28v Over-voltage protection - Just say NO!

Hardware MikroTik hardware general
1

I’m pulling my hair out and wasting all kinds of money on voltage regulators to make sure my solar and dc-powered sites don’t cause mikrotik routerboards to go into over-voltage protection when the batteries get charged over 28v.

I’m begging (and asking for you to join me) Mikrotik to:

  1. Upgrade the over-voltage protection to 30v or higher on 24 volt products.
  2. Never EVER make another routerboard that runs has over-voltage protection at 28v
  3. Change the over-voltage behavior to cause the device to reboot when the voltage drops to acceptable levels, instead of requiring a power-cycle to bring it back to life.

Will you join me on this and let Mikrotik, your distributor, etc. know your thoughts on this? This is not a new problem, it has been discussed repeatedly on the lists and forums.

Thanks!

2

for new products that we are designing now, we will try to go with 30V limit.

3

Thank you!

I got a reply from Mikrotik support about this subject and he said something I didn’t quite understand - maybe you can enlighten me?

“You can add LED for the power, it will increase the edge to +0.6V.”

What does this mean? Turn on all the LED’s on the board?

thanks,

Randy

4

Can you post full answer from support? Right now you turn off OVP and feed all RB up to 30V DC of course on your own risk :slight_smile:)

5

I think they mean you can add a LED in series between your solar output and the routerboard input.
The LED will drain the voltage by 0,7 V (but it will use some milliwatts of power of course).

So you can e.g. add 3 LEDs in series, to drop the input voltage by 2,1V.

6

Full quote:

Thank you very much for your suggestion and concern.
Right now we are not ready to change the behavior of the overvoltage, probably
we will improve our future products for the newer boards.
You can add LED for the power, it will increase the edge to +0.6V.

Regards,
Sergejs

How would you turn off OVP?

7

Nearly from power Jack you can find SO8 package with 9576 label. Solder tiny wire between 1 and 8 pin. ( First pin marked with dot )


8

Thanks. On my RB411 that is labeled Q801. Is that correct? And by the “dot” do you mean the indentation on the top of the eeprom?

Don’t know that I’m going to do this with stuff I already have in the air, but it is a useful tidbit for future reference.

9

A followup on the LED suggestion. Quoting from the Mikrotik Support guy:

I’m sorry for the incorrect information on the previous e-mail.
You should do the following,
cut positive wire from the battery and add diode like this
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=STPS8H100FP-ND

(reverse voltage at least 40V, forward current at least 2A, forward voltage
drop 0.6-0.7V) or similar diode.
It should help to improve current behavior.

I bet I can get one of those into one of these pretty easy for poe-powering the devices:

http://www.cablesnmor.com/rj45-coupler.html

Maybe I’ll market them :slight_smile:

10

Yes, add this wire and that’s all.



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11

MT publishes the voltage ranges for the equipment, you know the voltage ranges of the solar systems YOU built, and despite them being different you did it anyways, and it was either unreliable or you needed a voltage regulator. You deploying gear have gotta learn to respect the voltage limits of equipment.

My solar systems are 12v as I know a 24v system would go to too high a voltage. The 12v can go from 10.5 to 17v. (Higher if the battery comes disconnected; as solar can be close to 20v open circuit). Running as 12v system works well for me as I’ve got plenty of other 12v stuff.

If you must use 24v, you can get dc-dc voltage converters on ebay or a variety of sources for very little money. You can also get a heatsink and lm78xx chip to build your own. I think the dc-dc converters are probably a little more efficient than the LM chip, but the chip is smaller and simpler. Get the to220 or to3 case design if you for the chip.

12

JP - I agree, removing the voltage protection is not a good idea. The dc-dc converters seem to be a good idea, but I’ve had mixed success with some of them cutting out sooner than expected (low battery conditions), some that stop regulating if amperage gets too high (like on a power cycle), and others that can handle both low battery and high amperage but are too inefficient (fans, etc).

I came up with a solution for my problem for now.

I use West Mountain Radio Rigrunners ( http://www.powerwerx.com/west-mountain-radio/rigrunner-4005.html ) to distribute my voltage and protect my devices on solar installs. Makes for a nice clean, easy-to maintain and troubleshoot install. They go up to 38 volt, even though they don’t say that in the descriptions.

I bought some radio shack 276-1143 diodes - 200V 3 amp ( http://www.radioshack.com/product/index.jsp?productId=2062578 ). I crimped a red Anderson powerpole connector ( http://www.powerwerx.com/anderson-powerpoles/powerpole-sets/15-amp-red-black-anderson-powerpole-sets.html ) on each end of the diode after shortening the diode leads a little bit. Then I put that inline between my Rigrunner positive terminal and the cable that feeds my Mikrotik device. I label the end that goes to the Rigrunner - the side of the diode without the white stripe - with yellow tape so I don’t end up putting it in backwards later.

I use one for each device. Drops the voltage around .6 - .8 volts, enough to give me the margin I need on my radios. On routerboards that are very close by and don’t have a voltage drop due to ethernet cable length, I put two of these devices in line to drop it 1.2v. I’m cleaning out the local radioshacks and building a bunch of these for future use.

Total cost - about $2.75/device.

I still do hope that Mikrotik just makes it easy in the future and engineers for 30+ volts.

Randy