EEVblog #779 - How To Measure Product Battery Cutoff Voltage

[AmmoJammo]

What's with that graph ?

Looks like on normal battery the min current slowly ramps up and drops off around the 1:30 mark then dies at 2:00.  Is that normal behaviour for a gps ?

I'd expect the current to increase as the voltage decreased, to keep the power the same.

I'm wondering if the GPS then went into some "low battery" mode, which resulted in the lower current draw.

[romelec]

It is a Garmin Dakota that should have a 20h lifetime.
With the screen always on 10 hours seems fine.

About the graph difference:
The device needs a constant power, so as the voltage drops the current increase. Maybe then it enters in a lower power mode to work as long as possible.
The current is constant with the batteriser on because the voltage is constant.

One thing with their test: they measure the current, there is a shunt resistor so the voltage at the GPS drops way faster below the cutoff voltage...
With their thing the voltage stays at 1.5v so the drop of the shunt is not a problem.

[Fungus]

What's with that graph ?

Looks like on normal battery the min current slowly ramps up and drops off around the 1:30 mark then dies at 2:00.  Is that normal behaviour for a gps ?

It's normal for one that has a built-in DC booster, ie. the batteriser does nothing except interfere with it.

If the battery dies after two hours they much have selected the wrong battery type in the menu (and I suspect it wasn't accidental - they deleted a comment that asked about that).

[AmmoJammo]

On the GPS test, the current increases from 125ma, to 150ma... (before it goes into the weird mode)

Assuming its trying to do the same power, that means if it drew 125ma at 3volts. To draw 150ma, the batteries are down to 2.5volts, or 1.25volts per cell....

That appears to have occurred over a period of 90 minutes.

I have no idea where I'm going with this 

[AmmoJammo]

On the GPS test, the current increases from 125ma, to 150ma... (before it goes into the weird mode)

Assuming its trying to do the same power, that means if it drew 125ma at 3volts. To draw 150ma, the batteries are down to 2.5volts, or 1.25volts per cell....

That appears to have occurred over a period of 90 minutes.

I have no idea where I'm going with this 

To quote myself, it would seem, that for a Duracell CopperTop, to drop to 1.25volts, in 90minutes, it would require you to have a 350ma load or so.... not the 150ma they had...

In other words, I don't think the two tests were done with the same brand cells.... 

EDIT!
They've shown the current draw of the gps as being around 150ma.... based on the Duracell datasheet, you can extrapolate that, based on the 1.25volt "low battery" mode, that you'll get somewhere around 8 hours run time....

As to what they did? 

[Fungus]

They've shown the current draw of the gps as being around 150ma.... based on the Duracell datasheet, you can extrapolate that, based on the 1.25volt "low battery" mode, that you'll get somewhere around 8 hours run time....

As to what they did? 

We can only assume, but... they most likely selected an incorrect battery type and the GPS shut itself down even though the battery was still OK.

[AmmoJammo]

They've shown the current draw of the gps as being around 150ma.... based on the Duracell datasheet, you can extrapolate that, based on the 1.25volt "low battery" mode, that you'll get somewhere around 8 hours run time....

As to what they did? 

We can only assume, but... they most likely selected an incorrect battery type and the GPS shut itself down even though the battery was still OK.

Based on the current draw increase, assuming a starting voltage of 1.5volts, it shut down at around 1.25volts.

[EEVblog]

We can only assume, but... they most likely selected an incorrect battery type and the GPS shut itself down even though the battery was still OK.

I asked on the Youtube page and they actually replied 
They claim they used the Alkaline battery setting.
You'd think they would have said that in the video or description though.

[EEVblog]

If the battery dies after two hours they much have selected the wrong battery type in the menu (and I suspect it wasn't accidental - they deleted a comment that asked about that).

They replied to my comment, they claim to use the Alkaline setting.

[george graves]

Hmmm.  Dave, do you have any contacts with guys in the battery industry?  It would be awesome if you could get someone to do a phone interview. That would be some real interesting stuff.

Look who's on top when you search YouTube for 'batteriser'... I bet they're really scared now.

Unless you used a proxy, and a new IP, and cleared all your history and cashe, google will just give you what it thinks you want. I assumed everyone knew that by now, no?  Your google search isn't my google search, each one is custom based on your gmail/google/youtube search history.

[AmmoJammo]

... based on the 1.25volt "low battery" mode ...

And why do you assume that low battery kicks in at 1.25V per cell? If they accidentally left the type setting at lithium, thresholds levels probably be ridiculous considering alkaline discharge curves.

because 125ma at 3volts is 375milliwatt... and 375milliwatt at 150ma, is 2.5volts and 150ma is where the gps appeared to go into some power saver type mode.

and even if the cutoff could/should be lower than 2.5volts/1.25volts per cell, it still should have about 8 hours run time off decent AA cells, with its ~150ma current draw!

[HKJ]

They replied to my comment, they claim to use the Alkaline setting.

What about voltage drop in the wires and the ammeter?

[TheAmmoniacal]

The GPS seems to be a Garmin Dakota 20, the owner's manual says:

"Optimizing Battery Life Use premium batteries for optimal performance and maximum battery life. The best performance is provided by lithium batteries, precharged (ready-to-use) NiMH batteries, and NiMH rechargeable batteries less than one year old with a capacity greater than 2500mAh.Consider the following suggestions to maximize battery life:
•Do not adjust the backlight more than is necessary (page 3). Using a backlight level above 50% of maximum level for a prolonged period of time will significantly decrease battery life.
•Select a shorter backlight timeout (page 22).
•Turn tones off if not needed
•Turn the electronic compass off if not needed (page 28)"

[AmmoJammo]

and even if the cutoff could/should be lower than 2.5volts/1.25volts per cell, it still should have about 8 hours run time off decent AA cells, with its ~150ma current draw!

I would suspect that it could be much higher than 1.25V, hence the early shutdown happened.

It didn't actually shut down at that point, it changed modes, and started drawing less current for another half an hour.... wait! half my previous numbers were wrong, as I read the first division on the graph as 1 hours, not 2... so it ran for about 90 minutes before changing modes...

[TheAmmoniacal]

The current draw is not constant, but it seems to be an average of 175 mA, but we can conservative and say 200 mA. How on earth can it last for no more than 2 hours?

[wraper]

Hmmm.  Dave, do you have any contacts with guys in the battery industry?  It would be awesome if you could get someone to do a phone interview. That would be some real interesting stuff.

Look who's on top when you search YouTube for 'batteriser'... I bet they're really scared now.

Unless you used a proxy, and a new IP, and cleared all your history and cashe, google will just give you what it thinks you want. I assumed everyone knew that by now, no?  Your google search isn't my google search, each one is custom based on your gmail/google/youtube search history.

800% baloney indeed pop up on top of the search even if you go stealth. Changing IP is not necessary BTW.

[Fungus]

If the battery dies after two hours they much have selected the wrong battery type in the menu (and I suspect it wasn't accidental - they deleted a comment that asked about that).

They replied to my comment, they claim to use the Alkaline setting.

They also claim that most users wanted to see results for high end cameras and GPS devices.

Weirdly enough: Those are the exact same devices that EEVBLOG forum members predicted the batteriser might be worth using with.

(and they're also not the devices the super-smart PHDs were using last week to demonstrate the benefits of batteriser).

Hmmm.

[AmmoJammo]

The current draw is not constant, but it seems to be an average of 175 mA, but we can conservative and say 200 mA. How on earth can it last for no more than 2 hours?

by having it shut off at 1.39volts, like most devices do? 

[TheAmmoniacal]

The Garmin Dakota 20 supports three battery types, Alkaline, Lithium and Rechargeable NiMH. The type of battery you use has to be specified in the menu (Setup -> System -> Battery Type). If they are complete scam artists, as I suspect, they may as well have selected Lithium battery in the menu while using alkaline.

I've seen devices on lithium batteries with cutoff voltages as low as 2.75 V/cell, but frequently in the 3 V/cell range I'd think? The fresh batteries were 3.240 V, so is it likely?

[firewalker]

How much does the GPS unit cost? Maybe Dave should buy one... 

Alexander.

[Fungus]

How much does the GPS unit cost? Maybe Dave should buy one... 

Nope.

The only thought in their heads right now is surviving until the indiegogo thing is finished.

Anything that takes a week to arrive or allows them to stall for a few days is what they want. The only way ahead is to get enough complaints through to IndieGoGo that they pull the campaign.

I've already posted a list of the many ways they're breaking the IGG terms of service here:

https://www.eevblog.com/forum/blog/eevblog-779-how-to-measure-product-battery-cutoff-voltage/msg729686/#msg729686

[firewalker]

I am sure there will a local Garmin dealer in Syndey with this gps unit. 

Alexander.

[AmmoJammo]

It would appear their 800% claim came from this video.



13% battery, being boosted to 1.5volts, so the indicator shows 100%...

I guess seeing as batteries store 1.5volts of energy, it all makes sense!

[edy]

Don't waste your breath on IndieGogo... I have sent complaints for even more scammy campaigns and nothing is ever done.

The marketing bull$#!t aside, the product does appear to exist and boost a voltage. They have way more dubious complete garbage products (see the "crowd-funding" sub forum here on EEVBlog) which nobody has successfully had IGG cancel due to complaints.

So save your breath. IGG couldn't care less as long as they get their cut.

The best strategy I think is to keep encouraging young and old people alike to foster an interest in basic science and electronics with places like EEVBLOG where people from all walks of life can learn. If anything, this Batteriser debate has done more to help promote EEVBlog than it has to market Batteriser. This is the best thing about having this open forum.

The more we discuss these and other projects, the more videos by Dave and others, the higher the search rank in Google, the word will get out to those who want to hear it. People have to want to hear it though. You can't force a fool to keep their money.

[edy]

On a different note... When you boost voltage don't you get a drop in current? Power is VxI so wouldn't the current drop as a result? This is assuming ideal zero loss converter. Devices don't just need voltage to run, they need a steady current to provide the power needed. The reason joule-thieves work is because an LED uses a tiny amount of current, much lower than what a drained battery puts out, so you can keep tapping the battery a long time. Remote controls and low current devices with very limited active states can also benefit if they have an issue with the voltage but can operate with little current. You just trade one for the other. I guess a well designed device is going to have something like a Batteriser build into it already. But even if it didn't, it seems only a few low current devices might benefit from this booster. Also, if you have a system in place at home to cycle your batteries from high drain devices down to medium and then low, you can milk a battery yourself and prolong it's use instead of chucking it into landfill. I keep my batteries and they often end up in the remote. Another trick is if the remote takes 2 batteries I sometimes switch the order of the batteries and it keeps going for a while longer. I should sell that on IndieGogo.... I'll call it the "Reorderiser".