f355spider
$50 Site Donor 2026
Just seems a time consuming rotation. I like the idea of the battery charging bank from Pro Logix if the desulfation is effective. Then no rotation, you can plug them in a leave them without monitoring or anything.
Battery Charger Testing Results
- Thread starter JHZR2
- Start date
According to the NOCO Genius 1 website, it does do battery desulfacation, but I can not personally verify that it does.
https://no.co/genius1
This is the OEM battery from my old '11 Tahoe. Changed it out in '18 due to age, not performance.
I still use it to power LED lights in a pop up camper. It been on a old BatteryMinder 12117? since it came out of the Tahoe.
I still use it to power LED lights in a pop up camper. It been on a old BatteryMinder 12117? since it came out of the Tahoe.
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- Jan 12, 2025
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The >4 year old AGM battery from my Prius has always behaved as if it had much less capacity than the testers show. For instance, when attached to a charger it took much less time than expected to fully charge given the starting SOC.
Recently I bought a DLT150 electronic load to allow a more traditional capacity test. Removed battery from car. Charged with the BatteryMinder 1500 until it had been in float for a while and let sit 12 hours over night, not connected. Then it was tested with the Harbor Freight 58759 "Viking" digital battery tester with settings: AGM Flat plate, 45 Ah, not in car. Results: V 12.79V, SOC 100%, SOH 76%, mOhms 9.06, Ah 41. Not fantastic, but still most of the capacity, although the resistance is a little high. This was a PASS, by the way. Ran a few very brief (seconds) runs with different settings to figure out the DLT150, then set up a long run at 2.5 Ah. That is a load a little more than C/20. The battery voltage after resting 20 minutes was 12.76V. Set a lower voltage limit of 12.0V and started it. The voltage drop took a somewhat complex path, with a rapid drop of .4V, which started to flatten out at 12.33V at 1 minute and then really flattened out and held near 12.08V from 40 minutes to 80 minutes, then it fell .01V every 10 minutes until the run was stopped at 12.03V at 121 minutes.
I will try to post the data and plot it at some point. (The DLT150 showed a steady current of 2.5A except for the first 10s or so.) The battery was then allowed to sit with no load for one hour, during which VOC rose to 12.35V. The temperature range measured at the battery during all of this varied between 20C and 25C, going up with time due to heating from the run and the sun heating up the garage. So to estimate capacity:
start: 12.76V implies SOC=96%
end: 12.35V implies SOC=46.9%
measured capacity 5.03 Ah (shown on the DTL150, expected from current X time).
Gives estimated capacity as (100/49.1)*5.03 = 10.25 Ah
This battery has also been on a tester at Autozone which gave values close to that for the Viking tester.
So, why would the electronic testers be off by a factor of 4 from the capacity measured with a load at C/20 (ish)????
(The DTL150 did not come with any documentation whatsoever. I found a manual somewhere on line and extracted what I thought were the salient points. Attaching them here in case anybody else ever needs this information.)
Recently I bought a DLT150 electronic load to allow a more traditional capacity test. Removed battery from car. Charged with the BatteryMinder 1500 until it had been in float for a while and let sit 12 hours over night, not connected. Then it was tested with the Harbor Freight 58759 "Viking" digital battery tester with settings: AGM Flat plate, 45 Ah, not in car. Results: V 12.79V, SOC 100%, SOH 76%, mOhms 9.06, Ah 41. Not fantastic, but still most of the capacity, although the resistance is a little high. This was a PASS, by the way. Ran a few very brief (seconds) runs with different settings to figure out the DLT150, then set up a long run at 2.5 Ah. That is a load a little more than C/20. The battery voltage after resting 20 minutes was 12.76V. Set a lower voltage limit of 12.0V and started it. The voltage drop took a somewhat complex path, with a rapid drop of .4V, which started to flatten out at 12.33V at 1 minute and then really flattened out and held near 12.08V from 40 minutes to 80 minutes, then it fell .01V every 10 minutes until the run was stopped at 12.03V at 121 minutes.
I will try to post the data and plot it at some point. (The DLT150 showed a steady current of 2.5A except for the first 10s or so.) The battery was then allowed to sit with no load for one hour, during which VOC rose to 12.35V. The temperature range measured at the battery during all of this varied between 20C and 25C, going up with time due to heating from the run and the sun heating up the garage. So to estimate capacity:
start: 12.76V implies SOC=96%
end: 12.35V implies SOC=46.9%
measured capacity 5.03 Ah (shown on the DTL150, expected from current X time).
Gives estimated capacity as (100/49.1)*5.03 = 10.25 Ah
This battery has also been on a tester at Autozone which gave values close to that for the Viking tester.
So, why would the electronic testers be off by a factor of 4 from the capacity measured with a load at C/20 (ish)????
(The DTL150 did not come with any documentation whatsoever. I found a manual somewhere on line and extracted what I thought were the salient points. Attaching them here in case anybody else ever needs this information.)
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Finally got around to plotting the data from the discharge test. Note that there are a couple of places where the voltage actually goes up slightly during the discharge, which I suspect is due to temperature - a combination of heating inside the battery from the discharge itself and from the outside as the garage warmed up from the sun. The temperature shown was measured right in the center of the top of the battery with an IR thermometer. The discharge ends at 121 minutes and the two data points after that are the battery relaxing back to its (new) VOC. Note both the instant loss of about .44V over 30 seconds when the load is first applied, and then the loss of another .25V over about 40 minutes, then the much more shallow discharge curve that follows. I looked at a bunch of discharge curves online and didn't find one with a similar shape.
This battery had previously been charged for a total of 172 hours with the BatteryMinder 1500. The HarborFreight tester didn't indicate any significant improvement. Which is not surprising in retrospect because whatever is wrong with this battery seems to be invisible to the frequency based testers. The day after this discharge test, and after the battery had been fully charged, the HF tester showed:
SOH 83%, SOC 100%, Ah 43, Volt 12.79, mOhm 8.66, at 23.6 C in the flat plate AGM mode with reference 45 Ah
so only off by about a factor of 4 from the capacity in the discharge test.
The battery also has a CCA rating of 320, not that it is ever used in "cranking" application. Tested for that the HF tester saw:
SOH 100%, SOC 100%, CCA 346, mOhm 8.66, at 23.6 C in the CCA mode with reference 320
Since it was out of the car took it to Autozone and they tested it, CCA mode (all they had), and it was very similar to the HF CCA result.
This battery had previously been charged for a total of 172 hours with the BatteryMinder 1500. The HarborFreight tester didn't indicate any significant improvement. Which is not surprising in retrospect because whatever is wrong with this battery seems to be invisible to the frequency based testers. The day after this discharge test, and after the battery had been fully charged, the HF tester showed:
SOH 83%, SOC 100%, Ah 43, Volt 12.79, mOhm 8.66, at 23.6 C in the flat plate AGM mode with reference 45 Ah
so only off by about a factor of 4 from the capacity in the discharge test.
The battery also has a CCA rating of 320, not that it is ever used in "cranking" application. Tested for that the HF tester saw:
SOH 100%, SOC 100%, CCA 346, mOhm 8.66, at 23.6 C in the CCA mode with reference 320
Since it was out of the car took it to Autozone and they tested it, CCA mode (all they had), and it was very similar to the HF CCA result.
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Correction, in this post:
DLT150 should have been DTL150. The attachment had it right in the file name though.
DLT150 should have been DTL150. The attachment had it right in the file name though.
JHZR2, Impressive testing.
I recently bought a Schumacher SC1299 which is a low cost 0.8A maintainer.
I use this on a car with a deep cycle battery that I dont drive often. I have a volt meter/USB in one of my power plugs in the car so I can always see batt voltage (was not driving car at all). I immediately noticed that the battery voltage was going down to 12.6V (which is about 25% discharge for deep cycle) and then would charge back up to 13V. This cycle repeated indefinitely taking about 2 days to discharge to 12.6V (I measure 30ma parasitic on my car including the USB adapter).
So I removed the battery from my car to test in isolation. I dont have logging capability but have 2 DMM's so I rigged up one for current and one for voltage. What I see is that attaching the charger to fully charged battery (12.9V), the charger actually draws 10ma from the battery. So the battery voltage slowly sinks to 12.6V over several days at which time the charger starts a charge cycle. It never "floats" the battery.
So I e-mailed Schumacher on this and they said this is normal operation. I also e-mailed NOCO asking about Genius 1 (Genius 1 says it supports deep cycle) and they described same operation - when battery reaches 12.6V they start a charge cycle but do not float the battery at 13V. They implied this may overcharge battery.
Odyssey clearly states that you can float their batteries at 13.2V indefinitely (float up to 13.6V but lower value preferred for long term). I believe Optima is the same. Having a deep cycle discharge repeatedly to 12.6V will reduce the life. Perhaps not by much as Odyssey says 1000 cycles at 25% discharge but this is under ideal conditions with Odyssey charger.
It appears these low cost chargers never float the battery. Interestingly my Foxsur 25A charger does seem to float the battery at 13.4V.
I sent an e-mail to Optima to ask if their D200/D400 chargers float the battery but have not heard back yet. I suspect they do. These chargers although higher price seem to be a good value as many more features and cable options and its weatherproof. The odyssey charger does not seem to be a good value IMO based on features.
Have you tested any of these low power battery maintainers (did not look at all of your posts)?
I recently bought a Schumacher SC1299 which is a low cost 0.8A maintainer.
I use this on a car with a deep cycle battery that I dont drive often. I have a volt meter/USB in one of my power plugs in the car so I can always see batt voltage (was not driving car at all). I immediately noticed that the battery voltage was going down to 12.6V (which is about 25% discharge for deep cycle) and then would charge back up to 13V. This cycle repeated indefinitely taking about 2 days to discharge to 12.6V (I measure 30ma parasitic on my car including the USB adapter).
So I removed the battery from my car to test in isolation. I dont have logging capability but have 2 DMM's so I rigged up one for current and one for voltage. What I see is that attaching the charger to fully charged battery (12.9V), the charger actually draws 10ma from the battery. So the battery voltage slowly sinks to 12.6V over several days at which time the charger starts a charge cycle. It never "floats" the battery.
So I e-mailed Schumacher on this and they said this is normal operation. I also e-mailed NOCO asking about Genius 1 (Genius 1 says it supports deep cycle) and they described same operation - when battery reaches 12.6V they start a charge cycle but do not float the battery at 13V. They implied this may overcharge battery.
Odyssey clearly states that you can float their batteries at 13.2V indefinitely (float up to 13.6V but lower value preferred for long term). I believe Optima is the same. Having a deep cycle discharge repeatedly to 12.6V will reduce the life. Perhaps not by much as Odyssey says 1000 cycles at 25% discharge but this is under ideal conditions with Odyssey charger.
It appears these low cost chargers never float the battery. Interestingly my Foxsur 25A charger does seem to float the battery at 13.4V.
I sent an e-mail to Optima to ask if their D200/D400 chargers float the battery but have not heard back yet. I suspect they do. These chargers although higher price seem to be a good value as many more features and cable options and its weatherproof. The odyssey charger does not seem to be a good value IMO based on features.
Have you tested any of these low power battery maintainers (did not look at all of your posts)?
f355spider
$50 Site Donor 2026
Every battery tender uses a different charging algorithm. There does not seem to be universal agreement on how battery tenders operate.
There are inexpensive wall wart chargers that float...you just need to research to find one that meets your needs.
The Northern Tools battery tender made by Battery Minder floats, and has temperature compensation. But its starting float at 77F is around 13.3vt with very little temperature compensation seen in my experience. Their more expensive units float around 13.4vt (even though their literature says its higher) and compensate appropriately as stated in their IFU (going higher in colder temps and lower in warmer temps)
Battery Minder makes versions that are Odyssey approved, I own three of them. They are more expensive, ranging from $105 to $185 online depending on whether the 2012AGM or more versatile 128CEC2.
Many battery tenders use an "exercise" function as you noted with the Schumacher. I have seen this on some ProLogix models.
BTW, from my research, drawing a battery down to 12.6vt repeatedly via a charging sequence is not harmful to the longevity of the battery.
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I like the tenders that put out a low amperage with a constant voltage. I have a couple of older Harbor Freight maintainers, one that outputs 13.5V and another that's 13.6V. I know that if I put these on a fully charged SLA battery and walk away for a year, they won't boil the battery dry and the battery won't have been cycled up and down like with a lot of fancier chargers.
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Well, that statement is true if the temperature where the car/battery are during this operation is moderate, like 25C. See for instance the tables for AGM and Gel batteries here:
https://www.everexceed.com/blog/why...such-a-dramatic-effect-on-vrla-batteries-_b78
At moderate temperatures 13.5V is great, it can stay there forever. The problem is that if the car is sitting at 36C-38C or higher that voltage is too high for float and if it is below 10C-16C it will not keep the battery charged. So while the charger may not be cycling its voltage up and down, the daily and seasonal temperature variations are essentially doing the same thing. This is why BatteryMinder has temperature compensation, which in theory should extend the "set it and forget it range". Their temperature compensation is not very aggressive though, so maybe with that it is OK up to 38C or down to 10C. But only if the temperature probe is actually near the battery. Which it won't be if the charger is attached at a jump point under the hood for a car with the battery elsewhere (like an older Prius, where it is under the hatch floor). All that said, if I had to pick a single voltage for float, it would be as you observed, 13.5V or 13.6V.
Temperature issues exist when charging, and there the temperature compensation is really critical, since the charger has a lot more potential for damaging the battery. 14.5V is fine at 25C, but one really wouldn't want to leave an AGM battery at that voltage on a 45C day. It does get that hot where I live, so it isn't just a theoretical issue.
Fantastic thread!
My boat has two Optima Marine batteries D27M.
We purchased an on-board charger - NOCO Gen2x5 - at their recommendation (for size). Currently have both batteries plugged in while they are in the (50° heated) garage.
This is a new generation charger, they claim. Brag sheet says “YEAR-ROUND CHARGING. ZERO OVERCHARGE. AUTO MEMORY.” Normally we’d only turn on the charger every few weeks. They won’t be reinstalled back in the boat until late April.
Is that advisable?
https://no.co/gen5x2
My boat has two Optima Marine batteries D27M.
We purchased an on-board charger - NOCO Gen2x5 - at their recommendation (for size). Currently have both batteries plugged in while they are in the (50° heated) garage.
This is a new generation charger, they claim. Brag sheet says “YEAR-ROUND CHARGING. ZERO OVERCHARGE. AUTO MEMORY.” Normally we’d only turn on the charger every few weeks. They won’t be reinstalled back in the boat until late April.
Is that advisable?
https://no.co/gen5x2
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Leave them on the maintainer full time, that's the purpose of a maintainer. I've got an Odyssey in my HD, it's 14 yrs old now, cranked fine all last summer. Always on a BatterMinder temp compensated desulificating 1.5A when parked and see's below zero temps in winter storage. Same with a sled battery that is the factory one in a '13 sled. My '19 boat battery is also on the program.
Battery tester says they are still healthy.
Battery tester says they are still healthy.
Rember, batteries degrade faster if kept in hot areas.
Ideally you want them kept cold and on some kind of maintainer.
Ideally you want them kept cold and on some kind of maintainer.
f355spider
$50 Site Donor 2026
The entire point of a quality battery tender is you leave it connected continuously. You should have no problem.
Note that NOCO is not on the Odyssey recommended charger list. But most chargers with an AGM setting should be fine.
https://www.odysseybattery.com/charger-comparison-tool/
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Yeah, we live in a temperature climate where it's almost never below freezing or above 30C so temp regulation is not so critical here for float charging.
These are Optimas. Optima does not specifically recommend chargers other than their own.
This is a new model NOCO so didn’t expect to see it mentioned anywhere.
The latest battery charger we purchased is an AntiGravity charger, which has a readout. Probably should have got the 4amp model.
https://antigravitybatteries.com/products/super-chargers/sc-10/
f355spider
$50 Site Donor 2026
Sorry my mistake...was mixing your post with alexh1 above you.
f355spider
$50 Site Donor 2026
Sure, I have used a simple 1.5 amp on board Schumacher battery tender on an Group 34R Odyssey battery...it worked too, but is less than ideal. Lot's of stuff works, but is not following the manufacturer recommendations.
Lo, Odyssey chargers look to be Ctek.
I guess using a genuine Ctek should be avoided since they're not on the list.
https://www.odysseybattery.com/charger-comparison-tool/
https://www.ctek.com/charging-solutions/battery-chargers
I guess using a genuine Ctek should be avoided since they're not on the list.
https://www.odysseybattery.com/charger-comparison-tool/
https://www.ctek.com/charging-solutions/battery-chargers
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