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1-9 of 9 messages
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Alternate power supplies for the FT817
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by LA9GY4 on September 21, 2009
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Hello all!
I am relatively new to ham operating and esp. to QRP, but very keen to get my mobile rig solid.
The main problem is power for a multiday hike.
I am looking at the batteries sold as power for other devices.
For example: http://www.batteryspace.com/waterbottlenimhbattery132v5ah66whwtrail-techfemaleplugsmartfastcharger15forbikelight.aspx
While I can see that 13.2 V at 7A max is within the prescribed limits of the FT817, is there anything else I should consider as I search for alternate batteries?
73,
jay
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RE: Alternate power supplies for the FT817
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by KB3RHV on September 21, 2009
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My 817ND came with the Ni cad pack and the AA battery tray.
To get more run time and less weight, I changed over to the battery tray and use EverReady 2450Ah rechargeable AA batteries now. I also get a few more hours of run time.
The only issue with using 817ND's internal battery is it drops the output power 2.5W. If you opt to run 12V, a 4Ah or 7Ah SLA battery will do just fine and it will give you the 5W output from the 817ND.
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RE: Alternate power supplies for the FT817
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by W3JJH on September 22, 2009
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The main problem with power for an 817 while backpacking is the mass of the battery or batteries. One of the best low-mass solutions I've seen was using a small, flexible solar array (a 5 W Unisolar unit) to charge a set of AA NiMH batteries. The array was tied across the back of the hiker's pack.
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RE: Alternate power supplies for the FT817
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by LA9GY4 on September 24, 2009
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Thanks for the replies!
I have read elsewhere (including the FT817 manual) that there are some 'dangers' in using rechargeable AA batteries in the supplied unit.
Apparently this is a minor risk, or one that can be avoided with some common sense? Is it only the matter of charging which presents this risk, or is it also simply the use of these batteries in general?
For now, I have bought the OPP battery from W4RT. We'll see how I get on.
Thanks again! I love reading eHam!
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RE: Alternate power supplies for the FT817
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by KB3RHV on September 24, 2009
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The problem lies in 2 things with running rechargeable batteries in the 817.
The first one is a short circuit and having the rechargeable batteries explode. The battery pack has a fuse to stop this.
The second is the built in charger is only designed to charge Ni-Cad batteries. Any thing else, and you could pop the charger and/or the batteries.
I know a few people that run rechargeable batteries in the 817's besides me with no issues. My self, I have been doing this for a few months with no issues, as I am careful and don't use the built in charger.
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RE: Alternate power supplies for the FT817
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by W0GI on September 26, 2009
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I did two mods to the battery holder, that will prevent problems using NiMH cells. First I cut the black negative wire at the corner of the battery holder, and added a 3 amp auto mini fuse. Solder and cover with heat shrink.
The second issue I found is that the cells can scrap against the bottom cover in the recessed area. that is a short waiting to happen. To resolve that, take a dremmel to remove the lip on the bottom cover, then glue a small thin piece of plastic as an insulator.
At this point, I feel it is as safe as a pack. As for charging, I clipped the green wire, and I don't worry about using the internal charger. My other pack is a MAHA 1700 MAH NiMH and it has been fine since 2001.
All that said, I use 2000 MAH eneloops in the pack for short use, but the current draw of the 817 really calls for a gell cell for extended use. I use a 12v 7AH from Hobbytown, that costs $21.
Since I added the DSP, I am now drawing 400ma and 5W transmit current is 1.9A. I can't run for long on internals.
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RE: Alternate power supplies for the FT817
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by KU3X on October 16, 2009
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I see one MAJOR problem with the battery pack you chose from BatterySpace......Peak voltage. It's 15.5 volts peak. That is way too high of a voltage to run
any HF rig on.
Here are two suggestions for you.
http://www.batteryspace.com/airsoftgunbattery108v4200mahnimhbatterypackforairsoftmod.aspx
The above battery from BatterySpace is a 10.8 volt @ 4200 ma. I use this on my IC 703. When fully charged the peak voltage is about 12.2 volts. They make a 4600 ma version of this battery pack if you want a little more operating time.
Go to YouTube and search, "barrygkx" and you will see three videos I have posted. One uses the above battery pack. One other uses a 12 volt 7 amp gell cell. The gell cell is really your best battery to carry with you. When I set up portable for an entire day, the gell cell seems to last pretty much all day. I've used it with my IC 703 as well as my FT 817 when I had one.
One comment about power supply voltage. I will get all kinds of comments about this but bottom line is, "DO NOT operate a 13.8 volt rig on supply voltages above 14.3 volts. Yes.....I know the book says you can go up to around 15 volts, but all it does is generate more heat within the rig. I had a board melt down on a TS 480 because the supply voltage was 14.8 volts.
Have fun running portable. I do it all the time and love it.
Barry, KU3X/QRP/P
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RE: Alternate power supplies for the FT817
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by AD5X on October 17, 2009
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"The only issue with using 817ND's internal battery is it drops the output power 2.5W."
2.5W on internal batteries is the default. But you can change it to 5W on internal batteries with one of the menu settings. I no longer have an FT-817, so I don't remember the menu setting for this. Just check your manual.
Phil - AD5X
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RE: Alternate power supplies for the FT817
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by VE3WMB on October 17, 2009
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It worth mentioning that part of the secret to using the FT-817 in the field is addressing the power consumption. Part of the problem with the FT-817 is that it is a power hog on receive. For example my K1 draws about 60mA on RX whereas my FT817 draws more like 300mA. Generally speaking you spend a lot of time listening so the Rx current draw has a big impact on how long your batteries will last.
I suggest reading the following excellent web page on reducing the receive current draw on the FT-817 :
http://www.ka7oei.com/ft817_pwr.html
Note that one of the biggest draws is the non-latching relay that is powered to allow use of the rear (SO-239) antenna jack. Using the front BNC (even for HF) will reduce the current consumption by almost 30mA.
BTW I replaced my internal AA tray with a small molex connector that I use to connect a R/C NIMH pack that is modified so that both leads
are fused with picofuses to give some protection from shorts.
My packs are only about 1700 mAh but they are quite light so it is easy to bring along a couple of extras. You can buy these R/C packs at Radio Shack and I think that they still have a deal on a battery pack
and charger combo.
Cheers,
Michael VE3WMB
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