I've had my Z for about 10 years now and have modded the #%& out of it. I've noticed that I'm eating batteries faster and faster as the years go by. before you ask - alt is ok.

This week I'm getting the vert back on the road and notice that with a nearly new battery it has starting issues, testing the battery shows that I start off well charged but after a few cranks the voltage is down considerable and the car will not crank any more without charging the battery, starts fine with a boost.

So I'll be getting a new battery tomorrow but was wondering to what extent do add on's cause battery amps to fall.

what I mean is this.
say you have a new battery ~700 amps,

turn the key and the following demands occur:
starter
fuel pump
aux fuel pump (leftover from my FI days)
amp
1 fd capacitor (stereo)
extra ignition system (crane / MSD box)
stereo
pass window motor as I have done Brent's window starter switch mod.
lights
elec water pump
whatever else (ecm, scammaster box, ...)

Ok so I have disconnected the stereo and components and the daytime running lights but m still wondering if we can have starting issues because the sum of the power draws does not leave enough for the starter to do its thing?

should us folks with a lot of add one be looking for batteries with larger amp ratings or does this all happen so fast that the draws do not reduce voltage enough to prevent starting?

 

Turn everything off, hook an ammeter (multimeter) up in line between the battery (+ side) and the main red wire and make sure you have the meter set to measure current. You want to see if there is any current being drawn out of the battery.

Anything over 1/8 amp is bad.

I had a problem with battery drain and found 1.2 amps being sucked out, it turned out to be the trunk light being hooked up up wrong with my alram system.

 

Thanks - I'm not overly worried about overnight battery drains - but rather if there is too much demand for a standard battery at startup. There must come a point where all these electrical add ons overwhelm the stock battery

 

Measuring the cumulative current draw of all your "accessories" and adding to this your starter current draw and comparing that number to the battery's current capacity by load testing it will give you some idea of how close you may be to exceeding the batteries capacity, but they are just numbers and it is not a perfect test. Purchasing a good quality battery with a high CCA (cold cranking amps) rating should keep you from experiencing a no start condition as long as your charging system is adequately charging the battery.

Like the saying goes...you get what you pay for. In my opinion, there are a lot of marginal batteries being sold today...they may work okay for a very basic application, but will not withstand some of the more severe duty applications. Vibration will take its toll on a lot of conventional automotive batteries as well. The original GM Delco batteries and the NAPA "NASCAR" style batteries have always worked well for me.

Try eliminating some of those accessories or at least have the capability of controlling when they power on so they do not all power up at the instant the ignition swith is turned on.

 

get a yellow or red top. prob salve your problems right there

 

That would have been my suggestion. There has to be something drawing extra power or a short somewhere. Double check the alternator because if it'll start with a jump, then it usually isn't the battery. Recheck all your cables and measure the current as stated before.

 

this would be what i would do,
but i would wait about 40 min after you shut the key off, touch the red terminal to the positive battery post, black terminal to the positive cable and disconect the positive cable from the battery, now you can accuritly measure current draw, and the standard spec is anything over .5 amps is bad

 

I'm running a red top now, lots of reserve.

What's the "window starter switch mod"? Can't find it.

 

http://www.bfranker.badz28.com/fbody/starterkill.htm