Marlec HRDi controller v MPPT

[lumphammer]

I have 2 x 80W panels wired in panel into a Marlec HRDi controller. In a bright sunny day I get about 7-8A from the panels.
In the real world would I be able to improve that by changing to a suitable MPPT controller?

 

[AntarcticPilot]

Nothing to contribute, but I too am feeding a 100w panel through an HRDi controller, and the performance seems to be less good than it should be. I'd be interested in hearing comments - woudl replacing the HRDi with a PWM controller be an improvement?

 

[RobF]

I have 2 x 80W panels wired in panel into a Marlec HRDi controller. In a bright sunny day I get about 7-8A from the panels.
In the real world would I be able to improve that by changing to a suitable MPPT controller?

Do you get 7-8A in a day or 7-8AH (in an hour). If you're consistently getting 7-8AH over an 8 hour period, this would seem pretty reasonable to me for a 160W panel. Clearly, the charge you're getting will be proportionate to the state of battery charge and the orientation of the panels.

 

[RobF]

Nothing to contribute, but I too am feeding a 100w panel through an HRDi controller, and the performance seems to be less good than it should be. I'd be interested in hearing comments - woudl replacing the HRDi with a PWM controller be an improvement?

If it helps by way of benchmark, I've got a Lensun 100W solar panel connected to a Victron 75/15 MPPT controller. I get about 5AH on a sunny day if my batteries need charging.

I suspect you've seen this whitepaper which provides quite a fairly technical comparison of MPPT vs PWM. I should note that the HRDi is a PWM controller and you are likely to see some improvement moving to a MPPT controller.

 

[VicS]

Do you get 7-8A in a day or 7-8AH (in an hour). If you're consistently getting 7-8AH over an 8 hour period, this would seem pretty reasonable to me for a 160W panel. Clearly, the charge you're getting will be proportionate to the state of battery charge and the orientation of the panels.

I think you have your amps and your amp-hours in a muddle. "Amp"s is an instantaneous measurement of current flow. "Amp-hours" is a measure of total quantity over a period of time.

Numerically Ah = A x h. 8 amps continuously for 7 hours would be 56 Ah

He says 7-8 amps in bright sun ........ not particularly good would have thought from a 160 watt installation ... somewhat less than expectation, even from a non-mppt controlle,r at least if the batteries where sufficiently discharged to accept more. He does not tell us their state of charge or their capacity


7-8 Ah over a an 8 hour period would be very poor, at least if the battery could take more .... it would only be an average of 1 amp, or slightly less but again the state of charge of the battery bank is a relevant unknown.

 

[RobF]

I think you have your amps and your amp-hours in a muddle. "Amp"s is an instantaneous measurement of current flow. "Amp-hours" is a measure of total quantity over a period of time.

Numerically Ah = A x h. 8 amps continuously for 7 hours would be 56 Ah

He says 7-8 amps in bright sun ........ not particularly good would have thought from a 160 watt installation ... somewhat less than expectation, even from a non-mppt controlle,r at least if the batteries where sufficiently discharged to accept more. He does not tell us their state of charge or their capacity


7-8 Ah over a an 8 hour period would be very poor, at least if the battery could take more .... it would only be an average of 1 amp, or slightly less but again the state of charge of the battery bank is a relevant unknown.

Not in a muddle, and apologies if my post was confusing. Am strongly agreeing that an average of 7-8AH over an 8 hour period would provide about 60A of charge into the batteries (assuming the batteries could 'receive' this charge). Hence my question to the OP - is he receiving 7-8AH or is he receiving 7-8A? If 7-8A then I strongly agree that this is much less than I would expect.

Assuming that it is a poor charge rate of 7-8A, there are a number of currently unknown factors could cause this. In no particular order,

• battery charge state
• battery load
• age of the panels
• type of panels
• orientation of the panels
• whether the panels have any shading or obstructions overhead which partially obscure them from receiving sunlight
• thickness of the wiring the OP has used to connect the panels to the controller

It might be helpful to get some insight on these to help the OP narrow down where his issue is. When I had an HRDi, I saw minimal Amps coming in (from a wind generator in a good breeze), but that was because my battery was already charged.

 

[VicS]

Not in a muddle, and apologies if my post was confusing. Am strongly agreeing that an average of 7-8AH over an 8 hour period would provide about 60A of charge into the batteries (assuming the batteries could 'receive' this charge). Hence my question to the OP - is he receiving 7-8AH or is he receiving 7-8A? If 7-8A then I strongly agree that this is much less than I would expect.

BUt you are in muddle!

7-8Ah over an 8 hour period is only an average of slightly less than 1 amp!

What you really mean is that 7-8 A continuously for an 8 hour period would provide about 60 Ah of charge

 

[noelex]

The difference between a good MPPT controller and a good non MPPT controller (often called a PWM controller) depends on a number of factors.

With nominal “12v” panels the extra yield from the MPPT controller is likely to be in the region of +5 to +15% as a ballpark figure. Colder climates are usually at the higher end.

 

[Richard10002]

I have 2 x 80W panels wired in panel into a Marlec HRDi controller. In a bright sunny day I get about 7-8A from the panels.
In the real world would I be able to improve that by changing to a suitable MPPT controller?

160w suggests a max of about 11.5A, so 7-8A seems quite good in the UK.

Others seem to think you mean 7-8Ah in a whole day, which is not so good... but that is not what you say in your post.

 

[RobF]

BUt you are in muddle!

7-8Ah over an 8 hour period is only an average of slightly less than 1 amp!

What you really mean is that 7-8 A continuously for an 8 hour period would provide about 60 Ah of charge

You're right, I am in a muddle Thx for bearing with me.

 

[lumphammer]

To avoid confusion what I mean by 7-8 amps from the solar panel is the typical current that the HRDi controller says is coming from the solar panel, not what is going into the battery. The two panels are mounted on a radar arch at the stern and one or other has usually got some slight shading from the aid aerial, radome or mast.
The original question is not about how my system is set up, but whether changing to an mppt controller is likely to give me more capability to charge my batteries and if so by how much.
The only answer so far seems to be between 5 to 15%.

 

[Cuan]

Thats my understanding of the readouts on my HRDi controller too. It shows the output of the charging source (PV or WG or net of both if you have both). I don't understand the technical differences between different types of controllers, but won't the output of the charging source remain the same?

 

[GHA]

To avoid confusion what I mean by 7-8 amps from the solar panel is the typical current that the HRDi controller says is coming from the solar panel, not what is going into the battery. The two panels are mounted on a radar arch at the stern and one or other has usually got some slight shading from the aid aerial, radome or mast.
The original question is not about how my system is set up, but whether changing to an mppt controller is likely to give me more capability to charge my batteries and if so by how much.
The only answer so far seems to be between 5 to 15%.

I'd be happy enough with 7/8A from 160W in the real world, I go by rule of thumb that top wack will be about watts/20 then add a fifth to the answer in A. So 100w/20 = 5, 5 + 5/5 = 6A. Or there abouts.

I'm on the hard with mains but unplugged at the moment, so with 2 x 100W panels hanging vertically, one away from low sun, 1 towards - figures are

Solar off -7A
Solar direct - 2.6A
Solar through MPPT - 1.6A

So no MPPT: + 4.4A
with MPPT: + 5.4A. Takes a moment to settle while it searches round for the best panel voltage

22% gain. With a victron 75/10.

 

[lw395]

I'd be happy enough with 7/8A from 160W in the real world, I go by rule of thumb that top wack will be about watts/20 then add a fifth to the answer in A. So 100w/20 = 5, 5 + 5/5 = 6A. Or there abouts.

I'm on the hard with mains but unplugged at the moment, so with 2 x 100W panels hanging vertically, one away from low sun, 1 towards - figures are

Solar off -7A
Solar direct - 2.6A
Solar through MPPT - 1.6A

So no MPPT: + 4.4A
with MPPT: + 5.4A. Takes a moment to settle while it searches round for the best panel voltage

22% gain. With a victron 75/10.

When you say 'direct' do you mean literally panels direct to batteries?
So the panel current = charge current?
If that's the case, then a good non MPPT converter would be expected to improve on that by something like a factor of 17/14 x about 95% i.e.the set panel voltage over the load voltage times the efficiency. 15% more current out than in perhaps.
An MPPT merely optimises this by tweaking the set panel voltage.

 

[Mistroma]

To avoid confusion what I mean by 7-8 amps from the solar panel is the typical current that the HRDi controller says is coming from the solar panel, not what is going into the battery. The two panels are mounted on a radar arch at the stern and one or other has usually got some slight shading from the aid aerial, radome or mast.
The original question is not about how my system is set up, but whether changing to an mppt controller is likely to give me more capability to charge my batteries and if so by how much.
The only answer so far seems to be between 5 to 15%.

5%-15% sounds in correct ballpark but I'd need to check my historical data.

I have 145W rigid panels under boom and using an HRDi for these plus 913 wind-gen. I also have 200W rigid panels on an arch using an Epever MPPT unit. I have daily input data for HRDi in Ah and MPPT in Wh. I can only estimate MPPT in Ah/day or HRDi in Wh/day. I also have combined data for Ah from all sources and can select days when solar & wind are only source. Wind is pretty small and also reported in Ah so should be easy to remove.

I'll try to dig out some figures when temp. in cabin gets out of 30s and into high 20s C.

I can also dig out age and spec. of each panel if you need it. However, output from original 145W panels hasn't changed much over time and 200W ones are pretty new.

It is worth knowing that default HRDi settings are rubbish for my T105s and I altered them years ago. I think original value was 2.4V/cell @ 25C and I have something like 2.65V. It's looks high but I've found that batteries just get to 14.8V and hold for a few hours (V drop & other factors combine to stop Voltage rising in normal use at anchor). MPPT setting are also tweaked to give good performance.

Standard settings for HRDi would pretty much stop charging above 85% SOC and current to batteries was very low. Current stays up fairly well now. Trojan suggest 2.45 - 2.79V as batteries rise to 100% charge and current 10-13% C20 rate dropping to 1-3% C20 rate. Even at 100% batteries get under 14A from solar when 100% so settings seem good for life at anchor. Of course, all change at end of season in a marina.

Your settings will be different but it is worth getting them to correct value for your batteries.


UPDATE: Data from this year, only including days when no shore power, engine or generator used (21 days since 6th June).

HRDi PWM
913 Windgen..............................…...6.2 Ah/day
1x65 + 2 x 40W all in parallel..48.4 Ah/day

Epever MPPT
2x100W in series...………………..77.1 Ah/day

So MPPT is producing 15.4% more than PWM. A large proportion will be due to lack of shading on arch vs. under boom. But output from HRDi has always been surprisingly good from 145W solar so shading is not as big a problem as you'd think for my setup (3 smaller panels, less shading impact.

My MPPT is certainly not more than 15% better than PWM unit and actually more likely to be much lower difference if all panels were similarly mounted.

I'll try to find some spot A readings when none of the panels were shaded. 5%-10% improvement seems a likely outcome.

N.B. Ah/day or Wh/day is much more useful than simply quoting Amps. The daily output allows for fact that Amps. vary a lot during the day and gives a better idea of how much charge batteries are likely to get. Of course my figures are for Aegean where even early and late output is quite high. I'd expect MPPT on unshaded panels in series to greatly outperform PWM in low light conditions. But that's when you aren't getting much output anyway (i.e. Double 0.5A is still only 1A and impact on total daily figure not huge).

 

[noelex]

If that's the case, then a good non MPPT converter would be expected to improve on that by something like a factor of 17/14 x about 95% i.e.the set panel voltage over the load voltage times the efficiency. 15% more current out than in perhaps.

Regulators that are not MPPT (often called PWM) cannot perform any voltage conversion, so the current from a non MPPT regulator cannot be more than the current produced when the panels are directly connected to the batteries.

In practice there are some (small) self consumption losses that means direct connection will give slighly more current than would be seen than when using a non MPPT regulator.

An MPPT regulator is different and can potentially (and usually in practice) extract more power than direct connection.

 

[lw395]

Regulators that are not MPPT (often called PWM) cannot perform any voltage conversion, so the current from a non MPPT regulator cannot be more than the current produced when the panels are directly connected to the batteries......

Sorry that is totally incorrect.
The world is full of DC-DC converters which convert a higher voltage to a lower one at a higher current, with a power efficiency of typically 90-something %.

 

[noelex]

Sorry that is totally incorrect.
The world is full of DC-DC converters which convert a higher voltage to a lower one at a higher current, with a power efficiency of typically 90-something %.

Yes, that is the basic difference between an MPPT controller, which has voltage conversion and a non MPPT controller (often called a PWM controller) which does not.

 

[GHA]

Just recorded some bluesolar at work, great fun!
A buck converter puller the panel voltage down to 14v so unlikely to help a huge amount.

 

[lw395]

Yes, that is the basic difference between an MPPT controller, which has voltage conversion and a non MPPT controller (often called a PWM controller) which does not.

No it is not.
MPPT stands for 'maximum power point tracking'.
This means adjusting the current drawn from a solar panel to keep it at the optimum point on its V/I characteristic in whatever level on sunlight is hitting it at the time.
That's an improvement on a simple DC-DC type converter which drags the panel down to a set voltage which is an estimate of Vpp.

It makes a big difference if you connect a few panels in series, when the panel voltage might be 30 or 40 volts.
I suggest reading the basics of voltage conversion on the Analog Devices or Linear Tech websites before trying to lecture someone who's designed this stuff for a living.