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Old 13 October 2010, 14:30   #1
craggus2000
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Amiga battery replacement

Hi,

Quick question: is the lithium battery (CR2032) + diode the preferred type of battery replacement method in the A500plus?

Many thanks
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Old 13 October 2010, 15:12   #2
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Quote:
Originally Posted by craggus2000 View Post
Hi,

Quick question: is the lithium battery (CR2032) + diode the preferred type of battery replacement method in the A500plus?

Many thanks
Your choices for the A500+ (or any other Amiga with an internal battery) is either to replace it with a modern like-for-like part (Varta make NiMH parts for the job) or you can do the lithium coin battery hack. If you go down the NiMH route, you'll still need to replace the battery again in 7-8 years or so. The coin battery should be much less likely to leak, but some folks would argue that it is a bit of a hack.

I've got Amigas with both types of replacement. An A2000 with a coin battery and an A4000 with a new NiMH type. As far as I can tell, there's no actual difference in functionality; either it keeps the time or it doesn't. ;-)
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Old 16 October 2010, 15:38   #3
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I realize the OP was talking about an A500+, but I recently purchased a couple of the CR2032 battery mods. One was intended for my A3000D which still had its original battery. Since I have never done any soldering work before, I decided to take it to a guy who used to be an authorized Commodore sales and service technician back in the day and pay him to do the work instead.

He actually steered me away from the CR2032 mod because he said the voltage would have put the machine into a "borderline logic" state. (I think that's what he said.) Here's how he explained it: The original NiCad battery was a 3.6V battery. The CR2032's are a 3V battery, so already it is arguable of whether or not the battery is supplying enough power to the circuit. But then he said the diode on the modded CR2032 battery clip actually drops the voltage another .4V to 2.6V, which makes it even more borderline on whether it can supply enough power to the clock circuit or not. He recommended instead to replace the battery with a like-for-like NiMH 3.6V battery. The added bonus of this battery is that it's newer technology and does not suffer from the memory effect that NiCads often did.

He also gave me a couple more tips regarding the battery. He told me that those batteries tend to start leaking when they are discharged. My A3000D had been unplugged and unused for a few weeks when I brought it in to him and part of why I brought it in was because I saw some leakage starting. When he saw the battery, he said it was probably in the best condition he'd ever seen for something so old. At one point in the CR2032 vs. NiMH discussions, he actually said that if I wanted to, I could just take it home, plug the machine in and let it run for several days straight, enough to properly charge the battery, and it probably would be fine for quite a while yet.

In the end, I decided to have him swap out the battery with the NiMH.
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Old 16 October 2010, 23:24   #4
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OK,

Taking in to account, with respect to what Brett has said, I have done the CR2032 mod (did it before Brett's post appeared!). Put a brand new battery in. The voltage before the diode is 2.7V and after the diode it is 2.2V . Now I booted in to Workbench (booted off 2.04 disk), set the date and time and saved it. Turned off the Amiga, and unplugged from the mains. Left it for 10 mins or so, plugged in and booted back up. The time had gone back to 1991 !
I'm assuming this is because the voltage of the battery is too low? Is there anything else I can do , short of replacing again with a NiMH? Any other model of CR battery maybe?

Otherwise I guess I will just have to change again to an NiMH!
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Old 17 October 2010, 06:40   #5
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What I have done is replaced the battery with a cordless phone batteries. I have a few inches of wire attached that allows the battery to be placed well away from the motherboard. for my A2000 i made a plastic pouch to hold the batteires for the Mobo and a 386 in the space between the plastic front bezel and the metal frame.
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Old 18 October 2010, 12:43   #6
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Got one of these on order, decided to use it in the end...
Cheaper than Farnell if any one else is interested too!

http://www.budgetbatteries.co.uk/21438/ml2032-size-lithium-3v-65mah-maxell-rechargeable-coin-button-cell-with-t25-style-pcb-tags/
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Old 18 October 2010, 13:21   #7
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Except CR2032 is rated at 235mAh, yours will go flat in about 1/4 of the time.

Try not to leave your machine off for more than half a year.
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Old 18 October 2010, 23:00   #8
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Except CR2032 is rated at 235mAh, yours will go flat in about 1/4 of the time.

Try not to leave your machine off for more than half a year.
But the ML2032 is 65mAh (is that not nearly the same as the Amiga original batteries?)
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Old 19 October 2010, 01:20   #9
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What I wrote was half jokingly, from my own calculations on the replacement of the original battery in an A4000 with a CR2032 they will last for about 10 years even if you don't take into consideration how often the machine is switched on. You shouldn't have any issues with your choice.
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Old 19 October 2010, 10:38   #10
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i use http://www.digivideo.biz/it/elettron...h_3v6_80_3.jpg
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Old 19 October 2010, 21:28   #11
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Originally Posted by Loedown View Post
What I wrote was half jokingly, from my own calculations on the replacement of the original battery in an A4000 with a CR2032 they will last for about 10 years even if you don't take into consideration how often the machine is switched on. You shouldn't have any issues with your choice.
Sorry, having an off day, missed the irony!
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Old 27 October 2010, 11:29   #12
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Got one of these on order, decided to use it in the end...
Cheaper than Farnell if any one else is interested too!

http://www.budgetbatteries.co.uk/21438/ml2032-size-lithium-3v-65mah-maxell-rechargeable-coin-button-cell-with-t25-style-pcb-tags/
Just an update on this, installed last night and all working well
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Old 27 October 2010, 14:42   #13
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if money is no object, you could have used rechargeable coin type battery, or super capacitor (not sure if its the same thing). that way no need for diode or ever(?) replacing it.
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Old 27 October 2010, 20:36   #14
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The Amiga RTC circuit is way too "power hungry" compared to modern circuits. A super-capacitor will not last more than a week with the Amiga off.
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Old 28 October 2010, 10:56   #15
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if money is no object, you could have used rechargeable coin type battery, or super capacitor (not sure if its the same thing). that way no need for diode or ever(?) replacing it.
I did use a rechargeable coin battery.... ML2032
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Old 28 October 2010, 14:45   #16
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@brett

that's why some say we should use Schottky diode. the specs for RTC chip say minimum voltage is 2,2V (IIRC) but I think it can use even lower. I never had problems with ordinary diodes, they worked for years.
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Old 28 October 2010, 23:49   #17
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@brett

that's why some say we should use Schottky diode. the specs for RTC chip say minimum voltage is 2,2V (IIRC) but I think it can use even lower. I never had problems with ordinary diodes, they worked for years.
With a standard silicon diode the theoretical voltage drop still keeps the RTC at 2.6V assuming perfect battery condition, those button cells usually slowly drift down to around 2.9 and then when they are spent quite rapidly drop towards zero. Changing the battery and resetting the clock isn't a massive task.
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Old 29 October 2010, 14:23   #18
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I have already change the original 3.6 battery on my Blizz 1230 with CR 2032 lithium added one small glass diode with low voltage drop on +,
my A1200 still working 1.5 years with out problems and time is absolutely correct.

Edit: the "Schottky diode" has the lowest voltage dropping about at 0.2v
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Old 30 October 2010, 00:36   #19
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@Anemos: the glass bulb diode is also known as Germanium diode. Most common unit is the 1N60, which have a normal voltage drop of 0.3V.

Also Germanium units are known by they current leak on reversed voltage, but on the Amiga case this current is negligible.

But on the low current circuit of Amiga RTC the drop is only around 0.15 (checked with my multimeter).

A Schottky diode will "improve" the voltage by less than 0.1V compared to a Germanium unit. But at a cost: schottky diodes tend to cost a bit...
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Old 30 October 2010, 01:11   #20
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@rkauer,i dont use germanium diode..
im sure i use "Small Signal Schottky Diode" smd type and cover is a glass small and practical for small works..
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