solar hooked straight to the batteries question.

gww1 · November 2012

Would hooking 90 to 100 volts directly to a 48 volt battery bank charge the batteries correctly and efficently? When the batteries clamp the voltage what will be the actual result? 90 volts and 20 amps.
Thanks
gww

Cariboocoot · November 2012

Re: solar hooked srait to the batteries question.

gww1 wrote: »

Would hooking 90 to 100 volts directly to a 48 volt battery bank charge the batteries correctly and efficently? When the batteries clamp the voltage what will be the actual result? 90 volts and 20 amps.
Thanks
gww

No.
The panels will try to push the Voltage up, up, up. More than likely they will succeed. When the battery Voltage goes high, the electrolyte will 'boil' off. Left too long the plates will be exposed and then the battery is cooked.

Bad idea.

gww1 · November 2012

Re: solar hooked srait to the batteries question.

cariboohoot
If I had a different contoller mx60 hooked to the batteries with different solar hooked to it and a load to kick on through the inverter with this load being kicked on based on battery voltage. This "hopefully" would controll the battery voltage. If the above is ok, would I lose a lot of the panel wattage of the panels that were hooked directly to the batteries due to the high voltage differance?
Thanks
gww

Cariboocoot · November 2012

Re: solar hooked srait to the batteries question.

If you have an MPPT type charge controller such as the MX60 you connect the panels to the input and the battery to the output and it will regulate the charge. It will not care if array Vmp is 90-100 Volts. For a 48 Volt system 70 Vmp is "ideal" but the efficiency will not be significantly reduced by an extra 20 - 30 Volts.

Once the batteries are charged (and as they charge), loads can be offset by any 'extra' current capacity available from the array.

gww1 · November 2012

Re: solar hooked srait to the batteries question.

cariboocoot
I have too many panels for my one mx60. The panels also are not the same although I could get close on the voltage. I wanted to hard wire the panels in a fasion that if I actually ever got another mppt controller, I would not have to break the wire and re-configure them. I have a morningstar ts60 but it is not mppt. I am going to hook my turbines to the batteries and was thinking of controlling the batteries with loads "hot water heater through the inverter" with maby a redundent dump through the morningstar. I guess the only real issue would be the reconfiguring of the panels if I got another mppt controller. If I am still out of line in my direction please correct me. If you thing what I am trying to do might work but not at the high panel voltage then what should I try to wire for that more closely fits direct connect or pmw controller. Or would the 90 volts work if I control the battery charge level? I am not aurguing just giving more info. I thank you very much for responding.
gww

Cariboocoot · November 2012

Re: solar hooked srait to the batteries question.

What you're describing is using the controller as a "dump load" controller: power input directly to the batteries, any "excess" Voltage detected and "bled off" by the controller.
The MX60, as much as I like it, is not a good choice for a dump controller. In general MPPT controllers don't work well for this. PWM controllers like the TriStar 60 work better for this.

That said, if your input Voltage is high in that sort of set-up the dump controller will be working a lot just bleeding off Voltage. This means power that might be going to charging will instead be dumped just to keep the Voltage in range (as opposed to using the MPPT function to turn the higher Voltage in to greater charge current).

Would it work? In theory yes, but it won't be efficient and it will be 'hard' on the controller; expecting it to bleed off 20=30 Volts instead of the "usual overhead" of about 10 is likely to result in premature failure. I've never heard of anyone using a dump controller with that much Voltage difference and as such I can't recommend it.

You could talk to Morningstar. They are very good about answering questions.

gww1 · November 2012

Re: solar hooked srait to the batteries question.

Cariboocoot
I was actually not going to have any dump load on the charge contollers unless I had a failure of the inverters. I thought I could use the auxillary mode on the mx 60 to trigger a load with low voltage ssr that would turn on a high voltage a/c load to the inverters. The redundant second dump should never be used except during a inverter failure. Mostly I am trying to not have to buy another mppt cc just to use my stuff. Also I have a 200' wire run from pv to the batteries. Does 68 volts sound more reasonable for direct connect? I want to set the arays up for mppt and exspantion but want to get it going as cheaply as possible. I have to spend alot to install and am trying to use what I have. maby someday I will add the $550 charge controller. I thought the issue would be the batteries would clamp the solar and I would lose about 800 watts due to the lower voltage at 20 amps. I wasn't sure so I thought I would ask.
Thanks
gww

I hope you don't think getting info from me is like pulling teeth. I am never sure if I talk clear or not.

Cariboocoot · November 2012

Re: solar hooked srait to the batteries question.

The thing is that unless the MX60 is wired as a charge controller normally would be it won't work; it needs battery Voltage on the output just to turn on.

As you describe it, you could use a Voltage controlled relay to switch on the load (it is essentially a dump load by function, even if it is a load on the AC side of an inverter). In any case I would be concerned about the Voltage variations on the battery bank in respect to the inverter(s)'s input limit; it is possible it may rise too high. Keeping the array Vmp down around 70 will reduce that risk considerably, but not eliminate it. There would be a lag between when the battery Voltage is pushed above the limit by the panels and the point the load activates and pulls the Voltage down again. The more circuitry involved (control, inverter, load) the longer the lag and great potential problems from momentary over-Voltage.

gww1 · November 2012

Re: solar hooked srait to the batteries question.

Cariboohoot
Most people who run turbines have no choice but to hook up in just this fasion. I was trying to consider the solar as just anouther turbine which I will have also. I guess I need to read the morningstar manual again to make sure but I think it will shut the solar down if I hook up through it. I think I lose the extra dumpload if I use it this way though. I was trying to keep from having the solar shut down and using all the power but maby the turbines and solar will be just too much to direct connect. I did like an emergency dumpload though. I see no choice on the turbines though, as this is the only way I have ever seen them hooked up.
Thanks
gww

Ps I got this ideal from another web forum were they are using the classic charge controller in just this fassion. I believe the auxillary turns on with out changing the charging perimaters of the mx 60 and everything is hooked up normally. I could be wrong.

Cariboocoot · November 2012

Re: solar hooked srait to the batteries question.

Not exactly.

The standard hook-up for a dump load with turbine is using something like the TriStar PWM controller (which actually has settings for being used this way) to monitor battery Voltage. The turbine does go directly to the batteries, but the Voltage output from the turbine would be in the same range as typical for the battery bank (in this case around 62 max). When Voltage exceeds the programmed point at the batteries for the charge stage the controller then sends power to the dump load. This is all done with DC, and thus is more efficient than trying to control and AC load on the output side of an inverter; less circuitry, no conversion, no worries about delay allowing the Voltage on the inverter to rise. The controller and dump load need to be sized to take the maximum amount of power that could be generated by all sources once the batteries are full. NEC rules actually require redundant dump controllers in case one should fail, as the result of not handling that power could easily set something on fire.

MidNite makes specific controllers for wind turbines: the Clipper http://www.solar-electric.com/miso1waactuc.html These are about the best you can get.

When using the MX60 AUX function, it is normally wired as a standard solar controller with the AUX triggering at a certain Voltage set point (either Absorb or Float but not both; batteries kept at high Absorb too long will lose a lot of water and suffer shorter life). There is no risk here with system Voltage reaching levels too high for the inverter.

If that should happen, by the way, the invert shuts down from over-Voltage which means your AC dump load is now totally unpowered and completely ineffective. Guess what that would do.

The TriStar can be used as a dump load controller in the manner I described above. Take a look at the simple diagram at the bottom of the spec page here: http://lib.store.yahoo.net/lib/wind-sun/TSdatasheet.pdf

If at all possible, use the MX60 to control solar to the batteries and the TriStar to dump excess from wind power. I don't know what you've got for solar or wind or battery bank size, so I can't even come close to a specific layout for you. I'm just pointing out the pitfalls that could occur should you try to feed a lot of Voltage/power to a battery bank without the right method of controlling it.

gww1 · November 2012

Re: solar hooked straight to the batteries question.

Cariboocoot

I don't know what you've got for solar or wind or battery bank size, so I can't even come close to a specific layout for you. I'm just pointing out the pitfalls that could occur should you try to feed a lot of Voltage/power to a battery bank without the right method of controlling it.

I ask so you could point out the pitfalls and thank you for doing so.

What I am working with is:
1 dual outback gvfx 3648 inverters and the bells and wistles.

2. 12- 235 watt mx panels

3. 2000 plus watts of home made solar half panels 9 volts 30 watts each. evergreen cells.

4. Two hugh piggott 500 watt 8' wind turbines

5. one mx60 charge controller.

6. one morningstar ts 60 charge controller.

7. one "4volt-34volt dc " "600 volt ac" 25 amp ssr

8. one 12 pole combiner box.

9. one fused turbine shut down box.

10. no batteries "thinking 16 sams club" and nothing installed yet. also intend to buy a 50 gal 240 volt electric hot water heater to pre heat for my propane one. I will change the heating elements to 2000 watt ones.

I don't mind if you think most everything has been covered and don't respond furthur. If something pops into your head I would love to hear it. You have been patient and helpfull and I thank you.
gww

PS even though a dump through tristar is easyer, going through the inverter make the power more usable and I'm told that 240 volt water heating is much more effictiant then trying to do the same with dc voltage even with its inherant losses. Also sorry about the spelling. I am a highschool drop out and the spell check I tried to download almost stopped my computer untill I found a way to uninstall it.

Cariboocoot · November 2012

Re: solar hooked straight to the batteries question.

Everything you've listed there is a pretty good assortment that should work together.

As I said, the issue with using an AC dump load on the inverter is one where the inverter would shut down then you have no dump load; batteries can be fried.

Despite what you've been told (by non-engineers) converting excess DC power to AC power in order to run a hot water heater element is definitely not more efficient. It is in fact less so as some of the power dissipation will be as heat through all that circuitry rather than heat in the water tank itself.

As far as loading the water heater elements goes, if you do not need to power them as a matter of course to heat water the fact that they are "AC" is not relevant: they're just resistors. You can feed them AC or DC at any Voltage and they will behave the same; as resistors. The important thing is that they be the right value resistor. As 240 Volt 3500 Watt elements they'd be about 16 Ohms.

The MX60 will handle your 2820 Watt array on 48 Volts. No problem there.

You have two 500 Watt turbines: 1000 Watts potential that needs to be controlled. On 48 Volts that's only 20 Amps or less (as system Voltage goes higher, current goes down). The TriStar should have no trouble handling that as a dump load. You might want to change out the water heater elements for 120 VAC versions so you'll get better conversion of Amps into heat.

It looks workable to me.

And we certainly don't worry about spelling around here.

gww1 · November 2012

Re: solar hooked straight to the batteries question.

That still leaves me with 2000 watts worth of panels to inigrate to the system. If I also dumped this through the morning star I would be hitting about a 50 amp dump. I believe part of the reason I was told it was more effiteant with the 240 volt ac had to do with the configuration, if I even understand. When the batteries get to a certain point the ssr is pulsed not giving full power to the element and and keeping the charging current to the batteries so the panels work at full power. As the batteries get fuller the pulse to the ssr gets steadier and the power increases to the elements. Therefore it is not an all or nothing switching all on or all off situation. I could be misinterpiting. It is a long post on otherpower forum by chris olson who also posts on here at times.

I know with another mppt controller I can use the 2000 watts also. This is my weak spot and I was just looking for a work around.
thanks
gww

Cariboocoot · November 2012

Re: solar hooked straight to the batteries question.

Your proposed battery bank: 440 Amp hours @ 48 Volts.
2820 Watts of commercial panels will charge that. The other 2kW are not really needed. The turbines (if working) will provide about 50% of the battery bank's needs alone.

I'd advise against adding the 2kW of panels without a bigger battery bank. Or you could manually switch them in (providing they are Vmp compatible) to the MX60's input on cloudy days if production from the others is below 50%.

Or you could simply tie the surplus panels directly to the water heater. Whenever they produce power they will heat water. When they don't, they won't. No batteries = no need for regulation. Only problem is running the DC across the tank's thermostat, as they are not designed for DC and it could weld shut or burn contacts so that they don't. Even getting around that with an AC powered relay to control the DC from the panels would be easy.

gww1 · November 2012

Re: solar hooked straight to the batteries question.

cariboocoot
I really think I have to discount the turbines at this time. I don't know what I am going to end up with on tower hight at this time. currently I have one 40' lattice type that will probly be 45' after adding the pipe to put the turbine on. 70' would meet all the rules. I don't have the second figured out yet. secondly I am in a zone 2 wind area.

My house uses about 30 kwh per day when I lived there. I thought I could load the sub panel with loads till I just had enough to easily charge the batteries and use the dump for miss caculations and when we did have wind. Even with this rout I won't be able to put my whole house on the inverters.

I knew my battery bank was small but thought if I could work on day time loads and the hot water heater when that failed that that would be cheaper then a large battery bank that I might ruin while configuring the system and learning how to read and take care of batteries. I picked 16 batteries insted of eight cause I thought the inverter might need it to start loads properly. I am not even opposed to adding eight more batteries if that is what will make it work.

I know that sounds funny as I am groaning about maby needing another charge controller.

I guess not being off grid and having very few power outages give me a differrent perspective. I kind of want to use as much power as I can wile I make it with out stressing the batteries too much. I know your suggestion of direct connecting the solar to the hot water heater does that but, I don't really want hot water, I just think hot water is better then shuting the panel output down due to not enough loads in a specific time period when the batteries fill up faster then normal. I will win with the hot water just coming to room temp before being heated by propane.

I do not think the home made will hold up over the long haul. You can buy cheaper then you can build. Perhaps it a pride issue but I would really like to get some use out of them as I spent all winter building them. If I don't wear out or get discusded first I know I will have to eventually weed them out. I will have the infrastructure to replace them though.

Is my ideoligy hairbrained when put to the real world and how things really work?
Thanks
gww

PS I can make the home made panels pretty compatible voltage wise at many fewer amps. I don't think in parelel the amps matter if they are different. I really was hoping to get closer to seamless operation then manually schedualing loads or switching panel imput if possible.

Cariboocoot · November 2012

Re: solar hooked straight to the batteries question.

Let's just say you seem to be going at it from all directions and yet not arriving at a destination.

With two GFX 3648's and utility power available probably the obvious path is to get a legal grid-tie set-up. These leaves out the homemade panels of course and the wind turbines as well. But you can't beat the grid as a place to 'put' any surplus power you might make. Ideally to do that you'd need more panels (like 3600 Watts per 3600 Watt inverter) and to use both GFX's you'd double the set-up. But that means quite a lot of money to invest.

At 30 kW hours per day, spending $30 on a Kill-A-Watt and having a close look at everything might prove more worthwhile than doing anything else.

gww1 · November 2012

Re: solar hooked straight to the batteries question.

I have a killowatt meter I am just not on location to use it due to work. I still have a little time to work things out which might be part of the all over the board reason. I am not set in granite on anything but trying to get set so that when it is time to act I can. I would sell my outback and go batteryless if I actually decide to go grid tie. Thats what I originally wanted to do but I couldn't get any responces from poeple who were grid tied in Mo and I also have a hard time being partners with any one with power over me. I take it that I need more info from location that I can't get. I really want the wind turbines. not cause I think they will do that well just that they haven't wore me out yet. You notice I said yet. I am probly all over the board yet due to not knowing how things really work. Thats probly why newbees "probly me" ruin there first battery bank. If I get another charge controller do I need more batteries? Also, I had a destination I just didn't get the affermation that it might work and I keep having to adjust as I come up with questions and roadblocks. My destination apparently won't work so back to the drawing board.
Thanks
gww

Cariboocoot · November 2012

Re: solar hooked straight to the batteries question.

Normally if you go with an off-grid system of any type you first figure out how much power you want/need to supply. This determines the battery bank size, which in turn dictates how much charging capacity you need.

If you go buy more batteries and another controller to make use of the extra 2kW of panels, what happens when those panels fail? The batteries don't get charged by solar so you have to charge them some other way.

Right now the 440 Amp hour 48 Volt battery bank you propose would work well with one of the 3600 Watt inverters, the MX60, and the 2820 Watts of panel. What you'd expect:

25% DOD on the battery bank = 4.7 kW hours per day. 4 hours equivalent sun on the panels = 5.8 kW hours per day (always good to have more panel than battery power). This is about 15 to 20 percent of your daily use.

That much of it at least is perfectly viable.

gww1 · November 2012

Re: solar hooked straight to the batteries question.

cariboocoot
Great clear answer. I do understand what you are saying. Your options are not as wide as my discussions seemed to come to from disscussions with others. Its like going to the doctor and getting a second opinion before treatment. When you ask what I exspected, I will tell you. I thought that I had so much use that couldn't be covered and so much freedom of what loads I picked from that use, that I didn't need to know my loads. I wasn't looking for backup power. I have the grid so I was going to figure out what fit my production and move it to the sub panel. I wasn't going to pick what was important and try to cover that. I was just going to match my panels batteries and sunlight. I figured this would give me the freedom to have a smaller battery bank and just use the power as I go. I bought the inverters and had the stuff paid for so even though it was more exspencive then just using the grid it wasn't now cause it was payed for. I understand what you are saying will work for off grid. I wonder if it is all there is for on grid with no real worrys of backup power. I am not questioning you reasoning and I will probly follow your advice but in the back of my mind I had more hope and discussions that lead me to believe I wasn't that far out of line on all my other thinking. This original post was to only figure out what direct high voltage would actually mean if hooked strait to batteries. don't get me Wrong I am glad That I get to think about this other stuff also. I guess I got some more thinking to do. Even though I understand what you are saying will work I can't compleetly understand why for my situation where I am going wrong. If I don't listen compleetly I will pay for my mistakes as always and if I do listen it sounds like I got 2000 watts to put at the creek with the 180 watts Ive had there for over a year. The camping experieance may go way up.
thanks
gww

PS I wonder how microwaved fish would taste?

gww1 · November 2012

Re: solar hooked srait to the batteries question.

What I intend to do as of now.

1. Connect the 2820 bought panels to the mx 60 cc.

2. Hook the turbines to the battery with a 1000 watt dumpload through the morningstar cc.

3. Connect the 2000 watts of home made panels directly to the batteries at seventy volts and turn the breakers to them off in the combiner box.

4. Hook the ssr for the hot water heater to the auxilary on the mx 60 cc and set it to funtion during absorb. I accept the loses.

I am going to try to match loads to end up with a 50/80 battery discharge/charge regiment with a full charge being provided every 7 to 14 days.

I am going to turn on the 2000 watt homade panels on low production "cloudy" days and on days I need to bring the batteries above 80% dod to facilitate a full charge.

I am thinking to start with 6 kwh daily use for the load. I will find this by moving one circuit at a time from the main panel to the sub-panel and then watching the outback monitor for a day to a week to see the average kwh use. I will do this till I get to the 6 kwh that I "think?" I need.

I am guessing that about 6 kwh's worth of daily loads will slowly drain the batteries to 50% dod over a few days with only the 2820 watts bought panels. If I get wind this time to discharge will be exstended. No matter what I will make a full charge with in a 14 or less day period. If the batteries get to 50% dod quicker then I thought I will use the grid to run the loads till corrected.

Weaknesses that even I can see;

1. Not very seemless and needing much oversite.

2. Possibility of extended absorb times being hard on batteries.

3. Possible low charging amps due to the high draw of the hot water heater element.

Some possible salutions:

1. Start with a slightly discharged battery, run no loads and then charge with just the bought panels. While doing this, watch the charging amps and when it gets to 2% current going into the battery for a period of time record it and then set the absorb cycle to this time.

2. Do the same as you did in paragraph one above only with the ssr attached and triggering the load and see if the values hold true and if not adjust accordingly.

3. As I learn what is happening consitantly make the adjustments to make it more seemless.

The batteries sold in Missouri will make a 416 amp hour battery bank.

I know I will have to keep a constant watch on things untill I learn better.

I also know not to expect much from the hot water.

Is this a safe starting point with my system for me to learn from and then adjust as I gain knowlage?

Did I discord every bit of advice I got or am I on the right track?

Cariboocoot, thanks for the time you gave.
Cheers
gww

Cariboocoot · November 2012

Re: solar hooked srait to the batteries question.

4. Hook the ssr for the hot water heater to the auxilary on the mx 60 cc and set it to funtion during absorb. I accept the loses.

I have to point out that this different from using a hot water heater as a dump load. This is an "opportunity load" and a really good idea. Lots of off-gridders will do this: use the MX60's AUX function to turn on a big AC load once the batteries are in Absorb or Float.

I am going to turn on the 2000 watt homade panels on low production "cloudy" days and on days I need to bring the batteries above 80% dod to facilitate a full charge.

Another good idea.

I am thinking to start with 6 kwh daily use for the load. I will find this by moving one circuit at a time from the main panel to the sub-panel and then watching the outback monitor for a day to a week to see the average kwh use. I will do this till I get to the 6 kwh that I "think?" I need.

I'll suggest that experimenting this way to see how much you can gain from the panels is good, but once you have a firm average production you can count on your best bet is to put as many consistent loads on as possible. That's the stuff that you can count on to be running fairly regularly every day like refrigerator (always good to have back-up power on that anyway) and any other constant or consistent use (same lights every day, power feed for control systems, et cetera). This way you make best use of your solar and only tap the utility to power this stuff if necessary.

1. Not very seemless and needing much oversite.

Welcome to the world of battery systems.

2. Possibility of extended absorb times being hard on batteries.

The MX60 will adjust Absorb time according Bulk time, with the ability to limit Absorb by minimum and maximum time and also End Amps. With a bit of experimenting you'll find 'best settings' for this to keep the battery life as long as practically possible.

3. Possible low charging amps due to the high draw of the hot water heater element.

Not if you limit the heater's activation to when you know the Amps are available. Basically, though, a 3500 Watt element is going to nail a 2820 Watt array flat. This is why I suggested powering it from the other 2kW. You could have the system wired to cut that 'extra' array in when the water heater is on.

As I learn what is happening consitantly make the adjustments to make it more seemless.

Yup, yup, yup. You will also make adjustments according to how you use the system so that it best suits your needs. Right now you've got lots of options, which can be a bit daunting.

Here's something that may add to your possibilities: electric water heaters have two identical elements in them that operate in sequence, not simultaneously. For low power pre-heating sometimes people will wire the elements in series so that they both come on at the same time, but at half power.

Another thing is that your Outback inverters are 120 VAC and water heater standard elements are 240 VAC. You can stack the two inverters for 240 VAC, but technically you'd need a bigger battery bank to accommodate full power draw.

I'd say get the main system running and taking some of the load off the utility, then start experimenting with any "extra" power you may have available for opportunity loads.

gww1 · November 2012

Re: solar hooked straight to the batteries question.

cariboocoot
Thank you for your help.
gww

inetdog · November 2012

Re: solar hooked srait to the batteries question.

Cariboocoot wrote: »

Here's something that may add to your possibilities: electric water heaters have two identical elements in them that operate in sequence, not simultaneously. For low power pre-heating sometimes people will wire the elements in series so that they both come on at the same time, but at half power.

Just in case anyone is confused by this: With two elements in series at 240 volts, you get half the power of ONE element (same voltage but twice the resistance so 1/2 the current), or 1/4 of the power you would get using both in parallel (which the thermostats in the heater normally do not allow.)

There is certainly no harm in driving an element at 120 volts, and it will still allow you to get to the same ultimate temperature, just slower. Your opportunity load will just be 1/4 of the rated power of the same element when run at 240.
For many electric water heaters you can get replacement elements which are designed for 208 volts or for 120 volts at higher current. Check out the cost of those if they are available for your heater. (To some extent the heating elements are "universal" in that they fit a standard size/thread opening in the tank.)

If you do not need really high power or you have a lot of heater elements, you can even connect the elements directly (via a relay) to your battery voltage (best if it is 48 volts) or panel voltage and not waste power in the inverter.

gww1 · November 2012

Re: solar hooked srait to the batteries question.

Inetdog
Thanks
gww

solar hooked straight to the batteries question.

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