Kiss

[hkellogg]

The Keep It Simple Stupid principle.

When I decided to put a solar system on my RV I contacted a dealer in AZ who specialized in RV solar. Having been to Camping World and other venues I expected to not only have to buy the panels but all the other gizmos that they sell. Believe it or not this guy was a honest man. He sold me a 130 Watt panel and that was it. He instructed me to take an extension cord cut it off 3 foot from the female end and attach that one to the batteries (two 12 volt, 100 ah, marine in parallel) and the other end to the panel. That way I could move the panel where ever I wanted when camping and I would just have to plug it in to the batteries. When I inquired about a controller etc. he said that if you kept it under 150 watts none was needed. He was right. Going on my 5th year of almost fulltime RVing and have never run out of juice or replaced the batteries. I use the generator for about 5 minutes to fire up the Micro wave and that is it. The RV had LED lights, my computer and 24" monitor are very low wattage and I have unlimited data plan with Verizon.

My point is that I've seen so many complicate systems with people spending hundreds if not thousands of dollars on controllers and other possibly unnecessary gizmos that I believe are not needed if you keep each panel and battery system isolated and not centralized.

Here is my hair brained plan for a thousand square foot cabin in Wisconsin. Instead of a centralized battery bank with panels feeding into a controller or three I'm proposing to instead, follow the KISS method, I have used for both my boat and RV. Six 150 Watt panels each connected directly to two 12 volt batteries with each panel and batteries separate from each other. No controllers etc. needed. Put in an on/off switch for night time disconnect and that's it. Have mostly DC powered water heater, crock pot, coffee maker, refrigerator etc. Have a few AC outlets for backup and a few trickle chargers and a couple of 2000 watt inverters for odd situations and that's it.

Anticipated advantages: No loss of electricity due to inverters and shorter wire runs. Lower initial cost by cutting out the controllers etc. Mostly off grid and basic appliances usable if power goes out. Most of all it's a simple system that doesn't need an advanced degree in electronics to setup, fix, customize or understand.

Am I barking up the wrong tree here? Anyone see any obvious flaws or major problems? As I've said I have been doing this on my RV and boat for over 5 years without any problems. Have I just been lucky?

Thank you in advance.
Harry

[Sunking]

Here is my hair brained plan for a thousand square foot cabin in Wisconsin. Instead of a centralized battery bank with panels feeding into a controller or three I'm proposing to instead, follow the KISS method, I have used for both my boat and RV. Six 150 Watt panels each connected directly to two 12 volt batteries with each panel and batteries separate from each other. No controllers etc. needed.

Well two problems with you KISS approach. you are throwing away money and at high risk of destroying your batteries.

One to connect directly to batteries means you have to use very expensive battery panels. If you connect 900 watts of panels directly to the batteries you turn your 900 watt panels into 600 watt panels. Second problem with two days of no use will fry those batteries.

Use much less expensive higher voltage Grid Tied panels of 600 watts with a MPPT controller. 600 watts of GTI panels will be 1/3 the cost of 900 watt battery panels. More then enough saving to buy a good quality 80 amp MPPT charge controller and never risk burning up your batteries for less money than your method.

KISS that.

[SunEagle]

The Keep It Simple Stupid principle.

When I decided to put a solar system on my RV I contacted a dealer in AZ who specialized in RV solar. Having been to Camping World and other venues I expected to not only have to buy the panels but all the other gizmos that they sell. Believe it or not this guy was a honest man. He sold me a 130 Watt panel and that was it. He instructed me to take an extension cord cut it off 3 foot from the female end and attach that one to the batteries (two 12 volt, 100 ah, marine in parallel) and the other end to the panel. That way I could move the panel where ever I wanted when camping and I would just have to plug it in to the batteries. When I inquired about a controller etc. he said that if you kept it under 150 watts none was needed. He was right. Going on my 5th year of almost fulltime RVing and have never run out of juice or replaced the batteries. I use the generator for about 5 minutes to fire up the Micro wave and that is it. The RV had LED lights, my computer and 24" monitor are very low wattage and I have unlimited data plan with Verizon.

My point is that I've seen so many complicate systems with people spending hundreds if not thousands of dollars on controllers and other possibly unnecessary gizmos that I believe are not needed if you keep each panel and battery system isolated and not centralized.

Here is my hair brained plan for a thousand square foot cabin in Wisconsin. Instead of a centralized battery bank with panels feeding into a controller or three I'm proposing to instead, follow the KISS method, I have used for both my boat and RV. Six 150 Watt panels each connected directly to two 12 volt batteries with each panel and batteries separate from each other. No controllers etc. needed. Put in an on/off switch for night time disconnect and that's it. Have mostly DC powered water heater, crock pot, coffee maker, refrigerator etc. Have a few AC outlets for backup and a few trickle chargers and a couple of 2000 watt inverters for odd situations and that's it.

Anticipated advantages: No loss of electricity due to inverters and shorter wire runs. Lower initial cost by cutting out the controllers etc. Mostly off grid and basic appliances usable if power goes out. Most of all it's a simple system that doesn't need an advanced degree in electronics to setup, fix, customize or understand.

Am I barking up the wrong tree here? Anyone see any obvious flaws or major problems? As I've said I have been doing this on my RV and boat for over 5 years without any problems. Have I just been lucky?

Thank you in advance.
Harry

My personal opinion is that you were lucky not to have destroyed either of those 100Ah batteries.

First, I don't see how you can properly charge a 200Ah battery system in one day with only 7 or 8 amps from that 130 watt panel. If you were able to do so that can only mean you barely discharged those batteries.
Second, if you barely discharged the batteries on a daily basis there would be a high chance of cooking one or both of them since you have no charge regulation to keep the batteries from boiling themselves because they are fully charged but the panel doesn't know that.

While I agree you can KISS and build a small solar/battery system like you did on your RV when your daily load is very small but it doesn't make sense to do the same thing when building a bigger system using multiple small systems. What you have really done is build a complicated system with more places to fail and more batteries to inspect and not really having the potential to run any of your larger electrical loads like that refrigerator or coffee make which will need more than a 150 watt battery system.

I would estimate that the cost of those six 150w systems (including batteries and inverters) would be more than building a single 900 watt system using grid tie panels, a good MPPT CC, a 24volt battery system made up of 6volt high Ah rated batteries and a pure sine wave inverter.

Of course you did have some luck with your RV system so you might also have the same luck with those 6 x 150 watt system. But I think you are trying to keep it too simple and will result in a system that doesn't meet your true daily watt hour needs.

[Sunking]

If you were able to do so that can only mean you barely discharged those batteries.
Second, if you barely discharged the batteries on a daily basis there would be a high chance of cooking one or both of them since you have no charge regulation to keep the batteries from boiling themselves because they are fully charged but the panel doesn't know that.

Unless he has Blocking diodes his batteries discharge all night. Personally I don't believe a word of it. 600 watts into 12 volt 200 AH batteries my rear end.

[Wy_White_Wolf]

There's a couple of details in the KISS system that the guy didn't tell you. First it's not a standard 150 watt to stay under. It's about a C/50 charge rate. For your 200 AH of batteries that would be (200/50) 4 amps. The 130 watt panel did put out more than that but as long as you used most of the power it wouldn't fully charge you batteries.

Now the problem with what you have planned. You've done nothing to calculate how much power your loads need. Really a DC water heater. That thing is easily going to overload your parial system. I don't think the full 900W of panels and batteries could support that.

Good luck but just remember when your sitting in the cabin in the dark that KISS has it's downside.

WWW

[SunEagle]

Unless he has Blocking diodes his batteries discharge all night. Personally I don't believe a word of it. 600 watts into 12 volt 200 AH batteries my rear end.

I believe the RV system was more like a 130 watt into a 12v 200Ah system. So that panel won't produce much amperage to recharge the batteries in one day for most of the year. And if it does recharge them back to 100% it means he must be using less than 10% DOD of that system. That can result in the possibility of over charging during the summer months due to more sun hours and minimal battery usage.

I still think that if that system lasted him 5 years he got lucky or is misrepresenting his system's capabilities.