Help me pick a controller

767mrN#13

I've bought these 158 Watt panels: http://www.dmsolar.com/dm15somo2pkp.html

I've bought this inverter: This high efficiency DC-AC inverter converts 12 Volts DC to 150 watts of pure sine-wave AC power at 120 Volts, 60 Hz. The unit comes with a cigarette lighter plug. Features include overload protection, low battery alarm / shut down, low idle power draw of less than 0.5 Amps. AC power is available from a single NEMA 5-15R receptacle on the front panel.

I'll pick up a pair of deep cell, golf cart batteries, that I'll put into parallel (Anyone see something I'm doing wrong?) locally.

I need a convertor. Could someone suggest one?

Also, if anyone sees something I'm doing wrong, or might do better, please let me know your thoughts. I'm new to this and very open to suggestions.

Many thanks for any help.

Photowhit

Re: Help me pick a controller

Well... usually you start with what you want to run, but the panels and a pair of golf cart batteries isn't a bad start. The batteries you'll want to run in series rather than parallel since in series they will make a 12 volt battery bank.

What you need is a charge controller, several small ones available. Morning star and Schneider/Xantrex make reasonably priced PWM type charge controller which should serve you well. Do you have plans to expand the system?

Cariboocoot

Re: Help me pick a controller

Okay the system is based on the pair of GC2's. That's 220 Amp hours @ 12 Volts (as Photowhit said you wire the two 6 Volt batteries in series to get 12 Volts).

Now to recharge that you want around 20 Amps @ 12 Volts. The 158 Watt DM panels put out just over 8 Amps each. Two in parallel would be minimum: 16.8 Amps or 7.6% peak charge rate. Three in parallel would be better as it would give you 25 Amps or 11.4% peak charge rate.

That would be with a PWM type controller capable of handling the current. For the two panels it needs to be at least 20 Amp capacity and for three it needs to be at least 30 Amp. This is assuming no long wiring runs between panels and controller eating up Voltage.

Some choices:
SunSaver 20 Amp http://www.solar-electric.com/inverters-controllers-accessories/chco/mochco/stpwmchco/ss-20l.html
ProStar 30 Amp http://www.solar-electric.com/inverters-controllers-accessories/chco/mochco/stpwmchco/ps-30.html
Schneider/Xantrex C35 35 Amp http://www.solar-electric.com/inverters-controllers-accessories/chco/schneider-electric-solar-controllers/tracc35solch.html

There are others and more choices if you want to spend more money.

vtmaps

Re: Help me pick a controller

767mrN#13 wrote: »

I've bought these 158 Watt panels:
<snip>
I'll pick up a pair of deep cell, golf cart batteries, that I'll put into parallel (Anyone see something I'm doing wrong?) locally.

I need a convertor. Could someone suggest one?

What are your loads going to be? Where are you located (want to know how much sun you will get). Will there be any issues with partial shading?

Don't buy the batteries until your system is ready to charge them and you own an hydrometer.

I think you need a charge controller, not a converter. Photowhit mentioned some inexpensive PWM controllers. If you need to squeeze every last watt out of the panels, you might want to consider a (more expensive) MPPT controller.

Have you thought about fuses or circuit breakers?

--vtMaps

767mrN#13

Re: Help me pick a controller

Photowhit wrote: »

Well... usually you start with what you want to run, but the panels and a pair of golf cart batteries isn't a bad start. The batteries you'll want to run in series rather than parallel since in series they will make a 12 volt battery bank.

What you need is a charge controller, several small ones available. Morning star and Schneider/Xantrex make reasonably priced PWM type charge controller which should serve you well. Do you have plans to expand the system?

How would I hook the batteries up in a series? There are no plans to expand the system. Thank you for your help.

Cariboocoot

Re: Help me pick a controller

Batteries in series: (-)BATTERY(+)---(-)BATTERY(+)

767mrN#13

Re: Help me pick a controller

Cariboocoot wrote: »

Okay the system is based on the pair of GC2's. That's 220 Amp hours @ 12 Volts (as Photowhit said you wire the two 6 Volt batteries in series to get 12 Volts).

Now to recharge that you want around 20 Amps @ 12 Volts. The 158 Watt DM panels put out just over 8 Amps each. Two in parallel would be minimum: 16.8 Amps or 7.6% peak charge rate. Three in parallel would be better as it would give you 25 Amps or 11.4% peak charge rate.

That would be with a PWM type controller capable of handling the current. For the two panels it needs to be at least 20 Amp capacity and for three it needs to be at least 30 Amp. This is assuming no long wiring runs between panels and controller eating up Voltage.

Some choices:
SunSaver 20 Amp http://www.solar-electric.com/inverters-controllers-accessories/chco/mochco/stpwmchco/ss-20l.html
ProStar 30 Amp http://www.solar-electric.com/inverters-controllers-accessories/chco/mochco/stpwmchco/ps-30.html
Schneider/Xantrex C35 35 Amp http://www.solar-electric.com/inverters-controllers-accessories/chco/schneider-electric-solar-controllers/tracc35solch.html

There are others and more choices if you want to spend more money.

So I'm only going to get 7.6% peak charging rate? What does that mean? Thank you for your help.

767mrN#13

Re: Help me pick a controller

I'm hoping to use this system in case there is a long term power outage to power a small fridge and maybe a fan or two at night.

I live in southern Illinois. There will be no problems with partial shading.

I haven't thought about fuses or circuit breakers. I'll admit to not knowing why I need them in this system, so I'm open to your input. Thank you for your help.

767mrN#13

Re: Help me pick a controller

Cariboocoot wrote: »

Batteries in series: (-)BATTERY(+)---(-)BATTERY(+)

So connect the negative to the negative and positive to the positive? If I have three golf cart batteries as another has suggested to get a higher charge rate, will that connecting sequence continue? What types of cables should I look for?

Cariboocoot

Re: Help me pick a controller

767mrN#13 wrote: »

So I'm only going to get 7.6% peak charging rate? What does that mean? Thank you for your help.

Minimum recommended peak charge rate for most batteries is 5%. Usually you try for 10% and accept what you get in between. If it is too little current after load allowance the batteries may not charge quickly enough; you run out of sun before you're done. If it is too much current the batteries can be damaged.

I haven't thought about fuses or circuit breakers. I'll admit to not knowing why I need them in this system, so I'm open to your input. Thank you for your help.

You need over-current protection (fuses or circuit breakers) on circuits in case something goes wrong.
Panels are self-limiting in current, so when there are only two (of the same) in parallel no fuse or breaker is required.
Output from the charge controller to the battery is different. Should the controller short the battery is capable of dumping huge current through the wiring in an instant, possibly setting it on fire. The same goes for the circuit between the battery and the inverter (or other DC loads). As such it's a good idea to spend a little money and get a lot of protection.

solar_dave

Re: Help me pick a controller

6 volt batteries are 3 two volt cells in a row. To get 12 volt you need 6 cells in a row. To get that you hook one battery plus connection to the other battery minus. This stacks cells in series.

Your description is a parallel connection and will only yield 6 volts at double a single batteries amp hours.

767mrN#13

Re: Help me pick a controller

Cariboocoot wrote: »

Minimum recommended peak charge rate for most batteries is 5%. Usually you try for 10% and accept what you get in between. If it is too little current after load allowance the batteries may not charge quickly enough; you run out of sun before you're done. If it is too much current the batteries can be damaged.



You need over-current protection (fuses or circuit breakers) on circuits in case something goes wrong.
Panels are self-limiting in current, so when there are only two (of the same) in parallel no fuse or breaker is required.
Output from the charge controller to the battery is different. Should the controller short the battery is capable of dumping huge current through the wiring in an instant, possibly setting it on fire. The same goes for the circuit between the battery and the inverter (or other DC loads). As such it's a good idea to spend a little money and get a lot of protection.

So commercial inverters and charge controllers don't have fuses or breakers built in? Your explanation of getting 5% to 10% is incredibly valuable and something I didn't know. Thank you.

767mrN#13

Re: Help me pick a controller

solar_dave wrote: »

6 volt batteries are 3 two volt cells in a row. To get 12 volt you need 6 cells in a row. To get that you hook one battery plus connection to the other battery minus. This stacks cells in series.

Your description is a parallel connection and will only yield 6 volts at double a single batteries amp hours.

How would you recommend that I set the batteries up? What type should I buy and how should I set the up?

Photowhit

Re: Help me pick a controller

As a back up system, that will be in float most of the time (no loads) the pair of panels might be fine. Understand that you'll get maybe a days backup if drawing on the batteries only also your likely to need a larger inverter to run a fridge. Due to the design you might be able to run one on a 600watt Exeltech but the 1100 watt is just $80 more. There is also an ProWatt 1000 which likely would run a modern fridge. They also make a 2000 watt version that runs $130 more.

I personally would buy Golfcart batteries from Sam's Club or Costco, They run around $80 and they have liberal trade-in/core allowances, they allowed me to use a lawn mower battery!

Inverters usually have some internal protection, and you won't need a fuse or breaker with just a pair of panels, but it's just added insurance between the batteries and inverter. You could get a battery based fuse if you wanted a minimal safety against shorting out the battery.

I don't believe the inverter you have will start your fridge!

767mrN#13

Re: Help me pick a controller

Photowhit wrote: »

As a back up system, that will be in float most of the time (no loads) the pair of panels might be fine. Understand that you'll get maybe a days backup if drawing on the batteries only also your likely to need a larger inverter to run a fridge. Due to the design you might be able to run one on a 600watt Exeltech but the 1100 watt is just $80 more. There is also an ProWatt 1000 which likely would run a modern fridge. They also make a 2000 watt version that runs $130 more.

I personally would buy Golfcart batteries from Sam's Club or Costco, They run around $80 and they have liberal trade-in/core allowances, they allowed me to use a lawn mower battery!

Inverters usually have some internal protection, and you won't need a fuse or breaker with just a pair of panels, but it's just added insurance between the batteries and inverter. You could get a battery based fuse if you wanted a minimal safety against shorting out the battery.

I don't believe the inverter you have will start your fridge!

If it won't do a small, dorm fridge, I'll try an ice maker. If it won't run that, I'm not sure what changes I'll have to make.

The golf cart batteries, I'd put them into a "series" of 2?

TucsonAZ

Re: Help me pick a controller

To be a little more direct and less technical, you're not going to pull off what you want to do with what you have. A 150w inverter will not get the job done for your needs, the start up draw on the compressor for the fridge (or ice maker) is going to be at least 10amps so that would require a 1,200 watt inverter, maybe an 800w with a good surge rating. Also, fans pull a lot of power, it's surprising and you didn't mention the type of fan so that would help. Also, your budget would help, I could make suggestions, we all can but there's no point if your budget doesn't allow for them.

The panels look good, do you already have two of them?

767mrN#13

Re: Help me pick a controller

TucsonAZ wrote: »

To be a little more direct and less technical, you're not going to pull off what you want to do with what you have. A 150w inverter will not get the job done for your needs, the start up draw on the compressor for the fridge (or ice maker) is going to be at least 10amps so that would require a 1,200 watt inverter, maybe an 800w with a good surge rating. Also, fans pull a lot of power, it's surprising and you didn't mention the type of fan so that would help. Also, your budget would help, I could make suggestions, we all can but there's no point if your budget doesn't allow for them.

The panels look good, do you already have two of them?

I can get a bigger inverter. The reason I chose the one I did at first is that it is pure sine and I want it to charge the laptop. From what I understand, I could have done it with a modified sine. I just figured that a pure sine in reserve wouldn't hurt anything.

So for a small fridge, I'm going to need a 1,200 watt inverter? Another reason I chose a small inverter at first is because I was warned that you want to match the inverter to the job. From what I understand, if I hooked up a 1,200 watt inverter for a small job, it would drain the batteries quicker.

The big thing I'm looking for now is a converter. Do you have to match the converter to the job? Or do you match it to the two, 158 watt solar panels? Any more suggestions for an inverter would be appreciated.

TucsonAZ

Re: Help me pick a controller

767mrN#13 wrote: »

I can get a bigger inverter. The reason I chose the one I did at first is that it is pure sine and I want it to charge the laptop. From what I understand, I could have done it with a modified sine. I just figured that a pure sine in reserve wouldn't hurt anything.

So for a small fridge, I'm going to need a 1,200 watt inverter? Another reason I chose a small inverter at first is because I was warned that you want to match the inverter to the job. From what I understand, if I hooked up a 1,200 watt inverter for a small job, it would drain the batteries quicker.

The big thing I'm looking for now is a converter. Do you have to match the converter to the job? Or do you match it to the two, 158 watt solar panels? Any more suggestions for an inverter would be appreciated.

I think you mean charge controller which is not the same as a converter although it does "convert". Matching to the job is good with the inverter and having the 150w may come in handy for you as you can always use that one for smaller jobs and the other for larger jobs. For example, turning off the larger inverter for the last 8 hours of night time if your battery bank is getting low.

As for charge controllers (do not have to be matched to the load but have to be able to handle it, so you can go much bigger but not smaller), again, you didn't mention a budget, I would get a Rogue for $250 and run your panels in series but if your budget is only $100 that would change things a little.

767mrN#13

Re: Help me pick a controller

TucsonAZ wrote: »

I think you mean charge controller which is not the same as a converter although it does "convert". Matching to the job is good with the inverter and having the 150w may come in handy for you as you can always use that one for smaller jobs and the other for larger jobs. For example, turning off the larger inverter for the last 8 hours of night time if your battery bank is getting low.

As for charge controllers (do not have to be matched to the load but have to be able to handle it, so you can go much bigger but not smaller), again, you didn't mention a budget, I would get a Rogue for $250 and run your panels in series but if your budget is only $100 that would change things a little.

Yes, you are correct. I meant a controller. It sounds like, with two, 158 Watt panels a controller that can handle 300 watts UNLESS I plan on expanding the bank later, then I should get more.

When you put 2, 6 volt, golf cart batteries in a series, does that equal 12 volts in terms of buying a 12 volt controller? If so, do you have to get a 24 volt controller if you have more than 2, 6 volt golf cart batteries?

Thanks to you folks, it looks like I may be getting close to the basic system (then I know I have to deal with issues such as fuses or breakers on the system).

vtmaps

Re: Help me pick a controller

767mrN#13 wrote: »

When you put 2, 6 volt, golf cart batteries in a series, does that equal 12 volts in terms of buying a 12 volt controller? If so, do you have to get a 24 volt controller if you have more than 2, 6 volt golf cart batteries?

Most controllers are rated by their output amps, and can work with multiple battery voltages. For example, a 20 amp controller could push almost 300 watts into a 12 volt battery bank (when the battery voltage gets to absorb voltage of about 14.5 volts, 20 amps X 14.5 volts = 290 watts).

The same controller pushing 20 amps into a 24 volt battery: 20 amps X 29 volts = 580 watts.

--vtMaps