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Seeking advice on rebuilding GRiD Enhanced Batterypack

T

TommyTorty10

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May 28, 2025
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Hello! I'm new to the forum. I have a gridcase 1520 which came with a batterypack. I'm hoping to open up the pack and replace whatever's inside with some modern batteries, but I'm hesitant to use more force trying to open it. Prying gently at it doesn't seem to be making any progress, and I'm wondering if the plastic is welded shut or if I just need to know where to apply more force? Since I'm sure someone will suggest it, let it be known that I do have a power supply I can just run the computer directly off of.

I couldn't find any other posts or online resources about the battery pack, so if anyone knows of any guides or teardowns, feel free to share them with me. Any information regarding the batterypack is appreciated!
 
The pack is plastic welded around the seam. I had to go around it a few times with a rubber mallet on a hard surface to break it along the edge of the weld to separate it.
The larger issue we've run into is sourcing the cells. Inside is three cardboard tubes, each containing three 1.2v Ni-Cd C-cells with tabs and one thermal protection device. Because it's only two terminals on the pack it both charges and discharges through the same circuit which makes a lithium replacement complicated as you would have to develop a bi-directional charge-battery interface without having to just redesign the pack and lose the ability to keep a pack charged from the AC adapter while the system is running.
Tabbed Ni-Cd C-cells are not hard to find, however getting cells certified to their capacity (1000mAh, 2200mAh, 3000mAh....) is the hard part because either you are buying unknown from Amazon or it's a supplier who wants serious money that it becomes hard to justify. Popular Science was reporting in 1985 that a GRiD's battery pack could last "about an hour" but didn't specify in what display or drive configuration. Running an internal hard drive and a plasma screen will run you a TON of power, as opposed to a model with two floppy drives and the LCD screen.

With a lot of variables, a rebuild was tried earlier this year by another member who found that nine 1.2v cells fully charged only gave him around 14v on a pack but offered less than 15 minutes runtime. We can't tell if it was because the wrong cells were selected or the plasma screen was that much of a hog.
 
NeXT said:
The pack is plastic welded around the seam. I had to go around it a few times with a rubber mallet on a hard surface to break it along the edge of the weld to separate it.
The larger issue we've run into is sourcing the cells. Inside is three cardboard tubes, each containing three 1.2v Ni-Cd C-cells with tabs and one thermal protection device. Because it's only two terminals on the pack it both charges and discharges through the same circuit which makes a lithium replacement complicated as you would have to develop a bi-directional charge-battery interface without having to just redesign the pack and lose the ability to keep a pack charged from the AC adapter while the system is running.
Tabbed Ni-Cd C-cells are not hard to find, however getting cells certified to their capacity (1000mAh, 2200mAh, 3000mAh....) is the hard part because either you are buying unknown from Amazon or it's a supplier who wants serious money that it becomes hard to justify. Popular Science was reporting in 1985 that a GRiD's battery pack could last "about an hour" but didn't specify in what display or drive configuration. Running an internal hard drive and a plasma screen will run you a TON of power, as opposed to a model with two floppy drives and the LCD screen.

With a lot of variables, a rebuild was tried earlier this year by another member who found that nine 1.2v cells fully charged only gave him around 14v on a pack but offered less than 15 minutes runtime. We can't tell if it was because the wrong cells were selected or the plasma screen was that much of a hog.
Click to expand...
Thank you for all the info!

For the curious, I was able to successfully open the battery pack with a few gentle blows of a mallet on a chisel. I'm thinking of getting a lithium battery and a BMS for an RC car. The dimensions will be a little tight but look feasible. Some back of the envelope math assuming a constant draw of 60W and that the battery isn't lying about its capacity (I know, big assumption) works out to about 30 min of runtime. I'll report back with how things actually work out in reality when I get there.
 
The battery cartridge has 12 4/5 sub-c nicad cells, i tried to replace mine with nimh (tenergy https://www.amazon.com/Tenergy-SubC-2000mAh-Rechargeable-Batteries/dp/B084GHB6N8/) , but havent got any good results (i tried with 9 cells at first then with 12, it is hard to pack them they barely fit).
i opened it metal prying tools i use to open stuff.
now as for lithium replacement, i actually got it working with 3 unprotected flat top 18650 and this BMS https://www.amazon.com/dp/B09MLXFH81
It does recharge to full when installed in 1520 and allows it to run about 1 hour on full charge.
i have few more batteries with crusty nicad cells inside but I dont even want to bother opening them, it is just crusty toxic waste inside.
my plan is to design and 3dprint replacement cartridge and make battery contacts out of wrapped battery nickel strips welded with battery welder and put the bms and 3 18650 inside.
it could possibly also work with 3 flat pouch batteries which would possibly fit better inside battery pack.

i had much better luck recelling gridlite battery with the same nimh cells (which is the same as sony np-11 battery btw used for some betacams?).
 
I'm looking at the design and what are the odds the GRiD will tolerate 16.6 to 17v on the battery terminals?

I can see that the GRiD spec implies the rear DC barrel jack can be anything between 9 and 18v (I've seen mention for 24v but I cannot safely confirm that is a standard upper tolerance) but the battery is listed repeatedly for for 16.2v.
A three cell BCM circuit gives you 12.6v which is fine as you have tested but adding a fourth cell increases the battery capacity, it's just that this would put the battery terminals up to 16.8v while discharging and possibly higher if they are very healthy cells.

Edited: GRiD's spec for the 1500 series seems to imply that the DC-DC module for the EL/LCD and Plasma models has an upper tolerance of 20v DCdfghdsf.jpg
 
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yes, but the charging circuits outputs like 13V or something, it is not part of DC-DC board, it is before DC-DC which supplies the computer part of gridcase
the input power, battery management and so on are part of power supply before DC-DC
I am pretty sure that the battery goes at most to 12*1.2V
 
With that in mind I'm gonna crib your proof of concept and the battery control module and prototype a larger-scale pack.
The 20A 3-cell BCM you selected you can technically double the number of cells from three to six by running two sets of three in parallel. My major caution here is that this then means you cannot (and really you shouldn't ever be) mixing and matching lithium cells.

BCM.png

I'm pulling cells from a batch which after a charge and sitting for a week the best and closest reading cells are being used.
If you have ever wondered, six 18650 cells will fit *perfectly* inside a GRiD pack, with room on one end and space above, so we're on the right track!

IMG_6655.jpg

I'm placing some foam underneath the cells and at the rear end so the pack is firmly held in palce. For this prototype I don't have access to a spot welder or ribbon so I had to make do with wire. First thing of note is you MUST have ribbon spot welded to the ends. There's simply not enough space to be attaching wires, much less soldering to pre-welded tabs. I'm also using cardboard to layer the wiring which adds thickness but ultimately everything does fit inside the pack and the two halves can be glued together without a fight beyond making sure they are pressed together.

IMG_6656.jpgIMG_6657.jpgIMG_6658.jpg

Personally, after modifying a pack like this I'd put a caution sticker somewhere indicating this is now a Lithium-ion device instead of Ni-Mh/Ni-Cd. The energy density of this pack is a LOT higher than GRiD could of ever imagined and you're in for a bad day if something about the pack now fails or the terminals are shorted. I would seriously consider at least one safety fuse somewhere.
On the table with more or less charged cells I'm seeing 12.5vdc at the terminals which verifies 0xDEADBEEF's experiment and I guess should be fine.
Now be aware I have NOT tested this yet. I don't see why this will not work but I'd really like to test and see how it handles discharging and charging, presumably without bursting into flames. Unrelated work is going to keep me away from my desk for the next week or so.
 
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Good job.
It is normal practice to run multiple cells in parallel.
All right, I need to re-measure things and maybe go for 6 cell design for my replacement pack project. I have flat top cells and battery welder but I am pretty sure they didnt want to fit in the case across.
 
This is how I originally did it in 2022 but since then I changed from terrible unreliable crimps to spot welds. I have a plasma screened 1520 and I would get about 20-25 min of runtime (maybe 30+ min on low brightness and removing the hdd). You definitely want 9 cells if you are going Ni-Cad!
1750698994731.png
 
Initial life test was completed last night and here's the test conditions and the results.

Battery: 18650 @ 2200mAh, qty 6
-Cell build date: November 2015
Initial charge voltage: 12.6v DC
System: GRiDCase 1520
-286 W. FPU
-640K + 2mb
-20mb Conner Peripherals IDE hard drive (no power management)
-LCD display option W. Electroluminescent backlight (on)

Notes:
System booted and idled at a DOS prompt for two hours and twenty nine minutes before the low battery notification turned on (red LED and a beep). The laptop suffered a soft reset from a DC dropout and ultimately failed to POST at two hours and thirty six minutes, so we had five minutes of warning before the voltage went too low which is excellent because the lithium drop-off isn't so steep that it makes the warning useless.
Interestingly, either it is a fault in my system I need to look into but after about 30 minutes on battery the backlight flickered out. Some tweaking of the brightness slider and a reduced brightness would bring it back for a while but it eventually would not start up even at the lowest brightness setting until after the battery got so low the system soft rebooted, so either the EL driver circuit has a problem or it doesn't like the lower battery voltage.
After the laptop was turned off the pack was removed and the underside of the battery pack (closest to the cells internally) read approximately 91F, so the pack does get warm with use but not concerningly warm.
Likewise it occurred to me the BCM will only charge it back up to 12.6v whereas a fully charged Ni-Cd pack will do something like 13-14.2v. If the charging light on the laptop turns off above a set voltage that will mean the light will always be on as the system is running on an AC adapter. If it's current based and turns off as the charge current through the cells drops as it reaches full it might still work as I'm assuming the charge current drops off as soon as the BCM is satisfied the cells are fully charged. The next thing I need to do is sit around and watch it for a few hours as it recharges through the laptop to see how it responds, then fully cycle the pack again using whatever charge the laptop itself delivered it. Like watching paint dry.

Overall so far the initial test is very promising, increasing the endurance of the pack by 200% in reference to Popular Science's own test in the 80's however the next real test will be with an EL or plasma panel where the bar has been set at 15 minutes under rebuilt Ni-Cd. I suspect we will see about one hour of battery life however if another pack was built with 3400mAh cells it would be interesting to see what kind of results we got.
 
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