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Replacing battery in a Haas control?


Apr 1, 2009
Blaine, MN
I appreciate the input, keep in mind, they were only tied together for the replacement process because I wasn't sure whether I'd loose anything while replacing the battery, then the jumper was removed.

Donkey Hotey

Dec 22, 2007
Old thread but, this is relevant to all owners of these Vector Drive era, pre 2008 machines.

That's because one battery backs up the control memory and the other battery is for the Dallas DS1286 non-volatile RAM and Clock module, next to the battery.

This is not how they are wired, unfortunately. I believe the dual battery boards are the ones with more memory. From looking at similar vintage boards on eBay, it seems the boards with fewer memory chips on the board have a single battery. When all of the chip spots are populated, the machine also has twin batteries.

It's anecdotal but, I had originally connected only one of the battery pads (the right) to an external backup and it lost things on restart. I had to jumper the pads together and connect them to an external pack to make them work.

Note: there is a known problem where if you use the Haas external battery pack on our older machines, you continue to get a Low Battery alarm. Soldering the wires directly to one of the pads and installing a jumper from one battery pad to the remaining positive location makes that alarm go away.

The Dallas DS1286 Watchdog chip has no external pin for Vbat. That's our very problem. The pin to feed battery voltage is folded upward and a button cell is soldered on top of the chip. Then the entire top surface is potted in compound and a plastic cap put over it, as we see the final product. The chip is supposed to be stand-alone and when the battery dies, it dies. They wanted to sell chips. It seems plenty of computers and other industrial devices used these same chips back then. The good news is this means it's fixable.

Symptoms: the Haas CNC Real Time Clock reads January 26, 2066 (06-26-2066 20:66:00). All errors, file save dates and times, etc, will be stored that way. You can reset the clock but, as soon as you cycle power, it resets to the future.

The chip was very clearly intended to be replaceable since it's next to the batteries, in a dip socket and zip tied to the board. No reason to put it in a socket if it wasn't designed to be removable. With that said, something got lost between the engineer who designed the board and the service people who had to know to change these chips along with the batteries.

Those clock modules have a lithium battery in them and an external Vbat input. The battery not connected to the "ext bat" connector is for the Dallas NV RAM module, which then uses its internal lithium battery as a backup battery when you replace the one on the board, so no external battery is needed while that is replaced.

Both of my original batteries (fall 2004) had a measured 3.0V after nineteen years. I waited and waited and waited for a low battery alarm that never came. Had I not already planned to do the external battery mod and already disassembled everything, I would have left them in there.

You risk causing harm to the control by connecting both batteries in parallel. The SRAM in the control consumes far more current than the NV RAM module, which drains the batteries faster.

Disagree. See above. I actually believe the clock consumes more power. The three machines I had at work did not use the DS1286 chip and relied on the board battery to run the clock. All three died in their first five years. They were also 16 MB machines (2010).

There are a number of hacks elsewhere on the web that show cutting through the plastic case of the DS1286, clipping the battery lead, soldering a jumper wire to the Vbat pin and powering the chip externally.

There is also a person on eBay who sells an adapter board to replace the DS1286. The 1286 was part of a family of time keeping chips. One of the smaller versions of the same chip is the DS1284. He makes an adapter board that fits the socket of our DS1286. It also includes the holder for an external button cell and an external time crystal. It's the identical function in a different shape.

I have one of his kits on the way to fix my VF2. I'm about to try the grind and solder fix on a friend's 2003 Mini Mill. We're going to wire his to the now-external battery kit so the clock and both banks of memory will be retained by easy-to-service cells. I'm going to also hard-wire the new kit to the 3.1V lines. The whole intent of moving to external batteries is the freedom to replace them every few years. If the clock burns them a little faster, so be it.

More to come...

Perry Harrington

Oct 7, 2006
Klamath Falls, Oregon
This thread is necro, I haven't owned this machine in ~12 years? That said, the DS1286 datasheet shows an external battery input, this is what differentiates it from the DS1284: https://www.analog.com/media/en/technical-documentation/data-sheets/ds1284-ds1286.pdf

I have a Fadal now, and the SRAM chips draw something on the order of 2 microamps each, a single battery will power 4 of them for 30 years, without drain. This is referring to Tadiran Lithium cells, which seem to be the best quality IMO. I've seen some controls that drain the C sized cells in 5 years, that must be owed to bad design on the enable lines or not isolating the memory power properly. The Fadal isolation design works well. 4 chips and battery is still above 3.6v after 30 years. According to the datasheet, I should be getting ~75k hours out of 1 battery and 16 chips, this might be accurate. Divide that load by 4 and we are literally in uncharted territory. On their chart, half the load results in an order of magnitude greater longevity.

Anyway, I guess the bottom line is:
  • Replace the replaceable batteries regularly with high quality units
  • Tap the ext battery input of the DS1286, or replace it with a DS1284 regularly

Donkey Hotey

Dec 22, 2007
This thread is necro, I haven't owned this machine in ~12 years?

I fully understand. :D

I added it here with all the keywords I could think of because as I was researching this around the web, I couldn't come up with any results. I ended up having to start looking up chip numbers from the main board in hopes of finding the clock. I tried that one early because the zip tie and placement near the batteries made it suspect.

That said, the DS1286 datasheet shows an external battery input, this is what differentiates it from the DS1284: https://www.analog.com/media/en/technical-documentation/data-sheets/ds1284-ds1286.pdf

Peace! A little more info though: The data sheet shows the battery input pin but, if you look at the actual chip, the pins are absent. That's because they literally folded those unused pins upward and over the back of the chip. So you can't externally access the battery pin without grinding through the epoxy encapsulation.

I'll post pictures after I do the installations. I hate to sound like I'm spamming but, the guy who designed the little circuit board and sells them assembled on eBay is a savior. It's very simple but, necessary to do the job cleanly.

The DS1284 he uses is a PLCC package (allegedly the only version still commonly available). The DS1286 is wider EDIP and the other version of 1284 is a standard DIP (and no longer supported).

You brought up a good point though: could Haas have connected the Vbat pin on the socket to one of the battery lines and it's just not connected due to the pin missing on the chip? Something worth checking. Thanks for bringing that up. This aftermarket fix might get battery from the Haas board anyway.

Donkey Hotey

Dec 22, 2007
Haas battery and Real Time Clock replacement

Gonna put everything I've learned in this post so people in the future don't have to sift through everything. I believe this applies to the Haas controls from the beginning of the vector-drive and brushless motor era: around 1997 to 2006?

Batteries: one or two?

The difference here seems to be the amount of memory your board has. I have not verified this. My personal sample size is two machines, plus what I can make out in pictures on eBay processor board listings. My 16 MB board from late 2004 has 32 RAM chips soldered to it. It has two backup batteries. I can confirm that by the original design, the two batteries are not connected together so if power is not supplied to BOTH pads, some of the memory will be lost.

A friend's Mini Mill from first quarter 2005 is only 1 MB in the form of two chips on the board. It had pads for up to 16 chips and I believe this is the same board up to 8 MB. That board only has provision for a single battery.

Remote Battery

Haas makes a very nice and easy to purchase remote battery that can be installed outside the board stack. Once installed, it can be serviced without future disassembly. It plugs to the EXT BAT pins above the original batteries. Installation involves plugging in the external pack, clipping the zip ties on the original battery(ies) and then clipping the soldered battery leads from the board.

Haas has a known issue against this pack. On these pre 15" LCD machines: a Low Battery Alarm will remain after installation. The only way this is possible is the board is checking to see if power is coming from the EXT BAT pins vs the battery pads. Haas may tell you the pack will cause this error and they can't fix it, though it will function fine.

To fix the error: clip the wires off the end of the battery lead and hard wire to the board. If you have a single battery board, it's two solder joints.

If you have a double-battery board, you need to add a jumper between the + Positive pads to provide 3V to both banks of memory.

Obviously, all of this should be done with 3V applied at the EXT BAT pins or all the control settings and parameters will be lost.

A Cheaper Battery Alternative

$95 too steep for a couple of external batteries? Head on over to Digikey and order a Keystone Electronics 1120 dual battery socket. At the time of this writing, it will set you back less than $5. Its a plastic case and and does not need to be mounted to a circuit board. It has solder tabs and can be connected any way necessary.

I use 3M double stick auto body adhesive tape to mount this case. I mount them either above the DC power supply at the top of the back wall of the cabinet, or on the left interior side wall. For security, you may opt to wrap a zip tie around the installed batteries. I did this to a friend's machine because it's about to travel 800 miles to his new home. I have now done four machines this way.

For our application, we want two cells, wired parallel. That way we can change one battery at a time and not risk losing data. Solder leads from Positive to Positive and Negative to Negative (shown below). Finally, solder 12-18" of wire to reach the pads on the processor board.

The batteries are available from multiple brands, though Digikey sells the BR2/3A cells that likely came in your machine for $5.10 each. Except for wire and solder, this entire option should cost around $20 shipped.

My Clock has a Bogus Time and Date

This is how I found this thread: I'll call it the Back to the Future bug. My Mocon had an issue and I had to dump all the alarms to floppy to review them. I discovered that all the errors for quite some time, had been time-stamped 06-26-2066 at 26:66:00. Replacing the battery(ies) did not fix this. If I reset the clock, it would revert back to 06-26-2066 after restart.
As discussed up-thread, the problem is right next to the batteries. There is a real time clock and calendar chip, in a socket and held by a zip tie. It's the Dallas Watchdog DS1286 real time clock. The chip has its own battery inside the shell. The battery had an expected life of ten years. After that, you were supposed to replace this chip. Unfortunately the chip has not been supported in this form since about 2008. Many computers, industrial machines and pieces of test equipment used this chip and method for time. Lots of related videos on YouTube from these other computers and equipment.

If you poke around the web, there are procedures for using a dremel to grind through the side of the chip's case, gain access to the battery leads, where you then clip one of the leads and solder external jumpers to connect an external battery. This is possible. I didn't do that, though you are more than welcome to look elsewhere for the details.

I found a seller on eBay who has a small side gig making replacements for the DS1286 chip. He uses the surface mount version of the same chip. He has breakout boards made that adapt the pins to fit the form of the 1286 and allow it to plug directly into our processor board. It features a very large, external battery. The battery is not removable, though I suppose in 10-15 years, you could desolder and replace it. You could optionally clip the battery off the board and wire it over to the same 3V pads as the rest of the machine's memory. I opted to install it as supplied since I can now get to the main board and reassemble it in less than an hour.
To swap in this replacement chip: clip the zip tie around the old DS1286 chip. Gently pull on the chip and it will come out of the original DIP socket. Carefully align the pins of the new board, paying attention to the position of the #1 Pin (should be at the upper left corner).

He sells this kit for $50. I have no affiliation, other than it fit nicely and avoided the kludge of dremel and solder blobs on the side of the old chip. You can find it on eBay by searching for: Tektronix ds1286

I have forwarded the relevant information to him and he may soon be selling these under the Haas keywords as well. I could have used all of this information two months ago. I hope recording it here will help others.
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