I am currently studying for my foundation licence and can’t wait to combine my love of hill walking with my new hobby.
I have a 40v LiPo 16Ah battery that is used on my electric cycle. I’m not suggesting taking this up a mountain as it weighs 5kg. I do however want to use it whilst camping on a site during my stay in the hills. I have ordered this ( http://www.ebay.co.uk/itm/181347093991 )to allow me to run cycle lights from the battery. However when I’m camping for several days and between activations I still want to use my rig. Could I set this converter for example at 13.8V 8A (Yaesu 857d) and operate QRP? I can’t see a problem, however damaging relatively cheap cycle lights is ok compared to wrecking my Yaesu.
It will do as it says, convert an input voltage range to an output. Things which you don’t know:
regulation: is it any good or does the output voltage jump about when the load changes
Noise: does it produce huge amounts of RF hash when in use. This may be less of an issue on TX. If it blanks the bands then it’s not much good for radio.
RF immunity: will it keep working as intended in an RF field.
Overvoltage protection: when the switcher transistors go pfffft and fail, will the full input voltage appear on the output.
How do you find out? You could ask the vendor. Whether they know or would tell you is debatable. Or you buy one, it’s only £11.50 and try it.
I realise you may be hoping for a yes / no answer. Sadly it’s not that simple.
In reply to DAVE:
hello Dave a few vk5 ops are using a similar or possibly the same voltage regulator down under.
I can’t speak for John VK5BJE but knowing what a nice fella he is I am sure he would answer questions and tell you the type he has . Search for his call on QRZ there’s an email address there.
73 de Ian vk5cz …
In reply to MM0FMF: Some interesting points raised which I didn’t consider. As I was saying relatively cheap cycle lights are one thing but risking damaging a rig is another. Think I’ll do that and contact the vendor. If that checks out I suppose the rest is trial and error. Think I’ll also contact the guy above an QRZ.
No not looking for a yes or no answer, things never seem to be that simple.
Hi, Dave, I can’t help with your query, but a couple of things about your FT857D. I can tell you that this rig is in some ways more fragile than you might think. Firstly the makers have provided it with no reverse voltage protection, a whiff of wrong polarity volts and it is dead beyond economic repair, so make sure that you cannot connect it to the power supply the wrong way around - or protect it with a series diode. Secondly, following on from what Andy said, the rig is very intolerant of over-voltage. I had a PSU regulator fail putting a high voltage into my rig and this burnt out several components, so make sure that your power supply voltage won’t swing high when the current draw is low.
It’s a great little rig to go camping with, you should have a good time with it as long as you give it the protection that Yaesu omitted to give it!
If your battery does not exceed 15 V you can run the rig off it directly.
Yes you can set the inverter output to 13.8 V and run your rig. You could set it as low as 12 V and still run the rig. Hopefully whatever voltage you choose will also suit your cycle lamp. It’s best to set the voltage once and leave it.
If you find that the battery voltage goes above 15.8 V then you do need the inverter.
If the inverter does produce objectionable hash on receive then putting it in a metal enclosure with an output filter made of one or two toroids and a couple of capacitors should fix that. Inexpensive inverters come unboxed and maybe without noise suppression.
What happens if the inverter fails?
Most likely it will appear as a short on the battery so it MUST have an input protective fuse of say 20A.
This concern about regulator failure goes back to the series linear regulators that had 18 V to 25 V dc input and failure (short) of a series element could apply far too many volts to the transceiver.
If it does fail so that it applies the full battery voltage to the output, remember most Yaesu transceivers are rated to 15.8 V. They will likely withstand 16 V but really should not be operated with this voltage. Some operators have for a few hours operated their FT817’s at just under 18 V and surprisingly the set lived to tell the tale. This is NOT something to try. They were lucky.
I avoid operating my equipment above 14 V, but if the battery never exceeded 15.8 V max then I would seriously think about doing without the regulator to save weight and complexity.
Good luck with the licence - some of our most active SOTA people in VK are foundation licence holders.
I am currently studying for my foundation licence and can’t wait to
combine my love of hill walking with my new hobby.
I have a 40v LiPo 16Ah battery that is used on my electric cycle. I’m
not suggesting taking this up a mountain as it weighs 5kg. I do
however want to use it whilst camping on a site during my stay in the
hills. I have ordered this ( http://www.ebay.co.uk/itm/181347093991
)to allow me to run cycle lights from the battery. However when I’m
camping for several days and between activations I still want to use
my rig. Could I set this converter for example at 13.8V 8A (Yaesu
857d) and operate QRP? I can’t see a problem, however damaging
relatively cheap cycle lights is ok compared to wrecking my Yaesu.
.
An excellent choice of rig, Dave. For the money, IMHO, there is nothing that comes close to the FT-857 for SOTA work. Of course, the penalty comes in the form of weight. If you’re prepared to pay the penalty, you’ll love the rig and the way it performs.
In reply to G8ADD: One of the reasons I am being cautious with using the 40v battery even though I intend to use a DC DC converter is possible over voltage. I have read in a few threads on this forum about using a diode in series and I will look into that. I have fit Anderson power poles to my equipment to help prevent reverse polarity but a diode in addition seems to be a reasonable solution.
You could always get a battery for the 857 and charge that from the bigger battery. When you wish to operate, disconnect the charging system and power the radio from the separate battery. More to carry about etc. but you don’t need to worry about over voltage and if you size the radio battery correctly you can use it portable with the 857 for activations.
In reply to AX3AFW: Going to use the above converter for lights but decided against this one for the rig. Can’t get any Guarantees. I have read previous threads about using LiPo batteries on this forum. Think the plan is to initially purchase something for summit activation which I can also use in my future Soln1 project. I may pursue that project for now as the battery can be charged whilst in use when on the camp site. Think I need to find a regulated DC DC converter. Only ones to date are 24v meant for trucks. No hurry though, sure something will turn up.
Check out your QRZ page and I see that you use the same rig. Interesting choice of antennas.
After a lengthy search at what seems like a never ending choice of gear, I chose the 857. I live in a small flat so this rig is literally a do everything rig. My shack is the kitchen so the removable front means that I can move into a different room when needed. The power selection gave it the edge over the the 851 for home use. I’m happy with it. Only change I’m planning to make for home is to plug a larger diameter speaker in for better sound. So this rig will be used for home, car, SOTA/field work. Can’t ask for more!
Oh you have a 40 V battery. I read 40v as a part number. Sorry. A simple crowbar circuit set at 15 V to 16 V would protect from over voltage. A 15 V zener and a high current transistor would do the job.
LiFePo4 batteries with 4 series cells and a matching balancing smart charger are the way to go for powering radios. They are heavier than straight LiPo types but have a flat discharge curve and are virtually a direct substitute for the lead acid type of chemistry batteries. Prices are OK if you can find some on special, otherwise not cheap.
40 V is a bit high for most inverters on the market. Keep looking.
Linear regulators would do the job but you waste a lot of energy in heat.
A diode in series with the power lead will only reduce the voltage by 0.6 V to 1 V maximum. Several diodes in series enabled LiPo batteries to be used until their terminal voltage dropped to 15 V when the diodes could be bypassed.
According to the ebay listing, this is a switch-mode step-up (boost) module. This type of circuit will only generate an output voltage that is higher than the input voltage. It will not work to generate 13.8V from 40V. To do that you would need a step-down (buck) module.
As has been said already, the biggest problem with switch-mode modules is the large amount of RF (and sometime AF) noise they make.