Battery % monitor that works with solar

[GUMPY]

This is where I am. I have been a Smartgauge user since pre-production days and have found them excellent at what they do. I know that there is an issue when using them with solar panels. I have recently fitted 400w of solar and a MPPT controller, problem is that I need some form of indication as to the state of charge of the batteries. I can use SG before I go to bed and when I first get up as the solar is inactive at those times cos its dark but even then I'm not 100% convinced its correct.  There is a meter of sorts in the controller  but that tells me very little. Charging current is up and down depending on the sun so even that's not an indication. 

So what I am asking is there an accurate meter that works with solar, anything that counts amps in and out and gives a % reading is inherently inaccurate due to battery age etc.

So is there anything out there?

 

[Robbo]

Nope.  An "Amp Counter" is prob the better monitor if you have solar and you keep it configured for battery size.

[GUMPY]

57 minutes ago, Robbo said:

Nope.  An "Amp Counter" is prob the better monitor if you have solar and you keep it configured for battery size.

But there is no easy way to know what the battery size is, capacity decreases with age/use

[Robbo]

12 minutes ago, Loddon said:

But there is no easy way to know what the battery size is, capacity decreases with age/use

And that’s why there is no real accurate monitor unless you want to spend some big bucks like on the datacell.  The amp counter will be accurate on the other stuff as long as you put the correct parameters in for charging, this really only needs to be done once.   Ones like the Victron reset the count when fully charged based on voltage and incoming amps so you should know when they are at 100.

[Tony Brooks]

and the conversion of  electricity to chemical efficiency plus chemical to electricity will alter over time and temperature.

[mrsmelly]

3 minutes ago, Robbo said:

And that’s why there is no real accurate monitor unless you want to spend some big bucks like on the datacell.  The amp counter will be accurate on the other stuff as long as you put the correct parameters in for charging, this really only needs to be done once.   Ones like the Victron reset the count when fully charged based on voltage and incoming amps so you should know when they are at 100.

Whats a Datacell? how much is big bucks?

Taa

[Robbo]

Just now, mrsmelly said:

Whats a Datacell? how much is big bucks?

Taa

It’s Gibbos smartguage 2 thingy.  About a grand I think.

[mrsmelly]

1 minute ago, Robbo said:

It’s Gibbos smartguage 2 thingy.  About a grand I think.

Thanks I hadn't heard of it. Has anyone got one?

[WotEver]

3 minutes ago, mrsmelly said:

Thanks I hadn't heard of it. Has anyone got one?

The military here, the US, and elsewhere. Not sure about any boaters though. 

http://www.merlinpowersystems.com/wp-content/uploads/2014/06/MPS-DataCell-II.pdf

http://www.merlinpowersystems.com/products/products-commercial/products-commercial-battery-monitoring/

The latter link should be cheaper as it's the non-military version. 

[mrsmelly]

2 minutes ago, WotEver said:

The military here, the US, and elsewhere. Not sure about any boaters though. 

http://www.merlinpowersystems.com/wp-content/uploads/2014/06/MPS-DataCell-II.pdf

Thanks for that. I would definitely consider one of those but do the panel think it would take ages to get the grand back and just still be cheaper for us boaters to buy batteries every 2/3 years anyway? I have just replaced my set at about 360 quids that should last another 2 and a half years but a PROPER monitor looks good?

[cuthound]

30 minutes ago, Loddon said:

But there is no easy way to know what the battery size is, capacity decreases with age/use

Agreed. You can test discharge the battery to a known load, ideally increasing the load when the current drops because the battery voltage has dropped, to keep the current approximately evenue over time.

Problem is to establish the actual capacity,  you ideally need to flatten the battery to about 1.85 volts per cell, before immediatey charging them fully. However this will  impact overall battery longevity for all except traction cells.

Alternatively, if you have an amp-hour counting meter, you can discharge from 100% to say 50%, measure the amp hours used, and double them to get the approximate capacity.

 

[Robbo]

5 minutes ago, cuthound said:

Alternatively, if you have an amp-hour counting meter, you can discharge from 100% to say 50%, measure the amp hours used, and double them to get the approximate capacity.

This is how I tend to do it.  Just discharge to a settled voltage and then check how many amps I’ve used.  Not the best but life to short to care.

[smileypete]

Just eye the batt voltage first or last thing, don't obsess over it.

I'd bet there's typically far more capacity reduction from inadequate charging than wear and tear due to modest discharge below 50%...

Smartgauge is not a panacea, though it works very well, at least until you realise it's not a panacea etc etc....

Edited July 27, 2017 by smileypete

[nicknorman]

2 hours ago, Loddon said:

This is where I am. I have been a Smartgauge user since pre-production days and have found them excellent at what they do. I know that there is an issue when using them with solar panels. I have recently fitted 400w of solar and a MPPT controller, problem is that I need some form of indication as to the state of charge of the batteries. I can use SG before I go to bed and when I first get up as the solar is inactive at those times cos its dark but even then I'm not 100% convinced its correct.  There is a meter of sorts in the controller  but that tells me very little. Charging current is up and down depending on the sun so even that's not an indication. 

So what I am asking is there an accurate meter that works with solar, anything that counts amps in and out and gives a % reading is inherently inaccurate due to battery age etc.

So is there anything out there?

 

I would say a combination of the Smartgauge you already have, and an AH counting gauge, preferably one that automatically calculates CEF.

The SG will tell you the SoC during discharge (at night, or in very dark skies) but isn't particularly good during charge -either via alternator, shore power or solar. The combination allows you to work out the actual capacity provided  from time to time you get to 100% on both devices, followed by a significant discharge (say, below 75% SoC). This allows you to tweak the capacity on the AH counter to the actual capacity. The AH counter is good for knowing when the batteries are fully charged (ie voltage up at absorption, current below 1% or whatever.

[WotEver]

34 minutes ago, mrsmelly said:

Thanks for that. I would definitely consider one of those but do the panel think it would take ages to get the grand back and just still be cheaper for us boaters to buy batteries every 2/3 years anyway? I have just replaced my set at about 360 quids that should last another 2 and a half years but a PROPER monitor looks good?

You'd never get yer grand back but it would be fun to own one. 

[GUMPY]

One thing I didnt say is that it has to be useable by my dear lady wife.........came home earlier this week (when it had been raining and dull all day) and had to switch the mains charger on as voltage was down to 12.25 caused  by a combination of watching DVDs and the diesel heating with no sun......... its needed so she can check before using stuff as you may guess calculating amps in/out is a non starter. Another problem is if the batteries are between 55 and 85% voltage will be in the high 14's and current somewhere about 20amps if the sun is out all that tells me is that they are not fully charged not by how much.

Guess its back to what I did 16+ years ago and use intuition with a little assistance from a volt meter 

[MtB]

Before I bought my first SmartGauge I asked on here if they worked with solar panels installed. 

I got an emphatic YES!

Plus ca change...

[rusty69]

2 minutes ago, Mike the Boilerman said:

Before I bought my first SmartGauge I asked on here if they worked with solar panels installed. 

I got an emphatic YES!

Plus ca change...

I'll give you a tenner for yours

[MtB]

5 minutes ago, rusty69 said:

I'll give you a tenner for yours

 

But it doesn't work...

Is yours broken too?

[rusty69]

1 minute ago, Mike the Boilerman said:

 

But it doesn't work...

Is yours broken too?

Then its easy money! 

[WotEver]

22 minutes ago, Mike the Boilerman said:

Before I bought my first SmartGauge I asked on here if they worked with solar panels installed. 

I got an emphatic YES!

Yup. ''Tis true.

[GUMPY]

I've had an idea involving a push button, contactors and a dummy load........... 

More later........... probably much later.

[rusty69]

1 minute ago, Loddon said:

I've had an idea involving a push button, contactors and a dummy load........... 

More later........... probably much later.

Is it a water pump? 

[cuthound]

1 minute ago, Loddon said:

I've had an idea involving a push button, contactors and a dummy load........... 

More later........... probably much later.

When I got my boat it was 7 years old, as we're the 660ah Lifeline AGM leisure batteries in it.

I used the halogen cabin lights to fully discharge at the 10 hour rate. It proved the batteries had around 70% of their capacity.

Since then I have calibrated the ah meter to reflect the smaller capacity, and use that and the resting voltage to check the approximate capacity and recalibrate the battery capacity on the BMV if necessary . Last time I checked the battery was down to 63% of its capacity.

[nicknorman]

58 minutes ago, Loddon said:

One thing I didnt say is that it has to be useable by my dear lady wife.........came home earlier this week (when it had been raining and dull all day) and had to switch the mains charger on as voltage was down to 12.25 caused  by a combination of watching DVDs and the diesel heating with no sun......... its needed so she can check before using stuff as you may guess calculating amps in/out is a non starter. Another problem is if the batteries are between 55 and 85% voltage will be in the high 14's and current somewhere about 20amps if the sun is out all that tells me is that they are not fully charged not by how much.

Guess its back to what I did 16+ years ago and use intuition with a little assistance from a volt meter 

But surely in the specific case you cite, the Smartgauge will have been reading a fairly low SoC giving a clue that all wasn't right with energy supply? People say the SG doesn't work well with solar but there has never been any hard evidence, has there?

i have a SG and an AH counting gauge. During discharge they are usually pretty close to each other. If the AH-counting gauge has the correct capacity entered and you fully charge the batteries fairly often, the SoC indicated by it will be pretty accurate. I don't see that this would be difficult for your wife to interpret, it's just a % SoC like the Smartgauge.