Changing Battery, OBD2 Battery Keeper 1998 v70

[abscate]

Confirmed on ME7

Putting power onto the OBD connector will not preserve the ECU setting

[MrAl]

Confirmed on ME7

Putting power onto the OBD connector will not preserve the ECU setting

Hi,

Oh, do you know why it won't work?
I ask because they sell male OBD2 connectors with two wires and large alligator clips on the other end. To use it, the idea is to clamp the alligator clips on another battery and plug it into the OBD2 connector. They may say to plug it in first then connect the battery. Either way, the secondary battery voltage gets to the car battery terminals somehow. I know this is true on my car because for a short time I was charging the battery through the OBD2 port, the always-live positive terminal and one of the grounds. The battery did charge, but I didn't like that I found out that the wiring to the OBD2 port was very thin so i installed much heavier wire from the battery to the solar panel.

What kind of car were you talking about though, and what year/make/model, etc.

[wizechatmgr]

Why not just buy the device and prove to yourself it does or doesn't work? Abscate is telling you it won't. My experiences with him are such that if he says it won't work, he's already tried it personally. He's got a fleet of Volvo's and some choice VWs.

Sometimes manufactures will install zener diodes so that a bad scan tool cannot backfeed and frick up the ECU. On some cars the OBDII socket is powered from the ECU directly. On others, not so much.

I believe the current you're going to need to keep everything happy is going to exceed the little tool you think is going to avoid this issue, but your experience will tell you for sure. I'm interested in your result because I happen to have a '98 sitting out front. I've never had a need to bother with a memory saver tool. Frankly unless you think you have massive issues with the car, the value of using it typically won't exceed the purchase price. Typically you're just going to need to enter the radio code & stations after losing battery and that's about it from your end. A couple drive cycles later and everything is dialed back in.

[jmartin919]

I never loose the programmed radio stations. It comes back on at the lowest number (87.1 or something) but all stations stay in memory.

[MrAl]

Why not just buy the device and prove to yourself it does or doesn't work? Abscate is telling you it won't. My experiences with him are such that if he says it won't work, he's already tried it personally. He's got a fleet of Volvo's and some choice VWs.

Sometimes manufactures will install zener diodes so that a bad scan tool cannot backfeed and frick up the ECU. On some cars the OBDII socket is powered from the ECU directly. On others, not so much.

I believe the current you're going to need to keep everything happy is going to exceed the little tool you think is going to avoid this issue, but your experience will tell you for sure. I'm interested in your result because I happen to have a '98 sitting out front. I've never had a need to bother with a memory saver tool. Frankly unless you think you have massive issues with the car, the value of using it typically won't exceed the purchase price. Typically you're just going to need to enter the radio code & stations after losing battery and that's about it from your end. A couple drive cycles later and everything is dialed back in.

Hi,

Yes as to your first paragraph there i agree so maybe i'll just have to try it. On the other hand, i may like to do it in a different way.
On these cars they have a bolt sticking up from the battery terminals. You can use circular lugs on the end of the wires used to run to the secondary battery. That would be connected right to the battery terminals themselves. When the battery is disconnected, the terminals stay at around 12v or so. There is little danger the connection might come loose too which is a good thing because then the wires are bolted to the battery terminals.

The drain current when the car is off is reported to be around 10ma which really isn't that high. It cant be too high or else it would drain the battery too quickly.

[wizechatmgr]

Why not just buy the device and prove to yourself it does or doesn't work? Abscate is telling you it won't. My experiences with him are such that if he says it won't work, he's already tried it personally. He's got a fleet of Volvo's and some choice VWs.

Sometimes manufactures will install zener diodes so that a bad scan tool cannot backfeed and frick up the ECU. On some cars the OBDII socket is powered from the ECU directly. On others, not so much.

I believe the current you're going to need to keep everything happy is going to exceed the little tool you think is going to avoid this issue, but your experience will tell you for sure. I'm interested in your result because I happen to have a '98 sitting out front. I've never had a need to bother with a memory saver tool. Frankly unless you think you have massive issues with the car, the value of using it typically won't exceed the purchase price. Typically you're just going to need to enter the radio code & stations after losing battery and that's about it from your end. A couple drive cycles later and everything is dialed back in.

Hi,

Yes as to your first paragraph there i agree so maybe i'll just have to try it. On the other hand, i may like to do it in a different way.
On these cars they have a bolt sticking up from the battery terminals. You can use circular lugs on the end of the wires used to run to the secondary battery. That would be connected right to the battery terminals themselves. When the battery is disconnected, the terminals stay at around 12v or so. There is little danger the connection might come loose too which is a good thing because then the wires are bolted to the battery terminals.

The drain current when the car is off is reported to be around 10ma which really isn't that high. It cant be too high or else it would drain the battery too quickly.

On occasion modules have been known to turn on and draw more current while working on the car. Someone accidentally opens a car door trying to help grab keys or tools for instance...

[abscate]

I’ll double check the back feed on the OBD to ECU after a coffee in the morning

[MrAl]

Why not just buy the device and prove to yourself it does or doesn't work? Abscate is telling you it won't. My experiences with him are such that if he says it won't work, he's already tried it personally. He's got a fleet of Volvo's and some choice VWs.

Sometimes manufactures will install zener diodes so that a bad scan tool cannot backfeed and frick up the ECU. On some cars the OBDII socket is powered from the ECU directly. On others, not so much.

I believe the current you're going to need to keep everything happy is going to exceed the little tool you think is going to avoid this issue, but your experience will tell you for sure. I'm interested in your result because I happen to have a '98 sitting out front. I've never had a need to bother with a memory saver tool. Frankly unless you think you have massive issues with the car, the value of using it typically won't exceed the purchase price. Typically you're just going to need to enter the radio code & stations after losing battery and that's about it from your end. A couple drive cycles later and everything is dialed back in.

Hi,

Yes as to your first paragraph there i agree so maybe i'll just have to try it. On the other hand, i may like to do it in a different way.
On these cars they have a bolt sticking up from the battery terminals. You can use circular lugs on the end of the wires used to run to the secondary battery. That would be connected right to the battery terminals themselves. When the battery is disconnected, the terminals stay at around 12v or so. There is little danger the connection might come loose too which is a good thing because then the wires are bolted to the battery terminals.

The drain current when the car is off is reported to be around 10ma which really isn't that high. It cant be too high or else it would drain the battery too quickly.

On occasion modules have been known to turn on and draw more current while working on the car. Someone accidentally opens a car door trying to help grab keys or tools for instance...

Hi,

Very good catch. Those bulbs could draw 500ma each and there are several. That would put a strain on the wiring.
I guess we have to keep the doors shut.
Anything else you think might draw current?

[MrAl]

I’ll double check the back feed on the OBD to ECU after a coffee in the morning

Hi,

Oh ok thanks. Just be careful I wouldn't want you to lose your monitor readiness.

[wizechatmgr]

I’ll double check the back feed on the OBD to ECU after a coffee in the morning

Hi,

Oh ok thanks. Just be careful I wouldn't want you to lose your monitor readiness.

With the amount he drives? If they don't go ready, they never will! =)