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tombrdfrd66
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RB433AH voltage monitor

Wed Mar 07, 2012 11:51 am

Has anyone any observations on the accuracy of the voltage monitor on the RB433AH?

I see it was briefly touched on in another forum:

http://forum.mikrotik.com/viewtopic.php ... ge+monitor

As I have a 433AH on a purely solar site I have been logging the voltage monitor readings every hour, and been somewhat alarmed when it has been down as low as 11.4v around dawn given that the 433's minimum voltage = 12v. So on a visit to the site I checked the batteries with a volt-meter and compared it with the log.

Volt meter = 13.25v
RB433AH = 12.7v

The RB gets its power from the batteries via PoE over around 4 metres of cat5e.

When you're dealing with 12v batteries half a volt is no small thing, so is the RB433's system health volt meter showing something other than raw voltage or is it just woefully inaccurate and unreliable?
The more I know, the more I know I don't know.
 
readycool
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Re: RB433AH voltage monitor

Mon Mar 12, 2012 3:23 pm

Did you try to measure voltage on the batteries and at the end of the cable?
That would give you answer is voltage on the RB same as voltage on the batteries and if yes you can calibrate RB.
 
tombrdfrd66
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Re: RB433AH voltage monitor

Wed Mar 21, 2012 4:42 am

Did you try to measure voltage on the batteries and at the end of the cable?
No. Trying to put the pointy bits of a volt meter on the correct bits and only the correct bits of an RJ-45 is beyond the capabilities of my shaky, ancient, feeble and ague-ridden fingers.

The voltage meter on an RB433 AH can be calibrated?
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popcorrin
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Re: RB433AH voltage monitor

Wed Mar 21, 2012 6:53 am

In my experience the voltage monitors aren't very exact and I think Normis said you shouldn't rely on them for an exact voltage.
Also, I have never heard of being able to calibrate them.
 
readycool
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Re: RB433AH voltage monitor

Wed Mar 28, 2012 10:35 am

I really ment that you read voltage at the end of the cable and read on RB so you can compare them and always add fixed value depending on those two.
 
mlkr0
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Re: RB433AH voltage monitor

Tue Sep 04, 2012 12:20 pm

Hello,
anybody knows if a voltage reading lower than 8V triggers a "system shutdown"?

Is it possible to disable this functionality ?

Thanks
 
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janisk
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Re: RB433AH voltage monitor

Thu Sep 06, 2012 11:31 am

all RouterBOARD devices has protection that will turn off the power if voltage is too low, that is hardware feature and cannot be configured to lower value, other way you can damage the hardware.

Voltage monitor is not very accurate as it is not testing equipment as your multimeter/voltmeter is. Older models of RouterBOARD devices had monitoring circuit that where prone to temperature (reading could be impacted by temperature) on newer devices that circuit is replaced.

for RB433AH it is reliable in a sense, that if you know what router is displaying and ambient temperature and you know what voltage was at this reading - it will always display same reading at same actual value.

Also take into consideration that router was calibrated using Pext and PoE protection chain has 0.5V drop.

In many examples I have seen in the forums it is advisable to use 24V (2 batteries in series) as over-voltage protection will turn power off at ~28V
 
mlkr0
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Re: RB433AH voltage monitor

Thu Sep 06, 2012 3:03 pm

Thanks for your answer. Is the minimum voltage reading for working 8.0 Volt ?
My problem is that I'm using a 12V battery, RB433 AH reads it with an almost -3 Volt offset, so when battery reaches 11.0 Volt, RB433 reads 8.0 Volt and shuts down...
 
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janisk
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Re: RB433AH voltage monitor

Thu Sep 06, 2012 3:15 pm

voltage red from /system health is in no way connected to low voltage protection. Actual value is not known as that depends on parts specification that can have some dispersion of values.

If router is shutting down due to low voltage my suggestion would be to get bigger battery (one that can last longer) Or or go with 2 batteries in series to double the voltage, just be careful, as over-voltage protection will kick in at ~28V (28V is guaranteed to work)
 
mlkr0
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Re: RB433AH voltage monitor

Thu Sep 06, 2012 3:29 pm

voltage red from /system health is in no way connected to low voltage protection.
This is what wanted to hear !
Thanks
 
tombrdfrd66
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Re: RB433AH voltage monitor

Sun Sep 23, 2012 1:07 pm

just be careful, as over-voltage protection will kick in at ~28V (28V is guaranteed to work)
Will the board reboot when voltage drops below 28V again or will it stay off until it's physically disconnected and re-powered?
The more I know, the more I know I don't know.
 
tombrdfrd66
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Re: RB433AH voltage monitor

Sun Sep 23, 2012 2:21 pm

In many examples I have seen in the forums it is advisable to use 24V (2 batteries in series) as over-voltage protection will turn power off at ~28V
Forgive me janisk but is this really what we want? I've already had my entire network brought down when a gateway router on top of a mountain turned itself off in the middle of the day because the solar input to two batteries in series topped 14v.

I know next to nothing about electronics. Is there a device that can sit between the batteries and the routerboard which will cut in at, say, 26V and stop the voltage to the boards going any higher?
The more I know, the more I know I don't know.
 
patrickmkt
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Re: RB433AH voltage monitor

Sun Sep 23, 2012 2:39 pm

I know next to nothing about electronics. Is there a device that can sit between the batteries and the routerboard which will cut in at, say, 26V and stop the voltage to the boards going any higher?
Yes you can find plenty of devices. From the simple zener diode that will drop the voltage (but not really energy efficient), to more costly DC-DC converter that will keep the same output voltage over a wide input range. Cost range from less than $5 to $100 for a few A currents.

You can even find some solar panel charge system that are already including these regulators.
 
tombrdfrd66
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Re: RB433AH voltage monitor

Mon Sep 24, 2012 12:33 am

Thanks Patrick.

I'd already pondered a DC-DC converter but was put off by the warning of the heat they produce - using expensive solar power to heat the atmosphere seems counter-productive.
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janisk
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Re: RB433AH voltage monitor

Mon Sep 24, 2012 11:33 am

when voltage drops router should boot up and start working again. Same applies for undervalue - when voltage rises - board should boot up when voltage is high enough to work.
 
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nz_monkey
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Re: RB433AH voltage monitor

Mon Sep 24, 2012 1:07 pm

I know next to nothing about electronics. Is there a device that can sit between the batteries and the routerboard which will cut in at, say, 26V and stop the voltage to the boards going any higher?
What you need is a MPPT Solar Charge controller.

e.g. http://www.aasolar.co.nz/Tracer%20Solar ... llers.html

This converts excess voltage from the panels into extra current, charging the batteries faster but maintaining a nice stable 12 or 24 volt output.
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