Do I really need a $200 Battery Monitor??

if you seldom boondock, have power hookup, and seldom stay more than overnight, not much need for one IMHO. Now, we often boondock for 10 days or more, use solar for power until we need to turn on the generator. Then a good monitor, like a trimetric is worth it. then I can tell pretty close battery state of charge, when to run the generator when to turn it off.

Gary
Glad you like it
I've been very happy with mine

Went through the thread and didn't see this mentioned. I had an issue with my Magnum inverter. It was just over a couple of years old. I contacted Magnum about where to send it and how much it would cost to fix, and they asked if I had a monitor (I do). Without a monitor, the warranty period is 2 years; with, 5 years. Got the Magnum fixed for the cost or shipping it one way and now I have a spare.

Mr Wizard, I ended up buying and installing the cheap DCM meter you have and it seems to be working out pretty well. During the last several days of putting the finishing touches on my solar install I've been keeping a log of my voltage as shown on the DCM and on my DVM right at the battery. It consistently shows .15 volts less than my DVM shows. I can live with that as it's consistent. The amps are a little off, showing 2.4 amps charging when there is actually no charging going on and virtually no load. I think that's just a matter of calibration which I just haven't had time for. I have to go back and re-read the Chinglish instructions again and figure out what I need to do. In any case I just wanted to thank you, and everone else on this thread who gave me advice on this. You are all so helpful
.

Matt_Colie wrote:
Gary,

...The Vectrin BMV 700 is from Victron and seems to be very complete and well thought out. It is too new for me to have worked with and now that the business is buried, I probably never will.

Be sure to put the time into reading both the install and the operation instruction. None of these are PHD (Push Here, Dummy) devices and it will require some set up time. The results will be rewarding.

Matt

I installed the BMV700 awhile ago and I can highly recommend it. Straight forward installation, a lot of parameters you can play with but it tells me what I need to know. Gives me a clear picture of how much current is being put into or taken out of my battery bank, directly at the batteries. Easy to use remote display too.

MrWizard thanks for scanning and posting the instructions for the ebay monitor. And Harvey, thanks for your thoughts on the monitor MrWizard posted. Looks like I could save some money and get most of the functionality I need, at least for now. I guess sometimes you don't need a Lexus or Cadillac when a nice Mazda sedan will do.

Ken

I have the same monitor as Mr Wizard and Harvey51 and it has served me well in the 5 years of Boon Docking with that monitor. My pair of GC-2's are almost 8 years old and still truck'n.
Well worth it for an inexpensive monitor.

Yes, I think it is essential when boondocking to have a monitor that shows the state of charge in amp-hours and/or per cent of full charge. I tried the voltage chart and ruined my batteries because that chart is not accurate until several hours without any charging. At all other times it is very optimistic because the charging voltage only gradually fades away. I have 12.7 volts on my house batteries after sitting all winter in the MH.

Measuring the electrolyte density is such a pain (I had to take the batteries out of the storage bay) that I didn't do it often enough, particularly in the early morning before turning the thermostat up - so one morning the furnace didn't go on.

The battery monitor ALWAYS displays the state of charge accurately enough. I have the eBay one Boon Docker and Mr Wizard posted a picture of (with instructions). The instructions that come with it are adequate with the wiring diagram in the eBay description. I found the set of three diagrams a little confusing - I'll post a picture of mine. This is a 25 or 30A one, which has the shunt built in. The two terminals marked + are connected together inside the case and need to be connected to any +12 V supply (I ran mine through a switch so I can turn off the monitor). The current flowing from battery negative to/from ground is measured with the shunt connecting the two terminals marked with minus signs. Should you get these two reversed, the "charging" light would come on when discharging.
/
Really it is quite simple once you realize all current to/from the battery must flow through the monitor in order to be measured. On the low amperage model, the terminals are rather small so even 12 gauge wire is tricky. If you need to go with #14 for a couple of inches you won't introduce noticeable inaccuracy. The higher current models have an external shunt making that problem go away. The shunt makes it much easier to mount the monitor in a convenient place with only very light wires connecting it to the shunt in the battery compartment, though I suppose some accuracy would be sacrificed when using it with a low amperage system like mine.



Definitely worth $25, though perhaps not $125 even with the remote.

Here is the eBay page with the 100 amp version
It has quite a bit of info, including some wiring diagrams
It does not have the full instructions set, that I linked in my other post

Imo a great meter for the price

100 amp bidirectional meter,

Gary,

People are always first to mention Bogart Trimetric because they were the first to supply a unit that worked.

Victron was just a little later.

The Vectrin BMV 700 is from Victron and seems to be very complete and well thought out. It is too new for me to have worked with and now that the business is buried, I probably never will.

Be sure to put the time into reading both the install and the operation instruction. None of these are PHD (Push Here, Dummy) devices and it will require some set up time. The results will be rewarding.

Matt