Using 56W adapter with T42, safe?

[pianowizard]

I want to minimize the travel weight of my T42. I already have a travel bezel for it, but I am thinking about also using the 16V 3.5A adapter designed for the X series, which is lighter than the T-series adapter. The T42 can draw up to 4.5A current, so it's somewhat risky. However, I know that many Dell laptops get into a lower performance mode when a lower-power adapter is used, so that they won't draw more current than the adapter can supply. Does anyone know if the T42 is smart enough to do that too?

[richk]

No. I plugged one in by mistake to a T41, and the machine would run, but the battery wouldn't charge. I was testing a machine I bought, before I broke it up for parts, and I thought the charging circuit was shot, until I realized the adapter I was using was from an X31 (3.5A) I didn't wait long enough to see if the battery was slowly discharging, but I don't think you would be doing the machine a favor.

[carbon_unit]

Not completely safe.
I used to do that back when I had my T42. As long as you are careful you will be OK. You need to be either charging the laptop or using it fully charged. Make sure your battery is fully charged up before using the laptopwith a 3.5A power supply. Don't use the laptop while the battery is charging or the 3.5A power supply will get very hot and then you may damage the laptop.
My T42 was usually fully charged so I didn't have any problems. YMMV

[pianowizard]

Thanks guys for the very helpful info. I still like Thinkpads more than Dell laptops, but this is yet another case where Dells excel.

[gator]

However, I know that many Dell laptops get into a lower performance mode when a lower-power adapter is used, so that they won't draw more current than the adapter can supply.

PW, this is news to me ... do you know what model dell laptops do this?

[pianowizard]

PW, this is news to me ... do you know what model dell laptops do this?

I know Dell Inspiron 8200 and 6000 do that for sure.

[melmo]

My old Dell C840 wouldn't run at all when I tried to use a power brick from a C640, it would detect the smaller power supply and throw up an error screen.

I've sometimes inadvertently used a power brick from my old Thinkpad 600 with my T42 with no problems. Sounds like I probably shouldn't do that too often.

[richk]

The 600 put out 4.35 amps, which would probably be fine for X30/31 (3.5 amps) but not enough for T4x (4.5 amps)

[melmo]

Ah, that's only off by less than 4%, looks like I've got an extra charger for my T4x's now

I used to work for IBM designing power supplies, I feel bad - I should have looked into this myself (of course those were not for Thinkpads, they were for mainframes).

The 600 put out 4.35 amps, which would probably be fine for X30/31 (3.5 amps) but not enough for T4x (4.5 amps)

[richk]

not for T4s, but X30/x31