Charge controller settings

**Sunking** · 12-05-2016, 03:54 PM

OK first thing you have to learn is throw away the battery manufactures specs and recommendations. Also forget about Absorb times. With Solar all that means absolutely nothing and is worthless waste of time. The reason is very simple. solar is not capable of fully charging your batteries unless you system panel wattage is significantly larger than required or infrequently used. Even if properly sized wil not work in winter months

The reason is simple Crown and Midnite Solar are using recommendations made for AC Chargers that at not power and time limited, or correctly sized panel wattages. There is not enough sun hours in a day for you to complete a full charge cycles. Thus your batteries will always be undercharged. Which is a good thing for the manufacture because that means more frequent battery replacement. Example Absorb and EQ are NOT timed events. Absorb can take 6 to 12 hours or long after dark. Absorb is a charge current event, meaning Absorb ends when charge current tapers down to C/33 or 3% of C. Has nothing to do with time. Equalize can take 12 to 24 hours. You apply EQ until all the cells have the same Specific Gravity. No solar system is capable of doing that and thus why you must have a Generator with a Charger to do weekly charges and monthly EQ charges when needed.

You can also get rid of the refractometers. You are not making wine or maple syrup. You want a good $10 Temperature Compensated Battery Hydrometer as that is what you use to find the right Voltage. You need to eliminate the Stages in your controller by setting Bulk, Absorb, and Float all to the same voltage. What voltage you use you have to find with the hydrometer.

Example start with 30 volts, at th eend of the day measure the Specific Gravity. Most likely it will be low. Turn up the Voltage and repeat next day. Keep doing that until 1 of two things happen.

1. Most likely you will not find a voltage high enough. That means once a week fully charge the batteries with your generator until the Hydrometer tells you the batteries are fully charged up.

2. Since yours is part time use you might find a voltage high enough. If that happens you EQ the Batteries only when the Hydrometer says they need EQ charged. Never Ever EQ batteries unless it is necessary because EQ is a controlled Over charge which causes damage in the form of corrosion..

So do not worry about what midnite solar and crown tells you, just ignore their recommendations because they assume your system is adequately sized to do the job when in fact only 1% or less DIY and professional off grid solar systems are sized correctly. If it were you woul dhave most likely done somethihg else. Turn off auto EQ. So get yourself a $5 Battery Hydrometer, a 4 Kw generator, and 24 volt 100 Amp charger and you will be good to go. Otherwise you will have to replace your batteries frequently.

If you are gone weeks at a time you may very well be able to set Bulk/Absorb to 30 and Float to 27.2 volts. But do not count on it. USE the Hydrometer as it is the only way to determine your battery SOC. Voltage does not tell you anything. The Hydrometer will tell you the correct voltages to use.

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**Diesel Pro** · 12-05-2016, 05:19 PM

I have 2 different Honda inverter generators. I have a EU 2000i and a EU6500i. The 2000 is far more convenient of course, but I can't run through the Magnum inverter as it is only 120v. Can a guy get away with a smaller charger so that the 2000w generator can run it?

On a possible related note I have a question about the microwave clock. The microwave is a nice Panasonic inverter type, but clock does not hold time. It may be factory defective, but I'm wondering if these devices somehow synch to the 60hz? It seems to lose 1-2 minutes per day more or less. I do also know that I was abusive to it in the past running the little Honda on eco throttle and causing a brown out start. When on generator power it was never run long enough to watch time.

**John Galt 1** · 12-05-2016, 06:29 PM

As someone who actually does run off grid and uses Crown L-16 batteries I can say that much of what Sunking says is correct but a few thoughts. First off with the size of your panel array vs your battery bank and assuming you avoid taking the batteries below 60% SOC (state of charge) very often you've got plenty of panels to keep those batteries well charged. After factoring in a .77 derail rate (loss of charging efficiency from less than perfect sun on the panels, charge controller losses, and battery resistance to charging) you've got enough panels to charge at a C/10 rate which is right in the sweet spot (assuming the panels are aimed correctly with no shade most of the day).

As Sunking mentioned the only way to really know the correct absorb voltage and time is by using a hydrometer occasionally. In my experience with Crown batteries after they are 6 months old you will need to bump the voltage up another 1 to 1 1/2 volts to get your batteries close to fully charged. Since you will not be cycling the batteries daily I would bump the bulk voltage up about 1v higher than the absorb voltage to help keep the electrolyte stirred. It can be very hard to keep the batteries at 100% SOC even on days when you don't use them using solar but adjust the absorb voltage and time to try to keep the SG (specific gravity) over 1.265 at the end of the absorb cycle. A Crown tech guy and I have discussed this at length and that is what he strongly recommended..

Since you will be gone for weeks at a time be sure that your controller doesn't start a charge cycle every day, I'd suggest a recharge voltage around 50.5 or about 90% resting SOC. This is something I'm just using common sense about since I cycle my batteries daily. But it makes sence not to go into a 3 hr absorb every day with a fully charged battery. I'd also consider setting your absorb cutoff at about 6 amps ( 1.5% battery bank size) (I believe the Classic 150 has both a absorb time and amp draw cutoff) along with the timed cutoff. Using both allows you to use a longer absorb time without risking constantly overcharging when you're gone for a week because a 3 hr absorb on a fully charged battery can result in overcharging.

There are a lot of opinions on equalizing but it is generally agreed that it's best to only equalize if the SG varies more than .15 between cells although I'm generally satisfied if the cells stay within .20.. If you are looking for a low maintance way to keep the batteries up a automatic monthly 1 hr EQ can be a good choice but you still want to occasionally use the SG meter to double check if you need a longer EQ. Never EQ for more than about 4 hours as all EQs put strain on the battery plates and super long equalizing can do more harm than good

I would suggest that the LED tv draws more than 1 watt when off, probably more like 15 watts. Assuming you've got the battery box vent fan wired to some sort of AUX on your controller effectively uses no battery power since it's only running when the batteries are actively being charged..

Just be sure to check SGs regularly when at the cabin. We've all got preferences for SG meters but I like the Hydrovolt because it automatically compensates for temperature but,,, you must rinse it out well after a testing session or after a while it will begin to stick as it rotates the dial.

**Sunking** · 12-05-2016, 09:22 PM

Originally posted by Diesel Pro

On a possible related note I have a question about the microwave clock. The microwave is a nice Panasonic inverter type, but clock does not hold time. It may be factory defective, but I'm wondering if these devices somehow synch to the 60hz? .

It can be done two ways. One with a Microcontroller and Super Cap to keep the RTC running when power goes out. Does you clock keep time when power is out?

If you answered no then it likely uses the 60Hz signal from the Grid which is very stable, but not on a genny. Your off-grid so not sure what time really means to you. It is either light or dark.

**Sunking** · 12-05-2016, 09:32 PM

Originally posted by John Galt 1

Since you will be gone for weeks at a time be sure that your controller doesn't start a charge cycle every day, I'd suggest a recharge voltage around 50.5 or about 90% resting SOC. This is something I'm just using common sense about since I cycle my batteries daily. But it makes sence not to go into a 3 hr absorb every day with a fully charged battery. I'd also consider setting your absorb cutoff at about 6 amps ( 1.5% battery bank size) (I believe the Classic 150 has both a absorb time and amp draw cutoff) along with the timed cutoff. Using both allows you to use a longer absorb time without risking constantly overcharging when you're gone for a week because a 3 hr absorb on a fully charged battery can result in overcharging..

If part time use, he should not use 3-Stage Charging as that is hard on batteries. Just Float Charge them which means 1 voltage of roughly 27.2 volts, or whatever voltage your hydrometer days is 100%. Should be around 27.2 volts +/- 0.2 volts. Float charge is Minimum Stress on the batteries. Float just takes longer which should not be an issue with a part time system. All you have to do is set Bulk = Absorb = Float = 27.2 volts. It changes your charger from multi-stage, to single stage CC/CV mode what utilities use for plant batteries and longest life.

Another mistake most all users make is your job is never done changing voltages. There is no such thing as set it and forget it. It is a daily chore of monitoring and making adjustment. In summer you usually lower the voltages, and winter months raise the voltages. Also disable Temp Comp in your Controler. It has no use in Solar and can do more damage than it prevents.

**Mike90250** · 12-06-2016, 03:27 AM

Inverters never run 60.000Hz. So all the clocks on one system will be slow, move the clock to a neighbors system, it might run fast
And yes the microwave clock uses powerline as reference,

**Diesel Pro** · 12-06-2016, 01:39 PM

First sun in a week and a half!

Checked Sunday and voltage was a weak 23.7v and panels barely pushing 200 watts. This voltage is at or maybe a bit lower than it was a week earlier when I left which is cause for concern. Previously it would run in the 25.6 range. I did watch it run a 1hr EQ and also saw it running at absorb and kept the absorb going to a relatively low amperage, but I did not make notes so on a good sunny day does well.

My battery fan is tiny 1.10watt .09a Gryphon. It is wired directly to only one battery. I know this is not optimal, but figured that the load is quite insignificant.

Good to know on the microwave clock. I have the microwave unplugged this week. The clock is handy if a guy wakes up in the night etc, but if it's not accurate I may have to do something about it. I was hoping that the Magnum would tell me what the inverter out watts were like my killawatt, but apparently not. Even the DC monitor shows amps and that sits at 0 when at rest. I have not set the search watts and not sure if I want to. Seems that if I do it clicks in and out which is plenty annoying so I disabled search.

**Sunking** · 12-06-2016, 03:38 PM

I think you might be over looking something leading you to the wrong conclusions. You cannot charge a battery that is charged assuming your charger is operating correctly. Example let's say your battery is fully charged at the end of the day. Your only load is that tiny fan. It does not matter if you have a 2000 watt panel and 80 amp controller with a 24 volt battery, the next day you wil only see a few amps of charge current for a few minutes. That battery will not take full current until it is discharged 10 to 20%. Contrary to what many think, a battery self limits the charge current. The only time your charger limits charge current is when the battery demands more than the controller can supply it. Something has to give. Right now you do not know what that something is.

Here is a simple test question you should be able to answer if you read the two Stickies I pointed you two. Assume we have a 24 volt 430 AH battery that has been discharged 50% and Open Circuit Voltage (OCV) )reads 24.2 volts. The battery has an Internal Resistance = .01 ohms. We connect a 60 amp charger set to 28.4 volts. What is the voltage and current of the Charger?

Your answer should be 24.8 volts @ 60 amps. In this example the current is probable what you expected, 60 amps. But why is the voltage only 24.8 volts when you set it to 28.4 volts. Where are the missing 3.6 volts? It is not missing at all. It is working exactly how it should be working. What is happening is what you do not understand, how a battery charges up..

The clue (answer) I gave you to solve the problem lies in the Battery OCV and Internal Resistance of .01 Ohms with 60 amps of current flowing through it.

Voltage = Current x Resistance. 60 amps x .01 = 0.6 volts. So we have a battery with an OCV = 24,2 volts + (60 amps x .01 Ohms) = 24.8 volts. To make that battery go from 24.2 to 28.4 volts would require the charger to be able to supply 3.6 volts / .01 Ohms = 360 Amps. You charger can only supply 60 amps and in order to do that the charger has to FOLD THE VOLTAGE back 24.8 volts.

As the battery charges, the battery OCV voltage is rising over time until the battery OCV reaches 27.8 volts. At that point the current starts to taper off toward 0 amps. When the charge current drops to 0 amps, both the Charger and Battery Voltage will = 28.4 volts. FWIW what I just described is the Absorb and Float Mode. a slow process not measured in time, but current.

So now go back and read the two tutorials and you should start connecting the dots. So get a good hydrometer and it will tell you what to set your voltage to. The manufacture recommendations are just that, recommendations. It may or not work, if not you have to do something else.

Bottom line here here is 99% of all Off-Grid Systems are grossly undersized which leaves your batteries Chronically Undercharged and there is no fast way to destroy a good battery leaving it undercharged. With lead acid batteries the second you go from 100% fully charged to 99% fully charged the damage starts.So when your batteries do not live up to claims, you know why, you screwed up and abused them with Solar. They are not compatible.

**Diesel Pro** · 12-06-2016, 03:43 PM

You know I just had a thought. I'm leaving the Inverter on and idling for a week or more of non use. During this time it is consuming standby current plus feeding the vampires. The cabin does not require electricity when unoccupied. The heater is non electric so I could easily switch the inverter off while gone.

Now the question is would this benefit or not? I would think that my standby loss is quite minimal and the little bit of heat generated helps with the LP consumption.

So do I A) Switch off the main and shut off vampires B) switch off inverter completely C) leave it on standby

I would assume that the ME-ARC would retain it's settings if powered down or would I need to redo that every time?

P.S. The sun is all but gone again. Nice while it lasted...

**Sunking** · 12-06-2016, 03:59 PM

OK if you care for your batteries, byu all means turn everything off when you are not there. FWIW the battery fan is not needed.

Anyway if you do that and you should. DO NOT USE 3-STAGE CHARGING. Use Float charging and easily done with your controller. Set Bulk = Absorb = Float = roughly 28.4 volts. Her eis your game plan:

1. Buy a good $10 Temp Compensated Hydrometer
2 Set up controller as described above.
3. Leave for a week, come back, use hydrometer to see where your battery is at. Adjust voltage accordingly.
4. Repeat until you nail the voltage and repeat every visit. What you will find dis a range of about +/- .2 volts.

3-Stage charging is used for daily cycle use to speed the charging process up, but has a consequence, it is hard on the battery and shortens cycle and calendar life. Ball is in your court. You have no use for 3-stage charging in your application. Float Charging is the kindest and most gentle way to charge a Lead Acid Battery.

**Diesel Pro** · 12-06-2016, 04:16 PM

Hydrometer on the way. I like the look of the Hydrovolt that John Galt mentioned and I needed some Midnite/Heyco strain reliefs ($4 not worth ordering alone) so I ordered both together.

I know that I found Abs, Float, and EQ voltages in the 150, but not sure where Bulk is located.

Do I let it run a 1hr EQ every 30 days at 31v just to stir things up a bit?

At one point John Galt mentioned 50.5. Assuming this is a slip up crossing 24v and 48v systems?

**Sunking** · 12-06-2016, 06:11 PM

No only EQ when your hydrometer says it needs EQ. Bare in mind EQ is a controlled over charge, and does damage in the form of corrosion and drinks a lot of water. What you want to stay on top of is SOC and using the genny when necessary to get them to 100%.

With your part time use, and a correct charging strategy applicable to your use, being undercharged should not be an issue, and if you use Float Charging over charged is eliminated. If you float charge, you have no need for those fans as your batteries will never gas, at least not enough to make a good stinky fart you would be proud of. You know rotten eggs with beer kind of stink. In order for batteries to gas requires them to be at or above Gassing Voltage of roughly 2.4 vpc or 28.8 volts. You wil never be at 28.8 volts if you Float Charge at 27.0 to 27.4 volts.

I have an older Classic 150 and on that model Bulk and Absorb is the same integer. Set Absorb = Float = 27.x volts, and disable EQ. Monitor Specific Gravity and adjust Float Voltage accordingly.

I cannot Answer or tell you what John meant by 50.5, but that voltage is roughly 100% SOC on an OCV 48 volt battery. 48 volt batteries charge at up to 62 volts and Float Charge at 52 to 54 volts. I think he meant Recharge if the Battery drops below 50.5 volts in a given 24 hour period. That would be a discharged battery condition on a working system. about what you expect to see in the mornings.

**Mike90250** · 12-06-2016, 07:30 PM

Originally posted by Diesel Pro

....I know that I found Abs, Float, and EQ voltages in the 150, but not sure where Bulk is located.....

BULK is the same as Absorb. The charger runs flat out, dumping as many amps as it can. When the battery rises to the the Absorb setting, the battery voltage stabilizes at the desired voltage, and the Absorb timer starts.

The name of the game is to pump amp hours into the batteries to get them charged. Sometimes, that's going to need a higher than normal voltage setting (just a volt or two) to get enough amps in on short winter days. The hydrometer is the best tool, or you can infer from your morning voltage, if you reached a genuine full charge the previous day. A 2 hour Absorb time would be a minimum, unless you are short cycling a huge battery bank, If you can't get a full absorb, you have to raise the voltage up a bit, just 0.2V at a time till you can complete absorb
Inverter idle losses vary, but added over time, and it can be quite a bit.
Here's a chart of my voltage, today, on a cloudy day (do not try to emulate or scale my numbers, they are from a NiFe battery bank)
If I count carefully, I have about 60 min total of absorb time, which is not enough to offset my daily discharge. (another note, my Classic charger does not report it's charge to the Xantrex Combox, so I only have -amps , but the charging can be seen as the voltage rises, sunrise over the trees was about 8am) You can see the 3 fridges cycling on and off !

Absorb 3x cloudy.png

**Bala** · 12-06-2016, 10:22 PM

Running even small items off one battery in a series usually causes problems. If you leave that fan connected you will likely find that battery will not be balanced with the others

Charge controller settings

Charge controller settings

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