So I'm making plans for a mobile install on a older (2003) Honda CR-V. I'm ultimately looking at 3-5 radios, maybe 2-3 Harris 7/800 mobiles for NAS, and a Kenwood NX-3720 and 3820 for ham stuff. I may also add a Uniden scanner at some point, maybe a 536HP.
Yeah, as ka3aaa suggested, I don't see an issue with what you have.
The 2-3 Harris radios won't draw a lot of power, maybe 1-2 amps each when actively receiving. When sitting idle, probably less.
The two Kenwood's won't draw much on their own, except when transmitting, and even then, you are looking at around 12 amps transmit, an amp or so RX, and less when sitting idle.
Scanner won't draw much.
I'd say you've got about 5-6 amps maximum draw with all your radios on, all receiving with the volume up. That should not overtax your alternator.
And you can only transmit with one radio at a time, unless your passenger is going to be talking also. That extra 12 amps or so periodically should not break anything.
If you did some digging, you should be able to find something from Honda that tells you what the alternator output is at different engine RPM's.
If you got hold of the right manuals, they should have something that lays out all the loads in the vehicle. That should give you an idea of how much extra capacity the alternator has.
If your Honda is tricked out with all the options, the alternator would still have extra capacity. It would/should be designed to run everything in the vehicle with the engine at idle. That would mean high beams on, windshield wipers on high, defroster running on high, heated seats on, stereo cranked up, trailer hooked up with trailer lights on, etc. And don't forget it's probably got a couple of cigarette lighter sockets that will run 10amps each….
It's unlikely you'd be driving around with all that stuff cranked up at the same time, so unlikely you'd ever overload the alternator even with your radios.
Also, remember that people will often add bigger stereos, audio amplifiers, charging lots of cell phones, auxiliary lighting, etc. Rarely do any of them add bigger alternators or extra batteries.
I don't think you have enough load there to be concerned unless you've got a failing alternator, or you've added a lot of other accessories.
I've also looked at getting a second battery with an isolator, but from what I've read that only helps when the engine isn't running, and I tend to do a lot of driving/road trips so I'm not sure how much a second battery would really help.
Yeah, second battery is like adding an auxiliary fuel tank. It only gets you so much further before you have to stop and fill up.
Driving along at highway speed should put the engine RPM's right around the sweet spot for the highest alternator output.
I'd pay more attention to the health of the system. Make sure you have a good battery. Make sure you lay out all your wiring correctly, fused properly, good connections and proper sized wire. I'd also recommend adding something like a Lind shutdown timer that will kill everything after you shut down the engine.
