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profdant139's avatar
profdant139
Explorer II
Dec 14, 2021

Simplest battery monitor and shunt? Advice for non-expert

I have seen references in various threads to shunts and battery monitors. I have searched the archives for a very basic "how to" and have come up empty. Youtube has some instructional stuff, but it tends to be fairly technical.

A little background info -- my battery sits in a box on the tongue of my trailer. I am not an electronics expert at all. What I am looking for is a fairly easy, fairly inexpensive way to monitor the capacity of my battery on a real time basis.

I'm guessing that I will have to install the monitor inside the trailer and run wires to a shunt installed on the negative cable near the battery.

In your opinion, which is the most basic and inexpensive monitor? Are shunts sold separately from the monitors? What gauge cable does the shunt/monitor require?

Thanks in advance for your advice and expertise!
  • profdant139 wrote:


    In your opinion, which is the most basic and inexpensive monitor? Are shunts sold separately from the monitors? What gauge cable does the shunt/monitor require?



    I use this Voltminder and a battery state of charge chart. You can set an alarm on it if wanted. I bought mine direct from Voltminder, but Amazon sells them too, just you get free freight if you buy direct. They charge freight on Amazon. It is the same seller.

    http://www.voltminder.com/

    I use this chart off the Trojan web site, scroll down to the voltage chart. https://www.trojanbattery.com/tech-support/battery-maintenance/

    Take note, the battery needs to be at rest (not charging and no practical power draws) for 6 to 8 hours to not have a surface charge that can be misleading (false high voltage). It talks about this just above the chart.

    It has a 12 volt cigarette charge plug if you have a socket in the camper or your can hard wire it in. Ideal is to tie in close to the battery inside the camper if possible to avoid a long run voltage drop.

    While this does not count coulombs like the Victron,(a very good feature) knowing good voltage readings and understanding what they mean, works for us while boondocking. It simple and it is close enough on SOC. Everyone has different needs when it comes to battery power draw measurement.

    I do not have the need for an inverter (yet anyway) and I can manage our 12 volt power draws to minimum. If I end up getting an inverter or solar some day, then yes I would go the Victron route.

    Hope this helps,

    John
  • Basic, inexpensive monitor no shunt,This One nothing fancy but tells me what I need.

    I have one for the Chassis and one for the house batteries.
  • Lots of great ideas in a very short time -- thanks! Keep the suggestions coming -- I can see that I have more homework to do. (I bet I'm not the only one who finds "RV homework" to be more fun than "home homework.")
  • Probably the simplest option is the Victron Smart Shunt for ~$130.. The whole unit resides in the battery box with no holes to drill or wires to run. The output is viewable on any phone/tablet/computer. Victron also makes a version with a hardware display if that is important to you.


    There are cheaper no-name options, but they have several drawbacks - they need to have the display installed and wired up, they are less accurate and most importantly, they only provide a snapshot of what is going on right now without any history. The Victron unit provides the current state of charge, but also statistics about the performance of your battery which are very useful for determining how your systems is working.
  • If you can part with $200 Victron makes a nice unit with Bluetooth, no monitor to wire up.

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