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Ampmeter Size


Richard Dowe
Hi guys, I am going to clean up the wiring around the house batteries, too many connections on the terminals. I have upgraded the wiring system and installed several fuse panels, mounted negative buss bars in few places and ran a single conductor back to another buss bar before going to the battery. With all this change the original ampmeter does not see the full current. I would like to install a shunt on the negative side of the batteries and install a larger meter. Question what size should I go with?
The loads are modest but steadily increase. Radar,radio,vhf,tv, fans,Espar heater soon to come, mascerator pump, water pump, wash down pump,microwave,inverter, most lights have been converted to LEDs, the tv only 50 watts. Any recommendations.
Thanks Rick


James M. Cleary

If you are going through the process of installing a negative shunt, you should look into a Link 10 or Link 20 system. Although I think the company was brought out years ago and is called something else now. The Link monitor will allow you to check on the battery voltage, amp hours remaining in the bank, amp use at the moment and hours left in the bank at the current usage. The one thing needed for a correct installation is only one negative shunt that Includes every negative wire both incoming or out going. The system works by reading everything that happens on the negative side of your bank. We've had a Link 10 (monitors one bank) system for 20 or so years and it has been bulletproof. Hope this helps.



Stephen Ruell
You have to match your metering instrument to the shunt. I don't think as a practical matter that there are a lot of sizes available for the shunts.

Blue Sea sells two sizes of shunts and has an article about them.


There is another website called Handy Bob's Blog. https://handybobsolar.wordpress.com
He is entertaining reading and talks about the solar installation and charging issues for folks with RV's and gives a lot of advice from his experience and as an installer. On his site he recommends a company selling this type of monitoring equipment, Bogart Engineering, specifically their TM2030 monitor and SC2030 solar charger. http://www.bogartengineering.com/products/trimetrics.html

The two Bogart units act as a system to control and monitor charging and battery usage. Bogart tells you the sizes of the shunt you can use with their monitor. There are three sizes of shunts and I bought the middle one -- 500 amp/50Mv shunt. They have one that is 100 amps but that doesn't seem like enough. 100 amps x 12volts = 1200 watts. A windlass can be almost that much so it seemed to be cutting it too close, and with your microwave and inverter you probably are going to be in a higher range too, I would think. I went with the 500 amps, seemed sufficient for what I could imagine ever needing. But I haven't got any of this stuff installed so I cannot give any experience with it yet.

I went with a Victron BMV-700, which comes with a 500 amp/50 Mv shunt. Basically the same as the Xantrex LinkPro (which I believe is the successor to the Link 10/20 that Jim mentioned above). Only difference I can tell is that installation is a bit easier with the Victron because they use a telephone style wire/plugs between the shunt and display unit. Victron also makes one that can link to your phone via wifi or bluetooth - beyond my needs but I guess kind of cool? Like everything else these days probably selling your data off into the ether...

These two seem to be the current standard for most recreational boats, but if you need more than 500 amps at the shunt I would guess there is probably something heavier-duty out there!


Richard Dowe
Thanks for responding, Jim I had researched that a few years ago and forgot about it!
Steve, thanks for the web site, I like reading what others have done. 500 amps sounds about right.
Keefer, there a site call Marinehowto.com, the guy is in Maine and did a good write up for Smartgauge by Balmar. More reading
Thanks for the input guys!


Terence Thatcher
All the shunts and amp meters are both complicated and, from what I have read, of questionable accuracy, especially over time. I have a Balmar Smart Gauge, which I find very satisfactory. I always know my house bank (400 amphours) state of charge. I think they have upgraded the system to provide more info, but don't know if it is better or just more complex. Read the review by Compass Marine. He knows his stuff and he endorses it.


Richard Dowe
Your up early Terry! It's nice to know of others that have this particular unit. Do you still have the original ammeter?
I have used that site as a guide for several projects over the years, agree that it is top notch. Hadn't seen that Balmar article before, will read up!