battery protection components

In a non-smart Lithium battery used in an oscilloscope.

BV3P1N SOP8 body - some kind of fet used back-back in series.

CGH1 SOT23 6pin possibly an undervoltage controller.

Any accurate info out there? At present the scope firmware interacts with the battery at end of charge in a potentially life-shortening and demonstrably firmware-corrupting manner.

No access to scope firmware....

RL

Reply to
legg
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Usually the protection cuts discharging below 2.4V and charging above

4.3 volts, with some temperature compensation. A PTC fuse limits current. There's nothing else to it - it's strictly for momentary fault protection.

An old battery may have a high impedance that's triggering firmware bugs. Fancy chargers have a lockout timer for restarting a charge cycle to prevent constant top-offs of a failed battery that no longer appears to be charged.

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Reply to
Kevin McMurtrie

I expect these to be fairly simple devices, but need more accurate info on what thresholds are expected, and method used to introduce hysterisis etc.

This is a brand-dedicated series/parallel pack that expects ~constant voltage charge limit ~ another issue of this end-use. Thermal fuse is present (no ptc).

Even new packs have the same issue at end of discharge in these scopes, though with less bizarre symptoms. Aim is to prevent firmware from tripping over itself, even if it means external rework in hardware.

Batteries become 'aged' fairly rapidly under the circumstances, with capacity halved in the first year, but they don't require a remote depot servicing at inconvenient times, as a result.

RL

Reply to
legg

4.2v is a better cutoff voltage for lithium cells, most are specced for 4.2v. Charging to 4.3 will halve the life of the cells and only slightly increase capacity. (4.1v will increase cell life by about 20% but reduce stored energy by about 15%.)
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Reply to
~misfit~

The protection circuit is only for momentary faults, like a short to 0V or a high unregulated voltage. I've never seen one that provides continuous protection.

From what I've read, 4.1 volts (temperature compensated) is the only safe trickle voltage and it never produces a full charge. I'm using a pair of LTC4070 for a pair of solar charged LiPo cells. So far, no explosion.

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Reply to
Kevin McMurtrie

The charging isn't the immediate issue, its interaction with the hardware at end of charge I'm looking at, hence need for info on internal UVLO circuit (assumed) components.

CGH1 SOT23 6pin

This is a series/parallel pack with trickle voltage speced at 8V4. If charging is aging the cells prematurely, it would only mean that EOC conditions were reached more often.

Distinct odor of outgassing from these devices, when plugged in, so the charging circuit will need some looking into.

RL

Reply to
legg

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