I have just finished rebuilding the engine on my 4runner. We put a brand new Optima battery in it and now we're having problems keeping the battery charged. Any ideas?

 

Welcome to YotaTech.

Do you have a multimeter? If not, Stop. Do not pass Go. Get one: https://www.harborfreight.com/7-func...ter-63604.html

Put the multimeter leads on the battery posts. With engine off, you should get something close to 12.6v (temperature dependent). At idle, you should get 13.9-15.1v (also temperature dependent). http://web.archive.org/web/201102051.../2onvehicl.pdf

If that checks out, you might have some parasitic battery drain. Engine off. Set your multimeter to the 10amp range. Use something like a twist-tie to hold the red lead to the + battery post, and the black lead to the cable that connects to the SAME post. (If you hook it up across the battery, it will instantly blow the fuse in the meter -- if there is one.) Carefully disconnect the cable clamp to disconnect it, leaving the multimeter as the connection from battery post to cable. You should get much, much less than 1 amp; probably closer to 0.020 amps (just enough to keep the clock running).