Good idea but I think you found that the variables caught up with you. Pack size, discharge rate, cell temperature etc.

Not to say it's not a good idea but it would be hard to make money on a product where the capabilities already exist in current products which folks use regularly.

The other problem is how accurate can you get? If the tolerances are quite small then you won't have a problem but as you can see some of the chargers out with this capability vary widely.

I wish lipo manufacturers would adhere to a standard where they would have to supply their pack resistance ratings via some third party. This would eliminate alot of the bs which pervades our fun lipo indulging hobby.

B

This should be a good & useful tool in everyone's tool box. Great idea!

Maybe you can offer an option that would display via serial/usb connection to the PC and does not need to have box or LCD, just shrink wrap it. This should reduce the cost a bit. I think one cell measurement at a time would be fine too. Unless someone really wants to analyze battery, they wouldn't measure every cell every time the battery impedance every time they charge. And for those who wants high resolution, you can probably offer another design with 12 or 16 bit ADC?

just my 2 cents

-Thanh

I still personally think that a simple tester, like originally envisaged will have a place in the market at 1mR resolution, certainly helps a lot in diagnosing dud cells in a pack very quickly.

Variables like pack temperature aren't a problem, since that's something that affects all components but it doesn't stop us using multimeters. It's up to the person testing to make sure they take note of what the temperature is at the time.

Discharge rates, well I guess that's a factor to be noted and compared, eg, 4.2A vs 8.4A ... etc.

My personal view is that the original/simple version is what can be sold successfully up front initially.

A PC link version (without) LCD is also entirely possible in fact, as the product stands right now it does that (though only via standard RS232 serial, USB would cost another couple of dollars extra for the bridge chip).

Higher resolution ADCs would help too, certainly I often wish for a 12 bit ADC in these situations, alas without it being effectively built into the uC it's only going to mean even more components to allow MUX'ing of it.

Paul.
Paul.

the simple idea is the best options also

why does every one buy them small lipo voltage monitors(cell spy) even though a charger can do the same thing its because not ever one want to turn on there whole charging system just to see the Cells voltages so what if chargers have it bulit in

i think you should have a small product srinked raped and with a 3 sagnment led display

and 1mR is accepatable because most chargers are 1 mR and thing below 1mR is a whole new world as even resistoes are going to imbalance the and almost every thing in the circuit so i think 1mR is fine

version 1 make it cheap make it small and make it do the job and thats it

version 2 you can add all them extras like dc jack and all them pc data lines in this version

and one thing tho make version 1 the cheapest possible

if you can make version 1 ill put my order right now

Just an interesting fact about the device pictured above. I just came back from China, the street price for one of those in China is about 10 RMB (Chinese Yan) or US$1.43.

Paul, I think if you ever decided to produce this IRM, sitting at home and building them one by one is not an effective way to use of your time. I would work with prototype company in China and let them source the part and produce the SMD version for you. It probably would lower your cost to make the product marketable. If you are concern about firmware priacy, you can always have them build the device and program the device your self.

Brian

Brian

Hey there everyone, Brian and henal.

Brian, I know what you mean about getting them mass-produced over there and saving my own time here, however at this point it's the upfront costs that are a killer, for assembly (I've been quoted before) I need to pitch up for at least 100+ units.

So far as firmware etc theft, I think that as soon as the device is able to be purchased, it's as good as cloned. I tend to avoid having a lot of my products cloned purely because I wedge myself into markets where the turnover numbers are insufficient to gather enough interest.

henal,

Those voltspy things have always intregued me, for two reasons, they're so damned cheap (and they have an Atmel AVR on them!) but they're not the most accurate of devices. From what I've seen they just use a series of dividers to bring the voltage down to the level of the AVR (probably 3.3V) but the dividers are perhaps using 5% resistors. I won't need to go to using the 7-segment display anymore because I have found the LCD I want at a price that matches the cost of doing 3x7-segment.

Paul.

I did some testing and comparison of a number of those cell-voltage checkers last year. They are inaccurate and useless if you want to know the voltage to better than 0.1V. However they are very convenient and useful for checking which pack is charged and ready for use and which is awaiting recharging. Since they are so cheap, the inaccuracy is acceptable given the value they provide as a quick and easy way to check a pack. I keep one on my hobby bench near the chargers and one in my Tx case for use at the field.

I think there would be a market for Paul's device at 1mR accuracy but it would be limited to the tinkerers, measurebaters and geeks that just love to dig deeper into what's going on. I agree that at $60 it would be a tough sell in terms of perceived value to all but the most enthusiastic.

I think Paul's right on the money. Keep it as simple as possible and accurate enough to be really useful.

$60 seems fine to me. Anyone who is serious enough to want to know the R of their cells is probably commited enough to buy a quality product. If you flying cheap foamies with Chinese outrunners then $60 might seem a bit high, but then you don't really need to know the R of your cells either.

This is not another $10 gadget with an accuracy of +/-10%. This is a tool for those who need it.

Well, I'm going to order a lot of 20 LCD panels from the supplier, since I will be using this "format" for more than just the IRM. Things doing get much cheaper when I jump to 100 lots, so it's not a huge loss only going with 20 units.

Another thing that will make a difference is if I can stick with the 4K flash version of the mega AVR, as going to the 8K (mega88) pumps the price up a noticable couple of bob too.

Packaging/casing is still a killer, I can't really use shrinkwrapped because you need to get to the 9V battery on the back. I must use a physical on/off switch though because the voltage regulator consumes too much power even in 'idle' mode, so a physical on/off is the only way to go to ensure the battery doesn't go kaput in a day.

-edit- cut out price discussion -edit- still going over costs again -edit-

Paul.

I think it's incredibly important to both acknowledge and thank people like Paul who like us all both enjoy what we do, and take their enjoyment and inspiration and make something of it for all of us to benefit from.

There are $ involved - but nothing is free and everyone bears a cost.

What we DON'T get from 'mystery brand' etc. no name branded cheap (and very often unreliable) equipment is the level of interaction from the makers we get in threads like this.

Remember - a STACK of those cloned items came out of group discussions just like this, where one or more people took the lead and made the first versions without the benefit of mass production. Hey - love or hate MR GWS, where would we be without some of the great interaction with him over the years...

I happen to have the version 1 LiPo Cell normaliser Paul made - sure there was a premium involved in the purchase BUT it's quality is spot on (I can say I've got a hand made ), it does what it says and has saved me a lot of money in battery storage failures. Would I rely on a $15 version from some no name brand? - no, not when I have $100's of dollars worth of batteries....this is an example, but as Ralph pointed out if your budget = LOW always regardless of the quality of the item then you will inevitably get hit and miss items.

When you've spend good money on good items, adding weak points in the form of cheap goods is a false economy. We all know about spending big $ on an RC rig only to stick a cheap RX in it and lose the lot.

So - in summary (late night rant) - foster the thinkers and doers, appreciate there are different markets for different folk and when commenting on new products keep that in mind...not everyone WILL benefit or WILL want to, so take the perspective that any ideas are potentially good ideas and criticism (sometimes veiled as 'reality checks') are often not productive BUT if worded in a well thought out argument can be .

Hell - if we listed to all the reality check folks I wouldn't be typing on my laptop now, using my cool IPhone (yes I sold out) etc. etc.

Cheers!

Originally Posted by pldaniels

I still personally think that a simple tester, like originally envisaged will have a place in the market at 1mR resolution, certainly helps a lot in diagnosing dud cells in a pack very quickly.

Variables like pack temperature aren't a problem, since that's something that affects all components but it doesn't stop us using multimeters. It's up to the person testing to make sure they take note of what the temperature is at the time.

Discharge rates, well I guess that's a factor to be noted and compared, eg, 4.2A vs 8.4A ... etc.

My personal view is that the original/simple version is what can be sold successfully up front initially.

A PC link version (without) LCD is also entirely possible in fact, as the product stands right now it does that (though only via standard RS232 serial, USB would cost another couple of dollars extra for the bridge chip).

Higher resolution ADCs would help too, certainly I often wish for a 12 bit ADC in these situations, alas without it being effectively built into the uC it's only going to mean even more components to allow MUX'ing of it.

Paul.
Paul.

You'll need to do some research and gather some data, most folks would expect some explanation of what "proper" resistance of a LiPo is and what the numbers mean. If I were to use one I'd want to know how to grade my own packs, which would mean there would need to be measurements of other packs.

This has been an issue with the LiPo business for some time, why don't the manufacturers post this information, certainly they know it. If their excuse is the additional resistance added by the pack assemblers then the pack assemblers should measure and post this data. The idea that the single best determining factor to how a product performs is not stated, boggles my mind...

Jack

Just been lurking but Cudos on the uProc choosen.
I'm an Atmel fan myself with an old stk500 dev board etc.
LCD's can be found fairly cheap if you look long enough.
Not exactly sure re AU tho.
Then agian it appears that you are using a serial in LCD
which has got to be more expensive than doing the display yourself.
IF you have the ports and "room" for it.

I always thought THIS should be something that the garden variety Watt meters
should have included !

Birdofplay,

Fear not, I'm only using a serial LCD while I don't have the one I've designed the board for, it's simple another display option (I make the serial LCD boards myself, they've just got a nice simple tiny2313 on the back to do all the decoding via RS232).

For the "real" product I've already allocated the pins and board space for driving the LCD in nibble/4-bit mode.

Paul.

Paul.

Originally Posted by jfetter

The idea that the single best determining factor to how a product performs is not stated, boggles my mind...

Jack

Takes away their marketing "advantage".

Second "simple" prototype board has just been etched out... will be populating with the parts over the next couple of hours.

This board, I stripped out all the "extras" and just left it as simple as I can with a 2-load test configuration.

I've changed the LCD source that I'm going to get to a domestic supplier because the price ends up being much the same and it's slightly larger too.

Paul.