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It seems to me there must be very little draw when parked. Either that or it waits for a pretty low 12V before the HV recharges it, because I've often gone a week or 10 days parked AND getting in & out (to pack/unpack stuff) with solenoid clunking, often brake pump activating, hatch light, etc (often using headlights to illuminate garage!) & only very rarely have seen 1% drop in the gauge.

Someone said it was posted somewhere online that a stack of AAs would start it. If so, you'd only need that much left in a motorcycle battery after any parking drain.
That might be but motorcycle batteries have a charge rate anywhere from 5~10ah im pretty sure the DC converter puts out more then that might stress the battery too much. Im not sure how it will all work, i mean if what you're saying is true they would of put a smaller battery in. The 12V system still needs to use battery as a buffer for the amenities like seat heater, guages, ecu, Hvac, etc, thats alot of load to put on a tiny battery.
 

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I believe most lithium iron phosphate chemistries can take pretty high current flow, around 3C, i think, which would be about 9 amps on a 3ah batt.

If there IS lots of current from the DC converter, that's really what's powering the heaters & such, same as if you just jumpstarted a dead 12V.

It was probably much cheaper for them to use an off-the-shelf car battery & connectors, all the same as their gas model. It is a "compliance" car after all.
 

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I believe most lithium iron phosphate chemistries can take pretty high current flow, around 3C, i think, which would be about 9 amps on a 3ah batt.

If there IS lots of current from the DC converter, that's really what's powering the heaters & such, same as if you just jumpstarted a dead 12V.

It was probably much cheaper for them to use an off-the-shelf car battery & connectors, all the same as their gas model. It is a "compliance" car after all.
Motorcycle battery are AGM lead acids battery not lithium. Unless you’re talking the aftermarket offer lithium for bikes.
 

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Right, like the link I sent in post #35 above on page 2 of this thread.

Either way though, the DC converter (or gas motorbike or car's generator/alternator/magneto) supplies voltage (around 14V) to the 12V batt. Car alternators will put out something like 50 or 60 amps, but it's not forcing that much through the battery because at only 14V it's only accepting easily-tolerable currents.
 

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It all comes down to knowing exactly what the at rest current draw is. You can then size the battery with the correct amp hour rating to fit your needs. ie. if you need the battery to last 10 days at x current draw per hour, you’d need a battery that can handle the drain of 10 days time 24 hours times x current. To get the current draw at rest you would need an accurate dc clamp on ammeter that can measure in the milliamp range.
 

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GREAT! Thanks RKW! It would be cool if you could send us a link or two for reference, or maybe just which forum it was (don't bother trying to find it on facebook, since we know that's impossibe)
 

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I found a link, thanks again to RKW posting it elsewhere on this forum, linking to the applicable thread on another forum:

 

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You can have your 12V battery tested for free at most auto parts stores (AutoZone, O'Reilly, etc). Your 2017 battery will likely be good for at least another couple of years, but if you want peace of mind you can easily go ahead and change it.
This or using the linked load test unit is the right answer. While a multimeter or obd will give you a reading, it can make for a false positive as it doesn’t put a load on the battery which is the real test of a good battery. That said running an ev likely puts a lower load than what you would turning over an ICE, so it’s not a perfect test either.
 

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So how much amp output does this car need to switch on the HV battery and get everything going?
 

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So how much amp output does this car need to switch on the HV battery and get everything going?
I doubt anybody has tried to find the exact number, but it is very minimal. It only needs enough power to start up the electronics and then the HV battery will kick in with supplying 12V. Someone on the (now defunct) Google+ 500e forum said they managed to jumpstart the car with AA batteries strung together.
 

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In that case, starting current seems less of a limiting factor than parking drain, which also seems pretty low since it's only dropping my ancient 6.5-yr-old 12V by about 0.02V/day.

I've now read through every page of my link above, & the only issue reported was a motorcycle Li-ion with an older-than-current BMS, a 14.7V max charge spec, & possibly being used in a GAS 500 which may charge at a higher voltage. The battery eventually bloated, which is usually caused by over-voltage....:

OBD shows my 12V charging at 14.30V when the HV batt is charging, 14.06 when the motor is "ready", & 14.04 with the key on one-click "acc" mode, so to test the 12V battery's resting voltage with OBD you need to run it without the key, shortly after opening/closing the driver's door.
 
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