Fridges (yet again!) and Solar Controller

oldtrack123 · Guru

Fridges (yet again!) and Solar Controller

brian · Guru

Wirroff wrote:
Just as another aside folks, we have just looked at the PL20 again now (5:15pm with sun low in the sky) and the BATV is showing 11.6v and the CHRG is showing 0.2A. The fridge has now switched itself off again. I don't think there is enough in the batteries to run the fridge and I suspect that the batteries may be damaged. At a friends house, we had the charger on the batteries whilst on 240v from his house, for seven days and some folk suggested we may have 'over-charged' them and damaged them. Could this be the case also?

What Ah in and out readings does the PL20 now tell you?

There are a number of possibilities for your problems here, so keep the info coming.

Edit:-

I seriously doubt that you have damaged the batteries by overcharging them. Flooded batteries are very forgiving of this crime, and provided the water was kept over the top of the plates, then they would not have "cooked". I agree with others that you don't have enough of either solar or battery capacity to successfully run this fridge long term.

-- Edited by brian on Sunday 10th of November 2013 06:37:49 PM

Wirroff · Senior Member

So, here we are, a brand new Waeco HDC 190 fridge/freezer fitted, $2000 lighter and it lasted on 12v all of......wait for it.........2 days! We got up today (Sunday morning) after having it fitted on Friday and the fridge and freezer weren't working! I fired up our internal generator (petrol 2Kva) and it came on straight away. Having previously recently checked the state of our batteries (2 x 110 a/h house batteries) I'm now very confused!

According to the bloke we bought the rig off, the batteries are only 12 months old and viewing the voltmeter and testing the hydrometer, all looked good. We have two solar panels on the roof of the rig (not sure what size they are) and these are, I presume, charging the batteries also. I looked at the Solar Controller under the seat (Plasmatronics PL20) and, having read an online manual, pushed the yellow button and came up with these statistics (nothing else was 'on' at the time apart from the fridge freezer)....

1) DATA

2) SET

3) 11.9v BATV

4) 9.5A CHRG

5) 6.4A LOAD

6) 20 ah IN

7) 5 ah OUT

Can anybody help us out? We really don't know what any of this means and what it SHOULD be saying on these read-outs (i.e. Is something wrong with our system?). As we have mentioned previously, we are VERY new to being Nomads and don't understand electrics at all. Carton of beer for any assistance and extra points will be awarded for Plain English answers as we're not very bright (I'm sure there's a pun there - bright/electrics?).... biggrin

grae and deb · Senior Member

ok will try to help a bit at a time ,probally need to know first what sort of fridge ie 3 way or compressor , if it is 3 way it will run your batteries down really quick , by your readings your batt,s are down to around 75 to 80 % you have got a reasonable charge going in from solar so that should help , id say get a charger going on your batteries and get them back to 14.2 and go form there , first things first ,lets see what type your fridge is
cheers grae

KFT · Guru

I would check to see if the solar controller is set to the correct battery type or the charge voltage will not be enough.

solar controller needs to be set to AGM(14.2v charge) if AGM are the type of battery you have.

frank

Rover · Veteran Member

Voltage drop.

To check use a voltmeter, voltage at the battery then at the fridge

if at the battery its 11.9v with the fridge cycling and 11.3v at the fridge

when cycling you are getting a .6v drop in voltage, the fridge will stop.

If that is the case run bigger wire say minimum 8mm2 (square) should fix the problem.

moblet · Senior Member

OK, so it's a compressor fridge designed to run on solar-charged batteries, not a 3-way designed to run on gas while parked. So that issue is eliminated.

One feature of this (and many) 12V fridges is battery undervoltage protection (called battery monitor in the manual for my Waeco, which has three voltage settings, 10.4, 11.4, and 12.0). Look this up in your fridge's owner's manual and make sure it is set to the lowest setting. If it is currently set at 12V or similar then this could explain what's going wrong - when the compressor runs the voltage drops below the threshold and the protection feature then stops the fridge. The fridge then won't restart until the battery voltage is much higher than the threshold. If the wires are too light as suggested by Rover then the battery protection will trigger even when the batteries aren't this low, because the voltage reaching the fridge will be lower than at the battery.

For ongoing use it'll be helpful for you to know the capacity of your solar panels, i.e. can they realistically keep up with your fridge or will you be running the generator every few days to top up the batteries. Three ways to find out their capacity:

1. It's printed on the back of each panel

2. If you can measure them we could guess at their output from their area

3. See how many amps are going through the controller in full sunshine

If you park in the shade then you're not going to get anywhere near what the panels are capable of, and would need a lot of excess solar capacity to keep up with the fridge. 120W (~6.75A in full sun) would be the bare minimum to keep pace with that fridge, if the panels weren't placed in the shade.

Wirroff · Senior Member

It's a two-way fridge (240/12) and we have 2 x 110a/h house batteries (not sure what AGM means but we do have to check the levels, use demineralised water and have a hydrometer to do that??). The solar panels measure appox 1200mm x 600mm and there are two of them. The only reference in the fridge manual I can see to voltage is an 'switch on' voltage of 11.7 and a switch off voltage of 10.4v. I have looked at the back of the fridge and can only see wires and the compressor, no other switches.
My wife thought that the batteries themselves may be 'cooked' and are not holding enough charge over-night to run the fridge? We are operating on 12v right now (4pm and it's been sunny all day) and the fridge is OK but it was 5am in the morning when we realised it wasn't running. Could it be the batteries themselves? How much are replacement batteries? How can we tell if this IS the problem. Once again, thanks for all your help folks and I'm sorry we have so many questions. BTW, the fridge manual states that it is 75W so a draw of 6.4a sounds about right doesn't it?

oldtrack123 · Guru

moblet wrote:
OK, so it's a compressor fridge designed to run on solar-charged batteries, not a 3-way designed to run on gas while parked. So that issue is eliminated.
snip------l and make sure it is set to the lowest setting. If it is currently set at 12V or similar then this could explain what's going wrong - when the compressor runs the voltage drops below the threshold and the protection feature then stops the fridge.

Hi

I would certainly set it to the lowst setting to test if the fridge is OK BUT I CERTAINLT would not leave it there!!

Battery life could end up being very short

Much better to use the 12v setting as standard

& IF voltage drop is a problem get heavier CABLES

The inbuit low voltage cutout has little to do with protecting the batterries from over discharge

IT'S PRIME purpose is to protect the fridge itself !

PeterQ

brian · Guru

A couple of points that I will make here which contradict some of the other replies.

1. If the PL20 is showing 11.9v, then your battery state of charge is at 35% not 75 to 80%.

2. You should not set your fridge low voltage cutout to any lower than 11.75v as the batteries are just about flat at that voltage, and taking it lower will severely shorten the batteries' longevity.

3. You can download and print a user manual for the PL20 from the Plasmatronics website, and I suggest that you do so as it will help you understand what is arguably the best PWM controller on the market.

About those PL20 indications using your item numbers.

1. Data:- In this screen, a long press on the yellow button will reveal all sorts of information about what has been happening with your batteries and charging system for the last 30 days. Read the manual for how to access all of the info. One thing that you should do in this screen, (only when your batteries are definitely fully charged), is short push through to the SOC screen and then long push to reset it to 100%. Also don't leave the solar volts screen showing as in this mode the panels are disconnected from the batteries and no charge is going to them (it will reset eventually, but don't leave it there).

2. Set:- A long push on the button will give you access to the setup menu.

The first item will be "Time", it's in 24hr format, set that to the time of day, being aware that the hours are in decimal sections, so 13.5 is 1:30pm. A long push will start the display flashing so that you can change the time by using short pushes, then lock it with a long push, then a short push for the next item. The correct time is important for the PL20 to keep accurate records of your daily usage patterns, and for the event timer if you wish to use that feature. If you ever disconnect the battery, the time will have to be reset.

The next item is "System volts", which in your case should be 12. set as above if required. Then short push the button for the next item

The next item is "Program", which in your case should be Prog 0. set as above if required. Then short push the button for the next item. Program 0 has an inbuilt low voltage disconnect which is superior in operation to the fridge ones as it has a decent inbuilt hysteresis to allow for motor starting voltage drop.

The next item is "Battery capacity" which should be 220, If it's not, set as above if required. Then short push the button for the next item. This setting is important for the PL20 to keep accurate record of your battery state of charge.

The next items are not important to you, so short push until you reach "set" and then long push to exit the setup menu.

3. Batv:- This is showing the actual terminal voltage of your batteries. A rested battery (under neither charge or discharge for at least 8 hours) should show 12.8v if fully charged, and progressively lower voltages at various lower stages of charge. The reading will drop if there is a load, and will increase when the battery is being charged. When the batteries are being charged by either solar or other means, you should see an indication of anywhere from 13.5 to 14.6v. This is not an indication of the state of charge of the battery, it's an instantaneous battery voltage reading. A long push on this screen will show you what charge mode (boost-absorb-float-equalise) that the PL20 is currently working in, the screen will self reset to Batv.

4. Chg:- this is the total charge that is going to your battery via the PL20, (there may be other charge avenues (such as a mains charger directly connected to the battery) that is not recorded here. If you have an unrecorded figure, your daily record and state of charge readings will be inaccurate.

5. Load:- This is the load that is being supplied via the load terminal on the PL20. (there may be other load avenues (such as an inverter directly connected to the battery) that is not recorded here. If you have an unrecorded figure, your daily record and state of charge readings will be inaccurate.

6. Ah in:- Is today's total received charge as recorded by the PL20. This is only as accurate as the way the device wiring is set up, and can only record the charge that goes through the PL20.

7. Ah out:- Is today's total drain as recorded by the PL20 and has the same limitations as for 6 above.

From the charge that you are showing, I would suspect that you have a couple of 100 to 130 watt panels on the roof.

I would also suspect from the voltages showing that your batteries are in poor condition as the voltage should be showing higher with the excess of instantaneous charge over discharge and Ah in to Ah out on your display.

You say you tested the Hydrometer, so I assume the batteries are flooded type, what were the SG readings, were they taken before - during - or after charging?

Wirroff · Senior Member

Hi Brian, thanks for your detailed reply. The Hydrometer testing was done after they'd been on charge. Just as an aside, the 11.9v BATV which showed, was 12.3v 5 minutes earlier! This was in full sunlight. I will make sure all the settings on the PL20 are as you suggest, but my gut feeling is that the batteries are not holding charge as the fridge goes in daylight but stopped in darkness.

Wirroff · Senior Member

Just as another aside folks, we have just looked at the PL20 again now (5:15pm with sun low in the sky) and the BATV is showing 11.6v and the CHRG is showing 0.2A. The fridge has now switched itself off again. I don't think there is enough in the batteries to run the fridge and I suspect that the batteries may be damaged. At a friends house, we had the charger on the batteries whilst on 240v from his house, for seven days and some folk suggested we may have 'over-charged' them and damaged them. Could this be the case also?

moblet · Senior Member

You have the entire GN brains trust on the case now

You can safely assume that your existing panels will not keep up with the fridge on its own, let alone anything else you switch on. Therefore, with your existing setup you will need to monitor your battery voltage and top up with the generator when it's getting too low. Check them first thing in the morning and at sunset at the very least, and record them. You will have to learn what voltage they need at sunset in order to keep the fridge going overnight.

Most rigs these days are equipped with deep cycle AGM batteries, which don't require maintenance and won't leak if tipped over. I'm wondering if your batteries are genuinely deep cycle, i.e. designed for what you're using them for. Can you give us any information about them? Is there any brand and model information on them that you can see?

If your batteries were fully charged when you installed the fridge, then to have them down below 50% within 36 hours, with some solar input, suggests to me that they aren't in tip-top shape. At worst the fridge would have drawn 100Ah in that time unless it was in the sun or you left the door open.

In the medium term, unless you're happy with the above arrangement, you'll need to think about increasing your solar capacity and possibly your battery capacity too, especially if you are drawing much power with other appliances.

moblet · Senior Member

Wirroff wrote:
At a friends house, we had the charger on the batteries whilst on 240v from his house, for seven days and some folk suggested we may have 'over-charged' them and damaged them. Could this be the case also?

Are you using a battery charger that switches to "float" charging once the batteries are fully charged (i.e. just about any modern charger), or one that just keeps pumping in power regardless? Again, if you're not sure, tell us the brand and model of your charger.

brian · Guru

Wirroff wrote:
It's a two-way fridge (240/12) and we have 2 x 110a/h house batteries (not sure what AGM means but we do have to check the levels, use demineralised water and have a hydrometer to do that??). The solar panels measure appox 1200mm x 600mm and there are two of them. The only reference in the fridge manual I can see to voltage is an 'switch on' voltage of 11.7 and a switch off voltage of 10.4v. I have looked at the back of the fridge and can only see wires and the compressor, no other switches.
My wife thought that the batteries themselves may be 'cooked' and are not holding enough charge over-night to run the fridge? We are operating on 12v right now (4pm and it's been sunny all day) and the fridge is OK but it was 5am in the morning when we realised it wasn't running. Could it be the batteries themselves? How much are replacement batteries? How can we tell if this IS the problem. Once again, thanks for all your help folks and I'm sorry we have so many questions. BTW, the fridge manual states that it is 75W so a draw of 6.4a sounds about right doesn't it?

I have to assume that the readings that you took from the PL20 weren't done at 5 am otherwise you would have had no charge figures, unless that charge was coming from the generator, and the fact that you are posting here and obviously still alive which you wouldn't be if you started a genny near me at that time of the morning. blankstare

If you were able to use a Hydrometer and need to water the batteries, then they are flooded type not AGM.

The measurements of the panels don't tell us a lot, but the incoming 9.5 amp charge (if it was from just the solar) indicates that they total at least 200 watt and possibly a bit more.

You haven't provided the specific gravity (SG) readings that you took, so it's not possible to give an opinion of battery Soc, but that still will not indicate true battery capacity remaining. When testing for SG you should always take the readings before adding water. If you do need to add water, provided the top of the plates are covered, add the water after charging.

Don't worry about the fridge cut off voltage as the PL20 will protect the batteries from over discharge which is probably what happened overnight.

220Ah of batteries should very comfortably run your fridge overnight if they are reasonably up to charge when you go to bed.

To test the batteries' true capacity, you need to make sure they are fully charged and then put a known load on them for a set time and take note of voltage depression over that time. The load and time need to be large enough to get a good sample. Otherwise, you could get them load tested at a battery dealers, but don't let them hit them too hard for too long as deep cycle batteries don't appreciate this.

brian · Guru

Wirroff wrote:
Another quick question; if we go and get some brand new AGM batteries and we currently have 'flooded' batteries, where and how do I change the 'battery type' on the PL20 as someone has suggested I need to do?
One thing I will say; the quick responses on here and the advice and help that has already been given is outstanding. This is the BEST forum I have ever become a member of and I would like to thank you all....

PS What should we be paying for decent AGM batteries?

You will need to change to program 1 for AGM batteries.

This still gives you low voltage cut out but removes the equalisation cycle from the charge regime.

To effect the change, short push the button through to "set, then long push to enter the setup section, then short push through to "Prog", then long push to start the current program number flashing, then short push to change the program, then long push to set it.

Download and print that manual soon.

120 ah AGM batteries will cost you around $300+ each.

-- Edited by brian on Monday 11th of November 2013 08:46:40 AM

Wirroff · Senior Member

The information on the front of the charger is; 12v-10amp RMS Charger 10 BC10 Arlec if that helps.....?

Wirroff · Senior Member

At 5:15pm, the a/h in was 58 and the a/h out was 44 if that helps?

Wirroff · Senior Member

Another quick question; if we go and get some brand new AGM batteries and we currently have 'flooded' batteries, where and how do I change the 'battery type' on the PL20 as someone has suggested I need to do?

One thing I will say; the quick responses on here and the advice and help that has already been given is outstanding. This is the BEST forum I have ever become a member of and I would like to thank you all....

PS What should we be paying for decent AGM batteries? confuse

brian · Guru

Wirroff wrote:
At 5:15pm, the a/h in was 58 and the a/h out was 44 if that helps?

It tells us that you got more charge in than you used (at least as far as the PL20 could know). any circuits that are not supplied via the PL20s load terminal will not be counted.

It also tells us that your solar panels are working fine.

The nett total charge that your battery received was just 14Ah, which is most likely less than you would then consume between dusk and dawn, so your batteries will continue to struggle.

The fridge can be expected to use upwards of 60Ah per day in warm weather and even more when it's hot.

If, as I suspect, you have a couple of 125w panels on the roof, you can expect around 70 ah input on a good day.

That leaves very little for lights, water pump, telly, etc.

That Arlec charger is what is known as a dumb charger. It has no specific charging regime and will only react to battery terminal voltage to control its output. It is only 6 amps maximum which is too low to be effective.

You still haven't shown any SG readings, so we still don't know the real state of your batteries' charge but we have a fair idea that its not good.

First thing to do would be to get yourself a decent intelligent charger, something like the Projecta IC3500 or an equivalent ctek unit.

The advantage of the 35 amp charger is that it has the capacity to charge a larger battery bank when you do add another battery, but can still charge a small one quite happily.

You will need to increase your battery and solar setup if you wish to be self sufficient with little generator use when bush camped.

Wirroff · Senior Member

Hi Brian, the current batteries are in fact 2 x 100a/h flooded (and not 110a/h as I first thought). Not sure how to read the SG, but the hydrometer shows me that they are in the green??? If I changed the batteries for new 110a/h or 120a/h AGM batteries, would this help? I understand that we would need to run a charger or generator every now and again, but for how long could we 'free camp'?

You have been a wonderful help so far and we appreciate your answers very much

Paul & Val

Wirroff · Senior Member

Brian, you're a star! We'll go shopping and get 2 x 120a/h AGM's and possibly a 35amp charger if money allows...........

Wirroff · Senior Member

Brian, you mention a Projector 35amp charger. We've seen a Calibre 20amp charger in Super Cheap for $190, would that be any good? (certainly better than our 6amp charger I'm sure you'll agree!)

brian · Guru

Wirroff wrote:
Brian, you're a star! We'll go shopping and get 2 x 120a/h AGM's and possibly a 35amp charger if money allows...........

Don't forget that carton of beer wink biggrin

moblet · Senior Member

Wirroff wrote:
Brian, you're a star!

I would have to agree with that assessment :)

Wirroff wrote:
We'll go shopping and get 2 x 120a/h AGM's and possibly a 35amp charger if money allows...........

I'm a little concerned that you might spend a fortune on new batteries that end up dead in quick time because your system is mismatched and/or you don't have your battery management regime all figured out. I'm not sure that 220Ah of even perfectly functioning batteries is enough for your load, especially as we've established that your existing solar panels can't sustain your load and that it looks like you'll be reliant on running the generator every day or two. For example, it might be cheaper in the long run to buy more battery capacity which lasts longer because it doesn't get drawn down as much. It might be worth doing an assessment of your total load and intended travel habits and then working out what power system is required to sustain it, either by consulting a dealer who knows their stuff or starting a new thread here, or both. Your controller records your total input and load each day, which will take a lot of guesswork out of this process.

If and when you do replace those batteries, they have scrap value that you could try to maximise if money is tight.

brian · Guru

Wirroff wrote:
Brian, you mention a Projecta 35amp charger. We've seen a Calibre 20amp charger in Super Cheap for $190, would that be any good? (certainly better than our 6amp charger I'm sure you'll agree!)

That charger has a 2 year warranty, which is about normal. It doesn't have the same facilities as the Projecta, but is considerably cheaper and they do get good reviews.

Supercheap is a very reliable company who will honour any substantiated warranty claims.

It is a bit on the small side for your requirements, but yes, certainly better than what you now possess.

Hopefully, with a bit more solar capacity, you won't use it too often.

moblet · Senior Member

brian will probably know the answer to this (I've never used a generator/charger setup), but would a 35 amp charger better utilise the generator and result in 40% less generator running time than the 20 amp one?

brian · Guru

moblet wrote:
brian will probably know the answer to this (I've never used a generator/charger setup), but would a 35 amp charger better utilise the generator and result in 40% less generator running time than the 20 amp one?

Not necessarily. It depends on the size and the state of charge of the battery bank.

A 35amp intelligent charger (note that I refrain from saying smart charger, because they can be confused with very different chargers used to charge smart batteries), will, even if set on the 35 amp range, only output a current that is suitable for the observed requirements of the battery.

So, it is possible that a 20 amp charger connected to a battery that can only accept say 15 amps of charge will take no longer to reach float than will the same battery connected to the 35 amp charger, however, for a situation where the larger current can be accepted, then the bigger charger will do the job more rapidly, but the generator will also be working harder to do so.

For example, a 35 amp charger running flat out on boost/bulk will consume around 1100 watts, whereas a 20 amp charger running flat out will be closer to 700 watts.

Wirroff · Senior Member

OK. So, thanks you to you kind knowledgeable folk on here, we are starting to understand motorhome electrics. I have a couple more questions if you would be so kind.....

Lets assume we have 2 x 80w solar panels on the roof. Total = 160w. I have read on this forum (and others) that a good 'rule of thumb' to ascertain the daily amps that could be expected out of your solar panels is to use the equation 0.33 x Total Wattage (0.33 x 160w) = 52.8amps. This is based on average daylight hours etc. This is actually borne out by my solar controller (PL20) which stated that 55 amp hours were put in, so pretty accurate.
OK, I know that when I looked at the Solar Controller and everything else was switched off, the fridge freezer (Waeco 141 Litre) had a load of 6.3a. The only reference to power etc in the fridge manual I can find, is that is it a 75 watt fridge. Using my high school electrics knowledge (Power (Watts) is equal to Amps x Volts), I get 75 watts is equal to 6.25a x 12 volts, so again, pretty accurate. This also shows that there is no voltage drop between the fridge and the battery as this is what I expected the voltage to be at the battery.
The question I have is this; If, at the time I measured it, the fridge was drawing 6.3a, does it do this for 24 hours a day? If so, the draw from the fridge alone would be 151 amp hours. My solar panels only put in 55 amp hours, so my shortfall would be 96 amps a day, or in other words, one full battery. This can't be right surely? I understand that we do have a 'deficit' each day from the fridge, but how much is it really? Does the fridge 'cycle' between power needs? What is the REAL amp use of a fridge in 24 hours?
The only other question left remaining is; Given some cash restraints, what would you guys choose to have fitted to assist us? (We will be having a new large charger fitted, that's a given)
A) An extra battery fitted (i.e 120 a/h AGM) to go with our two current 100 a/h lead acid batteries) or.....
B) An extra solar panel (say 120 watts) to compliment the existing two panels and the existing two 100 a/h batteries

As someone else pointed out, I don't want to throw away two decent batteries if they can be fully charged up with a decent charger. Your thoughts are most welcome. Which would you go with, A or B??

Cheers,

Paul & Val

Plendo · Guru

Hi Wirrof, I am glad to see you stopping and taking stock before you rush out and spend money. I have just read your thread from start to finish, and you have had some great advice, and a fair bit of deductive analysis of what your system is based mainly on some facts, and some measurements.

I think your last post sums up what you have pretty well, but maybe it could be worth just confirming a couple of things before you spend teh hard earned cash.

1. It Looks as if you are suffering from a system imbalance, where your combined load is consuming more power than you are generating. And yes your fridge can be expected to cycle, and as indicated earlier about 60ah would be a reasonable daily load, unless it is extremely hot, or the fridge gets opened a lot.

2. It is likely that your batteries are OK, (SG in the green), but again this is not confirmed.

3. You know your 240V charger is inadequate, and inappropriate.

4. You do not know the profile of your solar panels, as in wattage, and what voltage they are generating power at.

5. You talk about adding an AGM battery to your set, this will then make it difficult to charge, as AGM and Flooded cells charge differently. I suspect you do not need to add a battery anyway.

I would suggest the first thing to do would be to understand a bit more:

a. Buy a better battery charger, remove the loads (turn things off), and charge them properly.

b. Measure the voltage, and the SG, and then let them sit for a while, overnight would be good, and measure again.

c. Did the batteries hold up ?

YES, then address the rest of the system.

NO, then it may be time to look at replacements (unlikely).

If your batteries are OK, they should be enough to hold you up overnight without issue, you might even get two reasonable days from them. Thus if free camping in reasonable weather with sun and reasonable solar they would be fine.

Given that you appear to be consuming considerably more power than you are generating, I believe you will need to address this imbalance. The obvious way to do this is to add more solar, but before you do there are a couple of things worth checking:

a. What roof top realestate do you have, what shape is it. (may limit the panel(s) you add).

b. What voltage panels do you need? The closer you get to your current panels the better. I expect Brian would be able to tell you how to get this information from the PL20 (I do not know the PL20).

After reading everything below I expect you will find you need: a good battery charger, and more solar.