noco battery charger voltage spiking?

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Nov 29, 2009
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So, I never noticed this before. This battery was pretty much dead at 10.5v Let it charge a few hours. Decided to check the voltage. Well it keeps pulsing between 12.93v and 15v all within about a 5 second cycle. Both of my noco 5 genius chargers are doing this. I don't recall this before. Usually it goes up to like 13.5v and stays around that range until it's charged, then settles around 12.83v
 
if the battery was showing 10.5V, it was discharged, but not dead, or 1 cell is dead.

But the desulfation mode involves pulsing high voltages, so I'm guessing that is going on. Nothing in the Noco manual?
 
It's flashing the green light which means it seems to think it's mostly charged but when I turn it off and hook a multi meter to it, it's only at like 10.9v
 
You've got a dead/ shorted cell. The others are probably getting overcharged with 6/5 of the proper voltage; any evidence of offgassing, low water, acid on top?
Idk. It was taking a charge the first few hours and stayed at one bar blinking, then I unplugged it to see if it was holding a charge at all and it went from 10.3 to 10.9v, but then once I plugged it back in ot went all the way up to a blinking green light and it just cycles back and forth from 12.93 to 15v. So idk what happened.
 
Sounds like it is fully charged in the good cels and fully dead in the bad, and the NOCO is just cycling. NOCO is probably just fine. Battery is toast.
 
Sounds like it is fully charged in the good cels and fully dead in the bad, and the NOCO is just cycling. NOCO is probably just fine. Battery is toast.
Well it is 4 years old. I had to try. Time for a new battery. First time I've ever had a totally dead battery like that though. Usually it's a situation where it's just an extra long slow crank type of deal and you get a warning for a week or two beforehand. This one didn't even jiggle the starter solenoid
 
Well it is 4 years old. I had to try. Time for a new battery. First time I've ever had a totally dead battery like that though. Usually it's a situation where it's just an extra long slow crank type of deal and you get a warning for a week or two beforehand. This one didn't even jiggle the starter solenoid
Yeah - you did good!
 
Your batteries done for. I have a G5 and it’s doesn’t pulse in normal mode. It goes up to 13.something and then goes into float when the light is solid green. To put into repair mode, you have to hold repair mode for around 3 seconds when you 1st connect it. You can try it, but I think your looking at a new battery.
 
Your batteries done for. I have a G5 and it’s doesn’t pulse in normal mode. It goes up to 13.something and then goes into float when the light is solid green. To put into repair mode, you have to hold repair mode for around 3 seconds when you 1st connect it. You can try it, but I think your looking at a new battery.
I wonder what happened to the battery for that to happen. I've never had a battery be dead as a doornail like that with no warning. I ordered a new battery at advance last night then forgot to pick it up on the way home today 🙃
 
I wonder what happened to the battery for that to happen. I've never had a battery be dead as a doornail like that with no warning. I ordered a new battery at advance last night then forgot to pick it up on the way home today 🙃
My wife’s 07 Murano had it happen once but that battery was 6yrs old, still no warning though. This last winter, my wife and I drove her 6 month old car to Detroit airport, went to Florida for a week and came back to a battery so dead it barely unlocked the doors, stone dead, shot! AAA got us going and we went straight to the dealership where they replaced it. My conclusion is, they just don’t make things like they used to. Now I charge my cars as often as I can and check battery health once a month. Her 2024 battery was testing @95% health the week before it went to pot. Both times that it happened couldn’t have been at a worse time. I now keep a jump pack in the back of all my cars, so I’m sure I’ll never have a bad battery again now. Or the jump pack will be bad when I need it.
 
My wife’s 07 Murano had it happen once but that battery was 6yrs old, still no warning though. This last winter, my wife and I drove her 6 month old car to Detroit airport, went to Florida for a week and came back to a battery so dead it barely unlocked the doors, stone dead, shot! AAA got us going and we went straight to the dealership where they replaced it. My conclusion is, they just don’t make things like they used to. Now I charge my cars as often as I can and check battery health once a month. Her 2024 battery was testing @95% health the week before it went to pot. Both times that it happened couldn’t have been at a worse time. I now keep a jump pack in the back of all my cars, so I’m sure I’ll never have a bad battery again now. Or the jump pack will be bad when I need it.
Those dumb jump packs always have a dead battery when you need it too. Idk, I was expecting longer life out of this battery. It's not like sits in a hot engine compartment 12hrs a day baking to death.
 
Those dumb jump packs always have a dead battery when you need it too. Idk, I was expecting longer life out of this battery. It's not like sits in a hot engine compartment 12hrs a day baking to death.
The best battery is a fully charged one, I’m learning. What part of the country are you in? Having a battery discharged and sitting, cold or hot, is just as bad as having Arizona heat beating it up in the engine bay. I went a little crazy buying chargers here of late but sitting in a freezing car in a dark parking garage while waiting for AAA, my wife said not a word. I haven’t had a battery slow crank in 20 yrs. They worked one time and were gone the next. I’d hook your Noco up to the new battery every chance you get to stay ahead of sulfation. All 3 of my cars (new one included) had new batteries this last December. I’ve been diligent about charging and they’re all still 100% battery health. I’m hoping this staves off instant failure.
 
The best battery is a fully charged one, I’m learning. What part of the country are you in? Having a battery discharged and sitting, cold or hot, is just as bad as having Arizona heat beating it up in the engine bay. I went a little crazy buying chargers here of late but sitting in a freezing car in a dark parking garage while waiting for AAA, my wife said not a word. I haven’t had a battery slow crank in 20 yrs. They worked one time and were gone the next. I’d hook your Noco up to the new battery every chance you get to stay ahead of sulfation. All 3 of my cars (new one included) had new batteries this last December. I’ve been diligent about charging and they’re all still 100% battery health. I’m hoping this staves off instant failure.
You know what I should have done is get an interstate battery. Got two on my boat from 2019, still doing good. The one on my tractor is just a no name battery, so who knows who made it. Although its gotta be one of the 3 or 4 only manufacturers we have in the country. It's these junk batteries I get from the auto parts store that fail early
 
You know what I should have done is get an interstate battery. Got two on my boat from 2019, still doing good. The one on my tractor is just a no name battery, so who knows who made it. Although its gotta be one of the 3 or 4 only manufacturers we have in the country. It's these junk batteries I get from the auto parts store that fail early
I don’t buy from auto parts store, way too expensive. Back when advance let you use big discount coupons I bought one of their batteries and didn’t have an issue. I’ve been getting Deka batteries from the local farm store and have had good luck. Although it’s only been 6 months, they’re all testing at 100% so far, as they should. The Deka rep personally removes the old and restocks with new so I’m thinking that maybe they aren’t getting the bejesus beat out of them by store employees.
 
It's not just desulfation mode. All new firmware-controlled external battery chargers use some kind of pulse pattern where voltage varies.

I have a 1A manual wall-wart charger, and that thing has a 16V open circuit voltage. It has to be connected to a load before the voltage goes down. I think it might have measured about 13V.
 
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