View Full Version : Introduction and hardware question

Sat 15th Dec 2018, 16:25
Hello Folks,

I've been away from ham radio for awhile, and I'm restarting over the Christmas holiday. I'll be running my Yaesu FT-817, and I'm considering an automobile jump starter for a power supply. I'm certain this has been done before, so I'm wondering what pitfalls might befall me? Also, what is a good connector to replace the battery clips?

Thanks, Tom

brandon lind
Sun 16th Dec 2018, 07:01
Jumper pack with internal battery, that might work, but Id rather just get a good deep cycle battery in that case. If it is a charger you wish to use as a power supply, be very careful. I recently purchased a 25A EverStart Plus (red and black in color) from walmart, absolutely worthless as a PS.

Here's the problem. Those battery chargers are being cheaply manufactured using switch-mode architecture and have very poor filtering (and usually no shielding). These things are good at sending wide-band noise out onto the ac power cord and the 12v leads because they lack proper filters and operate using square waves that are rich in harmonics. They don't care about quality control. The one I had from walmart was so bad it completely annihilated my receive capability. In fact, it was so bad that I opened it up out of curiosity and found that the morons had put the ferrite beads on the source pins of the switching mosfets rather than on the gates. It wont suppress unwanted oscillations on the source pin (doh) and rather than fighting the copious amounts of glue holding the ferrites in place, among the other issues, I just scrapped mine.

Be careful with the old-school chargers too, many were unregulated and the specs on your radio only allow a voltage deviation of 15% from 13.8V. The radios internal regulator might not appreciate the stress.

The FT-817 is a 5W radio that consumes (per the manual) a mere 2A on transmit.

Something like this maybe? Its output is high enough if you decide to run a bigger radio in the future and costs less than a walmart battery charger!
https://www.ebay.com/itm/Ham-Radio-Adjustable-Switching-Power-Supply-13-8V-33A/123508835529?hash=item1cc1b344c9:g:vQIAAOxyni9TD8h 1:rk:3:pf:0

EDIT: Check out the Anderson Powerpole for the connector inquiry, I like them

Sun 16th Dec 2018, 15:34
Hi Brandon,

Thank you for the reply. I'm not planning to use a battery charger as a power supply. My reason for choosing the jump starter over a deep cycle battery is convenience. They are small, clean, easy to handle, safe to carry in a pack (with precautions), and have a built-in 110V charger which I shall unplug when the battery is in use (outdoors portable operation, nowhere to plug it in if I wanted to). Once I replace the battery clips with a connector that cannot short while in transit, I think it will work well.

As for home station use, I have a Swan SS200A with Swan power supply. This is a modern, solid state radio :smug:. But seriously, I replaced the power transistors not too long ago, and the radio works well. It has no tubes to get gassy. I'm just more interested in portable QRP operation.

Take care, Tom

brandon lind
Sun 16th Dec 2018, 17:24
I can't think of any reason that wouldn't work... Those little SLA batteries you might find in a vexlar depth finder would also work well for that purpose, but they dont have built in chargers. I think the jumper pack would do well in that situation.

73, KE0KOY Brandon

Mon 17th Dec 2018, 02:14
I think the jump starter would be a good choice. I would look at Anderson PowerPole connectors as a power connector. I don't know what size wire is used on the jump starters but they have a 45 amp connector that fits up to #10 wire and they are a convenient to use. Don't forget to put a fuse in the line.


Wed 19th Dec 2018, 11:28
Lifespan used to be the issue using a high current, short duty cycle battery instead of a lower current long duty cycle RV style battery. Has this changed?

brandon lind
Wed 19th Dec 2018, 17:25
Its my understanding the lifespan of the "starter" batteries over the deep cycle ones is a function of plate thickness and erosion during charging. More current requires more surface area, and for that reason, starter (and jumper pack) batteries have thinner plates to accommodate more plates. I can see this being an issue when operating something like a 20A radio that leads to the battery being cycled more often, but I cannot imagine a 2A radio being used occasionally leading to the requirement of repetitious charging. I know letting a partially dead battery sit for long periods leads to sulfation (the buildup of insoluble sulfate crystals on the plates which leads to less effective surface area and diminished electrolyte molarity), but for the desire of a sealed, self-contained setup being used on a little 2A radio, I see it cost effective with respect to convenience and safety. For that reason, I stated it should be fine. You make a valid point, and if he uses the pack heavily, it will not survive long.

Sat 29th Dec 2018, 20:32
I think you ought to read the OP's first post. I take it he wants to use a lithium jump-starter battery pack. No lead-acid battery concerns, starting vs deep-cycle, etc., etc.

He is right that the lithium pack is small, light-weight and clean. Probably perfect for portable requirements. The voltage will be a half-volt or so higher than a lead acid battery but that won't cause a concern. Some packs (I have an Earth-X) have a USB port for charging your 'phone. Will work fine at any temperature that a sane person will be outdoors.

Should do very well.