AGM Charging Question

[Andy Squared]

I have two Optima Blue Tops, made in '17 & '19. I can not get these to charge beyond 12.8. (they are supposed to go to 13.4, 13.6 right?) We use them overnight to run a small fan, lights, we disconnect our electronics from charging and wake up to 10.8-11.4 left in the tank.

I called Optima - they said I had to get their Special Charger to get them higher than 12.8. Does this sound right? Optima has 2 chargers $90/$200, I fail to believe that I have to get a special charger. When on shore or generator power the batteries show 13.4+, once off shore power back to 12.8

Optima suggested I connect my solar panel always to maintain them. Then implied Zamp didn't not have the ability to charge AGMs. I called Zamp to verify that they do have that on their controllers.

I generally disconnect the batteries in storage and if going more than a month I put a Zamp 40W Solar panel on them. After the last month in storage with the south facing panel in the Florida sun, still 12.8

Any advice for an electronically challenged person? I want to thank all of the regular contributors in advance - your responses have been very helpful.

[Dennis C]

I've got two AGM batteries and a Zamp charge controller. There are settings on the controller that let you select your battery type to ensure proper charging. Mine is similar to yours in that it reads more than 13.4V when connected to shore power, but it drops a bit when disconnected. That said, I've never seen numbers as low as you're seeing on the bottom end. My batteries got down to 11.4V once, but that was after 5 days of boondocking without power or a generator, only 180W of solar on the roof in a heavily shaded area.

[GOUSC]

FYI - I have 3 Zamp solar panels on my roof. 2 at 90W and 1 at 100W. I use a Victron MPPT 30 controller. It achieves 14.5-14.6V in Bulk stage / 13.6V at Absorption stage and 13.2V at Float. The stock Airstream controller would not achieve that 14.5-6V rate. It would be around 13.6-8 for the bulk charge.

[ROBERT CROSS]

IMHO...get rid of the Optima 'round cells'. They just don't have the capacity. 75ah
Our Lifelines lasted 11 Seasons and are still in service as back-up power for the basement sump pump.👍
Charge them fully and disconnect/isolate during storage. A fully charged AGM battery with no draw will have no problems during off Season storage.

BTW it's best to have the same build dates on the batts.


Bob
🇺🇸

[batman]

^^^What Mr. Cross said^^^

I can not say what your charge controller in the trailer is doing. However the Zamp solar controller should have no problem charging AGM's, if they are still good. I have used Optima blue and red tops in different vehicles and boats and for a while in the Safari. Other than capacity (amp hrs) I had no problem, until I did. Once they were past that point I could not charge them enough to use them. It was time to change up and charge up. That was 2012.

FYI, CTEK makes a highly rated battery charger for AGM's also.

Now I have 4-Lifeline, 6-VDC GPL-6CT batteries in the trailer that have been in service since 2012 still going strong. Love them...

That being said it is 2021 (almost) and If I were to change/upgrade now. I would change my system charge controller, etc. To use LiFePO4 batteries. Not cheap. But if you plan to keep and use the trailer It is a good investment, IMO.



-Dennis

[dznf0g]

Although Lifeline does not recommend a regular equalizing regiment, they do recommend an equalizing charge when the batts demonstrate your type of scenario. ie. loss of capacity or won't reach the proper charge voltage. Lifeline recommends 15.48 volts for 8 hours (they call it a conditioning charge). Definitely research Optima tech material for the proper voltage and length of time. It may or may not help, depending on the "abuse" your batteries have experienced.
Like said above, I am not a fan of Optima, for the reasons stated above.

As a point of reference, Lifeline recommends that the bulk stage be a fixed amperage, until the voltage reaches a predetermined level (set by your charger or solar controller, and some brands are programmable). Absorption stage should be 14.3V =/- 1V. Float should be 13.3 =/- 1V. Anything below the mfr spec for Absorption and float and you never get a fully saturated charge, resulting in lower capacity and shortened life over time.

If it becomes apparent that it is time for new AGMs, you probably need to examine both your converter and solar controller specs and upgrade where necessary.

[Andy Squared]

Yesterday I bought a Zamp 180W, (Brand new, never used from a full-timer that could not carry the case around. She was relieved to let it go for $500, ) The controller is different from the 45W panel and does have AGM setting. When the sun comes up the test will begin.



Bob - yes I know the batteries s/b made at the time (that was just the situation, and I am paying for it)



I know I spend more on power for my trailer than my house on a per day basis; 2 Honda 2000's, fuel container, gas, 2 solar panels, 2 batteries that suck, Surge protector, Easy start... I have stopped using the phrase "recreational" when describing the trailer.



Li Batteries are what I am trying to avoid right now (unemployed for a few months now) however when the time comes, they are the next big purchase.


Again - thanks for the inputs

[ROBERT CROSS]

^
Good call on the 180,(great price btw), we have 2 and they work great with the BB Lithiums, you should be able to get a 5-7+ amp charge in full sun.👍 I have seen as high as 18.1a with the 2 180's.


Bob
🇺🇸

[ASWinos]

No one has yet mentioned in this thread that the “full” charge state for an AGM battery is typically 12.8 volts. The Optima site also points this out.
When connected to charger, the float charge voltage will read around 13.2V.

Your batteries are charging fine but the capacity may be a bit low based on age or previous use pattern. You may also want to make sure you know what current draw you expect overnight. A battery monitor would be helpful in this regard.

[KK4YZ]

Originally Posted by ASWinos

No one has yet mentioned in this thread that the “full” charge state for an AGM battery is typically 12.8 volts. The Optima site also points this out.
When connected to charger, the float charge voltage will read around 13.2V.

Your batteries are charging fine but the capacity may be a bit low based on age or previous use pattern. You may also want to make sure you know what current draw you expect overnight. A battery monitor would be helpful in this regard.

+1 on that. AGM’s are still lead acid batteries and, I believe have the same electrical characteristics of flooded cells. Full voltage of a lead acid battery is 12.7V (approx). When connected to shore power, you’re reading the output of the charger which is 13.6V or so (or 13.2 for float as mentioned above). When you disconnect from shore power, you might see higher than 12.7 until you put an initial load on it.

In short: what you’re seeing on your voltmeter is about right. I’m surprised and disappointed the Optima folks were trying to sell you an ‘upgraded charger’ when what you’re seeing is perfectly normal.

The other issue, as mentioned earlier, is your battery capacity......

[ROBERT CROSS]

Originally Posted by ASWinos

No one has yet mentioned in this thread that the “full” charge state for an AGM battery is typically 12.8 volts. The Optima site also points this out.
When connected to charger, the float charge voltage will read around 13.2V.

Your batteries are charging fine but the capacity may be a bit low based on age or previous use pattern. You may also want to make sure you know what current draw you expect overnight. A battery monitor would be helpful in this regard.

The "capacity" starts off a bit low @ 55ah or 75ah for the Blue Top's hardly enough standby.

Bob
🇺🇸

[Robert2]

Originally Posted by dznf0g

Although Lifeline does not recommend a regular equalizing regiment, they do recommend an equalizing charge when the batts demonstrate your type of scenario. ie. loss of capacity or won't reach the proper charge voltage. Lifeline recommends 15.48 volts for 8 hours (they call it a conditioning charge). Definitely research Optima tech material for the proper voltage and length of time. It may or may not help, depending on the "abuse" your batteries have experienced.
Like said above, I am not a fan of Optima, for the reasons stated above.

As a point of reference, Lifeline recommends that the bulk stage be a fixed amperage, until the voltage reaches a predetermined level (set by your charger or solar controller, and some brands are programmable). Absorption stage should be 14.3V =/- 1V. Float should be 13.3 =/- 1V. Anything below the mfr spec for Absorption and float and you never get a fully saturated charge, resulting in lower capacity and shortened life over time.

If it becomes apparent that it is time for new AGMs, you probably need to examine both your converter and solar controller specs and upgrade where necessary.

Rich - did you upgrade your charger, and if so what one are you using? I have a 2019 30Bunk. I got 2 6V Lifelines in series, and have realized the absorption requirement you mentioned above and confirmed isn't possible with my as delivered WFCO 9800 series. I'm looking for an upgrade - and lookign at the Victron Energy Blue Smart IP22 and a Victron 500 SmartShunt. It allows my to program the muliti stage charging threshholds. We're planning a whole electrical upgrade this summer (solar, new inverter, Li batteries) but need to get by until then.

[dznf0g]

Originally Posted by Robert2

Rich - did you upgrade your charger, and if so what one are you using? I have a 2019 30Bunk. I got 2 6V Lifelines in series, and have realized the absorption requirement you mentioned above and confirmed isn't possible with my as delivered WFCO 9800 series. I'm looking for an upgrade - and lookign at the Victron Energy Blue Smart IP22 and a Victron 500 SmartShunt. It allows my to program the muliti stage charging threshholds. We're planning a whole electrical upgrade this summer (solar, new inverter, Li batteries) but need to get by until then.

As a matter of fact, I just ordered a victron bluesmart ip22 yesterday. It is only 30 amps, but I think that'll be fine for our lifestyle. If it proves insufficient I can always parallel a second one later. Their larger amperage units are only available in 24 volt models. They have been telling me for a year, that they will be introducing a 50 amp, 12v model sometime, but it is way down on the priority list.