Battery dead again!

[Billygoat]

Had to pull my battery again to get recharged again. So something is drawing it down so I thought I’d start with the attached modification to get better cranking power because I’ve experienced this cranking issue. Is there any further write ups on this mode or is this power point it?

 

[Tybalt39]

Don't know if this will help, but check your boost solenoid wiring. Some PO added a second house battery bank but wired it to the starting battery side of the solenoid. This caused the house batteries to constantly drain the starter battery. Weak starts and eventually dead battery (and the "normal" house battery as well when I forgetfully left "boost" engaged for some hours). I killed two batteries before I noticed this.

 

[Billygoat]

Some where in my parts boxes I have a combiner, would that help to install that since I’m going through the wiring?

TG

 

[RF_Burns]

You need to troubleshoot your parasitic battery drain before making any changes to the wiring.

Get your multi-meter and set it up for 10 Amp current measurement. Turn the Ignition key to OFF position and remove it for now. Then disconnect the negative wire from the chassis battery and connect your multi-meter in series with the chassis negative wire and battery negative terminal (black wire to battery negative terminal and red wire to ground wire from the engine block).

Check the multi-meter for any current reading. It should be Zero or near zero. You may need to reconfigure your multi-meter to read a lower scale (next scale down is usually about 2 Amps).

If you are reading something well under 100mA, then you likely have parasitic drain from an accessory device like the dash radio or EFI module (if you have that). The OEM wiring for the dash radio is direct from the chassis battery, so I moved my radio power to the House batteries. Under 50mA should not causing any issues. Over 150mA I would look for the cause.

Also look for cellphone chargers, anything plugged into a cigarette outlet. Also look for PO installed devices like a hidden lamp.

Devices with electronic switches have been known to randomly turn ON. We had a new model of commercial two-way radio that was killing batteries. Turns out it would turn ON once the battery voltage dropped below 12V. Works as designed!!

Once you have found and corrected the parasitic drain, then consider moving the starter main power wire direct to the battery. It made a difference in cranking speed for me.

 

[Keith V]

Even 50ma will cause issues eventually if you arent on a battery charger.
The only car I have that can hold a battery over winter is my 65 Beetle, it has zero current usage when the ignition is off

 

[Tybalt39]

While I was diagnosing mine I used a battery cut-off at the negative terminal of the battery. Now I use a solar trickle-charger to keep it topped-off. Neither solves the root issue, but they can keep you operating while you figure it out.

 

[RF_Burns]

Even 50ma will cause issues eventually if you arent on a battery charger.
The only car I have that can hold a battery over winter is my 65 Beetle, it has zero current usage when the ignition is off

Very true! 50mA x 24 hrs x 30 days = 36Amp hours. So that's about 50% of the Amp-Hr capacity of a starting battery. Plus a lead acid battery can lose a significant amount of charge just sitting with no load connected.

I used to work at a CB/car radio shop back in the '70s when electronic tuners came out in car radios. I remember they drew about 250mA just on the battery memory lead. Add in a few other devices and many cars could not be parked from Friday night and be able to start Monday morning.

 

[mech0001]

Very true! 50mA x 24 hrs x 30 days = 36Amp hours. So that's about 50% of the Amp-Hr capacity of a starting battery. Plus a lead acid battery can lose a significant amount of charge just sitting with no load connected.

I used to work at a CB/car radio shop back in the '70s when electronic tuners came out in car radios. I remember they drew about 250mA just on the battery memory lead. Add in a few other devices and many cars could not be parked from Friday night and be able to start Monday morning.

I worked on Cadillacs in the 90's. We setup and performed overnight draw tests all the time. I think the allowable was about 55ma draw. 15 or so modules, most with a memory draw. Not the car to park at the airport for a couple weeks!

 

[LarryW]

I had a parasitic draw that took my start battery down to no start in about 2 weeks. Put in a negative battery disconnect till I had time to find the draw. Finally I then took a tail light bulb in a tail light socket and stuck it between the negative post of the battery and the negative cable. The bulb lit up very dim. Then started pulling fuses until the light went out. That was then the circuit I had to deal with. Had my wife watched the bulb while I pulled the fuses. It was a long time ago and cannot remember what it was, only that fixing it cured the dead battery.