VOGONS


First post, by Kahenraz

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I have a Toshiba Portege 7000CT with a dead CMOS battery. After a lot of careful prying and disassembly, I finally located it tucked away deep inside, lodged in a small crevice bedside the internal speaker. It has also leaked terribly.

This battery is a NiMH type, not lithium, so I had to order a special replacement. It's very difficult to impossible to get an exact match that also includes the right connector, so I will often have to snip the old one off and solder it to the wire of the new battery.

When trimming back the wire, I was surprised to find that the corrosion has actually progressed quite deeply down the negative wire. I kept trimming until it was finally clear.

A bit of flux, a dab of solder, and some heatshrink, and the repair is complete. I secured the excess wire with Kapton tape and used double sided foam tape to hold the battery in place.

It was an absolute chore to get at this battery, and there would be a risk of damaging the plastic each time doing so, so I routed the battery wire into the hard drive bay, where there is plenty of extra room when using a CompactFlash adapter.

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Last edited by Kahenraz on 2022-10-28, 21:19. Edited 3 times in total.

Reply 1 of 9, by Kahenraz

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Photos of the repair.

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Reply 2 of 9, by Kahenraz

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A few more photos.

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Reply 3 of 9, by chrismeyer6

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That's a great idea to relocate the battery to the HDD area. Was there any damage from the leaking original one?

Reply 4 of 9, by Kahenraz

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There was some discoloration to the plastic, but it's only visible from the inside. It was tucked away in part of the housing, and was not near any part of the motherboard PCB.

It was so well hidden that I almost missed it entirely. I was in the process of removing the entire motherboard to flip and over to see if there was a button cell on the other side. Then I spotted this really long twisted cable that ran off into a small void, and found the battery there.

It's also somewhat interesting that they used a NiMH battery instead of a Lithium cell. There is some kind of hibernate feature in this laptop that may uses it. Or maybe it's meant to carry enough power to allow swapping the battery while hibernating. I don't think it would be capable of keeping the laptop powered to swap the battery while it's running.

Reply 5 of 9, by chrismeyer6

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That's good about the lack of damage. I had a Thinkpad that had a NiMh battery pack that was used to keep ram content when the system was put to sleep.

Reply 6 of 9, by Kahenraz

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It's not uncommon to see laptops with two batteries (three actually, of you count the runtime battery), a lithium cell for the CMOS and a second, larger NiMH battery for sleep and hibernate functions. But in this laptop there is only the NiMH, and it's much smaller than I'm used to seeing in laptops that had the pair.

Reply 7 of 9, by Kahenraz

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I couldn't locate the dead CMOS battery in a Sony laptop I'm working on. After a lot of disassembly, I finally found it, like in the Toshiba, tucked away, deep inside the frame.

This is really annoying. Also, what's with the NiMH batteries? Why were these being used instead of lithium button cells?

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Reply 8 of 9, by Kahenraz

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This one appears to have leaked as well. Luckily, the replacement I have on order has the correct connector, and I can throw this one away. The last battery I had in the Toshiba, was not the same on the replacement.

The last two photos are from the seller.

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Reply 9 of 9, by Kahenraz

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Photos of the socket. It's very corroded. Luckily, the damage occurred on a smaller PCB that can be entirely removed. This makes cleaning it a lot easier, as I can just dunk it into a dish of vinegar.

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