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So, I inherited this old Epson Equity LT... It's a laptop with internal Ni-Cd batteries. No battery quick disconnect, but apparently they're at least somewhat removable as the manual says that you can have them replaced at a shop (well, maybe 20 years ago you could have!). Batteries don't hold a charge at this point, but neither does it get hot like they're in danger of melting down (yet).

If it had a user serviceable battery, I'd just pull it, send it to recycling, and run the system off wall power. However, with the batteries not being user serviceable I figure there's at least a chance that they're part of the power filtering system.

Does anyone know if it's safe to run it without the batteries installed? I'd hate to spend the time removing them and potentially doing damage to their connections only to find I needed them installed... However, I would like to have them gone to avoid a potential future problem!

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    I use all my laptops with batteries removed. Never had a problem. – EL Dendo Jul 5 '17 at 22:02
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    The original Mac Portable has its battery connected in series with the power supply though, so there is definitely at least one laptop for which you cannot simply remove the ancient battery. Though a side effect is that it also won't work with a dead battery, so I guess if the laptop is currently working from wall power then you at least needn't worry about that specific pitfall. – Tommy Jul 5 '17 at 23:24
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    The battery is probably made up of Ni-Cd C or AA cells bundled together in some fashion or another so you could potentially build a new battery pack. – Ross Ridge Jul 5 '17 at 23:54
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    @RossRidge You're almost certainly right, quoting from the manual: The battery pack inside the Equity LT contains eight NiCad (nickel cadmium) batteries that power the computer.... Incidentally, the manual can be found here: files.support.epson.com/pdf/elt___/elt___u1.pdf – misha256 Jul 7 '17 at 4:12
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    Any "power filtering" role could probably be adequately taken by a big electrolytic capacitor and/or dual layer capacitor... – rackandboneman Jul 7 '17 at 9:27
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I have 3 of these laptops, and can assure you that they will run OK without the NiCd battery installed, although you may need to replace the lithium CMOS battery if that hasn't been replaced. You can get a matching CMOS battery from Amazon, but you'll need to swap the connectors. Search for ER6C 3.6v Lithium. You should find a few AA size that say they're Maxell replacements.

To open this laptop up, there are 5 screws underneath and 3 screws across the top of the back that need to be removed. Then just lift the top straight up. The batter connects to the power supply at the back.

Removing the battery requires taking out 2 screws on the bracket that holds it in place and then pulling the battery out. It may be held in place by some tape. The screw nearest the PS doesn't need to be completely removed as the hole is just partial. It's a little hard to hold on to that one and it might slip into the PS if you take it all the way out.

If you are interested in a replacement battery, I would be happy to build one for a fellow LT owner for the cost of the parts and shipping. If you want to build one yourself, I'll dig up the part number for the connector for you. The battery consists only of 8 cells and 4 wires, so not too hard to assemble.

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    Welcome to Retrocomputing Stack Exchange. Please read the tour. Thanks for sharing your detailed, specific first-hand experience. – wizzwizz4 Sep 6 '17 at 6:28
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    Perfect, thanks for the information! I appreciate the offer to build the battery, but in this case (very infrequently used and always on reliable wall power) I'm just removing the batteries (had it done in mere minutes using your instructions after getting home)! They appeared to still be in perfect shape, but I don't want to chance it... :-) – Brian Knoblauch Sep 6 '17 at 21:52
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    Great! The LT was my first personal computer, so it makes me happy to see any that are still running. I've never seen the batteries leak in any of them. The only NiCd cells that I've ever seen leak were ones I over charged and melted on a quick charger. – John Sep 7 '17 at 0:48
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Ni-Cd cells like the ones used in the last century have one strong advantage over the Li-based battery cells we use today: They simply die silently.

As long as they are not leaking and contaminate the inwards of your computer, I see no reason why you shouldn't just go on using that computer.

Other than that, quite a lot of Ni-Cd battery packs have been built from standard-off-the-shelf 1.2V AA or AAA cells and are thus relatively easy to replace.

  • i often hear "omg, don't simply replace accu packs, that's dangerous!" ... is that only a trial to keep me from replacing them myself, instead of paying them to do it for me ? – Tommylee2k Jul 7 '17 at 8:13
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    Ni-Cd batteries have one specific area where they could possible be dangerous - That is, when you are significantly over-charging them they might produce excessive heat. As long as the charging circuit is laid out for the same type of batteries (and there is basically only one in Ni-Cd), there shouldn't be a problem. This is a bit different to modern Li-based batteries, that can react quite a bit more violently. – tofro Jul 7 '17 at 8:52
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The battery probably isn't a part of the power-filtering system. If you aren't sure if you'll be able to use the laptop without it, just disassemble the laptop, remove the battery and power on the computer. If it works, then there's nothing to be worried about. If it doesn't, firstly check if you have connected everything properly; If everything seems OK, then insert the battery again and check if it changes anything - if it will work then but not without the battery, just leave it inside.

Before sending the battery to the recycling center, i would suggest to try to replace the cells - you may make it work like a new one! Firstly, if you don't feel confident in electronics, don't do it - this process will include desoldering existing cells and soldering new ones, which is kinda dangerous if you don't take precautions, and may be hard for a beginner.

Before I even start on how to do it, i must write that i give no warranty that you won't destroy your laptop/battery and/or injure yourself. Be careful.

You'll need:

  1. A clean desk
  2. Lots of time, patience, and some soldering skills
  3. Flat and/or phillips screwdriver
  4. Soldering iron

First, if your battery is put together using screws, unscrew them. If you don't see any, then carefully insert your flat screwdriver in the slit and pry the battery open. Be patient with this step, try avoid damaging the plastic. Second step is to determine what cells your battery uses. They should have a numer like 18650 on them (but they probably won't be random 18650s - 18650s are LiIon, not NiCd). Search for that number on a site like Amazon or Ebay; If you'll get any results, buy an exact number of cells that you already have in your old battery; New cells can be rated for a little bit higher or lower voltage (~±1V is still OK, but anything higher/lower than that won't be good for your laptop), and can have a higher or lower Wh/Ah rating - this one will only change how much uptime will your laptop have on the battery.

When the cells will arrive, desolder the old ones from battery circuitry (from the Printed Circuit Board, or PCB), and solder the new ones exactly like the old ones were soldered. Don't forget to check the polarity of all batteries you solder - you should connect + from one cell to - from another cell, or if some of the cells are connected in parallel way in the original, then + from first cell to + from the second cell, and - from the first cell to - from the second cell (this way two or more cells will work as 1 bigger one). Don't forget to double-check if all cells are connected correctly before soldering two leads to the PCB.

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