Battery runs down

[lcfman]

I have a 95 ZR-1 that runs the battery completely down after sitting for an extended time in spite of having a battery tender hooked up. Should I put a cut off switch on the car or will lack of battery power damage any modules or electronics? Also are there any AGM batteries available for the ZR-1s?

[Paul Workman]

If the battery runs down IN SPITE of having a battery tender running, my first inclination would be there is a parasitic load in excess of the tender's capacity: i.e., 'there's a hole in the bucket draining more water than you are replenishing with a teaspoon' (in other words).

Current can be measured directly, using a VOM configured to measure AMPERAGE. OR, by measuring the voltage across a shunt resistor may be easier for a few good reasons. (Hint: "More than one way to skin a cat"... I have found a 10 watt, 1-ohm resistor connected between the disconnected negative battery cable and the battery terminal, using a pair of test leads with alligator clips on both ends is one way to do it. By Ohm's law, the voltage measured across a 1 ohm resistor is equal to the current passing through it. Expect a surge when the connections are first made, due to the various "always HOT" circuits requiring a few seconds to charge up. But, after a few seconds, the current will settle to a steady value which is the one we want to measure.)

My 1990 Z draws normally draws 33mA at rest, after the initial surge (which is well under the 750 mA capacity of my Battery Tender).

If your measured draw exceeds the capacity of your tender, that is why the battery drains in spite of the tender. But, if the draw is less than the tender's capacity, then either the tender is not working or there is a connection issue preventing the tender from charging the battery.

By using a blown fuse as a probe, and configuring the VOM to measure current, you can measure current by probing both ends of the fuse and reading the current directly. Also, CURRENT IS ADDITIVE. The total current draw of all the individual measurements will NOT exceed (33 mA, in the case of my Z, for example).

[Dynomite]

I have a 95 ZR-1 that runs the battery completely down after sitting for an extended time in spite of having a battery tender hooked up. Should I put a cut off switch on the car or will lack of battery power damage any modules or electronics?

Yes...A Battery Disconnect Switch is perfect.....I use one on each of 5 ZR-1s. NO....Lack of Battery Power will not damage anything except radio station memory will be lost :D

After sitting without power for 4 months the ZR-1s fire right up (NO Battery Tenders are used).

The Battery Disconnect Switch TIPS (http://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-8.html#post1587653767)

http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite11/9b113ff3-2c27-4600-aba8-a9f3456647a4.jpghttp://i287.photobucket.com/albums/ll142/dynomite007/Dynomite11/04ee613c-938d-4097-8632-8ae82f07897f.jpg

And the Battery Disconnect Switch is INEXPENSIVE with FREE shipping to your door :thumbsup:
Side Mount Battery Disconnect Switch (http://www.ebay.com/itm/SIDE-MOUNT-BATTERY-TERMINAL-BATTERIES-CUT-OFF-DISCONNECT-SAFETY-SWITCH-/331185335836?hash=item4d1c2f2e1c&vxp=mtr)

[lcfman]

Thanks for the replies I will get a battery disconnect switch. I like them to, I have a few on other non computer cars.