Voltage Issue HJ61

[1988hj61]

After driving around all morning, I went to start it in the afternoon and it only clicked a couple times. After poking around and checking wires, batteries and fuses, I have only been able to narrow it down to a low voltage issue. Both batteries read 12.2V when I check them at the posts, but when I check them in series, they only read 6V. They are fairly new batteries as well. Everywhere that should read 24 is currently reading 6…

I have it hooked up to a 24V charger, but that doesn’t change the output anywhere.

What am I missing?

 

[george_tlc]

12.2V is fairly discharged for an SLA battery.

I assume it is a true 24V system, i.e. the low-side battery has its negative to the engine block and body. The positive has a wire running to the negative of the high-side battery. The positive of the high-side battery is 24V relative to block/body.

Yes?

cheers,
george.

 

[1988hj61]

Solved it! The terminal was much worse than it first appeared.

 

[1988hj61]

12.2V is fairly discharged for an SLA battery.

I assume it is a true 24V system, i.e. the low-side battery has its negative to the engine block and body. The positive has a wire running to the negative of the high-side battery. The positive of the high-side battery is 24V relative to block/body.

Yes?

cheers,
george.

I think you are correct. I will swap a new battery and lug and update the thread.

 

[george_tlc]

That battery post/lug = NASTY!

I'd put those green/red felt 'washers' over the posts before putting the clamp on - they help neutralize and acid that wants to creep out of the battery and corrode the posts/clamps.

What is that 'wet' in the picture all over the battery top? Are the batteries overcharging/boiling? I'd wash them down with baking soda/water (to neutralize) if it is acid - which certainly you have nasty build up on the post.

Not sure on the schematic above, what the hell is the B-Y wire? It is shorting the low-side battery. One weird wiring schematic!! If that's a toyota schematic - they should be beaten senseless. Or are they trying to draw the 2 batteries being in parallel (schematic is still wrong)... ?

cheers,
george.

 

[1988hj61]

That battery post/lug = NASTY!

I'd put those green/red felt 'washers' over the posts before putting the clamp on - they help neutralize and acid that wants to creep out of the battery and corrode the posts/clamps.

What is that 'wet' in the picture all over the battery top? Are the batteries overcharging/boiling? I'd wash them down with baking soda/water (to neutralize) if it is acid - which certainly you have nasty build up on the post.

Not sure on the schematic above, what the hell is the B-Y wire? It is shorting the low-side battery. One weird wiring schematic!! If that's a toyota schematic - they should be beaten senseless. Or are they trying to draw the 2 batteries being in parallel (schematic is still wrong)... ?

cheers,
george.

The liquid is coke that I used to break down the corrosion. Not the most elegant solution, but it got the job done.

That is a screenshot of the factory wiring diagram. I agree, I haven’t found it to be the most easy to understand.

I have only had the truck for about 6 months and was not aware of how bad that terminal was. There was some corrosion visible, but I think the vinyl cover was hiding the true extent of the damage. They are dated 10/24, so I’m amazed it happened so fast.

I’ll grab some of those felt spacers and put them on both batteries when I get the new one installed.

 

[george_tlc]

Also, with a 24V system using 2 series connected batteries, they need to be the same type, same age, same capacity etc. One wants to replace them at the same time with a matched pair or one will overcharge and one will undercharge.

My diesel Patrol in Australia was 24V - I hated it over time (had bought it new) and eventually got fed up with the madness and spent a month replacing everything 24V with 12V (starter, alternator, bulbs, various motors (fan, wiper etc)). Was quite a task, but I'm so much happier when I visit Oz to have a 12V system with a 12V auxiliary for camping etc. There's folk that love the 24V system (or convince themselves they do), but it has very little value in such vehicles...

cheers,
george.