Batboard

Hello:
I have successfully opened up and emptied out the GTX battery housing and now would like to build a 13.8 volt dc input to 7.5 volt dc output for the Motorola GTX800 portable.
Anyone have a working design or schematic for doing this ?

Also I did order a battery eliminator off of fleabay but when put in use on a gtx the gtx gives you low battery alert and drops tx.
Now the gtx is proven to be good and vehicle battery voltage was good so its qaranteed to be the batt eliminator.
The batt eliminator from fleabay does put out 7.2 volts but theres apparently not enough amps output from my testing.( 7.2 volt output was at eliminators output contacts and not on radio with tx load so voltage could be dropping on tx but didn't test for that yet)
Id rather just build a known good eliminator circuit and toss the rest.
Thank You
Satelite

I have used a 5 amp adjustable regulator IC/transistor on a copper heatsink mounted in the battery housing.

ST Micro low drop out voltage regulator LD1084V. Cost is about $1.90.
http://www.st.com/web/en/resource/techn ... 003086.pdf

Why a 5 amp device? Lower voltage drop at 2 amps. A 3 amp, LD1085V.

Any 7v regulator should do the trick. "http://pdf1.alldatasheet.com/datasheet- ... 8L075.html" was the first thing I found in a google search.

I did a similar mod to an old Kenwood handheld for the local fire station I was a member of at the time. 7v tran and bits in the batpack hooked into the 13v fusebox, hard screwed/bolted to the chassis of the vehicle with a proper 5/16 mount in the roof terminated in a BNC plugged directly into the handheld and a speaker mic for the microphone. Works a treat.

Well... "any" 7 volt regulator will not do the trick, for example in the 7800 series, a 78Lxx regulator is a low current version and generally rated at 100mA, a 78Mxx is medium current, around 500mA, 78xx is standard, around 1A. None of these would would be a good choice.

You'll want to go with the 5A regulator Will mentioned.

Hello:
Yeah I agree with Wills recommendation on the 5 amp regulator.
I have a fleabay eliminator that puts out the 7.5 volts but no wheres near the amps needed to properly tx.
Satelite