Battery Bank - R x I=V so.....

[hoopty_yo]

So I have about 1200 watts of panels feeding through 4 charge controllers to a small battery bank. I only have 4 golf cart batteries and I think this may be leading to my problem? Some charge controllers are smarter than others, but the incoming voltage is shutting them off. By the time the sky is dim enough for the voltage to drop and trigger the charge controllers, it's too late in the day to get a good charge.

I have (3) 120 watt panels that I can switch between the Wellsee PWM controller (of course, the one with the most adjustments) and a grid-tie. Even pulling these off, the three 145 watt panels on the Sunforce controller shut down. Not sure what the "charge-off" voltage is, but it isn't adjustable.

The BZ MPPT250 shuts down at I think 14.1v. The only one that keeps on cooking is the Phocos PWM, but I have almost no info on it, and it's only good for 8-9 amps tops.

My thought is, since R x I = V (resistance times amps (intensity) = Volts (or E), that more batteries would equal more resistance and therefore lower the voltage enough to maintain charging in a normal fashion.(I wish I had this problem on overcast days.)

I think this is what I witnessed when I got my first HF kit and hooked it to a 7.2 AH battery. Massive voltage fluctuation on the battery.

Am I on the right track here? I know I want two more batteries anyway. 660AH is better.

I just thought of something. Should I unplug one panel from each offending charge controller and see if I get more charge hours per day? - To re-iterate, The charge controllers will often show 14.5 volts throughout the day, settle to 13.1 or so as the sun is going down and stablize at 12.3.

[W.R. Wahlquist]

   Hoopty

   I'm not sure I'm grasping your writings. But, if the controllers are shutting down in mid day sun it would tell me the battery is charged and were done. I use the sunforce controllers on my system and late, very late depending on the time of year they shut down because the batteries are charged. Yesterday about 3 pm they had shut down, other half turned on the TV and it began again charging but only what the TV needed. I never have seen the controllers shut down unless the batteries were charged. The wellsee controller I have looked at but haven't had in hand, the sunforce I have several 60032's on sit working every day and have had no problems with.

   What is the pole voltage on the batteries when it doe's the high sun shut down? are we infact charged?

[hoopty_yo]

The batteries usually show 12.1 to 12.2 range in the morning. That should mean I need to replace around 200 of my 440 amp capacity. A good average would be 30 amps from 3 of the controllers with a max of probably 50 amps. (The panels on the 4th controller are fixed and have some angle/ shading issues - hard to come up with consistent numbers).

A couple days ago, it did get a full charge, but usually falls short. I would expect that if charging all day, but if the controllers are off or in PWM mode most of the day, I would like to see 12.6 volts if not more at 10PM (in August)

My Sunforce is the non-digital model. I can usually switch the (3)x120 watt to grid tie (different controller)and reset the Sunforce (145 x 3) (which shows 50% on the battery LED during test/reset) Sometimes it will charge for a little while, others it will cycle on/off at about 1 second intervals. I've only seen a full charge indicated once during the battery test/reset.

I was going to try some things, but it's raining now! 94 and clear skies yesterday! Welcome to Washington State!

[W.R. Wahlquist]

      Hoopty

   I'm in Minnesota,,been pretty close weather wiss. I'd like to no what the voltage at the battery poles are when charging, should be 14+ when nearing full charge. I'm running 8 145 watt panels against 1160 amp hours of battery. I'm useing about 4 KW on the AC side of the inverter per day.I'll be at full charge about 3 or 3:30 in the after noon, bright sun today!

[hoopty_yo]

Alright, the sun came out and I was able to check some numbers. The battery bank is at 13.3v. The Wellsee charge controller is showing 14.5v which is charge voltage, not battery voltage. I switched it to grid tie and turned off the Phocos controller input. The voltage indicated on the Wellsee was 13.0v. I reset the Sunforce (it was off), and it started running again, putting out 22.5 amps and raising the charge voltage to 14.2v.

What I've come up with is the BZ and Phocos controllers are the only "intelligent" controllers I have. The BZ shows actual battery voltage and the Phocos has a bar graph (25/50/75/100) that seems fairly accurate. It has yet to shut off. Always kickin, but not enough amps. The Sunforce seems to be looking at charge voltage. When I initially reset it (14.5 on Wellsee display)it showed a full charge on the LEDs.

I pushed the reset again to check the battery after it turned on and it lit the 50% LED, which the Phocos display confirmed. 

The BZ has it's own battery feed. The other 3 have their outputs run to a fuse box. The feeds are run to each end of the battery bank. So to summarize, two controllers running, two feeds to batteries right now. Even if I run seperate feeds to the batteries for all controllers, they will still have a common junction point and have a false voltage reading. ??? I like having multiple controllers, because they are all running matched panels.

[hoopty_yo]

I'm totally convinced this Sunforce controller is a joke. I pulled one 145 watt panel off and applied a load to get the voltage low enough to get it to charge. 13.1 seems to be the point where it will reset, but I don't know when it will do it on its own. 12.8 didn't do it.

It may be a fine controller on it's own with a large enough battery bank. With the BZ pushing 9 amps, it keeps the voltage high enough that the Sunforce will not resume charging.

[Dale Marshall]

Well Hoopty. I could've told you they are a joke. If your charging a couple of batts with it. And no other controllers thats fine. The Biggest problem I find in these cheap knock off PWm charges. They will bring your battery to the set 14.4- 14.6 volt and wont it set there for absorb. They usually just bring the batts to the required 14.4 + volts then set to Float at 13.6. Problem is without absorb mode in charging, Your batteries set technically at 80 % charged. And depends on float..Float most of the time wont get ya there. My chargers being MPPT. Most of them have an absorb mode. Which will hold the battery to a set 14.4 + volt and the amps lower slowly coming in according to how far the battery is charges up. Most of the time your battery will reach a 95 % + charge here in this mode, Then it goes to float which can be handled  easy.

[Bill K]

Hoop,

This comment concerns me....and it was mentioned in another part of this discussion as well...

"To re-iterate, The charge controllers will often show 14.5 volts throughout the day, settle to 13.1 or so as the sun is going down and stablize at 12.3"

If you reach a float level of 14.5, and if that float holds thru out the day (say 5 or 6 hours), on the next morning, you should see, at the very least, 12.7 vdc....on days like that here, my bank will show 12.85 or so, in the morning....12.3 is way down from 100% charge, in fact it's below 70%...are you sure you don't have a bad battery (or more) in the bank?

I don't know if this is effecting the controller readings, but it might, those MPPT controllers are smart little buggers..

[Raymond Dias]

I would suggest doing a battery test. After the batteries are fully charge and with no load while charging. When the batteries have been fully charged unhook them from everything and let them sit for a few hours. Take a volt meter and check the voltage of each battery and see what the numbers tell you.

If these are wet cell batteries (not Gel or AGM) then you should check the water level and specific gravity of each cell (watering hole).

For the Specific gravity numbers you might need to look up the manufacturer's specifications. 

I found a bad battery in my bank recently by doing just this. While all the other batteries had voltage readings of 13v+ the bad battery had a reading of 11.8. Going to see if i can recover the battery or just replace it.

As for the voltage in the morning, anything you have on that is connected to the batteries will drain a little bit of juice.

[Denise McCracken]

  All charge controllers going into the same battery bank?  I tried more than one, and didn't like the results.  Maybe they interfere with each other?  It would take a moosy one to handle 1200 watts, but might be worth it.  BTW, I have a Sunforce controller, and it works just fine for me, but it is the only controller.

[hoopty_yo]

I think the controller will probably work fine by itself. I can turn each controller on individually while watching voltage rise until they float. The oldest battery is 4 months I think.  There is about 5 amps drawing usually 24 hours a day and about 9 amps with the TV on. When the incoming amperage raises the voltage enough to put the controllers in float I end up with 2.5-10 amps coming in, which won't charge the batteries from 25%

[hoopty_yo]

UPDATE: No sun today until 5:45 PM Overcast all day. Batteries at 13.1, 13.8v coming in.

I turned off the controllers for a few minutes, but left the inverter on (5 amps) and it dropped to 12.8

Have to see where it stabilizes, but all is showing a full charge so far.

[Big Moe]

Hello Hoopty,

 

I would consider changing to one controller that can handle the load. Or if you would like mutiple controllers I would put each panel type on one controller. So the 145(s) would be on one controller and the HF panels would be on another controller.

 

I run muliple controllers to a single bank, but they are the same brand and model of controller. Once my bank is full one of the units will shut down while the other is absorbing or floating. If the bank is not full both will feed the it until it is charged. But since the controllers are identical they work in unison with each other, no fighting like I think your units are.

 

Just my take on the issue.

 

Moe