2000 Honda Civic EX D16Y8 How to maintain current to ECU during dead battery?

Hello Fellow Forum members,

1. 3 1/2 year old battery died, ECU wiped.
2. Replaced battery, battery drained and died again, ECU wiped again, must have a parasitic drain, don't know how to diagnose that yet, trying to keep rolling til I solve the      problem.
3. Got warranty swap on battery (yes!), installed battery disconnect on negative terminal, I  remove it each time car parked to maintain battery.
4. Must get car inspected, but the ECU monitors are wiped, here in PA it can't pass inspection without stored monitors of approximately 500 miles including highway miles.
5. Saw a YouTube video about maintaining the  ECU and other settings when replacing a car battery; wow, the OBDII connector can supply power to the ECU, that should        work for this.  Got a jump starter with a 12 VDC port and an OBDII cable with a 12VDC connector to attach to the  OBDII connector and maintain current to the ECU              when the car battery is disconnected to keep it from being drained.
6. Read the manual that came with the OBDII cable.  It says:
    CAUTION: 
    When the vehicle's battery is removed and the Memory Saver is 
    used to connect the vehicle's OBDII port to a power source, the 
    vehicle's batterty connection cables/hardware are live. Care must
    be taken to secure the positive battery cable/hardware to prevent
    arcing, damage or injury!
    To prevent overloading of a vehicle fuse or other vehicle damage,
    do not use the Memory Saver if the vehicle's current draw is 4 amps
    or more when the vehicle is in a KEY OFF condition.

So... 
Question 1: It seems that the OBDII connector does not just supply the ECU and radio but everything in the car is live. So I guess the parasitic draw would be drawing on the jump starter (which has an analog gauge to see the state of the jump starter charge and can be plugged in to an AC outlet to charge it, so perhaps not a problem? Just keep jump starter charged?)

Question 2:  And... if the vehicle is drawing more than 4 amps, don't use the Memory Saver cable to prevent overloading of a vehicle fuse or other vehicle damage.  Hmm... how do I determine that?  Can I just do an amperage measurement with a basic digital multimeter?  (Or would it require a more sophisticated meter?) If so, where would you put the leads?  Positive terminal cable to body ground?

Thanks so much, 
CaseyAtTheBat

 It seems that the OBDII connector does not just supply the ECU and radio but everything in the car is live. So I guess the parasitic draw would be drawing on the jump starter (which has an analog gauge to see the state of the jump starter charge and can be plugged in to an AC outlet to charge it, so perhaps not a problem? Just keep jump starter charged?)

In the case of your Civic, the Data Link Connector is connected directly to the battery via fuse #43 in the underhood fuse box. So yes, when you install your jump starter to the car via the DLC and disconnect the main battery, the jump starter effectively becomes the battery. Anything parasitic drains on the vehicle will continue to drain your jump starter.

If your only goal is to make it through inspection, then you may be better off using something like a trickle charger. I picked a NOCO charger off Amazon as an example:

www.amazon.com/NOCO-GENIUS5-Fully-Automa...ation/dp/B07W8KJH44/

Using this would eliminate the need for the DLC adapter and the battery disconnect.

And... if the vehicle is drawing more than 4 amps, don't use the Memory Saver cable to prevent overloading of a vehicle fuse or other vehicle damage.  Hmm... how do I determine that?  Can I just do an amperage measurement with a basic digital multimeter?  (Or would it require a more sophisticated meter?) If so, where would you put the leads?  Positive terminal cable to body ground?

Just about all multimeters will do current measurement, usually up to 10A. It's even easier for you because you've already installed a battery disconnect on the negative terminal.

To start out with, turn the ignition off and remove the key. Close and lock all doors. With the disconnect switch closed, set the meter to measure current (including moving the positive lead to one of the amp ports). Connect one lead to the cable side of the switch. Connect the other lead to the battery side. Open the switch. What the meter reads is your current draw.

My rule-of-thumb for current draw is 50 mA, or .050A. Less than that, I don't worry. More than that is a problem.

Dear Tyler,

Thank you so much for your reply which I unfortunately wasn't aware of at first; I now see the box to check to be notified of replies, I hope i have it checked right!

I had previously bought a battery charger at NAPA:

www.napaonline.com/en/search?text=hfdvbcm6a&referer=v2          

which in a later conversation with the counter guy at NAPA (after I'd made my first post here), told me I could use this battery charger to maintain the battery and do it indefinitely.  So, that's what I started doing, and later I saw your reply which mentioned using a battery charger so I thought, I'm good until I can do the diagnosis for the parasitic drain, just hook it up the the charger in the middle of the day and at night in my driveway (I'm a school bus driver so I go back and forth to work 4 miles away twice a day to work).  

Well, things keep coming at you and I haven't gotten to the drain diagnosis but I do have a multimeter now, ready to start but....

Yesterday morning at 5:30 am, no crank, no start, had dash lights on accessories, co-worker picked me up, thankfully, no one was available to cover my run!

 Today, Saturday, battery charger says Full, no crank, no start, no dash lights on accessories, but still have the blinking light on my radio so hopefully enough amps that the monitors in the ecu for LTFT are still stored.
    1. With MM, tested battery voltage: 13.16V
    2. With MM, tested battery terminals to cable connectors to see if a voltage drop was there, zero voltage drop
    3. Used a fully charged Jump Starter to jump it, it started right up, so the battery doesn't have the cranking amps, it's shot!
    4. Called NAPA, described, at first counter guy was trying to tell me you can't use that kind of a battery charger all the time, it has to be a "trickle charger" I told            him, you guys told me you could, eventually he told me it was within a year of purchase and could be replaced under warranty, good, it comes in on Monday.
    5. I also ordered a Battery Load Tester  www.napaonline.com/en/p/SOR1852 so I can monitor the battery.

So, now I've really got to figure out this problem!

Questions:
     1. Is this the right kind of charger?  Was it just a bad battery or did the charger ruin the battery?  Can I safely maintain the new battery with it?
     2. When measuring amperage drain at the battery terminal/battery disconnect:
         a)My MM manual has a 10amp port where you move the lead from the usual positive connection and set it to the 10amp setting on the dial, I assume that's                  what you're referring to when you mention moving the positive lead.  The regular port position measures up to 200mA.
         b)My manual's directions say, 
            "Remove power from circuit, open circuit at measurement point, connect meter in the circuit using the test leads, apply power to the circuit"
            Your directions say to put the meter over the disconnect while it is still closed, so I'm not sure what to do. I fried my first meter's fuse by having the settings 
            wrong, I don't want to screw it up!
          c)When the battery disconnect is opened won't the ecu lose power and wipe out the stored monitors?  Or would the amperage going through the meter                         maintain it? (as long as the meter is attached before the disconnect is opened?)

Whew, that's enough to figure out before I even get to starting the diagnosis!

Thank you so much for your help Tyler!  I really joined the right community by becoming a ScannerDanner Premium member!  I bought a hard copy of the book also so I can make notes in the margins from watching all the videos and then be able to use the book as a complete reference to the course materials; there's so much content!  I'm unfortunately still in the first section, Basic Electrical Skills, there's so much else in life that interrupts, but I'll get there eventually and I don't mind paying every month until I get there!  

I'll watch for your reply and if I don't get an email notification, I'll know I have the box checked the wrong way.  Thanks again!

Dear Tyler,

I worked really hard to format my post in the reply box so it would be easy to read
but when I submitted it, the lines had wrapped in different places and made it all a mess!

How do you post without that happening?

Thanks,
CaseyAtTheBat

I worked really hard to format my post in the reply box so it would be easy to read

but when I submitted it, the lines had wrapped in different places and made it all a mess!

How do you post without that happening?

Yeah, that's not your fault. The forums are undergoing some changes at the moment, and a lot of the formatting/features/interface get changed up daily. Definitely frustrating, but it's not gonna be forever.

In the mean time, if you end up with a post that you spend a lot of time on, you can always copy and paste it into a Word document or the like before you hit Submit. If the formatting doesn't turn out correct, you can always go back and edit it later.

1. Is this the right kind of charger?  Was it just a bad battery or did the charger ruin the battery?  Can I safely maintain the new battery with it?

I'm not familiar with that specific charger, but the product description sure makes it sound like it'd be fine for your application.

Did the charger ruin the battery? Probably not, IMO. But it's tough to say without further tests. Reconnect the charger and get the battery fully charged before proceeding with your draw testing.

2. When measuring amperage drain at the battery terminal/battery disconnect:

Yep, definitely use the 10A port.

Your meter directions aren't wrong, but they're not the best use of the meter in this case. The idea of having the meter connected across the battery disconnect while it's still closed is to provide a continuous path when you do open the disconnect (and measure the draw).

With the disconnect closed, your meter will read near zero. That's normal, as the vast majority of the current is going across the disconnect. With the disconnect open, you'll get your draw amount. As long as your draw doesn't exceed 10A, then your meter fuse will be A-OK. If your draw does exceed 10A, then the draw is huge, and you won't need an ammeter to find it.

 c)When the battery disconnect is opened won't the ecu lose power and wipe out the stored monitors?  Or would the amperage going through the meter                         maintain it? (as long as the meter is attached before the disconnect is opened?)

Exactly. The car never knows the difference. Not that there's a lot of modules to disturb on your car, but it's still good practice.

It's probably worth saying that, at some point during your testing, you're probably going to mess up and inadvertently take battery power away. Or pop your meter fuse. That's not commentary on you, it just happens. Especially when you're learning. Don't sweat it! Draw testing isn't easy to do well, even for professionals.

Dear Tyler,

Thanks for the kind words about blowing my meter, gonna try not to make dumb mistakes
but I spent hours on line figuring out where to get backup fuses so I'm not left hanging 
when I do!

I'm going to do a narrower column to try and avoid the post wrapping.

Can't get new battery until tomorrow now.  

You said:
"With the disconnect closed, your meter will read near zero. That's normal, as the vast majority of the current is going across the disconnect. With the disconnect open, you'll get your draw amount. As long as your draw doesn't exceed 10A, then your meter fuse will be A-OK. If your draw does exceed 10A, then the draw is huge, and you won't need an ammeter to find it."

Okay, if the draw is greater than 10A it will blow my 10A fuse and I'd have to go get the replacement (those little buggers are expensive!), then the draw is huge
and you won't need an ammeter to find it.  How would I find it then?

My battery has been on the charger since Saturday afternoon after I had jump started the car and let it run for awhile.  I didn't try to start it this morning, a co-worker got me.

I went to try measuring the amperage draw: got the probes to stay in contact with the disconnect closed. On the 10A scale with the lead in the 10A jack it read
0.04A .  Hmm, that's 40 mA, do I have that right?  Is that close to zero then for this use?  The battery is still connected.  I didn't disconnect the battery yet, 
want to make sure I've got this right.

To my amazement the car started, not sure if it's reliable to get to work and back but I do have the jump starter.

I also have ordered a battery load tester to monitor things going forward as I go through this parasitic drain diagnosis.  My co-worker told me there are different types, ones that place a load on the battery (which is drawing down charge, concerned if it would make the situation worse) and ones that use impedence and don't draw charge.  Tried to figure out which ones are which on the NAPA website, no luck, counter guys didn't know.  What about that?

Thanks,
CaseyAtThe Bat

Okay, if the draw is greater than 10A it will blow my 10A fuse and I'd have to go get the replacement (those little buggers are expensive!), then the draw is huge

and you won't need an ammeter to find it.  How would I find it then?

10A is a huge amount of current as far as draw testing goes. Drawing more than that would mean a big consumer is still on. For comparison, your fuel pump might draw 5-6A. Your low beam headlights might be 10A total. But you could probably hear the pump running, and you'd notice if the headlights were stuck on. In other words, if something like that were drawing on the battery, you'd know it by now.

I went to try measuring the amperage draw: got the probes to stay in contact with the disconnect closed. On the 10A scale with the lead in the 10A jack it read
0.04A .  Hmm, that's 40 mA, do I have that right?  Is that close to zero then for this use?  The battery is still connected.  I didn't disconnect the battery yet, 
want to make sure I've got this right.

Yep, you're good to go. The reading of .040A, or 40mA, is a good sign that you've made the connections correctly. Ohms Law at work. Because there are now two parallel paths for current to go to the battery (your meter and the switch), you're measuring a portion of the draw. Some of the draw is going across your meter, the rest is going across the switch. When you open the switch, you'll have your reading.

After that, you get into the real fun of finding it!

Casey, any progress? Not nagging, just following up.

Gosh, Tyler, thank you so much for the "how's it going",  and I'm sorry I haven't been 
on the forum to reply. 

I sprained my LCL in my right knee and it's really put a crimp in everything;  just been
focusing in just getting to work using the jump starter and getting through driving the 
40 ft bus with the lousy non-power brakes; hobbling to the bus and hobbling back to my car!

The long and short of it is; it's clear as mud!  I'd gotten a Viking Battery Analyzer from 
Harbor Freight to get more data about what's going on:

www.harborfreight.com/12v-digital-batter...em-tester-58759.html

The car had done a freaky thing on the way to Harbor Freight; the speedometer gauge was
flipping up and down to from the 30 mph I was going to 0 mph, the SRS light on the dash came
on and the car died in traffic. Re-jumped it with the jump starter, got it off the road sat for 
20 minutes at 2500 rpm, drove cautiously around the parking lot for awhile, seemed stable,
drove to HF, got the Battery Analyzer and some clamps to attach to my MM leads over the battery 
disconnect to do the parasitic drain measurements with, cause I only have two hands. 

Later at work I talked to our bus mechanic about the freaky behavior; he said it sounded like bad grounds.
Did research that night about where all the grounds are on this engine; next morning I injured my 
knee and it's been hit or miss since but I have moved forward.

The Neg Terminal Ground Cable and the Ground Cable A, which goes from the power steering pump bracket 
to the front bulkhead did look a little corroded and the A cable measured 7 ohms on a continuity test. I ordered
new Honda replacements and bolts and installed them with dielectric grease.

Parasitic Amperage drain measurements:  have gotten different measurements at different times;
only 20mA at times (wow, there's no drain!) to 2.25A once!  Did hours of research to know which fuse
controls what (like the ECU!) before I started pulling fuses, when finally ready, the reading was 20mA
again!

That was before I replaced the Neg Terminal Ground cable two days ago AND I finally found the G101 
connector ground (coming from the wiring harness and bolted onto the engine under the thermostat 
housing) and cleaned that up and re-attached with dielectric grease.

NOW,  recently, the coolant level in the overflow bottle has gone to empty once and after refilling, been 
losing small amounts that have to be topped up every few days. Can't see any liquid leaks anywhere, 
BUT, there is bluish/white-ish residue on top of the thermostat housing next to where the lower radiator
hose (which looks fine) connects. Hmm, did coolant leak onto connector G101 and affect that ground?
Covered in dielectric grease now.

Tomorrow, I pick up a NAPA Cooling System & Cap Pressure Test Kit 
www.napaonline.com/en/p/SER3700     to add to my toolkit and figure that out.

So, with my MM (and finally knowing how to test for a drain) and my Battery Analyzer I can monitor
how things are progressing and if it's fixed or ... is it not!!

Thanks so much for your kind assistance Tyler.  I am so glad I joined this community!  

Can't wait to get back to Basic Electrical Concepts...