Memory Saver

Discussion in 'Honda Hybrids' started by Mendel Leisk, Jul 14, 2009.

  1. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    I've been thinking about pulling out our 12 volt battery, cleaning the posts and clamps, giving the case and surrounding area a wipe down, for some time now. What motivated me was our daughter and son-in-laws car: their battery was in very grubby condition, lots of build-up on the positive post, everything was very rusty and seized up. Now if only ours looked more like that...

    Then, I got a gift card from them, for Princess Auto, which got me browsing the P.A. website for ideas. One thing I came across was a "Memory Saver":

    a device that typically plugs into a 12 volt accessory socket. It uses a 9 volt battery to supply voltage while you have the big 12 volt battery disconnected, supposedly preventing the car's computer and radio, etc. from losing their memories. The linked item also comes with clamps. It's not clear if that is for hook-up to another car battery (instead of the 9 volt), or to replace the accessory type plug.

    A little more browsing on the net and I learned that portable Jump-Start units apparently can be employed as memory savers. I have on hand a Jump-N-Carry 660, and it comes with a cord with 12 volt accessory plug at both ends:

    Up till now I've just used it for periodically jumpstarting a car we were storing, but supposedly plugging it into a 12 volt accessory socket (and the 12 volt accessory socket on the body of the unit) would allow me to remove the car's 12 volt battery without losing memories.

    Except, I notice with a cell phone charger cord plugged into either of the car's two sockets, it's indicator light only comes on when the ignition key is in and turned to "I" or further.

    A little more browsing on the net, and I found a cord that has 12 volt accessory plug at one end, and OBDII plug at the other end. Supposedly the OBDII plug is always connected to the 12 volt, even without key in ignition, and plugging a 12 volt source such as the Jump-N-Carry into the OBDII will do the job, supplying 12 volts to the car while the regular 12 volt battery is removed. Here's a couple of links for that cord, the first from the manufacturer, the second a US source:

    Being in Canada, choosing the pricier shipping option that doesn't incur brokerage fees makes this cable prohibitively expensive. Locally I've phoned one place and emailed another. This item is fairly new. Hopefully I'll hear back today regarding availabity, price, etc.

    Another suggestion I've read is to just use the Jump-N-Carry's main jump starting cables and clamps, connecting the positive lead just a little downstream from the 12 volt battery terminal, say at the connection to the car's (conventional) starter, and the negative lead to a good ground.

    Having a look at our starter's positive terminal, it's pretty deep down in there, and looks delicate. Plus I'm a little nervous about the whole thing. I'm also a little nervous about connecting 12 volts to the OBDII plug-in, LOL.

    So, I'm in a bit of a quandry. One the one hand, I can forget the whole thing, just pull the battery, and then when re-hooked up, enter the radio code and presets, and let the car's computer recalibrate itself.

    But I have this Jump-N-Carry, and it appears to have the potential to save memory during 12 volt battery disconnection. Maybe someone in the know could help me with:

    1. Is it dangerous to have the Jump-N-Carry connected with the key in position "I" and connecting to the 12 volt accessory socket, and be disconnecting the 12 volt battery? (I strongly suspect it is, but not sure.)

    2. Is it ok to hook up the Jump-N-Carry to the OBDII port?

    3. Is hooking up the Jump-N-Carry directly to the starter and a ground ok? (There looks to be practical issues with this route, the starter terminal is small and difficult to get at.)
    Last edited: Jul 14, 2009
  2. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Mendel, here's what I did when I had to swap the battery in the Insight:


    As the unit is a sealed lead acid battery (12V), it kept everything running just fine. I clipped onto the positive lead and then to the frame for a good ground. No issues at all and I left it that way for a good 5hrs.
  3. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Yeah, I was thinking that too. Just put the clamp securely on the neck of the positive battery lead. Hmm, maybe I could get a cable with with 12 volt accessory plug at one end and semi-compact alligator clips at the other end. My Jump-N-Carry's clips are pretty massive, but it has this 12 volt socket, allowing you to vary the output type.
  4. diamondlarry

    diamondlarry Super MPG Man/god :D

    The Prius has a terminal under the hood which would make Sean's set up very handy to use. The battery in the Prius is in the hatch. In fact, Sean's set up would be about the only way to do this in my car since the 12-volt outlets are dead until the power button is pushed.
  5. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Here's another source for cord with 12 volt accessory plug at one end and OBDdII plug at the other end, the E-Z Red Memory Saver MSBD28 (Orange, 8 foot coil cord, indicator LED):

    This one has an led to confirm good connection.

    Edit: Looks to only ship to US, no good for me ;(
    Last edited: Jul 14, 2009
  6. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Ok, USAToolWarehouse has the E-Z Red Memory Saver MSBD28, for $12.70US, and will ship internationally. To me on west coast Canada the shipping is $26.50US, groan.

    I've used these guys before, got my Jump-N-Carry through them, but this is getting too pricey for a small item.

    I'll maybe just wander up to The Source (aka Radio Shack), and pick up a 12 volt accessory plug with leads, and some loose banana clips, make up something myself. If I could find a loose OBDII connector that would be great. You only connect positive 12 volt and ground portion of the OBDII.
  7. msantos

    msantos Eco Accelerometrist

    Hi Mendel;

    I don't think that memory saver would work well for several reasons:
    - The 12V accessory ports are part of an "isolated and open circuit" unless the vehicle is electrically powered up.
    - The current draw from a boot-up (no ice start) along with steady drain is too much for a lowly 9V battery anyway. Besides, the 9V level is too low and will cause several systems to crash.


  8. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Hi MSantos, thanks for weighing in ;)

    What about my Jump-N-Carry JNC660 jump start unit? It is rated 1700 peak amp and 20 amp hour It has a 12 volt accessory outlet. I'm thinking the Rolls Royce method is to use the JNC via the 12 volt accessory outlit with a cord with 12 volt accessory at one end, and OBDII at the other end. Apparently only the 12 volt positive and ground contacts are used at the OBDII. Very difficult to find this cord locally though, and shipping is too much, at least what I've found so far (see above).

    Alternately I can connect my jumpstarter directly or semi-directly to the positive battery cable and ground (per Sean). But this method bothers me: the JNC660 cable jaws are massive and likely to pop-off. Or jury rig a 12 volt accessory plug with more modest sized alligator clips??
    Last edited: Jul 14, 2009
  9. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    I'll attempt to insert some images. First, the E-Z Red Memory Saver MSBD28, one offering of this cable:


    And my jumpstarter:

  10. msantos

    msantos Eco Accelerometrist

    Hi Mendel,

    Have a look at a vacant fuse location and use that instead as a power-up point. I suggest looking at fuse socket #6 and that should work OK for you as well.

    In my case, I use a small 12V gel battery (extracted from a computer UPS) that I keep charged in my garage. When needed, this ~1kg battery connects to a plug I have latched onto fuse #6 which is also shared with my solar setup and is able to not only sustain the "car's memory" but also power it up without issues even when the OEM 12V SLA battery is gone. ;)


  11. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    I guess in a nutshell that is what I need: a readily available, out-of-harms-way positive connection point. Connecting at the 12 volt battery positive cable, right at it's end, is likely too precarious. And it seems to me the last thing you want is your power sources negative lead hooked up and the positive lead flopping around loose. Yeah, I think coupling my JNC with a home-made cable (12 volt accessory plug one end, modest sized alligator clips other end), the fuse box should work. Thanks.

    I'll still look for the OBDII cable though, I have a few enquiries out, and will post if I find a decent Canadian source.
  12. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    I have a cigarette lighter socket wired in under my hood, for a float charger. I just tapped into one of the many 12V lines in the engine bay. It's not fused, so less than ideal, but it works. $5 at walmart for the socket, with the wire tapping clips included. I did use it when I changed my battery last winter, and everything kept its memory.

    Just be aware that wherever you have the power source connected, the + lead on the battery will be active while you're working in there. I slipped an old leather glove over it while I was working. ;)
  13. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Andrew, I dug around and found an old Motorcycle Battery Charger, basically a 110 volt plug-in brick with a long cord, a coupler (that can only be plugged in one way) and a then a couple of short leads with red and black ring lugs. It's rated output is 12 volt at 500 milliamp (1/2 amp?). I might try hooking that up.

    Thanks also for the glove tip.
  14. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Well my 500 mA trickle charger worked, all the presets etc were remembered, and the IMA battery state-of-charge shows unchanged when I turned the key to postion "II".

    I hooked up by bolting the positive lead in with a secondary cable at the positive battery cable, and the negative lead to a clamp down bolt of an adjacent grounding cable. Once I had the 12 volt battery re-installed I disconnected the trickle charger leads. Still, a lot more hassle than that OBDII cable, if I could find one.
  15. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    MSantos, after having another look at your Solar Panel install thread, I understand better your suggestion to use vacant #6 fuse location: you simply plug and inline fuse with lead into that receptacle, hook up a ground lead also, and you're in business ;)
  16. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Been thinking about this for a few days, and I'm coming to the conclusion something like my 500 mA trickle charger (described above) could well be the best route. It has a pair of short leads with ring connectors, then a non-reversable connector, to long leads going into a brick that plugs into 110 volts. Works, secure, done!

    We have 12 volt accessory socket type phone charger cord. It has a power indicator light, and I've noticed a slight nudge can shut it off. That considered, maybe the convenience of 12 volt accessory plug is outweighed by the risk of momentary disconnection.

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