I have the cobra CXT275 they have been on the desktop charger for 5 days. They won't charge over a 1/4 of the way how do I get the maximum charge?

Most lithium small radio batteries are 3.6 volts. If AA or AAA batteries, multiply by 1.5 volts. 4 batteries = 1.5 * 4 = 6 volts MAXIMUM. Rechargeable batteries are 1.2 volts. Your charger would be a much higher voltage because it takes power to "push" the charge into a battery. You didn't say, so I am assuming you want to operate the radio with a wall charger. I've done this by soldering the wires to the battery contacts. You need a higher voltage than 3.6 volts, but milliamps is more important. You need enough milli amps to get the radio to transmit. Too much and it frys, literally. So, this is all on you to decide if the risk is worth it. I use a 5-6 volt power supply set on no more than 1 amp (800 ma is my favorite size) 1 amp = 1000 ma. Let us know if this helped!

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Who knows.
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How long before it started to charge

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The Cobra CXT275 radios can operate on any type of battery (Alkaline, Ni-Cad, NiHM). Each radio uses 4 AAA batteries. Only special rechargeable batteries can be recharged in the actual radio (see below)
If I remember correctly, they come from the factory with NiHM batteries rated at 300mAH. "mAH" stands for milli-Amphere-Hour and it represents the storage capacity of the battery. (The larger the mAH, the longer run time of the battery)

You have 2 options: A or B
Option A) Buy a set of Nickel-Metal Hydride AAA rechargeable batteries and a external battery charger. When the batteries die, pop them out of the radio, and charge them in the external charger. When they are recharged, pop them back in the radio.
Option B) If you want the ability to charge the batteries in the radio, using the "drop-in charger" then you will need modify the batteries so they can charge in the radio.
Follow these steps: You must be somewhat electrically inclined to do this...Note: By doing this you are going to void the warranty of the radio and new batteries that you just purchased.
1) Buy a set of Nickel-Metal Hydride AAA rechargeable batteries. You can probably find some rated at 600 mAH (this will extend the run time)
2) Looking at the back of the radio with the cover removed, there are 4 slots for batteries.
3) Looking at the battery slot on the far right, you should notice 2 contacts for the negative contact. The one on the bottom, is the contact for the radio to receive power from the battery. The one on the side (about 1/8" inch up from the bottom contact), is the contact for the charger to recharge the battery.
4) You will need to modify 1 battery for each radio. Somehow you need to bridge the bottom contact with the side recharge contact.
5) (look at the negative end of the cobra factory batteries and this should help you realize what you need to do) depending on the manufacturer of the new rechargeable batteries, you may be able to use an X-acto knife and remove 1/4" of the plastic wrapper from the bottom of the battery on the negative end. This should reveal the metal shell of the battery that can mate with the radio's side recharge contact.
If it does not, you need to find another way to have it mate with the bottom contact. You might be able to use some Aluminium Foil to bridge the bottom contact with the side recharge contact. Be sure the Aluminium Foil does not touch the positive contact of the battery to the left! You could have an electrical short!
6) Insert the Modified Battery into the right slot.
7) Insert the other 3 new batteries into the other slots. These do not have to be modified. Only the right most battery needs to be modified.
8) Drop the radio in the charger for the batteries to charge. The red LED on the charge base should come on. If it does not, then the side recharge contact is not making a good connection with the negative battery terminal.
9) If the red LED comes on, then the modification works. Let the batteries charge for 24 hours for their first initial charge.
10) When the batteries die after radio use, then charge them for about 12 - 16 hours in the drop-in charger. Do not let the radios sit in the charger for long periods of time. That can destroy the batteries. Take the radios out of the charger when the allotted time has passed.
11) If you hardly ever use your radios you will want to drop them in the charger for about 8 hours every 3 months. This will keep the batteries fresh without damaging them.
I hope this helps, Thomas (Electrical Engineer)

• Hi, to power the radio on or off press and hold the "MODE" button on the top center of the face for 5 full seconds.

• Hope this helps.

Regards, Tony

Probably time to trash and purchase new.
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i just bought a cobra cxt275 walkie talkie i want to know what channel to set it on to get the best distance without breakin the law

yes as long as your on the same channel and freq.