12v buck boost to keep tait charger happy

I have for many years struggled to get our tait VHF radio chargers to run happily off nominal 12v battery supplies. They seem to go into ‘error’ state (orange light) on power-up / when a battery is inserted. If you can convince them to start charging, they charge to completion, but there must be some 1-off ‘power good’ check at the start that they fail when the supply voltage does not meet their expectations. The same charger / radio combinations work fine off AC with the supplied adaptor. The radios come with a 12v ciggy lighter lead, so are clearly intended to run off a 12v vehicle supply.

My theory is that either:
a) they don’t like overvoltage or undervoltage. That’s to say a vehicle that is running or a 12v solar system during daylight seems likely to cause a fail. Likewise they do not like under-voltage - e.g. our hut 12v solar-based systems in winter where the battery voltage is often in the low 11.Xv range seem to fail all the time.
b) But as a second possibility - this could also be triggered by ripple or other noise on the input ‘DC’ from the solar regulator / vehicle.

So, I was wondering about trying a cheap 12v buck-boost system to ensure I supply 12v. This would need to be a boxed, commercial device as it’s being used in a ‘workplace’. And it would need to be RF-quiet so as not to disturb my evening HF nets and park activations from our backcountry huts.

Any recommendations or thoughts?

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You could check this with lab power supply.
Ripple is slightly more difficult to generate, when you want it :slight_smile: When you don’t want it, it’s there for free :frowning:

But on the other hand, you say

The manufacturer must surely have known that vehicles have their motor running from time to time and that thus the board voltage is higher. Also vehicle power are not too clean either.

Just my 2c.

73 de Martin / HB9GVW

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As you know, I use Taits at Motorsport events. In my vehicle (and many ofher marshals vehicles) the Tait is the first to complain when your vehicle battery is dropping and it’s time to start your engine.

Does your power supply dip from 13.8v with a heavy start up load? Maybe just need a beefier supply, or even a leisure battery on a trickle charge.


Here you go Matt, This is what I have and have used in the field with 11.1v LiPO in the past.
Solid, metal-cased, constant 12.6V output at 4A (50w) - if that’s enough current for what you need. RF Quiet and stupid cheap price!

Quanum DC Field & Car Charger für DJI Phantom 2 Batterie (hobbyking.com)

73 Ed.


Do you want a solution for your tait that you take with you, or a general solution to be deployed?

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Do you feel the urge to pop it open and take photos, preferably of both sides of the pcb?
Interested in the chip and architecture , and if they have any noise filtering.

The Alix BB I got a few years ago was a boost chip followed by a second buck chip. I see that there are some single chip SEPICs on there now. The interesting things about a SEPIC as a step down, is that when the switch fails the output goes to zero, not to Vin - well it’s interesting when Vin is 36V

Interesting to know what is inside yours.

So you might simply need to have a “start” switch that turns on the boost convertor momentarily until the charger is up and running. After that it just runs off the battery via a schottky diode, and there is no noise.

I would probably investigate that first.

(btw this is also a valid trick to run your radio off 3 x LiIon, where RX works fine off the batts, but TX doesn’t, and you use PTT to enable the convertor.)

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@DD5LP - thanks for that - that looks exactly like what I wanted.

Now, if only I can convince them to ship to Alexandra, Otago, NZ. Frustratingly their address entry is by drop-down selection only and the list of postal towns for NZ is woefully short - missing all but one town in my region! A support ticket has been lodged.

@ZL1THH I’m after something that I can put the required connectors on (ciggy lighter, to correct sized jack), and leave one-of in all the biodiversity huts we use regularly (4-5) for our trapping work. I’m also after something I can recommend as a tried & tested solution to other contractors / volunteer groups / DOC staff who face the same issue.

The quiet-on-HF bit is for my own benefits only, obviosly!

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Hi Simon, I have no plans to open up the < €2 unit. It’s not worth taking its design to build your own as a case alone would cost more than the whole unit. Indeed expecting these units to be noisy, I bought three of them purely for their metal cases.

I have experienced several buck/boost converters that caused awful QRM across the HF bands, this one doesn’t.

Matt, sorry to hear that Hobby King doesn’t ship to your part of NZ. You may find these at AliExpress or Banggood as well - but I doubt they will be this cheap - this looks to me as if Hobby King is seriously overstocked and rather than sending them to the tip, they are selling them off.

73 Ed.

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Indeed, excellent buying as they are, and no, I wouldn’t consider copying the design.

My questions are:
a) Is there space inside to add decent filtering, and some more output electros?
b) Is there any filtering built in?
b) Are they a SEPIC convertor, i.e. when the fets fail, will the rig get over-voltaged. (This is a big plus for cheap chinese supplies when you are using >16V )

So a photo of the inside would be nice…

As an aside, here is my main 15-60Vin, 13V 25A out step down for the 100W rigs, using a (pretty nice, relatively quiet, synchronous) Aliexpress module.

Note the green ground wire from the case to the radio chassis, which is needed for best noise, even with all that filtering.

It’s also notable that it worked without that filtering and extra shielding when I was using a centre fed 40m dipole - I could just use the plain smps module. With an EFHW on HF (and I recently discovered on 2m) the filtering and shielding is needed (for noise free operation on every frequency)


Having worked through the hobbyking process to get my address approved (3 weeks) I found that the shipping for 4x $4 buck-boost dcdc converters was over $100!

So back to looking …

The price of living in paradise!

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I use a 0-140v Variac (Powerstat) for that and for slowly bringing up long idle antique radios in hope of saving the electrolytics.

Elliott, K6EL