12v Charging of ICOM M31 Handheld vhf

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JustMelfort

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I plan to install my ICOM M31 (with li-ion battery) 'permanently' connected to the 12v DC battery supply. In this way I hope to find some battery life in the set when I need it! Can I connect directly to 12v or will I need some form of regulated supply? Also, has anyone come across a charging base that can be mounted on a wall - the base supplied with my ac charger is horiziontal.
 
The Icom M31 uses a BP-224 Ni-Cd BATTERY PACK 7.2 V/750 mAh Ni-Cd battery pack according to the manual so you cannot connect it directly to 12v - well you can, but..... phut! You need a 12v ciggy adaptor (supplied with the radio?) or why not use a BP-224 Alkaline pack and remove it when not in use?

I have no idea about the effect of leaving the unit on permenant charge but personelly I would not think it was a good idea.

I would suggest you contact Icom Uk and ask their advice rather than risk damage to the radio or battery.
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"Artificial intelligence is no match for natural stupidity"
 
I have an Icom M31 which I charge using a 150w inverter which fits into the 12V supply via a cigarette adapter. Don't know about leaving it permanently connected though. Doesn't sound like a good idea.
 
If the batteries are 750mAH 7.2 volts then you can charge the batteries by connecting a resistor between the 12v supply and the charge socket. (or direct to the batteries)
The resistor value is predicated on 7.2v of the battery subtracted from 12v of the supply is 4.8volts to be dropped. The charge current is a max of 10% of the battery capacity so 75ma or .075amp. Ohms law gives a resitor value of (R=E/I) 4.8 divided by .075 = 64 ohms.
Now because you may be charging the battery with engine running ie 14volt supply that value should be around 80 ohms. If you choose a lower resitor then it will recharge faster but may damage the batteries if the charger is left connected for more than a day. The 10% of AH capacity is predicated on recharge fully in 14hours. ie 10 hours plus 40% for inefficiency. If you transmit a lot then a higher recharge rate may be good but if it is mostly just listening then about 80 ohms is good. Note that these calculations are based on no drain on the battery so if the receiver is always on when it is recharged then you need perhaps 40 ma for power to the receiver so a resistor in the area of 50 ohms may suit. If the battery seems to go flat over many hours of listening even when on charge then fit a smaller resistor down to 40 ohms.
If indeed you have Li Ion batteries then they do not like to be overcharged so a value of 70 ohms would be safest and only charge it with the receiver on. (and occasional transmit) If you are feeding the 12 volts into a charger base in place of a plug pack transformer then the charger circuit should look after the battery and a resistor of about 40 ohms should suit.
The resistors come from any electronics shop and should be rated at 5 watts. (of course you may need to buy a suitable plug to go into the set.
good luck olewill
 
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