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-   -   Expensive vs Cheap Amp Meters (http://www.cruisersforum.com/forums/f14/expensive-vs-cheap-amp-meters-142311.html)

Snore 05-03-2015 06:43

Expensive vs Cheap Amp Meters
 
After reading the outstanding guidance of Maine Sail and others on CF, I am about to install a SmartGauge.

This gauge is great but it will not show connected load. The existing ammeter is shot and several large power users are wired (with fuses) off the house battery.

My current plan is to add a shunt between the engine (system ground) and the common battery ground/DC bus ground. Then connect an ammeter.

This will let me see current DC load on the system.

Question to the "team". What is the difference between a $125 ammeter and shunt vs. a $30 meter and shunt------ okay aside from $95.

Why not go with the low bid item??

Thanks


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wingless 05-03-2015 06:48

Re: Expensive vs Cheap Amp Meters
 
Here is one for $10.

Post links to the two products to permit a better comparison.

Snore 05-03-2015 10:05

Expensive vs Cheap Amp Meters
 
The iPhone app does allow for links.



But generally what is the difference between any amp meter from blue sea or defender vs the $10 one you found on eBay.



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Stu Jackson 05-03-2015 10:13

Re: Expensive vs Cheap Amp Meters
 
The difference would be the quality of the shunt and the meter. Without being able to see the ones you're comparing (and I understand your inability to provide links) there's pretty not much more we can say.

The only other difference I can think of is the RANGE of the ammeters. The ones with built-in shunts are less expensive, but would have a smaller range.

Ammeters & Shunts 101 Ammeters & Shunts 101

So you have to figure out how much current you're planning to measure.

For example, we have a built-in 0 - 25 A ammeter that measure output of our distribution panel. If I turned every single DC load I have connected to the panel, it would be hard to exceed the 25A.

OTOH, that meter would be toast if I placed it where you're planning yours, because I have a 100A alternator (OK only sees 50A when charging) but our shorepower charger can get up at 75 A on startup on a discharged bank.

Plan accordingly.

Good luck.

sailorchic34 05-03-2015 10:31

Re: Expensive vs Cheap Amp Meters
 
While not a cheap amp meter, I have a cheap $10 volt meter that is almost 2 years and still reads the same as my VOA meter.

The $10 amp meter is direct from china, the defender unit has probably an importer and distributor markup as well as defenders mark up. So $10+$20+$40+$60 = $120.

Myself I've found the $10 volt meter well made. One day I'll splurge on a $10 amp meter.

Snore 05-03-2015 15:24

Re: Expensive vs Cheap Amp Meters
 
Finally got home and did some research


This is the Defender Ammeter Defender.com Search Results: digital ammeter


Here is an eBay one for $38 DC 5 40V 0 100A Volt Amp AH Power Combo Meter Charge Discharge Battery Monitor | eBay





And one for $26.50 http://www.ebay.com/itm/DC-150A-200V...item2a30ea87c0

Aside from being openly Chinese (vs rebranded)


What is the difference??


Thanks

Sailorman Ed 05-03-2015 19:12

Re: Expensive vs Cheap Amp Meters- shunts
 
Question - do shunts add resistance to a circuit? And does adding a second shunt in series have any effect?

travellerw 05-03-2015 19:35

Re: Expensive vs Cheap Amp Meters
 
Quote:

Originally Posted by Snore (Post 1766410)
Finally got home and did some research


This is the Defender Ammeter Defender.com Search Results: digital ammeter


Here is an eBay one for $38 DC 5 40V 0 100A Volt Amp AH Power Combo Meter Charge Discharge Battery Monitor | eBay





And one for $26.50 DC 150A 200V Current Voltage Combo Meter Battery Monitor Charge Discharge | eBay

Aside from being openly Chinese (vs rebranded)


What is the difference??


Thanks

You should search the forum about that Chinese meter. There was a post a couple of months back about that exact amp meter. The post could not get the amp meter to be accurate. Another user was trying to help him as he had just installed the exact meter.

I can't seem to find the thread right now.

DeepFrz 05-03-2015 19:35

Re: Expensive vs Cheap Amp Meters
 
Yes, shunts do add a small resistance to the cct. They are just highly accurate, high power, low resistance resistors. Adding a second one in series shouldn't be a problem, although I don't think I would do it. Some people have one in the positive lead from the alternator to read the alternator current directly. That is effectively in series to the negative side shunt for a battery monitor.

travellerw 05-03-2015 19:39

Re: Expensive vs Cheap Amp Meters
 
Found it.. 3 pages of information about that particular meter..

http://www.cruisersforum.com/forums/...or-137003.html

wingless 06-03-2015 03:53

Re: Expensive vs Cheap Amp Meters
 
Quote:

Originally Posted by Snore (Post 1766410)

The Blue Sea Systems 8236 Ammeter is a quality marine gauge w/ a list price of $245. They also offer a positive-side shunt for $46 to permit measuring from the positive side instead of negative side.

The $10-$38 Chinese meters are not marine parts and provide functionality.

All should work.

My prior experience w/ Blue Sea System products is positive and I wouldn't hesitate to use / recommend their other products.

Saving money is good, so a cheap Chinese device for $10-$38, versus a qualtity product for ~$200 is worthy of consideration for some applications.

Ex-Calif 06-03-2015 04:07

Re: Expensive vs Cheap Amp Meters
 
Quote:

Originally Posted by Snore (Post 1765869)

This gauge is great but it will not show connected load. The existing ammeter is shot and several large power users are wired (with fuses) off the house battery.

I have been on the hunt (on CF and elsewhere) for the elusive positive and negative recording amp meter for less than $100 for months. No one has given me a straight answer that their amp meter will do it.

I opt for the smartgauge, due to superior SOC monitoring and added BMV702 only for the amp recording.

Quote:

Originally Posted by Snore (Post 1766410)
Finally got home and did some research
This is the Defender Ammeter Defender.com Search Results: digital ammeter


Here is an eBay one for $38 DC 5 40V 0 100A Volt Amp AH Power Combo Meter Charge Discharge Battery Monitor | eBay

And one for $26.50 DC 150A 200V Current Voltage Combo Meter Battery Monitor Charge Discharge | eBay

Aside from being openly Chinese (vs rebranded)

The defender one is too expensive

The $38 appears to record but does not appear to negative range. i.e It will record the amps going out of the battery for example but not amps going in. So if you drew 120 amp/hr one day and produced 100 amp/hr of solar it would report 20 amp/hr? The next day you drew 100 amp/hr and produced 120 amp/hr it would report 0 a/h not -20 amp/hr? - I don't know but that is the thing no one can tell me.

The $26 one does not record but it does negative range.

If you just want to know the immediate volts and amp draw the $26 one appears to be it. I sure wish I could find a recording one.

Maine Sail 06-03-2015 05:04

Re: Expensive vs Cheap Amp Meters
 
Just one caution....

Be sure your shunt can handle the system loads for where you place it in the system. I have seen undersized shunts get whacked with high current and lose accuracy and in one case actually lose solder.......

If your highest system load is your engine cranking circuit you want a shunt that can handle that with ease. If it is a bow thruster, electric winches, windlass etc. it too needs to handle those with ease... Most reputable Ah counter manufacturers ship 500A rated shunts and most often 50mV.

To me one of the best values, for what you get, is the Victron BMV-700....

rwidman 06-03-2015 06:29

Re: Expensive vs Cheap Amp Meters- shunts
 
Quote:

Originally Posted by Sailorman Ed (Post 1766611)
Question - do shunts add resistance to a circuit? And does adding a second shunt in series have any effect?

Yes. The meter determines the current through the shunt by measuring the voltage drop of the shunt and displaying it as current. It's a small resistance though.

Maine Sail 06-03-2015 12:25

Re: Expensive vs Cheap Amp Meters- shunts
 
Quote:

Originally Posted by Sailorman Ed (Post 1766611)
Question - do shunts add resistance to a circuit? And does adding a second shunt in series have any effect?

A 50mV X 500A shunt will impart a 50mV drop (0.05V) at 500A. At normal house loads it is at the opposite end of 50mV...


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