BM1 monitor goes haywire!!

[Seajet]

For some reason people seem to give a lot more credibility to a measured figure that is in digital format than when the same information is in analogue. This is especially true if there are lots of significant figures on the display. It is a well known phenomenon, and is known as the digital deception. Marketing people love it.

Angus,

I presume you mean the capacity display on the BM-1 ? I do know the digital deception phenomenon, it always amuses me when people trust depthsounders down to .1 !

 

[AngusMcDoon]

When SmartGuage first came out nobody believed it could do what it claimed - even James Hortop (manager of Merlin and ex tec editor at PBO) didn't believe it - and then he bought the company.

The SmartGuage designer is a bit of an electronics genius who is now locked in a cupboard with no contact with the outside world. He is developing new cleverer software for the US military, so someone believes in him.

The whole point about the SmartGuage software is it learns about your batteries as they charge/discharge - reading the voltage 1100 times a second. The older the batteries get the more accurate SmartGuage gets.

I've tried for two years to programme my battery monitor to make it get even close to what I think my batteries are doing, without success. My AGM batteries are now ten years old so I have no real idea what their capacity is. That is a major problem for a BM. My Peukerts value will also be changing with age, and because that has a logarithmic effect on the Ah reading a small difference from 1.15 to 1.17 can have a large effect on the displayed Ah. Also an accurate charging Ah count is affected by the “efficiency” of the battery at accepting charge. Wet cells may need 130Ah put in to register 100Ah, whereas AGMs may only need 102Ah. If all these values or not input correctly, or they change with age it will upset the Ah count accuracy.

I agree that the Smartguage is better than the Nasa simplistic Peukert's Law method. However, I stand by my claim that 0.1% is just not believable. The sensors that measure the current and voltage and the voltage references they rely on will not have that sort of temperature compensated accuracy. The reason why I know this is because if they did, firstly the device would be a lot more expensive than it is, and secondly it would need periodic calibration. Sitting at my bench right now I am surrounded by cheap and expensive measuring devices. The expensive ones are very expensive, and are regularly sent off for checking and adjustment. But if it makes you happy to believe that 2nd decimal place, that's fine by me.

 

[Jabamusic]

With what seems to be a general consensus that like all politicains battery monitors are liars..was there not a recent thread (at work- so can't spend too much time searching ), which suggested a cheap voltage monitor was adequate rather than paying £100 for a BM1 for example - or alot more for other makes?

Did anybody have any adequate results with such an item?

 

[AngusMcDoon]

Angus,

I presume you mean the capacity display on the BM-1 ? I do know the digital deception phenomenon, it always amuses me when people trust depthsounders down to .1 !

Even the voltage and current measurements on the Nasa kit will not be accurate. They will be using the absolute cheapest measuring components being Nasa. 1% at best, and probably not temperature compensated. The capacity measurement is just an educated guess.

 

[halcyon]

I agree that the Smartguage is better than the Nasa simplistic Peukert's Law method. However, I stand by my claim that 0.1% is just not believable. The sensors that measure the current and voltage and the voltage references they rely on will not have that sort of temperature compensated accuracy. The reason why I know this is because if they did, firstly the device would be a lot more expensive than it is, and secondly it would need periodic calibration. Sitting at my bench right now I am surrounded by cheap and expensive measuring devices. The expensive ones are very expensive, and are regularly sent off for checking and adjustment. But if it makes you happy to believe that 2nd decimal place, that's fine by me.

Why do you want accuracy to a high degree, is + / - 5% critical, recharging at 45% or 55% is not going to destroy your battery, or equally your not going to run out of power.

Voltage to capacity varies with lots of things, as said earlier in the thread, a new battery charged voltage will rise to around 13 volt, then over time fall to 12.7 - 12.8, then start falling when getting old. Equally the charge voltage will vary by charge rate and battery age, so saying any voltage is 100% charge is highly optimistic.

Brian

 

[AngusMcDoon]

Why do you want accuracy to a high degree.

I don't. I was just disagreeing with accuracy claims of 0.1%.

Voltage to capacity varies with lots of things, as said earlier in the thread

I agree. It was me that wrote that.

 

[sailinglegend420]

.... I stand by my claim that 0.1% is just not believable.......

I'm not interested in an accuracy of 0.1% - I'm just quoting the MD of Merlin whom I know quite well. If you multiply this in-accuracy by 50 then it would still be 5% accurate - that's a lot better than any other BM!

The sensors that measure the current and voltage and the voltage references they rely on will not have that sort of temperature compensated accuracy.......

The SmartGuagae doesn't measure current so that just shows how much you know about it!

It's not a cheap product so there is no reason it's components aren't doing the job properly.

 

[AngusMcDoon]

The SmartGuagae doesn't measure current so that just shows how much you know about it!

I'm aware how the Smartguage works thanks. I was talking about these types of instruments in general. Others do measure current, including one I have done development work on in the past.

It's not a cheap product so there is no reason it's components aren't doing the job properly.

I didn't say they weren't. They will be working to their specification. However, I guess you have never worked in consumer electronics manufacture, because there is little relationship between a product's selling price and the quality of the components.

I'm not interested in an accuracy of 0.1% - I'm just quoting the MD of Merlin whom I know quite well. If you multiply this in-accuracy by 50 then it would still be 5% accurate - that's a lot better than any other BM!

As I said before, you believe whatever value makes you happy. The reality will be different, but it's not a critical measurement; nobody's life depends on it. It's not easily verifiable either, so a great opportunity for a product and some slick marketing to part people from their money.

 

[sailinglegend420]

.... It's not easily verifiable either, so a great opportunity for a product and some slick marketing to part people from their money.

I don't understand why you are so down on a product you don't know or understand. The accuracy I mentioned of 0.1% was given to me by the MD in a private conversation. Nowhere do they use this kind of claim in their marketing.

 

[AngusMcDoon]

I don't understand why you are so down on a product you don't know or understand. The accuracy I mentioned of 0.1% was given to me by the MD in a private conversation. Nowhere do they use this kind of claim in their marketing.

I do know the product thank you. I don't know the algorithm, but then neither do you, as it's a trade secret. I'm not down on it and agree that it is better than a Peukert's Law based one. However, I am sceptical of some things they claim, and don't believe it is worth the cost for a boat, but happy for others to disagree on its worth.

I only came into this discussion to point out that the 0.1% accuracy you mentioned, however you obtained that figure, is not realistic, a premise I stand by. I'm an engineer, a geek, a nerd and a dweeb. Figures like that matter to me. Sad, I know, but it's my life's work. I can't help it.

 

[tokoloshe]

I don't understand why you are so down on a product you don't know or understand. The accuracy I mentioned of 0.1% was given to me by the MD in a private conversation. Nowhere do they use this kind of claim in their marketing.

Because he's a clever dick!