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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Wed Oct 09, 2019 5:30 am 
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Joined: Fri Jun 19, 2015 11:09 pm
Posts: 23
so, i have two simple questions about the 12v battery (which i replaced recently). what does it do and how does it get recharged?
tx,
ferenc

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Wed Oct 09, 2019 5:58 pm 
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Joined: Mon Apr 01, 2013 11:42 pm
Posts: 308
Location: San Diego, CA, USA
ferenc wrote:
so, i have two simple questions about the 12v battery (which i replaced recently). what does it do and how does it get recharged?
tx,
ferenc

It provides 12v power for all of the systems in the car...computers, headlights, navigation, seat heaters, etc... It is charged by a DC to DC converter that operates when the traction battery is active. This happens when the car is "Ready" and during charging, I believe. Only a few things run directly off the traction battery: The electric motor, the heating element for the cabin heater, and maybe the AC.


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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Wed Oct 09, 2019 11:19 pm 
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Joined: Thu Jan 17, 2013 11:13 pm
Posts: 1790
Location: Los Altos, CA
davewill wrote:
ferenc wrote:
so, i have two simple questions about the 12v battery (which i replaced recently). what does it do and how does it get recharged?
tx,
ferenc

It provides 12v power for all of the systems in the car...computers, headlights, navigation, seat heaters, etc... It is charged by a DC to DC converter that operates when the traction battery is active. This happens when the car is "Ready" and during charging, I believe. Only a few things run directly off the traction battery: The electric motor, the heating element for the cabin heater, and maybe the AC.

There are separate HVDC PTC heaters for the cabin and the battery pack. The A/C compressor also runs on high voltage as well as the electric power steering.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Thu Oct 10, 2019 6:12 am 
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Joined: Fri Jun 19, 2015 11:09 pm
Posts: 23
Thanks, so theoretically, one _could_ use the EV for limited current emergency off-grid power, through a 12v inverter ...
I wonder what the rated charging current and voltage to the 12V battery are, or if one would have to charge the battery, disconnect/turn off the car and then hook it up to the inverter?
Ferenc, who had initially hoped to do so directly with the large battery pack ...

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Thu Oct 10, 2019 8:36 pm 
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Joined: Thu Jan 17, 2013 11:13 pm
Posts: 1790
Location: Los Altos, CA
ferenc wrote:
Thanks, so theoretically, one _could_ use the EV for limited current emergency off-grid power, through a 12v inverter ...
I wonder what the rated charging current and voltage to the 12V battery are, or if one would have to charge the battery, disconnect/turn off the car and then hook it up to the inverter?
Ferenc, who had initially hoped to do so directly with the large battery pack ...

It is pretty easy to get 1,000W out from the 12V system. Just make sure the car is on and READY so that the DC-DC will maintain the 12V from the traction battery. Also, don't use an AGM battery if you will leave the car parked for extended periods in READY like this. They will overheat and vent toxic fumes. I have a disconnect on my AGM and I connect a LiFePO4 12V in parallel.

This is my RAV4 EV set up for 12V power export. The green knob on the negative terminal disconnects the Bosch battery.

Image

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Tue Oct 15, 2019 1:35 pm 
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Joined: Fri Jun 19, 2015 11:09 pm
Posts: 23
miimura wrote:
ferenc wrote:
Thanks, so theoretically, one _could_ use the EV for limited current emergency off-grid power, through a 12v inverter ...
I wonder what the rated charging current and voltage to the 12V battery are, or if one would have to charge the battery, disconnect/turn off the car and then hook it up to the inverter?
Ferenc, who had initially hoped to do so directly with the large battery pack ...

It is pretty easy to get 1,000W out from the 12V system. Just make sure the car is on and READY so that the DC-DC will maintain the 12V from the traction battery. Also, don't use an AGM battery if you will leave the car parked for extended periods in READY like this. They will overheat and vent toxic fumes. I have a disconnect on my AGM and I connect a LiFePO4 12V in parallel.

This is my RAV4 EV set up for 12V power export. The green knob on the negative terminal disconnects the Bosch battery.
...

This looks great! I did so, rather ad hoc during our recent power outage, loading the system up to 850W. I don't understand what the green knob is connected to - some sort of high current switch? Is your system turn-key or custom? I love the monitoring meter, as well as the quality of the workmanship. I resorted to using large clamps onto terminals, but would prefer to have a setup similar to yours,
Ferenc

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Tue Oct 15, 2019 5:01 pm 
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Joined: Thu Jan 17, 2013 11:13 pm
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Location: Los Altos, CA
ferenc wrote:
This looks great! I did so, rather ad hoc during our recent power outage, loading the system up to 850W. I don't understand what the green knob is connected to - some sort of high current switch? Is your system turn-key or custom? I love the monitoring meter, as well as the quality of the workmanship. I resorted to using large clamps onto terminals, but would prefer to have a setup similar to yours,
Ferenc

The green knob is a disconnect. It allows you to easily reboot the car. In my case, I also cannot leave the car in READY for extended periods of time because the Bosch AGM battery overheats. I have a LiFePO4 battery that I temporarily connect when I want to leave it on for long periods. Just opening that green knob takes the Bosch battery out of the circuit.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Tue Oct 15, 2019 5:12 pm 
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Joined: Fri Jun 19, 2015 11:09 pm
Posts: 23
so the green knob comes with the setup, or is the setup custom made?
is it a high current switch or something mechanical/home made?

i'd be interested in buying/making something similar - how did you accomplish your setup?
thanks.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Wed Oct 16, 2019 5:18 pm 
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Joined: Thu Jan 17, 2013 11:13 pm
Posts: 1790
Location: Los Altos, CA
ferenc wrote:
so the green knob comes with the setup, or is the setup custom made?
is it a high current switch or something mechanical/home made?

i'd be interested in buying/making something similar - how did you accomplish your setup?
thanks.

The green knob thingy is a standard automotive battery disconnect accessory. You can find it at most auto parts stores. I bought this one: Harbor Freight - Battery Disconnect Switch

The rest of the non-OEM stuff you can see in the picture is either part of the JdeMO installation, or added by me for the 12V power export. Here's the parts list for the power export:

Amazon - 100 amp breaker
Amazon - 100 amp DC current shunt meter
Amazon - Anderson type 2-4ga 175 Amp Connector
Amazon - 4 gauge wire and crimp lugs
Amazon - 4 Position waterproof connectors

Lastly, I designed and 3D printed the bracket to hold the shunt and the breaker. It uses existing M6 threaded holes in the engine compartment.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Thu Oct 17, 2019 7:13 pm 
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Joined: Wed Nov 14, 2012 9:50 pm
Posts: 4075
Location: San Diego
You can use a simple M8 wing nut. Every JdeMO™ installation includes this. We would be happy to send you one with a flat washer.

https://shop.quickchargepower.com/12-Vo ... ONNECT.htm

The Bosch AGM battery has been a disappointment over the years. Yes, you want a Group 24F or bigger battery, and you want the largest amp hour rating (not cranking amps... we don’t need that). It also should be a deep cycle type battery. AGM would be a plus.

But, the Bosch batteries fail too often, and overheat too much.

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