rotary_FD3S

Hey I'm having an issue where my 1989 RX7 verts battery keeps going dead. Its a new battery. Any ideas would be appreciated

satch

iTrader: (1)

Have you made any recent changes to the car? Have you performed an amperage draw test?

rotary_FD3S

I literally just bought it Friday. How would I do that test and what would I need?

satch

iTrader: (1)

A multimeter set to DCma (ma = milliamps). Disconnect the negative battery cable. Place the Black meter lead to the battery post. Red meter lead to the negative battery cable. You should read a rather low draw of milliamps. Perform the test when the car has been just sitting there for a period of time to allow the circuits to turn off in case you recently had the car running. And make sure the car doors are closed as an open door will turn the interior overhead light to come on and thus cause an electrical draw. Post #35 in the link provided shows an illustration.

https://www.rx7club.com/2nd-generati...1031325/page2/

Also, if the alternator is connected improperly that could cause the battery to drain. Look at the FAQ thread at the top of ths 2nd gen page and it will show how it should properly be wired.

rotary_FD3S

Does the battery have to be fully charged to do this? What should it normally read?

satch

iTrader: (1)

That's a good question and I am not sure of the answer. You could try it regardless though. Do the test and provide the results and we'll tell you if it's acceptable or not. Actually, 30 to 50 milliamps is okay.

rotary_FD3S

OK I will. It'll probably be tomorrow though

jjwalker

Also, if you fully charge the battery and only get 12.35-12.4v fully charged then you have a dead cell.

If you have caps on top of the battery, you can test each cell if you want.

rotary_FD3S

What should it read?

rotary_FD3S

And also should the battery have two wires instead of one hooked up to the positive terminal?

satch

iTrader: (1)

Two wires in all. One wire runs to the engine fusebox while the other runs to the starter.

rotary_FD3S

So counting the ground wire 3 wires total?

satch

iTrader: (1)

Yes.

rotary_FD3S

And should those wires be big wires? Jw because they seem pretty big.

satch

iTrader: (1)

The positive and negative wires running to the starter are rather thick gauged wires. The wire running to the fusebox is not so big.

rotary_FD3S

Ok. I have the battery charging now and I'll test it when I get a chance

jjwalker

12.6 volts.

don't test the voltage immediately after charging, let it rest from the charger for about 10 minutes.

rotary_FD3S

OK I did the test and its pulling 70 ma if I did the test right. And its around 13v on the battery

satch

iTrader: (1)

You now need to to figure out what's causing the draw. To start with, you should pull the 60 amp BTN fuse from the engine fusebox and then recheck the amperage draw once again and see if it falls within reasonable limits.

jjwalker

70ma is too much.

Did you let the battery rest after charging and did you leave the meter on the battery for at least a minute when you where testing current draw?

rotary_FD3S

Yes I did

jjwalker

any mods to the electrical system, for example, aftermarket alarm?

rotary_FD3S

There was a sound system but it has been ripped out. How do I find out what it is?

jjwalker

The easiest way to figure this out is...

1. Place meter between chassis and ground set to current.
2. Pull a single fuse. Did you current draw suddenly drop below 30ma?
3: if no, put fuse back in and try another
4. If yes, replace fuse and start unplugging things tied onto that circuit.

rotary_FD3S

OK I'm at work now and it will probably be this weekend before I can do that.