Announcement

Collapse

Forum Rules and Etiquette

Our mission ...

This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.


Rule 1: Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.


Rule 2: Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.



Rule 3: Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.


Rule 4: "PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.


Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Rule 5: Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.


Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.


New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.


Other suggestions
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
See more
See less

3.6v battery on 286 motherboard

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    3.6v battery on 286 motherboard

    I have a 286 Motherboard with a dying 3.6v battery soldered to it. I want to replace it with one of these It's a LIR 2032 (Lithium Ion Rechargable) The holder for it is a perfect fit on the motherboard. My concern is the charging voltage. With the Motherboard powered up, the voltage across the existing dying battery is 4.0 volts(it drops to 3.0 volts after the power is off for a while and the clock loses time dramaticaly). The specs for the LIR2032 says charge voltage is 4.2 volts.
    1)Will it charge at the slightly lower voltage?
    2)Will the battery overheat if the charge doesn't stop when it's fully charged?
    3)I wonder if it will hold its charge long enough to power the Clock and CMOS setup memory if the machine is left off for 2 or more months?

    Thanks in advance

    Greg
    Last edited by ibmapc; February 6, 2013, 10:07 PM.

    #2
    I don't think Li-ion or any other lithium based rechargeable battery is a good replacement for NiCad batteries that were used on older AT motherboards. Lithium batteries usually require special charging controller, this to make sure battery is not overcharged (and as result overheated and destroyed).

    I would suggest using another NiCad or NiMH battery instead. I think small cordless phone battery is a better replacement.

    Comment


      #3
      Yep, That's what I was afraid of. Can you suggest a battery and/or source for this?

      EDIT
      OK, I found this. The spec say's it's not rechargeable, but I question that. I've never seen a NiCD that wasn't rechargeable. Anyone have an opinion on this?
      Last edited by ibmapc; February 6, 2013, 10:54 PM.

      Comment


        #4
        Originally posted by ibmapc View Post
        Yep, That's what I was afraid of. Can you suggest a battery and/or source for this?
        How about this battery? It is pretty much the same type as used on older AT clones.

        Comment


          #5
          I personally wouldn't bother with replacing one of the old rechargeable batteries as it'll just end up dead\leaking later anyways. If you have a battery header you can check to see if there's any voltage on it, and if not then just connect a more common battery to it, such as a CR2032 battery (solder a cable to a holder) or even just AA batteries.

          Comment


            #6
            Does your motherboard have a 4-pin header for attaching an external battery? If it does, I'd just go for 4 x AA alkalines in a battery holder and get the %^$^# battery off the PCB before it leaks and does some real damage. But if you've got to get a rechargeable battery, just get a cordless phone pack and wire it in. Radio Shack has a pile of different ones--or you can get one cheap from China on eBay. They're insanely cheap.
            Reach me: vcfblackhole _at_ protonmail dot com.

            Comment


              #7
              I don't think CR2032 will do a good job. CR2032's voltage is only 3V (vs. expected 3.6V) could be too low - MC146818A RTC minimal operating voltage is 3V. Other than that the charging current will be applied to a non-rechargeable (and pretty small) CR2032 battery. Which is not a good thing, as it could cause the battery to overheat, and so on...

              On the other hand 4 x AA will provide about 6V... way too much.

              The rechargeable RTC battery is usually connected through a diode and a resistor to VCC (+5V). Diode prevents battery discharge through other than RTC components, and resistor limits the charging current. With 6V (or any greater than ~ 4.4V) battery RTC will be always powered by the battery, even then the computer is ON. Probably it is not a very bad thing, since the capacity of the AA alkaline batteries is enough to keep the RTC running for years. But I would use 3 x AA batteries instead.
              Attached Files
              Last edited by sergey; February 7, 2013, 09:31 AM.

              Comment


                #8
                These old systems usually are fairly lenient on the battery voltage, you can get away with anything from 2.5V-6V really. I have my Compaq Prolinea 4/33, designed for a 4.5V battery brick, running just fine off a CR2032, keeps time and settings.

                Comment


                  #9
                  I soldered a CR2032 to the olld batter ypads with a diode on the + side to prevent the charging circuit from killing the cell.
                  [Need something to waste time on? Click here to visit my YouTube channel CelGenStudios]
                  --------------------------------------------------------------------------------------------
                  [No time for videos? Click here to visit my Twitter feed @CelGenStudios]

                  = Excellent space heater

                  Comment


                    #10
                    Another vote for 3x AAA battery holder, series diode and leads. Dead easy and avoids the leaking NiCd issue. I've done the same with my fruit machine too as it happens, as well because (in both cases) the likely run time will be insufficient to keep the rechargable actually charged.

                    Comment


                      #11
                      Originally posted by sergey View Post
                      IOn the other hand 4 x AA will provide about 6V... way too much.
                      You're forgetting at least 2 diode drops in the backup battery circuit (usually an NPN transistor). In fact, the 4xAA was packaged (with 4 pin connector) with many generic cases of the time. I still have a number of systems that use that 4xAA setup. The batter holder was packaged with a square of double-stick hoam tape for attachment inside the case.

                      Alkaline cells can have a very long life (years) in a setup like this. On my PC 6300, I replaced the rechargeable with a CR2032 and a schottky diode and it works fine, but IIRC, the Oki RTC chip used there is rated down to 2.2V.

                      The problem with NiCd and NiMH cells is that they do self-discharge. On a rarely-used system, this can be a problem.
                      Reach me: vcfblackhole _at_ protonmail dot com.

                      Comment


                        #12
                        Originally posted by Chuck(G) View Post
                        ...On my PC 6300, I replaced the rechargeable with a CR2032 and a schottky diode and it works fine, but IIRC, the Oki RTC chip used there is rated down to 2.2V.
                        ...
                        So with the diode, your voltage drops to about 2.3 volts. I don't know what the minimum voltage for my RTC is.
                        THIS is my motherboard. It looks like JP17 is the external battery header. I'll have to figure out the polarity with my ohm meter.

                        Comment


                          #13
                          Originally posted by Chuck(G) View Post
                          You're forgetting at least 2 diode drops in the backup battery circuit (usually an NPN transistor). In fact, the 4xAA was packaged (with 4 pin connector) with many generic cases of the time....
                          Should I connect 4AA's or 3AA's to the JP17 on THIS motherboard. JP17 is a four pin header with one pin removed for external battery. Note that the original battery is only 3.6 volts. I figured out the polarity with my volt/ohm meter and there is at least one diode in the circuit so that it won't attempt to charge the external battery when the power is on. So the volts will drop about .7v per diode right? So if there are two diodes the 4AA battery will drop to about 4.6 volts. But if there is only one diode it will drop to about 5.3 volts and that has me worried that I might damage something.

                          Comment


                            #14
                            The photo [here] shows the typical situation.

                            RTC chip

                            The RTC chip (built into a chipset on later machines) that either battery supplies is designed for a wide range of voltage.
                            Different chip types have different ranges.

                            Internal battery

                            3.6v NiCad (or a 3.6V NiMH).
                            The charging circuitry is designed for the charging requirements of a 3.6v NiCad.
                            Substituting with something else that is not compatible may damage the battery due to improper charging.
                            In this application, NiMH can be used in place of NiCad.

                            External battery connector

                            Your machine is a 286.
                            A 6V battery is not going to be a problem.

                            Comment


                              #15
                              Originally posted by modem7 View Post
                              External battery connector

                              Your machine is a 286.
                              A 6V battery is not going to be a problem.
                              Thanks Modem7 4AA's it is.

                              Comment

                              Working...
                              X