Hi, I Am Going To Do A Custom Stainless 3.0" Intercooler Piping And Was Running Piping Around Battery. Does Anyone Know Of A Good Compact Battery? I Dont Want To Relocate It To Inside Car.. Thanks,
Chris

 

Try the battery from a mazda miata. They're half the size of the one the FC uses.

 

get a yellow top dry cell and put it where the spare tire goes u can get a car audio amp wire kit made by streat fx at wallie world with giant 4 gauge wire to relocate the battery for 25bucks! just my 2cents

 

Hawker genesis.. Bout the size of a motorcycle battery.

 

thanks. how much is the genesis battery? does it last long? has it ever died? i'm going to run an e-fan that draws 13-18 amps.. do you think that battery will be fine?

 

actually what you want is a red top battery
optima yellow arent good for cold cranking amps
and he said small battery, not honking drycell

 

get a honda battery. Those things are small as all hell.

 

http://www.portablepower.com/product...ies/Hawker.asp

 

I never recommend that anyone with an RX-7 use a smaller battery. The reason is that very simple. If you flood the car and have to crank it for an extended period, the battery has very little capacity and cannot turn the car over for very long before it's dead. If you're out in the middle of some field somewhere with no one around for 50 miles, you're boned (ask me how I know and why my experiment with smaller batteries was ended immediately...).

Is this going to be a problem every day? No, of course not. If the car is in good shape and starts immediately without flooding the you won't have a problem. HOWEVER, it is inevitable that you are going to flood the car at least once and based on luck it means that it will be at the side of the road in a freezing rain storm at 2AM on a country road where another car won't pass for 3 hours...Then you're going wish you had the battery capacity to unflood the car and start it right up!

Another problem with the small batteries is if you have a habit of leaving the stereo or lights on. A few hours of running the stereo or lights means that your battery won't have the juice to crank the car. So it will crank slowly, then flood....

Relocate the stock battery or even better, relocate the battery then upgrade to a good aftermarket battery (not an Optima!) like those made by Deka or Hawker.

 

Go to wallyworld or your local auto parts store with a tape measure!
In Hawaii, does he have to worry about 'cold' cranking amps?

Battery size won't make a difference with an e-fan. Get a bigger alternator, increase your idle, and upgrade all the ground/power wires, to increase charging needed for the e-fan load.

 

i use a odyssey motorcycle battery, i think its called the odyssey PC80 or something. you can get it on ebay and even get it with the normal car style terminals if you want, its super small compared to a honda or miata battery, but like aaron cake said theres risks involved with running a tiny battery that you should be aware of.

 

Out of curiosity, why hasn't anyone ever used NiMH? They're less than 1/5th the size of a lead acid with the same power. I know you need to limit the charging current on NiMH, but otherwise they charge/discharge the same way as lead acid. You'd need an expensive high current NiMH, though, to match a lead acid's cold cranking amps. And a NiMH would probably need replacing more often since it doesn't like the frequent mini-recharges that happen in a car (lead acids are the opposite; they don't like deep discharge/recharge).

Is this for sale? Has it been custom rigged before?

 

Totally different charge and discharge curve. PbA batteries are easy to judge SOC...Just look at their voltage. NiMH will show basically the same voltage throughout most of the curve until the very end. Most good NiMH chargers will need to measure AHs in and out to determine SOC, as well as pressure and voltage. It's not a simple retrofit.

Not true. NiMH doesn't mind half/quarter/etc. cycles. They have no "memory" effect. All the currently produced hybrids use NiMH for this reason.

Deep cycle PbA handles this fine.

 

NiMH have no memory effect mostly due to modern improvements in battery chargers. Even NiCad batteries do well on these chargers. There are no old NiMH chargers with the problem, b/c common NiMH chargers aren't that old. NiMH will still have a shortened life compared to deep discharge & recharge. Likewise deep cycle batteries can handle deep discharge, but they don't prefer it. Saying "deep cycle lead acid" is like saying "stainless steel". You don't see "stainless glass" because glass doesn't corrode. Likewise you don't see "deep cycle NiMH".

But yeah, I can see a NiMH setup being very complicated.

Hmm... maybe if you had a low capacity lead acid for when the engine is running and a high capacity NiMH for when the engine is not running (and for ignition). The lead acid would be hooked up as normal, with diodes preventing current flow from the lead acid to the NiMH (but current could flow from the NiMH to the lead acid and hence to the rest of the car's electricals). An ordinary NiMH charger powered by the alternator would charge the NiMH battery. You'd need a switch or relay to cut off the NiMH charger when the engine is not running. 14V may not be enough to power the NiMH charger, so that may be an issue. - I think such chargers are good only up to 7.2V nominal (6 x 1.2V nominal). See any other problems with this setup?

 

Well, a properly running car should not exhibit flooding tendencies. Especially those that run on standalones. Sounds to me like your experiment ended because you failed to remove all the controllable variables.

My self and others have been running those smaller batteries for YEARS with no problems. Sorry your experience was a bit sour.

Be aware that unless the battery is outfitted with a cutoff (and the alternator too), the car will not be allowed to compete in NHRA, be it test and tune or otherwise.

Just a little FYI.

Rat

 

is it possible/wise to arrange two smaller batteries to make up for the capacity? supposing you have two small locations you can place them.

 

Yes. There should be absolutely no difference between 2 small batteries and 1 large battery. Make sure their capacities (rated in Ah) add up to the capacity of the larger battery. Using identical batteries may be nice (so they fail at roughly the same time), but it's not necessary. Connect + to + and - to -.

 

How?

 

There is a major difference between a deep cycle lead acid and a "regular" or "starting" lead acid. Deep cycle PbA will have much thicker plates and generally a weaker acid solution. Starting batteries have many thinner plates (to provide the high peak currents needed for starting) and a stronger solution. When you cycle starting batteries the thin plates corrode very quickly and after a few cycles you are left with a dead battery.

I'm trying to wrap my head around what you are saying and I can't seem to do so. I think I have it figured out though....

Would it work? Probably after you got the bugs sorted out. But you can't just leave an NiMH battery on charge like you can with a lead acid. You will start to overcharge the cell, it will heat up rapidly, then overheat and fry itself. If you intend to use NiMH, you need a battery management system and not just a charger.

There's no advantage unless you are seriously concerned about weight and if you are that worried, then just run a small lead acid since it will be a pure track car anyway.

How many cars on this forum are properly running?

My experiment was years ago, just a few months after I purchsed my '78 RX-7. I had a baby Optima installed and decided that I would leave my MP3 player turned on just for an hour or so while I did some work at a customer's. I tend to leave the player on all day in the 2nd gen so I didn't think anything of it. Cam eback an hour later to start the car, the engine turned over at like 50 RPM and the car flooded. By that time everyone had left the property and I was stuck in the middle of nowhere with a dead battery.

I know a lot of people running small batteries. I'm not of course saying that you can't do it, it's just not something I would recommend for most people.

Yep.

 

that may be true, but I dont think the ratio is as vast as everyone thinks. There are some very clean running FCs here in the 2nd gen section.. Then again, there are some fine examples of junk too..

 

I don't understand why moving the battery would make the car not raceable in the NHRA. What difference does it make that a cutoff switch is installed?

 

It's the rule. If the battery is mounted in the cabin it must:

-be secured to the body of the car
-have some kind of cut off device (in case of emergency)
-be in a sealed and vented box and of sealed construction (ie. AGM)

Those are the three main points though I am sure there are more guidelines.

 

The switch MUST be mounted on the rear of the car, it MUST have an "on" and "off" indicator clearly marked, and it MUST be able to shut the car off completely while the car is still running.

 

Man, dont ask me, ask the NHRA. I think its a ridiculous rule myself, but I dont get to write the rules.