Batteries dying quickly

owen_a

Hi,

I have two 12v 100Ah Deep Cycle batteries connected in series to give me 24v @ 100Ah. I have this connected to my TS-MPPT-60 charge controller which keep the batteries charged to about 26.1v - so that's about 13.05v per battery. 

I have a 2000W Photonic Universe Pure-Sinewave inverter connected to my batteries and on all the time. It's currently powering my phone charger that charges my phone every night. My phone takes about an hour and a half to charge. The charger uses about 14Watts of power when it's charging the phone, so that's about 0.06Amps of current on the AC side @ 230v. Now, 0.06A for AC is 0.63Amps DC. If we say we should never discharge batteries below 50% of their rating, that's 50Ah - please correct me if I'm wrong. So, if we divide 50Ah / 0.63A, that equals 3.3 days of use.

The problem is, that's theoretical, but whenever I take my phone off charge, the batteries are always at 24.59v, which is 12.29 per battery. If we take a look at the picture below I grabbed off Google, we can see that they are at a 60-70% charge.


Is this right? Surely it can't be? 3.3 days use out of fully charged batteries yet they get run down to 60-70%? They did get run down to 22.58v once on load, however I have had four Equalisation sessions for 1 hour since then. Do I need to equalise for longer to remove the sulfation?

Thanks,
Owen

westbranch

first off, do you know the Tare load of that inverter, its probably > 40W??? 
I hope you have a significant need for that big whopper of an Inverter..other than the cell phone?.
 If you don't have some heavy loads you need to get a much smaller Inverter ...
Do you have another charger than the PV ? 
what are the charge parameters on the TS 60 set at? 

owen_a

Hi,

Thanks for your reply. Yes, the inverter is going to be used when there are power cuts for boiling the kettle, etc. I also plan to have a home server running off the inverter and my soldering iron when it's needed, along with my raspberry pi.

The technical specs for the inverter are;

• Input: 24V (20-30V) DC
• Output: 230-240V AC
• Output frequency: 50 Hz
• Output waveform: pure sine wave
• THD: < 4%
• Continuous power: 2000W
• Surge power: 4000W
• Peak efficiency: 90%
• Low battery shut down: 20.0V +/- 1.0V DC
• Low battery alarm: 21.0V +/- 1.0V DC
• High voltage shut down: 31.0V +/- 1.0V DC

The charging parameters on the TS-MPPT-60 are;



The batteries I'm using are these ones.

Kind Regards,
Owen

mike95490

To correctly use voltage as a measure of charge, you have to let the batteries rest, with no load or charging, for a couple hours to stabilize.  To fine tune this reading, you need to also take the temperature of the batteries, their voltage changes with temperature.

Or you can use a hydrometer with temperature correction table, to test the specific gravity of the electrolyte.

westbranch

OK  a couple of shots for you #1 shows ~ 25W in Power save mode,
#2 shows load in Watts when inverter is providing power , what does it show when you charge your phone?

owen_a

Hi,

Thanks for your reply. When I plug my phone charger into my energy meter plug (used to see how much power a device is using), it shows about 14 watts constantly. That's 0.63Amps @ 24VDC AND 0.066Amps @ 230VAC.

Am I right in saying, if it's using 25watts when on, then with my phone charger plugged in charging my phone, it's actually using 25w+15w = 40w? So, 40W/24V = 1.66Amps.

Kind Regards,
Owen

mike74820

if it like my pure sine wave inverter it waste amps like crazy. just to charge a phone like you i wanted to see how much amps i was using while using the inverter and bang 2.5 amps to a 5 volt usb port to charge a  black berry type little phone. my advice is stick a kill a watt meter on it and see how much you are really using out of that inverter

westbranch

please clarify what you are using as my energy meter plug .  Watts is the best description of consumption and then you can reference the voltage, and amps of available, 24V DC is important as we are trying to decipher what is going on with the battery  ...
To be clear you should only talk about the loads in AMPS at 24V DC. 
Your charger (appliance, etc.) will be rated in AC input and DC in output...  like wall-warts to power X,  y  , or Z  

you are probably correct with that calc as the data sheet is rather vague and the IDLE tare rate may be higher than the Power saver mode...
 
the way to measure the DC Amps is with a DC Clamp meter

owen_a

Hi,

This is the energy meter plug I'm on about.

Kind Regards,
Owen

zoneblue

im not sure your getting what wb and mike are trying to convey to you. An inverter draws power on the DC side even when you have no or little loads on it. In the 2000W range, a great inverter would be 15W, a nasty one 80W. Given your inverter is on teh cheaper end, (just about the cheapest i guess, given the specs dont say, gees), you need to establish what the idle/tare is. Its likely your biggest load.

westbranch

Owen, that energy meter only measures the amount of AC power you are using..

zoneblue

If all you need is the phone charger, turn the inverter OFF, and get a 12V to USB converter, any old car usb charger will do fine. 2 bucks from ebay.

South Africa

Those batteries are a very good place to start learning about batteries.

My 2 cents, over and above what has been said above, I have used similar batteries where I live, just under another brand.
They are ok for leisure but not really for solar applications, in my opinion. Even less so if you cannot add water to them.

The inverter load of 40w, as mentioned above, are going to tax those batteries a wee bit over time.
Friend of mine had similar batteries with inverter load of 25w, just being on. When he added lights at night, they did not last more than a year before capacity was substantially reduced.

owen_a

Hi,
Thanks for your replies. I've been in touch with the engineer over at the company who I bought the inverter from. Just FYI, it wasn't cheap. They stated it was about 0.8 – 1.0A during idling. I'm not sure if this sounds right or not since I haven't measured the current between the inverter and the battery when nothing is plugged in.

westbranch - Yes I know that plug measures the AC voltage/current/power, but you can calculate how much current an AC appliance is using in terms of DC if you know the voltage and current which the AC appliance is operating at.

South Africa - What batteries do you recommend? I thought these would be good in my opinion being Lead-Acid and 100Ah...

South Africa

Personally, I like Trojan T105RE's, not the T105, the T105RE's.

zoneblue

OP, that inverter, (this one? http://www.photonicuniverse.com/en/catalog/full/181-2000W-24V-low-frequency-pure-sine-wave-off-grid-inverter-peak-power-6000W.html ) looks very much like one we see around here branded Anypower and other brands. If its the one i think, then the quality isnt so terrible. But not mid range.

Still the missing idle from teh specs is not good, (just get a clampmeter and measure it), but if we go with 1A thats 24W. Thats ok as it goes. However....

24W * 24hrs = 576Wh/day.

For a 100Ah battery (which is 100Ah*24V= 2400Wh), thats a full quarter of teh banks capacity. Without doing ANYTHING, youve cycled the battery to is lowest recomended daily DOD. And you dont give PV specs so we dont know how well its being charged.

Also...

A 2000W inverter needs <=0.25C discharge capability, which is =2000W/24V/0.85 = 100A, which is 1C for your battery. Ie its too small for that inverter.

If you can give solar specs well see if thats all good.

zoneblue

Curious about who actually makes these i found these:

http://www.alibaba.com/product-detail/Single-Phase-Power-Star-Pure-Sine_1686863075.html?spm=a2700.7724857.29.66.nyYwZL
https://www.you tube.com/watch?v=WY-8L_ngo3Y
https://www.you tube.com/watch?v=WpqAmLDXdz4
https://www.you tube.com/watch?v=M_A7o69rPhE
http://www.aliexpress.com/store/product/3000W-Grid-off-Inverter-with-Pure-Sine-Wave-Form-Any-Power-Combined-Inverter-Charger/709295_579679895.html
https://forums.energymatters.com.au/solar-wind-gear/topic3344-60.html
http://www.electro-tech-online.com/threads/powerstar-inverters.113420/

You can see the resemblence at these links and some of the issues, notable among them VERY high idle. The 25W figure is the powersave mode as Wb pointed out. If powersave is not in effect all bets are off. Figures like 108W, 220W and all sorts on teh forums.

The company is called Shenzhen ZLPOWER Electronics Co., Ltd.

I saw one of these in a beach house we rented for a weekend and assumed they must be ok. But they are cheap chinese inverters like all the rest, and better avoided.

owen_a

Hi,

My solar array is just 3x 300W LG mono X Neon panels in parallel to give me a theoretical maximum output of 900 Watts. The Panels can reach about 40V, but for charging it's normally at 29v.

I've had a few dull days so far so I've only been generating about 116W - 180W @ 29V. (~14.5V across both batteries).

The inverter I'm using is this one for anyone who's interested.

What batteries should I use then which aren't too expensive? Mine cost about £64-67. I'd say £100-£120 is my limit (I live in the UK).

Thanks,
Owen

zoneblue

900W peak into 24V will produce = 900W/28V*0.77 = 25A peak, thus youre aimed at a battery that is around 250Ah. (0.1C). That also gets you closer to supporting a 2kW inverter.

If it was me id be looking 4 x GC2s in series. These are the batterys they use in golf carts, and they are usually reasonably cheap and are a true deep cycle battery, unilike the ones you have.

Seems like this is a hobby for you so do yourself a favour and head online and buy yourself a clampmeter. This one has served me well. http://www.dx.com/p/uni-t-ut204a-1-5-lcd-digital-clamp-multimeter-1-x-9v-6f22-127969#.VsTqnytJ9uE

BB.

I am worried about your solar panel array... I guess that you have three panels in parallel for Vmp-array=29 volts.

The Vmp of solar panels are measured under test conditions. In real life, the panels are going to be closer to 27-24 VDC Vmp-array on a hot day. That is really not the optimum charging voltage for your 24 volt lead acid battery bank.

Your two better choices are to choose to wire the three panels in series for Vmp~87 VDC and get a MPPT controller that supports that (relatively) high voltage array.

Or second, get a 4th panel and setup up 2x series by 2x parallel array with Vmp~58 volts--And (the same or different) MPPT controller designed for that working voltage and battery charging current.

Otherwise you will be hard pressed to harvest the optimum power from that array to your 24 volt battery bank as currently configured.

-Bill

zoneblue

Indeed Bill, even if they are 72 cell panels (probably are), the Vmp is still "genarally" too low for mppt. It might work on a Morningstar (so ive heard), but wouldnt on a Classic. As a rule. As you say 2S2P would be ideal.

owen_a

I have a Morningstar TriStar 60A charge controller. I say 29v because that is what the controller seems to be charging my battery bank at. I have posted my settings above for the charge controller so whether they need to be tweaked, I'm not sure.

Vic

Hi Owen,

Am late to this ...

But,  two things,  Owen does have the TS- MPPT-60 CC.
AND,  those 300 W LG PVs are (surprisingly)  60-Cell units,  with a  Vmp of 32 V @ STC,  probably just too low a Vmp for almost any MPPT CC.

Seems,  that if the PVs were rewired as one string of three PVs,  things would have to be better,  IMO.

However,  one might expect that those PVs in good sun,   might be able to produce about 25 - 28-ish Amps,  which would probably be a bit too much current for most 100 Ah Flooded  batteries.

So you might want to be careful,  or perhaps try to limit the max charge current,  which has its own negatives.

Perhaps a larger battery bank is in order ...

FWIW,  Late Vic

owen_a

Hi,

The batteries are Sealed Lead-Acid.

Also, my solar panels are these ones.

Kind Regards,
Owen

Vic

owen_a said:

Hi,

The batteries are Sealed Lead-Acid.

Also, my solar panels are these ones.

Kind Regards,
Owen

YES,  indeed,  those are the ones that I had found (probably should have Linked to them).

So,  yes,  the Vmp IS 32 volts from these 60-Cell PVs.  Believe that having those three PVs in parallel gives a too-low voltage into the MPPT CC,  IMO.  Would it be difficult for you to rewire the three PVs into one string of three,  for about 96 volt Vmp?   YES,  this is a bit higher than a general ideal for many MPPT CCs,  but,  seems that this could result in better charging.  If your SLA batteries are Gel,  then,  perhaps you have adequate,  or almost-adequate Vmp.

Do you have a model number for your batteries?   Many SLA batteries appear to be Gel-type.  Are your batteries AGM,  or Gel,  if you know?   OR,  do you know if there is a specified limit on charge current,  and what that might be?

Thanks,   Vic

owen_a

Hi,

@Vic - The batteries have LV26MF written on them. Baring in mind I only have two of these wired in series to give me my 24v @ 100Ah. I'm glad I didn't buy another two if I need bigger batteries, which brings me to my next point...

I did a test and had my inverter power my home server. My home server consumes 2.75 DC Amps (I calculated that from the website specified previously). Assuming my inverter uses 1 Amp, then if we should never take a battery below 50% of it's charge, then 50Ah / 3.75A = 13.33 hours. I checked my home server and saw it had been on for nearly 12 hours, and the batteries where nearly 50% discharged, but it was discharging at a very healthy and normal rate. If I left it on any longer, it would of met that target quite accurately. This means, thankfully, my batteries are fine, HOWEVER, I do need better batteries for that inverter, and if I want to run the server, or other items for longer periods.

What do you all think of this type of battery?

Thanks,
Owen