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My third SmartGauge...


MtB

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12 hours ago, Peter Thornton said:

Have to say, I don’t really understand the principle on which they work. We have been using a voltmeter to monitor SOC and, as anyone who’s tried this knows, the problem is that the volts measured varies with the load on the batteries. So I guess that one function of the Smartgauge is to smooth all of these variations out.

No it doesn’t just smooth the voltage out, that wouldn’t really work. As we know, SoC can be determined from rested no load voltage. If you now turn on a load, the voltage takes a step change, and then slowly decreases as the battery discharges. Turn other thing on or off, you get different step changes and rates of voltage decrease. You can make a stab at a relationship between voltage step change and current (as a % of capacity) and hence SoC. At some time the voltage may stabilise (everything off) and the box can re-evaluate the SoC using rested no load voltage. If the answer is different from that calculated so far, it can modify the constants used to link step change with %current (learning process). Obviously the reality is much more complicated than that.

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Did my first cruise with Smartgauge today.

 

Started with 66% showing and it climbed nicely for the first 3 hours then slowed and ended up at 94% when I moored. I assumed that was because I have a standard charging system with no trickery?

 

But this evening I’ve been reading some old posts and come across one that says they have a tendency to show 94%. Is this just co-incidence?

 

Just to avoid a three page note on batteries and charging, (!) I’ve always understood that it’s unlikely/impossible to get to 100% whilst cruising with a standard car based alternator set up.

 

So, is this 94% thing a feature?

 

But I’m very pleased with the Smartgauge so far. It seems to work exactly as promised.

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12 minutes ago, Peter Thornton said:

Did my first cruise with Smartgauge today.

 

 

 

Just to avoid a three page note on batteries and charging, (!) I’ve always understood that it’s unlikely/impossible to get to 100% whilst cruising with a standard car based alternator set up.

 

 

What voltage were you charging at as you finished your cruise?

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11 minutes ago, Peter Thornton said:

Just to avoid a three page note on batteries and charging, (!) I’ve always understood that it’s unlikely/impossible to get to 100% whilst cruising with a standard car based alternator set up.

Not True...... if the charging voltage is 14.2 or above.

An old 1970s 13.8v alternator would however be unlikely to reach 100% on a normal day.

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Just now, Peter Thornton said:

Good question! I’ll check next time .......

As Loddon says, your abilty to get fully charged will be down to the voltage. If you are up over 14.2 (ish) V then you should be able to get fully charged - but what capacity is your battery bank?

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1 minute ago, Dr Bob said:

As Loddon says, your abilty to get fully charged will be down to the voltage. If you are up over 14.2 (ish) V then you should be able to get fully charged - but what capacity is your battery bank?

It’s 4, 100AH batteries. I’ll check the charging voltage tomorrow.

I do know that when we return to the Marina after a long cruise and hook up the onboard charger (Sterling Pro) it does put quite a bit more in. It’s difficult to track exactly how much as the current keeps varying but probably 20 - 30 AH’s in total.

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4 minutes ago, Peter Thornton said:

It’s 4, 100AH batteries. I’ll check the charging voltage tomorrow.

I do know that when we return to the Marina after a long cruise and hook up the onboard charger (Sterling Pro) it does put quite a bit more in. It’s difficult to track exactly how much as the current keeps varying but probably 20 - 30 AH’s in total.

If I use 100Ahr overnight - so am 100Ahrs off full, I will be down to a 1% tail current after 4 hrs running ...using a 90A alternator. In your case you were putting in circa 120Ahr (66% to 100% assuming your capacity is slightly down) so should be not far off full ....but you didnt say how long ...3hrs +?

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7 minutes ago, Dr Bob said:

If I use 100Ahr overnight - so am 100Ahrs off full, I will be down to a 1% tail current after 4 hrs running ...using a 90A alternator. In your case you were putting in circa 120Ahr (66% to 100% assuming your capacity is slightly down) so should be not far off full ....but you didnt say how long ...3hrs +?

You use 100 Ahr overnight. Wot are you doing man, that's nearly a whole armful! 

Edited by rusty69
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44 minutes ago, Peter Thornton said:

Did my first cruise with Smartgauge today.

 

Started with 66% showing and it climbed nicely for the first 3 hours then slowed and ended up at 94% when I moored. I assumed that was because I have a standard charging system with no trickery?

 

But this evening I’ve been reading some old posts and come across one that says they have a tendency to show 94%. Is this just co-incidence?

 

Just to avoid a three page note on batteries and charging, (!) I’ve always understood that it’s unlikely/impossible to get to 100% whilst cruising with a standard car based alternator set up.

 

So, is this 94% thing a feature?

 

But I’m very pleased with the Smartgauge so far. It seems to work exactly as promised.

I’ve never noticed a tendency to stick at 94%. But then we have a modern alternator that charges at around 14.5v. We go from say 65% on starting the engine in the morning, to 100% by early afternoon. As has been said, perhaps your charging voltage is on the low side?

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Just now, rusty69 said:

Mrs Bob shouldn't be drinking coffee overnight:)

No, that's two cups in the morning before we get going. That's still overnight on our boat!? .....so that's sort of 5pm ish to the time we get up and start the engine.

Have you tried an Nespresso machine - IIRC its about 140A? Awful coffee. I drink instant.

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Just now, Dr Bob said:

No, that's two cups in the morning before we get going. That's still overnight on our boat!? .....so that's sort of 5pm ish to the time we get up and start the engine.

Have you tried an Nespresso machine - IIRC its about 140A? Awful coffee. I drink instant.

Never mind the Taste  ,it makes Laydees think of George Clooney..

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22 minutes ago, Dr Bob said:

If I use 100Ahr overnight - so am 100Ahrs off full, I will be down to a 1% tail current after 4 hrs running ...using a 90A alternator. In your case you were putting in circa 120Ahr (66% to 100% assuming your capacity is slightly down) so should be not far off full ....but you didnt say how long ...3hrs +?

It was just over 3 hours - well guessed!

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15 minutes ago, rusty69 said:

You use 100 Ahr overnight. Wot are you doing man, that's nearly a whole armful! 

I deliberately provoked it by leaving lots of lights on as I wanted to test it out and give it a chance to calibrate itself. This evening’s been much quieter and it’s moved from 94% to 90% so about 12 Amp/Hour or so (bearing in mind that 4x100 doesnt equal 400 when they have some age.

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2 minutes ago, Peter Thornton said:

I deliberately provoked it by leaving lots of lights on as I wanted to test it out and give it a chance to calibrate itself. This evening’s been much quieter and it’s moved from 94% to 90% so about 12 Amp/Hour or so (bearing in mind that 4x100 doesnt equal 400 when they have some age.

Leaving lots of lights on our boat wouldn't make a dent in the batteries...... They're all leds:)

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