NiMH Battery selection switch query

Discussion related to the Garmin GPSMAP 66s/st GPSr
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robert
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NiMH Battery selection switch query

Unread post by robert »

Does anybody know if the built in battery selection switch does anything more than change the parameters of the battery level meter and turn off the charger?

The reason I ask is that I have the battery selection switch taped over to use with my own NiMH batteries. But for an extended trip I want to carry some spare Lithium non rechargeable batteries to use if I deplete the NiMH before I am able to recharge them.

I don't really want to un-tape and re-tape the selection switch if leaving it will cause no harm to the device. I am happy to ensure the Lithium's are not charged and cope with a less accurate battery level indicator. But I would not want to damage the unit.

I appreciate no would may have the answer to this but I thought I would ask.

Thanks
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GPSrChive
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Re: NiMH Battery selection switch query

Unread post by GPSrChive »

If you have the button in the battery compartment take over, do not install anything other than NiMH batteries, or you will cause irreversible damage to your GPSr and possibly yourself

Please see the GPSrChive > GPSMAP 66 > Accessories page and consider our NiMH Battery Adapter as a possible solution.
robert
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Joined: Tue Oct 01, 2019 1:19 pm
Location: United Kingdom

Re: NiMH Battery selection switch query

Unread post by robert »

Yes I know what the manual says and trying to charge Lithium batteries could be catastrophic. But as I said in my post I was quite happy to be responsible for this aspect.

Anyway if it is not known what exactly the NIMH changeover button actually does at the electronic level that is fine.

Your battery option would be a more easily changeable option, I agree if this is needed.
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GPSrChive
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Re: NiMH Battery selection switch query

Unread post by GPSrChive »

robert wrote: Thu Apr 14, 2022 1:38 pm Anyway if it is not known what exactly the NIMH changeover button actually does at the electronic level that is fine.
This button serves as a switch to enable the battery charging circuitry. When closed, the internal battery charging circuit will attempt to charge the batteries installed inside your device, regardless of chemical composition.
robert
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Location: United Kingdom

Re: NiMH Battery selection switch query

Unread post by robert »

Well that is what I assumed it would do. So it will prevent non rechargeable batteries from being presented with a charging voltage when the device is connected to a USB port. So as long as the GPSMAP is not connected to a USB port then it should not make any difference to it or the batteries.

But I don't have a circuit diagram so I cannot be sure it does not make any changes also because of the voltage difference between NIMH and Lithium batteries.

So I will play it safe and remove the switch bypass when using non NIMH batteries until I know otherwise.
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GPSrChive
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Re: NiMH Battery selection switch query

Unread post by GPSrChive »

When enabled, the GPSr automatically configures the device for NiMH batteries and calibrates the battery guage accordingly. The setup menu to select battery chemistry is no longer displayed.
mpistora
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Re: NiMH Battery selection switch query

Unread post by mpistora »

robert wrote: Thu Apr 14, 2022 11:23 am Does anybody know if the built in battery selection switch does anything more than change the parameters of the battery level meter and turn off the charger?
I hope the "Battery Type" setting also affects when the device shuts down:
  • for primary cell (Alkaline, Lithium) after complete discharge of the cell,
  • for rechargeable battery (NiMH, Precharged NiMH) when the limit voltage is reached, when the battery is not destroyed yet.
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GPSrChive
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Re: NiMH Battery selection switch query

Unread post by GPSrChive »

mpistora wrote: Wed Apr 20, 2022 11:02 pm
robert wrote: Thu Apr 14, 2022 11:23 am Does anybody know if the built in battery selection switch does anything more than change the parameters of the battery level meter and turn off the charger?
I hope the "Battery Type" setting also affects when the device shuts down:
  • for primary cell (Alkaline, Lithium) after complete discharge of the cell,
  • for rechargeable battery (NiMH, Precharged NiMH) when the limit voltage is reached, when the battery is not destroyed yet.
Yes, it does that also. If you have the wrong battery type selected, you may observe premature device shutdown.
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