Battery want charge

dnoonkeste
I have a Bolens riding lawn mower with a new battery and it runs down, while I use it.  How come the lawn mower will not charge the battery, while it is running?  Model Number: 13W1762F065, Serial Number: 1B282B70443

Roy, provide it still has the original Briggs 310000 series that the IPL indicates and the wiring diagram is indicating a dual circuit stator [alternator] the the DC side is not providing the unregulated DC to charge the battery. If the fuse was blown the OP would not be starting the engine; unless, the OP is starting jump start at the starter.
 
The problem can be anything from simple bad electrical connection to a bad out stator. On the stator it can be either the winding has opened or the diode has opened. Also if the after fire solenoid on the carburetor has partially shorted it could drawing more than the 3 amp charge that stator produces therefore draining the battery during operation.
 

Roy
The IPL I found indicates the Powermore engne, I am not familiar with it's charging system.

If that is the case then it is likely the P90 engine which has a combination full wave rectifier and voltage regulator.
 
P90 charging system testing:
 
To test the charging system:
1. Locate the connection between the engine harness and the main harness of the machine.
2.Start the engine and run it at full throttle.
3.Check the engine RPMs.
NOTE: The engine must be at 3,300 RPMs to test the alternator output.
4.Connect the black (-) lead of a digital multimeter to a good ground on the engine.
5.Set the multimeter to read AC voltage.
6.Back probe the orange wire in the charger harness with the red (+) lead of the multimeter. See Figure 6.38.
7.The multimeter should read a voltage of 11 - 20 Vac.
NOTE: If the AC voltage is too low, remove the flywheel by following the procedures described in Chapter 7: Ignition System and check the internal magnets. If they are still magnetic, replace the stator.
8.Set the multimeter read DC voltage.
9.Back probe the purple wire of the charger harness. See Figure 6.39.
NOTE: Will be a different color on the equipment side of the harness connection.
10.The multimeter should read 13.75 - 15.5 Vdc.
11.If the results do not match the specifications:
11a.Turn off the engine.
11b.Disconnect the regulator/rectifier.
11c.Start the engine again and run it at full throttle.
12.Set the multimeter to read AC voltage.
13.Connect the black (-) lead of a digital multimeter to a good ground on the engine.
14.Connect the red probe to one of the red wires from the stator harness. See Figure 6.40.
NOTE: The meter should read 8.5 to 10 Vac.
15.Move the red probe to the other red wire.
NOTE: The meter should read 8.5 to 10 Vac.
NOTE: If the meter shows the proper readings, the regulator/rectifier is bad and needs to be replaced.
NOTE: If the readings don’t match what is listed above, check the flywheel magnets. If the magnet are still magnetic, replace the stator.

dnoonkeste
The fuse is not blown.  Engine number 120217ZA86172.

Roy
The schematic shows a 20A fuse that may be blown. Can you give us the engine model number so we can see details of the charging system?

That would the be the datecode/serial number of the engine. It is actually a Briggs 31A807-0905-G5 and it would be using the 592831 dual circuit stator. This means you have one AC circuit (for lighting)and a half wave rectified DC circuit. It most likely that the diode has open circuited; therefore, providing no DC to charge the battery. The diode would be the lump in the stator wiring.
 
Test voltages @ 3600 rpm are 14 VAC, 13-16 VDC, DC amp max is 3 amps without a regulator and 5 amps max with regulator.
 
It also means the engine is built by Briggs and not MTD. Briggs labels this engine as a Powerbuilt and MTD labels its engines as Powermore. Two completely different engine lines.

Briggs PN 393456. Also Oregon 33-414 and Rotary 9206. Just these part numbers.