I am new to SOTA (2 weeks) and wish to activate some of the hills around my area (Stirling). I have a FT-817 and am looking for advice on suitable batteries to use to provide me with a reasonable time on air. The Ni-MH battery pack that came with the rig only gives me about 30 mins TX time and I would like to extend this.
What batteries would you all recommend (for internal or external fitting) and where is a good source? Would rather use rechargables but will accept ‘one-shot’ if that is what is recommended.
Lots of people will sing the praises of the LiOn packs…but they’re probably a bit expensive for experimenting/starting out.
With summer coming on it’s probably easiest to put rechargeables in the dry cell carrier that comes with the radio. There are plenty of efficiency issues with this…but it works.
I prefer to keep the body of my 817 wrapped up with just the face showing, or covered by a transparent plastic bag. Opening it up in rain, or trying to work that catch on the battery case with cold fingers can be a problem
I use an 8 AA cell holder from maplins with a short lead (2 core mains flex)soldered directly to it to reduce the voltage drop and eliminate polarity problems. The plug is available from maplins too, I don’t know the part number but others on here do.
This setup means I can use 2300AH cells, or whatever is available cheaply. I can charge them in any charger at home or in the car. Most importantly it means that the 817, handy, gps, torch etc all share the same battery size and so can be interchangeable.
I think that there was some discussion about this on the yahoo reflector a year or so ago…It might be worth searching that.
In reply to 2E0HJD:
I have seen those advertised on the Maplin website, might try one and see how it goes. I think they had a 7.5Ah cell which weighed about 2Kg.
Glyn
In reply to M0EIQ:
Dick thanks for those tips about protecting the 817 and the battery arrangements. Cost is not really an issue so will try an experiment with different types.
Glyn
I have seen those advertised on the Maplin website, might try one and
see how it goes.
Maplin are very expensive for SLABS. Try a local electrical wholesaler (the sort that supply stuff to local electricians). They sell SLABS for burglar alarms. Make sure that what they sell you is actually new though (some pass off secondhand ones as new). 4Ah should meet your needs easily; you could probaly manage with less. There is a calculator at http://www.g3cwi.org.uk
use 300mA (RX) and 1.7A (TX 5W) for an FT817 and you won’t be far wrong.
I can recommend the sealed lead acid type batteries, some may consider them a bit heavy but they are available in a variety of capacities - pick the one that suits! With my FT817 at 5W, 2 Ahr will do a good activation, 4 Ahr two or three between charges. On my recent trip to GD one 7.2Ahr battery lasted for the whole expedition, 5 activations, 120+ QSOs plus an hour or more chatting with the locals.
I’ve got a 7.2 Ahr one resident in my rucksack, spade connectors well-taped over to avoid shorts and a fused lead (taped to the battery to avoid pulling free incidents) with non-reversible socket on which pokes out of the side of the sack. Radio power lead with matching plug connected in seconds when setting up, and no risk of wrong polarity. To charge, I use a lead with matching plug connected to an “intelligent” charger, battery only needs to come out of the sack every few months for an inspection to make sure no physical problems with it.
I use a 2.8AHr SLAB on my FT-817. This is good for at least 3 activations. Though to be honest I have never pushed it to see how far it will go. I don’t do much FM operation so if you intended to operate a lot of FM you might need more capacity.
The performance predicted by the spreadsheet Richard put together agrees with my experience. An average HF activation for me consists of about 45mins of operation. So you want to ensure you are not carrying a SLAB that has drastically more capacity than you are ever going to use as SLABs are so HEAVY! Of course that applies less with LiIon where you get typically 2x the power density for a quarter of the weight.
It’s also worth noting that some sizes of SLAB are much more commonly stocked and this means that if you want something a bit different then you might have to pay much more per AHr than the common sizes. And as others have said, Maplin is the last resort. A quick online search shows a 12V 2.8AHr can be had for £12.87 whereas Maplin want £21.99.
As they say, “you pays yer money and makes yer choice” but in this case you are going to have hump it up and down hills so choose wisely!
Further to what Richard CWI has said, you might get a decent price with a local house alarm installer. The 7.2AH units seem to be common, though with things getting ever smaller, I’m sure lower capacities will be available.
I needed 4 SLABs for multi-summit activations. I purchased 4 cheap ones from www.batterymasters.co.uk - each 3.3AH, weight 1.3kg - the cost was £32 incl VAT, post and packing. I built a charger around an L200CV chip for about a fiver. They just sit on float and get packed when I need them.
