Rechargable batteries
That resistor controls the charge current to the batteries.
You can't measure or read that resistor anymore, so we must do a little sleuthing to figure out what it should be.
NiMH batteries do not like overcharging, and if that's impossible to prevent (it is in your case), then you should do only a trickle charge of about 0.05C
https://batteryuniversity.com/learn/article/charging_nickel_metal_hydride
You should charge the batteries at (1500mA) * (0.05) = 75mA (max)
You have 11V from the adaptor, dead batteries will be around 1.2V, so that resistor needs to drop (11V - (7 * 1.2) ) = 11 - 8.4 = 2.6V
To limit charge current under 75mA, the resistor needs to be:
2.6V / 0.075 = 35 ohms or more
47 ohm is an easily obtained standard value.  Picture looks like a 1/2W device
https://www.ebay.com/itm/47-Ohm-0-5W-1-2-Watt-5-CF-Resistors-Qty-5-Bonus/223631630544?hash=item34117be0d0:g:FQQAAOSwoOddXWHo
BTW, I don't expect you to follow the calculations or the justifications unless you want to ;)   I put them there so the community can keep me honest.
BTW BTW, are you sure you have SEVEN (7) batteries in that green wrap?  Looks like SIX (6) to me.  7 would be a very unusual configuration.