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Old 05-06-2013, 11:52   #1
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Overcharge event on new lithium batteries

Hello
During recent sea trails with a new mastervolt system which comprises of 2 x 75 amp x 24v Mastervolt alternators and 2 x 180 ah 24v Mastervolt lithium batteries, power was cut. A check of the system has shown that the batteries were cut by the safety event triggers due to an over-voltage problem with the alpha pro regulators attached to the alternators. Recorded voltage on the batteries was 35.34v and 36.55v respectively. Any ideas on possible damage or shortened lifespan?
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Old 05-06-2013, 13:28   #2
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Re: Overcharge event on new lithium batteries

Merely charging at a high voltage wouldn't necessarily damage the cells. However, prolonged charging at HV when cells are full could. It sounds like your BMS cut off charging when it recognized the problem. Any bugling of cells/ or venting? those voltages are high for any battery! Hopefully your BMS did it's job, please let everyone here know the outcome of this.
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Old 05-06-2013, 14:02   #3
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Re: Overcharge event on new lithium batteries

Thanks for quick response. Technical assessment by supplier will be undertaken early next week - will post the results. No venting apparent at the time and yes it was only for a short duration before shutting off.
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Old 05-06-2013, 20:15   #4
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Re: Overcharge event on new lithium batteries

Winston cells are designed to run between 2.5 and 4.0 per cell.

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We just ordered 8 of these for our home's 2.88kw backup solar system, to be delivered in early August.

I doubt you will have any damage if the over voltage charging was short lived.
Do you have any idea how long the overvoltage condition lasted and what the charging current was?
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Old 05-06-2013, 20:58   #5
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Re: Overcharge event on new lithium batteries

It does sound like your BMS sensed a high voltage event (HVE) and opened a contactor.
We really need a lot more info on this event to be of any help to you:
> What are the absorption and float values for your alternator regulators and what is the high voltage cutout (HVC) for your BMS?
> Does the BMS respond to a battery pack HVE or a cell level HVE?
> Does the BMS open a relay in the power to the alternator regulators prior to opening a contactor to ensure that the alternator output diodes are not over stressed?
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Old 05-06-2013, 23:00   #6
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I'm guessing s loose wire. I doubt, given the low impedance of a LFP battery, the alternators could get the terminal voltage that high. The actual facts will be interesting when determined.

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Old 07-06-2013, 06:13   #7
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Re: Overcharge event on new lithium batteries

How did you determine the max voltage the batteries reached? What did the voltage drop to when the charging current was stopped?

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