Measuring Battery Charge

[awol]

Is there a way to tell how much charge is left in my battery with one of those cheap yellow multimeters?
How have others been measuring how much watt hours or amps still left in battery before a recharge is required?
I have not ridden my new future commute yet and won't be for a few weeks but would like to go for a small ride and work out how much battery I've used and how much is left so I've an idea how many full trips I will get per charge.

 

[Alan Quay]

Measuring voltage will give you an approximation. You will need to know what the type of battery, and wait for a bit between using and measuring to let it all stabilise.


Sent from my HTC One using Tapatalk

 

[Deleted member 4366]

You can do it with one of these:

New Digital 60V/100A Battery Balance LCD Voltage Power Analyzer Watt Meter | eBay

or these:

60V/100A Digital Battery Balance Voltage Power Analyzer RC Watt Meter Checker | eBay

If you decide to get one, let me know, and I'll tell you a good way to wire it up.

 

[Richard_M]

That's absurdly cheap, so I've bought one straight away. I couldn't buy the LCD for that price.
I'll check its accuracy thoroughly when it arrives.

 

[Sheffmax]

You can do it with one of these:

New Digital 60V/100A Battery Balance LCD Voltage Power Analyzer Watt Meter | eBay

or these:

60V/100A Digital Battery Balance Voltage Power Analyzer RC Watt Meter Checker | eBay

If you decide to get one, let me know, and I'll tell you a good way to wire it up.

Can you add the instructions to this thread, please? If it's as simple as you say I may get one myself.

 

[astroeyes]

will they work for 10 cell batteries though?

 

[Deleted member 4366]

Use 14g silicone wire or equivalent:
14g silicone wire | eBay

The meter only measures the current on the negative (black) side but it needs a positive connection on the red wire to power it, so the black wire carries the whole battery current, and the red one a few miliamps. You can make it a lot neater and avoid power losses by eliminating the thick red wire:

Start from the battery to controller connection. Run the black wire from the black battery side to the meter and back to the controller black.

Connect the red wire from the controller directly to the battery so that it doesn't go through the meter.

Connect a thin wire from the red battery controller to the red meter wire on the input side.

Insulate the meter red wire on the output side.

To make a mount for it, you can cut the edges off one of these and use Pritt pads to hold it on.
Bike Bicycle Mount Phone Stand Holder For Samsung Galaxy S4 S IV I9500 New | eBay

I prefer to make it a it tidier by making a mount out of a bit of 1 mm aluminium sheet. Cut a hole in it the size or your stem cap, shape the outside, and use Pritt pads or similar to hold the meter on. Something like this:

 

[awol]

Thanks for the great reply and the wiring instructions too, I may be asking how to decipher the info on the displays in a few weeks!!

 

[awol]

Well, I went for the blue Watt meter and it's just arrived. Is there any calibrating type checks to do or simply wire up as per d8veh's instructions above and good to go?

 

[awol]

Forgive my lack of electronics knowledge but I have got a blue watt meter which is labelled source one side and load the other, does the black 14g wire from the battery goes to the source or load side of the watt meter. (I don't know which is input/output when described as source/load)

 

[Sacko]

Battery is the source.

Controller is the load.

 

[Deleted member 4366]

So thick black and thin red from the battery to the source side. Thick black from the load side to the controller. Thick red from the battery direct to the controller.

 

[NZgeek]

I fitted one of the cheapy Watt meters that d8veh recommended in a thread somewhere - it works great! I haven't verfied it's readings, but it's close enough for what I need, I'm sure.

I've mounted it on the handlebars temporarily, so I have some 4mm2 wire running from the battery connector up to the front and back, and made a pair of connectors that piggybacks with the bike/battery connector - I can remove it whenever I need, and add it back in easily.

(Thanks again, d8veh!!!)

 

[awol]

Thanks for the info, that's a job for the weekend planned.

 

[awol]

Thanks all, now fitted and working. The bottom left figures cycle through some info. Does
ah=amp hours been used?
wh=watt hours been used?
but what do - wp , ap , vm - stand for ?

 

[Deleted member 4366]

Vm is minimum voltage
AP is actual amps?
WP is actual watts?
aH is accumulated amp-hours
WH is accumulated watt-hours

 

[Alan Quay]

Vm is minimum voltage
AP is actual amps?
WP is actual watts?
aH is accumulated amp-hours
WH is accumulated watt-hours

AP = Amps Peak
WP = Watts Peak

 

[Deleted member 4366]

AP = Amps Peak
WP = Watts Peak

I knew that. I was just testing to see if you were paying attention.

 

[jhruk]

Those who ordered the Blue Watt Meter from ebay may find the comprehensive instructions for the similar Watt's Up or Turnigy meters helpful. They can be found here:

http://www.rc-electronics-usa.com/docs/wu100v2_user_manual.pdf
Turnigy Meter Manual

It might also be worth checking the calibration. The one I received was obviously out as it read .22A with no load attached, so I guess it had missed the calibration step at manufacture. There are two trim pots inside so it's not a big problem.

 

[Aushiker]

Connect a thin wire from the red battery controller to the red meter wire on the input side.

What weight is suggested for this thin wire? Would say 18AWG or 24AWG do the trick?

Thanks
Andrew