changing from regular to agm battery?

bhowze · 12-20-2021, 01:18 PM

I am considering changing my coach batteries from the napa 7549 regular battery to the napa 9849 AGM battery and would like recommendations. My rig is a 2018 navion 24g and batteries are original. Napa says I have a pro ration still and can get about $68.00 each credit making the 7549 $83.00 each or the AGM's $117.00 each. It would seem that the small difference would be worth it to go to the AGM battery but there is the added weight of 10lbs per and maybe heat issue, we do live in texas and travel to florida and arizona mostly
my current situation initiating the change is that nothing works unless I am plugged in to shore power and batteries are around 3.6 v, zamp panel doesnt appear to be coming on so probably only getting solar charge . I will be putting a load test on a externally charged battery before i change out

Morich · 12-20-2021, 01:46 PM

Before putting in new batteries and maybe putting them at risk, I might want to first find why the current batteries are not getting a charge while plugged to shore power.
Assuming the battery disconnect is closed, I would expect to see charge voltage coming to the batteries from the ocnverter????

But some questions about when and how you are testing the low voltage may help to clear the question. Are you saying that you get the low voltage when plugged in or is that before you plug in and while you find nothing working?
If while plugged in, there would appear to be a question of the charge system but if before plugging in, it might just mean parasitic draings have drained the coach batteries and that is pretty normal.

**creativepart** · 12-20-2021, 04:15 PM

Are you saying your 12v house battery is showing 3.6v??? Really? Maybe you mean 13.6v and that is not your battery voltage but the charging voltage being applied?????

Also, I'm confused by the statement - "zamp panel doesnt appear to be coming on so probably only getting solar charge." What do you not "coming on?" There's no reading on the display? And, how could you be getting a solar charge if the display is "not coming on?"

I'm all for replacing flooded lead acid batteries with AGMs. That's a great move. But like Richard said above. You gotta figure out the other questions above. It could be just your battery, but it also could be a lot of other things.

BobC · 12-20-2021, 06:08 PM

By "coach" batteries I assumed you meant "house" battery as opposed to "chassis" or "starting" battery. However, I looked up the specs on the two Napa batteries you mentioned and both appear to be starting batteries.

Typically "coach" and "house" are synonyms as are "chassis" and "starting". Can you clarify which battery you're replacing?

Elkman · 12-24-2021, 03:06 PM

The only real world advantage with AGM over flooded lead acid is that they can be placed on their sides. If I was replacing factory batteries it would be to gain the greater usable capacity and faster charge rate of a lithium phosphate battery. In a Class A there is more room and the option of going with heavy duty true deep cycle batteries.

Your batteries can be discharged to 50% SOC without greatly shortening their life but with lithium batteries they can be discharged to 10% SOC with no problems. I went from the new lead acid batteries to lithium phosphate and the time to get them recharged dropped by 80%. I needed far less daylight and much shorter generator run times to recharge the house batteries.

MadMaxWinny · 12-26-2021, 05:01 PM

Well, I'm a huge AGM fan. Should you go that route, you will find them pretty bulletproof (literally). I've ran them in my boats, cars, cabin and now RV for decades. If your charger has an AGM option, you'll want to change that, but if not, no worries. I've done zero modifications on my cars with no ill effects (the charge algorithms between flooded and AGM are pretty close).

BobbyH · 12-27-2021, 10:34 AM

Quote:

Originally Posted by bhowze

I am considering changing my coach batteries from the napa 7549 regular battery to the napa 9849 AGM battery and would like recommendations. My rig is a 2018 navion 24g and batteries are original. Napa says I have a pro ration still and can get about $68.00 each credit making the 7549 $83.00 each or the AGM's $117.00 each. It would seem that the small difference would be worth it to go to the AGM battery but there is the added weight of 10lbs per and maybe heat issue, we do live in texas and travel to florida and arizona mostly
my current situation initiating the change is that nothing works unless I am plugged in to shore power and batteries are around 3.6 v, zamp panel doesnt appear to be coming on so probably only getting solar charge . I will be putting a load test on a externally charged battery before i change out

DO IT............you won't be sorry,love mine

dkoldman · 12-27-2021, 06:55 PM

Make sure your system is working properly before doing anything as others have suggested.

I spent a lot of time researching batteries; but never thought about trying to get credit by having my new OEM batteries pro rated. But even had NAPA giving me $150, I still would have bought the Pure AGM Deep Cycles this past April.

I basically chunked gave away two brand new NAPA OEM FLA 65ah each that in my opinion were absolutely worthless, in favor of two brand new vMax tanks 125 ah each. Someone may be able to successfully quibble about FLA & AGM being the same technology, but it is simply NOT true performance / capability argument. Night and Day difference. The $500 I spent was by far the best mod I have made dollar for dollar.

I went from barely getting through one night of 65ah to going two full days on 125 ah. I no longer have to water batteries which I hated more than anything, I no longer have that sulfating and corrosion that was eating up my brand new RV. Why in the world would Winnebago put two dual purpose batteries in a house application is way beyond my comprehension? I no longer have automotive posts; so it is less likely for me to error to short something out when installing. A true Deep cycle AGM has enough cycles to be rated for 8 years. But here is my favorite, yes both batteries have 50% SOC, but with my AGMs I never get that low anyway!!! In fact, I have my AGS set to auto start at 12.5 which is about 60% SOC, I have capacity to go down to 12.4vdc to be 50% SOC.

Lithium is for really high volume usage and comes with a really high price tag as well. You should by what you need or simply what you want. If IU wanted to run my entire RV of batteries or if I wanted to spend weeks and weeks with no generator or shore power, Lithium would be my choice, but I only needed more amp hour capacity and I did NOT want FLA nor to spend an awful lot of money. I got it. It was one of the best things I have done to my RV. I will NEVER ever buy another FLA battery.

I had the below batteries in perfectly good working condition listed on ebay for two months and no one bothered to inquire let alone pick up.

Note: IMO these batteries would have been perfect in my boat or to start an auto if I needed that; but didn't. I am only talking about batterie needed for House Application in a RV.

MadMaxWinny · 12-27-2021, 08:13 PM

I had my own editorial column in Sail Magazine for 11 years. AGM batteries were designed for MILSPEC applications. They were found in submarines, helicopters, and tanks. They were designed to withstand a 45 round without significant degradation, as well as a 5 meter drop onto concrete. When they hit the public market, I asked the (only) manufacturer for data for a battery comparison. They told me to ask the military. I suppose you can imagine how that worked out. I subsequently published, saying I could not recommend AGMs for lack of data. They then sent me a pallet load of them for testing. This was in the 90's. Most of them are still in service. I think other battery technologies have promise, but I still believe that AGMs are the best bet for the money.

dkoldman · 12-28-2021, 09:59 AM

Quote:

Originally Posted by MadMaxWinny

I had my own editorial column in Sail Magazine for 11 years. AGM batteries were designed for MILSPEC applications. They were found in submarines, helicopters, and tanks. They were designed to withstand a 45 round without significant degradation, as well as a 5 meter drop onto concrete. When they hit the public market, I asked the (only) manufacturer for data for a battery comparison. They told me to ask the military. I suppose you can imagine how that worked out. I subsequently published, saying I could not recommend AGMs for lack of data. They then sent me a pallet load of them for testing. This was in the 90's. Most of them are still in service. I think other battery technologies have promise, but I still believe that AGMs are the best bet for the money.

Good story, I am too lazy to sail, but I have witnessed a many of people that were stranded on the lake that wish they had sails

As you state; the vMax tanks are military grade. Thus far no 45 round, c4, or nukes have done any damage to them

I have often made the below analogy.

Chevy Tahoe - FLA
Cadillac Escalade - Pure Deep Cycle AGM
Ford - F-350 - Lithium

Depending on what you need, what you want and how much money you wish to spend all can be a good fit for the intended purposes. The best way to know which battery is best; starts with what do you NEED the battery do and for how long.

BobbyH · 12-28-2021, 10:28 AM

Hello....I also went with the VMAX route converting to 4 6V's.So far so good,they work great and the price is palatable.

MadMaxWinny · 12-28-2021, 10:42 AM

When the AGMs first went public (and before the manufacturer decided to provide test samples) the only large scale sales of them were to a high-end cruising sailboat manufacturer in Florida. So I connected with their forum and presented a survey on AGMs. To my surprise, the curve was bi-nodal. Half of the people loved them and half would never buy another after experiencing infant mortality.

It took me about a month to get to the bottom of the story, but there IS one sure way to kill an AGM. Since they were "new," and since the yard used two different low-voltage install crews, one crew saw that they were a sealed battery and gray like a gel cell, so they set the voltage regulators to that setting. Gel cells have a relatively high float voltage which kills AGMs. Instantly explained why half of the installs were failing. Mystery solved!