VHF battery life

Ok guys ... How do you handle multi day or longer trips with your radios? Buy extra factory batteries? Buy a unit that takes AA's? Only turn it on for a few hours a day? I am looking to pick up a radio and need to be able to use for a remote week long trip.....
Thoughts?

Ok guys ... How do you handle multi day or longer trips with your radios? Buy extra factory batteries? Buy a unit that takes AA's? Only turn it on for a few hours a day? I am looking to pick up a radio and need to be able to use for a remote week long trip.....
Thoughts?

I bought an ICOM M72 which had the biggest capacity battery.  I once ran the numbers on battery life once, but will have to look it up.

Don't get the AA's.  You'll have reduced maximum output power when using them as they can't source enough current to support 5W transmit.  Read the fine print and you'll see this.

BTW, the M72 supports 6W output, which is the highest I've seen.  For most trips I run the VHF in lowest power transmit mode (1W) because you're never that far from the others that you need to do otherwise.  I like the 6W in case of an emergency.

For typical trips up to 1 week, I've not had any problems running the battery empty.

-Allen

Allen's got more wilderness experience than I do, but a lower power output is better than no power output at all.

 My Lowrance LHR 80 required recharging after 2 days of leaving it on.  Perhaps it was harder on the battery because of the GPS function (not to mention the hours that I spent broadcasting drunkin sea shanty's), so I'm certain I could have gotten a lot more from it if I was more conservative, but it just doesn't seem to rec'v very well when it's off.

I guess If your only using it for emergency transmissions that might not be an issue, but if your using it for on the water communications without facilities to plug it in, I think I'd want another power source. I've heard of solar panels and such, but some well wrapped AA seems like a sane (if less ecologically sound) backup.

That said, my radio only uses the LiPO pack

GPS sucks battery fast.

Of course a spare battery is good.  In that case, I'd rather pack a spare Lithium-Ion battery than AA's.

-Allen

This example may help with the secret decoding of battery life.  The ICOM M72 claims 15-16 hours of battery life.  This assumes a 5:5:90 ratio of TX:RX:Standby.

TX is 6W  high mode.  RX is built in speaker.

TX high mode consumes 1700 mA
RX Speaker consumes 400 mA
The battery is rated 2000 mAH

At 16 hours 5% TX, this means 5% of 16 hours = 0.8 hours draining 1700 mA ==> 1360 mAH
At 16 hours 5% RX, this means 5% of 16 hours = 0.8 hours draining 400 mA ==> 320 mAH
The remainder 2000-1360-320= 320 mAH of standby, or 22.2 mA at 14.4 hours

Going to TX 1W low mode only consumes 700 mA.  Doing all the reverse math leads to ~26.7 hours assuming the same 5:5:90 split.  On a 6 day trip this means you get ~4.5 hours of ON time per day.

Now lets look at this another way, how many minutes can you talk/listen per day and make 48 hours (6 days at 8 hours) of on time?  Reversing the math yields almost 10 minutes of TX and 10 minutes of RX.  That's actually a lot of time if you think about it.  Your average message may be 1 minute and this gives you 10 minutes.  How much you really want to talk on the VHF anyway?

-Allen

A couple more points.

I selected the M72 because of its large battery pack.  Other radios, like the M34 have 1/2 that, so obviously your battery life would be half that.

Also the calculations above assume the RX has speaker at max.  Turn the volume down and get more life ... for instance, at 1/2 volume you get another 2 minutes of TX and RX time per day.

-Allen

Did I lose everyone here?   

BTW, in checking the M34 specs ... the M34 can take an AA battery pack.  Using Alkaline AA, the maximum transmit power is 2W in high mode (vs 5W in high mode using the Li-Ion battery).

-Allen

I went ahead and picked up a m72. I liked the smaller size over the floating radios. I'll leash it to my PFD and be done with it.
Still thinking about getting an extra battery as back up

I went ahead and picked up a m72. I liked the smaller size over the floating radios. I'll leash it to my PFD and be done with it.
Still thinking about getting an extra battery as back up

There are some refurbs on the market that are like $10 more than a new battery.  I just ordered one (but just found out it is backordered  ).  Anyway, it's worth the shot to use the battery out of it as an extra battery when on trips, or to use the whole radio as a spare when not on trips.

-Allen

Ya I saw several places with refurbs but no one had any in stock. I got mine for for 165+ shipping which is by far the lowest price. It looks like Icom plays like apple and tries damn hard to keep the price at the MSRP.