I have a new "memory saver" that attaches a 12V power source (e.g. Spare battery) to the car's OBDII port during a battery change to save radio presets, PCM "learning" and the like.
This seemed like a "no-brainer" and a smart thing to do but I see conflicting advice on, you guessed it, the Internet: some sources say it's prudent and almost essential but other say it's dangerous.
What's been the exprience here? Thanks.
Battery change memory savers
- Thread starter Danh
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depends on the vehicle and you have to be careful. ODB ports are only spec'd for 4 amps officially, but it depends on what fuse they're running off. Interior lights, auto lamps/DRL, fancy radio head units and the like can draw quite a bit of power
You have to plug it in and keep the doors closed to ensure the vehicle won't draw too much power. If you accidentally open the door with the battery disconnected, there's a small chance you could blow a fuse and have to go hunting for it.
Typically, when I have the time or it's important to not lose settings like security codes, I will use a small 12V SLA battery with test leads to battery lugs or fuse panel under the hood.
With proper precautions taken, they're very convenient to have around and if it has a 2 pin sae connector, it can be used with a bunch of different battery maintainers and low amperage chargers.
Some of the Noco chargers have a 12V 3-5A maintain/supply mode that works well for this.
The conventional device uses 9V battery hooked through the lighter socket.
A 9V battery doesn't need a fuse. It's so weak it can't put out enough current for a dome lamp, let alone blow the typical 15 amp fuse for the lighter socket.
You don't see these devices much any more. Most settings are stored in non-volatile memory, and a 9V battery isn't powerful enough to run the ECUs in not-quite-asleep mode.
I wouldn't use a smart charger, or a really dumb one. A smart charger will shut off when it doesn't detect a battery, and typically produces high frequency noise on the output that may not properly power ECUs. A dumb charger may output a high voltage with no load, and may be essentially unfiltered 60 Hz pulses.
Originally Posted By: HorseThief
depends on the vehicle and you have to be careful. ODB ports are only spec'd for 4 amps officially, but it depends on what fuse they're running off. Interior lights, auto lamps/DRL, fancy radio head units and the like can draw quite a bit of power
You have to plug it in and keep the doors closed to ensure the vehicle won't draw too much power. If you accidentally open the door with the battery disconnected, there's a small chance you could blow a fuse and have to go hunting for it.
Typically, when I have the time or it's important to not lose settings like security codes, I will use a small 12V SLA battery with test leads to battery lugs or fuse panel under the hood.
With proper precautions taken, they're very convenient to have around and if it has a 2 pin sae connector, it can be used with a bunch of different battery maintainers and low amperage chargers.
Some of the Noco chargers have a 12V 3-5A maintain/supply mode that works well for this.
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I just use my little jump starter at the battery cable terminals. Switched out 3 vehicle batteries recently, no issues.
I change a lot of batteries on a lot of cars at work (auto parts store) and we never bother with the stupid obd2 memory saver gizmo that corporate tells us to use... never any problems. most cars, especially newer toyotas, stall right away the first time it gets started after a battery replacement since it hasn't learned idle but on the second start it's all good.
I have a jump n carry that has a 12v out cigarette lighter style plug, and my outlet in my car stays hot all the time so I just hook them together and it even has enough power to run the power locks and lights without blowing a fuse.
I saw they make a new product that plugs into obd and that's its only function.
https://www.cloreautomotive.com/sku.php?id=554
For memory saving, I use a small lithium-ion jump starter plugged into the DC socket, with a modified cable, EC5 connector and a fused plug.
Then I'd turn on the ignition to connect up the circuit, before replacing battery.
I tried to connect at the battery terminal, but sometimes, the clip would slipped off or get knocked off by my changing of the battery.
The DC socket way is more reliable, but have to watch out for high current drain from devices, such as hazard lights, and DRL lights that won't go off.
I have used the 9 volt in the cigarette lighter for decades and have 0 issues. It's fused and it has a diode.
Just be sure to use it in a port that isn't wired to shut-off with the key.
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odd that the car maker does not cover this in the owners manual
I just write down my radio stations etc and it takes me about 2 minutes to re-install. No mess-no foul and good to go. Ed
+1 on the jump starter
Originally Posted By: Eddie
I just write down my radio stations etc and it takes me about 2 minutes to re-install. No mess-no foul and good to go. Ed
Originally Posted By: vwmaniaman
+1 on the jump starter
Originally Posted By: edwardh1
odd that the car maker does not cover this in the owners manual
Originally Posted By: Danh
Originally Posted By: HorseThief
depends on the vehicle and you have to be careful. ODB ports are only spec'd for 4 amps officially, but it depends on what fuse they're running off. Interior lights, auto lamps/DRL, fancy radio head units and the like can draw quite a bit of power
You have to plug it in and keep the doors closed to ensure the vehicle won't draw too much power. If you accidentally open the door with the battery disconnected, there's a small chance you could blow a fuse and have to go hunting for it.
Typically, when I have the time or it's important to not lose settings like security codes, I will use a small 12V SLA battery with test leads to battery lugs or fuse panel under the hood.
With proper precautions taken, they're very convenient to have around and if it has a 2 pin sae connector, it can be used with a bunch of different battery maintainers and low amperage chargers.
Some of the Noco chargers have a 12V 3-5A maintain/supply mode that works well for this.
Also, to be clear - I don't use a car battery. I use a 5 amp-hour sealed lead acid battery. They're about the volume of a softball, but square. Commonly used for trailer brakes, burglar/fire alarm panel backups, deer feeders, garage door motor backups, etc.
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Originally Posted By: edwardh1
odd that the car maker does not cover this in the owners manual
Originally Posted By: HorseThief
Also, to be clear - I don't use a car battery. I use a 5 amp-hour sealed lead acid battery. They're about the volume of a softball, but square. Commonly used for trailer brakes, burglar/fire alarm panel backups, deer feeders, garage door motor backups, etc.
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