12 Volt Battery ICE'd

[wycolo]

Lift the hood of any ICE and there it is, the 12 volt battery with exposed terminals. Maybe a red plastic safety shield over the POS terminal. But no mystery, no hassle to get to the terminals.

Here is the MS done up in convenient ICE style:

Detail of Cover Plate:

Remove cover plate:

Overview:

Rear of Box:

Connections to MS:

14 ga "primary wire" stranded copper soldered to lugs:

Cover with "3/8 inch dia heat resistant uv black flex tubing". Caution: do NOT run both POS and GROUND in same single flex tubing!! They need to be separatly tubed in case incendiary situation arises.

Now you can hookup your boom-box or inverter in the Frunk. Or quickly connect a charger (10 Amps or less). Or tie in another small 12 volt battery for boosting purposes so you can limp the MS into Tesla Service. Or you can slowly bring a charge to an ICE battery, but disconnect before cranking that ICE.

Project is purposely based on everyday parts from my local General Store. The box is a shallow PVC 'gem' box. I chose Grade 8 bolts and nuts since they are anodized thus more rust resistant. I hit the rear connections with flat black spray and will follow up with some electrical tape. There should be plenty of room around the terminals for even the largest buzz-box clamps on a tow truck to fit. Red & Black caps from juice jugs. Box should be mounted a bit forward of the position I chose. Had to trim the cover plate due to rug curvature in the corner.
--

 

[Puyallup Bill]

Neat. Just moments ago, I was giving the LEAF 12 volt battery a conditioning charge and was thinking I'd like to remote the terminals on the Tesla. Thanks for some good ideas.

 

[FlasherZ]

I might suggest the use of brass bolts as terminals instead of steel or galvanized bolts to reduce galvanic corrosion potential.

 

[wycolo]

Brass bolts: not at local store, but a decent True Value or Ace Hdwre should have. Sharp utility knife readily cuts the tub liner so use care. Lugs were soldered over gas range burner (use ventilator!). Soldered rather than crimped connections 'cause I'm a Rust-Belt refugee. Might try circle cutouts on cover plate with rubber plugs that can quickly pull out. Most charger clamps would probably fit thru such holes.

Was going to put 'public address' speaker in this same spot but the passenger side seems to have enough room for that. Warning: investing effort in such a project almost ensures that the need for such a configuration will never arise. But hey, hang a mirror on frunk latch & electric shave yourself while standing up. Any more ideas out there?
--

 

[Cottonwood]

Why go to all this trouble? For charging at up to 10A, you don't need hardware this big.

I have found that the BatteryMinder charger maintainers do the best at smart charging a lead acid battery and their pulsed desulfate cycles are wonderful for battery life extensions. BatteryMINDer - 12 Volt 2/4/8 Amp, Model# 12248 is thier best 12V unit, will charge AGM batteries, and will charge at up to 8A.

The terminals for the BatteryMinder and Battery Tender products are compatible. The Battery Tender Extension Cable is a nice 12.5 foot extention cord. All you have to do it route this extension cord from the battery into a convenient corner of the Frunk. The hardwire, ring adapter that you put on the battery terminals includes a 10A fuse, so everything is protected.

Good Luck!

 

[wycolo]

> All you have to do it route this extension cord from the battery into a convenient corner of the Frunk. [Cottonwood]

Which is exactly what this exercise is, but in a permanent, all purpose form. Not only for trickle charging. Convenient since no panels or nosepiece to remove in order to access 12volt battery. Light-duty only: 14 gauge copper wire good for 10 amps continuous, no fusible links, breakers or fuses needed. If you feel the need you can add them somewhere. When the AAA Service Truck shows up, you can point him at these terminals and he will relate. Assuming frunk lid can be opened. Don't know about this!! Solution might have to be a cable to a ring-pull in a wheel well to be fail-safe. Right now I'm learning to park car in N (not P) so calipers don't lock up. Got bit by this one. So much relies on the assumption that 'service is just 10 minutes away' - well not out here it ain't!! It's DIY or die. So part of a work in progress.

Btw, Model S applies pulsed power on a regular basis to the 12v battery. See graphs posted on TMC.

And if your frunk is filled with fresh turnips, the terminals are high & dry.
--

 

[rdrcrmatt]

Bike guys use a product called a battery tender for our batteries over the winter. Perhaps a pigtail from one of those would be a good idea to have hanging in the frunk.

 

[Cottonwood]

Bike guys use a product called a battery tender for our batteries over the winter. Perhaps a pigtail from one of those would be a good idea to have hanging in the frunk.

The Battery Tender and the Battery Minder products are very similar, and as I said before, use compatible connectors for the +12V connection to the battery. Both use a sophisticated, multi-stage charging protocol that let's you get and maintain a full charge with an "attach and forget until you need it" method of use.

The Battery Minders are a little more money, but include a "desulfate" function that can help partially restore and maintain batteries that have been stressed by deep discharges. Also, the larger Battery Minder, the 12248, has a temperature sensor that you attach to a battery terminal. The voltage at 100% state of charge on a lead acid battery is higher at low temperatures and lower at high temps. If the charger does not compensate for this, you get an undercharged battery in cold temps and an overcharged battery at high temps.

As for opening the Frunk, maybe this little charging connector needs to hide behind the grill so that you can fish it out when needed, without having to get the Frunk open.

 

[Puyallup Bill]

Just to save a little trial and error, what are the threads of the studs behind the nose cone? I think I have misplaced all my thread gages. Thanks.

 

[wycolo]

> what are the threads of the studs behind the nose cone? I think I have misplaced all my thread gages. [P-Bill]

I just purchased 6 each of every different nut the store had in that size range. The POS post is bigger dia than the NEG on the frame, but no nut needed anyway. The NEG post is "fine thread" and I believe 5/16 dia. Exact thread pitch I do not know.

Tesla Service often has to remove Frunk Tub entirely to get into firewall area. Make sure they know to simply back the blue box out of tub opening. Just have to remove the small corner screws, and tilt Gem box out of the tub.

I need to go back in and attach some sort of plastic safety cover over the POS rear bolt head, using nylon bolts which I did not have available.
--

 

[Puyallup Bill]

Just to save a little trial and error, what are the threads of the studs behind the nose cone? I think I have misplaced all my thread gages. Thanks.

Both metric. Positive 10 x 1.50, negative 8 x 1.25.

Which brings a question to mind: Is this a metric car?

 

[Puyallup Bill]

Thanks for the inspiration,wycolo.

Just finished mine, but not quite as fancy as yours. I just drilled a hole in the tub and ran a pigtail into the frunk, sealing the entry with Household Goop. Terminated the pigtail with Anderson Power Poles, my favorite connector.

Thanks for the tip on possible removal of the tub - I broke the feed with Power Poles between the tub and the nose cone.