DIY Solar Micro Cycling Your Batteries With Dump Load Off The Grid 

Hey, good thinking BUT... Micro-cycling the top most end of your batteries is not the same as deeper discharging, which will obviously affect battery life. And you DO want to connect the dump to your batteries. Your battery plates WILL remain in a state of very high charge and so will not incure degredation. If you take the power direct from your panels, there will not always be enough amps to meaningfully heat the dump as the dump load will not always have sufficient power available to operate as designed, resistance, volts and amps. If your upper and lower set points are suitably close, you take as much power from your panels as is available, and any short fall is taken from batteries. If excess power is still available, ALL power consumed by the dump will be taken directly from the panels via the battery terminal connections and the regulator will maintain the batteries at full capacity, **note**. If sufficient power for dump is not available from pannels, a small amount of power will be taken from the batteries, which will drop the voltage down a little below the lower set point, and the dump will thus turn off until the high set point is turns it on again. you need to experiment with your individual system to arrive at optimum settings and you may need to seasonally adjust these by a small amount to maintain optimum operation due to temperature variations. Now the **note**.... matching you system dynamics: array size, situation, orientation etc; battery capacity; use characteristics; dump capacity and actual dump unit particulars is important. If on an average good day, you might have 400W spare, then a 300W dump will be better than a 600W unit. Sure, you might occasionally lose a little power, but your dump will run at optimum for much longer while taking very little draw from your batteries the majority of the time, and then, only for a very short amount of time at a time. A simple check is when your dump is running at or near capacity, just turn the dump of and note your volt meter and regulator status simultaneously. you should see that your batteries ate at full charge and the regulator is in almost full regulating mode, i.e. only allowing a tiny amount of power from your aray into the bsttery, if any at all. It is never going to be 100% due to hystersis, however, with a little effort, you can get VERY close. I do not have an expensive regulator, just a cheapie cheapie PWM from ebay, and built the dump controller for a couple of pounds using a FET instead of relays. works great (24V system plus 300W 12V immersion heater with 2 150W elements, which were wired in series to convert to 24V). I am not an expert, but have lived 100% solar for 11 years with no backup and all done on an extremely tight budget. My battery bank is much to small, resulting in very high C rates, both charge and discharge, in that time, I have gone through 2 sets of two batteries. Considering how over stressed my system is, I think that the batteries have fared very well under the circumstances, including with the dump opperating from mid february to early november in SW England!! So what I offer here is from personal experience amd I hope it may be of some use to some with respect to issues pertaining to dump loads, or at least add a little additional/alternative perspective to this subject. Good luck and all "power" to you all.

In the TriStar PWM Installation, Operation and Maintenance Manual it does say the energy will come from the source, not from the battery. "As the battery becomes fully charged, the FET switches are closed for longer periods of time to direct more current to the diversion load." "When fully charged, all the source energy will flow into the diversion load if there are no other loads. The generating source is typically a wind or hydro generator."

A super capacitor bank between the charge controller and batteries might help with this... it would primarily cycle the super caps, if the cap pack is big enough

Not sure I am following your logic here. I do no have an Outback, But do have a Midnite Solar Classic 150, and from my extensive experience with this controller it is possible to extremely limit, or possibly completely eliminate what you are calling micro cycling. The Waste Not Hi (aka Diversion Load) setting for the Classic is highly configurable when using the Auto Feature. One can tweak the Delay and Hold settings to keep the Classic from diverting when there are clouds, etc and voltage triggers can be set to not allow any change in battery current flow when the diversion load is on. Example: in full sun when my Lead Acid battery bank is fully charged (according to Specific Gravity and SOC of the Classic) the batteries are in Float and receiving 0.5 to 1.5 amps. If my diversion load kicks in at 720 watts, and solar conditions are right, my battery voltage does not change from 27vFlt, and the float amperage to the battery does not change, holds at 0.5 to 1.5 amps. What changes is the power (Watts) coming in from the array. It changes from 30W+/- to 750W+/- and the amperage coming in from the array goes up over 34amps. The batteries are still receiving the exact same float charge voltage and current. So the array, and not the batteries is providing the diversion. And this can be tweaked in the Classic to turn off the diversion if any thing changes before any charge is lost from the battery bank. While I understand in your case you are dealing with Li batteries and not floating them, and this may be doing some "micro cycling" , but the cycling would not necessarily be true in all cases in all battery types, and could possibly be massively compensated for in Li chemistries as well with proper tuning of the Classic settings.

yes ive never liked dumping from batteries, the same thing crossed my mind years ago ,you could have a small lead acid slave battery bank which could power loads with the excess solar power.

I agree with you. The current so called divert load isn’t a true divert load system. Believe me or not I was thinking about this for many years. Like why do I have to discharge the battery to maintain a certain voltage. I was just waiting for someone to develop a REAL divert load system. Hey maybe you could patent this and sell your version of a divert load system.

Subscribed and waiting for an answer purely to/because-of this video. If you wire up a dump load on the solar side, totally want to see how that is configured. I've always questioned this methodology micro cycling the bank and would love to see an easy workaround and seems possible in theory.

great insights man! Thanx for your vids over the years... I finally got my first 400w turbine a few months ago (to complement my old 55watt coleman panels been hanging off my garage and charging a battery for 3 years very very slowly , lolol ) and having a great time with it. The second day the turbine was up had 35 mph and more winds, and the pole bent! I straightened and lowered it a bit, and a week later we had another whole day of similar wind. On that day I brought in 1.2kw... but that was on the dc side shunt read out. Now the power goes into charge the battery (loss), then wait (loss), then get sucked at a terrible loss thru the inverter, and worse the inverter is usually on (loss). All these questions and more are arising fast with my first little system. Totally agree with your video here. Your battery getting cycled (loss), your inverter working at a loss (loss), and those two losses are doubled when the whole time pure excess dc load could raise water or heat it, or chill water or freeze it, or compress air ...

Exactly! I finally found a video that finally discussed this. I plan on using a digital voltage comparator and 2 ssrs. I have 6 strings of 2 x 370w solar panels in series with a morningstar 60A pwm charge controller. I am using chevy volt batteries. The digital voltage comparator will be sensing the battery voltage. If battery is bellow 50V close relay that connects one string to the combiner box bus bar and open the relay to hot water element. If battery is above 50V, open relay that connects solar string to combiner box and open relay that connects to hot water element. That way I can control how much solar I dedicate to my charge controller, not touch my batteries or inverter.

You are right in that the system does micro cycle. The problem you will have in running direct from solar is that you lose the MPPT and so if dump load exceeds solar at any time the solar voltage will collapse until the dump load takes whatever current the panel will produce. As watts is Volts x amps and the volts have reduced then so has the power. I tackled this with a current sensor on a main battery lead which backs the dumping off when the battery current approaches zero. The result is that the voltage varies between float and dump level but no current leaves the batteries. If you put on a house load this is sensed and dumping also stopped immediately so the solar can power the load. I have graphs of both methods. The next aim is to use a PID method to predict battery voltage behaviour and smooth out the voltage swings that occur because battery voltage when not under load and fully charged moves down very slowly from absorb level but moves upwards very fast when a bit of current goes in. Super caps could possibly help here.

Thank you, so many channels are promoting this method and don't understand that you're micro cycling your batteries.

Did you ever re-wire your system to the solar side? I'd love to see your "after". Thanks!

Very interesting!!! The longevity of lithium batteries is reduced by that last push of capacity... The 90% to 100%. Micro cycling at the top end should be avoided. I'm working on a diversion load controller that avoids this and several other problems.

just like my ongoing micro hydro turnbine, i use solid state relay as dumpload switch instead of thyristor.

One of nicest set up around

yes, modern off grid diy, you are probably asking a bit too much. the oscillation thing is a common problem. you can only avoid this by a costly device. but even they can have some oscillation. in the midnite classic you can program the aux relay by the voltage of PV. this might cause less oscillation. my way at looking at this is to put more solar panels up. which gives you added energy, etc and is probably much more cost effective than that expensive dedicated device. lithium batteries in particular are very voltage sensitive, at the same time very stiff. this causes some irregularities in my midnite classics. they really need the have battery voltage sensors and be programmable to 10mV rather than 100mV. midnite classic blokes seem to put their energy into new projects though.

I very much agree. I went to using no dump. Put a switch in to open system. Once batteries are full. The dump load I recieved didn't have a way to adjust when it dumped. It was preset. Which would dump at 12 volt not 13.2v. So it was near useless. @ 11:00 hope you show wire diagram Where do I find the adjustable dumpers?

I have been searching for this video for years

I can see how you've come to this idea, makes sence. My campervan solar system has a 255w 30v solar panel, 110amp lead acid house & 110amp Starter battery charged by a Votronic charge controller with AES system as a dump load . The charge controller needs the 12v or 24v battery to tell it what voltage to convert to so i couldn't disconnect it to issolate the batteries once charged. The charge controller switches the AES on when the batteries are full, it is only a low power signal ment to turn a 3 way fridge to run on 12v instead of gas or grid power but my fridge isn't wired that way. Instead i power a relay to run a small DC dehumidifier as a dump load. I guess i could run a heavier load from this. As you say it does cycle the house battery as it is designed to maintain the load for 30 minutes regardless of the solar input. If the panel gets shaded and the input goes down the battery starts to loose power, when it reaches a certain level of discharge the system switches to recharge mode. What this needs is a solar intensity senser to turn off the relay powering the dump load when the output drops thus saving the battery from discharging.

Okay, in my church my batteries go to bulk at 58.5 volts, so I set my wind controller to dump at 58.70 volts. The same goes for float. The batteries go to float at 54 volts, so my controller on the turbines is set to float at 54.20 volts. I believe that this will solve your problem my good sir. Set your DUMP LOAD to: 0.20 volt over your Bulk, Absolve and Float and you'll be fine.

I had same problem 2 years ago. I did close to what you was saying. I used a battery monitor to control relays on the solar input side and divert the power to a water tank that stores heat, for my night time thermal electric power generating. When the batteries drop to my low setting. It switches power back to the charge controller.

I have a similar system with the same Outback Gear and Solar and Wind power. I use a Pulse Width Modulation (PWM) TAPERING load diversion system that can divert up to 120 amps..IT doesn’t cycle the batteries at all..just diverts extra power from the wind. You can use a Xantrex C60 for Tapering Pulse Width Modulation and Load Diversion…no relays at all needed and lower cost.

That makes a lot of sense I always wondered about that Please share on How you wire it up Inquiring minds want to know

Good discussion point... I have a question about it though. If you divert at the solar side, but still require AC power to the house wouldn't you still be micro-cycling your batteries? The difference is that your inverter would be powering only from the batteries. I thought most inverters plugged into a bus bar would pull power (if available) from the spare power given from the charge controller. Basically, the inverter is looking for DC power, whether it is from the batteries or MPPT is just based on the available power at the time. Also the traditional wired (what the manufacturer tells you) diversion load would work similar as any excess power generated by the panels would be used first before anything from the batteries. Only if you are pulling too much in your diversion load would it do a micro cycle. So the key would be to have something that only uses what is available from the charge controller + inverter draw and not more so there is no effect on the battery.

I thought that is what the load output of the inverter is for?

I think I know what you are trying to say, have your inverter and battery in parallel, this way power goes to the inverter if there is a load and never sees the battery. On my 22kWh LiIon setup when the Midnight Classic is putting out say 50 amps and my inverter is drawing 50 amps to make 240v AC, there zero pull on my batteries. The power comes out of the charge controller and goes directly into the inverter. If your main breaker has been off for months (like mine) you are already charging your batteries from solar every day (micro cycling) and discharging every night (micro cycling). For most of the US, dump loads are completely unnecessary from October to April as you produce 1/3rd less solar due to short days and cloud cover. However from May-Sep its good to have an EV to plug in.

If you size the diversion load to less than output of the solar panels it will not cycle the batteries, but what you are saying is correct also you could just use teckluck board.

very smart/super great /i like the idea/thamks much

I agree and it’s driving me nuts ! I use my batteries all night (250 watt load 24/7 ), in the morning they are about 60% charged then on a good sunny day they charge to 100% by 1:00 pm….then the dance starts. I too have considered hooking a 72 to 12 volt regulator at the output of the panels, then the output of the regulator to a 12 volt pure sin wave, then it’s ac output to a UPS that facilitates voltage sag on a cloudy day. Limitations, the regulator is only 35 amps AND I have 3 independent groups of panel banks. Oddly enough only 1 panel bank needs to be active to handle the 250 watts from 1pm to 4 pm and maintain full battery charge.

All you need to do is match diversion load to excess load. Do they make suck a thing yet? A heating element could be varied easily enough. ...

makes perfect sense to me!

Hi there. Yes, you are correct that there is a "slew rate and slew time" the way that they want you to wire the deversion circuit. When they designed that function lithium batteries weren't popular like they are now a days. My sealed lead acid batteries take a lot of charge time in order for the current to drop in order for the batteries to change to the float condition. My concern is this. If you wire your batteries to unhook from the charge controller during deversion, can the deversion circuitry react quick enough to reconnect the batteries to not produce a spike on the AC out side of the inverters. Yes the solid state relays are fast but is there a delay before the deversion circuit denergizes and hooks back up to the batteries? Just food for thought.

A actionable way to utilize your concept for a reasonable cost would be to use a juntek vat shunt to drive a relay to your load Assuming your load is good for your panel voltage Just set the relay to activate when current is below say 2amps One could trigger relay off or on by voltage aswell ergo at night no voltage = relay off Next how to stop the panels from dropping voltage and run with max efficiency is up to you or, Would run it into direct drive solar inverter with load directly attached to say a heater to boil water or to a freezer Let me know what you think of that

this is what ive been thinking about alot

Thanks for that video I honestly thought your explanation was the way it works

You know i think that there is alot of people getting riped off by this and most of them don't know even know. And i was thinking about the same thing and i was thinking what if you get a grid tie inverter to only use the solar and wind power to pwer the household appliances during the day and save the battery power for the night....... now that would be great for the longevity of the battery life

you are so on top of your game , i am lost for words. you are so , so , so , right. Brother, thkY for this brain storm of BRAIN MASS... VERY important imformation ... WE ARE TALKING ABOUT A LOT OF MONEY HERE WITH BATTERIES AND OTHER STUFF. thank you dan t palm springs ca USA

I like your idea on that, do the dump on a grid tie inverter would work good as well if it is a good length of time

Did you ever make a video of how you fix this and actually showing us?

you're right about the voltage tapering though which is something that's been bothering me lately. I'm not talking about the regular taper that happens during the bulk cycle. What I mean is my Midnite classic seems to be slowly approaching the absorb set point even though there's 5000w available to push the batteries up to the absorb set point. I look at them they're still in bulk or absorb and they're only pulling 400 watts but still haven't made it to the high absorb point that I set. Like it's just slowly approaching it for some reason. Seems like the lithium batteries would be much more of a problem with this micro cycling we're seeing here. Because the lithium's we like to hold them below 100% And we want to hold them steady. Any voltage change represents cycling. However with my flooded lead-acid batteries a full one hundred percent charge voltage is actually under my float set point so my voltage fluctuating near float voltage would barely pull any power in and out of the batteries at all because of the higher resistance of flooded lead-acid batteries compared to lithium's

It isn't actually cycling the batteries. What is happening is that the charge controller is directly connected to your dump load when your batteries are fully charged. What you see as the voltage dropping slightly is the charger not being able to adjust voltage fast enough for the load. Since it knows that it can't raise the voltage due to over charging the batteries it goes on the safe side and ups the amperage causing a sag in voltage but when the amperage is available from solar it's not taking anything from the battery until the load is too much for the solar input

Of course we don't want to be using batteries when solar is still producing power...great video!

Good Idea

Alternatively, you could make sure the dump load is enough to bring the state of charge low enough so that your batteries aren’t charging on the top end.

Can you show us how u actually stop micro cycling you batteries.... I think I’ll get a better understanding

Batteries really are expensive and they take a while to run out, but after 5 years mine were junk and it's such a waste. Now I have to start all over and dont have so much money. And I always use to get too much power. But I am so left brained, I wont be able to figure out how to do what you do. You're a mad genius! I still want to keep learning hat I can though.

I have a L1 charger for my EV at 120volts for dumping. My impression was the incoming solar was used be the load first and excess went to the batteries. Ex 2kw in the car pulls 1400watts then 600watts go to the batteries when fully charged the full solar input go's to load. Am I missing something? Have Outback FP1 with lithium battery bank.

seems logical. Any update?

Cant you hook up a secondary PWM through a capacitor to where the battery out is on the first PWM & use the dump load on the first PWM once the second dump load closes a switch on the first one?

Yes especially I'm running group 31 Optima Batteries those things are very pricey for my wind turbine system for my solar I have lithium ion batteries out of Toyota Highlander

Do you have a wiring diagram , wanting to set this up on my system thanks

Understand how and why NOT to do it, but I wish you would make a video about how to do it your way..it sounds much better!!!

First, love your set up!!! thanks for the vids!! Second, I am currently focusing all my time and efforts in putting a system together. This system u have and the environmental conditions you live in are very similar to my conditions other than i get snow!! What would u do differently? what would u put your money in first??????

That sounds amazing can you please make a diagram?

The only Appliance I could see that would run this load variance would be a heating element, maybe a preheat? you wouldn't want to hook fans or any other brushless system to this just because of the fluctuation in power.

Makes sense, now the heating element rating depends on your solar voltages...or? Or let a water pump pump up on a hill and use micro water turbine at the bottom when u need the power like the big electric companies do.

Hey that's a very important discover you just made maybe I should look into doing something like that on my system

It made sense... if your not you should be a teacher ✌

Why do you need the relays if you aren’t pulling from the batteries? Current follows easiest path, why not just put your load on After the rectifier? When they charge controller blocks the current, it will find the next easiest place to go, the dump.

Did you ever do a follow up video of this. I can see why NOT to do it the way the directions say...but I don’t understand exactly how to DO so it!

I am having terrible trouble with the solar power and the local electric company. They suck my energy up every morning at 3:30am and leave me 0 kw and also spike energy from my system all day then I have to BUY energy from back "Everyday"!!!! I have had solar for a year on one of those 0$ down programs and I still am paying electric company $200+ every month. I have 31 panels and two batteries ...

Or put a cheap pwm or mppt to a second battery bank. Basically run the diversion to the solar input of the mppt charger. Or a light or what ever.

I agree with "Nick Ush, 11 months ago, Hey, good thinking BUT... Micro-cycling the top most end of your batteries is not the same as deeper discharging, which will obviously affect battery life." What actual hard evidence do you have that "micro-cycling the top end of batteries" is bad for batteries, and to what extent? There is sufficient data available to show it is wrong that each micro-cycle is additive to make complete cycles. Indeed that is an assumption on your part which I consider wrong, I just don't know how wrong it is. Time using systems the way manufacturers configured them will prove or dis-prove your concern and theory. As it happens I am running a "micro-cycled top end" system on sealed deep cycle lead acids so am interested to see if there is a premature failure rate for these batteries. So far no evidence of a problem, most of the batteries are now over a year old. To be clear I make no criticism of you as a person, plainly you are thinking about things which is good, I am happy to debate the points you make with a view to coming to understand the truth and where the theory stands up and also falls over.

You have an EMP shield for all that stuff? Would be a terrible shame to lose all those awesome gadgets.

To a degree you are right and to a degree you are wrong. You are right in the sense that the cycling affects batteries, but I am certain that you charge controller would draw some power and the other gadgets would draw some power. Therefore they are cycling you batteries, but at a lower rate. However, what you described would work well in a grid tie battery back up scenario not in off grid, because in off grid you are already loose money

wow, very good explanation!! do you have a diagram of how you set up the dump using the solar and not the batteries? thanks

you are right!

So have you contacted the manufactures about this? And got their take on it? and what your plan to do?

Let me know how you do the solar because the windmills already did it when my battery is fully charged my charge controller will disconnect the windmills on the charge controller and I'll send it to the water heater without touching my batteries

Well dont shoot me but you need 1 of 2 things....or both... 1 smaller loads split between your 3 dump relys on your 3 controller so you can step when they come in... 2 a load division controller that regulates the load to maintain constant voltage.. not turn on one big load at once

This problem SUX ! I have 3 TracerAN controllers and experience the same issue. My battery bank charges completely under load by 11 am. then the excess power is wasted, furthermore I witness charge cycling on the battery bank ! You are correct in that the solar input has to be redirected to avoid this. I haven’t yet decided on the best modality to do so. Solution 1 involves a inverter with an Mppt input and a wide voltage input ( my panels output are 20-60vdc ) and properly rated capacitor bank for “clouds”. Solution 2 is a inefficient 80v to 12vdc output step down converter 10 amps max. ! Other possibilities are dc heater water elements, dc lighting etc. etc. in retrospect it would have been better if I would have chose an inverter that would natively run at my solar panel “full sun” output power. Any solution requires more expense. Any inaction produces more damage. Electricity is .12 kWh.

Great Tip!

Does he have a video on how to do this?

Use the SSD function on your outback. It uses a percentage of the SSD

That's how i do my system

if battery is full at 13.6 and u dump at 13.7 and over were is this using or cycling the battery. would u not be just using extra power. seems this would help with over charging batteries also.

Couldn't you utilize some capacitors to float and maintain the voltage somehow after switching away from the fully charged batteries? Just a thought, I'm curious myself as to what others could branch from the concept.

Lots of power..

Show us your wiring diagram, please.

I believe you. You've lived the Life for quite some time. There will those snake oil salesmen out there calling for data and such but that's like some random skinny dude walking up to Mike Tyson and telling him how to knock a motherf@&ker out. Keep shining bro✌🏾️☀️

Did you share or make another video the wiring diagram of your dump load?

Good point brah

You mentioned using SSR on the solar side, would it be possible to have the output of the SSR 's into another solar charge controller or a "dumpload" charge controller? So you don't have to worry about connecting DC-DC voltage converters or transformers etc to regulate the dumpload power? Now you will have to build another mining rig to use the dump power. lol Just my 2 cents. Great Videos BTW! keep em coming :)

Any updates on this?

Hey I thought it it works I use three relay and a dump controller and I'm dumplings of the top when the thumb control comes on my charge controllers think it's night time

Add dump Lowe's extra power Tesla battery

The diversion load should be used before the float stage comes to avoid this cycling.

Did not understand anything. Because I do not know English .. Please make such videos that understand every person speaking every language. Do me practical and tell me Connection of A to Z wiring dump load after wind turbine and what equipment will be installed. Do this by doing live practice. Please please please 🙏🙏🙏

How do we know what is a full battery. I have a 48 volt system and all the specks on my AGM batteries. What would be the name for full batteries? Sorry for being stupid, but I can not find a direct answer to this question. Jim in Chile.

So. I've watched ur vid years ago and now, again, im trying to use that extra power to a dump load. The thing is i got my 2 245w panels in a 24v system. Once batteries are fully charged a relay disconnects from charge controller and connect straight to a 600w 24v grid tie inverter. I wonder if the charge controller wont "miss" the panels to fullfill all stages os charging, bulking and floating?!? Im not sure i made myself clear. Hope you can understand the question. Best regards from Brazil.

Well let me know when you pull that video because I want to watch it I have 650 amp hours Lincoln die on and 450 hours off AGM batteries running together Elysium run at 15.2v when the lithium-ion drop down to 13.0 pancake off and the AGM takes over so yes I need to definitely find out

Would it be good to run that through a separate charge controller that is not tied to the battery? That way you are getting to the target voltage vs what the panel voltage is.

Or you could also simply use a smaller dump load. Then no more micro cycling

Why 2 ssr? Negative on ssr too?

Have you created the next video with the reworked dump load circuit via solar panel, Very interested Regards Ross Tga NZ

Schematics would be easier to follow

Will the mppt pickup on the extra load on the pv side?

would be not so bad with lead acid

You mentioned using two solid state relays? Are you actually disconnecting some of the solar panels from your charge controller and routing them to the dump that way they don't interfere with the charge controllers mppt algorithms?

Do you have a follow-up video where you've set up the diversion load? I'm very interested in doing this as well.