CCA ratings for a Group 27 Battery

[herons]

I need to replace my factory battery with another Group 27 deep cycle battery. I have choices between a 600 CCA and a 675 CCA. Does it matter when using in a small camper?

[AC0GV]

Originally Posted by herons

I need to replace my factory battery with another Group 27 deep cycle battery. I have choices between a 600 CCA and a 675 CCA. Does it matter when using in a small camper?

Cold Cranking Amps (CCA) is for starting engines. Look at the Amp hours A/H to know the capacity of the battery. If you are looking at a lead acid battery you will want to use only half of capacity to get the most years of life.

[RogerDat]

Most deep cycle batteries these days are intended to be usable in applications such as boats that require a certain amount of Cranking Amps. CCA is just a measure of how much "right now" power battery can deliver at a certain cold temperature as a means to compare between batteries and to show which battery will run the starting motor.

Amp hours is a measure of the storage capacity of a battery. Best way to understand that measurement is how long can this battery run a light that draws 1 amp. A hundred amp hour battery is able to run that 1 amp light for 100 hours, double the draw with say a 2 amp fan and battery can only supply that power for half as long. Most group 27 batteries will be fairly close to the same capacity. 110 to 125 amp hours as I recall. Group 24 is smaller so maybe 90 - 100 amp hours. The group number is physical size. So that one can purchase a battery that fits in the space.

Drawing a battery down below 50% of charge causes changes internally with the battery that greatly shorten lifespan of the battery. Flatten a battery by total discharge and the lifespan and usability can be greatly diminished.

If you want to compare how long a battery will run the lights, fans, pumps in your camper that is figured based on amp hours of the battery.

[Carl V]

If the Ah rating of the battery isn't labeled, another relevant spec to look for is the Reserve Capacity. It is the number of minutes a battery can last with a given load (usually 25 amps) before it is depleted. So the higher the number the better capacity.

[Perryb67]

A series 24 battery deep cycle battery "usually" has about 80 amp hours @ 20 hour rating

A series 27 battery about 90 amp hours

A series 31 about 110+ amp hours

For more power you can install two 6v batteries in series to create a 12 volt.

A pair of series GC2 6 volts will be about 220+ amp hours.

When we could only have one battery on the tongue, I always bought a series 31. Lately we've been able to install two 6v AGM's for 220 amp hours.

However, for lead batteries divide the total ah's by 2 to get usable amp hours that won't kill your battery. For instance, series 24 has 40 usable ah's, series 27 has 45 usable ah's, series 31 has 55 usable ah's, or two GC26 volt AGM's have 110 useable ah's. This is just a guide; different types of lead batteries can go below 50%, but that's enough at this time. Do your research.

Then there is lithium. A 120 ah Battleborn has a battery management system that stops the output at 100 usable ah's so you don't kill their $900 battery.

With our 16' Scamp and 17' Casita we got by with a series 31 battery with 110 ah or 55 useable ah's. Without the furnace running we could go a whole week on 55 ah's. With the furnace it was usually down to two nights. The furnace is the biggest ah hog in our campers.

Now that we are retired and camp for long extended times we have 2 six volt 260 ah Soneil lead crystal batteries, that, because of their chemistry, will give us 200 usable ah's, equivalent to two Battleborn lithium batteries. We also have a 170 watt solar panel on the roof and a 100 watt solar portable.

Most of my information came from Batterystuff.com. Amp hours will vary from various website/manufacturers. I used the lower of the amp hours I'm familiar with.

Enjoy,

Perry

[herons]

[QUOTE=Perryb67;807727]A series 24 battery deep cycle battery "usually" has about 80 amp hours @ 20 hour rating

A series 27 battery about 90 amp hours

A series 31 about 110+ amp hours

For more power you can install two 6v batteries in series to create a 12 volt. etc



Thank you. Very informative!

[Carl V]

My Kirkland (Costco) Group 27 deep cycle is rated at 120Ah.

[Jon in AZ]

Originally Posted by Carl V

My Kirkland (Costco) Group 27 deep cycle is rated at 120Ah.

Can you double-check that? Seems high to me. All the marine/RV hybrid batteries I've seen are more in line with Perry's figures. Costco does not list Ah on their website. Interstate site lists 88 Ah for a similar 27DC marine/RV battery.

Costco marine/RV batteries are a good value, but you can get one at many different places. Start with the largest conventional deep cycle battery that will fit in the space you have on the tongue and monitor the state of charge morning and night until you get a handle on your use.

If it's discharging faster than you recharge, you have 3 choices: (1) reduce your power use, (2) add recharging capacity (eg, solar or generator to supplement the tow vehicle charge line), and/or (3) increase battery size/capacity (larger 12V conventional, dual 6V conventional, or lithium).

[Carl V]

I don't have a link to Costco's battery's specs, but that's what's on the battery. Picture is not from me but I have this same battery.
https://www.fiberglassrv.com/forums/...1&d=1615244065

[Perryb67]

Originally Posted by Carl V

My Kirkland (Costco) Group 27 deep cycle is rated at 120Ah.

I suggest you read TheBatteryGuy.com ratings explaination. We're talking deep cycle @ 20 hour rate. Any other ratings really don't apply to our camper needs. We need to talk apples to apples.

Enjoy,

Perry

[Glenn Baglo]

These are specs on my Trojan TMX 27. You can see several specs for same battery depending on criteria.

Also note, that Kirkland is trying to be all things, cranking and deep cycle.

[Carl V]

Originally Posted by Perryb67

I suggest you read TheBatteryGuy.com ratings explaination. We're talking deep cycle @ 20 hour rate. Any other ratings really don't apply to our camper needs. We need to talk apples to apples.

Enjoy,

Perry

Thank for the suggestion but I just mentioned what the label says.
I'll let you dig out the actual specs if your so interested in apples to apples.

[Jon in AZ]

There are true deep cycle batteries- Glenn’s Trojan is one- and there are marine/RV hybrids, like Carl’s. The former typically have a little more capacity, and longer life (more discharge cycles due to thicker plates). They also cost quite a bit more, like $150-175. You can buy a hybrid from Costco for less than $100 (comparison in USD).
https://www.costco.com/interstate-27...100476408.html

Is the extra cost of a true deep cycle worth it? Depends on how much you travel, how much time you spend off-grid, how much power you use, and how diligent you are about care and maintenance. For heavy users, maybe. For occasional and moderate users, probably not. The latter are more likely to accidentally kill a battery through inattention during periods of storage, in which case the pain of premature failure is lessened with a hybrid.

For the OP, I’d say go for the Costco/Interstate hybrid (or similar). Put the money you save on the battery toward a portable solar panel, LED lights, and/or upgrading your trailer's power center to a modern multi-stage charger. Take the best care of it you can- use a meter to keep it above 50%, recharge promptly, water regularly, protect it from freezing or overcharging in storage- and you should get 4-6 years of good service, sometimes more.

[RogerDat]

For most the furnace blower is by far the biggest power draw on the battery. What is worse is absent a cut off designed to stop drawing power beyond that 50% point a furnace that is running during the night can really flatten a battery. Or leave you waking up with no power and a chilly camper.

One can as I have just stick a decent quality battery in the box and figure the two LED interior lights are unlikely to kill my battery for a lot longer than the water will last. I did add an inverter which will allow me to run some 110 volt items which could lead to drawing down the battery. I plan to add a fantastic fan which also could put a lot more draw on the battery. Vent fan isn't especially high draw but it tends to run for longer periods.

Which brings up the other way to determine battery/solar needs. Find out the draw in amps of the devices you will use that draw power from the battery. Then multiply that draw by the amount of time the device will run in a day.

Repeat that calculation for all your devices. Sum the total will tell you how many amps you will draw in a day from the battery.

lights 3 hours per day @.5 amp = 1.5 amp hours
fantastic fan 4 hours per day @2 amp = 8 amp hours.
laptop 2 hours per day @ 2 amp = 4 amp hours
TV how would I know I don't camp with a TV

Divide battery amp hours by 2 to get your 50% discharge amount. Then divide that by the number of amps you use in a day. This will tell you how long you can camp on battery absent any charging.

Sum is 13.5 amp hours a day.
Battery has 90 amp hour rating divide by 2 equals 45 amp hour capacity
45 divided by 13.5 equals 3.33 days I could run the listed load without any additional charging.

If one has 100 amp hour capacity from pair of big 6 volt true deep cycle (golf cart type) batteries one can go over 7 days with that usage and no additional charge

Charging with solar, generator, campground power, or tow vehicle will allow you to replace used portion of your stored amp hours. Deep cycle and hybrid starting/deep cycle batteries charge slower than auto starting batteries. They are designed to release power slower and thus take in a charge slower. Making them especially suited to the slow all day charging of solar. Pumping amps in at a high rate from a generator doesn't work as well for deep cycle as it would to charge your vehicle battery.

Many campers will have a converter to charge the battery when camper is plugged in to campground power. People install a line to charge the camper battery from tow vehicle through the lighting plug. I have the power line from tow vehicle alternator, a few hours driving can put a full charge back into the battery.

People often do some pretty careful calculations on power usage and solar capacity in order to insure adequate power with a good margin for rainy days with little solar output. Or they do some quick back of the envelope calculations and determine dear wife will want to go someplace civilized well before I will deplete my stored reserve. Or I'll run out of water.

Even adding back in only half of what you use each day doubles the number of days you can boondock camp off the battery. So if a 100 amp solar panel would replace your normal daily use it would provide for long term camp off grid. If you instead have a 50 amp panel you would get 2x as many days as you would from the battery without any charging.

So if battery alone last 3.33 days as shown above a solar panel that puts back in 50% of daily use (6.75 amp) would give one 6.66 days of camping which I will guess is longer than my wife wants to stay in the national forests these days by at least a day or two.

Bottom line what one puts in the battery box or uses for charging is somewhat individual. For 3 season campers that will use furnace more and be camping where longer stretches of poor solar conditions are possible might opt for a lot more storage and/or a lot more solar capacity. Or a generator

Someone that does 3 and 4 day weekends at rustic campgrounds a few hours from home might be fine with a single battery and nothing, or small solar, or a line to the trailer plug from tow vehicle alternator so they arrive fully charged and get home fully charged.

Some folks always camp with power and the battery mostly just provides lights when they go in the camper at a rest area and keeps the digital electronics powered when traveling.

Costco has often been mentioned as a good place to purchase batteries, I liked the one I purchased from Tractor Supply. I will say I clean the battery, top the fluid with distilled water, make sure to fully charge as checked with a meter once in a while and store for the winter with fluid topped, fully charged and on a battery maintainer. A practice that is the result of not doing it and having expensive battery die after a season or two, freeze or cooked dry are really a good way to get assessed a "learning tax" to replace the battery.

[matthfam]

Originally Posted by Jon in AZ

Can you double-check that? Seems high to me. All the marine/RV hybrid batteries I've seen are more in line with Perry's figures. Costco does not list Ah on their website. Interstate site lists 88 Ah for a similar 27DC marine/RV battery.

Costco marine/RV batteries are a good value, but you can get one at many different places. Start with the largest conventional deep cycle battery that will fit in the space you have on the tongue and monitor the state of charge morning and night until you get a handle on your use.

If it's discharging faster than you recharge, you have 3 choices: (1) reduce your power use, (2) add recharging capacity (eg, solar or generator to supplement the tow vehicle charge line), and/or (3) increase battery size/capacity (larger 12V conventional, dual 6V conventional, or lithium).

I also have the Kirkland batteries, and yes they are 120 Ah each. I wouldn't go less than 2 batteries using my CPAP machine as I try not to draw it down too low. I also have a 310 Watt solar panel and a top-up trickle charger for when I have electric hookup. No furnace yet. (I'm installing a diesel heater though) I have changed out my lights to LED as well. So far so good.