Battery memory saver

Barry14UK · May 29, 2021

Hi folks,

I would be grateful if somebody who has used a Battery memory saver when removing their 12v Battery on their Lexus, preferably an RX model, would clarify some things for me. The instructions that came with the one I bought off eBay are not very clear and the procedure shown in utube videos also varies and some readers comments add to the confusion.

I have tested the continuity between the saver and a spare Battery I have and it is ok, showing 12.5v. I have also checked the saver is working when plugged into the OBD2 (with the croc clips unconnected). I then come to my first query. Some videos show the crocs being applied to the slave battery and after this has been done then connecting to the OBD2 port, whilst others show this reversed. Is one way correct or more appropriate or does it matter? Also, after you have replaced your main Battery, does it matter whether you disconnect the crocs to the slave Battery first or remove the saver to OBD2 first?

Next query, some say doors should not be opened/closed as well as other powered circuits operated, (assume this would include hatch), while Battery saver being relied on. So if this is the case, hatch and driver's door would need to be open all the time the saver was in place.

There are some horror stories about damage to electrical components using Battery savers but these seem to be brought about by + and - crocs coming into contact. Naturally, I wish to avoid such damage, hence advice sought here as car systems can vary.

Incidentally, I think Lexus went out of their way to place the OBD2 port in a very difficult to see and reach position, meaning I had to kneel on my arthritic knees and use a mirror to locate it. No way would I want to attach a solar panel using this port! Also, the lit display came up on the reverse side of my Battery saver when connected to the OBD2, so I again had to use the mirror to read what was happening, so that's just the way the Battery saver is designed I guess.

I am aware that there are other methods of preserving memory but I want to use the Battery saver which seems to work for most people and is widely used in garages.

I need to remove the Pan Battery in order to tailor under Battery packing and fit alternative earth clamp terminal arrangement I have bought to facilitate fitting a higher Ah battery, about which more hopefully soon.

stringbender · May 30, 2021

Our resident "sparks" (Herbs) will be along soon with the answer to this. I'm no electrician but I'd have just put 12 volts ( in parallel ) from a slave Battery across the Battery terminals the second before I pulled the positive off.

Is there a problem with doing that ?

Alan

steveledzep · May 30, 2021

I'm not aware of Battery savers, so I'd have used the same solution that Alan suggests.

I can understand the concern about the crocodile clips shorting, so make sure the crocs are always on the Battery terminals when connecting/disconnecting the OBD plug.

Herbie · May 30, 2021

Well, with the greatest of respect Barry, you're overthinking it mate.

The whole reason to have or to use a Battery saver is to keep the car 'alive' so that things like the radio presets, the clock and so on, don't need to be reset after changing the Battery over. This is something that usually takes just a few minutes to complete but I am aware that your Battery will be out for longer because you're doing some work on the Battery tray.

Quite simply, all you need is another 12V source. This could be a spare car Battery, a mobility scooter or golf cart Battery, a burglar alarm Battery or whatever, it doesn't matter; it's just an alternative 12V source.

All I've ever done is to loosen the cable clamps on the existing Battery, croc clip the temporary 12V source onto the clamps (observing correct polarity of course), then lift them off the existing Battery and move them out of the way while you do whatever it is you're doing. This ensures that the 12V supply to the car is never interrupted so you don't lose any settings, doors can be opened/closed and so on. Just remember to make sure they never come into contact with each other or the +ve with any bare metal - maybe put the +ve clamp/croc in a plastic sandwich bag?

Barry14UK · May 30, 2021

7 minutes ago, Herbie said:

Well, with the greatest of respect Barry, you're overthinking it mate.

The whole reason to have or to use a battery saver is to keep the car 'alive' so that things like the radio presets, the clock and so on, don't need to be reset after changing the battery over. This is something that usually takes just a few minutes to complete but I am aware that your battery will be out for longer because you're doing some work on the battery tray.

Quite simply, all you need is another 12V source. This could be a spare car battery, a mobility scooter or golf cart battery, a burglar alarm battery or whatever, it doesn't matter; it's just an alternative 12V source.

All I've ever done is to loosen the cable clamps on the existing battery, croc clip the temporary 12V source onto the clamps (observing correct polarity of course), then lift them off the existing battery and move them out of the way while you do whatever it is you're doing. This ensures that the 12V supply to the car is never interrupted so you don't lose any settings, doors can be opened/closed and so on. Just remember to make sure they never come into contact with each other or the +ve with any bare metal - maybe put the +ve clamp/croc in a plastic sandwich bag?

Thank you for replies, particularly Herbs. Have to admit I am concerned about the the quality of the £10 ish Chinese Battery memory saver accurately storing the information and not causing other problems. It may work fine and this is used by many, but you don't know for sure until you have used it. So potentially, I might lose my settings or worse still cause some damage to electrical components. Clearly, it would be safer to connect my slave Battery to an earth on the car and clamp the positive to the outside of the positive lead terminal before removing the terminal to post on main Battery. I can use my jump leads for this enabling my heavy slave Battery to be used outside the car. Yes, I think I will go that way. I appreciate need to keep positive insulated and thank you for the idea of a plastic lunch box, I know some people use a rubber glove tied in place for this purpose.

Herbie · May 30, 2021

24 minutes ago, Barry14UK said:

Have to admit I am concerned about the the quality of the £10 ish Chinese battery memory saver accurately storing the information and not causing other problems.

I've never seen one of these units Barry but as far as I'm aware there is no information to store. A Battery 'saver' doesn't actually save or store anything, or if it does, then again it's a case of 'overcomplicating' things - but I really don't know how it could.

Taking the radio presets as an example, it's a chip in the radio itself that saves this information and it needs a 12V supply to do it. If that supply is interrupted then the chip is erased and the information is lost and the chip gets reprogrammed later on when you put the info back in.

Like I said above, all that's needed is just a 12V power source connected to the car while the Battery is out/disconnected.

ColinBarber · May 30, 2021

Agreed. Provided the Battery is outputting a voltage between 12v and 14.5 v then there shouldn't be a problem.

Just don't try to turn on the ignition, open the power back door etc with the only power source connected to the OBDII connector, otherwise you will blow the fuse. If you have smart entry it is probably worth keeping the key fobs away from the vehicle as when they are near it can trigger the brake vacuum pump to energise.

Barry14UK · May 30, 2021

One has to wonder when it seems these are only in effect a form of junction box between the spare Battery and the car electrical system why so many of these are sold. Would it just be that it is more convenient to plug into the OBD2? An example

There are many such 'savers' advertised, mostly cheap Chinese ones of non specific make, although some are marketed by well known names. Some are included here. https://www.google.com/search?q=memory+saver+car+battery&source=hp&ei=DgS0YJnxG8jQaI3Nu6gE&iflsig=AINFCbYAAAAAYLQSHumsWFV4nTUVUXfHB8Z6It6uiCFN&oq=memory+saver&gs_lcp=Cgdnd3Mtd2l6EAEYADICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADICCAA6CAgAEOoCEI8BOg4ILhCxAxDHARCjAhCTAjoLCC4QsQMQxwEQowI6BQgAELEDOggILhCxAxCDAToFCC4QsQM6CAguEMcBEKMCOggIABCxAxCDAToCCC5QpzRY7Gpgz4ABaAFwAHgAgAFdiAGuBpIBAjEymAEAoAEBqgEHZ3dzLXdperABCQ&sclient=gws-wiz

This is like the one I bought with a transparent case which shows the voltage. https://www.wish.com/product/5e1696c4afe01e0439849b0b?hide_login_modal=true&from_ad=goog_shopping&_display_country_code=GB&_force_currency_code=GBP&pid=googleadwords_int&c={campaignId}&ad_cid=5e1696c4afe01e0439849b0b&ad_cc=GB&ad_curr=GBP&ad_price=6.00&campaign_id=6493229882&exclude_install=true}&guest=true&gclid=EAIaIQobChMIionFwbby8AIVaAIGAB3pqgg2EAQYASABEgIpmfD_BwE&share=web

On my old BMW I just lose the radio presets so use the disconnect on the negative terminal clamp to help reduce discharge and reset when car is used (which has not been at all during pandemic), but with modern cars more settings, even performance ones can be affected.

Herbie · May 31, 2021

12 hours ago, Barry14UK said:

One has to wonder when it seems these are only in effect a form of junction box between the spare battery and the car electrical system why so many of these are sold.

No offence meant Barry because you're obviously the exception to the rule, but I honestly believe they sell most of these to people who don't know what they're doing and who are attracted by the fancy packaging and the jargon on it, and I think the term "Battery Saver" or "Battery Memory Saver" plays a big part in that.

The advertising blurb for these devices appears to be worded such that it encourages some people to think that there's something magical or mystical going on in order to 'save' settings, whereas in reality, the only thing that matters is a supply of electricity. Once the supply is interrupted the settings are lost, so just piggyback any other 12V source in parallel and that avoids the interruption of supply and keeps the settings.