I would have thought the same thing. Have you tried it?
12V battery charger question for the experts
- Thread starter someotherguy
- Start date
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someotherguy
Truly Awesome
I think RichLo covered why this doesn't work. And yeah, that was the preface of my whole adventure here. If you leave these lights plugged into the cord constantly as the manufacturer suggests, it kills the battery very quickly. A new or near-new battery that would previously last almost the entire work week now will no longer last a whole night on a "full" charge. Permanently damaged capacity. That's what is behind my whole series of "new battery for the tow lights" posts recently - I had to change mine after about a year because I forgot to unplug it, and it's something that happens to my co-workers frequently, as well. So I replaced a whole whack of batteries for several of them.
Richard
What about using a small 12V AGM motorcycle battery?
someotherguy
Truly Awesome
For replacing the existing sealed lead-acid battery? It's pretty small and has to fit into a tight housing. The size they chose is about the largest that will fit and it's close. I believe the "group" designation is a UB1213 (12V, 1.3Ah) and they're certainly available in AGM but that still leaves me searching for a proper charging solution.
Richard
Hmm,well it was a thought.
I just remembered that I used a battery like that to operate a remote bell on a Chelsea ships clock. I used a little float charger I found on ebay. Been a few years back so I don't remember what brand but I do remember it didn't cost much and it is still maintaining that same battery.
someotherguy
Truly Awesome
Thanks, the biggest issue I seem to have to overcome is finding a "smart" charger that won't kill the battery, but is also 12VDC->12VDC because it lives in my truck, not anywhere convenient to plug into a 120VAC outlet.
Yes I could do the inverter + smart charger combo but it seems "extra" ... it might be the ultimate solution, I'm just hoping for something simpler.
Richard
This brand allows a battery to be continuously plugged in, I have this brand and it doesn’t damage batteries. Not sure if you could adapt it for your situation. My former Tacoma had a 120 outlet that while I drove I could charge ATV batteries.
www.impactbattery.com
My truck battery has been plugged into one for months, if battery discharges a bit, it senses it and brings it back to full.
“Maintenance Phase Where the battery can stay indefinitely connected to the charger. As the battery drops voltage while unused, the unit will activate when needed to ensure a full state of readiness.”
MotoBatt Little Boy 1.0 Ah Motorcycle Battery Charger and Maintainer MBCLB
6 Volt or 12 volt "Self-Sensing" 9 Step Fully Automatic Charger. Includes alligator clamp + eyelet leads. Accepting orders; will send new MBRC1 replacement charger for MBCLB
www.impactbattery.com
“Maintenance Phase Where the battery can stay indefinitely connected to the charger. As the battery drops voltage while unused, the unit will activate when needed to ensure a full state of readiness.”
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skylark
I'm Awesome
I would like to think that part of the may be that it is just killing the battery due to overcharging when the engine is running. I'd try a simple resistor to limit the voltage to just slightly over the specs of the battery.
1990Z71Swede
I'm Awesome
The Idea is not bad, its simple and might work. But I think a diode in series might work even better. The resistor will only drop the voltage as long as there is current flow to that small battery. As SOC increases current decreases, so in the end the voltage drop will be very small and possibly enough to still cook the battery. A diode will give a constant voltage drop of .6-.7 Volts regardless of current (within reason), which could be on the high side but on the other hand, backfeed of any significant current into the car will not be possible. A stack of Zener diodes in parallell with the Battery clamping the voltage to ~13.6V will most likely work, but may need a current limiting resistor, and now we are slowly moving away from simple solutions....
someotherguy
Truly Awesome
Hmm... usual scenario: that 10-12 hrs they spend on the charge cord, only the first 35-45 mins of it is with the engine running, then I get home and it sits on the charge cord all day with the engine off. When we move vehicles around to grab the 300 and go to dinner, I unplug the charge cord as they should be fully charged and ready to go for the next work week. I can do this every week for a year+ and never seemingly hurt the battery.
What seems to kill it is forgetting to unplug it at the end of the day and leaving it on the cord past that 10-12 hrs, truck not running (I generally drive the 300 on my 'off' days/nights) just sitting in the driveway.
Richard
