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Old 01-27-2017, 03:20 AM   #76 (permalink)
Nautilus
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Join Date: Dec 2016
Location: Romania
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Simba - '05 Seat Leon FR
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AA cells may be a bit overworked unless the vehicle is a motor scooter.

When outside temps fall below the -7 to -9ºC range, at -12 to -14ºC (7-10ºF), the 12Ah+supercaps combo may not start. It holds 12.0-12.3 volts and cranks, but after the first 2 seconds of supercap discharge, it falls below 8 volts and cranks too slowly. This means the battery, which decreases in available amps as the temperature drops, is not strong enough to either replenish the supercaps at the same rate they discharge, or crank the engine by itself.

However, it's very easy to jump start. Just after connection to a fresh battery or running alternator, it starts just fine, as quickly as it does at positive temps. This happens because it needs only to replenish the supercaps, not the battery. Lead acid batteries which are too weak to crank charge slowly when jump started and need multiple attempts to give a strong cranking by themselves.

So it needs either a pocket sized lithium jump-starter, or an auxiliary lithium battery in the trunk. Or to be parked in some place where temps do not fall below -9ºC.

PS Laserhacker's experiment worked with a much smaller battery because he used a RC-car type lithium pack. These are made to give quickly a lot of amps for acceleration, almost like supercaps do.

Last edited by Nautilus; 01-27-2017 at 07:51 AM..
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