Newby experiment going wrong

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Re: Newby experiment going wrong

Postby Smurf1976 » Fri Nov 23, 2012 9:28 pm

I assume this 100Ah battery is an AGM battery?

Anyway, the panel voltage should be only slightly above the battery voltage unless the battery is fully charged. Assuming it's a fairly simple regulator, this means that if the battery voltage is 12.5 under charge, which is somewhere about right for the gear you have and starting with the battery at 12.0V, then the panel voltage will be only slightly higher - 13 or thereabouts.

Are you sure it's wired up properly? Any chance of a photo?
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Re: Newby experiment going wrong

Postby Tracker » Sat Nov 24, 2012 7:16 am

During the day, I measure 21V on the panel input,

Smurf, The situation seems to be that he is using a charge controller, and so the battery voltages could be anything.

That would seem to point to the CC if the battery is not being charged..

You had better put the panel back to the battery For a while and get some charge back into it and check out the CC..
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Re: Newby experiment going wrong

Postby melmik » Sun Jun 29, 2014 11:27 am

Hi, just reviving this as I have revived the old CMP 12/24 10A charge controller in a new project...and I'm having the same not so good results.

I bought a 85W Photowatt panel to charge a 12Ah 12V battery to run a small 12V pump. This is used to transfer water from a 2nd rainwater tank to our primary tank which connects to the toilet, and also to water the garden with more than gravity pressure.

Panel is connected to CMP regulator/controller, as is battery - connected in correct order (battery first). I've also used 6mm square wiring and appropriate fuses and connectors, so my skills have developed very slightly.

Using the unfortunately cheap multimeter, I get from 19.6 to 21Volts at the panel connections of the regulator.

The battery is fully charged and brand new, and runs the pump by itself very well.

But the panel doesn't charge the battery - same problem jde had in this topic. The battery just gradually drops voltage over a week to around 12.1 volts before I get nervous and recharge it. This is without any actual load/use being applied to it.

The controller lights up only 2 of the 3 battery charge status lights even when the battery is first connected fully charged. The load light stays on - which according to the manual means only that there is enough charge for a load to be applied. The charging light never lights up, even at 20 or 21 volts from the panel.

The voltage at the battery and load terminals of the controller are around 12.6volts once everything is connected, and the voltage at the battery terminals is 0.1V below this at all times.

Because I bought a cheap multimeter I cannot measure amps (it doesn't have a high enough range - yet another purchase I have to make).

My thoughts are:
1. The controller is faulty - which is highly possible considering I bought it from the Solar Energy Store online, which has been the subject of multiple Fair Trading warnings recently. Maybe jde and I bought from a faulty batch - or the same supplier.
Edit: here is some more info on the controller:
• Rated Voltage:DC12V/24V
• Max Current:10A
• Low Voltage Cut:10.5V/21V
• Temp compensation:-3mv/℃/cell
• Zero Load Loses:≤20mA
• Min Wire Size:≤20mA
• Min Wire Size:2.5mm^2
• Voltage Drop:<210mv
2: The controller is OK but its own internal power needs are so parasitic that it doesn't allow enough thru for the battery to be charged.
3: My 85W panel doesn't have the grunt - which seems unlikely as the panel puts out between 4 and 5 amps and I know I'm getting decent voltage through.

If anyone has any ideas I'd be grateful. The alternative is to buy a new controller - which I'm 99% convinced I need to do.

So next question is; what is a good brand of relatively inexpensive controller for a setup like this?
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Re: Newby experiment going wrong

Postby Gordon-Loomberah » Sun Jun 29, 2014 1:28 pm

EM sell a range of good quality controllers, such as these:

An 85W panel could damage your 12AH battery, since Lead-acid batteries don't like to be charged at much more than C/4 for flooded cells, and less than that for sealed batteries. I would assume that your battery is sealed, and a safe charging rate might be only 2A for it, and given that panel could output over 7A in some conditions, you could damage it pretty quickly if the reguator was working... although it sounds as though it is not. Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
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Re: Newby experiment going wrong

Postby melmik » Sun Jun 29, 2014 3:06 pm

Thanks again Gordon. Those Morningstar controllers look good.

The battery is a SLA and has initial current limit of 3.6A so yes, a 7A burst might harm it and even the typical 4.8Ah might be a bit much.

The specs for the panel give open circuit voltage maximum at 21.6 and with a short circuit current of 5.2A +/- 5% so I would need a controller rated above 6.5A (125% * 5.2) to handle the panel.

But your warning about the potential battery damage from an overcurrent incident worry me - it sounds like I have underdone the battery. I have a few spare old 7Ah ups batteries I could connect in parallel which would give me enough Ah to absorb the overcurrent? Plus extra capacity....but the need for a new enclosure. Oh well, more man cave activity next weekend.
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Re: Newby experiment going wrong

Postby melmik » Sat Jul 05, 2014 11:53 am

Turns out it was a faulty regulator. New Morningstar SHS-10 arrived a fee days ago, hooked it up and everything is working perfectly. Batteries are charging even in the shaded winter position I have the panel. Used the pump for 2 hours to transfer water and no problems. It is a small 12v Commercial Electric pressure pump from Bunnings. Uses 4.5A so I can easily get a few hours out of the 19Ah of batteries I have so far. Pump is slow but does the job....and easier on my back than the buckets used previously.

The Morningstar will cut me off if the batteries get too low, but as the panel is putting maybe 3 or 4 amps back in when I use it thru the day, it shouldn't be an issue.

To hopefully protect against the overcurrent damage Gordon mentioned, I have just changed the battery fuse down to 5A until I increase my battery bank.

I realise all this is probably expensive overkill for a simple water transfer, but I'm using it as a learning experience, plus the whole setup is easily useable for other purposes like garden lights. Plus it is fun.
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