Battery Size (replacing)

blt2ski wrote:
8D and 4D batteries aren't used in boats?;?;? USCG use 8 8D per Cutter based in Puget Sound. I know a few folks with 1 8d per motor. Reality iirc mat, two or 3 31's equal an 8d with out the weight to toss a 150'ish lb battery around.

I was speaking of pleasure boats. USCG can throw 4 - strapping young 22yr olds at the problem if they need to move an 8D.

Similarly when you get into really big yachts the rules are different...again, the guy who buys a 150ft mega yacht likely is paying someone to bring big strapping guys in to move batteries around...plus they are likely putting them in a walk in engine room, not shoe-horned into a tight spot where you have to crawl in on your belly.

Pleasure boats below 50ft...almost unheard of (at least in the last 30-40yrs) and certainly with the advent of cost competitive lithium.

But all way off topic for a guy who doesn't even boondock. A basic group 24 is plenty for that use.

8D and 4D batteries aren't used in boats?;?;? USCG use 8 8D per Cutter based in Puget Sound. I know a few folks with 1 8d per motor. Reality iirc mat, two or 3 31's equal an 8d with out the weight to toss a 150'ish lb battery around.
With this said, on brand of lead deep cycle I know of, stuffs a bit more lead into their batteries, so you get another 5-15 AHR. So their 24 is just shy of a 27, 27 shy of a 31.
AGM as noted, last a long time. I've seen some Northstar, now Odyssey branded A,gM, along with Mastervolts coming back at work 8-12 yrs old on boats. Be lucky to get 2-4 with a typical 12V lead deep cycle. Also most AGM batteries s considered dual purpose. You can star motors, or cycle them down as house batteries. I use a lead DP for my sailboat. You can drain these many more times than the typical 4-6x with a true starting battery. AGM batteries try to get charged at 40% of there list AHR, putting many charging systems in trouble, as they can not keep up with the battery taking the charge. You toast an alternator, or charger. Lead or gel need 25% or so of lost AHR to charge them up.
I used to drain two 24's overnight when winter camping in my trailer, just keeping the rig warm in 10-20f temps. 2 270 AHR 6v woul net me 24-36 hrs in those temps. I had no hook ups.
A single 24 in sailboat can last me a day or three depending upon what electronics I'm using. I have 5 years with a Northstar 31, vs 2-3 max with lead versions.
OP has a battery. There is more than one way to set up RVs and boats to suit ones needs. Lithium may be next house battery, half the weight of leaf, triple the usable AHR for a given size.

Marty

An inverter powering a residential fridge , uses around 10amps draw from battery while the fridge compressor is running, it uses far less electrical energy than an RV absorbtion fridge, which needs more electrical power for same job,
The Dometic Elite 2 door fridge in this RV uses 4x the 120v power than the residential fridge in my previous RV, that's why i stick to LP for cooling this fridge, and only use 120v as backup when LP tank is empty .

wa8yxm wrote:
of GC-2

If not LiFePO4 is expensive but may well be worth it. And getting less expensive daily.

Far cheaper than equivalent AGM, LiFeP04 is now the cheapest you can go when you take lifespan and usable AH into account. for me I just had to take usable AH into account, and they were cheaper than GC2 batteries

Steve

Veebyes wrote:
There are plenty of good reasons to go to an AGM. The double to triple the service life is only one of them. My first AGM gave me nine years.

In storage the AGM loses very little. My AGM sits, disconnected and untended, November to April and retains enough power to operate landing legs upon reconnection.

Zero maintenance other than annual terminals cleaning.

Yes they cost more. Much more. Given what they are over the 100 plus year old technology of the wet cell the AGM is worth it.

There's a reason why they are used in aviation and marine applications.

The reason they are used in marine, and aviation was they don't spill when the boat rocks or the planes bank. Also, before I retired from the Navy in 2009 we converted a lot of our stuff to Lithium batteries to improve reliability, capacity, and lifespan.

They do last longer compared to a normal starting battery but not when compared to a GC2 so let's throw out some context. The only reason to buy an AGM in an RV, in my opinion, is if you don't want to do maintenance on the batteries as they do protect themselves from low water levels better. To me it just doesn't make sense to get AGM for a RV application as here, the price is double for an equivalent battery.

Campinfan wrote:
Thank you for all the great info. I did go get a 27 battery but next time I may upgrade to an AGM.
Not sure why my post does not make sense....it is the battery in my trailer that is listed. Maybe the manufacturer just went cheap.

I am not convinced of the advantages of AGM in most cases. IN SOME cases yes. AGM is better than a "Wet" battery but those are extreme.

IF you can expand the battery compartment go with a pair of GC-2

If not LiFePO4 is expensive but may well be worth it. And getting less expensive daily.

Veebyes wrote:
There are plenty of good reasons to go to an AGM. The double to triple the service life is only one of them. My first AGM gave me nine years.

In storage the AGM loses very little. My AGM sits, disconnected and untended, November to April and retains enough power to operate landing legs upon reconnection.

Zero maintenance other than annual terminals cleaning.

Yes they cost more. Much more. Given what they are over the 100 plus year old technology of the wet cell the AGM is worth it.

There's a reason why they are used in aviation and marine applications.

Other than checking water, nothing different than standard lead acid. I've not replaced a battery on an RV. Disconnect the cables, clean the terminals and water in the fall. In the spring reconnect and away you go.

The reason they are used in aviation and marine is you can flip them on their side or completely over without spillage. Usually, that's not an issue for most RVs.

So still waiting on a reason to pay soooo much more for AGM.

valhalla360 wrote:

Campinfan wrote:
Thank you for all the great info. I did go get a 27 battery but next time I may upgrade to an AGM.
Not sure why my post does not make sense....it is the battery in my trailer that is listed. Maybe the manufacturer just went cheap.

Why would you bother paying for an AGM? The only advantage is you can flip the trailer and the liquid won't drain out...if you flip your trailer, the battery is the least of your concerns.

If you don't change your use pattern, a basic battery is going to be fine when you need one in 7-10yrs.
If you start boondocking, better to go with a couple 6v golf cart batteries as you get more amp-hr per $.

Except none of this matters. Since the little single battery on the big 5ver will either get overused and drained and cooked very easily or it is literally never used without being backed up by the converter.
There are more important considerations in this thread that are worthy of clarifying or debating than AGM or not.

RLS7201 wrote:

Grit dog wrote:

RLS7201 wrote:
Marine/RV batteries are compromise batteries. They were developed for marine trolling and engine start. They do not excel at either.
For you application a standard lead cell starting battery is your bet choice.

Richard

You’re right about the first part, sort of. They’re actually just fine for starting and will take the short term high amp loads just fine but they’re a compromise for deep cycle/ house battery use like trolling motors and campers because they have more/thinner plates to accommodate the high amp loads.
Second part you’re completely off/backwards. A dedicated starting battery while it will do the same job as a deep cycle, it won’t do it near as long before it’s worn out. That’s why true deep cycles aren’t suitable for high amp starting loads. They have thicker plates that last longer under discharge conditions that a good operating starting / charging system keeps from happening.

It is my understanding that the OP was looking for a starting battery. Which makes my comments correct.

Richard

Your understanding was wholly incorrect as the OP has a camper trailer. As listed in his first post.
But regardless, dual purpose “marine” FLA batteries make fine starting batteries, just not great deep cycles in the long run.

There are plenty of good reasons to go to an AGM. The double to triple the service life is only one of them. My first AGM gave me nine years.

In storage the AGM loses very little. My AGM sits, disconnected and untended, November to April and retains enough power to operate landing legs upon reconnection.

Zero maintenance other than annual terminals cleaning.

Yes they cost more. Much more. Given what they are over the 100 plus year old technology of the wet cell the AGM is worth it.

There's a reason why they are used in aviation and marine applications.