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BQ24650: Battery not charging

Rafael Cruz
Prodigy 30 points
Part Number: BQ24650

Hi!

We've been trying to use the BQ24650 as the charger for a lead acid battery, as you can check on the schematic. We followed the slva437a application for a 1.6A charge current

Our voltages are as follow:

VCC: 23.97V

VFB: 1.8V

SRN: 12.73V

MPPSET: 1.54V

STAT1: 23V

STAT2: 17V

VTS: 1.9V

REGN: 6V

VREF: 3.29V

And this is what it looks like on the battery side:

Could you please help us?

  • 0
    TI__Mastermind 24075 points
    Hi Rafael,
    Is this scope capture showing charge current? I will review the schematic and calculations and get back to you with comments.
  • 0 in reply to Kedar Manishankar
    Prodigy 30 points

    Hi Kedar,

    The scope is showing the discharge current applied to the battery by the IC, as it only does that while VCC>SRN. 4mA is the current that the battery provides for powering a few extra components (DC/DC, comparators) that shouldnt affect the charge cycle at all.

  • 0 in reply to Rafael Cruz
    TI__Mastermind 24075 points
    Hi Rafael,
    From your test results, it looks like both STAT pins are high indicating a charger fault. Table 8.3.20 shows a table indicating which faults could be present, and you should test for these conditions. From your test results, we can rule out TS fault and SLEEP mode (VCC = 23.97V > VSRN + 150mV). If possible, can you recreate this test setup on BQ24650EVM? All your settings minus the float charge setting can be recreated on the EVM, and will give you a good template as to how your board differs from the EVAL board. To account for timer faults, are you observing the charger operate correctly, and then stop or is it never working at all?


    Can you also include a scope capture of VFB (not SRN)?
  • 0 in reply to Kedar Manishankar
    Prodigy 30 points

    Hi Kedar,

    The charger is not working at all, as far as we can tell.

    We are going to receive the EVAL board this week so we can try to replicate the issue.

    VFB Scope:

    Regards,

    Rafael

  • 0 in reply to Rafael Cruz
    TI__Mastermind 24075 points
    Hi Rafael,
    Let me know results from EVAL board. Feel free to open a new thread to re-open this discussion. It will be useful to also go through the different fault states, which is what you are currently seeing on your board.