http://www.vonwentzel.net/Battery/01.Type/index.html

Hope this helps.

Kip

[john warren]

well,, batteries are another one of those things that prove,,,"you will never be sorry you bought the very best"

[Rene]

Originally Posted by john warren

well,, batteries are another one of those things that prove,,,"you will never be sorry you bought the very best"

This may be partly true but some people should probably stick with cheaper batteries. Those who use their batteries only for a few weeks a year, overdrawing them (the easiest thing to do) forgetting to add water, not promptly recharging them or using only a converter or bulk charger instead of a multistagecharger could easily kill any battery fairly quickly. Once you are sure you can really maintain your battery for long life and are going to use it for more than a few weeks per year, then consider a more expensive quality battery.

[BCDave]

Originally Posted by Rene

This may be partly true but some people should probably stick with cheaper batteries. Those who use their batteries only for a few weeks a year, overdrawing them (the easiest thing to do) forgetting to add water, not promptly recharging them or using only a converter or bulk charger instead of a multistagecharger could easily kill any battery fairly quickly. Once you are sure you can really maintain your battery for long life and are going to use it for more than a few weeks per year, then consider a more expensive quality battery.

Have you been spying on my battery maintenance habits?

Actually - even with the above-described "system of careful battery preservation" the Optima Blue top has lived over 10 years. I don't expect the flooded cell one on the other trailer to go much past 2.

[MCDenny]

Originally Posted by Kip in Ga.

Here is another source for comparison of the 3 types of battery. This source does say that AGM batteries are more subceptable to being ruined if the charger is not in tip top shape.
Battery Types: Flooded versus AGM and Gel

Hope this helps.

Kip

You cannot replenish the water in an AGM so if they are over charged enough to boil the electrolyte and cause the battery to vent the battery is ruined.

Three stage chargers are common, reliable and not too expensive. I personally don't think over charging is much of a risk.

[Donna D.]

So... the question remains. IF you are always hooked up to an electric bush when camping... do NOT boondock or have solar... do YOU need a deep cycle battery or is an el-cheapo 'car' battery (which you probably need for the brake disconnect switch) good enough? I ask, because there are a number of owners that may want to know the answer...

[MCDenny]

Your car battery is pretty much always being charged while in use, just like a trailer battery hooked to a charger always connected to an electric bush. The cheapo car battery will last just as long (5-6 yrs?) in your trailer. The fly in the argument is that is has to be connected to shore power all the time, especially when it is sitting in your back yard unused for several months. A typical car battery will self discharge itself dead in 3-4 months.

[Kip in Ga.]

According to the battery page posted above. A flooded battery will typically self discharge about 1% per day. Depending on ambient temperature.

So yes, as McDenny said, in 3-4 months a flooded battery would be pretty much discharged. That would very likely be true whether it be a deep cycle or a car battery.

On the other hand, an AGM car battery would likely behave the same as a deep cycle AGM battery and discharge much slower.

Question is, do they even make AGM car batteries? Realizing there have been maintenance free car batteries around for years. Such as the Sears "Die Hard". Are they AGM or simply flooded batteries that are somehow sealed?

A cheap-o car battery would work fine in a camper that was plugged into camp power, but would likely have a shorter life than a more expensive one. Also IF camp power went out for several hours, and a fantastic fan and light were burning, the car battery might not do well.
Construction of car batteries and Deep Cycles are different as they have different jobs.

Another thought:

The more expensive and better quality chargers have buttons or switches for selecting Flooded or Gel or AGM. According to my "Battery Minder" charger/desulfinator, the 3 types need to be charged at different rates and/or at different cut off points.

The power supply in my 2003 Casita doesn't give me those options. I don't know if it is a multi-stage charger or single stage. AGMs were not as plentiful in 2003 as they are now. So could the camper charger do justice to an AGM or even damage it?

Kip