I have a 1997 850 that also has a mysterious battery drain. Was lasting about a week before battery dead. After about 6 months and 2 battery's I finally got serious about it today and checked the drain with an ammeter between the positive battery cable and positive terminal. It was about 170 Ma. I started pulling suspect fuses and found fuse #15 (OBD, courtesy lights, door open warning light, remote central locking system)to be the majority of the parasite load,(about 150Ma). During my investigation of the interior lights, I noticed that the black pin of the glove box switch was missing. Turns out the switch itself fell out of it's bracket under the glovebox liner and was somewhere inside the dash, always on. I had to take the glovebox liner out to get to the switch. Rather than find a new mount for the switch, I merely removed the bulb from the socket. After removing the bulb, my load on fuse #15 was gone. Hope this helps someone.

I checked the standby current draw on my 1998 V70T5 with a Fluke DVM. I had readings which bounced from 90-130ma. Since the Fluke is a digital meter I really couldn't see what was happening - a good reason to also own an analog meter!

I have an aftermarket (read imported) alarm/starter system and I've never figured out how it exactly works exactly. I alway use a key. Wish I could get rid of it (and all the lousy wiring) and return to the original OEM.

Cheng,

You may also want to check the trunk internal light. It has a manual switch that has a position for "Lit" even when the trunk is closed. In that position, the light will also be on without keys in the contact. Pull back seat armrest down to check if the light is on.
However, it seems you are using a weak type of battery, that coupled with your driving habits, is simply not holding up to the job.

Good luck,

Icelandic

47 refers to the physical size of the battery case, not the amperage. Your battery should have more than 500 cold cranking amps (CCA), a 120 hour reserve capacity and a 70 amp-hour or more total capacity (Volvo specs for temperate 4-season use). Many stores sell lesser batteries that won't hold up (even tho the physical size is the same). Maybe the ones you are buying are just too small for the car?

A "standard" small car battery (whatever that means) has about 45 amp-hour capacity. That is you can draw 45 amperes for one hour, 22.5 amps for two hours, or 0.16 amps for 281 hours or about 11 days. To me this sounds unreasonable. I believe a Volvo battery is much bigger and has perhaps nearly twice this capacity. Are you sure it's 160ma?

I would suggest looking at the charging voltage and being sure that all your cables are absolutely clean - all connections should be polished to a bright metallic shine. Be sure all connections are tight. Don't forget the engine/alternator grounding cables as well.

Do you park you vehicle for long periods of time or do you start/drive it every day?

Cheng:

You have obviously done your homework on the drainage problem.......just wondering what kind of batteries Walmart has. I have good luck with the AutoZone Duralast 800 amp batteries and always use the felt insulators on the terminals. There are lots of old postings on voltage drainage to sort through. Are all the wires tight on the alternator? Has the voltage regulator ever been replaced?