Batteries not charging

mike01

Hi there....first post here, and I need some help.

I have a remote cabin in the mountains, and have had a solar system for a few years now. The cabin is only accessible in the summer. This system has worked fine for the last few years, and was working fine when we left last fall.

I have a Trace DR2424 inverter, Trace C-40 charge controller, and Trace TM 500 meter.

The system charges fine when hooked to a generator, and while charging, the TM 500 reads positive charge in the amps function.

However, with the panels in full sun, and the batteries down to 80% or so, the TM 500 does not read any positive charge in the amps function. And, of course, the batteries never charge without the generator running now.

Using a DVM, I have good voltage at the PV connection lug inside the C-40. With all of the disconnects in the "on" position, I also get good voltage at the battery connection lug in the C-40.

This system worked fine for years, and I am at a loss to figure out what happened over the winter. Any help would surely be appreciated.

mike

icarus

Re: Batteries not charging

What is your battery configuration? Have you checked the SG of the batteries?

I would first use a clamp on ammeter to check the current from each panel, as well as the final home run to the controller. Strt with the simple first and go to the complex.

Good luck and keep in touch.

Tony

PS. Welcome to the forum. Please also post your panel config as well.

T

mike01

Re: Batteries not charging

Thanks Tony.

I have 10 AGM batteries. No way to check SG.

I only have two solar panels, and they are of different wattage, wired in series. Worked fine last year though.

Also, sitting here at home, I am now wondering about which side of the shunt the negative wire from the charge controller needs to be hooked to in order to read charge amps on the meter. I would think it goes to the battery side of the shunt, correct?

Also, I don't have a dc ammeter....and would rather not buy one if we can figure this out without one. That might narrow my problem down to either the panels or charge controller, right?

mike

icarus

Re: Batteries not charging

Just a note, Sears sells a relly nice digital clamp on ammeter/volt/ohmmeter. For about $60 Almost. Must have for solar installations.

Tony

Cariboocoot

Re: Batteries not charging

10 AGM batteries and two solar panels.

Sounds like a classic case of chronic deficit charging. It works (or seems to) until the not-quite-enough power from panels fails to stave off the ever-decreasing capacity of a too-large battery bank.

icarus

Re: Batteries not charging

Can you by pass the controller, and still use the meter? It sounds like the controller is having an issue. I am not real familiar with the C-40, does it have indicator LEDs, and what do they say if so?

What was the at rest voltage of the battery bank when you returned after the winter? Are they accepting a full charge from the genny?

tony

PS ten batteries, wired how? As Marc suggests too much battery not enough panel, plus ten batteries in either simple parallel or series/parallel config is a recipe for trouble.

T

Cariboocoot

Re: Batteries not charging

10 batteries on a 24 Volt system is likely five parallel strings of two 12 Volt.

Five parallel strings is bad; highly unlikely the current flow will be even through all.

It is also likely to be in the 500 Amp hour neighbourhood, so a C40 would be maxed out trying to keep it charged. It would need roughly 1000 Watts of panel to do so, and that won't come from two mismatched PV's.

So left on its own over the Winter it has been up to luck to keep ahead of the self-discharge rate even on AGM's, and now after the years the luck has run out.

Just guessing, of course. But logically that would be the situation here based on the information available.

mike01

Re: Batteries not charging

Boy....lots of good ideas here.

The batteries charge up fine with the generator, so I assume they are fine.

The batteries are 12 volt. Two each are wired in series, and then to a bus bar to tie them all together.

I understand, lots of batteries for the two wimpy solar panels. But the meter should still read a positive charge with sun on the panels.

The C40 does have an indicator light that flashes to indicate state of charge....and I don't remember what it was saying.....I will check that though.

I too suspect the charge controller, but I want to confirm that before buying a new one.

Somebody said to bypass the controller. So.....take the wires from the panels, and hook directly to the pos and neg battery connections in the DC250 disconnect box? Then see if the meter reads charge?

icarus

Re: Batteries not charging

Ten parallel batteries wired for 12 vdc? Ouch! Trouble from the get go. As 'Coot suggests, other problems not with standing, you got way to many panels and not any where near enough PV. Assuming say 75 ah per battery, that makes 750 ah of battery, which would need a minimum change curent of ~75 amps! Assuming 200 watt panels, 400 watts of PV might, might on a perfect day put out ~25 amps,, enough for float over the winter but way to little to use.


(edit, I just noticed you 24 vt, so the charge current needs to be ~40 amps, but the charging from the PV at 24 would be closer to 12-15.
Tony

Ps. How are you determining that the " batteries are fine" because they charge fine on the genny? Even a nearly dead battery will charge quickly to full voltage, but it won't sustain a load. I think you need to test ech and every battery to see. How they are really good.

t

inetdog

Re: Batteries not charging

icarus wrote: »

Ten parallel batteries wired for 12 vdc?

Nope. Ten batteries in five two battery strings for 24 volts. Not quite as bad, but not good.

And regardless of the state of the batteries, there should be some charge coming from the CC and solar. So at least one problem there.
Either no output current from the panels (but "Using a DVM, I have good voltage at the PV connection lug inside the C-40.") or else a defective CC.

mike01

Re: Batteries not charging

No, there are 10 - 12v batteries. The system is 24v, so two batteries are wired in series, and then hooked to the buss bar.

If the wires connecting these batteries to the buss bar are of equal length, they all should see the same charging voltage, I think.

And...you are right....just because the batteries charge up with the genny doesn't necessarily mean they are good. I will do a load test.

All of this is beside the point though....why won't my meter read positive with panels in full sun? Can I bypass the controller like I suggested below?

icarus

Re: Batteries not charging

I got interrupted in my edit,, sorry for the confusion.

T

icarus

Re: Batteries not charging

Voltge is only one element,, you need to determine if thee is any current,, hence the suggestion for the clamp on ammeter.

T

Photowhit

Re: Batteries not charging

mike01 wrote: »

I only have two solar panels, and they are of different wattage, wired in series. Worked fine last year though.

So how mismatched are these? 2 panels in series will basicly work at the amperage of the smaller panel. If you don't know the wattage, do you know the type of panels and the square footage?

Have you checked, even with a throw away meter that you have current coming out of the panels, did a squirrel runn across the back and disconnect the 2?

Volvo Farmer

Re: Batteries not charging

Is the TM500 like a Trimetric? I wonder if the instantaneous loads at your cabin are exceeding the rating of your solar panels. Hence, no charging.

mike01

Re: Batteries not charging

When looking for amperage on the meter, I had the main breaker to the cabin off, so it did not have any instantaneous loads.

First thing I can do for free is to bypass the controller. If it still does not show a charge, my problem will be at the panels. If it does charge, then it is the controller.

And....I will start looking for a clamp on DC ammeter.

Thanks for all the help. I will let you guys know what I find out.

mike

Cariboocoot

Re: Batteries not charging

To bypass the charge controller you simply bypass the charge controller: (+) and (-) from the panels move to (+) and (-) from the controller (its output). That way any current from the panels will go through the meter and be registered.

Here's a question: has the meter ever registered current from the panels? And if you're not looking at current but only Voltage it becomes irrelevant.

We really do need more details here to help you out. The panel and battery specifications are very important to understanding how and even if it should function. It is entirely possible that the panels produce so little current that it is not noticeable but has been enough to keep self-discharge at bay. Or something could have gone wrong with a panel connection over the winter and they are now producing nothing. By the same token, a generator can push a lot more current through the inverter charger and even dead batteries will appear to charge but the panels would have no effect. And those dead batteries may read close to proper Voltage but now have the capacity of 'D' cells due to 'aging'.

Depending on what the output of the panels is supposed to be, an ordinary DMM may be used to bypass the charge controller and check for current (if under 10 Amps, the usual limit for multimeters).

mike01

Re: Batteries not charging

Ok....the batteries are 134 AH AGMs.

The led on the charge controller that indicates state of charge is not lit....even though the voltage on the battery bank is good. I know....gotta do a load tst on batts.

One solar panel is 115w, 6.7a, 21.8voc. The other panel is 120w, 7.12a, 21voc.

I have borrowed a DC clamp on ammeter. Next weekend I will go up and check things out. As the system sits right now, I expect zero current flow from the panels.

I will bypass the controller, and then, if I get current flow, the controller is bad. If not, it is the panels....right?

mike

Cariboocoot

Re: Batteries not charging

mike01 wrote: »

Ok....the batteries are 134 AH AGMs.

The led on the charge controller that indicates state of charge is not lit....even though the voltage on the battery bank is good. I know....gotta do a load tst on batts.

That's 134 Amp hours * 5 = 670 Amp hours. Good size battery bank. Needs about 2kW of panel to charge.
Even if the Voltage reads good (25.5) the batteries can still be bad.

One solar panel is 115w, 6.7a, 21.8voc. The other panel is 120w, 7.12a, 21voc.

What you have there is an array capable of probably 35 Vmp @ 6.7 Imp or 234 Watts. At any rate, it's a PWM controller so the most current you'd see would be 6.7 Amps: 1% of the battery bank capacity.

I have borrowed a DC clamp on ammeter. Next weekend I will go up and check things out. As the system sits right now, I expect zero current flow from the panels.

I will bypass the controller, and then, if I get current flow, the controller is bad. If not, it is the panels....right?

mike

Yup. Aside from all else that's out of whack, that is.
You can test the panels Isc individually to; short the outputs of each one and see what current reading you get in full sun. It won't be perfect, but it will tell you if one of them has failed (which would drop output to zero).

Dennis

Re: Batteries not charging

Hello, I am very new to solar but if his cc neg cable is attached on the battery side of the shunt would his meter
be able to see if it is charging? He seems to be using his meter to decide if his solar is charging.
Dennis

Cariboocoot

Re: Batteries not charging

Dennis wrote: »

Hello, I am very new to solar but if his cc neg cable is attached on the battery side of the shunt would his meter
be able to see if it is charging? He seems to be using his meter to decide if his solar is charging.
Dennis

Welcome to the forum, Dennis.

I don't recall anything in the thread regarding the wiring specifics but yes; if the meter uses a shunt (like most battery monitors) and the charge controller is attached to the battery directly (both positive and negative) instead of on the metered side the current from the controller would bypass the shunt and not be detected by the meter.

In fact I did ask if the meter had ever registered current from the panels.

CATraveler

Re: Batteries not charging

Any load or charging source connected to the negative battery terminal would bypass the shunt. Normally all loads and charging sources are attached to the shunt side away from the negative battery terminal and the shunt then can measure the total current into and out of the battery. This current is then the sum of both the charging and load sources. For example if the charging is 20A and the load is -5A then the battery receives 15A as 5A of the charging source is diverted to the load.

I believe the OP said all loads were disconnected. Disconnected vs off can be important. My Magnum ME2012 draws 0.25A idle current when off. Magnum has confirmed that there is no way to turn off this idle current. That's 180AH/month when the RV is in storage.

Dennis

Re: Batteries not charging

Re: Batteries not charging

Thanks Tony.

I have 10 AGM batteries. No way to check SG.

I only have two solar panels, and they are of different wattage, wired in series. Worked fine last year though.

Also, sitting here at home, I am now wondering about which side of the shunt the negative wire from the charge controller needs to be hooked to in order to read charge amps on the meter. I would think it goes to the battery side of the shunt, correct?

This is from one of the first posts.
Dennis

Cariboocoot

Re: Batteries not charging

Good catch, Dennis.

You're absolutely right that the meter's negative should not be on the battery side of the shunt.

mike01

Re: Batteries not charging

I agree....good catch Dennis.

When I wrote that, I had it backwards. In reality though, the cc is not connected to the battery side of the shunt.

mike

mike01

Re: Batteries not charging

Was up at the cabin today, and did some testing. I completely disconnected the two wires coming from the solar panel to the charge controller, and hooked the hot wire to the positive cable going to the batteries and the negative wire to the none battery side of the shunt.

The meter in the house read a charge rate of point 1. The clamp on ammeter also read a charge rate of point 1. The voltage coming from the panels was about 37.

Looks to me like the panels are bad....they are putting out voltage, but no amps.

Any suggestions on where I can find a couple of reasonably priced panels?

Cariboocoot

Re: Batteries not charging

Our host Northern Arizona Wind and Sun is a pretty good starting point for panel prices: http://www.solar-electric.com/hiposopa.html

Whereas you definitely need some panel, don't discount the ones you have yet. You should check the short circuit current (Isc) from them first (+ and - output of panel connected through Amp meter, nothing else connected) to see if they are really bad and to see of maybe there might be something else wrong.

icarus

Re: Batteries not charging

I would suggest looking carefully at the wiring before assuming the panels are dead. UN wire all the panels and check each, and consider if there are diodes that may have failed.

Tony