C-60 Controller Bulk/Float settings

BajaGringo13 · August 2013

My home is in Baja CA Mexico. I just replaced 6 Trojan L-16's with 8 Deka L-16's. The system is set to 12 volts.
Up top the array is 8 Keyocera 120 watt panels. The current settings on the C60 worked fine for the 6 Trojans. I received a brochure from Deka on their batteries and they want to see 14.55 vdc on bulk and 13.98 on Float. That seems a bit "Hot" to me. On a good sunny day I used to see 57-63 amps coming from the array and was at float by 2pm.
Since the replacement batteries, I've only floated a couple times. The house has been empty for the last 3 weeks and when I arrived the battery voltage was 13.4 and the controller was at one blink. I have a DC amp clamp on meter and that current was the same on both sides of switches and fuses so no loss there. The output of the C60 had the same current going to the batteries.
Shouldn't they be at float after 3 weeks of charge? I'll go into the controller and see where the bulk and float settings are. The proceed.
Any comments???

Thanks

Rick

NorthGuy · August 2013

Re: C-60 Controller Bulk/Float settings

The current must go somewhere, and it cannot go into fully charged batteries. So, they must've been discharged.

I would check the voltage of individual batteries to see if there's a difference and current into individual strings.

Cariboocoot · August 2013

Re: C-60 Controller Bulk/Float settings

Welcome to the forum.

You've got some problems.
To start with, eight L16 Dekas on a 12 Volt system means you have four parallel connections. This runs the risk of current sharing problems unless the wiring is done correctly and kept in good condition.
Then there's the matter of capacity. Four in parallel is going to be 1200+ Amp hours @ 12 Volts, and your peak current is only around 60 Amps which is a meager <5% - not enough to satisfy the charging demands.
14.5 Volts is not unusual at all; Trojan recommends 14.8 for their L16's in fact. A remote battery temperature sensor is a must for this system, but with the multiple strings you may have trouble locating it in a place where it accurately reflects the internal temperature of the batteries.

First thing to do is get a hydrometer and check the specific gravity on each and every battery cell. They will need to be charged fully before they suffer permanent damage. To do this you may have to divide the array into single strings of two and charge each on a separate day to get them all up to maximum.

Even so you will not have enough charging power to keep them up without at least occasionally Bulk charging with a generator and allowing the panels to finish the job. I'm not sure the exact capacity of your new batteries, but more or less you'd be looking a need for about 2kW of panel and two 60 Amp charge controllers to handle it.

Adding more batteries is rarely the solution to a problem, and can only be done if more charging capacity is added along with them. With eight 120 Watt panels you were barely getting enough to charge the three strings of Trojans @ >960 Amp hours.

Photowhit · August 2013

Re: C-60 Controller Bulk/Float settings

BajaGringo13 wrote: »

... the array is 8 Keyocera 120 watt panels.....good sunny day I used to see 57-63 amps coming from the array

First Kyocera(?) KC120watt panels are "rated" at 16.9 VMP and 7.1 amps IMP, even if you were at 40 degrees your 8 panels couldn't make more than 7.1x8 = 56.8 amps and in the heat I suspect your producing a little less than that in amperage and considerably less voltage.

Not sure why you added more batteries if your system was working, I guess you use it on weekends from time to time and your in a sunny area, so you might have been OK with 3 sets. How long did your last battery bank last?

I suspect you could add panels, but right now you should first check your batteries to see that they are all still fairly uniform in state of charge. You could do this by letting them sit for a few hours and see that they have very close to the same voltage individually. Then fully charge your batteries with a different energy source, then equalize them. Then I would suggest removing 1 set from the system.

You should check to see that the combined resistance of the wires running from where they connect into the system is the same, same length and gauge wires. Then setup the C60 for the correct voltage by your battery manufacturer. If you have a fairly long wire run, you may need to increase the wire size from the array to the charge controller and on to the battery bank. your panels are rated at 16.9 vmp and in a lot of heat may drop to 90% of that which will be less than what your saying you need to charge the batteries after much resistance in wires and a small drop in the charge controller.

BajaGringo13 · August 2013

Re: C-60 Controller Bulk/Float settings

The first set of batteries lasted 5 years and I was still working. Used the house for only 5 days at a time 4-5 times a year. I'm retired now hence the additional 2.
I'm down here a month at a time now. I have run the genset which feeds a Xantrex MS2000 which brings the batteries up to float.
All the batteries are now at 6.1 volts.
All 8 panels feed a Combiner and #2 wire from there feeds the C60.
Are you looking for actual resistance in the wire or voltage drop. The run from the Combiner to the controller is less than 30 feet. The batteries are 4 feet away from the controller and are fed by #2 wire also.
I've measured voltage before and after switches and fuses and no drop at all.

Cariboocoot · August 2013

Re: C-60 Controller Bulk/Float settings

It's like this:
You start out with 16.9 Volts maximum power at the panels. Run it through 30 feet of wire, and then ask the question "do you still have enough Voltage left to hit the Absorb level?"

Under full current of 60 Amps (which should be less by the time the batteries near Absorb Voltage) you would need 8 AWG across that 30 feet to keep the Voltage drop down around 2 so that there would still be over 14 Volts available. Ideally it would be 1/0 AWG to reduce V-drop to 3% over that distance.

No, ideally you'd be running the panels as a "24 Volt" array and using an MPPT type controller to down-convert the 'extra' Voltage into charge current and cut the array to controller current in half.

Which does not solve the problem of the array simply not being large enough to produce sufficient current to push that much battery up to Absorb level in a reasonable amount of time.

I suggest you re-evaluate your loads. With 1200+ Amp hours @ 12 Volts you have roughly 3.6 kW hours capacity available @ 25% DOD. But you don't have enough panel to replenish more than about 2.4 kW hours.

You should not run the generator to achieve Float either; that is a lot of fuel going to make a small amount of power. It is a fine way to Bulk up a battery bank when needed, but then you should be able to have the panels take over and finish the job.

Basically your system is unbalanced in terms of load vs. battery vs. panel.

vtmaps · August 2013

Re: C-60 Controller Bulk/Float settings

Cariboocoot wrote: »

To start with, eight L16 Dekas on a 12 Volt system means you have four parallel connections. This runs the risk of current sharing problems unless the wiring is done correctly and kept in good condition.

BajaGringo13 wrote: »

All the batteries are now at 6.1 volts.

As far as the voltage on the batteries, since they are connected in parallel they will have the same voltage. Having the same voltage does NOT mean they will share current equally. Buy an inexpensive DC current clamp meter (about $60 at sears or radio shack) to measure the current in the individual strings. Read about parallel batteries: http://forum.solar-electric.com/showthread.php?14674
Even if the parallel setup is not your problem now (and its probably not), it is something you should be aware of and able to diagnose in the future.

Photowhit wrote: »

your panels are rated at 16.9 vmp and in a lot of heat may drop to 90% of that which will be less than what your saying you need to charge the batteries after much resistance in wires and a small drop in the charge controller.

Cariboocoot wrote: »

Run it through 30 feet of wire, and then ask the question "do you still have enough Voltage left to hit the Absorb level?"

I think that Photowhit and Cariboocoot have hit the nail on the head. When the panels are hot, their voltage may be even less than 90% of their rated voltage. Your 30 ft of #2 cable is causing an additional 0.5 volt drop between the panels and the batteries.

After what you've spent on batteries, the cost of a MPPT controller does not seem so high. If you go that route, just rewire your combiner box so that your panels are configured in 4 parallel strings, each string being two panels in series. That will solve your problems of inadequate voltage reaching the batteries. As mentioned, you could benefit from a few more panels. Your current setup is at the limit for a 60 amp controller. If you add a few more panels you will need a Midnite Classic or an Outback FM80 controller, and even if you don't add more panels you should buy the larger controllers... in a hot climate its never good to run electronics at their maximum limits.

The smartest thing to do (if you can afford it) would be to switch to 24 volt system. Your new batteries could be reconfigured as two parallel strings of 4 batteries per string. The current from the panels, through the controller, through the battery cables, and to the inverter will be cut in half; and the system will be more efficient.

--vtMaps

Cariboocoot · August 2013

Re: C-60 Controller Bulk/Float settings

vtmaps wrote: »

The smartest thing to do (if you can afford it) would be to switch to 24 volt system. Your new batteries could be reconfigured as two parallel strings of 4 batteries per string. The current from the panels, through the controller, through the battery cables, and to the inverter will be cut in half; and the system will be more efficient.

--vtMaps

I think you mean 24 Volt array. If he ups both the array Voltage and the system Voltage he could be right back at inadequate Voltage (16.9 * 2 = 33.8 which is a tad low for a 24 Volt system). Unless once again he ups the array to 2X system nominal and uses an MPPT controller.

A couple of mitigating circumstances he might have based on location: if the elevation is high the panels will receive greater insolation and produce more current, plus they may remain cool enough to keep Voltage drop to a minimum. But that is speculation.

vtmaps · August 2013

Re: C-60 Controller Bulk/Float settings

Cariboocoot wrote: »

I think you mean 24 Volt array.

My first suggestion was to reconfigure as a 24 volt array with MPPT, but remaining with a 12 volt system.

My second suggestion (smarter, but more expensive) was go with a 24 volt system. That would solve the four strings of battery problem. But I didn't go into what controller or array configuration would work with a 24 volt system... he might be able to get away with his C60 because of the reduced voltage drop in the cable.

As you mentioned, he need more panels anyway and he's at the limit of what most controllers can handle at 12 volts. If he adds more panels and stays at 12 volts he will at or near the limits of even a Midnite Classic or Outback FM80.

--vtMaps

C-60 Controller Bulk/Float settings

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