Moto T200 FRS issue

[Roodog2k]

About two-three years ago,, I bought the 3-pack of the T200 handhelds just for goofing around with the kids. I just found them and given our self-isolating orders, I brought them out of storage.

So, I charged-up the batteries that came with the radios, kids went for a walk around the block. After about 20 minutes, we started getting low battery indicators on the two radios we were using.

So, I thought maybe the 3.6v NiMH battery packs that came with the radios may have gone south, so I tried using three freshly-charged Enloop AAs. I know the manual says to use alkaline batteries, but the 3 Enloops should be giving me 3.6v on a fresh charge anyhow, just like the battery pack that came with the radios.

Anyway, still getting the same thing. Battery seems to go dead fast.

But, I noticed something. If I power-cycle the radio, the low battery charge seems to go away for the same period of time it took to "discharge" the first time.

Anyway, I'm assuming that this model is one of the 0.5w radios, so I'm just wondering what's going on. Is it looking for 4.5v? Is there some weird sub menu that I'm mssing? Something else going on?

 

[RFI-EMI-GUY]

There may be subtle circuitry or a switch that detects a NIMH battery pack vs Alkalines. Your enloops have terminal voltage equal to a discharged Alkaline. The radio thinks it has Alkalines. Do the NIMH Packs plug in with a wire lead?

 

[Roodog2k]

Do the NIMH Packs plug in with a wire lead?

No, they look like three AA batteries shrink-wrapped together.

 

[RFI-EMI-GUY]

There is something in either the circuitry or some mechanical device that determines that there is a rechargeable NIMH pack vs AA alkaline cells.

The radio thinks the Enloops are alkaline batteries because physically they are the same only lower terminal voltage. The radio has to determine this or someone could try to charge alkalines in the radio which can explode. It could be a mechanical switch, or a different tab to contact the NIMH pack battery terminal or some software wizardry. Your assignment is to outsmart it or forget about using the Enloops.

 

[n1das]

There is something in either the circuitry or some mechanical device that determines that there is a rechargeable NIMH pack vs AA alkaline cells.

The radio thinks the Enloops are alkaline batteries because physically they are the same only lower terminal voltage. The radio has to determine this or someone could try to charge alkalines in the radio which can explode. It could be a mechanical switch, or a different tab to contact the NIMH pack battery terminal or some software wizardry. Your assignment is to outsmart it or forget about using the Enloops.

The Talkabouts sense the battery type by looking for a voltage on one of the terminals between two of the batteries in the pack. The rechargeable NiMH pack is wrapped with heatshrink tubing so that only the end terminals are exposed and doesn't connect to the middle terminals. When installed in the radio, no voltage appears at the terminals between two of the cells. When AA Alkaline or AA NiMH batteries are used, a voltage appears at the middle terminal sensed by the radio and disables the battery charger. I don't think the radio cares about the battery voltage as much as ensuring the battery charger is disabled when AA Alkaline batteries are used.

I have modded a few Talkabouts in the past to enable charging AA NiMH batteries. The terminal between 2 of the cells monitored by the radio has a tab which springs against a pad on the PCB to connect to the PCB. I cut into the plastic in the battery compartment enough to get to the tab which goes down to the PCB and cut the tab off. Now the radio never sees a voltage at that terminal and thinks NiMH batteries are installed all the time regardless of whether I use the heatshrink wrapped original NiMH pack or AA NiMH batteries. The radio now enables the battery charger circuit with AA NiMH batteries installed. With 2500mAh NiMH AA batteries, the charging time for a full charge was doubled to about 30 hours but the operating time was increased to 30-40 hours on a charge, depending on how much I transmitted with them.

I did this mod on a pair of MS350R Talkabout radios. These are the yellow waterproof (1 meter depth for 30 minutes) Talkabouts and were one of a few bubble pack models that were GMRS repeater capable. Repeater capability went away under the new rules for FRS. They also were among a few Talkabout models that don't have Motorola's crappy and much hated X-Pand audio companding system. Just plain non-companded audio. The only drawback to doing this mod was that using 2500mAh NiMH batteries made the radio heavier and no longer would float in water.

 

[Roodog2k]

... When installed in the radio, no voltage appears at the terminals between two of the cells. When AA Alkaline or AA NiMH batteries are used, a voltage appears at the middle terminal sensed by the radio and disables the battery charger. I don't think the radio cares about the battery voltage as much as ensuring the battery charger is disabled when AA Alkaline batteries are used....

Perfect, thanks!