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AIY (Assemble It Yourself) Li-Ion battery pack for FR-5/7/7x/8x

pentaprism

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Hello all
Stu here
I've Just joined the forum and see we have a few DIY battery enthusiasts here.
Glad to meet and to see I'm not the only one who likes to tinker.
I hope you don't mind me trying to use your experience...
I have a question about the Roland FR7 battery I hope one of you can answer...

My original battery still works ok for 2 hours or more so I don't want to mutilate it yet but would like to build a copy before I have to replace it.
I would like to stay with NiMH.

There is a 3 wire connection from the battery pack to the instrument.
Does anyone know what is inside the pack apart from the NiMH batteries?

Pentaprism mentions a 10k thermistor, would that be all (and how is it wired) or is there a more complex circuit?
Perhaps one of you can help me out here.

Best wishes to all
Stuart
Hello Stuart,

Please read this thread: Roland FR-8X Battery Options

Note that the thread refers to other threads.

My post (#8 in the thread) has a photo of an AA battery pack with the said 10K thermistor. I've never opened the original Roland battery pack, but my guess is that there is no "more complex circuit."

This article is helpful. There is a figure showing the connections: NiCd and NiMH Pack Design.

I once used this exact item: NiMH Rechargeable Battery: 24V 2200 mAh (2x10S/S, MH-AA2200B). I later gave it to a friend for his FR-7x.

Note that I didn't use a thermistor in the Li-Ion battery pack. The Li-Ion charger has only 2 wires and thus the thermistor would be useless to it. I did put in a thermal protector as a precaution measure.

Edited to add:

I just looked at Custom NiMH Battery Pack: 24V 4500mAh (108Wh, 20x4/3AF, HR-4/3FAU, Sanyo) and believe that it can be used as the direct replacement. Note the terminal specs:

PR-CU-R629-V1​
4" 22AWG wires with Molex connector and 10K NTC (see notes)​
Pin 1 = 10K, Pin 2 = +, Pin 3 = -, Pin 4 = Not use.​

which is the same as the Roland battery pack. Also, I believe the Roland battery pack uses Sanyo battery cells, not Sony.
 
Last edited:

Keymn

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I just received enough materials to assemble a Li-Ion battery pack (the prices below include tax + shipping):

spot welder - $66
I plan to rebuild a bunch of battery packs for my power tools. Instead of buying batteries with tab (thus limiting the sources), I can just buy flat top battery cells and add the tab myself​
batteries - 8 cells - $42
need 7, but bought 1 extra just in case....​
charger - $10
don't want to use the NiCad-NiMH chargers I currently have.​

battery protection board - $7
connectors - $11
thermal protector (metal, 5A, 70 degrees C) - $10

I'm still waiting for the delivery of the heat shrink tube - $8.

Instead, I could buy these:

Custom NiMH Battery Pack: 24V 4500mAh (108Wh, 20x4/3AF, Sanyo) - $185
Thermistor - $2

Or have one built by batteryspace.com, probably about $200. That would be still $50 less than a "used, very good" battery pack from Amazon Warehouse.

But to me, putting the battery pack together is most of the fun.

Wish me luck.
That spot welder seems nice to have with this project. Makes a good connection…
 

oldbayan

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You get what you pay for! I would not use an "economy" solution on a fine electronic instrument worth thousands of Euros/Dollars/whatever, but that's just me. :cool:
 

JIM D.

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Not only you get what you pay for but much more --


 

oldbayan

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Not only you get what you pay for but much more --



I think these should not even be labeled as a "battery" because they are capacitors! Like most rechargeable cells.

A few weeks ago we had to check the serial number of my wife's laptop computer, which is located under the battery; when trying to remove it, we noticed that it had swollen and was very hot! It was good timing, it stayed hot for hours after we took it off.

We now start seeing Lithium-Ion replacements for vehicles and marine application. The trouble is, a vehicle's charging system is designed for lead-acid batteries. Even if the manufacturer says they are safe, I would not spend $1000 on a "battery" just because it is supposed to outlast a regular $200 lead-acid battery.
 

donn

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I think these should not even be labeled as a "battery" because they are capacitors! Like most rechargeable cells.

There is a lithium-ion capacitor -
A lithium-ion capacitor is a hybrid electrochemical energy storage device which combines the intercalation mechanism of a lithium-ion battery anode with the double-layer mechanism of the cathode of an electric double-layer capacitor (EDLC). The combination of a negative battery-type LTO electrode and a positive capacitor type activated carbon (AC) resulted in an energy density of ca. 20 Wh/kg which is about 4–5 times that of a standard Electric Double Layer Capacitor (EDLC). The power density, however, has been shown to match that of EDLCs, as it is able to completely discharge in seconds.

It's news to me if what we buy as lithium-ion batteries are in any way more like capacitors. Relative to common "alkaline" etc. batteries, the irritating thing is that the different chemistries come with their own characteristic voltage, so may not be interchangeable for devices that have a narrow voltage requirement. A flashlight can run on anything, but for example we have a "trail camera" that won't run on lithium cobalt cells. A common lithium cobalt "9 volt" battery's nominal charge is 7.4V (so naturally "common" is relative - rechargeable 9V are more likely NiMH.)
 

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