EEVblog Electronics Community Forum

Electronics => Repair => Topic started by: MrMosfet on January 08, 2022, 01:29:47 am

Title: EXFO Max-715B OTDR: Won't Charge Internal Lithium Battery
Post by: MrMosfet on January 08, 2022, 01:29:47 am

Have an EXFO OTDR that no longer wants to charge the internal battery LiPo battery. All other features/functionality work, if powered from the 9V-18VDC input jack although a battery is need for it to bootup. When on the red LED low battery indicator blinks red indicating a low state of charge... I've been charging the battery manually and have load tested with 100mA->500mA and the output voltage is steady at 3.9VDC

Control board output to the battery ~2.6VDC, I've checked it with input voltages ranging from 9-15VDC and tried sweeping a the thermistor terminal resistance from 1k to 25k and don't see any changes (Batteries thermistor reads ~10k at 75 deg F).  Not the most proficient with board level repairs but can usually poke my way through with a schematic, challenge I'm having is identifying the charge controller with limited success googling most of the chips.

I'm hoping somebody might be able to point out chip most likely related to the LiPo battery charging so that I focus additional research into identifying it

Title: Re: EXFO Max-715B OTDR: Won't Charge Internal Lithium Battery
Post by: abdulbadii on January 18, 2022, 09:24:19 pm

"Control board output to the battery ~2.6VDC"

Is it easy to find T there, to meter sec. winding output and to know that's value or 3.9 V it is?

Title: Re: EXFO Max-715B OTDR: Won't Charge Internal Lithium Battery
Post by: m3vuv on January 19, 2022, 11:44:35 am

Can you not bodge on a TP4056 ,and feed it with a 5v supply and let that  charge it?