How do I monitor the battery?

[MoTiger]

Hello friends,

I'm in the middle of doing a solar install in my van. I thought I had all the bases covered: 200-watt panel, 100 amp/hr battery, Renogy Wanderer charge controller, circuit breakers, wires, hardware...

Now that I'm actually looking at the charge controller, I realize it has no digital readout, no screen. How the heck do I ever know if my battery is fully charged? Or more importantly, if it is getting too low. How will I ever be sure I'm not draining my battery too low? Is there another device I need to buy to monitor my battery?

Also, the charge controller has a place to plug in an optional temp sensor. Is it worth while for me to order a temp sensor and install it?

Thanks in advance for any input suggestions you might have,

Stymie

 

[jonyjoe303]

You can use a 90 volt 30 amp combometer (cost about 20 dollars on ebay) and place it between the controller and battery. It measures volts/amps going into the battery. I have mine connected to my battery 24/7 almost 8 years, its bright LED you can read from a distance even in daylight. With the combometer you always know the status of your system and also how many amps your panel is producing in realtime.

combometer






Another meter you can use is the tk15 coulombmeter, these cost about 25 dollars for the 50 amp model. You also connect next to the battery and it counts amps going in/out of battery. You program your battery amp hours and max/min battery voltage and it keeps track of the amps you use. With this you know if your getting your battery fully charge. If you use 25 amp hours today, then you know you have to put 25 amp hours back tomorow. This also makes a good wattmeter, it lets you know how many amps/watts your devices are using.

tk15 coulombmeter


I use both on my system.

 

[WalkaboutTed]

We have a Victron battery monitor BMV-700 on the trailer. It was about $140, but it came with a shunt. I put a bluetooth dongle on it, so I can monitor the batteries from my phone or tablet.

On Hubby's van, he has the Victron charge controllers with Bluetooth. I'm just as happy with just that as it holds 30days of data and you can see your daily solar input, your high and low voltages for each 24hour period. Also, I can change settings on the fly, even giving the batteries an extra jolt for iffy circumstances. I'm pretty neurotic, watching things, so even without a formal monitor, I've been able to keep a pretty good idea of where the batteries stand.

On my old van, I had a Blueskies 3000i. I was flying blind with that. To check the resting state on the AGM batteries, I would have to send Hubby out before dawn to check the voltage.

When I install my son's solar system at his offgrid house, I'm putting in Victron charge controllers and monitor. We're looking for land for our tiny house and I'll be doing the same. I've been very happy with their product in both the van and travel trailer.
Ted

 

[RVTravel]

Which model exactly. Read the manual. If the https://www.renogy.com/wanderer-li-30a-pwm-charge-controller/ then it has LED indicators of charge status or you can purchase the bluetooth module to use a phone as the screen?

 

[B and C]

Don't trust any blinking lights telling you the battery is full.  They just tell you the controller went into float mode.  Cheap controllers just have timers built in for each charge state and have no way of knowing when the battery is full or not.

A shunt based battery monitor is the way to go for battery monitoring.  You have to put more back in than you take out of a battery, it isn't a 1 for 1.  My preference and what I installed is the trimetric TM-2030-RV.  A nice added bonus is that it will also tell you the voltage of your starting battery.  Spendy but it is not cheap being your own power company.

 

[WanderingRose]

I use one of these:

https://www.napaonline.com/en/p/BK_...MI6P6ns8DK6wIVnD6tBh3O6A8sEAQYGSABEgIX6fD_BwE

 

[B and C]

Voltage is a better indicator than nothing but at the very bottom of the list. For a true voltage reading, the battery needs to rest for 10 hours. This means no charging or discharging during that period.

 

[WanderingRose]

I’m sure that’s true, but with my limited expertise this has worked pretty well.

I don’t leave it in all the time, but will plug it into the 12volt receptacle most days to just check, as something is drawing off my coach battery all the time when I am traveling.

It helps me keep a watch on what is drawing off my battery the most.

My 100 watt Renogy solar panel also includes a monitor that tells me the charge level as soon as I hook it up to the battery, then as it charges.

 

[highdesertranger]

voltage is a poor indicator of battery SOC(State Of Charge). shunt based amp counters are much more accurate. the best ones count amps both ways, in and out of the battery. I also have a Trimetric you can program it for the amp hours of your battery and it keeps track of amps going in and out and gives you a percentage of full. the other day I saw the highest input for amps that I have seen, 56.8 amps going into the battery. at this moment I have 5amps going out and my batteries are at 67%. the sun has not hit my panels yet. highdesertranger

 

[Weight]

CDI/Balmar has developed a 'smart monitor' that learns your system as you go. It is pricy, $225, but it doesn't require very much programming up dating as your battery changes. https://marinehowto.com/balmar-sg200-self-learning-battery-monitor/

 

[MrNoodly]

I use one of these:

https://www.napaonline.com/en/p/BK_...MI6P6ns8DK6wIVnD6tBh3O6A8sEAQYGSABEgIX6fD_BwE

Yup. I also use one of those, plus a monitor made by MidNite.

https://www.amazon.com/Midnite-Solar-Battery-Capacity-MNBCM/dp/B0041OHFK4

Seven years with the same batteries. Still going strong.

 

[B and C]

I have a midnite kid solar charge controller and looked at that one as it was made by midnite. Didn't get it because it is a glorified voltmeter and is not shunt based.

Edit to add: about the same as the stock RV battery monitor with the red, yellow and green indicator. Voltage based.

 

[technerd88]

victron BMV. Thats how I do it and would recommend it to anyone.. Not expensive compared to batteries and they have bluetooth so you cant forget about it

 

[sneaks]

Load:


Input:


I checked them both vs my SunPro DMM and they are pretty accurate. Granted, you can get ones that will read both but I'm cheap and I have the real estate for two.

 

[MoTiger]

Wow, tons of great information! Thanks to all of you who replied. I appreciate all of the suggestions/advice. I will research all of the items you folks recommended.

Now that I've had more time to ponder this, I want something small/compact, that I can mount on my dash, if possible. I want all of my control centers for everything to be in one place - the driver's seat. I have my charging/power station in the cab. When I want to plug in my laptop, I don't want to have to go to the back of the van, where my battery is. However, I did install the charge controller in back. I wanted it out of the way, in a protected place.


Thanks again to all of you,

Stymie

 

[MoTiger]

Just for educational purposes: Since a battery's voltage gradually declines, as it's capacity is drained, how possible is it to deduce the current capacity of the battery based on current voltage reading? By capacity, I mean "how fully charged" it is.

Or is this completely impossible?

 

[highdesertranger]

"By capacity, I mean "how fully charged" it is."

you need to let it sit with nothing going in or out for several hours. that's the main reason voltage is such a poor indicator. no one lets their battery(s) sit idle for so long. when I had my shop we would let them sit overnight. highdesertranger

 

[MoTiger]

Thanks again. I really appreciate everyone sharing their experience. I'm learning a lot here.

-Stymie