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MPPT setup


blackrose

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8 minutes ago, blackrose said:

This is how I've got it set up:

 

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Boost is absorption. If there's anything I've got wrong please llet me know.

The data sheet I posted earlier suggested your batteries require an equalisation voltage of 16.2V

Worth checking it's the right one though 

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15 minutes ago, rusty69 said:

The data sheet I posted earlier suggested your batteries require an equalisation voltage of 16.2V

Worth checking it's the right one though 

Having thought about it a bit more, I guess there is good reason not to set an unattended equalisation charge, particularly if that voltage is being passed to the boat services 

Edited by rusty69
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15 minutes ago, rusty69 said:

The data sheet I posted earlier suggested your batteries require an equalisation voltage of 16.2V

Worth checking it's the right one though 

 

Ok thanks. But how often is the MPPT going to run an equalisation charge? I wouldn't want it going up to 16.2v too often.

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2 minutes ago, rusty69 said:

Agreed. See my last post. 

 

Ok thanks. So if it's going to do an absorption charge at 14.8v for 2 hours + an equalisation charge for another 2 hours could that be too much for the batteries?

 

I would normally do an equalisation charge at about 16v for half an hour once every couple of months from my bench 12v supply.

Edited by blackrose
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1 minute ago, blackrose said:

 

Ok thanks. So if it's going to do an absorption charge at 14.8v for 2 hours + an equalisation charge for another 2 hours could that be too much for the batteries?

You could always set equalisation duration to zero minutes and do it manually when required. 

Edited by rusty69
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16 minutes ago, rusty69 said:

You could always set equalisation duration to zero minutes and do it manually when required. 

 

Yes I'll do that. Thanks.

 

I'd set the equalisation charge at 16.2v for half an hour once a month if I could, but since it doesn't have any frequency parameter and I have no idea how often it's going to do it I think it's best not to have it at all. Imagine if it did an equalisation charge everyday - I don't think that's good for the batteries at all. 

Edited by blackrose
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25 minutes ago, blackrose said:

 

Yes I'll do that. Thanks.

 

I'd set the equalisation charge at 16.2v for half an hour once a month if I could, but since it doesn't have any frequency parameter and I have no idea how often it's going to do it I think it's best not to have it at all. Imagine if it did an equalisation charge everyday - I don't think that's good for the batteries at all. 

Yes, you are right. The MPPT manual will have the definitive answer on equalisation frequency. I doubt very much it is a daily occurrence, but probably wise to turn it off for the reason I have already given. 

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39 minutes ago, rusty69 said:

Yes, you are right. The MPPT manual will have the definitive answer on equalisation frequency. I doubt very much it is a daily occurrence, but probably wise to turn it off for the reason I have already given. 

 

All the manual gives under lead acid battery parameters is the equalisation charge voltage and duration ranges. There's nothing about frequency of charges. As I said, it's a crap manual.

Edited by blackrose
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Thanks. It seems safer not to have a MPPT running an equalisation charge especially if your don't know how often that will happen and might not be there. 

 

I'm away overnight and have left my new PSW inverter running the fridge instead of shore power. I wasn't sure if that was a good idea but I used to leave my mains battery charger on all the time and never had any problems over the last 17 years.

 

I'm sure there are lots of people who wouldn't leave their battery charger on while they're away from the boat but would be happy to leave a MPPT controller running through its charge cycles. I'm not sure what the difference is in terms of risk?

Edited by blackrose
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3 minutes ago, blackrose said:

I'm sure there are lots of people who wouldn't leave their battery charger on while they're away from the boat but would be happy to leave a MPPT controller charging the batteries. I'm not sure what the difference is in terms of risk?

When I had battery cell failure this year the MPPT only pumped power into the batteries when the sun was out.

A battery charger would have dumped 60amps into the batteries 24/7 so they would probably exploded  before I got back.

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The Epever XTRA controller on my setup has the equalisation set at 14.8v. I was at the boat about 4 hours after sun up (not that there was any here today) and the batteries were at 14.8v, so it appears this version of the controller does equalisation immediately after absorption at 14.6v. It was only pushing out 0.2A at that time. It completed the cycle shortly after I checked it and the voltage dropped back to a more normal level. I attempted to modify my controller parameters by using the USR setting but there only appears to be a common LEN option for both absorption and equalisation. I got frustrated with the interface and button pressing  and wasn't confident of the correct result given the poor documentation, so left it on FLD rather than USR. The batteries seem fine and there was no sign of gassing or loss of liquid. The way to avoid the equalisation appears to be to set absorption and equalisation voltages the same and the LEN parameter to half the desired E.g. 60 so it does 120mins absorption. I might try this yet, but like blackrose, it's early days with solar for me, so still getting used to power available per day and season.

 

I've only half the panels balckrose has and there wasn't much coming out of the panel today. With a fridge running, I'd probably have been in deficit, but it'll be sunny tomorrow no?

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1 hour ago, Loddon said:

When I had battery cell failure this year the MPPT only pumped power into the batteries when the sun was out.

A battery charger would have dumped 60amps into the batteries 24/7 so they would probably exploded  before I got back.

 

Why would the charger have done that? Wouldn't it just sit on float charge pumping 0.6A into the batteries? Or would it be higher because a cell has failed?

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45 minutes ago, Psychalist said:

The Epever XTRA controller on my setup has the equalisation set at 14.8v. I was at the boat about 4 hours after sun up (not that there was any here today) and the batteries were at 14.8v, so it appears this version of the controller does equalisation immediately after absorption at 14.6v. 

 

Interesting. If it's doing an equalisation charge everyday that would explain why mine was sitting at 14.8v for 4 hours. No wonder Epever set the default equalisation charge to a relatively low voltage. Imagine if it did a 16.2v equalisation charge everyday!

 

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11 minutes ago, blackrose said:

 

Why would the charger have done that? Wouldn't it just sit on float charge pumping 0.6A into the batteries? Or would it be higher because a cell has failed?

Battery with a shorted cell will sit at just over 10v draining the others, charger sees low voltage and goes into bulk charge and just keeps going as the voltage never gets high enough to get to the next stage. Most modern chargers have a limit on bulk charge time but often its not been set.

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42 minutes ago, Loddon said:

Battery with a shorted cell will sit at just over 10v draining the others, charger sees low voltage and goes into bulk charge and just keeps going as the voltage never gets high enough to get to the next stage. Most modern chargers have a limit on bulk charge time but often its not been set.

 

I see. So a MPPT wouldn't do that?

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10 minutes ago, blackrose said:

 

I see. So a MPPT wouldn't do that?

Yes it can but the high voltage bit is limited to 2hrs plus the battery gets to rest when the sun goes in so cools down overnight which with a charger it wouldn't.  My batteries were dropping to below 70%  overnight with nothing on apart from the comms devices that's how far the duff one was pulling them down. Whereas in normal use with everything on it goes down to 88%. 

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One other question I have. 

 

I bought a remote battery temp sensor for the MPPT. Apparently you're supposed to lay the thermocouple on top of the batteries but that seemed a bit naff to me so I put a bit of thermally conductive compound on it, slid a ring terminal over it, secured it with a bit of aluminium tape and attached it to one of my negative battery terminals and the other end to the remote temp sensor socket on the MPPT.

 

The problem is my MT50 display for the MPPT is showing some 27C but when I check the temperature on the top of the battery with an IR thermometer it's about 16C. 

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Strange. My MPPT came with a sensor srewed into the green connector. I wasn't expecting that and was anticipating ordering one if it was going to be useful. I soldered the litlle sensor (looking like this) to a data cable and ran it the 2-3 metres to the batteries and left it between two of them. It seems to indicate quite accurately the ambient temperature (I haven't had the batteries warmer than that).

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4 hours ago, blackrose said:

One other question I have. 

 

I bought a remote battery temp sensor for the MPPT. Apparently you're supposed to lay the thermocouple on top of the batteries but that seemed a bit naff to me so I put a bit of thermally conductive compound on it, slid a ring terminal over it, secured it with a bit of aluminium tape and attached it to one of my negative battery terminals and the other end to the remote temp sensor socket on the MPPT.

 

The problem is my MT50 display for the MPPT is showing some 27C but when I check the temperature on the top of the battery with an IR thermometer it's about 16C. 

Remove it from the negative post and see if this makes a difference. It works by creating a small voltage for the controller to read and if the case is not isolated you may have created a ground loop affecting the voltage, hence affecting the measured temperature. My Victron one is bolted to the negative terminal but the case on that is definitely isolated.

Edited by PeterF
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5 hours ago, blackrose said:

The problem is my MT50 display for the MPPT is showing some 27C but when I check the temperature on the top of the battery with an IR thermometer it's about 16C. 

Just noticed in my manual that if the sensor is  broken ir shorted the temperature will revert to default.

Do you get a different reading with the sensor connected/disconnected ?

   

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2 hours ago, PeterF said:

Remove it from the negative post and see if this makes a difference. It works by creating a small voltage for the controller to read and if the case is not isolated you may have created a ground loop affecting the voltage, hence affecting the measured temperature. My Victron one is bolted to the negative terminal but the case on that is definitely isolated.

 

Ok I'll try that, thanks.

 

1 hour ago, Loddon said:

Just noticed in my manual that if the sensor is  broken ir shorted the temperature will revert to default.

Do you get a different reading with the sensor connected/disconnected ?

   

 

Just disconnected it at the MPPT and it hasn't changed. It was showing 16.6C before I disconnected it and it's still showing the same temperature. 

 

The MPPT came with a local temp sensor, a small green block plugged into the same socket, which I removed and plugged in the remote sensor.

Edited by blackrose
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