batteries full, acts like dead

[blueman8898]

Just drove my new old bus 350 miles to its new home. Eager to dig in, turning the key results in quickly fading dashlights, and solenoid sounds. Dead battery, obviously, but but the batteries are fully charged. Any ideas?

[Rwnielsen]

I would first check all of your battery connections, both ends. Sometimes you can get a good voltage reading through a loose connection but it will fail with a load.
Just an idea...

[HamSkoolie]

Ditto on checking connections at both ends.
Also check that the solenoid that's clicking is actually putting power through to the starter. Buses can have a bunch of solenoids that activate with the key but only one sends power to the starter solenoid.



It will help forum members help you if you put your rig information into your profile. Type of bus, brand, engine, trans, etc.

[rossvtaylor]

Originally Posted by blueman8898

Dead battery, obviously, but but the batteries are fully charged. Any ideas?

As others mentioned, you should definitely check the connections. But I would also suggest that you load test the batteries, or have them load tested at an auto parts store.

https://www.youtube.com/watch?v=ystmn3ly61Q

[Booyah45828]

Like ross said, load test the batteries. They can read full voltage indicating they're charged 100%, but have so little capacity that it drops like a fly with any load placed on it.

Follow that up with checking the connections are tight and corrosion free, and then a voltage drop test of the power and ground circuits to check cable health. If all of that checks out, then you can condemn the starter/solenoid.

[Rucker]

Originally Posted by Rwnielsen

I would first check all of your battery connections, both ends. Sometimes you can get a good voltage reading through a loose connection but it will fail with a load.
Just an idea...

Most likely battery connections are corroded and bad. That's a good first thing to do, clean the terminal connectors, and if necessary, replace them.

How old are the batteries? That's another good place to start, to rule out any issues.

[rossvtaylor]

Originally Posted by Booyah45828

Like ross said, load test the batteries. They can read full voltage indicating they're charged 100%, but have so little capacity that it drops like a fly with any load placed on it.

Exactly! It wouldn't be incorrect to change the title of this thread to, "Batteries dead, act like full." It's a common thing.

And all the "check the connections" comments are right on track, even if you can measure proper voltage on both sides (without a load). As a good friend used to say, "you can carry voltage through a hair, but not current." So a corroded/bad connection can show the same voltage on both sides, until you apply a load. I like the Load Pro leads for checking these kinds of things.

https://www.youtube.com/watch?v=k34fPKeO0LM&t=28s