A little thought on MSI GT70 NOS power limit

[Minami Chan]

The Haswell version of MSI's GT70 series have a power limit from the AC adapter of 180w max due to the NOS feature. And we all know that if you're running 4940MX + 980M or something likewise, and you want to push them to the limit, 180w is just not enough at all.

Recently I've consulted some technicians at MSI, only to confirm that this limitation is hard-coded into the EC firmware and can't be unlocked.

Then here comes my thought. The NOS starts to draw power from the battery once 180w is reached. What if we take a secondary adapter and wire it onto the battery bay (instead of installing the battery). In this way we might be able to utilize a lot more juice without modding the nb.

Any thoughts?

[blablabla1600]

In theory it should work. In practice its harder than you think. The battery has an internal circuit for controls and tests. If that's missing the EC recognises a no battery condition and throttles back the 4940MX and 980m once >180W are reached. Ok let's wire the second adapter on the battery's control board bypassing completely the cells. Each cell is wired separately for voltage controls so if a failing cell is detected its disconected from the rest of the system. If all the other cells are disconnected then Windows reports a 0% capacity battery, NOS fails to load. So back to the throttling condition.

MSI engineers do use an unlocked EC internally for testing purpouses (max system power consumption) but there are no plans on releasing it afaik.

[Minami Chan]

I thought Windows judges remaining battery charge via voltage.

A new idea. Keep the battery in, while charging it with a secondary adapter (do some wiring stuff). I think that will keep the battery level up and the NOS will keep going for hours.

[MrTwisT]

Windows doesn't know what proper battery voltage is. Voltage is not necessarily an indicator of capacity and charge. Different batteries have different voltages and discharge rates, you'd need a driver for each battery type for windows to have some sort of estimate. In reality, the battery's circuit reports the charge AND remaining time to the system. Some clevo models don't show remaining time because the circuit only reports percentage.

"Do some wiring stuff" is not a magical term that solves any problem. You don't see guides online like "Step 1 - Do some wiring stuff. Step 2 - Enjoy your mod." Putting two charging circuits in parallel across the cells in the battery is not a good idea - something will short out. You'd need to modify the closed-source/proprietary original control circuit to disable its own charging function, since you'd have two circuits outputs shorted together. Moreover, that circuit probably already has protection against "do some wiring stuff". It could be that if it detects a cell's voltage does not drop or the current draw is higher than that cell can provide it deduces something's wrong or someone is trying to tamper with the battery - so it disables that cell or reports a faulty battery to the system.

Laptop batteries while sound dumb and simple enough are far from dumb and simple. They are complex devices designed to be tamper proof and safe. It's not that the designers don't want people tampering with them because "we don't want people to have fun!", but because Li-Ion, Li-Po batteries are dangerous if handled incorrectly - they explode, burn, leak, etc. - and that is grounds for legal action for many consumers.

Second of all, it's not as simple as simply having the battery provide more juice. It's not the battery limiting the power draw, but the system's EC firmware itself. The whole system is designed with multiple kill-switches. The motherboard power controller will limit the power draw from the battery itself because it knows the battery probably can't provide high current. It's probably not even to protect the battery but the motherboard itself from too much power.

[Minami Chan]

The whole point is not to increase power. The point is to sustain that battery power. Normally NOS enables you 180+50=230w, enough for overclocking since you're going to face severe thermal problems before surpassing that power limit.

The reason I wanna mod it is that NOS kicks in only while your battery has enough juice. For long gaming session I can end up with an empty battery and tons of throttling after like 1 hour or so.

By "do some wiring stuff" I mean putting an extra power brick into the charging circuit on the mobo, not modding the battery itself since it's dangerous. It's like one brick for the power and another for charging up the battery while the battery is meanwhile discharging.

Wiring a brick onto the mobo to charge the battery isn't impossible IMO. Disconnect the circuit from the mobo voltage input and use another brick instead. I might be wrong though, not sure how this thing actually works.

[Eivis]

Personally i see 2 options here:

1. Leave everything as is and use it for as long as posible.

2. Tear down the battery and take out it's circuit, then calculate the maximum power that a new stock battery can give to the nb while on nos and select a proper power source. Connect the power source to the battery circuit instead of cells and try.

NOTE! I'm not held responsible if you try this and something for you fails. This is just a theory made up by a student of electronics in 5-10 min.