Mppt charger question

[dianah]

Hello! Electrics question... When running my engine, my mppt solar charge controller alway shows 'float' today it shows 'bulk' although my smart gauge is measuring that the batteries are charging. Is this a sign of something to worry about? Batteries on the way out or alternator problem maybe? Thanks in advance

[Phil.]

I would have thought this is how it should be. My controller is in bulk mode even when engine charging and will only switch to float after a fairly long period of absorbing, or if the batteries have been fully charged and left in that state unused.

[Top cat]

I agree with Phil I would only start to worry if the solar controller continues to show bulk after the Smart gauge shows full for some time. Do you have an ammeter in the charging circuit? You can consider the batteries charged once the current flls to less thn 2% of the battery capacity or does not change for 45 minutes. At this time of year your are getting almost nothing out of your solar panels so the batteries will be lower and the other charging methods have more to do.

 

Top Cat

[dianah]

Thank you both! Think all is ok, it switched to absorption once the smart gague showed 95%. It normally goes to absorption before that but then again the solar panels are normally keeping me topped up. Maybe the smart gague isn't an exact science and maybe the batteries were emptier than I thought. Thanks again

[matty40s]

It depends on when you looked at it.

If youre batteries were quite depleted prior to charging with engine, the alternator reading on the smartgauge will not immediately show 14.6V, more like 13.8 as this reading is taken from the batteries, not the alternator.This will slowly creep up as it puts a lot more oomph into the batteries.

Most MPPT controllers have a bulk charge of 14.4V - so until you're alternator raises the voltage on the meter above this, the MPPT will remain in bulk charge.

[Top cat]

The smart gauge is less accurate during charging than discharging. I seem to recall that the error during charging can be as much as 15% but I'm sure the true believers will be along to challenge that.

 

Top Cat

[Phil.]

I also have a smart gauge and that does not appear to accurately read solar charge. I believe there is info on this somewhere on this forum or alternatively an expert will be along to explain. As an example my smart gauge often displays SoC 100 but the solar charger is still supplying significant current to the batteries thereby indicating that whilst the SG says the batteries are full, they are not.

[rusty69]

I also have a smart gauge and that does not appear to accurately read solar charge. I believe there is info on this somewhere on this forum or alternatively an expert will be along to explain. As an example my smart gauge often displays SoC 100 but the solar charger is still supplying significant current to the batteries thereby indicating that whilst the SG says the batteries are full, they are not.

It is said that the smartgauge can be inaccurate by up to 10% whilst charging (particularily whilst a charge source has a low output)

Edited November 5, 2016 by rusty69

[Murflynn]

I agree with Phil I would only start to worry if the solar controller continues to show bulk after the Smart gauge shows full for some time. Do you have an ammeter in the charging circuit? You can consider the batteries charged once the current falls to less than 2% of the battery capacity or does not change for 45 minutes. At this time of year your are getting almost nothing out of your solar panels so the batteries will be lower and the other charging methods have more to do.

 

Top Cat

please can you clarify that you mean current falling to 4A for a 220AH bank?

[rusty69]

 

Edited November 5, 2016 by rusty69

[WotEver]

please can you clarify that you mean current falling to 4A for a 220AH bank?

I can't speak for TC but yes, around 2% of battery capacity or when it hasn't dropped for about 45 minutes, which should be much the same thing.

It is said that the smartgauge can be inaccurate by up to 10% whilst charging (particularily whilst a charge source has a low output)

Spot on. The SmartGauge is very accurate on discharge but an ammeter should be used to determine 100% as above. (Bearing in mind that true 100% is unattainable.)

 

.. my smart gauge often displays SoC 100 but the solar charger is still supplying significant current to the batteries thereby indicating that whilst the SG says the batteries are full, they are not.

Bear in mind that if anything at all is switched on then the panels will be supplying that.

[Top cat]

please can you clarify that you mean current falling to 4A for a 220AH bank?

 

During charging the voltage rises to typically 14.4V (Depending on type) and then is held at that and the current will start to drop as the battery approaches full charge. Once the current has dropped to 2% of the rated battery capacity most experts will consider it charged.

 

Top Cat

[Richard10002]

The Smartguage manual says it can be up to 10% inaccurate when charging.

 

My Smartguage is not accurate when discharging if it shows more than about 80%, (if it were accurate at say, 90%, my 450Ah battery bank would be over 600Ah).

 

(I have both a Smartguage and a NASA BM2, so can see how many AH have been used when starting from 100% SOC)

[Geo]

Pop corn time

[WotEver]

(I have both a Smartguage and a NASA BM2, so can see how many AH have been used when starting from 100% SOC)

And what do you suppose that shows you?

[Richard10002]

And what do you suppose that shows you?

 

 

On Sundays I charge the batteries until amps drawn are less than 4, so less than 1% of capacity, so full - SG show 100%. I turn everything off, leave the boat, and return on Wednesday, so there have been 3 days of trickle charge from a 100W solar panel, the SG shows 100%, and I think it's safe to assume that the batteries are as full as they can be.

 

I zero the cumulative Ah reading on the NASA. Sometime later, or the following morning, the NASA shows that 60Ah have been used, and the Smartguage shows 90%.... if both are accurate, 60Ah = 10% of bank size thus bank size = 600Ah. My bank is 4 x Trojan T105s, so max bank size is 450Ah.

 

I agree that the NASA could be at fault, but from the point where the SG reads 80% down to the point where it reads around 40%, the readings seem to correlate to a bank capacity around 420Ah, which is both possible and reasonable.

 

QED??

[WotEver]

 

 

On Sundays I charge the batteries until amps drawn are less than 4, so less than 1% of capacity, so full - SG show 100%. I turn everything off, leave the boat, and return on Wednesday, so there have been 3 days of trickle charge from a 100W solar panel, the SG shows 100%, and I think it's safe to assume that the batteries are as full as they can be.

 

I zero the cumulative Ah reading on the NASA. Sometime later, or the following morning, the NASA shows that 60Ah have been used, and the Smartguage shows 90%.... if both are accurate, 60Ah = 10% of bank size thus bank size = 600Ah. My bank is 4 x Trojan T105s, so max bank size is 450Ah.

 

I agree that the NASA could be at fault, but from the point where the SG reads 80% down to the point where it reads around 40%, the readings seem to correlate to a bank capacity around 420Ah, which is both possible and reasonable.

 

QED??

Does the NASA show solar input? So if the solar is giving say 2A and you're drawing 3A does the NASA show 1A or 3A?

 

Obviously it depends on where the shunt is placed.

[Richard10002]

Does the NASA show solar input? So if the solar is giving say 2A and you're drawing 3A does the NASA show 1A or 3A?

 

Obviously it depends on where the shunt is placed.

 

The shunt is placed so there is only one wire to the battery negative. I'd assume that the NASA shows whatever the net effect at the battery negative is - presumably it has no idea where the Amps are coming from, or going to.

 

In fact, if everything is off, and there's a bit of sun, I see an input. If I turn a light on, the input falls.

 

I generally get to the boat after dark on a Wednesday, so the various observations I make are generally in the dark and not affected by solar input.

 

ETA: The above isnt quite true - The Smartguage is wired directly to the battery bank, but I think the effect is negligible.

Edited November 6, 2016 by Richard10002

[Murflynn]

I have 2 banks of 2 x 110AH, each connected to 2 x 100W 20V solar panels via Victron 75/15 mppt controllers, and monitored by digital ammeter/voltmeters.

 

one bank charges as I would expect, reaching a peak of about 14.6V when the controller goes into float mode.

 

the other bank regularly sits at 15.8v or even 16v in float mode.

 

any ideas what is going on?

 

.

Edited November 6, 2016 by Murflynn

[rusty69]

I have 2 banks of 2 x 110AH, each connected to 2 x 100W 20V solar panels via Victron 75/15 mppt controllers, and monitored by digital ammeter/voltmeters.

 

one bank charges as I would expect, reaching a peak of about 14.6V when the controller goes into float mode.

 

the other bank regularly sits at 15.8v or even 16v in float mode.

 

any ideas what is going on?

 

 

 

if the controllers are setup with the same parameters seems odd. The float voltage seems too high(assuming you have a 12v system).Worth checking the electrolyte level if you have been charging at a high level for a while.

Edited November 6, 2016 by rusty69

[Oldbugger]

I have 2 banks of 2 x 110AH, each connected to 2 x 100W 20V solar panels via Victron 75/15 mppt controllers, and monitored by digital ammeter/voltmeters.

 

one bank charges as I would expect, reaching a peak of about 14.6V when the controller goes into float mode.

 

the other bank regularly sits at 15.8v or even 16v in float mode.

 

any ideas what is going on?

 

.

 

Battery type settings? A 'custom' setting maybe?

[Top cat]

If its the same version of the 75/15 that I have ( 3yrs old) then there is no provision for setting the battery type or float voltages. I believe the later ones allow you to adjust things via your mobile phone so could have got corrupted ( taken over by Russian hackers) so if its a recent one check the settings. But not having one I can't give first hand experience of that possibility or how to adjust.

 

Top Cat

[Murflynn]

If its the same version of the 75/15 that I have ( 3yrs old) then there is no provision for setting the battery type or float voltages.

same - no provision for settings, except the jumper which is set to 'battery life' configuration in both cases.

if the controllers are setup with the same parameters seems odd. The float voltage seems too high(assuming you have a 12v system).Worth checking the electrolyte level if you have been charging at a high level for a while.

yeah, 12v system, and electrolyte levels are fine.

[Top cat]

Could you swap the controllers over and see if the problem follows the controller or stays with the battery.

 

Top Cat

[WotEver]

Sounds like a faulty controller to me assuming all the cabling is correct.