Probably a LiMnO2 battery. Not safe indeed.
Jan de Jong
On 4/28/2012 5:52 PM, david park wrote:
> --> Europa-List message posted by: david park<dpark748@hotmail.co.uk>
>
> Recently seen a thermal run away on a seneca where battery is in the nose.
> Glad
i was not in the air with it.!!!!!!
>
> Sent from my iPhone
>
>
> On 28 Apr 2012, at 16:35, "Jan de Jong"<jan_de_jong@casema.nl> wrote:
>
>> I believe that a 12 V LiFePO4 battery is quite safe if used with care.
>> It does not have a thermal runaway mode, but will burn, not explode, if
>> mistreated
to an internal temperature of about 800 C (well above the melting point
of aluminium).
>> By the way, LiFePO4 is not for low temperatures; one example increases
>> internal
resistance (4 mOhm) below 10 C as follows: 20 mOhm at 0 C, 40 mOhm at -10
C etc.
>>
>> How I intend to use with care:
>>
>> 1. Charge with a CC/CV regime, just like a lead-acid battery.
>> CC: small alternator, charging current guaranteed less than 2C
>> CV: maximum charging voltage 14.5 V; less is ok but the maximum SOC will be
less than 100%
>>
>> 2. Cell balancing is much slower and worse than with a lead-acid battery
>> (because
a fully charged cell largely stops passing current).
>> Mitigation:
>> - long stays at CV interrupted by shallow discharges - normal starter battery
use actually
>> - apply an external shunt (3.70 V) across each cell to speed up balancing
>> if/when
needed
>> Monitor:
>> - all cell voltages must remain below 4.00 V; remedy: stop charging
>>
>> 3. Replace if ever discharged to below 20% SOC
>> Monitor:
>> - battery voltage must remain> 12.8 V; remedy: if needed carry on
>> discharging,
but do not recharge, replace
>>
>> 4. Have 2
>>
>> I designed a "monitor& top equalizer" for attachment to a Shorai LiFePO4
>> battery.
It has just two indications: 1. a cell has a shunt operating, 2. a cell
has a shunt operating but even so its voltage exceeds 4.00 V.
>> According to the battery suppliers no equalizing or monitoring is needed -
>> which
may be right ofcourse. Neither of the indications may ever show. On the other
hand - they do sell balancing chargers...
>>
>> Attached a typical charge curve for a LiFePO4 cell (author unknown). See the
current drop when a SOC of 100% is approached.
>>
>> Jan de Jong
>>
>>
>>
>>
>>
>> <40138chargeprofile.jpg>
>
>
|