Replacing Wet Cell Batteries with AGM - One or All?

[gaylemarlowe]

One of my coach batteries' "lead acid type" is getting weak. I would like to go to all AGM, eventually. Can the two type batteries be used together? In other words, can I replace just one of the wet batteries with one AGM now and replace the rest as they get weak?

[Icefixr66]

<p>In a word, NO, they charge at different rates and a lead acid setting on a charger will not bring the agm  battery up to full charge, therefore shortening it's life right from the get-go. Bite the bullet and replace with ALL Agms, if that is the route you choose. I have 10 of them <img class="bbc_emoticon" src="http://community.fmca.com/public/style_emoticons/default/sad.png" title=":(" />. It only hurts for a little while.</p>

[CarlAda]

Additionally, it's not generally a good idea to replace only one battery in a bank of batteries. Best to do the entire bank, and all of the same type.

[wolfe10]

Two "contradictory points":

ALWAYS best to replace all batteries in a bank at the same time, as one dead cell in an older battery can cause over-charging of the good battery.

The charging algorithms for AGM and wet cell are VERY similar. Not so with gel.

[gaylemarlowe]

Okay, even though it is gonna hurt as icefixer66 says, I guess it is something I will have to do. Besides, I will like the fact that there will be no more fumes in the compartment making a mess.

Thanks for the info, guys.

[jlandon13399]

Brett,

Are you saying one could have lead acid 12-volt starting batteries, and AGM 6-volt house batteries or visa versa in the same coach? My 12-volt starting batteries are fairly new, but the house batteries may need replacing in a year or so.

[wolfe10]

Jack,

A purist may say no, but the reality is that the ideal charge curve is close enough between wet cell and AGM that they will "play well together".

It is a common set up.

[jlandon13399]

Thanks Brett. I now have a plan to move forward with.

[desertdeals69]

I would use AGM for the house if had a choice.

[deenad]

The Magna we just purchased has 4 - 8D AGM's and four 1000 CCA sealed no maintenance batteries. The charger can only have one setting so, as I understand it, they co-exist just fine although they are the OEM batteries and are 2009 era and might need replacing soon as they seem to be weak, but, until we get it back from Cummins I really don't know.

[arubakid]

On the question about having a lead/acid battery for the engine and AGMs as coach batteries, there is no problem. The engine battery is charged by the engine alternator, and the coach batteries are charged by the shore-powered converter or solar cells.

[chboone]

If you use Lifeline AGM's make sure the float voltage is set at 13.2 V. Any higher can damage the batteries. Their battery manual has excellent information in it for maintaining their batteries. The manual can be downloaded from their web site, to large to upload here.

[luckydog1949]

Couldn't delete the duplicate post. Moderator help? if you get the time.

[luckydog1949]

How does the addition of a product like Amp-L-Start affect this? The Amp-L-Start monitors the charge state of your chassis batteries while plugged in to power and, when the charger begins charging the house batteries, "siphons" a charge over to the chassis batteries to keep them up.

I would think that the chassis and house batteries would then have to either be all the same, or ones that "play well together" (AGM and wet cell.)

[rlbarkleyii]

I just replaced my coach batteries with new Duracell Low Maintenance Commercial Deep Cycles group 31, three of them. Bought them from Sam's Club at a price of $114.00 each. I originally sought to buy AGM's but at $260.00+- elsewhere. I decided to try Sam's Club. BTW they sell Group 31 Deep Cycle AGM's for $199.00 which is not a bad price, but I would have had to wait for them special order. Sam's club has a decent "no muss, no fuss" warranty of one year on the Duracell's.

For the first time with this coach I am able to run the heater all night and still have 12.3 volts in the AM. What a improvement.

[CarlAda]

I'm in need of a new chassis battery - size 8D ... thinking about the Cat battery. Specs look good. Anyone ever use them or have any recommendations for a good starter battery (8D) for Cat C9?

[blueflame]

I would like to echo luckydog1949's concern.

My coach has the chassis and house batteries interconnected by a "smart" switch (I don't have the make/model handy). When the chassis batteries near full charge power is fed to the house batteries to charge them. Conversely when the house batteries near full charge power is fed to the chassis batteries to charge them.

From the information above I believe this means I can leave the flooded batteries on the chassis (they are good) and replace the house batteries with AGM (current flooded batteries are bad) and the two sets will coexist peacefully (charge off either power source). Is this assumption correct? Are there any other concerns? Or other things I need to be aware of or consider?

[glsmith47]

CarlAda

Recently replaced Gp 31 batteries (Cat C7). Did a lot of shopping (Sam's, Costco, battery specialty houses) and went with Cat batteries - best specs, warranty, and price. This was a few months ago. My local Cat dealer was discounting the Cat batteries at the time.

[wolfe10]

From the information above I believe this means I can leave the flooded batteries on the chassis (they are good) and replace the house batteries with AGM (current flooded batteries are bad) and the two sets will coexist peacefully (charge off either power source). Is this assumption correct?

You should have no issues-- this is a very common setup with AGM house and wet cell starting batteries. Since your smart inverter charger charges the house batteries, which will now be AGM's, I would set the inverter/charger to AGM, correct total amp-hrs and warm temperatures.

[gbrinck]

Just to be clear, nobody said the AGMs would be 6v batteries.12v AM deep cycles are readily available - I have 4 Trojan Group 31 AGMs for my house bank.

In a previous coach I did as Brett described - added a 12v AGM in parallel with a pair of 6v GC2 flooded cells. Ran it 5 years that way and both the flooded cells and the AGM stayed happy (charger was a 90A, 3-stage, Iota). In fact, I kept the AGM when I sold the coach and used it another year or so in my bass boat.

[dddlin]

How long should batteries last? Our batteries (four deep 6 and two 12V) are only four years old but don't hold a charge for very long. We have a 1998 Dutchstar.

[wolfe10]

When replacing batteries always replace all batteries on a bank with the same (new) kind/technology. OR, that one old battery having one cell go bad can cause your converter or inverter charger to overcharge all the batteries in an attempt to turn that now 10 VDC battery (one dead cell on 12 VDC battery) to 13.2+ VDC.

No average life for batteries-- depends on initial quality, how deeply and how often they are discharged, if they are equalized, water level kept up, etc.

[dickandlois]

dddlin,

How long should batteries last? Our batteries (four deep 6 and two 12V) are only four years old but don't hold a charge for very long. We have a 1998 Dutchstar.

There are a number of variables. Some batteries are just built better and quality is often related to price.

Then there is the maintenance of the batteries, how often one checks the water levels in the cells and the condition of all the connections at the batteries and the charger.

How often do you check or have the specific gravity of the cells tested. This test is very helpful in finding individual cells that are bad.

Do you use a trickle charger to keep the batteries charger when setting for extended periods?

Rich.

The condition of the ground connections that are connected to the chassis, engine and alternator are key points