Keeping UHF radios charged?

[Gremlin]

Anyone had bright ideas, or know if equipment is available, to keep radios charged, or run them off the bike, as you are riding along?

Busy been reading threads on baehr etc (just acquired a verso xl) and looking at putting a radio into that as well, for bike to bike.

One weakpoint (assuming everything else goes well :sweatdrop) is battery life in the radio (why I didn't go for a bluetooth/wireless system), as days could be quite long - some of the longest have been 20 or more hours.

[Hitcher]

Not all UHF radios allow batteries to be charged whilst in the radio. If you're going to have to faff around changing batteries, best buy some decent alkalines, rather than having the additional complication of a bike-powered charging pack.

[Gremlin]

Well, to be cruel to it, it doesn't matter what the battery life is, as long as the radio runs, because its effectively plugged into mains permanently.

Hell, if some sort of kit is available that allows a cable to be plugged into the radio, it wouldn't even need a battery...

[JMemonic]

Anyone had bright ideas, or know if equipment is available, to keep radios charged, or run them off the bike, as you are riding along?

Busy been reading threads on baehr etc (just acquired a verso xl) and looking at putting a radio into that as well, for bike to bike.

One weakpoint (assuming everything else goes well :sweatdrop) is battery life in the radio (why I didn't go for a bluetooth/wireless system), as days could be quite long - some of the longest have been 20 or more hours.

Not as worry really, depends on the radios its easy to charge voltages up to 13.8 volts with little effort, over that there are methods but that's fairly moot for hand held.

The easiest is if the radio has a 12 volt input, that is suitable for a car, the current draw is normally no higher than 1 amp.

[JMemonic]

Well, to be cruel to it, it doesn't matter what the battery life is, as long as the radio runs, because its effectively plugged into mains permanently.

Hell, if some sort of kit is available that allows a cable to be plugged into the radio, it wouldn't even need a battery...

Unfortunately this is not quite true for all radios, most that have the 12 volt input dont have a 12 volt battery ie 7.2 or 8 volt, internally they have a charging circuit for the battery which will generally provide enough current to charge the batteries and run the receiver section, when the radio is on transmit it draws the extra current off the battery.

[NinjaNanna]

Cheap "universal" solution would be to make a dummy battery pack out of pieces of dowel, use a couple of pieces of metal for the contacts and then connect it to a suitably rated mobile phone car charger.

Trademe would be the best bet for the charger, remember each battery is 1.5V so if it takes:

3 batteries you want a phone charger rated for 4.5 - 5V if its
4 batteries you want something rated for 6 - 7 Volts

To get the cable into the battery compartment easiest way would be to file a small slot into the battery lid so that it still closes.

[BMWST?]

Cheap "universal" solution would be to make a dummy battery pack out of pieces of dowel, use a couple of pieces of metal for the contacts and then connect it to a suitably rated mobile phone car charger.

Trademe would be the best bet for the charger, remember each battery is 1.5V so if it takes:

3 batteries you want a phone charger rated for 4.5 - 5V if its
4 batteries you want something rated for 6 - 7 Volts

To get the cable into the battery compartment easiest way would be to file a small slot into the battery lid so that it still closes.
how does this work in relation to hte post above where the battery pack is required for "transmit."?Was thinking some uhfs would be good in a small group tour situation...

[NinjaNanna]

how does this work in relation to hte post above where the battery pack is required for "transmit."?Was thinking some uhfs would be good in a small group tour situation...

The post above is working on the assumption that the charging circuit/external power supply is not up to the job.

The replacement "battery" pack does not suffer the same issue as it effectively bypasses the charging circuit (if it has one at all).

That being said though you will want to ensure the car charger is up to the job current wise as well, somewhere around 0.75A should be suffice.

[Gremlin]

Given that I know bugger all, it looks like project for a geek, and not some plug and play (someone may have seen my post in martybabe's thread... it really isn't a good idea for me to "have a crack").

Perhaps in the new year, as I would need everything up and running by new years day... so not enough time...

[davereid]

You can easily charge NICADS while they are in the radio.

As a rule of thumb, a NICAD can be left on charge forever, if the charge rate is 1/10th or less of its amp-hour capacity.

For example...

You have a NICAD battery rated at 1-amp hour (voltage is irrelevant).

You can charge this battery at 0.1 amps for ever without damaging it.

So..

1) Use an amp meter to measure the current your radio draws on standby from its battery pack. Your charge current must exceed this if the battery is to remain charged all the time.

2) Use ohms law to calculate the correct resistor to charge your battery with.

Say you have 3x 1.2 volt Nicads in your radio, (3.6 volts) and you want to charge it from a 13.8 volt motorcycle battery.

13.8 - 3.6 = 10.2 volts.

Measured current = 0.028 amps (28mA)

V = IR

So the required series resistor would be 364 ohms.


That is to say, you can put a 364 ohm resistor from Motorcycle Batter POS to NICAD battery POS, with negs all joined, and the battery will charge at 28mA.

As long as the battery pack has an amp-hour rating exceeding 280mA/Hr this is safe, as even with the radio turned off you will not exceed the battery acceptable charge current.

You wont actually be able to buy a 364 ohm resistor, Just buy the next one up or down and try it.