Keeping a charge on AGM batteries

[Teleman]

Keeping my previous coach connected to shore power for extended periods of time required monitoring the water levels in the lead acid batteries but my new coach has AGM batteries. Am I correct in assuming it's okay to leave it connected to shore power for several months at a time between trips and the batteries will be fine?

[Gjac]

To keep things simple if you have a single stage charger in your MH you can always just buy a 40 amp portable that has settings for wet cell, agm and gel battery. I have an old Magnatech 9050 single stage charger in my MH and use a 40 amp B&D portable to charge, equalize and desulfate. I charge my 2 6v GC batteries in Oct when I winterize and push the battery disconnect switch for the house batteries and disconnect the neg cable on the chassis battery then fully charge again in April. Just checked the voltage and they are at 80% SOC. They only lost 20% in 4 1/2 months. I don't keep them plugged in 24/7 even in the summer, just recharge when they self discharge to 80%.

[MountainAir05]

wa8yxm wrote:
In days of old some of the converters were first class JUNK and would destroy batteries if left connected too long.. I don't think that converter type has been manufactured in the last 20 years
Modern converters come in 3 or 3+ types
Single state: More proper to call this a "power supply" Fixed out put voltage normally 13.6 battery NEVER gets to full charge

Two stage... Bulk/Float This recharges much faster but depending on the unit may or may not fill the cells with power.

Three State (Bulk/Absorption/Float) Now this rapidly recharges the battery to like 90% then slowly tops it off to FULL then switches to Float. Best type

The PLUS. Equalization or desulfacation features.


And mine for my AGM or wet cell is 7 stage plus equlization or desuf.
Provided the converter has the proper "profile" You are golden. But even a Flooded Wet charger like the Progressive Dynamics Charge wizard is at worst Silver with AGM's (The profiles are mighty close)

If your rig was made this century. post the make and model of your converter for more.

[wa8yxm]

In days of old some of the converters were first class JUNK and would destroy batteries if left connected too long.. I don't think that converter type has been manufactured in the last 20 years
Modern converters come in 3 or 3+ types
Single state: More proper to call this a "power supply" Fixed out put voltage normally 13.6 battery NEVER gets to full charge

Two stage... Bulk/Float This recharges much faster but depending on the unit may or may not fill the cells with power.

Three State (Bulk/Absorption/Float) Now this rapidly recharges the battery to like 90% then slowly tops it off to FULL then switches to Float. Best type

The PLUS. Equalization or desulfacation features.

Provided the converter has the proper "profile" You are golden. But even a Flooded Wet charger like the Progressive Dynamics Charge wizard is at worst Silver with AGM's (The profiles are mighty close)

If your rig was made this century. post the make and model of your converter for more.

[Blaster_Man]

Call who ever makes the controller for the batteries and be sure it is set up for AGMs, correct number of batteries, amp hours, charge rate, etc. Once they are set correctly, you can leave the AGMs plugged in as long as you want.

[Ivylog]

Teleman wrote:

Ivylog wrote:
A 2000 Airstream likely has a dumb converter...doesn’t go into float charging. I would just disconnect them, remove the negative cables. AGMs can sit for 6 months without loosing enough voltage to hurt them unlike lead-acid.

There's a switch inside the doorway that operates a relay that disconnects the house batteries. Wouldn't that suffice?

While the relay will cut off most of the power, the relay still has power to it...not a big draw but over months it adds up. You may have a physical/manual disconnect switch closer to the batteries.

[MountainAir05]

Teleman wrote:

MountainAir05 wrote:
If they are AGM then they need a correct charger. I have one vehicle that has it and it stays on the charger 24/7 if not on the road. I use a Cteck brand. My OEM lasted 9 years doing this. As stated every time you take them off they start over, just not as long as if they not been on in a while.

https://smartercharger.com/

Are we talking about the same thing? Honest question. When plugging in to shore power the converter supplies the charging current. I'm not even sure yet where it is (2000 Airstream Land Yacht) and it's not something I can check right now, but is it likely to have different charging settings?

Yes you will not be able to use the RV system unless it came with a high end or up grade to a higher end charge. Since you have a 2000 as stated you do not have a high end charger as OEM. Maybe an upgrade. If you going to run AGM then you need to configure the correct way so they will last. Charging voltage and rest voltage are different for AGM. 12.80+ for charging. My rest voltage is 13.1

[Teleman]

Ivylog wrote:
A 2000 Airstream likely has a dumb converter...doesn’t go into float charging. I would just disconnect them, remove the negative cables. AGMs can sit for 6 months without loosing enough voltage to hurt them unlike lead-acid.

There's a switch inside the doorway that operates a relay that disconnects the house batteries. Wouldn't that suffice?

[time2roll]

Post the brand of battery or if you have the charging specs post those.
Also get out your voltmeter and check the actual voltage on these batteries direct on the terminals. Post the results.

[Ivylog]

A 2000 Airstream likely has a dumb converter...doesn’t go into float charging. I would just disconnect them, remove the negative cables. AGMs can sit for 6 months without loosing enough voltage to hurt them unlike lead-acid.

[Teleman]

MountainAir05 wrote:
If they are AGM then they need a correct charger. I have one vehicle that has it and it stays on the charger 24/7 if not on the road. I use a Cteck brand. My OEM lasted 9 years doing this. As stated every time you take them off they start over, just not as long as if they not been on in a while.

https://smartercharger.com/

Are we talking about the same thing? Honest question. When plugging in to shore power the converter supplies the charging current. I'm not even sure yet where it is (2000 Airstream Land Yacht) and it's not something I can check right now, but is it likely to have different charging settings?

[MountainAir05]

If they are AGM then they need a correct charger. I have one vehicle that has it and it stays on the charger 24/7 if not on the road. I use a Cteck brand. My OEM lasted 9 years doing this. As stated every time you take them off they start over, just not as long as if they not been on in a while.

https://smartercharger.com/

[Ed_Gee]

theoldwizard1 wrote:
IMHO I don't like to leave ANY type of battery hooked to ANY type of charger for more than a couple of days. Use a charger designed for AGM batteries but connect it to an inexpensive mechanical lamp timer and on!y let it run 4 to 8 hours per day.

Trouble with doing it that way is that everytime the charger starts up again it is likely going to start with the Bulk charge phase, which is hard on batteries when repeated unnecessarily. Leaving charger on nonstop, as long as it is staying at a proper ~13.5 Float level is best. IMHO

[theoldwizard1]

IMHO I don't like to leave ANY type of battery hooked to ANY type of charger for more than a couple of days. Use a charger designed for AGM batteries but connect it to an inexpensive mechanical lamp timer and on!y let it run 4 to 8 hours per day.

[Teleman]

jorbill2or wrote:
As long as the charger has the ability and is set to the correct AGM profile they will be fine. Did you adjust the charger or double check it’s settings ?

I bought the RV unaware it had AGM batteries. I'll take a look at the converter. Thanks.