A7000+ battery

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KarateEd
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A7000+ battery

Post by KarateEd » Thu May 30, 2019 2:24 am

Hi Folks,

Can someone tell me if I can use the 3.6 Ni-MH battery in my A7000+....? Also, I'm assuming it would be best to locate the battery off the motherboard to avoid nasty stuff from happening.

I think I know why it won't hold the CMOS....LOL.
Battery Location.png
There are 3 holes, I'm assuming the 2 are the positives and the other the negative though it's not marked well that way.
3.6-battery.png
I think I used this in my A3010. Don't see why it wouldn't work as well in the A7000+.....also, is that location also charging the battery?
Ed...... :-)

3 working Beebs, 1 RetroClinic Master, 1 normal Master, 1 A3010, 1 Pi2 RISC OS, 2 broken Beeb Motherboards, 1 Omnibus A7000+ server, 1 A7000+ Desktop, 1 PET, 1 C64, 1 C128, 1 Amiga 500 and 1 Roamer.

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Re: A7000+ battery

Post by mattdy4 » Thu May 30, 2019 7:48 am

Yeah battery will be fine. As you say positive any of the top two and negative the one on it's own. I use 2xAA holder on leads to keep off the board and easier to replace but the mempacs always look cleaner to me!

The 8583 has a wide tolerance (from 1v to 6v I believe)

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Re: A7000+ battery

Post by DutchAcorn » Thu May 30, 2019 9:14 am

The battery is fine but you will essentially be installing a new time bomb in your A7000 if you solder it directly on the MB. It will start to leak at some point in the future.

Best keep it well away from the MB...
Paul

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1024MAK
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Re: A7000+ battery

Post by 1024MAK » Thu May 30, 2019 10:04 am

As said above, the two PCB pads (holes) near the BT1 / + labelling are the battery positive connections. They are linked by a PCB track. So if mounting the battery off the board, you can use either for your wire.

The PCB pad (hole) just above the capacitor C13, is the battery negative connection.

Acorn used a single cell (1.2V), but the chip used is happy with a two cell (2 x 1.2V = 2.4V) or a three cell battery (3 x 1.2V = 3.6V). The battery you show in your post is a 3.6V three cell type and will be fine.

There are advantages and disadvantages to using a different voltage battery. A 3.6V type will retain the time and settings for longer (assuming the Ah capacity is the same), but takes longer to recharge. On first use, or after a long period of not being used, run for at least 24 hours to recharge (does not have to be continuous use, so could be 6 hours per day over four days).

If using AAA or AA cells, you should use a type that has a low self discharge (long shelf life), not the normal consumer grade.

It is not recommended to use a battery with a higher voltage, as that would mess up the charging current and the chips switch-over from normal power mode to low power “standby” mode.

Mark

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Re: A7000+ battery

Post by philpem » Thu May 30, 2019 2:05 pm

As an aside, the chip will also work quite happily with a CR2032 or similar lithium coin cell in a holder, but you'll need to add a series diode (e.g. 1N4148) to prevent it from being charged. They're essentially leakproof and easy to change.

I've tried supercapacitors too -- sadly with little success. The CMOS chip (or something around it) draws too much power.

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Re: A7000+ battery

Post by KarateEd » Thu May 30, 2019 5:37 pm

Thanks all for your replies.

I will be putting this battery somewhere in a 'safe' non-threatening location with extender wires to ensure when it does go, it won't destroy anything on the machine.

It's likely that I won't be alive by the time it does that anyway but I want to ensure the future for someone else.
Ed...... :-)

3 working Beebs, 1 RetroClinic Master, 1 normal Master, 1 A3010, 1 Pi2 RISC OS, 2 broken Beeb Motherboards, 1 Omnibus A7000+ server, 1 A7000+ Desktop, 1 PET, 1 C64, 1 C128, 1 Amiga 500 and 1 Roamer.

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Re: A7000+ battery

Post by 1024MAK » Thu May 30, 2019 11:25 pm

philpem wrote:
Thu May 30, 2019 2:05 pm
As an aside, the chip will also work quite happily with a CR2032 or similar lithium coin cell in a holder, but you'll need to add a series diode (e.g. 1N4148) to prevent it from being charged. They're essentially leakproof and easy to change.
You also need a suitable resistor in series with the diode, to limit the fault current in the event that the diode fails short circuit (if a diode is going to fail, it is most likely it will go short circuit).

Mark

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Re: A7000+ battery

Post by 1024MAK » Thu May 30, 2019 11:30 pm

KarateEd wrote:
Thu May 30, 2019 5:37 pm
Thanks all for your replies.

I will be putting this battery somewhere in a 'safe' non-threatening location with extender wires to ensure when it does go, it won't destroy anything on the machine.

It's likely that I won't be alive by the time it does that anyway but I want to ensure the future for someone else.
Are you expecting to only have five years left on this world :shock:

The recommended service life of the PCB mounting NiMh battery is five years.
At my work place, we change these (used on industrial control systems) every five years, including on the spare cards.

Mark

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Re: A7000+ battery

Post by KarateEd » Fri May 31, 2019 12:46 am

1024MAK wrote:
Thu May 30, 2019 11:30 pm
KarateEd wrote:
Thu May 30, 2019 5:37 pm
Thanks all for your replies.

I will be putting this battery somewhere in a 'safe' non-threatening location with extender wires to ensure when it does go, it won't destroy anything on the machine.

It's likely that I won't be alive by the time it does that anyway but I want to ensure the future for someone else.
Are you expecting to only have five years left on this world :shock:

The recommended service life of the PCB mounting NiMh battery is five years.
At my work place, we change these (used on industrial control systems) every five years, including on the spare cards.

Mark
Really? Sounds pretty short to me.....ah well, If I have to get more, I got them in a 4 bundle but could just set something up here like in the Master with the diode/resistor on a 2032, that's also pretty easy.

and no, I expect to live longer but I want to see how long practically this will go before doing the watusi......
Ed...... :-)

3 working Beebs, 1 RetroClinic Master, 1 normal Master, 1 A3010, 1 Pi2 RISC OS, 2 broken Beeb Motherboards, 1 Omnibus A7000+ server, 1 A7000+ Desktop, 1 PET, 1 C64, 1 C128, 1 Amiga 500 and 1 Roamer.

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Re: A7000+ battery

Post by philpem » Fri May 31, 2019 3:12 pm

1024MAK wrote:
Thu May 30, 2019 11:25 pm
philpem wrote:
Thu May 30, 2019 2:05 pm
As an aside, the chip will also work quite happily with a CR2032 or similar lithium coin cell in a holder, but you'll need to add a series diode (e.g. 1N4148) to prevent it from being charged. They're essentially leakproof and easy to change.
You also need a suitable resistor in series with the diode, to limit the fault current in the event that the diode fails short circuit (if a diode is going to fail, it is most likely it will go short circuit).

Mark
Is that necessary with the two Acorn usually fit on the PCB? (assuming they work of course!)

On the 5-years-life thing -- the issue is that the electrolyte eats away at the casing. It's very similar to alkaline battery electrolyte. This tends to accelerate if the battery is run completely flat -- which is why you should remove batteries from your remote controls as soon as they run flat!
Last edited by philpem on Fri May 31, 2019 3:16 pm, edited 1 time in total.

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Re: A7000+ battery

Post by KarateEd » Fri May 31, 2019 6:03 pm

philpem wrote:
Fri May 31, 2019 3:12 pm
1024MAK wrote:
Thu May 30, 2019 11:25 pm
philpem wrote:
Thu May 30, 2019 2:05 pm
As an aside, the chip will also work quite happily with a CR2032 or similar lithium coin cell in a holder, but you'll need to add a series diode (e.g. 1N4148) to prevent it from being charged. They're essentially leakproof and easy to change.
You also need a suitable resistor in series with the diode, to limit the fault current in the event that the diode fails short circuit (if a diode is going to fail, it is most likely it will go short circuit).

Mark
Is that necessary with the two Acorn usually fit on the PCB? (assuming they work of course!)

On the 5-years-life thing -- the issue is that the electrolyte eats away at the casing. It's very similar to alkaline battery electrolyte. This tends to accelerate if the battery is run completely flat -- which is why you should remove batteries from your remote controls as soon as they run flat!
The CR2032 isn't chargeable so yes, the diode and resistor are necessary. I can't remember what happens if you try to charge a non-chargeable battery but fire or explosion comes to mind. Even if you were to mount the battery on the MB it would need these as the battery that goes there is a chargeable battery. The Cr2032 isn't.
Ed...... :-)

3 working Beebs, 1 RetroClinic Master, 1 normal Master, 1 A3010, 1 Pi2 RISC OS, 2 broken Beeb Motherboards, 1 Omnibus A7000+ server, 1 A7000+ Desktop, 1 PET, 1 C64, 1 C128, 1 Amiga 500 and 1 Roamer.

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Re: A7000+ battery

Post by 1024MAK » Fri May 31, 2019 6:40 pm

philpem wrote:
Fri May 31, 2019 3:12 pm
1024MAK wrote:
Thu May 30, 2019 11:25 pm
philpem wrote:
Thu May 30, 2019 2:05 pm
As an aside, the chip will also work quite happily with a CR2032 or similar lithium coin cell in a holder, but you'll need to add a series diode (e.g. 1N4148) to prevent it from being charged. They're essentially leakproof and easy to change.
You also need a suitable resistor in series with the diode, to limit the fault current in the event that the diode fails short circuit (if a diode is going to fail, it is most likely it will go short circuit).

Mark
Is that necessary with the two Acorn usually fit on the PCB? (assuming they work of course!)
Yes. The recommended value is a 4.7k ohm resistor. Lithium coin cells can’t tolerate any significant charging current. The resistors fitted on the main board are too low a value to limit the current flow in the event of a fault to a safe value.

The 4.7k ohm resistor should not affect the 50uA current required by the RTC CMOS chip to maintain the time and settings.

Mark

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Re: A7000+ battery

Post by KarateEd » Fri May 31, 2019 11:40 pm

This diagram is from the Acorn FB site and shows how to connect a battery that isn't chargeable into a circuit that is.
Battery fix.png
In 32 bit Acorn machines for instance, instead of the Master 3 prong you have the 'Varta' semi-circle where you would attach the cables then put the battery in a safe location.
Last edited by KarateEd on Fri May 31, 2019 11:41 pm, edited 1 time in total.
Ed...... :-)

3 working Beebs, 1 RetroClinic Master, 1 normal Master, 1 A3010, 1 Pi2 RISC OS, 2 broken Beeb Motherboards, 1 Omnibus A7000+ server, 1 A7000+ Desktop, 1 PET, 1 C64, 1 C128, 1 Amiga 500 and 1 Roamer.

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Re: A7000+ battery

Post by philpem » Sat Jun 01, 2019 11:44 am

KarateEd wrote:
Fri May 31, 2019 11:40 pm
This diagram is from the Acorn FB site and shows how to connect a battery that isn't chargeable into a circuit that is.

Battery fix.png

In 32 bit Acorn machines for instance, instead of the Master 3 prong you have the 'Varta' semi-circle where you would attach the cables then put the battery in a safe location.
Interesting. I wouldn't have picked a 1N4001 due to the high reverse leakage current (50uA worst-case). A 1N4148 would seem to be a much better choice at 25nA worst-case reverse leakage current (around 2,000 times lower).

I'll take 1024MAK's point on the 4k7 resistor - I need to go into the A3010 again at some point and find the loose/damaged component in the audio circuit which is making the speaker crackle when the plugs in the mouse port or VGA port are moved, so I'll fit a 4k7 when I do...
Last edited by philpem on Sat Jun 01, 2019 7:29 pm, edited 1 time in total.

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Re: A7000+ battery

Post by guddler » Mon Jul 01, 2019 12:07 pm

Just going to tag this on the end here rather than create a new thread!

I assume that I can fit a CR2032 with 4.7k resistor and 1N4148 diode in an A5000 ?

It's been on the bench in bits for far too long now and I need to get it back to it's owner :)

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Re: A7000+ battery

Post by 1024MAK » Mon Jul 01, 2019 4:36 pm

Yes, that will work.

However I recommend diodes: BAT42, BAT43 or BAT46 as they have a lower forward voltage drop.
Recommended resistor: 4.7k ohm. You can also use a 3.9k, 4.3k, 5.1k or 5.6k resistor. 1%, 2% or 5%. 250mW / ¼W or 500mW / ½W.

The CR2032 can be changed with the machine powered up.

Mark
Last edited by 1024MAK on Mon Jul 01, 2019 4:41 pm, edited 1 time in total.

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