Motorhome Solar Power System Issue

[thedigger]

I had trouble with my 200 amp/hr lead acid,just kept giving less supply,went 180 amp/hr,lithium ion ,they say they as good as 300 amp/hr,and it weighs 1/3 of the lead acid,and I would go along with that.
Leads dead!!!!

Regards Frank

 

[fluffyboxerfan]

Wow thank you everyone, seems like I have a lot of homework to do re charging and chasing down issues I never even contemplated. i.e. reverse discharge and diode faults on the panels. Unfortunately the best I can do for now is get the batteries checked, as I am heading away for work for 10 days and won't be around to do the rest of the trouble shooting.
My panels are wired in series and the batteries are in parallel. Definitely something has changed though, just have to find what! Pretty sure the alternator is charging the batteries, but will double check that as well.

I shall post and let everyone know how the batteries have tested, hopefully can get the wife to drop them in to Battery World on Wednesday.

If anyone has any other ideas as to faults that may have occurred please feel free to share. I will get the wife to check back and keep me informed by phone. You have all been an absolute mountain of knowledge and offered some great scenarios.

thanks again,

Bill

 

[fluffyboxerfan]

Thanks Frank, good to know about the Lithium ion batteries, but my pockets aren't that deep unfortunately. :lol: How are they charged?

 

[BigWave]

Frank,
I agree with TD. Most AGM Deep Cycles shouldn't even be taken below 50% charge for reasonable life expectancy, whereas Lithium Iron Phosphate LiFePO4 batteries are safe, less than half the weight, double the usable capacity due to having a much deeper discharge capability than lead acid. They also last a proven 10 times as long (discharge cycles) as most AGM Deep Cycles when both types are cycled within recommendations. I've started using them on my Suzi GSX1400 - can pick up between two fingers - massive starting capacity as well. I'd say one or more of your batteries are Roo#*ed mate. Also, your charger is little more than a trickle charger for those puppies. 40A+ would likely do the trick if your supply can deliver it.

 

[condor22]

Fluffy,

I would advise against adding another battery at this point, they really do need to be of the same age, make, model and preferably batch.

Lithium Iron are better, but you will pay $1,800 for a 150AH, so that is one helluva expense considering your current needs.

Re wiring panels in series, yes that will work, but if you have a problem with 1 panel or any interconnecting cable, the whole system goes down.

For that reason, I use my 2 panels in parallel, each goes through a cushioned 10A circuit breaker and are then connected in parallel before the controller. That way I can isolate either or both. Apart from isolating 1 if faulty and still having the other in use until repaired, I have another reason for this.

I can also charge from a Redarc BCDC charger when driving, so I turn the panels off to avoid 2 lots of charging that may be running at different voltages or current, not to mention charging at too high a rate if both are running.

Although a bigger, heavier method, it is better to use 1 big Deep Cycle ie 1 x 350AH which may weigh 70-80kgs, than 3 x 120AH (which @ 30kg+ each is heavier in total) in parallel. That way there are no issues re compatibility or interconnection issues. Space and ability to install may be what decides using smaller batteries in parallel.

 

[BigWave]

Quite right Condor re expense, but they will drop in price quickly (Aluminium batteries are on their way) and will likely outlive me - I opt for reliability. As for paralleling Lithiums, I have no idea? Sorry to be off topic a bit there FBF.

 

[Nightjar]

Fluffy,

Re wiring panels in series, yes that will work, but if you have a problem with 1 panel or any interconnecting cable, the whole system goes down.

The jury is out on this one, have read that partial shade on one panel kills the whole system.
Have just completed tests on two 60W panels in series through an MPPT controller. Covered one panel completely and was still getting amps flowing into battery.
Don't have any accurate reading other than an Volt & Ammeter.

 

[fluffyboxerfan]

I have a diagram of how the panels are wired but I apparently need to have 10 post to upload anything.. grrrr.
Not sure if it is series or parallel? Have a positive and negative coming out of each panel through a DC Isolater/removable fuse into charge controller then to the battery bank (In parrallel). A 250A fuse on the positive between batteries and inverter, then to AC supply.
We had the local Electrical who specialise in Solar advise us and draw up the diagram.

Have the meter that came with the MPPT Panel, it displays :" Solar panel voltage, battery voltage, battery current, load voltage, load current, battery capacity AH, battery temp, battery type, Load Timer 1 mode and load timer 2 mode, discharging accumulation AH discharging accumulation WH as eight team data." Guess I better work out how to read it a lot better than I have been doing.
(We are not using it in Load mode)
Just having a look in the instruction book (handy gadgets those, should read them) I have only been taking note of the one screen which is the battery voltage and battery current.

 

[BigWave]

It becomes way more complicated particularly considering the mode of shading (but won't go into that here - checkout vertical vs horizontal shading). "Can kill the whole system" is the correct answer - that's why you were still getting power albeit reduced.
Protecting the array and maximising its output is what the two types of diodes are for - isolating the shaded cells/panels. If the panels are in series, the bypass diode bypasses the shaded cell(s) with a ~0.7V drop (per series section - there's often many series sections per panel), and if in parallel, the blocking diode just blocks the shaded panel from contributing and prevents reverse polarity damage to it. So, either way, you'd still have output with only a single shaded panel. I've seen some very stupid installations where less than 10% shading kills an entire high power array, and am happy to discuss in another thread.
Still betting FBF has stuffed battery(s).

 

[Tathradj]

I also ran a separate 2 core lead for each panel.
Though I have seen 3 core utilized with a common negative for 2 panels.
But always a diode on each positive.
I know that most modern controllers have non bleed in them but,
How effective or reliable in a low cost unit this is remains for me to find out.

 

[condor22]

Disregarding the term "Panel" and instead focussing on "Cell" (to explain, "A panel consists of a group of cells)

Mono Crystalline Cells and Poly Crystalline Cells will both drop off when shaded. So will Amorphous cells such as the Unisolar panel, but they don't.

The difference is as Bigwave notes; How the cells are connected when assembled to the panel. The Unisolar Amorphous panels use the Bypass Diode construction method. However they also have other differences, Plus - Amorphous cells are more tolerant to heat, in fact they work better when hotter. Negative - They are also more expensive and per square metre of cell, output less than Mono or Poly.

Most common cheaper panels have Mono Crystalline Cells, many of the Ebay cheapies do not have bypass diodes and will drop of drastically with only a small shaded area. With Bypass diodes, the drop off in output is relative to the % of shaded area and the panel will therefore continue to produce albeit a lower output. This is still preferable to none.

The other type of Diode used on some panels as Bigwave eludes is the reverse polarity Diode. It's principal use (in simple terms) is to stop the battery from feeding back into the panel at night. Better controllers will also have this protection.

Mono and Poly cells are also heat affected, in that when they get really hot, the output reduces.

Most panels, particularly the cheaper ones work from light in the Visible Spectrum and most are what are termed "Front Gridded" i.e. the lines or grid you see on each cell.

The more expensive cells that appear black (shiny black) are primarily rear gridded and in at least one manufacturer from the USA, work not only from visible light, but also the Infra Red and Ultra Violet spectrums. They therefore output more power in lower light (winter time) but also for more sun hours per day. i.e. when the sun is low on the horizon, dawn and dusk, the angle through the atmosphere produces IR light, red sun in the morning etc. Plus when overcast, visible light is reduced, UV can still be more intense. That's why on a dull day you still get sun burn.

Most of the folding suitcase type solar panels are fitted with a simple controller and most output at 13.8 or so volts. A good MPPT controller designed for AGM batteries will output at up to 14.5 volts and are multi stage. So it's not hard to work out which is better for your battery.

 

[Tathradj]

Amorphous cells are more tolerant to heat, in fact they work better when hotter.,
A good MPPT controller designed for AGM batteries will output at up to 14.5 volts and are multi stage.
load on with the fridge running I have seen up to 14.8 volts.

That is what I have in a folding 160 watt.

 

[condor22]

Fluffy - when using a system the size of yours and for independent living, you really do need to know exactly what's going in and coming out.

As an inverter the size of yours is connected directly to the battery the only way to include it's current draw is via a shunt. 3000W divided by 12 = 250 amps so that is at least the size shunt you need. Here is an example;

http://www.rammeter.com/ram-meter-b250a50-250-amp-50-dcmv-dc-current-shunt.php

You connect the shunt using the larger holes inline between the battery and the inverter input (usually on the negative line). The small screws you see in the picture are what you connect to the metering device. You will note that it states it is 50mV, it is this small voltage that varies and is measured then converted to the correct amperage.

http://www.plasmatronics.com.au/downloads/PLTypicalInstallInfo.V1.11.pdf This is an example of how it connects. The PL20 manages lower loads such as TV and lights. The shunt is in the higher load circuit and using the PLS2 to measure and convert, then sends the data to a separate input to the PL20.

The PL20 is limited to 20amps, however it will record higher amperage via the PLS2 and shunt. If your controller has shunt capability then it needs modifying, or. You would need to ascertain your solar input first ie 500W convert to expected amperage ie approx. 40 amps then pick the next size controller up that does have shunt input.

Apart from the inverter most other 12 volt items are low current draw, the biggest is probably the water pump. However it is not just one item it is the total maximum you might use at any one time.

My advice is; measure all solar going IN and rewire all loads to be measured going OUT. Including the inverter (with shunt).

My inverter is only 150W for small stuff ie detector charging or my Satellite receiver. So I don't need the shunt. But I still measure everything going in and out using the BM PRO as noted in my Bush Power thread. If I use the microwave or the wife the hairdryer, I crank up the genny. The difference is a caravan v motor home

 

[Luke]

Hi all,
Interesting reading and lots of knowledge here.
I've done pretty much same system when I build my camper last year. Two 200W solar in parallel straight to 30A controller (35$ ebay, that's why I didn't bother to put any circuit braker between, just after).The same three 130Ah AGM deep cycle battery.I thought better a bit of an overkill then underkill as they don't like to be discharged over 50% (shaded/rainy days).1500w inverter just for little use here&there of non12V appliances. No microwave for me as I don't like my food to by "killed" by those waves A water pump, 24"LED TV (36W),few LED lights and couple of USB outlets for charging.So biggest consumer of current is a 92L 12v fridge.
When driving charging over a voltage sensitive ryley isolator, no switch to turn solar off as I assume the solar regulator cuts it off anyway as voltage in the circuit increases.
So far so good.
I hope not but it looks like those batteries/battery might be slowly dying in your case as already some members suggested. I'll be waiting for your report how the battery test end up.
How long was a warranty for them? 2 1/2 years? Mine says should last 1000 charge cycles.In your case would be far away from there as you don't use yours every day.
Another evidence of the "light bulb conspiracy"?
Though my first post will be about prospecting, well...
About to get my first coil for my 5k.Have only standard 11"mono and DD.
Thinking about a 17x13NF, would like more coverage and depth.I blame the coil as I haven't found any yellow yet and no I don't want to hear it's not the coil
Just noticed that coiltek makes 17x13 as well bit cheaper. Thoughts which one might be a better choice? Any advice appreciated. To "17x13nf" thread so I don't mess in this one.
Thank you all.God bless this site and apologize for my English as of an still english learning immigrant from Czech rep. and new member of PA.
Cheers all.
Lukas

(Fluffybexerfan, good luck with batteries)

 

[Nightjar]

May be of some help.
Always remember,
.
" A bit of load will tell the story. "
.
What I do to test a battery,
12v only.
Utilize a 100 watt light bulb.
Connect a volts meter across the battery first.
Record the voltage.
Then connect the light bulb across the battery.
let it run for 1 hour.
record the voltage and compare the two.
If you need more brute force,
Use two light bulbs.
Take safety into consideration as things especially the bulbs will get hot.
Beware of sparks and gas.

Have used similar method many times and as recent as 2015 when a battery supplier used his load tester and told me there was nothing wrong with their battery.
Set up your method and drove to the shop and showed them how the battery dropped off rapidly under a continuous low load (Headlight globe)
They gave me a new battery under warranty, which also failed first trip away. Didn't bother returning to this store, bought a recognised brand.
As per the old quote; "Buy cheap, buy twice.
In the days of the common vented batteries it was so simple testing with a hydrometer. Battery could show near full charge with voltmeter but a cell or two could be well down using hydrometer.
Which sounds like your case Bill.

 

[fluffyboxerfan]

HI everyone, Bill asked me to post re testing of the batteries. I took them in yesterday, apparently he said they passed the initial quick test as in said they haven't dropped a cell, apparently one was a little down than the other two, but he is going to do a series of load tests on them, but I won't have them back or know the results till Monday. I will keep everyone updated.

Regards,

Karen

 

[condor22]

Thanks Karen,

I assume he is testing them as separate batteries, in that 1 is down. The thing is that when in tandem (parallel) a bad one will affect the other 2.

Look forward to you posting the results.

 

[fluffyboxerfan]

Yes Condor he said he will be testing them individually, apparently that's why it will take several days. He said he would test each batteries 3 times (i.e. charge and then put on load and then test and then charge again etc.,) to get an average? Should have a chart print out of each one. I will ask him for a copy so that I hopefully can post it for you.
He said the same thing one bad will drag the others down.

Karen

 

[bazxa]

I replace my batteries in pairs if they are not electrically isolated to minimise the chance of the older failing and damaging the newer battery.
there is a heap of great info here, thanks to those contributing.
Following this with interest & would love to know the outcome.

 

[condor22]

I know that everyone has a different need for remote power and there are many ways to achieve similar results. I try to look at the whole picture, put what is absolutely essential first in design and cost. I have an acquaintance who is an expert in remote and independent power. Unfortunately, although great stuff, some of his designs and equipment are at considerable cost, $$$ wise. He is into things like 12VDC air conditioners, large 300AH plus AGM batteries, motorhome toilets that don't use water and systems big enough to provide whatever 12VDC and 240VAC is needed i.e 6 x 150W solar (larger motorhome). However, most of us are on a budget and have limited space in campers and caravans. The following logic is but again only my opinion, but a starting point for design and I have said this before.

When it comes to larger Inverters 2000W and above, the drain on a battery system is huge, roughly 85-90 Amps per kW. The cost of the Inverter (I would recommend only Pure Sine Wave) the additional cost of a battery bank to run it properly, the size of the charger to charge that size of bank, the amount of solar energy to also charge as well as possibly a DC to DC charger, need to weighed against how often and for how long that kind of kW+ 240VAC is needed and as Karen has mentioned about 10min a day. The cost of this equipment can rapidly climb to several thousand $s not to mention weight. This needs to be balanced against the fact that a 2kVA Honda will do all of this for roughly $1,500.

Modern caravans or older retro fitted ones have LED lighting that use 2/10 of bugger all power, 0.1 to 0.2 AH each. Most 12VDC TVs use 2-3 AH, small Kogan Twin Tuner PVR, about 17W @ 240VAC, a Satellite TV Decoder about 50W @ 240VAC. Water Pumps use roughly 6-7 AH, but are rarely used for more than 15minutes a day. A Diesel Heater averages 1 AH when running.

That about sums up basic needs (excluding special needs such as sleep Apnoea machines), both examples of 240VAC TV equipment will work on a small 150W Inverter. So totalling all needs as above, a 120AH AGM and 200W of solar is ideal, when using a 3 way fridge on LPG.

If using a 12VDC compressor fridge, 200AH of battery is a better option if using all of the above, 200W of panel is still enough, but could be increased up to another 100W.