2000 Honda Odyssey Battery Electrical

TF89

MEMBER
2000 HONDA ODYSSEY
6 CYL
2WD
AUTOMATIC
175,000 MILES

2000 Honda Odyssey, replaced battery and alternator about 1 year ago. Van has been sitting for a couple of months, drove it for a couple of days without issue. About a week later went out to start and battery was completely dead. Attempted to start using jumper cables and let it charge about 1 minute before I tried to start it. The starter turned over, was weak and the solenoid starting clicking, so I stopped (total time about 5 seconds or less). I then let it charge about 5 minutes and when I tried again, there was nothing. The clock was working at that was it. I then moved the jumper cables to see if they were firmly connected and they were. I also noticed that there were no sign of electric flow (sparking) when moving the ground for better grip. The clock stopped showing time after about 10 minutes, assuming the little charge that was given upon first connecting ran out.
So it seems that there is a short or open relay in the system. The fuses looked okay under the hood. I didn’t remove any, just look through the little viewing panes and didn’t see any breaks in the wire.
Do you have any ideas as to where I should begin to look?

Thank you,
Dave

1 Reply

CARADIODOC

MECHANIC
33,871 POSTS

Don't forget to check the fuses inside.

There's a couple of things to consider before we assume you have a problem. The insane engineers have gifted us with a lot of unnecessary computers that do things we never needed computers for before. They all use a small amount of current to maintain their memories. Unless specified differently by the manufacturer, 35 milliamps is what's allowed, and at that rate a good, fully-charged battery will still crank the engine fast enough to start after sitting for only three weeks. You will likely get more than three weeks, but that's the standard.

To add to the misery, there are now some computers that take quite a while to go to "sleep mode" when the ignition switch is turned off. That can drain a partially-charged battery. Then, when the battery runs down, some computers will "wake up" again and draw high current. That can totally discharge the battery and could be related to why it was dead after only a week. You didn't say what kind of driving you did for those couple of days. If it was a lot of short trips with many engine restarts, the battery may have never fully recharged.

More importantly, you must be aware that to recharge a totally dead battery, it takes at least 15 minutes on a charger before the acid in it becomes conductive and it STARTS to take a charge. There is no way to get enough current through jumper cable clamps to run a starter motor. All you can do with jumper cables is to assist a weak battery. If you have a battery charger with an amp meter, you'll see with a dead battery, the meter stays on "0" amps, then by around 15 minutes, it slowly comes up to around 15 to 20 amps if you're using the low charge setting. After about an hour, the meter will show close to 5 amps when the battery is fully-charged.

Always use the lowest charge rate if you use a large wheel-type battery charger. The current pulses differently than the relatively smooth three-phase output of the vehicle's generator, and that pulsing vibrates the battery's plates. That vibration helps the lead to flake off and shortens the battery's life. That is much worse on older batteries.

It is common now for fuses to blow when reconnecting a battery or when connecting jumper cables. That's due to surges from the computers' memory circuits charging up. Charge the battery at a slow rate for an hour or two, turn the charger off, then after a minute, turn on the head lights for ten seconds, then measure the battery's voltage. You should find 12.6 volts. If it's closer to 12.2 volts, it's not fully-charged yet.

Next, with the engine running, measure the voltage again. You must find between 13.75 and 14.75 volts. That proves the generator is working.