Battery monitor

There is a battery monitor a victron bmv 700 I believe at $200.00 that uses a shunt but there is also an aili battery monitor that uses a shunt same type of meter face as the victron but its only $32.50 (amazon). Has anyone used these monitors and what is the diffrence between them.

A link to the $32 monitor at Amazon would really help.  Leaving out the link is just asking folks to try spend their time trying to guess which monitor you are asking about.

We have a Victron BMV 712, with the built in Bluetooth.  https://www.amazon.com/Victron-Energy-MONITOR-VTBMV-S-BMV-712-Battery/dp/B075RTSTKS/ref=sr_1_2?keywords=victron+bmv&qid=1552652181&s=gateway&sr=8-2

We do a lot of boondocking, and this thing has been SO useful!  It was a snap to install and set up (you need to know your battery bank's total amp hours).  I LOVE the phone app with Bluetooth connection.  A quick glance shows me precisely how much battery life I have left, how much power we've used and are using currently, and how long (approximately) I have left before I need to charge.  Also really helps to know exactly when I can turn off the genny and know we're fully charged.  As a bonus, it shows current amp draw pretty exactly, so it's also helpful to get a handle on what each individual device uses, as well as a baseline of power consumption when everything is turned off.  There are some nice history functions, too, so you can see use over time. 

I wouldn't hesitate to recommend it.  Yes, it's a wee bit spendy, but I've found it to be well worth the investment to get much more piece of mind.

https://www.amazon.com/AiLi-Battery-Monitor-Voltmeter-Motorhome/dp/B07CTKYFTG/ref=sr_1_3?crid=2610RC4E213D0&keywords=aili+battery+monitor&qid=1552672207&s=gateway&sprefix=aili+%2Caps%2C311&sr=8-3

This is the link to the cheap battery monitor.

I have read on other message board that those cheap style battery monitors don't do well at reading light parasitic loads so quickly go out of calibration due to not reading these constant low current losses.

FYI, the Victron units "sync" each time the battery is fully charged.  It's been very accurate as far as I can tell.

I bought this one on ebay. It doesn't have all the bells and whistle a Victron does but I don't need to find my phone to see what my battery is doing. Easy to read and been accurate so far. If it goes bad I can still buy 9 more for the price of a Victron. If you like techie stuff then get a Victron. This ain't it but it works for me.

skeeter

skeeter_ca said:

I bought this one on ebay. It doesn't have all the bells and whistle a Victron does but I don't need to find my phone to see what my battery is doing. Easy to read and been accurate so far. If it goes bad I can still buy 9 more for the price of a Victron. If you like techie stuff then get a Victron. This ain't it but it works for me.

skeeter

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A link to what you bought would be nice.

skeeter_ca said:

I bought this one on ebay. It doesn't have all the bells and whistle a Victron does but I don't need to find my phone to see what my battery is doing. Easy to read and been accurate so far. If it goes bad I can still buy 9 more for the price of a Victron. If you like techie stuff then get a Victron. This ain't it but it works for me.

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Does this unit have a shunt or does it rely on battery voltage for calculations?

For $200, I would have expected the Victron to have a hall effect current sensor instead of a shunt which can fail...you don?t always get what you pay for.  It has other nice features though.

ClassyC said:

For $200, I would have expected the Victron to have a hall effect current sensor instead of a shunt which can fail...you don?t always get what you pay for.  It has other nice features though.

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The similarly priced Trimetric also uses a shunt. Are there competing products in this price range that use hall effect sensors?

In the course of my earlier life as an industrial electrician and controls tech, I have seen hall effect sensors fail too. I've also seen them fail when used in vehicle ignition systems too.

I really just started looking at solar equipment, so I don?t have a broad view on exactly who offers what yet.  The issue I have with a shunt failing is that you are out of business while a sensor failure would just kill your ability to monitor. Coming from an industrial background as well it just surprised me that a apparently high end product didn?t take advantage of indirect measurement.  Only an observation, not a dislike of the Victron product.

ClassyC said:

I really just started looking at solar equipment, so I don?t have a broad view on exactly who offers what yet.  The issue I have with a shunt failing is that you are out of business while a sensor failure would just kill your ability to monitor. Coming from an industrial background as well it just surprised me that a apparently high end product didn?t take advantage of indirect measurement.  Only an observation, not a dislike of the Victron product.

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How would a shunt "fail"?  A shunt is not any more likely to fail than a 2 inch section of heavy wire will fail.  (wire about the size of 4/0 cable)  A shunt is nothing more than a precision length of heavy copper or brass installed on the negative side of the battery pack.  Attached to each side of this piece of copper or brass are two wires which then go to the remote monitor.  The monitor then measures the very small voltage difference between the two ends of the heavy copper brass.  The voltage difference is probably in the millivolt or microvolt range.  If the wires to the monitor or the monitor would fail that would not affect the operation of the 12V system in the RV.

A properly sized shunt is rated for a 100 or more amps than the possible current draw of the circuit.  My shunt for my battery pack is rated at 500amps.  The battery pack is 400AH (Amp Hours).  The circuit breaker on the positive side of the battery pack is rated at 180amps.  So the max amount of current possible is about 180 amps or somewhat more for the short time it would take for the CB to trip and open the circuit.  Nowhere near the amount of current required to damage the shunt.

More details at Wikipedia:  https://en.wikipedia.org/wiki/Shunt_(electrical)  You will need to scroll down about half way to the section titled "Use in current measuring" for the details for the shunt used for 12V battery monitors.

Of the two you mentioned I have experience with only Victron which has been very good, i highly recommend it.  Considering the price differential between the Victron, other highly regarded battery monitors I would say the Amazon one is likely not going to be as accurate, may not be as easy to operate and perhaps not as reliable.  Considering the cost of batteries these days, I would not consider the Amazon one, rather spend on proven quality.  My prior experience has been with the Trimetric, also very good and worth considering.  With the Victron and it's Bluetooth App, I have installed the monitor in the basement just inside the door out of sight, but available if I need it, and now have the luxury of checking the batteries from the comfort of a chair or bed upon waking up.  Another benefit of the Bluetooth app is if I am curious what the amp draw of various components, I can walk around the coach and turn on and off each component, without having to go back to the monitor.  The Victron while a relatively recent player in the RV industry, has been a stalwart in the boating industry and have proven themselves in tough conditions.