AGM battery charging questions
- Thread starter AJO432
- Start date
What did you end up doing? I am going through the same thing right now with AGM and the NOCO 2D. I am doing some testing over a few days on 3 of them, 2 are on East Penn AGMs and one on a Costco Interstate AGM.
You don't want to float an AGM at 14.5, that will kill it in a few years.
I have a Genius 2D and quite happy with it. I can probably get some voltage details from it on the weekend.
I really like the 2D. Can you post your findings?
I will, I am writing everything down as I go. Are you using the 2D on an AGM?
No, it's on an old SLA for maintenance but I've got several AGM for testing.
Well after a week of testing here are some results:
The NOCO definitely are a slow, gradual charge. During charging I measured voltages which started at 13.5V and went as high as 14.5V on average, at one point I read 14.6 on the Infiniti battery which is the newest AGM, about a month old and an O'reilly Superstart made by East Penn. East Penn specs their AGM charging voltage between 13.8-14.8 so it's right there in the ball park. As far as float voltages I measured around 13.4 and looking at published info for East Penn I found 13.5-13.62 in one place and 13.8 in another. Float voltage does seem to drop off even further when parked for a long time.
For the Interstate AGM in the VW TDI which is around 6 months old I recorder similar charging voltages but never caught it to go over 13.4V. Information on Interstate AGMs is harder to find and probably not as specific as I know Interstate just contracts with different manufacturers so I assume their specs are more generalized. All I could find is that they say charging voltages should be under 14V which doesn't make a whole lot of since since most vehicles will charge at 14.4 at least when first started. I could never catch a float voltage higher than about 13.3 on this one.
I also tested the 6 month old Superstart AGM in my ole Jeep TJ with results similar to the Infiniti with the exception that the Jeep can sit a lot longer without being plugged in and still maintain a resting voltage between 12.6 and 12.7 while the Infiniti drops pretty fast which I concluded is from more parasitic loads than on my old Jeep.
I concluded that while the little NOCO may not be 100% optimal for AGMs, it will likely extend their useful life. The last one in the Infiniti only lasted 2.5 years, I'll see how long the (identical) replacement lasts with the NOCO.
My next chore is to install NOCO power inlets so I can plug in without raising the hoods.
The NOCO definitely are a slow, gradual charge. During charging I measured voltages which started at 13.5V and went as high as 14.5V on average, at one point I read 14.6 on the Infiniti battery which is the newest AGM, about a month old and an O'reilly Superstart made by East Penn. East Penn specs their AGM charging voltage between 13.8-14.8 so it's right there in the ball park. As far as float voltages I measured around 13.4 and looking at published info for East Penn I found 13.5-13.62 in one place and 13.8 in another. Float voltage does seem to drop off even further when parked for a long time.
For the Interstate AGM in the VW TDI which is around 6 months old I recorder similar charging voltages but never caught it to go over 13.4V. Information on Interstate AGMs is harder to find and probably not as specific as I know Interstate just contracts with different manufacturers so I assume their specs are more generalized. All I could find is that they say charging voltages should be under 14V which doesn't make a whole lot of since since most vehicles will charge at 14.4 at least when first started. I could never catch a float voltage higher than about 13.3 on this one.
I also tested the 6 month old Superstart AGM in my ole Jeep TJ with results similar to the Infiniti with the exception that the Jeep can sit a lot longer without being plugged in and still maintain a resting voltage between 12.6 and 12.7 while the Infiniti drops pretty fast which I concluded is from more parasitic loads than on my old Jeep.
I concluded that while the little NOCO may not be 100% optimal for AGMs, it will likely extend their useful life. The last one in the Infiniti only lasted 2.5 years, I'll see how long the (identical) replacement lasts with the NOCO.
My next chore is to install NOCO power inlets so I can plug in without raising the hoods.
After reading this thread: https://bobistheoilguy.com/forums/threads/battery-charger-testing-results.336207/ my testing looks pretty primitive. At least in post #128 of the linked thread @JHZR2 seems to have reached the same conclusion that I did through my bumbling second grade experimenting!
JHZR2
Staff member
Did you use the AGM setting?
I’m confused about your voltage readings. You never caught it go over 13.4? Seems odd. Often a battery will hit the CC voltage peak quick and then the chargers will pull back. That could mean that there is low capacity and it peaked up because of inability to take charge quickly.
It should hit a reasonably high voltage, certainly higher than 13.4V for a while and as the SOC increases.
Some chargers will titrate charge up sequentially after the CC stage, and so if the charge never got to where it should, the SOC could also be too low.
https://bobistheoilguy.com/forums/attachments/1640582093527-webp.82291/
That NOCO plot shows that it reverts in voltage a few times…. It’s essentially performing the CV charge cycle asymptotic current decrease in reverse by dropping the current and getting to the cv level repeatedly.
Thanks for your reply, I was hoping you'd drop in.
The NOCO-2D on board charger has no mode settings, NOCO says it works for FLA and AGM. https://no.co/genius2d I saw voltage as high as 14.5-14.6 while charging. The 13.4 I thought was float but today after reading your thread I now understand better what was happening. At any rate my intention was to see if the 2D would help with the longevity of the AGM and after reading your thread I believe it will and I will keep them. Being retired with 5 vehicles none get driven daily and all are on some sort of maintenance chargers, 3 AGMs on NOCO 2Ds, 1 H8 AGM on a Victron Blue Smart 12/5 and 2 group 65 FLAs in my diesel truck on an old Deltran on board 5 amp tender.
I appreciate all your knowledge and research which if I am correct leads me to believe I should be ok with the NOCOs
I have a 2d on an Optima Red Top. it hasn't blown up yet - how's that for some primitive testing 
Well things have been working well till yesterday when I plugged in the NOCO to the Infiniti and about an hour later the factory alarm sounded. I thought I had bumped the panic button in my pocket so I just killed the alarm and it was OK the rest of the day and all night. Then today I unplugged it so my wife could run a couple of errands totalling 4 starts but very little mileage so I plugged it in when she got home. After about an hour the alarm went off. Neither of us had the key fobs in our pockets so it wasn't an accidental press. I killed the alarm and went back to what I was doing but about an hour later it sounded again. Now I have to figure out what to do about that.
So I think it's because I left the hood cracked and the wind moved it and the alarm switch closed. I re-routed the cord temporarily so I could fully close the hood. I have a NOCO inlet but haven't yet had the time to install it so I've had to raise the hood each time to plug in the NOCO.
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