N_Jay

Has anyone used an ODB plug-in memory retention device when changing the main and gell-cell battery?

Just wondering if the ODB port is a good/better way to keep power going to the computer devices.

I am guessing that will all the circuits that cut off the regular power outlets, those are not a reliable way.

ddruker

When I replaced my batteries, I attached a battery keeper to the jump starting terminals on the passenger side of the engine compartment... No drama. If you do this, do be careful with the positive battery lead when you are replacing the battery, as it will be "hot" and it can short to the body or any other ground, defeating the purpose of trying to keep the system powered whilst you are changing the batteries.

N_Jay

That was my other choice.
However I was going to use a small gellcell with a limiting resistor, because I don't like using a charger as a supply without a battery to smooth the voltage.

Some smart changers and tenders will even shut off if they don't detect a battery.

I just saw the ODB memory keeper and thought it was a unique solution.

ddruker

Understand. If you are worried about instantaneous over-voltage by hooking a 12V power supply to your truck, then you could also attach any random 12V battery to the charging terminals. I just don't see a reason to spend money on a new gizmo for this procedure - you are a sophisticated wrencher and I know you have a bunch of reliable 12V DC sources you can choose from...

N_Jay

Yep, probably overthinking this.

Started having slow cranks if I let it sit a week, and since the car sits often for two+ weeks, and almost didn't start the last time it went two weeks without the tender, I figure it is time for a new battery.
The current battery has just over 6 years and 70k miles on it.
I am fairly sure they did not replace the gellcell when they did that battery, so I am going to do both.

ddruker

I replaced mine after 5 years. I had a harder time wrestling with the auxiliary battery than the main - it is in contained in annoying thin metal enclosure with sharp edges.

For the main battery, I ended up going with the Bosch Platinum Group 49/H8/L5 AGM. I liked that it has a 4 year warranty. Got it at Pep Boys on sale - price out the door was $190.

I bought a relatively cheap auxiliary battery on-line from Interstate batteries. 12V 1.3AH AGM - Part #SLA105. Total $22 including shipping. Any AGM in that same physical size group should do.

To finish out the discusssion on the ODBII memory retainer - in my mind the electrical system of the truck is just wires that eventually all connect together. So you've got some sort of power source - either a 12V battery or a 12V power supply, that's getting connected to some very small gauge wires in your ODBII port, and those wires are eventually connecting to your main 12V power bus. How is that any better than just connecting a 12V Battery or Power Supply directly to the main power bus - I would argue it's worse because if you cause a short I would rather over-current is not traveling through very small gauge wiring in my ODBII port. I get why someone would build that product - in newer vehicles the cigarette lighters may be switched so the easiest way to get power to the system from inside the truck is through the ODBII port - I just think it's unneccessary and less than optimal for someone that knows what goes where under the hood.

N_Jay

Except the electrical systems are cars are not that simple since about 1998 on. (depending on the make and model)

There may be some amount of circuitry between the common battery hot and the various "+12V" lines in the car.
Example being, even our "non-switched" power outlets are in fact switched by a SAM, so they can be shut off when the battery is too low.
I am not sure which power runs to the OBD ports, but it s likely to be "filtered" side of any car that tries to isolate computer power from the noise starting, charging and large motor running side.
My concerns was if people knew that for some MB-Crazy reason, our cars did not like seeing power flowing in the ODB port.
I am not too worried about shorts, as the unit is powered by a 9V battery, and they will not light up much of anything.

ddruker

Agree. Good luck with your project!

Next up for me is another round of transmission and gearbox fluid changes, new engine air filters and and a new fuel/water separator.

N_Jay

When I have to get into the manifold, EGR, or maybe even the next air-filter change, I am thinking about adding a truck style vent oil separator and small diesel trunk fuel filter with a water separator.
The spin off cartridge will make things easier, and keeping the oil mist out of the intake will keep the whole intake system cleaner.

My goal is for the GL to be a forever vehicle.

DennisG01

I've only replaced my main battery, so far. Lost a few memory things, but no big deal. Didn't take much more than a few minutes to get them back. A couple of the windows (and the sun roof) didn't close/open via the one-touch... but it only takes 20 seconds to reset those.

If it was me and I was worried about losing more things with removing the little battery? Remove main battery, wrap a cloth around the positive lead and tape in place, connect the battery to the jump post under the hood with jumper cables, remove auz battery. Reverse procedure. I'm all in for buying tools - but sometimes it's easiest to just make do with what you already have lying around.

"Forever car"... I never quite got around to pulling the trigger to buying/installing this on my old '98 diesel Suburban, but check out the FS2500 Bypass Oil Filter system.

eric_in_sd

Going off topic, but: I don't see the need for a permanently installed bypass oil filter system. Hear me out:
You can get 1 micron spun polyester filters for very cheap. You can also get polypropylene housings (that's what you have on the RO filter under your kitchen sink) for cheap, too. See where I'm going with this? Pump oil up out the dipstick, through the filter, then back in the oil fill hole. Leave it running for an hour or so in your garage. Do this every few thousand miles.
I set it up but haven't tried it yet; I'm going to have Blackstone test the oil before and after polishing to see if my wacko scheme works.

eric_in_sd

Get a AA-size 8-cell battery pack. Hook the resulting 12V to the terminals under the hood. You should be good to go. Put in a 5A fuse if you're worried.

N_Jay

Going to use a 12V gel cell with a lightbulb as a resistor.
Incandescent bulbs have very low resistance below the current needed to light them.
A 12v 55w bulb effectively limits current to around 4A while providing very little voltage drop under when under an amp is drawn.
Due to a very slow start a few days ago, my wifes E350 is getting the new battery first.
Found one at Advanced Auto Parts for $195 less 25%

KYBRIGGS82

N_Jay

Just did it myself today.
PepBoys had the best price at $195 less 25%.
They wanted $45 to change it, since it is marked in their system as a difficult job. Regular battery change is free.
I would rather do it myself, so I know it is done right (the way I want) (and I am cheap).

I used a jump box to supply power to the underhold terminals.
I made a little duck tape bag to go over the "+" terminal after I disconnect the battery just as an extra measure of safety, since it was getting power from the jump box.

What I found:
1) The last guy who changed the battery, (previous owner just before I bought the GL) (maybe MB, since it was an MB battery), cut the carpet wrong and made the job harder than it needed to be (Why I like to do things myself)
2) Getting the back up battery out without removing the main battery is a bit harder, but not impossible.
3) Every video is WRONG about how to remove the back-up battery,
- The tab they want you to bend down is actually designed to be a spring to hold the battery.
- You do NOT bend the tab. You remove a 10mm nut from the metal clamp, and it swings up and slides off the battery.
4) The MB back-up battery is unique for no reason.
- It is a 12V 1.2 AH Gel-Cell battery, however the terminal are two different sizes. The Positive is a 1/4" (F2 Type) and the Negative is a 3/16" (F1 type). Probably done to keep stupid mechanics from making a stupid mistake. (See carpet cut note above)
- - This is not a problem as the standard battery of that size is F1 terminals and the wires will fit fine.
- - Any QUALITY 12V-1.2AH Gel-Cell battery will work. These are also sold as 12V-1.3AH and 12V-1.4AH, but check the size. The MB battery is slightly larger the standard, but the spring clips holding it make up any difference.
- They are also reversed the Positive and Negative terminals from normal.
- - This is also no problem since the wires are long enough to reach either way.
5) If the carpet is cut properly, you can probably change the back-up battery without disconnecting the main battery.
- I don't know if this would retain memory or not. It is not clear exactly what the back-up battery runs.
6) The main battery comes out and goes in much easier than most videos show.
- Just sit in on the rear seat and you have all the leverage you need to pull the battery out without the help of any tools, like prybars and such shown.

I would guess if I was not being extra carful, the carpet was cut right, and I was doing this a second time, it would take me less than an hour.

P.S. The battery lasted 7 years. The previous battery was 5 years old when replaced, but the guy did it early being it was his wife's car.
The back-up battery seems good, which is surprising for a 12 year old gel-cell. It might have been replaced 7 years ago, but the stamp on top of the battery is "0107 7".
Guessing that is Jan of 07, which is about right for a car built in mid 07 for 08 model year.

eric_in_sd

Great write-up.

The longevity of the back-up battery is no surprise. Lead-acid batteries last basically forever if they are not discharged and are kept cool.

lkchris

Back up battery runs the shifter solenoid.

Miguk_Saram

Accessing the battery compartment is much easier if you remove/tilt the passenger seat (4 bolts/screws; 1 on each corner. Remove plastic trim for access.) and lift the carpet. The battery would then pull straight up by the handles without issue. Be careful not to disconnect the wires attached to the seat, especially the SRS (safety restraint system / seat belt) cable unless you have and OBD scanner capable of resetting SRS.

With the seat removed/tilted, the job should not take more than 30 minutes, including seat removal.

N_Jay

I can't imagine pulling straight up would save the amount of time to remove the seat.