Overvoltage! Schumacher SEM-1562A-CA Charger/Maintainer
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From: Delaware
Overvoltage! Schumacher SEM-1562A-CA Charger/Maintainer
I recently bought the 1.5A Schumacher charger/maintainer, when my Sears 2A maintainer died. I read in the HD 2017 touring owners & service manuals that a charging voltage greater than 14.6 is not recommended for AGM batteries. So I tested the Schumacher charger on three different (non-AGM) batteries before connecting it to my 2017 Road King. In all cases, the voltage rose to 15 volts before the unit switched to maintenance mode! Two of the batteries were gel cells often found in lawn tractors. The gel cells were marked "maximum charging voltage: 14.4". Whoops! I won't be doing that again! The Schumacher instructions claim the charger is safe for AGM batteries. Not on my Road King!
I also have a Harbor Freight ("HF: where the customer is quality control") 2/6 amp charger/maintainer, ITEM 60431. On the same gel cells, in the 2A mode, the maximum charging voltage was 14.4 volts.
So it looks like I'll be cutting off the alligator clips from the HF charger cable, and adding the mating connector for the Road King.
I assume that the Deltran maintainers don't exceed 14.6 volts? Has anyone measured this?
Dave
I also have a Harbor Freight ("HF: where the customer is quality control") 2/6 amp charger/maintainer, ITEM 60431. On the same gel cells, in the 2A mode, the maximum charging voltage was 14.4 volts.
So it looks like I'll be cutting off the alligator clips from the HF charger cable, and adding the mating connector for the Road King.
I assume that the Deltran maintainers don't exceed 14.6 volts? Has anyone measured this?
Dave
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Here's the Batter Tender information. Read this section and study the chart. Battery Charging Algorithm Fundamentals:
http://www.batterytender.com/Battery-Basics
http://www.batterytender.com/Battery-Basics
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Thanks for the link, Vernal. But as much as I tried, I cannot find anywhere where the Deltran charger manufacturer specifies the maximum charging voltage, either in the TECHNICAL section, or in the product documentation. The closest I can come is in a generic diagram of the four charging phases. There it shows a max charging voltage of 15 during the absorption phase, and an even higher voltage in the subsequent equalization phase.
For their 0.75A tender, the web page says it is suitable for AGM batteries, but nowhere in the product document (either in English or in French!) does it say AGM. By the way, the Tender document, and the Schumacher document, are surprisingly similar. They both even put the extension cord chart right near the beginning of the product document. How's THAT for good technical info?
So what's a concerned biker to do?? Well, for a start, we can see what the AGM battery manufacturers recommend. On the Optima AGM battery site, they specify a maximum charging voltage of 15.0. On another AGM battery manufacturer's site (whose name I forget) they said the maximum is 2.45 +/- 0.05 volts per cell. Sooooo, for a 12v battery, the absolute maximum would be 6 x (2.45 + 0.05) = 15 volts.
I wonder where the good people at the MoCo get 14.6 volts from? It's one of life's little mysteries, I guess.
Dave
For their 0.75A tender, the web page says it is suitable for AGM batteries, but nowhere in the product document (either in English or in French!) does it say AGM. By the way, the Tender document, and the Schumacher document, are surprisingly similar. They both even put the extension cord chart right near the beginning of the product document. How's THAT for good technical info?
So what's a concerned biker to do?? Well, for a start, we can see what the AGM battery manufacturers recommend. On the Optima AGM battery site, they specify a maximum charging voltage of 15.0. On another AGM battery manufacturer's site (whose name I forget) they said the maximum is 2.45 +/- 0.05 volts per cell. Sooooo, for a 12v battery, the absolute maximum would be 6 x (2.45 + 0.05) = 15 volts.
I wonder where the good people at the MoCo get 14.6 volts from? It's one of life's little mysteries, I guess.
Dave
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Good question. I've recently measured the voltages of fully charged AGM and non-AGM lead-acid batteries. The former were about 12.8v, and the latter, 12.68v.
All measurements were made with the same VOM. The AGM may have been 12.9v; I'm going from memory.
Just to be sure, I'll put a second VOM on them when I return home in a few days. I'll let you know if there is a problem.
thanks,
Dave
All measurements were made with the same VOM. The AGM may have been 12.9v; I'm going from memory.
Just to be sure, I'll put a second VOM on them when I return home in a few days. I'll let you know if there is a problem.
thanks,
Dave
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To try to answer the question raised by im,
I put a second multimeter on a battery, and compared that to the reading I'm getting with my go-to multimeter that I usually use. The "new" meter reads 12.93v, whereas the "old" meter reads 12.84. That's about a 1% difference. The "new" meter is a fresh-out-of-the box Harbor Freight $1 wonder. If it is the more accurate one, then my previous 15 volt reading should have been more like 15.1v. I've been hoping for reading closer to the MoCo's desired 14.6 max.
The battery I was just testing was on the Schumacher maintainer. The green light was pulsing, meaning it was in maintain mode. I pulled the clips off and measured the voltage at the battery terminals. 12.8 volts or 12.9 volts - both seem about right in maintain mode. It's that 15 volt maximum while charging that is still disturbing.
What would be nice would be for the owner of a different brand charger to measure and watch the voltage as the charging proceeds. It's possible to separate the two connectors on the charging cable just far enough to insert the meter probes, so you don't have to remove a seat, cover or other stuff to take a reading.
I won't be able to post for a while. Maybe in two weeks we will know more?
thanks, Dave
I put a second multimeter on a battery, and compared that to the reading I'm getting with my go-to multimeter that I usually use. The "new" meter reads 12.93v, whereas the "old" meter reads 12.84. That's about a 1% difference. The "new" meter is a fresh-out-of-the box Harbor Freight $1 wonder. If it is the more accurate one, then my previous 15 volt reading should have been more like 15.1v. I've been hoping for reading closer to the MoCo's desired 14.6 max.
The battery I was just testing was on the Schumacher maintainer. The green light was pulsing, meaning it was in maintain mode. I pulled the clips off and measured the voltage at the battery terminals. 12.8 volts or 12.9 volts - both seem about right in maintain mode. It's that 15 volt maximum while charging that is still disturbing.
What would be nice would be for the owner of a different brand charger to measure and watch the voltage as the charging proceeds. It's possible to separate the two connectors on the charging cable just far enough to insert the meter probes, so you don't have to remove a seat, cover or other stuff to take a reading.
I won't be able to post for a while. Maybe in two weeks we will know more?
thanks, Dave
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