this is likely a glitch of some kind, but I managed to get my soldier to have 45 storage space. the lvl 40+ soldier hosted a splitscreen game on the 2nd playthrough, and my friend was a new siren; i was trying to lvl up the siren. the soldier was just entering new haven, and when i did the claptrap rescue quest in tetanus warren, he got a new storage upgrade that put the total space at 45. so maybe if you splitscreen with a new character on your 2nd playthrough, you can keep getting storage upgrades instead of 'nade mods? i dont really feel like confirming this myself; id actually rather not have more storage space than you are supposed to be able to have if you played legitimately. 22.214.171.124 00:50, November 3, 2009 (UTC)tim
Psh, we aren't all purists. I'd personally LOVE to have >42 backpack slots! Gonna confirm this as soon as I round up money for a wireless router. Seeing as how this will take at least a few weeks, someone should go ahead and beat me to it. XD --Aelwrath45 00:59, November 3, 2009 (UTC)
I can confirm that it's possible to get 45 slots, I have it and my friend had it before I did. He got his from soloing through the New Haven claptrap mission and I got it from the same one on my own game with him on co-op (I was lvl 45 at the time, he was 47). I figure it must be a glitch since I've done a few more claptrap mission since then in hopes of getting more and haven't found any yet. 126.96.36.199 01:33, November 3, 2009 (UTC)
hmm... maybe its not a glitch then, since you can do it solo. i guess the only thing that suggests that 42 is the max is the name of the achievement/trophy ("fully loaded"); even the description only mentions "enough to earn 42," not "enough to max." maybe by the time you do all of them again a 2nd time you'd have 45-48 slots? 188.8.131.52 02:16, November 3, 2009 (UTC)tim
I Can confirm this at least on the ps3 you can get 48 slots, which is all the claptraps from the first playthrough and 2 in the second.
I've gotten up to 57 in my second playthrough on the 360, still have one or two claptraps to find still. --184.108.40.206 21:26, November 3, 2009 (UTC)
It seems that, on the second playthrough, getting Backpack SDU upgrades is random. --RinArenna 03:31, November 4, 2009 (UTC)
Haha, 43 is nothing... I happen to have a backpack size of 200. No joke. .ini editing is the way.
I'm level 33, and i have no idea how i got 200 slots in my backpack.. i didn't edit anything at all... weird..
you can have up to 72 maximum legit
12 initial 30 from PT1 claptraps 30 possible from PT2 claptraps
there is always a possibility when you complete a PT2 claptrap it will give you a Backpack SDU. Not sure tut they may also be tradeable (going to experiment with this on my Xbox)
I actually have 400 item slots. I AM a purist and I didn't want 400 because I hate robbing myself of the game, but sadly you can "catch" any inventory adjustments from other people. The guy who gave it to me edited his game data somehow and gave himself 400 slots, and I joined his game. Apparently it's irreversible. I'll see if I can get a screenshot.
If you log into a game where the host has modded his .ini files to facilitate larger backpack slots, your default number of backpack slots will be modified as well. You can simply go into the .ini file and mod the default backpack slots back to 12, which should put you back to normal. Pdboddy 20:50, November 16, 2009 (UTC)
In response to Pdboddy...is there a way to fix the number of weapon slots? A friend set his to 5 and now no matter what I do I can't get it fixed. I tried editing the .ini file, but I still have the extra slots (is there a weapon slots value in a few different places?). I normally wouldn't care except that it glitches and binds stuff on pickup a lot, and the weapons got lost in a hidden slot. The only way for me to get them out of my equips so I can manipulate it is to sell if to a machine and buy it back. I don't lose any money doing this but it's annoying as fk. - Effedup 08:10, November 26, 2009 (UTC)
You can read the wiki page to get the details, but currently the official limit would be 63. You can pick up 10 from playthrough 1, 5 from playthrough 2, and 2 from Zombie Island DLC.  You can't duplicate the slots using the multiplayer exploit, but you might be able to acquire more backpack upgrades by playing with other people who are helping claptraps and receiving new upgrades. You shouldn't worry about going over some "moral" limit because the continuous flow of DLC is sure to continue to provide more opportunities for upgrades. [OriginalBurch, November 26, 2009]
I have been playing multiplayer on PC and now I have a level 50 soldier with 3000 backpack slots, I don't know how but Im stoked. -Terrible One
I would have thought that editing the number back would have worked. However, instead of selling and buying back, why not just mouse-wheel until the gun is selected, and then drop it on the ground and pick it up again? Not the most optimum of solutions, but better than running back to a vending machine. Pdboddy 13:48, November 30, 2009 (UTC)
For those suggesting .ini editing, it's good in some senses, but bad in others. For PC users, this shouldn't be too much of a problem, but people on consoles, especially on Xbox Live, you may need to worry about getting the account banned; losing all your achievements/trophies (for those who find them somewhat important) and losing your account (for XBL, that you've paid for). As for the solution? I've heard that you can get all the Claptraps through PT1, then complete the Claptraps in PT2, if you get a GMod, then quit without saving and do the mission again until it gives you an SDU. Personally that's too much time and effort for me to waste, so I haven't even tried it yet.
LOL, I didn't even know it was possible to mod the 360 version at this point. Is it really possible to mod the 360 version comparable to editing the PC version's .ini? If there is, kudos to you console players that have been able to do such things, they really don't give enough inventory in this game...not if you like collecting guns and stuff like I do, anyways :)
In response to Pdboddy: Yeah, I play with a 360 controller, so honestly that didn't even occur to me. I'll have to remember that, because lord knows I pick up some shit guns running around...I'll go to cycle through with the Y button and be like "What the hell is this gun??" Not cool in a firefight, not cool at all... - Effedup 08:07, December 1, 2009 (UTC)