Battery Monitors - Are they worth it?

Submitted: Monday, Dec 12, 2016 at 18:58
ThreadID: 133929 Views:5261 Replies:12 FollowUps:9
This Thread has been Archived
I have just installed 2 new 120ah AGM batteries in to the Quantum, also been tidying up the wiring by installing a recessed switch panel, it amazes me that they don't have a switch panel, switches all over the place, but that's another story!
I guess my question is, are battery monitors worth having, or do they just complicate things? I have always subscribed to the KISS system!
I have looked at Ctek (NASA) BM1 Compact & the Victron BMS 700.

Back Expand Un-Read 0 Moderator

Reply By: Notso - Monday, Dec 12, 2016 at 19:10

Monday, Dec 12, 2016 at 19:10
A simple Volt meter is all I use.
AnswerID: 606641

Follow Up By: RMD - Monday, Dec 12, 2016 at 19:57

Monday, Dec 12, 2016 at 19:57
$15 digital votlmeter from Jaycar is what I also use.
If the volts are down then there is less charge stored in battery which requires a charge. Simple. That is what a solar regulator sees too.
If down it replenishes.
FollowupID: 876350

Reply By: B1B2 - Monday, Dec 12, 2016 at 19:56

Monday, Dec 12, 2016 at 19:56
When you setup the Victron BMS 700 it knows the capacity of your batteries at 240ah. From the shunt which is fitted to the -ive lead back to the batteries, the meter measures how many Ah have been used, how many have been replaced by solar or a charger and gives you a percentage of battery capacity left.
It also gives a complete history of maximum usage, High/Low voltages etc.
I find it useful. It would be even more accurate starting with brand new batteries.


AnswerID: 606645

Reply By: PhilD - Monday, Dec 12, 2016 at 20:08

Monday, Dec 12, 2016 at 20:08
I work on the basis that the more I know about my battery state, the better I can manage it, and be certain nothing has failed. I have a Victron in my Kimberley, and a Finscan touch screen in my Iveco to monitor the Lithium. Not trying to sell a Finscan as they are a complete monitoring system for fuel, water, power, switch circuits on and off, etc, and cost lots of dollars!!
AnswerID: 606646

Reply By: Gronk - Monday, Dec 12, 2016 at 20:21

Monday, Dec 12, 2016 at 20:21
I use the KISS system also..a led voltmeter ( $10 ).

I know my batteries are getting a little tired after 4 1/2 yrs because they get down to approx 12V (under load ) a lot sooner than they used to. I don't need to know exactly how many a/h's I have, as long as the beers stay cold until the magic 12v recharge level.
AnswerID: 606647

Reply By: Member - Blue M - Monday, Dec 12, 2016 at 21:30

Monday, Dec 12, 2016 at 21:30
This is my experience,

On my first Camper Trailer I had nothing, not even a volt meter, when the fridges stopped I knew the batteries were flat. 2 x 100ah batteries no solar.

Next I had a Jayco with one little volt meter hooked up and I used to look at it every now and again. 2 x 100ah batteries and 2 x 80w solar panels.

I now have a U beaut caravan with all the bling, and all I seem to do all day is watch gauges and worry. 5 x 120ah batteries and 5 x 140w solar panels.

I don't drink, so keepin the beer cold is not a priority.

I think KISS is the best way.


AnswerID: 606649

Follow Up By: Shaker - Monday, Dec 12, 2016 at 21:34

Monday, Dec 12, 2016 at 21:34
That's what I was worrying about, becoming obsessive about batteries!

FollowupID: 876355

Follow Up By: tazbaz - Monday, Dec 12, 2016 at 23:03

Monday, Dec 12, 2016 at 23:03
Start with a few beers, then some white wine, then some red wine, then a port wine. By then you won't worry!
FollowupID: 876362

Follow Up By: Nomadic Navara - Tuesday, Dec 13, 2016 at 15:15

Tuesday, Dec 13, 2016 at 15:15
Five batteries. That's nearly 200 kg. Add plenty of water and your 400 kg load allowance has nearly gone. Have you had an ATM upgrade done to your van to give yourself some decent load allowance in the van?
Retired radio and electronics technician

Lifetime Member
My Profile  Send Message

FollowupID: 876378

Follow Up By: Member - Blue M - Wednesday, Dec 14, 2016 at 02:07

Wednesday, Dec 14, 2016 at 02:07
I have 3 batteries and 3 solar panels in/on the van and others in/on the canopy of the ute.

I did get a bit extra payload when I ordered my van. The ute has been given a GVM upgrade to 3760kg as well. I come just with in the GCVM when fully loaded.

I wanted as much as I could get, as I had been warned there are some people around who dislike the soothing hum of a generator purring away in Eco mode whilst charging a battery.

FollowupID: 876398

Reply By: Malcom M - Tuesday, Dec 13, 2016 at 08:08

Tuesday, Dec 13, 2016 at 08:08
Depends a bit on why you want to monitor things.
KISS is ok if you simply want to see the current voltage level but sometimes you might need more, consider this-
You are away camping and its been cloudy and the fridge is cutting out due to low batteries. Question is, are your batteries old and lacking storage, just not fully charging or maybe stuffed.
Have a monitor that can tell you amps in and out can be handy in figuring that out.

If all you want to see is the battery voltage then maybe its a better idea to fit a low voltage cutout.
AnswerID: 606656

Follow Up By: RMD - Tuesday, Dec 13, 2016 at 12:01

Tuesday, Dec 13, 2016 at 12:01
If the system is working correctly but the fridge stops and make you think the batteries are faulty because of age. MAke sure you do something which will definitely charge the batteries to their max stage of charge possible.
If fridge still stops, then replace batteries. Not much else it can be is system is healthy.

Exactly the above was a mates caravan, I suggested batteries. He purchased a DC/DC unit, still no joy and fridge still stopped. Later in trip he replaced the two 120ah crappy calcium batteries for 2 AGM batteries. Funny that it remedied the problem. No need to know the in and out cos you still won't know what is the problem.
FollowupID: 876375

Follow Up By: Malcom M - Tuesday, Dec 13, 2016 at 14:20

Tuesday, Dec 13, 2016 at 14:20
Very limited thinking that.
If you are camping during a very hot spell and opening/closing the fridge quite often then you will increase battery drain considerably. Doesn't mean the batteries are stuffed, simply not enough charge going back into the batteries to keep up with the power drain.
You would replace the batteries whereas I might add an additional unit before the next trip. Knowing the current in/out would show you this.
FollowupID: 876376

Follow Up By: RMD - Tuesday, Dec 13, 2016 at 20:23

Tuesday, Dec 13, 2016 at 20:23
Fully charged and then overnight the batteries don't last past 1am. No door opening at all. 20c temp max. All points to batteries. Anyone will allow for usage, I hope.

It WAS the batteries. A sound diagnosis after sensible observation.
No limited thinking at all. New batteries were suggested BEFORE the trip. The way it worked ensured the outcome.
FollowupID: 876392

Reply By: Sand Man (SA) - Tuesday, Dec 13, 2016 at 09:11

Tuesday, Dec 13, 2016 at 09:11
Hi Shaker,

Are Battery Monitors worth it?
It depends on your perception I guess.
You can buy cheap ones or expensive ones.

Are they necessary? No!
Are they piece of mind? Most definitely!

I have a camper van with a pair of 100Ah batteries installed to run my compressor upright fridge in the camper.
At about $750 the pair, I need to rely on those batteries performing well at all times as I do a fair bit of bush camping.
These batteries are maintained by a Ctek D250S dc-dc charger and supported by solar panels as necessary. To monitor the battery bank, I added a Nasa BM-1 monitor which displays volts and amp hours, giving me battery bank status at a glance, at any time I look at it. I don’t have to remember to apply a volt meter from time to time. The monitor cost about $150 a couple of years ago.
“Piece of mind”.

Just recently, I added another Ctek D250S charger to my vehicle auxiliary battery, supporting a portable fridge in the back of the vehicle. We are planning a long trip to the Pilbara and Kimberley regions next year and I need to ensure good battery health.
For about $30 extra I purchased the Ctek in a “kit” form which included a tote bag (big deal) and a nifty little device called a “Battery Sense”.
This little device normally retails for about $69 so is not a huge outlay. It is simply connected across the battery terminals and links to a free App running on my iPhone. Any time I choose, I can get the status of the battery, displayed as percentage. Not only can I determine battery health, but judge if the battery is maintaining its charge whilst driving, or remaining capacity at camp, prompting me to connect my portable solar panel as necessary.
“Again, piece of mind”.

The Ctek Battery Sense is a “stand alone” device and appears to be a low price solution for battery monitoring.

The "hard wired" Ctek Digital Battery Monitor appears to be identical in appearance to the Nasa BM-1 unit.

I'm diagonally parked in a parallel Universe!

My Profile  My Blog  My Position  Send Message

AnswerID: 606657

Reply By: swampy - Tuesday, Dec 13, 2016 at 09:49

Tuesday, Dec 13, 2016 at 09:49
First u need enough solar and battery capacity . Having enough of both builds a strong system . EG Able to with stand cloudy days by quick recovery of battery state in a very small window of sunlight.
A monitor does not charge batteries .
Remember a
200 watt panel harvests 50ah
So therefore to use 50% of a 100-120ah battery you need 200watts
Prioritize ,until u have 200w per 100ahr batt a volt meter is enough .
Remember in southern states where peak sun hours are even smaller this statement could not be more accurate ..
AnswerID: 606660

Reply By: Sigmund - Tuesday, Dec 13, 2016 at 14:43

Tuesday, Dec 13, 2016 at 14:43
Voltmeter doesn't give you an accurate idea of your batteries' state unless you prepare them for a reading. Better to work out an energy budget. You can estimate draw under varying conditions (your spending) and then fit an inline monitor (using Andersons, c $40) to record amp hours going in, from the wagon or solar panels (earnings). After a while you'll learn your system and won't need to continually check.
AnswerID: 606664

Follow Up By: Zippo - Tuesday, Dec 13, 2016 at 17:37

Tuesday, Dec 13, 2016 at 17:37
And those Ctek sense devices are no more than a glorified voltmeter with sampling.

On top of that, nowhere in the Ctek literature do they mention the standing current draw to feed this little voltmeter-with-bluetooth-transmitter combo. The current draw may well be totally insignificant, but that is left as an assumption for the user.
FollowupID: 876387

Reply By: Nomadic Navara - Tuesday, Dec 13, 2016 at 15:41

Tuesday, Dec 13, 2016 at 15:41
If you are going to use an SOC monitor you need to recalibrate it periodically. It needs to know the actual capacity of the battery to give an accurate reading. Batteries loose their capacity over their life. They don't retain their rated capacity until they suddenly die. A 10 year old battery could be down to ½ capacity if it has been well used.

If you use a volt meter as your battery monitor you need to rest it for a couple of hours before you take your reading for an accurate calculation of capacity. As your battery gets older it could have a capacity of half its new capacity. When you have used ½ of that reduced capacity the rested volt meter will read the appropriate a battery at ½ capacity. However if you are using a SOC meter and not recalibrated it at all it will convince you that you have ¾ capacity. When your battery is nearly flat a volt meter will tell you it is nearly flat. However a non recalibrated SOC meter will tell you that your battery is around ½ capacity. If you use the battery a bit longer you will be wondering why the lights went out and the TV goes blank.
Retired radio and electronics technician

Lifetime Member
My Profile  Send Message

AnswerID: 606665

Reply By: Grizzle - Tuesday, Dec 13, 2016 at 17:06

Tuesday, Dec 13, 2016 at 17:06
I have monitors in my car but my son and I hired a Britz Troopy in Darwin a couple of months ago. It had an Engel 40 litre in it and no monitors. We didn't even think about battery voltage or if the fridge was working!!!

My son actually mentioned it to me after we got back to Melbourne.

Funny, if its there you will look at it, if it isn't you don't think about it!!!

Lifetime Member
My Profile  Send Message

AnswerID: 606669

Reply By: The Bantam - Wednesday, Dec 14, 2016 at 09:20

Wednesday, Dec 14, 2016 at 09:20
knowing the terminal voltage of your batteries is a good idea.

Knowing how much current is comming in or out of your batteries at any given time is helpfull.

Without both of those ya pretty much blind to what is going on in your electrix system

As for the analiser/datalogger type battery monitors.
If you are happy to spend your money and realise they simply can not be accurate and can not be relied upon ..... they can be helpfull.

It must be understood that the concept of "accuracy" and " battery capacity" realy don't go together.

We need to read terminal voltage very accurately even to have a vague idea of what is going on in a battery.

A battery ... pretty much any technology, but espcially the lead acid family is not a bucket or tank of fixed capacity.

Battery capacity varies quite a bit with a number of variables.

Remember, for the best service life from your batteries, you need to be cycling them less than 50% capacity depth.

Accuracy in pretty much unhelpfull ...... the shallower you cycle the battery ..pretty much the longer it will last.

A data logging battery monitor can be helpfull ..... but never accurate.

AnswerID: 606679

Sponsored Links