Powering old walkie talkies with li-ion?

[prcguy]

These don't sound like a good idea to put inside an HF transceiver. Might generate a lot of RFI.

Actually it is not at all a 1.5V Lithium. It is a standard 750 mAh 3.7-4.2V Lithium Ion with a buck inverter inside each can.

https://www.reddit.com/r/AAMasterRace/comments/chzxhv

While useful, I don't think it is a cost effective replacement for 12 AA batteries. 3 x $31 = $93 for essentially 750 mAh whereas 3 x 18650 Li-Ion are going to be much cheaper and produce much more power.

Also the 12 buck invertor's are likely to introduce some noise into the radio receiver.

 

[KEWB-N1EXA]

I rarely post, however this thread reminds me why I don't. I had seen the Tenavolts AA cells and thought it might help out the OP. I understand that there are no 1.5 volt Lithium AA cells, this product could work for the OP's original post. I am actually kicking myself for even trying to help.

I know how you feel but stay in the race

As they say don’t wreck the car to lead a lap!

Peter N1EXA

 

[DaveC1964]

I have been converting stuff to Li-Ion. I was once wary of them, but you can get batteries with protection circuits. Currently I am repacking Motorola SABER radio batteries with two lithium ion cells and a protection board. A small battery has 2200 mAH and 7.4 to 8.4V which is nearly same as the 6 NIMH cells it replaces. Works fine just need a charger that matches the chemistry and voltage.

I have a radio that runs on nominal 13.8 V . 3 Lithium Ion batteries deliver 11.1 to 12.6 V and the radio is fine with that range.

How much loss of range will I get when the pack drops to 10.5V when the radio wants 12V? Is it significant or not really from your experience?

The issue with Li-ion is that they only are at 4V for a short time. They drop to the 3.5-3.8V pretty quick, they seem to "like" being in that range longer.

I could get a DC-DC converter to keep at 12V but I am afraid of those putting out noise to interfere with the RF and will introduce a whine. Maybe they make filtered ones?

 

[RFI-EMI-GUY]

How much loss of range will I get when the pack drops to 10.5V when the radio wants 12V? Is it significant or not really from your experience?

The issue with Li-ion is that they only are at 4V for a short time. They drop to the 3.5-3.8V pretty quick, they seem to "like" being in that range longer.

I could get a DC-DC converter to keep at 12V but I am afraid of those putting out noise to interfere with the RF and will introduce a whine. Maybe they make filtered ones?

Your AA cells are going to drop to 1.3V per cell, 10.4V in constant use. You probably don't notice it until they perish.

10.5 V is slightly less than 3.7V per cell where most Li-Ion chargers will kick in. But no matter they will go deeper. I don't notice anything with a 5 watt UHF FM Motorola SABER when they approach discharge. They hold up power well. I am pulling about 3 amps perhaps 1.5C with the smaller cells.

If you have 8 AA cells in your radio, consider the capacity of an alkaline cell.

Discharge tests of Alkaline AA batteries 100mA to 2A

Alkaline battery discharge curve, AA battery discharge curve,AA battery capacity,Resources for designing equipment using AA cells from PowerStream

www.powerstream.com

Calculating the Battery Runtime - Battery University

Examine battery losses when estimating energy reserve

batteryuniversity.com

You don't need a DC-DC converter or boost circuit nor do you want one in the radio.

Just get the biggest 3 or 6 (2P3S) protected cells that fit into your space and don't worry. The technology is well beyond what alkaline or NIMH can deliver. I considered making a AA alkaline pack for my SABER radios and realized the effective series resistance (ESR) made those cells very inefficient. Lithium Ion is the way to go.