I have no power outlet (so no charging) where my C8 is stored for winter so I have been disconnecting the negative battery terminal yearly for storage and that works well but I need to remove the panels, disconnect, and in the spring, reinstall leads and panels. I was looking at a Remote Battery Disconnect Switch that you just press a button. Two questions:
1. The switch looks fairly big so will it fit under the panels?
2. The wiring looks thin. Is there an Amp minimum required for the C8 battery
3. Anyone do this?

 

For the cheap price it may be worth giving it a try. Sam

 

Side mount should work.

 

can you mount a solar panel outside? There are plenty of slow charging unit designed for car. If you can, then run an extension cord to the fronk cig outlet.
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Currently own:
2019 Mustang GT Premium 6MT Daily Driver
2023 Corvette Stingray 2LT
2017 Porsche 718 Cayman
2009 Jeep Wrangler Rubicon

 

I did not want to take my panels off and take a picture, but here are some views of the battery in its native habitat. I think there is room. If I were going to get one though, I would pop the panels off and plan where its going.

 

That looks like one nut to remove for the battery hold down. I've read there's as many as two for the top brace/holdown and another one at the base of the battery.

 

Two. Here is the other one, like you said.

 

Unfortunately I cannot use solar. I am renting some underground parking spots in a nearby apartment tower since my garage is full. The spots I have are 4 levels down.

Follow-up question for those understanding parasitic drain (or math): I see the unit has a 3mA standby current

So if our batteries are 70AH and this unit drains 3mA, a battery discharge calculator tells me that is 2333 hours till full discharge. So half discharge is 1166 hours and that is just 48 days so not really useful for longer storage. Or am I calculating something incorrectly?

 

I think so, yes.

3 ma is .003 amps. And 70/.003= 23333 hours or 972 days. Half would be 486 days.

I measured the parasitic draw of the car, and its about 10 ma or so. 3 ma is 30% increase in total draw. So, at 13 ma you have 5384 hours or 224 days. Half would be 112 days. But, do you want to discharge that much? Will you be putting a full charge on the battery before storage? The car only maintains an 80% charge so if you relay on that, the battery is already down 20%.

 

Take the battery out of the car and put it on a battery tender wherever you have power. Batteries can lose 1% of their charge every day. It may last a couple of years just using a kill switch but eventually the battery will die.

 

Thanks ! The on-line calculator I found was incorrect but another one showed me the 972 days. So here's my new calculations:
C8 Battery is 70 Ah. BUT only charged to 80% so 56 Ah is available. I heard we do not want to discharge more that 1/2 so 1/2 of 70 is 35.
Starting with 56 - 35 is 21 Ah to half drained. At 3mA gets me 271 days or just over 9 months ! Looks like I will try the Remote Battery Disconnect switch after all.

 

I just put my car away for the winter. It's in a storage unit without an electrical outlet so a battery tender isn't option. I disconnected the ground wire from the battery. You have to remember to keep the frunk open or you'll be crawling under the driver's side dash in the spring. I did this same procedure with my ZL1 for three winters without any issues. I guess I'll find out how well this works next April.

 

I get 21/.003 = 7000 hrs = 291.7 days.

I guess you don't need to account for the car parasitic draw since its disconnected.

 

I would not use an inexpensive battery switch. Go find something that prostreet cars use that have high amp batteries that are spinning up heavy duty starters for big block high compression engines. These are required at the drag strip and can be trusted. The problem will be mounting it.

but, I’d personally yank the battery if I were you and take it with me to trickle charge, or definitely consider disconnecting it and bring a jump box with me when I reconnect it. Don’t overthink it.

 

I do not disconnect the battery. I have a low amperage charger on my 2022 coupe.

DMK

 

AH ratings for batteries are not linear. The curve is somewhat exponential. 70Ah rating for a specific discharge rate (which is not generally supplied for commercial batteries) As an example, if the 70Ah rate was for 3 hours, then if you load the battery at 70A it would theoretically supply a reasonable voltage for 3 hours (relatively new battery), if you load it for less that 70A, say 35A, you would more than 6 hours or power, something like 10 hours. You really need the load curve for the specific battery.

 

The 2020 C8 service manual that I have gives an example of run down time vs current draw for low current draws. The example is for a battery that has 110 minutes of reserve capacity (RC), and a cold cranking amp (CCA) capability of 690 amps. The amp hour (AH) rating is not stated, but lets look at the RC. RC is the number of minutes a battery can sustain a 25-amp load before the voltage drops below 10.5 volts, whereas amp-hour (Ah) rating indicates the total energy a battery can deliver over time.

The C8 battery has the same RC, 110 minutes, as the example in the Service Manual, but a CCA of 730, a little higher than the example from the 2020 service manual. And it has an AH rating of 70 amp-hours.

Having the same reserve capacities, I think the example in the Service Manual is going to be in the ball park with respect to what will actually happen. And, table attached gives the time it takes to discharge the battery to 50% capacity , starting with an 80% charge. I think this is much better way to estimate how quickly the C8 battery will drop because 1) it starts with 80% which is exactly the target state of charge of the battery when running - the C8 does not charge it to 100%, and 2) I think a 50% state of charge is as low as I would like to go - I don't want to fully discharge the battery.

So the results in this table show that a parasitic draw of 25 ma (.025amps) will draw the battery down from 80% to 50% in 33 days. And, the inverse relationship between current draw and rundown time holds pretty constant for these low current draw. Thus, doubling the draw to 50 ma will draw down the battery in 16.5 days, exactly half. If the current draw increases 10 times, from 25 ma to 250 ma, the draw down time goes down from 33 days to 3.3 days.

From the table it can be inferred that the inverse relationship between current (I) in amps, and time (T) in hours is

(I*T) = 19.8 amp-hours or T = (19.8/I)
where T = time in hours and I = current in amps

This 19.8 amp-hours is NOT the amp-hour rating of the battery, but it is the apparent usable capacity when starting with an 80% charged battery and not allowing it to go below 50% capacity, based on this chart. And, perhaps with very high current draws this relationship might vary, as noted in a previous post, but for these low currents it holds pretty well. And it is an example, in the ball park - because this example battery has the same RC as the battery in the C8 (110 minutes).

A while back I measured the parasitic draw for the C8 at 10 ma after its all settled down. It wakes up from time to time so the draw is a bit more. But at 10 ma, and using the formula derived from the table, it would take 1980 hours or 82.5 days or 2.7 months, for the battery to discharge to 50% from 80%.

 

Open panel

 

I really do like your idea, but the simplest while not having to consider the draw-down etc. may be just disconnecting the negative cable at the battery for storage. Once you get panel R&R figured out, it shouldn't be difficult to do once a year.

Panel Removal:
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If money is no object, get an Anti Gravity Battery. You will not have to charge it or put it on a tender. I know they are about $1000 but you won't have to worry about it going dead.https://antigravitybatteries.com/?ma...ion=vpf-search