Cheap Little Battery MONITOR - But How Good Is it ?

RAW

Full Member
I bought this a while back on Banggood, as the Alpha AGM Battery is not in a Van at present I thought I would connect it up. I think it could be relatively accurate but to test fully I would have to charge the AGM to full then have a 1 amp draw or more to watch the battery capacity lessen over time.
Potentially though it could be an accurate device.
As far as the Temperature goes it is the ambient temperature of the device and not the battery temperature (could be a misnomer).
Still at a little over a fiver it is probably good value I think
www.banggood.com/JS-C33-10-100V-Universal-LCD-Car-Acid-Lead-Lithium-Battery-Capacity-Indicator-Digital-Voltmeter-Voltage-Tester-Monitor-Meter-p-1416277.html

I have run it alongside a Victron Smart battery Sense for now

Screenshot_20200302-141234.jpg20200302_141145.jpg20200302_141214.jpg

Thoughts ?
 

Nabsim

Full Member
How does it know when the battery is 100% @RAW, is it similar to the Victron monitor that you have to set parameters? If not what does it do when charging, does it show 100% then drop to real state when charge source off?

looking at the size it could fill the cut out a previous owner made in dash to fit a digital clock that I have disconnected, I would connect to starter battery though 👍
 
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RAW

Full Member
How does it know when the battery is 100% @RAW, is it similar to the Victron monitor that you have to set parameters? If not what does it do when charging, does it show 100% then drop to real state when charge source off?
Well all good questions and I was thinking similar so was just getting some bits and bobs off the kitchen floor, which is where all the Van gear is, to do some testing. Sylvia is sold now thankfully, and I STUPIDLY connected the Edecoa Inverter the wrong freaking way round !!!

SO to answer your questions
How does it know when the battery is 100% @RAW - Don't know, it says it can monitor 12/24/48 V systems so somewhere it must detect voltage and make a calculation ?
have to set parameters - NO, no way to set anything

Yes I think it is a good idea to connect to starter battery.
 

SquirrellCook

Full Member
I purchased some Coulomb counters before I change my mind and took the Victron route. I went for the inductive pickup style, but after experimenting on the bench for a few months I wasn't convinced as to their accuracy. One prematurely died also. I get stressed when things don't work as I expect.
 

RAW

Full Member
I purchased some Coulomb counters before I change my mind and took the Victron route. I went for the inductive pickup style, but after experimenting on the bench for a few months I wasn't convinced as to their accuracy. One prematurely died also. I get stressed when things don't work as I expect.
So some Analogue type Monitor I guess, I would assume these are similar and also like the ones you get with inverters that show the Battery State of Charge. Just blew my inverter BTW 🤬🤬🤬🤬 see here
 

wildebus

Full Member
How does it know when the battery is 100% @RAW, is it similar to the Victron monitor that you have to set parameters? If not what does it do when charging, does it show 100% then drop to real state when charge source off?

looking at the size it could fill the cut out a previous owner made in dash to fit a digital clock that I have disconnected, I would connect to starter battery though 👍
To answer the first question, it is simply a function of "SOC" vs Voltage in terms of what it displays. TBH, the battery meter display is pointless. If you wanted to check this, connect the battery to a charger and see the fuel guage instantly hit 100% and stick on a big load and see in instantly drop.

I guess that could be useful for someone who didn't want to pay for a proper monitor and didn't want to have to work out what a voltage figure likely meant.
Word of note: those pre-set voltage-battery level conversions don't apply to Lithium Batteries.
 

trevskoda

Full Member
I have to cheepos ,one for starter and other for less batts,i dont and am not a battery watcher,birds yes. o_O
van f.jpg
 
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RAW

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If you wanted to check this, connect the battery to a charger and see the fuel guage instantly hit 100% and stick on a big load and see in instantly drop.
I plugged a Charger in and got this, took about 3 mins to get to 100% - in retrospect I should have simply disconnected the charger when the 100% mark was reached and seen then what the Monitor dropped back to
Anyway as the AGM battery needs a bit of charge I have left it charging. This is not a hugely inspiring video, just for reference really and the timeline was paused to shorten it
 

Nabsim

Full Member
To answer the first question, it is simply a function of "SOC" vs Voltage in terms of what it displays. TBH, the battery meter display is pointless. If you wanted to check this, connect the battery to a charger and see the fuel guage instantly hit 100% and stick on a big load and see in instantly drop.

I guess that could be useful for someone who didn't want to pay for a proper monitor and didn't want to have to work out what a voltage figure likely meant.
Word of note: those pre-set voltage-battery level conversions don't apply to Lithium Batteries.
That’s how i thought it would be doing it David 👍

I don’t need anything really to monitor the starter battery (Bosch PowerFrame) it’s just I disconnected the horrid little digital clock in the dash as it annoyed me and I thought this may be similar size (isn’t now I have measured). I noticed you could turn the display off on these so wouldn’t annoy me :)
 

RAW

Full Member
Now the Battery Should be fully charged according to the cheap and cheerful Battery Charger, left on overnight.
20200304_080444.jpg
I turn on the cheap and cheerful battery monitor and see a reading of 97% and 13.1V, I am pretty sure the full charge capacity of the AGM is 13.4V in output voltage. 13.1 V is confirmed by the Victron Battery Monitor
20200304_080454.jpg
NOW - Was going to ask what was going on and then re-read the Spec of the Charger and saw this:
Charging Current: 0.9A(Small),3.8A(Normal)
Battery Types: Wet, Gel, MF, CA, EFB, AGM & LIB
Battery Capacities: 2-120Ah (6V), 2-120Ah (12V), Maintains All Sizes of Batteries

So that would be why the charger won't fully charge the battery. However, this also indicates to me (correct me if I am wrong @wildebus) that the small battery monitor is quite accurate as the charge state now would be 97% or thereabouts I would think.
 

wildebus

Full Member
well, I am surprised it is not reading 100% with a battery voltage of >13V.
If it only has two connections - +ve & -ve - there is no way it can read the current so it must be basing the battery level on voltage alone, but not on 100% at >13V makes no sense.

It's magic, I tell thee!
 

SquirrellCook

Full Member
I purchased something like that a few years back for a power supply project. When it turned up and I finally found it in the packaging I couldn't see it's legs!!
 

Nabsim

Full Member
You really need the manufacturers data sheet for you particular battery if you are using voltage for battery condition. I suspect that’s one reason I did my PowerFrame battery’s in so quickly. 12.2v on those is a lot less than 50% left. Most folks are low users and on EHU so it doesn’t matter though lol
 
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