This is probably not even a Volvo question. Sorry.
For a lot of repair work, it is recommended to disconnect the battery neg first. This involves quite a bit of fiddling with the stereo afterwards: Entering the theft code, the pre-set station frequencies, the display color, the audio settings etc. etc. Is it possible to hook up a back-up battery to avoid this? Using say, a small 9V battery?
My stereo is a Kenwood KDC-V6090 radio/CD unit.

Erling.
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My 240 Page

I've always kind of wondered about the logic of applying current to the system to keep the radio on, when you are removing current ( the battery ) to protect circuits computers etc . It seems rather self defeating.Only time I could see this is when removing the batt to stick your hand down in dangerous places where the current from a small battery wouldn't really do anything
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '82 Mercedes 300SD for sale

Hook up a 9v battery plug to the memory wire (Yellow) and ground wires and attach a 9v before removal. This was std on the benzi box setup.

I like the 9V battery idea. I wired the constant power to my son's Radio/CD as a separate 12-gauge (2mm) wire straight from the battery with an inline fuse. I could tap into it somewhere downstream of the fuse with the 9V, pull the fuse, and the radio circuit is then isolated from the rest of the car.

You could do the same sort of thing if your constant radio power line comes from the Volvo fuse box, but note that after pulling that fuse, while you are isolated from most of the car, any other circuits on that fuse will be supplied with 9V. Virtually anything still switched on would flatten that little battery quickly, and your radio memory blacks out.
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Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and a few old motorcycles)

I just used to have a 9v plug wired into the back end of the radio with a 12 in length and installed a 9v before disconnecting the main battery and removed it after hooking up the battery again.

Benzi box used a 9v Nicad, I used a Bunny battery

This sounds great, thanks! Will this be a relatively risk-free project, considering the delicate electronics inside? I won't be feeding the system 12V + 9V this way, will I? "Benzi box" - you lost me there, I'm afraid. As is embarrassingly apparent, English is not my first language...

Erling.
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My 240 Page

Risk free as long as you simply ensure that + is hooked to +, etc. The batteries are hooked up in parallel, so the voltages won't be added together. But for the period before you disconnect the 12V battery (or pull the circuit fuse), the 9V will be getting "charged" by 12V...and dry cells are not meant to have this done to them. So I'd think one should be pretty quick to disconnect the 12V after hooking up the 9V.

Your facility with English is excellent and is better than many who claim it as their first language.

I lived on your side of the Atlantic for a couple of years and remember this saying from those days:

If you speak three languages, you're trilingual;
If you speak two languages, you're bilingual;
If you speak just one language, you're English;

...and I have to admit (now that you've gone first) that I, too, don't know what a Benzi box is.

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Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and a few old motorcycles)

s'posed to be a diode in that 9V trick.

this may not yet be admitted to "english" http://www.rapdict.org/Benzi-box

Clip a battery charger to the terminals before you take them off. That should provide enough juice to keep the settings. There are adapters that hold 9v batteries made just for this that plug into the lighter socket but if I remember right there is a relay in the circuit which kills the power when the key is off.
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Dave Shannon
Spring Valley, California
'67 1800s
'73 1800ES
'88-240
my pages