Outback MPPT output voltage waveform

Dapdan · March 2009

Hey all,

Can anyone out there confirm if the output voltage wave form the of the outback mppt is continous as opposed to say PWM. I have some GNB agm i am trying to charge with a C60 and the rest voltage is not at the full charge rest voltage as indicated by the OEM. I read some where that PWM charging is not ideal for these telecom cells and it should be a continous voltage form to charge them. I am just looking into this aspect to see if this could be the reason why i cant get them to their fully charged rest voltage. Maybe this is a question better suited for boB?

Damani

Solar Guppy · March 2009

Re: Outback MPPT output voltage waveform

In Bulk charge, PWM is the array directly connected to the Batterys 100% On, Mppt is a Step down both output fairly constant Voltage, limited to available current

In Absorb or Float, PWM is On/Off ~400 times a second, Mppt is constant voltage, either will charge battery fine

You are being unrealistic to think used sub battery's will live upto new specs, battery's decline in performance with age and use, nothing can prevent this and your reported rest values are quite good considering they are used

Windsun · March 2009

Re: Outback MPPT output voltage waveform

Some of those telephone batteries have a lower specific gravity acid in them, so they will never charge as high as a standard one will.

Or they may be sulfated, or just old.

Dapdan · March 2009

Re: Outback MPPT output voltage waveform

Thank you guppy & wind sun,

the actual situation is that the max rest voltage is 2.10vpc and OEM document states that it should be 2.15vpc. I am aware of the age factor but these cells apparently have never been installed, but they did sit for some years unused so i am not sure if they self discharged and then sulphated. I am trying with them to see if i can get anything out of them since i got them for free. Dont get me wrong they are holding voltage. I tried to fully charge them discharge through a Kill a meter to record kwh hence Amph and got 12kwh (500amph) and then charged them again adn the CC indate appro 500amph of charge. This is my first cycle adn i will keep at it to see how it goes. so they still have some life in them.

Damani

mike95490 · March 2009

Re: Outback MPPT output voltage waveform

Depending on how you control the discharge, you can ruin them yourself. Limit the discharge to 50% of capacity, or the 50% discharge voltage, whichever you reach first. Otherwise, you can actually reverse charge a weak cell.

And how accurate is the METER you are checking the voltage with ? maybe it's a out of calib meter. When was it last calibrated - before you worry too much about .05V

I think voltage is a function of chemistery, so much % acid, so much volts @ 70F. Once you start the discharge, all bets are off.

BB. · March 2009

Re: Outback MPPT output voltage waveform

It does say "Max Rest Voltage"? So less would be OK too--how much less is a question.

With Telecom batteries--do you have the manual?

-Bill

Dapdan · March 2009

Re: Outback MPPT output voltage waveform

I did download the original manual from GNB and have read it thoroughly.

In respect of the DVM i can not swear on it's accuracy but i would have to say it is the same DVM i use when to set my voltage points accurately on my C60 and C40 for the set point when i am charging my FLA and they have been peforming good for the past 6 months (they also used traction cells 640Ah each)

when i cycle my batteries they are not discharge beyond 20% since my capacity is high and i can drive up to 350ah on average and use on average 250Ah at night. Generally by 2pm my batteries are in float. In respect to discharge it is an average of about 250w (appro 10A pc max 25A pc) so my cells arent discharged at a fast rate.

Damani

BB. · March 2009

Re: Outback MPPT output voltage waveform

Damani,

It may be worth checking the calibration on your DVM... They are usually pretty good--but it is sometimes very difficult to tell when one is working correctly or not.

-Bill

Bob McGovern · March 2009

Re: Outback MPPT output voltage waveform

What's the total Ah of your bank? If you keep it in the top 20%, they should last a very long time, & I wouldn't fret at all over a tiny discrepency in rest voltage.

Good score!

Dapdan · March 2009

Re: Outback MPPT output voltage waveform

yes bob it is a pretty good score.

the FLA are hawker and they are suppose to be 640Ah cells (24#) so that give me 1280Ah for my 24v system got them for $35 each 3 yr old from a submarine comp.

The GNB agms are 900Ah and got them for free from a telecom comp and i have 12# of them. it is these one i am trying with to get max. life out of them. These deals dont come often and i am always looking out for them. those one i was waiting for about 6months to get them.

i realise you have a bergey. how does it perform and how long did you have it. i am considering getting one. That is a pretty large battery bank you have there by the way- i am jealous

How do you recommend i calibrate the DVM Bill?

Damani

BB. · March 2009

Re: Outback MPPT output voltage waveform

When I used to work in the industry--The company would calibrate our own meters along with those at work (for free 8)).

Other than finding a local calibration lab and getting a quote--If you can find somebody else with a "new or calibrate" meter and have them measure your "critical items" (such as your bank voltage)...

The problem is that a "bad meter" can be very difficult to detect... We had one person here that ended up with weird results when measuring current and voltage with a damaged meter... 1 amp measured OK, 4 amps measured 1.78 amps (or something like that)... So when adding and subtracting loads/panels (trying to find an electrical problem)--the meter errors where repeatable--but did not make sense.

Sorry, I don't have any good way of doing it at home on the cheap...

Maybe one of the "HAMs" here has some good ideas or contacts.

-Bill

Bob McGovern · March 2009

Re: Outback MPPT output voltage waveform

Dapdan wrote: »

i realise you have a bergey. how does it perform and how long did you have it. i am considering getting one.

See this thread, with incriminating photos.:;)

Do you plan to run two separate battery banks, then -- Hawkers as one bank, GNBs as reserve? Or are the Hawkers not performing?

niel · March 2009

Re: Outback MPPT output voltage waveform

"Maybe one of the "HAMs" here has some good ideas or contacts."

well if it's meter accuracy you want to compare or find out, you can ask your local electric company if they can check it or at least compare the readings with his dvm. you could ask an electrician too, but they may want to charge you big for their valuable time.
of course this is in addition to the obvious answer of buying a high precision meter for big bucks.

Dapdan · March 2009

Re: Outback MPPT output voltage waveform

Bob i plan to run the two banks separately. since i depend on used batteries for storage i have to be always looking out for them so that i get an overlap and dont end up with all my storage gone. The hawkers have been working very well.

It seems that it would be easier just buy another DVM rather than trying to calibrage on:roll:

Thank all of you guys for the info, i am eternally grateful. If any of you guys find yourself in Barbados, you are most welcomed to be my guess. I wouldnt mind putting any of you guys up-cheers.:D

Damani

Outback MPPT output voltage waveform

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