Voltage Drop

[svencool]

I have 4 12v 100ah AGM batteries, 2 sets of 2-12's in series and then paralleled for a total of 200ah at 24v. The batteries are probably 14 months old and I bought them brand new. This setup powers my entertainment center at night. The whole setup uses about 253watts. When I get home in the evening using Graham Ross's App Classic Monitor says my 200ah battery bank has 214ah in it.

Question is My batteries are topped off and I'll turn tv and receiver on 7:16pm and watch tv. Like I said this setup uses 253watts after about 3 hours and 45 minutes and my Tri-Metric meter went from 100% to 88% and Graham Ross's app said my batteries went from 214ah down to 181AH's and at 22:41pm my battery via the classic read out said 24.08volts and 22:47pm battery was 24.6 and 22:52pm battery was 24.4volts and at 22:58pm battery was at 23.8 and my inverter alarm started.

How can I only pull out of my batteries less than 20% and that alarm go off? 200ah less 20% is 160ah. Something is not right or I'm just confused which is quite possible. Can someone explain this to me? Thx....

Mike

[Taos]

Hi Mike
Theres a lot of info missing for anyone to give you a accurate answer , how are these batterries wired ,agm batteries need same cable lenght and size , there internal resistance is lower then flooded batteries ,plus they should be wired to a buss bar , and inverter cables are hooked to the buss bars for equal charging or discharging , other wise one or two batteries takes the major load and wear out in no time , disconnect the batteries from each other and inverter and measure each batterie voltage individualy if voltage varies a lot (more then a 1/4 volt ) you have a problem , were the batteries all purchased at the same time , same date code , also we need to know more about there charging life and discharging life , if you discharge the batteries to 50%or more  some batterries are at the end of there life in a year or two , were the batteries sitting for a long time in a discharged state ! This could damage them , what brand of batteries ? , we need info , solar panel wattage ,

[svencool]

All cable lengths are the exact same size and length and I used 2 gauge copper stranded wire also. I have the negative off one bank and the positive off the other bank. All batteries bought as the same time. I've never took more than 15-20% out of the battery bank at any given time. That's going off the Tri-Metric usually at the end of the night when I turn everything off the Tri-Metric will say usually 83-87, starting out at 100. It's hooked to a classic 150 and I use this system most everyday and most of the time its charged and ready by the next day. They days where it didn't to 100% I skipped watching TV. I have 8 300w panels open circuit voltage of 46.12v Short circuit current of 9.56 amps, Optimum Operating Voltage 37.47v and Optimum Operating Current 8.01 amps. They are wired in 4 strings of 2ea in series and run to a combiner box. Hope this helps....

Mike

I used this type setup that came out of the Samlex Manual except mine are 12v batteries

[Taos]

The only thing that bothers me is you don't have your inverter cables going to a buss bar  ,like i said these a.g,m batteries really need buss bars , the reason i tell you this is i had my batteries wired like your s and had a problem with the battery closest to the cable going to the inverter , i replaced this battery with one about the same age off my r.v. (   all my batteries should have been replaced at the same time ) but very expensive so i decided to put two buss bars in and hope for the best ,  i would disconect the cables and measure voltage of each individual battery, a least you can check this , and lke i said if you see a voltage difference have your batteries tested , if they turn out good then look elsewere ,but from what your telling us your batteries have no capacity ,either low on charge or no good . But start with the voltage test .  Thanks for giving us more info ,it makes it easier for us to help you .


Don

[svencool]

Can you give me a picture of how you have these hooked up to a buss bar? Pictures are worth a whole bunch of words lol.....

[ClassicCrazy]

I would put a load on your inverter , then check the voltage of each battery to see if one of them is taking a dive.

AGM batteries can show good voltage with no load but drop rapidly under load when they are bad. Another thing to check is when they are charging feel them to see if one of them is getting hot . Or take them apart and load test each battery separately .

Here is some info on wiring up parallel battery strings

http://www.smartgauge.co.uk/batt_con.html
Larry

[svencool]

I would put a load on your inverter , then check the voltage of each battery to see if one of them is taking a dive.

AGM batteries can show good voltage with no load but drop rapidly under load when they are bad. Another thing to check is when they are charging feel them to see if one of them is getting hot . Or take them apart and load test each battery separately .

Here is some info on wiring up parallel battery strings

http://www.smartgauge.co.uk/batt_con.html
Larry

Well I have a 24v DC to AC Inverter so my batteries have to be wired in series then back to parallel.... I've seen this link before But I would like to learn more about running these batteries to a bus bar and then hooking my inverter to that. This weekend I will separate the batteries and test them as well...

Mike

[Westbranch]

Do you have a Clamp Ampmeter?  If not get one so you can measure the amps each batty cable is passing through, that should show you the weak component...  it can also identify a loose connection.  Have you retorqued all the connections this year?
hth

[svencool]

Do you have a Clamp Ampmeter?  If not get one so you can measure the amps each batty cable is passing through, that should show you the weak component...  it can also identify a loose connection.  Have you retorqued all the connections this year?
hth

No just a Fluke Multimeter but I can get one. I just switched over from a 12v setup to a 24v setup. So all connections are nice and tight...

[Taos]

Mike if you look at example 3 ,that Larry posted thats the way i have mine connected ,were all cables meet thats were for the positive cable leaving to the inverter,thats were you put a buss bar positive ,,,,then do the same for your negative .  And since your a 24 volt system you need to wire 2  12 volt batteries in series , and then  wire this to the buss bar in parrallel do this twice to make your battery bank . Oh and if you had your batteries not wired properly  for awhile its posible there toast ,you can try charging them according to the manufacture mine( sunxtender )have lots of info on recovery charging ,but you should follow the manufacture instructions ,my battery manufacture does allow for a equalizing charge ,but follow the manufacture instructions , lots of A.G.M. Batteries cannot be equalized. As a battery life is closer to the end ,as Larry said when you put a load on it ,voltage drops fast ( it has no capacity) you can try hooking up your inverter like Larry said to load each set of batteries to isolate the weak ones ,make different combinations to isolate the bad one , and checking voltage with your fluke meter , also make sure all batteries are fully charged before test .

Don

[Taos]

Oh forgot , Mike you mentioned you had a 12 volt inverter and changed to 24 volt , were these the same batteries you were using ? Because when in 12 volt you would be drawing double the current then 24 volts ,= more wear on your batteries and also would multiply your wiring inbalance if wired inproper.

Don

[ClassicCrazy]

Do you have a Clamp Ampmeter?  If not get one so you can measure the amps each batty cable is passing through, that should show you the weak component...  it can also identify a loose connection.  Have you retorqued all the connections this year?
hth

No just a Fluke Multimeter but I can get one. I just switched over from a 12v setup to a 24v setup. So all connections are nice and tight...

This inexpensive DC clamp on  meter has pretty good reviews and extensive testing by meter geeks if you look it up on youtube .
http://www.ebay.com/itm/UNI-T-UT210E-Digital-Clamp-Meter-Multimeter-Handheld-RMS-AC-DC-Mini-Resistanc-/252445358891?hash=item3ac6ea7b2b:g:Q00AAOSwoydWj2id

May be able to find it already in US for a few bucks more.

Larry

[svencool]

Oh and if you had your batteries not wired properly  for awhile its posible there toast.

Don

Don thanks for the input but I had the 4 batteries wired in parallel for a total of 400ah at 12v before and was wired correct. All my wires were the same length so I could minimize the resistance thing. I had them wired like Method 2. They charge just fine and seem to always go about 4 hours. So I don't know if what I'm running that's all I can expect or if there is something wrong. I just ordered one of the Clamp meters and it will be here tomorrow. I will check my batteries this weekend if I have a chance as I have to work both days. I do appreciate everyone's input as that's the only way I will learn something

[Taos]

Mike  even in method 2  you could have damaged your batteries ,been a 12 volt system larger draw and charging amps = more wear then a 24 or 48 volt system . i had mine wired like #1 , with 12 batteries for a 48 volt system , 4 batteries in series and 3 parallel runs , it took out one battery in just over a year , it was replaced with one about the same age from my r.v. And i wired them correct with buss bars and there 6 years old now and still ok , im sure i should have replaced them all but too expensive. I also think i lowered there life span.  Once you get that meter ,you will be capable of finding out if a battery or more is bad . I also rotate my batteries yearly as there in a cabinet in my basement ,the top shelf batteries are higher( 4 feet higher )  therefor warmer then the bottom shelf almost on the floor . Not sure if it makes a big difference but after loosing one battery figured why not..
Don

[svencool]

Do you have a Clamp Ampmeter?  If not get one so you can measure the amps each batty cable is passing through, that should show you the weak component...  it can also identify a loose connection.  Have you retorqued all the connections this year?
hth

I picked up one of those clamp meters that was suggested here and I was just curious. How would the meter tell me if I had a loose connection?

Mike