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Any suggestions or recommendations would be appreciated.
I checked into the weekly net a couple weeks back and was advised I might have a problem with my radio and sure enough I’m having a low current situation.
I have a FT-857 in my ’04 Dodge Ram 2500 (diesel so it’s a dual battery setup for what it’s worth) wired direct to the ditch side battery with the typical Anderson powerpoles/wires/in-line fuses. The radio is supposed to draw 0.5a receiving and it’s only pulling 0.17a, and it’s not getting even close to the 22a to transmit at 100w. No difference if the truck is running or not. The truck starts and runs completely fine. Good voltage, just low amperage getting to the radio.
Troubleshooting thus far:
Oreilly Auto tested batteries good.
Alternator tested and threw a “voltage regulator failed.” This truck doesn’t have one (The alternator and the PCM handle it). Replaced the alternator and still the same code from oreilly. Still scratching my head on this one too.
Cleaned battery terminals and replaced one. Wiring to the radio is good. I hooked up my lifepo4 battery box and got the desired amperage from there.
I’m not sure where to go next. I can’t understand why I can’t get more amperage out of the batteries. I don’t see how the PCM would be limiting me if the radio is wired to the battery’s terminal and ground location.
Thanks in advance.
Ryan, KC1KMT
And what is the rated output of the new alternator? And what is the rating / specs for the battery saver between the two batteries?
Chris K1ZG
The alternator is 12v/136a. I don’t know of any battery saver, nor does google so far for the Gen 3 Ram.
Does this vehicle have current sensors? My F-150 did. If so you have to connect down stream of the current sensors. Being an ‘04 I doubt it does, but I do not know.
The receiver pulling 0.17 A may be ok. The 0.5 A specification is probably a maximum with audio unsquelched and volume turned up. Mobile rigs have a lot of power for the speaker to overcome road noise.
“12V” on a lead acid battery is about 13.6V with no load/no charge and rises to about 14.4V under charge, but varies with temperature. What does the voltage do when transmitting? If it drops, then look for a bad connection?
Another thing to look for, do the panel lights on the radio dim when transmitting? (they should not)
jeff, wa1hco
What I understand is the alternator and the PCM control the batteries and charging. I have the radio connected to the positive terminal and the ground bolt the battery is grounded to. I even tried disconnecting the battery completely and clamped the radio cables to the battery alone and got no change.
I eventually wanted to do an auxiliary battery with a dc-dc charger but concerned that if the radio can’t get enough current, how will the dc-dc charger be able to function correctly.
Hello Ryan,
170ma is a fair rx current for FT-857. Another test is to set the radio to SSB and key the radio without any audio into the mic. You should see the Tx current with the idle current into the driver and finals. This should be 3-4 amps.
It’s possible you are looking too hard at batteries and charging circuits. If you have around 13 volts measured at the radio’s DC connector there is no way those items can effect the amount of current the radio consumes.
If the 13V is there during Tx and the current (and therefore RF power) is low I would suspect the radio is folding back due to a high antenna SWR.
If you are monitoring current while TXing SSB at 100w the current will be far less than 20A unless measured with a peak reading meter or o’scope due to the low duty cycle of SSB. I suggest using FM or CW since they are both 100% duty cycle.
73
Hamilton
To close this loop in case someone stumbles across this thread in search of their own gremlin I settled on the decision that it is old/weak truck batteries even though they are not affecting vehicle operation yet. Rather than replace otherwise still working batteries, I used this as an excuse to a DC-DC charger and house battery. I’m still experimenting with drive times and recharging rates or even if I have the charger configured.
Thank you to all who offered help.
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