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Possible to trickle charge motorcycle off Model 3 12v?

cascade

Member
Jun 3, 2018
11
1
Austin TX
Hello everyone,

I live in a highrise condo building and park my car in the building's parking garage. I paid to have a 240v HPWC run to my unit, but I don't have access to a standard AC wall outlet that I've used to trickle charge my motorcycle battery in the past. I am wondering if there is a simple, safe way to trickle charge my motorcycle occasionally by drawing power from my Model 3 since the car has unlimited power via the HPWC. I thought about using an inverter that Ive used on laptops before in other cars to power the AC trickle charger (Battery Tender brand), but it seems rather inefficient to go from DC to AC back to DC again. Any tips or suggestions on how to accomplish occasional trickle charging of the motorcycle given that I have available?

Thanks in advance!
 

buddhra

Member
Dec 29, 2017
235
307
San Luis Obispo
Ehh, I like where your head is with the efficiency, but I wouldn't want to risk killing my Tesla's battery and all the headaches that would bring. I'd lean more towards using a portable battery pack that you could charge in your condo. There are many different flavors of them, but you could either get one with 120VAC output if you already have a tender like that or a just 12V accessory outlet or one that has everything including jumper cables, like so: https://amzn.to/2xL1M2m.

Of course, another option is to bring your motorycle's battery up to the condo to charge.
 

BioSehnsucht

Model 3 LR
Apr 1, 2016
1,790
4,812
DFW, TX
Might be easier to find a 240V battery tender and hook that to 240V than to go from 240V to 120V. You'd probably still need to have an electrician wire in a 240V outlet in proper enclosure (if necessary) to make the building happy. Possibly with a manual transfer switch to toggle between the HWPC and the outlet for the tender, to guarantee you can't try to overload the circuit.

Too bad there aren't HWPC daisy chain compatible devices for charging other things (whether it be other EVs or running a trickle charger for 12V) - at least that I know of. If there were, you could daisy chain the wiring and they would automatically switch back and forth as needed which one was getting power.
 

paladinfello

Member
Apr 11, 2016
57
32
San Francisco
How would that step down transformer tie into my existing HPWC setup? Would I need an electrician to come hardwire it in?
A step down transformer would lower the line voltage from 240v down to 120v. You would plug this in between the wall outlet and your trickle charger. Given that you've installed a HPWC, there wouldn't be an outlet to plug anything in to. You would need to have your electrician install an outlet, assuming a 14-50 for 50a circuit, and then you would need an adapter from 14-50 to whatever plug your step down transformer is. I also found this which looks like it takes a 14-50 and splits the lines into 2 5-20 outlets.
It might be easier just to run an extension cord to the nearest regular outlet when you need to trickle the bike.
 
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ShockOnT

⚡️⚡️⚡️⚡️⚡️
Jun 26, 2016
3,393
3,079
Sydney
I don’t see why you can’t use the 12V outlet in the car. It should be fed from the cars main battery.
The cars main battery will drop a few percent before it uses the HPWC.
 

widodh

Model S 85 and 100D
Jan 23, 2011
6,853
2,773
Venlo, NL
I don’t see why you can’t use the 12V outlet in the car. It should be fed from the cars main battery.
The cars main battery will drop a few percent before it uses the HPWC.
I think that it works as well. If you "just" tap off 12V somewhere in the Model 3 and hook it up to your motor cycle it will keep the motor cycle charged.

If the 12V drops the internal charger of the Model 3 will kick in.
 

NeverFollow

Active Member
Aug 9, 2010
1,278
732
I live in a highrise condo building and park my car in the building's parking garage.
I paid to have a 240v HPWC run to my unit, but I don't have access to a standard AC wall outlet
that I've used to trickle charge my motorcycle battery in the past.
I am wondering if there is a simple, safe way to trickle charge my motorcycle occasionally by drawing power from my Model 3
since the car has unlimited power via the HPWC.
I thought about using an inverter that Ive used on laptops before in other cars to power the AC trickle charger
(Battery Tender brand), but it seems rather inefficient to go from DC to AC back to DC again.
Any tips or suggestions on how to accomplish occasional trickle charging of the motorcycle given that I have available?

Thanks in advance!

DBPOWER 600A 18000mAh Portable Car Jump Starter


Use A TESLA To JUMP START Another Vehicle
 
Last edited:

paladinfello

Member
Apr 11, 2016
57
32
San Francisco
I don’t see why you can’t use the 12V outlet in the car. It should be fed from the cars main battery.
The cars main battery will drop a few percent before it uses the HPWC.

I think that it works as well. If you "just" tap off 12V somewhere in the Model 3 and hook it up to your motor cycle it will keep the motor cycle charged.

If the 12V drops the internal charger of the Model 3 will kick in.

The problem that individuals have been having with tapping the 12V is the Model 3 does not like anything taking 12V power without it knowing bout it. This is the issue that almost everyone is having when they tap the 12V line to power their dashcams in parking mode. After a few months the car will throw a 12V batter replacement error because of the unaccounted discharge/charge on the battery. The argument could swing either way with a device using more power than a dashcam but being plugged in less often.
It seems like the easiest and cheapest solution would be getting a portable jumpstarter charged and ready to jump your bike when needed (might not be great for bike's battery health). That or run and extension cord to the nearest 120 outlet and power the trickle charger constantly.
 

dhrivnak

Active Member
Jan 8, 2011
4,456
3,699
NE Tennessee
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Reactions: Xenoilphobe

widodh

Model S 85 and 100D
Jan 23, 2011
6,853
2,773
Venlo, NL
The problem that individuals have been having with tapping the 12V is the Model 3 does not like anything taking 12V power without it knowing bout it. This is the issue that almost everyone is having when they tap the 12V line to power their dashcams in parking mode. After a few months the car will throw a 12V batter replacement error because of the unaccounted discharge/charge on the battery. The argument could swing either way with a device using more power than a dashcam but being plugged in less often.
It seems like the easiest and cheapest solution would be getting a portable jumpstarter charged and ready to jump your bike when needed (might not be great for bike's battery health). That or run and extension cord to the nearest 120 outlet and power the trickle charger constantly.
Hmm, ok, that’s odd. Although the trickel charge of a motor cycle will not draw that much, almost nothing.

Other option is just to install a AC socket next to the HPWC by tapping off the 240V there.
 

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