Designing 12v charging system from scratch

[MtB]

On 09/12/2017 at 12:50, Loddon said:

Thing is Mike even if they are recalibrated as you have solar they will lie to you when your solar is active especially if the solar is only lifting the battery voltage slightly and not putting in a significant charge. They will however be accurate after a couple of hours darkness and then remain like that until the next dawn.  I find 3am as one is on the way to have the middle of the night wee a good time to check SOC 

 

Good point which deserves more dissection.

Before I bought my first Smartgauge, I asked on here if they were messed up by solar panel input and Nick (I think it was) stated emphatically that no the Smartgauge takes solar charging in its stride. I couldn't quite see how, imagining the effect you describe but I went ahead and bought one anyway.  

Later, when it began to emerge I had a major problem with the Smartgauge lying, my doubts about how it coped with solar got pushed to the back of my mind. It probably warrants a separate thread on the subject.

[rusty69]

I thought everyone could see their Smartgauge from bed,. 

[MtB]

On 09/12/2017 at 13:40, rusty69 said:

I thought everyone could see their Smartgauge from bed,. 

 

Nope. One of mine is in the galley and the other in the engine room. Neither is visible from my bed.

If I levae the engine room door open though I can amuse myself looking at how different to two readings are though! Curiously they both read the same now. First time I've ever noticed this!

Mind you, they are probably both wrong according to the manual, as the readings both say 100%.

[rusty69]

3 minutes ago, Mike the Boilerman said:

 

Nope. One of mine is in the galley and the other in the engine room. Neither is visible from my bed.

If I levae the engine room door open though I can amuse myself looking at how different to two readings are though! Curiously they both read the same now. First time I've ever noticed this!

Mind you, they are probably both wrong according to the manual, as the readings both say 100%.

Wow, you have two. Impressive. 

[MtB]

On 09/12/2017 at 13:50, rusty69 said:

Wow, you have two. Impressive. 

 

Didn't you know?

I'm thinking about buying a third, just for a laugh.

It might even work!

[rusty69]

6 minutes ago, Mike the Boilerman said:

 

Didn't you know?

I'm thinking about buying a third, just for a laugh.

It might even work!

I don't think you'll get one for £5.50

[GUMPY]

35 minutes ago, Mike the Boilerman said:

Before I bought my first Smartgauge, I asked on here if they were messed up by solar panel input and Nick (I think it was) stated emphatically that no the Smartgauge takes solar charging in its stride. I couldn't quite see how, imagining the effect you describe but I went ahead and bought one anyway.  

Gibbo's view on how accurate SG is with solar

This is a question that comes up time after time. The answer is a lot simpler than you’d think. If the solar panel is fully charging the batteries, SmartGauge is accurate throughout any period using them. It  only appears to be inaccurate for the first 10% to 15% of the following discharge cycle. After that, all is good. If the solar panel is not fully charging the batteries (the usual situation in the UK) then it is accurate throughout any period using them. it’s just that a human’s idea of state of charge during intermittent solar charging doesn’t map well with reality. It’s the human that is wrong!]

[WotEver]

3 hours ago, Mike the Boilerman said:

Secondly, the Smargauge will tell you when the batteries are 100% charged but it is usually wrong, even on a correctly calibrated Smartgauge

On what do you base that assertion, Mike?

It can be early, it can be late. I’m not aware that it’s “usually” wrong. The only person I can recall on this discussion group to have ever checked it is Nick, and he reckons his is between 1%-2% accurate at 100%. 

Besides, the post of mine that you quoted never suggested that it should be used for this purpose. I haven’t suggested that anywhere in this thread. I specifically said “use an ammeter” to determine full charge. 

You love banging on about how inaccurate some have been yet you still haven’t proved that either of yours are by returning them to Merlin. 

[MtB]

On 09/12/2017 at 15:18, WotEver said:

On what do you base that assertion, Mike?

 

The fact that my battery bank got destroyed by me stopping charging when the Smartgauge said 100%. Remember? 

 

On 09/12/2017 at 15:18, WotEver said:

You love banging on about how inaccurate some have been yet you still haven’t proved that either of yours are by returning them to Merlin. 

 

I don't need Merlin to tell be they are wrong. They are both connected to the same battery bank and return wildly differing results. So they can't BOTH be right can they?

And checking them with a correctly calibrated voltmeter, they turned out BOTH to be wrong. Or have you forgotten that too?

 

[rusty69]

2 minutes ago, Mike the Boilerman said:

 

The fact that my battery bank got destroyed by me stopping charging when the Smartgauge said 100%. Remember? 

 

Coupled with charging less often than perhaps you should  

[MtB]

On 09/12/2017 at 16:01, rusty69 said:

Coupled with charging less often than perhaps you should  

 

Oi, stop muddying the water! The Smartgauges are still both calibrated wrongly.

 

[rusty69]

8 minutes ago, Mike the Boilerman said:

 

Oi, stop muddying the water! The Smartgauges are still both calibrated wrongly.

 

Sorry mtb its, "My fault",I'm jus "still a fool" ,I'm  "messin with ya man",I've "got my mo jo workin", I jus "can't be satisfied"

Edited December 9, 2017 by rusty69

[MtB]

On 09/12/2017 at 16:16, rusty69 said:

Sorry mtb its, "My fault",I'm jus "still a fool" ,I'm  "messin with ya man",I've "got my mo jo workin", I jus "can't be satisfied"

I knew that.....

[rusty69]

1 minute ago, Mike the Boilerman said:

I knew that.....

[cereal tiller]

1 hour ago, WotEver said:

On what do you base that assertion, Mike?

It can be early, it can be late. I’m not aware that it’s “usually” wrong. The only person I can recall on this discussion group to have ever checked it is Nick, and he reckons his is between 1%-2% accurate at 100%. 

Besides, the post of mine that you quoted never suggested that it should be used for this purpose. I haven’t suggested that anywhere in this thread. I specifically said “use an ammeter” to determine full charge. 

You love banging on about how inaccurate some have been yet you still haven’t proved that either of yours are by returning them to Merlin. 

Smart Gauge calibrates itself.

[rusty69]

2 minutes ago, cereal tiller said:

Smart Gauge calibrates itself.

Smart Gauge owners, however, remain un-calibrated

Edited December 9, 2017 by rusty69

[WotEver]

33 minutes ago, Mike the Boilerman said:

The fact that my battery bank got destroyed by me stopping charging when the Smartgauge said 100%. Remember? 

So because your SmartGauge was telling fibs when it reported 100% charged you feel justified in making the assertion that all Smartgauges are “usually wrong”?

[MtB]

On 09/12/2017 at 16:32, WotEver said:

So because your SmartGauge was telling fibs when it reported 100% charged you feel justified in making the assertion that all Smartgauges are “usually wrong”?

 

Yep. Especially as backed up by the manual.

'For this reason it may not be wise to place too much faith in the charge status during charging. SmartGauge
will certainly give a very good indication (certainly better than an amp hours counter – and certainly better
than a volt meter [which will tell you nothing more than that the batteries are charging]) but it could be that
SmartGauge shows the charge status to have reached (as a worst case example) 100% when in actual fact
the batteries have only reached 90%.'

[WotEver]

So you believe that “could” means the same as “usually”. Okay. 

[MtB]

On 09/12/2017 at 17:37, WotEver said:

So you believe that “could” means the same as “usually”. Okay. 

 

Ok lets get this straight. 

Do you now hold that the Smargauge is a suitable instrument for determining when batteries are fully charged?

Or do you consider the Smartgauge cannot be relied upon for this task?

[WotEver]

1 hour ago, Mike the Boilerman said:

 

Ok lets get this straight. 

Do you now hold that the Smargauge is a suitable instrument for determining when batteries are fully charged?

Or do you consider the Smartgauge cannot be relied upon for this task?

I believe that you should use SmartGauge for what it’s designed for, which is to give a pretty accurate SoC reading when using your batteries. 

As I suggested earlier in this thread (twice, I believe, or perhaps three times?) the best device for determining close to 100% SoC when charging is an ammeter. You will probably find (unlike your assertion) that SmartGauge is pretty accurate too, although it shouldn’t be relied upon. Just like it says in the manual. 

[Tony Brooks]

I also think that a Smartgauge will stay far more accurate  than an amp hour counter that has been fitted and not set up being used by a boater with no inclination to    alter things. Nick says one such meter make sets the tail current too high so it synchs too early.

If you can be bothered to learn a but about batteries and charging then a digital ammeter and voltmeter is more than adequate for battery monitoring but if you can't then a Smartguage and ammeter is the best you can do.

[smileypete]

Haven't read every reply in detail but here's my thoughts:

Somewhere in another topic I suggested three main scenarios for batt ownership:

    Plan A for most (95%?) of boaters would be decent brand leisure batts.

    Plan B would be Trojans but only if they can be provided with the correct charge and EQ voltages, and required maintenance and monitoring. I expect this needs a genuine long term interest, hmmm...

    Plan C is to use a less common battery make/type/chemistry/desulphators etc, but then you may be the guinea pig on that one.

I guess most second home type boats fall into Plan A, and most off grid liveaboards move towards Plan B at some point.

Sounds like the OP is firmly 'Plan A' at this point and using the boat while moored in a marina with a shoreline and I guess will stay that way through the winter. So the initial step might be best to get some decent brand leisure batts (Numax, Varta, Banner) and a modest charger to keep them topped up, I made a suggestion for a charger on the other topic:

Later on when circumstances change might be a good time to think about battery monitoring (Smartgauge? ammeter?) and possibly a decent solar setup if warranted. A lot may depend on how much the inverter will be used when off grid...

I guess you could split 'Plan A' down between those having very modest electrical demands or very occasional use off grid, and those with large inverter expecting something akin to a shore based lifestyle while off grid, with the majority in between somewhere.

 

Edited December 9, 2017 by smileypete

[smileypete]

32 minutes ago, Tony Brooks said:

I also think that a Smartgauge will stay far more accurate  than an amp hour counter that has been fitted and not set up being used by a boater with no inclination to    alter things. Nick says one such meter make sets the tail current too high so it synchs too early.

If you can be bothered to learn a but about batteries and charging then a digital ammeter and voltmeter is more than adequate for battery monitoring but if you can't then a Smartguage and ammeter is the best you can do.

I reckon once people properly get the hang of 'tail current' then it's not a huge step to correctly set up an amp hour counter and understand it's shortcomings.

Trouble is some (most?) canal or riverboat owners want a 'fit and forget' type box with no instruction manual reading needed, and so their batts die slowly or not so slowly in the meantime.

[WotEver]

1 hour ago, smileypete said:

I reckon once people properly get the hang of 'tail current' then it's not a huge step to correctly set up an amp hour counter and understand it's shortcomings.

Trouble is some (most?) canal or riverboat owners want a 'fit and forget' type box with no instruction manual reading needed, and so their batts die slowly or not so slowly in the meantime.

I agree that your first para is how things should work out however your second para I think sums up the reality more closely. I know that Tony B speaks from long experience of dealing with boaters’ woes when referring to Ah counter failings.