I Revived a 30 year old Laptop Battery - here's how I did it.....

[creepingnet]

So for those wondering if I'm still messing with NEC Versa stuff, yes I am. And I've got a new one....

So I have an original Ultralite Versa battery from 1993 - p/n OP-570-4001 - 3400 mAH, 7.2v, NiMH. I also happen to have a working V/50 and 40EC that work with this thing.

Anyway, after months of it vegging out in my V/50 and assumed dead. I decided to throw it on my McGyver'd together Battery Rejuvination rig.

What is this? It consists of a disused Skill NiCAD charger from a cordless drill I no longer have, 2 galvanized wood screws, and some copper, insulated, 2mm thick wire wrapped around. them that I just drop on the battery contacts like the tone arm of a record player to rejuvinate/charge/break dendrite shorts.

Now I've tried some other methods, I burned out the 40EC's power board (Which I fixed) with a previous method involving a Toshiba laptop charger and some alligator clips by overcharging the battery to 14vdc, and also the higher amperage I think caused some cells to blow under load.

With this method, the Skill charger is far more gentle. It only puts out around 20vdc and maybe 2 amps or less vs the 5 amps of the power supply for the Toshiba at 24vdc.

WHAT I DO TO FIX NiMH Batteries on the Versa (what I've Got Down So Far)

1.) I test the voltages on the battery to see if there is a charge, if the voltage is 3vdc+, I drain it with an old Tape Deck motor to 1vdc or less - both - contacts used.

2.) Once the battery is fully drained, I use my VOM on continunity test to see if there are any shorts, if there are, I put the battery on the Skill Charger to charge, if not, I Try the laptop itself first

3.) The Skill Charger will let me know when the dendrite shorts are gone because the LED light will get brighter as it starts to properly charge, up to full brightness when properly charging

4.) I charge the battery up into the 7-8vdc range, testing both negative terminals to make sure they are the same or within 10% close, then I toss it in the laptop and run the laptop till the battery dies.

5.) Let the laptop charge the battery, and continue the cycle to increase life.

I ran the V/50 off a single charge last night for 30 minutes, kind of amazing for a 27 year old laptop battery with the original cells installed. I'm going to experiment some more to see if I can increase the life span by draining it and then doing a full recharge using the V/50 or 40EC, and then drain down, using the laptop, and then the motor to finish it off.

Eventually I'm building a full rig around this that will make working with the batteries far less precarious.

 

[Chuck(G)]

I have a power supply I constructed with an inverter transformer a 40A bridge and a Variac. Sort of brute force, but it works when you just need to get a charge started. Were NiMH cells common in 1990? Most of the ones that I recall were NiCd.

 

[creepingnet]

Chuck(G) - I don't think so. The NEC Versa line started in 1993 with the UltraLite Versa. The earliest laptops I've seen with NiMH may have been 91' or 92'. I've had a lot of different laptops....this is sort of where I base my concensus that 92'-93' is the hotspot for NiMH.

1991 - NanTan Notebook 3500 - NiCAD (The funky one that screws into the back with thumbscrews). The battery looked like it was leaking bird poop when I opened up the casing to rig it to a printer power supply to run it (it had that weird 4 pin power connector NanTan liked to use so much)

1992 - TwinHead SlimNote II 486SL - NiMH Battery, 3 contact, no BMC. This one also had a funky 4 pin connector and no PSU, and I had a second one that was burned up.....so I gutted the dead one, and used a 36V HP Printer power supply to make a charger. You had to pick up the battery with oven mitts, but oh boy did it hold a charge. I could run that thing for at least a couple hours off one charge.

1993 - NEC Ultralite Versa - Same as the ones above. Actually I'm using the battery from that one in my V/50. It was DOA, I still have the motherboard which I'm using to learn SMD Soldering and repair with. NiMH 3400 mAH 7.2v.

1994 -Other than the Versa M/75 and Versa 40EC, I had an AT&T Safari 3151 (Samsung Notemaster 486P), also NiMH and had a working battery, and a NanTan "Duracom" and "Prostar" 9200, one monochrome, one color, both had dual 9volt NiMH Packs with 6 cells each.

1995 - NEC Versa V/50, and P/75 of course. And then there's the IBM ThinkPad 755CD I had which started life with an NiMH pack but sometime down the road they offered a Lithium Ion upgrade for it. I got about 2-3 hours out of that thing with the LiION and used to take it to work at my early I.T. jobs as a "Daily Driver" in the mid 2000's.

 

[Chuck(G)]

About 1990, Makita was bringing out their battery-powered drills. I still have a couple of the things and the stack of big 9V batteries. All are NiCd and all still hold a charge. I wonder if the 14650 Li-ion batteries will be able to show similar durability. If you let them self-discharge for too long, you have to give them a jolt before the standard chargers will accept them.