Icom M31 VHF

[PeteCooper]

I have just noticed that on the battery holder of my Icom M31 it specifically states : "NEVER use Ni-MH batteries otherwise a fire hazard or damage to the transceiver may occur." I had planned on using Ni-MH batteries, so can anyone tell me in very simple terms why these are different to 'ordinary' batteries? Thanks, Pete.

 

[Blue5]

I have just bought an M31 thanks for pointing it out, very difficult to see on the casing and not mentioned anywhere in the literature. I assume it means dont use re-chargable batteries Nmh or nicad, sure someone will enlighten us

 

[Brian_Moffat]

The Icom re-charging circuits are designed for NICAD cells only. All NICAD's have a particular charging current which is limited to around 20% of the cell Ampere/Hour discharge rating.

NIMH cells have a very high charge dump capacity (i.e. Extremely Fast Charging Capability) and require a completely different charging regime to NICADS. They also require totally different charging circuits and extra monitoring of the cell.

The warning is given to protect the ICOM charging circits from being overloaded by use of a set of cells that they are not designed to operate.

Remember - high charge/discharge rates cause a lot of heat (Have you ever overvolted your on-board batteries and felt the temperature?)

NIMH cells can and do generate high temperatures within the cells at high charge/discharge rates and, whilst it is not known for them to actually catch fire, there are some recorded instances of "smoke issuing" and damage to surrounding plastics which do not have a high temperature capability.

Hope this helps

regards

brian

 

[Blue5]

Hi. thanks Brian but one more question. On my M31 it reads
"Use alkaline batteries only. NEVER use Ni-cd or Ni-MH batteries otherwise a fire hazard or damage to the transceiver may occur."
The M31 originally had a Ni-cd battery pack with Li-ion option so why would it be OK to use a Ni-cd main battery pack but not 6 x AA ni-cds as the back up option
I have never seen this warning on any other product and both my handheld GPS that I have had for years work with AA batteries, I have used alkaline and rechargeable Ni-cd and ni-mh with no problem.

 

[PeteCooper]

Thanks Brian. However I do not have an Icom charger, so the batteries will only be charged away from the VHF unit and then refitted. Is this a problem? Thanks again, Pete.

 

[Blue5]

Have spoken to an ICOM agent who tells me this is more to do with the fact that ni-cd and nmh rechargeable batteries will not achieve 100% recharge power and therefore may not function properly when in emergency at 5w output

Seems plausable

 

[guydickinson]

I have an ICOM M31 and the bl***y NiCd battery was running down in no time at all. The local chap here said he's just had a supply of new Li ion batteries with new charger thrown in for £49 - have got it and I am hoping it'll be a lot better!!!