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eHam Forums => Emergency Communications => Topic started by: KD2JIP on July 18, 2018, 10:43:44 AM



Title: Seeking voltage limiter recommendations
Post by: KD2JIP on July 18, 2018, 10:43:44 AM
A quirk of my portable power setup with solar charging is that under certain conditions, the charge controller sends solar panel Voc of up to 22V to the load.  This would fry my KX2.  I work around this problem by never connecting the panel and the load to the controller simultaneously. 

I would prefer to float the battery while powering the load from the panel as much as possible. I might be able to achieve this with a different charge controller or battery pack, but I'd prefer to first see if I can find a regulator that will limit the max output voltage.

I tested this adjustable output step up/down switching voltage regulator from Pololu (https://www.pololu.com/product/2573).  It's very small, RF quiet and efficient, but its max output current is only 2A, which doesn't allow my KX2 to transmit at full power.

I also tried this one (https://www.amazon.com/gp/product/B017CNAL56/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1), which satisfies my power requirements.  But it's extremely noisy--it obliterates strong, clear signals on 20m and 40m.

The advantages of a buck boost converter are that it protects my load from panel Voc and it maintains a voltage that allows my KX2 to operate at full power as the battery discharges (although draining the battery faster).  But I'm not 100% sure that a buck boost converter is necessary--maybe some other simpler component would work.  My essential requirements are:  1) max output voltage limited to around 13.5V;  2) max output current of around 5A; 3) as efficient as possible;  4) as RF-silent as possible;  5) as small and light as possible.

Any recommendations?


Title: RE: Seeking voltage limiter recommendations
Post by: K5LXP on July 18, 2018, 03:42:42 PM

A 15V zener rated to dissipate the maximum panel capacity across the panel output is RF quiet and very simple.

Mark K5LXP
Albuquerque, NM
 


Title: RE: Seeking voltage limiter recommendations
Post by: WB6BYU on July 20, 2018, 08:50:20 PM
And if you don't want to buy a large zener, use a smaller one and a big transistor together.
Such a combination can draw 20A or more (assuming you have enough heat sinking) to
load the panel down and keep the voltage within range.


Title: RE: Seeking voltage limiter recommendations
Post by: W8JX on July 21, 2018, 04:04:07 AM
How about a load bank on solar panel output too to keep it loaded so voltage does not spike high. It can be a few high wattage power resistors of proper value. It could be switched out when not needed and reduce energy needed to be dissipated by a zener.


Title: RE: Seeking voltage limiter recommendations
Post by: KD0REQ on July 21, 2018, 01:51:42 PM
Get the schematic of an Astron PS off the repeater builder site. Build the part after the filter caps. Done. The voltage max out of the panel is the voltage passed into the control board. Or just put two big-arsed diodes in an Astron cathode common, one anode back to the cap, one anode to the solar bank. Now you have a diode-switched Astron that will take the higher voltage from either source without impressing backflow into either one. Just like a big telco.


Title: RE: Seeking voltage limiter recommendations
Post by: WB4SPT on July 22, 2018, 06:33:51 PM
A quirk of my portable power setup with solar charging is that under certain conditions, the charge controller sends solar panel Voc of up to 22V to the load.  This would fry my KX2.  .

Certain conditions related to RF?  I come across numerous regulator designs, even very popular reference V IC's that are quite sensitive to RF.   But, taming is possible. 
Solve the primary issue, don't chase a bandaid. 


Title: RE: Seeking voltage limiter recommendations
Post by: AA4PB on July 22, 2018, 07:30:56 PM
No solar charge controller should ever send 22V to a 12V battery and load. It sounds like either your battery is bad or it is disconnected from the system. A solar panel can put out 22V with no load but the charge controller should limit the voltage to about 14V with the battery connected.


Title: RE: Seeking voltage limiter recommendations
Post by: N3QE on July 23, 2018, 06:30:22 AM
Normally a solar panel would feed a charge controller which feeds the battery which feeds the radio.

The battery acts as a pretty good 14V regulator.

You might want to rearrange your wiring such that the battery can never be disconnected while the radio is still hooked to the charge controller. I might recommend one set of wires from the battery to the radio, and a different set of wires (with a different plug) from the battery to the charger.

Others swear up and down that a charge controller will never put out 22V. And I agree, it would never do that to a battery. But in my experience if the battery isn't there then all bets are off. That charge controller was designed to charge a battery and not protect a radio.


Title: RE: Seeking voltage limiter recommendations
Post by: W8JX on July 23, 2018, 07:18:35 PM
The battery acts as a pretty good 14V regulator.

Only if it is a big battery and panel only makes a few amps or so max.


Title: RE: Seeking voltage limiter recommendations
Post by: AA4PB on July 23, 2018, 08:11:04 PM
The battery acts as a pretty good 14V regulator.

Only if it is a big battery and panel only makes a few amps or so max.

If the charge controller is allowing the voltage on a 12V battery to be pulled to 22V then the battery is not going to last very long. It's time for a new charge controller if yours is doing that.


Title: RE: Seeking voltage limiter recommendations
Post by: W9IQ on July 24, 2018, 04:05:50 AM
If the charge controller is attempting a current regulation phase for battery charging, it would not be unusual to see 22 volts when the battery is not present. The charge controller is attempting to raise the charge current to a predetermined level but with no load, it will reach the maximum of its supply voltage.

- Glenn W9IQ


Title: RE: Seeking voltage limiter recommendations
Post by: KJ4HVL on July 31, 2018, 11:24:17 AM
As others have stated even a small 7AH sla battery will drag down the output voltage, my panel will do 24V OC, but with even a tiny load falls to 15v. That said, I have purchased some of the DROK buck converters on amazon for my power kit (I have mine inline between the panel and the controller with a peak limit of 14.8V). They are a little noisy, so a coil of wire on the output through a ferrite, and shielding the switching module itself is important... However without those protections I've worked wspr from the US to Antarctica and Tasmania, with the only noticeable issue being the pop-pop-pop of the pwm charging circuit from my controller.

The benefit of locating it at the input to the controller, is if your controller fails, you can actually use that module as a CC / CV charge controller in and of itself, and in bright sunlight, you could probably even run a rig directly off the panel (so long as you dial back the power a bit)

https://www.amazon.com/dp/B0744BT79M/?coliid=I2WNLLPKXTEIER&colid=107GIW97E1MA2&psc=0&ref_=lv_ov_lig_dp_it


Title: RE: Seeking voltage limiter recommendations
Post by: KD2JIP on August 18, 2018, 06:56:40 AM
Certain conditions related to RF? 

No.  By design, the internal BMS board disconnects the battery when charging rate falls to 0.02C.


Title: RE: Seeking voltage limiter recommendations
Post by: W8JX on August 18, 2018, 07:35:19 AM
As others have stated even a small 7AH sla battery will drag down the output voltage,

Not that well as regulation will depend on battery charge state and it will shorten its life. If you go battery route, you want a bigger battery.


Title: RE: Seeking voltage limiter recommendations
Post by: KD2JIP on August 18, 2018, 07:40:11 AM
After further consideration, I decided to replace my battery.  I built a higher capacity pack (6.6 Ah as opposed to 4.5 Ah) using a PCM board that doesn't disconnect the battery near end of charge.  The PCM top balances the cells at 14.4V, so, unfortunately, I had to replace my 14.2V charge controller, too.  I went with the same model controller, custom programmed with a CV voltage of 14.4V.

My setup now functions as I had hoped.  The load is now exposed to a maximum of 14.4V, so I can keep the panel and load connected at all times.  This allows the controller to power the load from the panel when possible and from the battery when necessary.

I would still like to put a voltage regulator between the controller and the load, no longer to protect the load, but to keep it powered at >= 13V as long as possible when running on battery.  This would maximize the amount of time I could transmit at full power (the KX2 will transmit at its max of 12W as long as input voltage is >= 13V).  I don't know if a regulator like this is available to buy or feasible to build.  Current draw while transmitting and powering a Raspberry Pi (for digital modes) is between 2.5A and 3A;  I'm not sure if this would require a regulator with constant current...


Title: RE: Seeking voltage limiter recommendations
Post by: W8JX on August 18, 2018, 07:56:39 AM
A regulator itself is going to consume some energy so not sure if you will gain much if any with one. 


Title: RE: Seeking voltage limiter recommendations
Post by: K5LXP on August 18, 2018, 04:42:37 PM

Does your panel put out 3A?  If not, no dropping regulator will fix that, and even a low dropout regulator would have some drop vs input voltage below its setpoint, which translates to an output below battery voltage when the panel isn't pulling it up.  A DC-DC converter would maintain whatever output voltage you wanted as long as you satisfied the input voltage and current requirements of the converter.  Some are noisy but some are pretty quiet.  There would be a bit of efficiency penalty but if it allowed you to use the full capacity of the battery at whatever output power you need it might be viable at the system level.  I use a DC-DC converter this way to run a laptop at 16V, and another one to keep a 100W transceiver gel topped off from a bank of gel cells and solar.

Mark K5LXP
Albuquerque, NM


Title: RE: Seeking voltage limiter recommendations
Post by: K6AER on August 19, 2018, 08:16:14 PM
You did not mention what the output wattage from the panel is , the unloaded voltage and your battery size in amp hours. Solar charge controller for up to 20 amps can be had on the internet fore under $35. Your battery should be of a capacity to run the radio for three hours. I would suggest at least 35 amp hours.


Title: RE: Seeking voltage limiter recommendations
Post by: KD2JIP on August 21, 2018, 07:23:30 PM
Does your panel put out 3A?
Yes.

Quote
A DC-DC converter would maintain whatever output voltage you wanted as long as you satisfied the input voltage and current requirements of the converter.
This is what I want.  Any recommendation for a quiet one?


Title: RE: Seeking voltage limiter recommendations
Post by: KD2JIP on August 21, 2018, 07:47:56 PM
You did not mention what the output wattage from the panel is, the unloaded voltage and your battery size in amp hours. Solar charge controller for up to 20 amps can be had on the internet fore under $35. Your battery should be of a capacity to run the radio for three hours. I would suggest at least 35 amp hours.

I have a 60W panel.  Max Voc is 21V if i recall correctly.  I have shied away from cheap controllers because my assumption is that highly reputable equipment is more likely to be reliable than no-name, cheap equipmenti.  A 35 Ah battery is too heavy for man portable.


Title: RE: Seeking voltage limiter recommendations
Post by: KD8SKM on August 28, 2018, 04:09:48 AM
Our Apollo Charge controller would work well here with a 60 watt panel and have room to grow up to 280 watts of Solar Power.

It also pairs nicely with a 20 amp hour Lithium Iron Phosphate battery at 6.5 pounds weight... and that's a true 20 amp hour usable capacity.

Check out the controller at:  http://www.diysolarforu.com

Battery can be found from http://www.batteryspace.com
I use the 20 amp hour 12.8 volt packs for shows LiFePO4 or LiFeMnPO4.

Cheers,

Rob
KD8SKM
DIY Solar for U


Title: RE: Seeking voltage limiter recommendations
Post by: KC4ZGP on August 28, 2018, 11:03:59 AM

Oh forget that fancy-pants solar charging thingy.

Use car batteries.

Kraus


Title: RE: Seeking voltage limiter recommendations
Post by: LYFAN on February 14, 2019, 07:37:34 PM
"I would still like to put a voltage regulator between the controller and the load, no longer to protect the load, but to keep it powered at >= 13V as long as possible when running on battery."

Ain't gonna happen. You'e got something grossly wrong in the setup, and I think you are also under some misimpressions about how it can all work.

First of all, you will never have the battery powering the radio at more than 12.8 volts, which is about the maximum you'd eer see on a lead acid battery of any type. (Lithium might go higher, but that's a whole other kettle of worms.)

Anything over 12.8 volts (typically 12.6) on a lead acid battery is a float charge, which disappears after just a few minutes under any load. So, your battery is not going to give your radio anything above 12.6-12.8 volts.

Second, putting a regulator after the controller is totally counterproductive. The controller is supposed to have a regulator built into it. Either it works, so no second regulator is needed. Or it is broken--and it needs to be fixed, not kludged with a second regulator.

What you might want to do is replace the charge controller with an "MPPT" type controller. They can be 15% more efficient than pure DC simple controllers. And they may gain another 15% because they can take the low voltage in the early/late hours, or if the panels are partly shaded, and still boost it to effective charging voltage.

From what the OP is posting, there's just too much wrong, it needs to be redone right, not kludged on the kludges.


Title: RE: Seeking voltage limiter recommendations
Post by: KB8VUL on June 20, 2019, 04:47:49 AM
There are DC to DC buck converters on eBay that will take 12 to 60 volts and output a solid 13 volts at all times with a reasonable current rating.
You could design something, but if it's a shelf item from China for 10 bucks, why bother?


Title: RE: Seeking voltage limiter recommendations
Post by: KD8SKM on July 30, 2019, 03:49:30 PM
There are several issues with using a 10 dollar DC-DC converter...

1) Probably the most significant is the amount of RFI it will produce - making a DC-DC to be RF quiet takes great care in the design and selection of components along with PCB layout.

2) It will not know when the Battery is at full charge and stop charging

3) Without MPPT that converter will just pull down the Solar Panel Voltage to the minimum input of the converter - likely pulsing on and off all the while.  This results in a significant loss of power likely over 50%.

4) Reliability is another big one - 10 bucks is real cheap and will have cheap parts used in the design... probably will not last.

All of the above reasons are why I started DIY Solar for U 6 years ago and developed a Solar Charge Controller that would be RF Quiet,  have Maximum Power Point Tracking to get every last watt out of the panel, and know when the battery is full to go into standby.

Designed, and made in the USA with Automotive / Military grade components sourced in the USA.  Built to last 40+ years too.

Check us out at https://www.diysolarforu.com

Cheers,

Rob
KD8SKM


Title: RE: Seeking voltage limiter recommendations
Post by: N8AUC on July 30, 2019, 07:19:14 PM

Oh forget that fancy-pants solar charging thingy.

Use car batteries.

Kraus
That is a bad idea on so many levels, it defies description.