How can my system batteries die in four hours

[Ghof]

First , I have 750 watts on the roof. An MPPT Outback fm80 charge controller and four t105 batteries in series/parallel 12v system, and each battery shows 6.67v. Charging at 14.8 float at 13.8.,
I equalize monthly. Water levels are monitored very often.
I have an 1800 watt zantrex pro inverter.
Last, I have a whirlpool residential fridge that supposed to pull 300 watts.
The problem is: the batteries last less than 5 hours.
I'm thinking the power is back feeding to the panels, I can't find any other power drain of significance.
Ideas or perhaps a solution, tests, anything!

 

[ghostwriter66]

Losing THAT much power you should be able just to touch the cabling and find your short ... Assuming you have a DVM ... Very unlikely the power is feeding back to the panels unless you hooked them up wrong ...

As they taught us at work - start with the panels and work your way all the way to the battery ... you will need a DVM with a AMP meter ...

After they are fully charged .. DISCONNECT all your solar from the battery -- put a amp meter on the battery -- and see what is going on .. could be a giant ass-short ... (yes that's a technical term) ... BUT you need to figure out is it your CHARGING system or your DRAWING system ...

also if its an RV - make sure that your inverter is not drawing from the battery to charge the battery ...

actually i would start with the battery myself .. you could easily have one with a collapsed cell .. putting money on that first .... way to do that is UNPARELLEL the batteries and see if the same results happen each time .. if it does .. then its NOT your batteries ... ie .. run 2 for one day .. then switch out the other 2 for another ..

an AMP meter is your best friend at this point ...

following

 

[John Frum]

This is where a shunt is really helpful.

Amazon.ca

 

[ghostwriter66]

This is where a shunt is really helpful.

Amazon.ca

actually a shunt will only measure in/out at one location .. he needs to find where that in and out is happening along a route .. DVM w/ AMP is going to be really the only way ... trace the amps going in from the panels to the battery .. disconnect the batteries when they are full -- let the batteries settle for an hour .. check voltage of each battery ... (if all the same) then hook up amp meter and see what kind of draw your getting from the equipment to the battery ... could easily be a collapsed cell or a short

 

[John Frum]

actually a shunt will only measure in/out at one location .. he needs to find where that in and out is happening along a route .. DVM w/ AMP is going to be really the only way ... trace the amps going in from the panels to the battery .. disconnect the batteries when they are full -- let the batteries settle for an hour .. check voltage of each battery ... (if all the same) then hook up amp meter and see what kind of draw your getting from the equipment to the battery ... could easily be a collapsed cell or a short

Actually just measure at the battery and disconnect components will likely suffice.
A clamp meter will certainly work too.

 

[Silentpower]

Fault with the load? Fridge seals OK? Compressor drawing more? If battery electrolyte is used evenly they sound OK. What is the duty cycle of the load? Could it be that the 750w on the roof is undersized to charge the bank fully while powering the load? Is this problem a new thing? Sorry for all the questions..

 

[Ghof]

Losing THAT much power you should be able just to touch the cabling and find your short ... Assuming you have a DVM ... Very unlikely the power is feeding back to the panels unless you hooked them up wrong ...

As they taught us at work - start with the panels and work your way all the way to the battery ... you will need a DVM with a AMP meter ...

After they are fully charged .. DISCONNECT all your solar from the battery -- put a amp meter on the battery -- and see what is going on .. could be a giant ass-short ... (yes that's a technical term) ... BUT you need to figure out is it your CHARGING system or your DRAWING system ...

also if its an RV - make sure that your inverter is not drawing from the battery to charge the battery ...

actually i would start with the battery myself .. you could easily have one with a collapsed cell .. putting money on that first .... way to do that is UNPARELLEL the batteries and see if the same results happen each time .. if it does .. then its NOT your batteries ... ie .. run 2 for one day .. then switch out the other 2 for another ..

an AMP meter is your best friend at this point ...

following

Excellent ideas, no amp meter but have dvm
Rv two panels on the roof to a combiner box # 6 wire to controller direct to batteries very simple setup all fused or circuit breakers. I've been trying to find the big ass short. BAS,, BIG ASS SHORT,,, IS ALMOST AS GOOD AS MY , GHOF, GREY HAIRED OLD FART!
THANKS , lots of tests to do when we stop somewhere. We are headed east on i 70 for a while.

Fault with the load? Fridge seals OK? Compressor drawing more? If battery electrolyte is used evenly they sound OK. What is the duty cycle of the load? Could it be that the 750w on the roof is undersized to charge the bank fully while powering the load? Is this problem a new thing? Sorry for all the questions..

It may be new as I didn't know what to expect when I i stalled the panels.

 

[Silentpower]

750w sounds like a lot, but given the hours of effective charge time, it may not be sufficient to replenish the batteries and drive the load. At a minimum its best to size a system to x3 the expected load, so 900w of solar might be considered the absolute minimum for you. Also, lead acid batteries increase internal resistance when partially charged for a while, and this can cause the terminal voltage to read higher than the expected soc. One draw back of lead acid is the lengthy time of absorbtion charge and topping off, but its crucial this happens for the health of your batteries. Its unlikely you'll achieve this under real world conditions with 750w solar.
Edited for spelling

 

[madmax]

First , I have 750 watts on the roof. An MPPT Outback fm80 charge controller and four t105 batteries in series/parallel 12v system, and each battery shows 6.67v. Charging at 14.8 float at 13.8.,
I equalize monthly. Water levels are monitored very often.
I have an 1800 watt zantrex pro inverter.
Last, I have a whirlpool residential fridge that supposed to pull 300 watts.
The problem is: the batteries last less than 5 hours.
I'm thinking the power is back feeding to the panels, I can't find any other power drain of significance.
Ideas or perhaps a solution, tests, anything!

You have to put monitoring on the fridge. My mid/small fridge draws about 250-275 watts... until it decides to turn on the defrost cycle. Then its a little over 1000. Still 5 hours seems a bit on the short side. Is that inverter working that hard?

 

[Silentpower]

You have to put monitoring on the fridge. My mid/small fridge draws about 250-275 watts... until it decides to turn on the defrost cycle. Then its a little over 1000. Still 5 hours seems a bit on the short side. Is that inverter working that hard?

I feel some under charging might be the issue.

 

[ghostwriter66]

I guess the first thing i would rule out is the batteries ... it sounds like one may have collapsed and although will take a charge - will not hold the charge ... and then it brings all the others down with it ...

JUST FYI but for about 30 on Amazon you can get a real good DVM with AC/DC AMP reader ... i have found working with solar that my AMP meter is used more than voltage ...

 

[John Frum]

I'm thinking the power is back feeding to the panels, I can't find any other power drain of significance.
Ideas or perhaps a solution, tests, anything!

This hypothesis can be tested by isolating the solar charge controller from the system.
BTW I've never heard of this happening and can't imagine how it would but its easy to rule out.

 

[Silentpower]

I guess the first thing i would rule out is the batteries ... it sounds like one may have collapsed and although will take a charge - will not hold the charge ... and then it brings all the others down with it ...

JUST FYI but for about 30 on Amazon you can get a real good DVM with AC/DC AMP reader ... i have found working with solar that my AMP meter is used more than voltage ...

A battery capacity test would be useful

 

[tmanpdx]

I'm going to write the same thing I've written for others who have this issues, but you need to look at your fridge for a manual defrost button - if this has been turned on, you are sucking down 1000 watts all the time. It will drain your batteries very quickly. I had this problem and it was an ah-ha moment, so I'm figuring if it can happen to me, it can happen to anyone.

My switch was embedded in the frame and only visible when you opened the freezer door.

If this is not the case, then as others state, get monitoring on the fridge stat.

 

[Ghof]

I feel some under charging might be the issue.

We just drove 400 miles today charging at 14.2v volts are 12.8 with the fridge off 11.4 when I turn the fridge back on

 

[gnubie]

12.8v under charge, with no load(?), says battery is a long way from charged.

 

[Ghof]

I think this is the

I'm going to write the same thing I've written for others who have this issues, but you need to look at your fridge for a manual defrost button - if this has been turned on, you are sucking down 1000 watts all the time. It will drain your batteries very quickly. I had this problem and it was an ah-ha moment, so I'm figuring if it can happen to me, it can happen to anyone.

My switch was embedded in the frame and only visible when you opened the freezer door.

If this is not the case, then as others state, get monitoring on the fridge stat.

I think you likely hit the nail on the head I have been running the fridge at MAXIMUM COLD

 

[Ghof]

12.8v under charge, with no load(?), says battery is a long way from charged.

I'll have to run it tomorrow for 400 miles at 14.2 with the fridge set lower without the frost-free mode. My solar will put the batteries into float 13.8 and hold it , with the fridge on max cold and lights on, radio on. Phone chargers and ryobi charger too. And a half dozen leds.

 

[ghostwriter66]

I'll have to run it tomorrow for 400 miles at 14.2 with the fridge set lower without the frost-free mode. My solar will put the batteries into float 13.8 and hold it , with the fridge on max cold and lights on, radio on. Phone chargers and ryobi charger too. And a half dozen leds.

Something is still not right ... you need to find the solution and not guess at the answer ... there is a combination of concerns:

1. Have you ever put like 14.4 volts on your batteries -- got them up to 100% .. and then tested them ??
2. You keep saying "driving" -- are you relying on a little trickle charge from your vehicle to charge the house batteries ?? OR do you have the vehicle properly set up to charge while driving ?? (ie DC to DC converter)
3. Do not confuse DEFROST (which is a heat strip around the doors) with setting it on coldest ... your temp setting will have very little affect on the overall wattage use...
4. You need to get yourself an amp meter -- disconnect the SCC from the Batteries -- and see what kind of draw you are getting .... Until you do that you won't know if you have a Bad battery or a short or a monster appliance drain ...

 

[kevfab]

I guess the first thing i would rule out is the batteries ... it sounds like one may have collapsed and although will take a charge - will not hold the charge ... and then it brings all the others down with it ...

JUST FYI but for about 30 on Amazon you can get a real good DVM with AC/DC AMP reader ... i have found working with solar that my AMP meter is used more than voltage ...

Do you have a recommendation for a “real good DVM with AC/DC AMP reader”? What do you use? Thanks in advance!