Requesting solution from knowledgeable RV.NET collective

[RV-1_2n-FUN]

Need to replace 2yo T-105s due to my neglect and wondering if 2-12V 24DC in parallel are a wiser less expensive choice since not using MH dry-
camping?

https://www.walmart.com/ip/EverStart-Lead-Acid-Marine-RV-Battery-Group-24DC/180350522

TIA for expert opinions as always

[BFL13]

Can't help you there, Phil. I understand the question. The various AGM guides say to charge at 14.x where x depends on brand/type, and the AGM battery specs give 14.x for use when "cycling" and 13.x when in use as a UPS.

Mex once said something about needing the 14.x to force more into the glass mats ISTR, but not sure what he meant.

I suspect you are getting enough 14.x from alternator time to satisfy the requirement somewhat plus you do the right thing for fully recharging them.

[pnichols]

BFL13 wrote:

MDKMDK wrote:
Yes, they are. And you can mount them upside down if you want. Try that with your "wets". :B

Guess what happens if you forget to recharge them to 0.5a/100AH at 14.x volts until amps taper that low. (see that guide and the other brands' guides, same thing.) You need an ammeter and a charger that will hold 14.x volts for as long as needed to get that done, which many chargers/converters can't do.

Also AGMs can be mounted sideways but not upside down.

Hmm ... we've been over some of what you say above, before.

Keeping lead acid (liquid or AGM) batteries as close to fully charged as much as possible is what makes them serviceable for the longest possible time. I've seen nothing in print from the experts as to why voltages above 14 are required - if one has the time to let them fully charge up using less than 14 volts.

My 2nd set of AGM RV batteries in 14 years is doing as fine as the 1st set did (for their first 8 or 9 years) using only the stock 13.6-13.8 volt converter in the RV and the engine alternator when traveling to charge them. While in storage both sets of AGM batteries were/are continuously hooked up to the converter, since the RV is plugged in all the time during storage.

I'm still looking for my first technical paper detailing the reasons why voltages greater than 14 are required to fully charge lead acid batteries - assuming that an ammeter shows the batteries have reached the low 0.5 amp fully charged current acceptance rate at whatever charging voltage was used.

[RAS43]

RV-1/2n-FUN wrote:
Again, thanks for all replies.

Group 29DC at Walmart for $100.00 each with 2 YEAR FREE REPLACEMENT and a pair in parallel will fit.

p.s. -- not too concerned about being WET since if I roll the MH pretty sure other issue will arise.

Good choice, that is what I have and will begin the third year this spring. I have dry camped for a couple days due to a power failure and they did fine.

[Chum_lee]

IMO, if you hook up two 12 volt batteries in parallel, when new and roughly factory equivalent, they will mimic each other. As you charge/discharge them, one battery will tend to do more of the work and take more of the wear over time because of the way they are wired and their inherent internal resistance. As you discharge/recharge them, one battery will charge more than the other because it is working harder and sees more charge. (or less depending on which battery gets the higher charge voltage) That's why, in general, 2 simple 6 volt batteries wired in series (to make 12 volts) are normally used in simple applications. With more than 2 batteries wired in series/parallel, things can get more complicated.

Edit: That said, if you want the cheapest solution, just get a dirt cheap 12 volt automotive battery. If you don't boon dock and are always connected to shore power, IMO it's all you need.

Google: "The 12 volt side of life" if you want a more detailed explanation.

Chum lee

[CA_Traveler]

OP A single 12V battery will do the job based on no dry camping, about 80Ah depending upon the group. 2x the power for 2. Plus easy to remove and charge if needed. 🙂

If in the future you want more power and longer life then consider 6V deep cycle battteries. Larger, heavier and cost more. 😞

[Lwiddis]

With a battery history of neglect, I suggest you buy an AGM battery.

[BFL13]

MDKMDK wrote:

BFL13 wrote:

MDKMDK wrote:
Yes, they are. And you can mount them upside down if you want. Try that with your "wets". :B

Guess what happens if you forget to recharge them to 0.5a/100AH at 14.x volts until amps taper that low. (see that guide and the other brands' guides, same thing.) You need an ammeter and a charger that will hold 14.x volts for as long as needed to get that done, which many chargers/converters can't do.

Also AGMs can be mounted sideways but not upside down.

Lighten up a little. :C
And please, stop micromanaging other people's batteries. It helps no one.
How do you know they can't be mounted upside down? Have you ever tried it? :E

Scroll down to where it says, "Except upside down"

http://www.wegosolar.com/products.php?product=SKR%252d125AGM-Stark-AGM-12V-Solar-Battery-Sealed-125A

Also read para 3.9 here, which even says if on their sides, only the long way, not up-ended.

https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf

[MDKMDK]

RV-1/2n-FUN wrote:
Again, thanks for all replies.

Group 29DC at Walmart for $100.00 each with 2 YEAR FREE REPLACEMENT and a pair in parallel will fit.

p.s. -- not too concerned about being WET since if I roll the MH pretty sure other issue will arise.

I would think so. :W

[MDKMDK]

BFL13 wrote:

MDKMDK wrote:
Yes, they are. And you can mount them upside down if you want. Try that with your "wets". :B

Guess what happens if you forget to recharge them to 0.5a/100AH at 14.x volts until amps taper that low. (see that guide and the other brands' guides, same thing.) You need an ammeter and a charger that will hold 14.x volts for as long as needed to get that done, which many chargers/converters can't do.

Also AGMs can be mounted sideways but not upside down.

Lighten up a little. :C
And please, stop micromanaging other people's batteries. It helps no one.
How do you know they can't be mounted upside down? Have you ever tried it? :E

[RV-1_2n-FUN]

Again, thanks for all replies.

Group 29DC at Walmart for $100.00 each with 2 YEAR FREE REPLACEMENT and a pair in parallel will fit.

p.s. -- not too concerned about being WET since if I roll the MH pretty sure other issue will arise.

[BFL13]

MDKMDK wrote:
Yes, they are. And you can mount them upside down if you want. Try that with your "wets". :B

Guess what happens if you forget to recharge them to 0.5a/100AH at 14.x volts until amps taper that low. (see that guide and the other brands' guides, same thing.) You need an ammeter and a charger that will hold 14.x volts for as long as needed to get that done, which many chargers/converters can't do.

Also AGMs can be mounted sideways but not upside down.

[opnspaces]

2oldman wrote:
24dc is the group, not the voltage. I know, I'd never heard of it either.

Lol that's what the 24dc meant.:) I was assuming the OP wanted to wire in series for 24 volts.

[MDKMDK]

Yes, they are. And you can mount them upside down if you want. Try that with your "wets". :B

[BFL13]

AGMs are not set and forget anymore than Wets are. See AGM charging guide here:

https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf