Battery relocation
- Thread starter MedicMike
- Start date
Alin
Diehard Car Enthusiast!
I'd be interested in learning as well.
@Batmobile_Engage @Grinder34 [MENTION=692]Eagleye[/MENTION] @IGOTASTi @HolyCrapItsFast @black bandit @Doppelganger @Boogieman98 [MENTION=3416]WRB_STi[/MENTION] [MENTION=5193]War_Panda04[/MENTION]
@Batmobile_Engage @Grinder34 [MENTION=692]Eagleye[/MENTION] @IGOTASTi @HolyCrapItsFast @black bandit @Doppelganger @Boogieman98 [MENTION=3416]WRB_STi[/MENTION] [MENTION=5193]War_Panda04[/MENTION]
Grinder34
Track Monkey
I haven't done it, but both my old MINI and my Current M5 have trunk-mounted batteries. Both are in the place where a spare would usually go, beneath the trunk liner.
I just did a quick google and people mentioned an external cutoff switch...not sure why you'd need that? But theoretically it should be simple to run a large cable to the trunk from the stock battery connection. You'd need to bolt/weld a battery box into the trunk, and make sure you had venting figured out. But it doesn't *seem* hard.
I just did a quick google and people mentioned an external cutoff switch...not sure why you'd need that? But theoretically it should be simple to run a large cable to the trunk from the stock battery connection. You'd need to bolt/weld a battery box into the trunk, and make sure you had venting figured out. But it doesn't *seem* hard.
A cutoff switch is always useful, and if you are going to the trouble of relocating the battery, you might as well put in a switch. Venting is definitely a concern. I know some people that don't have their battery in the trunk vented, and they haven't exploded. But if you ever intend to autocross or HPDE the car, a non-vented battery will almost definitely keep you off the track. Lastly, stay the hell away from the plastic relocation trays. I think there are a couple out there that are heavy duty ABS plastic, designed for racing applications. THOSE are okay, but most of the cheap plastic ones on the market lead to horrific results in the event of an accident. One guy I read about who got in an accident, had the plastic tray come apart and the battery continued on through the rear seats, THROUGH the driver seat and killed him by blunt-force trauma. If that wasn't bad enough, acid was everywhere and the vapors eventually started a fire that consumed more than half of the vehicle. So, basically what I'm getting at is, don't bother relocating the battery. The OEM did a lot of corner balancing that takes everything into consideration, including battery weight and how that balances other things in the car. But if you must, be damn sure that you purchase quality materials. Safety should always be the number one priority.
Grinder34
Track Monkey
Hmm, off the top of my head:
Lead acid batteries are usually vented. Not 100% sure why (vapor or liquid), but bad stuff can come out. Actually, it might be hydrogen released during charging/discharge? If it's in the engine bay, you dont really risk breathing it (or it exploding), at least in any significant concentration. If, however, it's inside the car, that can build up and cause health issues (or exposions) since you're essentially huffing it.
I think the need for vents is lowered with newer battery tech (e.g. Li-Ion) but not 100% sure on that. Even "sealed" batteries are supposed to be ventilated IIRC, but not sure how much of a rumor-vs-fact that is.
Lead acid batteries are usually vented. Not 100% sure why (vapor or liquid), but bad stuff can come out. Actually, it might be hydrogen released during charging/discharge? If it's in the engine bay, you dont really risk breathing it (or it exploding), at least in any significant concentration. If, however, it's inside the car, that can build up and cause health issues (or exposions) since you're essentially huffing it.
I think the need for vents is lowered with newer battery tech (e.g. Li-Ion) but not 100% sure on that. Even "sealed" batteries are supposed to be ventilated IIRC, but not sure how much of a rumor-vs-fact that is.
You have a major fire hazard or even an explosion in your boot, as while lead acid batteries are being "used" they release toxic and flammable gasses. Also the gasses could/will leak into the cabin .. if that doesn't kill you, then you'd prolly lose a damn few brain cells.
Hydrogen gas is the product of the acid-lead excitement. The gas will get so heavy that it becomes an explosive mixture of Hindenberg level. Add a little heat and some O2....POOF... LOVE THAT BILL NYE GUY
Hydrogen gas is the product of the acid-lead excitement. The gas will get so heavy that it becomes an explosive mixture of Hindenberg level. Add a little heat and some O2....POOF... LOVE THAT BILL NYE GUY
HolyCrapItsFast
Drinks beer!
You can get sealed lead acid batteries. Optima is one that is suited well for in trunk use and you can mount them in any position, even upside down. There are others as well but I forget the brands. I was thinking of going super capacitors myself but I have a thousand other projects I need to complete first
Grinder34
Track Monkey
The mention of supercapacitors made me perk up. Energy storage is something I'm very involved with at work (from the strategy side, not technical).
Anyways!
Supercapacitors are great for some good CCA, but severely lack in any sort of energy storage. Meaning you cant run your radio on battery for more than a few minutes. Leave your headlights on by accident when you run into the store? Dead....
The following graph is for weight. Meaning 1 KG of each gets you how much energy/power. Maybe not the most relevant for cars, except a lot of people switch batteries for weight purposes.
The next one is for size. If you wanted to cram something else in the same amount of space, how much power/energy could you get from each:
Remember, both of those graphs are on log-log scales! What you'll see is that capacitors and super capacitors are always SUPER high in power (you could start a 20L diesel) but very low in energy. Just gotta make sure you know what you're doing. (And I'm pretty sure you, [MENTION=9]HolyCrapItsFast[/MENTION] do...just posting this for others and potential discussion)
I couldn't follow along those graphs either. Jesus man!!! I did a battery swap to the rear in a 01 Ford Focus when I was into stereos but for weight savings for our cars I don't personally feel the need. The only way I would move it is to make room for a FMIC. Otherwise I would just do a lightweight battery from Odyssey, Braile or Optima. But if you do move it to the back for sure put in fuses and a cut off switch. Lots of sparks and unplanned welding occurs when shit goes wrong. Ask me how I know that!! haha.
