Finding a suitable DIMM battery replacement

[twistedsymphony]

The lithium ion rechargeable battery for memory backup needed for this naomi multi?

nope.
in-fact most DIMM board have either completely dead batteries or missing batteries.

This topic recently came up and I started looking into it again.

First of all you might be asking "WHY" you would want or need the battery pack.
Basically the battery stores the last loaded game settings and high-scores. So if you shut down and then boot back up it will go back into the last loaded game, and retain everything as if you hadn't shut down. This wont help you when you change games as all of that will get wiped out, but it's nice if you run 1 game for a while challenging yourself to get higher scores, or want to run a DIMM based setup in an arcade where it's loading the same game every time.

There are some solutions already
I know that other's like FrizzleFried have come up with a "semi-perminant" solution to the DIMM battery problem
There are also guides on how to rebuild the battery pack utilizing the protection circuit from the original battery pack.

A less DIY and More Drop-In Solution
I'm not really a fan of either of the above solutions. Ideally, I'd like a nice new Battery pack with a protection circuit already built in that at most only requires changing the connector. Searching around I found this on AdaFruit: https://www.adafruit.com/product
/354?gclid=CjwKCAjw96fkBRA2EiwAKZjFTeGE0x0A7kVFRuFYw7eupNC3krP1uVFd1CiROjt5W4PeZ77tyKg8LRoC6boQAvD_BwE



This appears to have the same type of cells as the original battery and has a built in protection circuit, however it has no thermal protection and advises limiting the charge current. I'm unsure if the original batteries have thermal protection and I have no idea what the charge current is on the DIMM boards.

If you know the answer to either of these questions or know of other dual-18650 based battery packs please post up below!

 

[twistedsymphony]

looking around a bit more I found this from Ken on KLOV:

I have built several of these. Yes just use 18650 with tabs. Provided the pcb on end of pack is good you should not have any trouble. Just for info on these, the third wire is thermal protect from pack to DIMM Bd. If DIMM Bd sees correct resistance between the black and blue wires, it allows pack to be charged when needed. If resistance drops it thinks pack is overheating, cutting charge.

I have an idea I have been throwing around but haven't tried yet. Most all two wire packs have a thermal protect built in to pcb on them. I have supposed that if a 10ohm resistor was tied between blue wire from DIMM and the black ground, DIMM would assume packs fine and allow charge. If someone wants to try this I would like to know how it goes.

 

[Psyko-M1]

looking around a bit more I found this from Ken on KLOV:

I have built several of these. Yes just use 18650 with tabs. Provided the pcb on end of pack is good you should not have any trouble. Just for info on these, the third wire is thermal protect from pack to DIMM Bd. If DIMM Bd sees correct resistance between the black and blue wires, it allows pack to be charged when needed. If resistance drops it thinks pack is overheating, cutting charge.

I have an idea I have been throwing around but haven't tried yet. Most all two wire packs have a thermal protect built in to pcb on them. I have supposed that if a 10ohm resistor was tied between blue wire from DIMM and the black ground, DIMM would assume packs fine and allow charge. If someone wants to try this I would like to know how it goes.

I've revived my NetDimm Battery with these.
https://www.amazon.com/Original-PAN...nasonic+18650&qid=1552579265&s=gateway&sr=8-6


The little Naomi battery PCB is pictured here. It was rather easy, and I just used electrical tape after soldering the batteries in.
There's a nice little plastic guide to keep it all wrapped up.
You need to be VERY CAREFUL cutting into the plastic sleeving of the old battery so you don't cut the battery or the leads going to the bottom of the pack.
Easy peasy.

Now these are for 4 of them.
I was able to score a couple for like 12 bucks.
With this drop in mod, I'm almost able to get an entire week's worth of saved games easy.

 

[tiff_lee]

Not sure what cells are inside that but you can buy higher capacity panasonic/samsung protected 18650 cells. It wouldn't look as tidy but you could just as well put a pair inside a plastic holder.

https://www.fasttech.com/products/1420/10001980/1141104-panasonic-ncr-18650b-protected-rechargeable

loads to choose from, ignore anything with 'fire' in the name they are garbage cells

https://www.fasttech.com/category/1...wfDE4Mz1Qcm90ZWN0ZWReUmVjaGFyZ2VhYmxl&sort=r&

I've only skimmed over this but that adafruit battery has the cells configured in parallel for capacity but it looks like the original pack has them in series (7.2V 1900mAh). Still even if you used 2 Panasonic NCR 18650B cells you would bump that up to 3400mAh.

Or if you wanted more capacity try looking for some decent 26650 at the expense of a bigger pack.

 

[tiff_lee]

looking around a bit more I found this from Ken on KLOV:

I have built several of these. Yes just use 18650 with tabs. Provided the pcb on end of pack is good you should not have any trouble. Just for info on these, the third wire is thermal protect from pack to DIMM Bd. If DIMM Bd sees correct resistance between the black and blue wires, it allows pack to be charged when needed. If resistance drops it thinks pack is overheating, cutting charge.

I have an idea I have been throwing around but haven't tried yet. Most all two wire packs have a thermal protect built in to pcb on them. I have supposed that if a 10ohm resistor was tied between blue wire from DIMM and the black ground, DIMM would assume packs fine and allow charge. If someone wants to try this I would like to know how it goes.

I've revived my NetDimm Battery with these.https://www.amazon.com/Original-PAN...nasonic+18650&qid=1552579265&s=gateway&sr=8-6


The little Naomi battery PCB is pictured here. It was rather easy, and I just used electrical tape after soldering the batteries in.
There's a nice little plastic guide to keep it all wrapped up.
You need to be VERY CAREFUL cutting into the plastic sleeving of the old battery so you don't cut the battery or the leads going to the bottom of the pack.
Easy peasy.

Now these are for 4 of them.
I was able to score a couple for like 12 bucks.
With this drop in mod, I'm almost able to get an entire week's worth of saved games easy.

You wrapped the cells in electrical tape? be a shame to go to all that effort and not make it look pretty!

Just google 18650 (the form factor of these cells) twin heatshrink

https://www.moddiy.com/products/PVC-Heat-Shrinkable-Tubing-(50mm-Φ32mm-Dual-18650-Battery).html

Also forgot to add as got ninja'd on first post, if you intend to reuse the original protection board then you specifically buy unprotected (regular rechargeable) 18650 cells, protected cells individually each have their own protection PCB shrink wrapped on top of the cell

Unprotected:
https://www.fasttech.com/category/1420/batteries?f=MTI1PTE4NjUwfDE4Mz1SZWNoYXJnZWFibGU&sort=r&

 

[Psyko-M1]

You wrapped the cells in electrical tape? be a shame to go to all that effort and not make it look pretty!
Just google 18650 (the form factor of these cells) twin heatshrink

https://www.moddiy.com/products/PVC-Heat-Shrinkable-Tubing-(50mm-Φ32mm-Dual-18650-Battery).html

The Netdimm, Naomi2 are all painted in metallic gunmetal with rainbow sparkles.
Don't hate, the battery is hidden under it's painted plate.

 

[tiff_lee]

No hate mate just the finishing touch to your efforts!

That looks awesome, looks like pearlescent paint! did that come out of a can?

 

[Psyko-M1]

No hate mate just the finishing touch to your efforts!

That looks awesome, looks like pearlescent paint! did that come out of a can?

We used a multi step process like pearlescent.

Krylon sells the sparkle clear coat.

 

[obcd]

To return to the original topic, basically, the battery protection circuit has 3 purposes:

1. It should protect against over charging.
2. It should protect against short circuits and limit the output currzent.
3. It should protect against deep discharging and disconnect the battery pack if the cell voltage drops below a minimum.

The dimm battery pack is a 7.2V with 2 cells in serie.

The third wire on the plug is a (1K?) NTC that protects the battery against overheating. They are easy to find and I wouldn't replace them with a normal resistor. You don't want an overheating battery in your system. (It can function as an additional protection)

Some tablet batteries would probably be a perfect replacement, if they are 7.2V and only connect with 2 wires to the tablet.

There should be another topic about using 2 18650 cells with a battery protection circuit. I even bought the needed components from PascalP but never had the time to assemble it yet.

 

[Bay78]

Hello there, I’m wanting to make a new 18650 battery pack for my NetDimm. Does anyone have a guide that has working pictures? I found a guide on Naomi forums but I guess it’s to old and the pictures have been removed. I just want to make sure I do this right considering on dangerous these batteries supposedly are. Any help would be appreciated

 

[djsheep]

Here’s an alternate solution, unless you’re using your cab for hours at a time, at least every 72 hours, the batteries won’t hold charge: http://aha-forums.com/wp/2015/08/18/dump-that-battery/


Battery replacement guide in Japanese (But the pictures are good and explain what is needed): https://bakutendo.net/blog-entry-409.html

Finally, in English, here's all the information and diagrams you need: https://wiki.arcadeotaku.com/w/Sega_Naomi_DIMM_board_and_GD-ROM

 

[nem]

I put some new 3350mAh Panasonics in mine. They last at least two weeks, not 72 hours. Admittedly, I let them charge fully.

 

[Raph_friend]

I put some new 3350mAh Panasonics in mine. They last at least two weeks, not 72 hours. Admittedly, I let them charge fully.

Link or model please?

 

[nem]

Link or model please?

NCR18650B

I did the same thing as @Hydreigon here:

Back to Ghost Squad (project)

 

[tiff_lee]

Link or model please?

NCR18650B

I did the same thing as @Hydreigon here:

Back to Ghost Squad (project)

Just to clarify it looks like he used unprotected INR18650's which I wouldn't recommend as the danger of over-discharging the cells and killing them is quite likely if you don't use your board much

 

[nem]

Just to clarify it looks like he used unprotected INR18650's which I wouldn't recommend as the danger of over-discharging the cells and killing them is quite likely if you don't use your board much

Pretty sure the original cells found in these packs are unprotected too.

CGR18650A / CGR18650H

 

[tiff_lee]

Just to clarify it looks like he used unprotected INR18650's which I wouldn't recommend as the danger of over-discharging the cells and killing them is quite likely if you don't use your board much

Pretty sure the original cells found in these packs are unprotected too.

CGR18650A / CGR18650H

Yeah not sure if that was a limitation of the tech at the time or a cost thing, I mean these things would of been on 24/7 so there was probably no concerns of over discharging the cell but take the cell voltage too low (edit:2.5V is when the protection board goes open circuit to prevent further discharge) and it can damage the cell

 

[nem]

The price difference is negligible, so better to now go for protected cells, but I wouldn't have any concerns over running unprotected ones.

 

[djsheep]

If anyone is searching for these batteries and having trouble finding them, any decent vape shop will have a variety of 18650's for sale. My go to's are the Samsung 25R or Sony VTC6.

 

[kikaso]

Sorry for bumping an old thread but how do I go about replacing the cells if I want to forgo a battery holder?

I have replacement cells but don’t know how the old cells are removed. Are the batteries soldered to the tops and bottom?

EDIT: I desoldered the charging circuit PCB but don’t know how to remove the metal tabs. Is this as easy as adding heat?