Solar Power

[sushidog]

Great thread. Thanks for all the great ideas folks!

I will be going FT in about 3 years in a TT and am planning on building a FT boondocking rig. My system will allow complete off-grid power independence. Such a system will be rather complex, heavy and expensive, but doable within my budget (weight and monetary). I will have both a 12v and a 48v battery bank. The 12v side of the house, consisting of 2, CG-2 golf cart type batteries or 2 Rolls S-550s will be used to power my slides, LED lighting, fridge board, water pump, etc. It will be recharged by a single 300-325 watt solar panel. My 48v side will consist of 8-GC-2s (to start) which will power a 48v DC mini-split 12,000 BTU heat pump (which has an EER of 21.42 - drawing only 11.5 amps for cooling) and a 2,000 watt AIMS PS inverter for my A/C needs. They will be recharged by 6, 300-325 watt solar panels. I particularly like the SUN high-efficiency 325 watt modules that Sun Electronics has for only 64 cents/watt for less than pallet quantities. These are light enough (at only 41 lbs each) to be moveable, if necessary. But with 2,100-2,275 watts on the roof, they should produce sufficient power for my needs just leaving them mounted flat.
Here's a couple links so you can see what I have in mind:
http://www.geinnovations.net/HSAC_Productline.html
http://sunelec.com/

I plan on using 2 controllers, a Tristar TS-MPPT-45 for the 48v side, and a Tracer 3215BN MPPT for the 12v system. I will use one monitor for both, the new Pentametric meter from Bogart Eng.

I should be able to construct the total system for around $6,500. ($7,400 with an EU2,000 Honda generator back-up) Though this sounds expensive, if I consider the savings in not just my power bill, but RV park/GC fees it should easily pay for itself very quickly in full-time use. If I estimate the average monthly GC rate of $400 plus a metered electric bill of $100, This $500/month savings would put the payback of only 15 months (less if I qualify for a federal subsidy at the time of purchase). The panels and hardware should last for my lifetime and the batteries should last 3 yrs or more. When my initial batteries finally expire, I'd like to go with some high-tech LiFEPo4 batteries to replace them if they drop sufficiently in price by then. If not, I will use this as an opportunity to upgrade my battery bank to better, more durable FLAs.

Chip   

 

[Artstang]

Hers's my unit I installed a month ago. I don't normally boondock, but you'll never know when you need to. My unit consisted of 2x 100 watts PV, a 30 amp charge controller with a 40 amp resetable breakers wired with 10 ga wire connected to two 12V, 200 min. @ 23 amp Duracell batteries. A 2000 watts inverter with 200 amp ANL fuse is connected to the battery + terminal. For now the panels produces at 10-11.5 amp charge to the batteries on bright sunny days her in NE Florida. A single circuit transfer switch powers the two TV's, DVR, and a coffee maker when used.

 

[hes4all]

My roof

 

[Lou Schneider]

Second group of brain teaser questions.

We might need a Rocket Scientist or at least an Electrical Engineer for this one as it is totally different than the last.

Tomorrow I am buying 6 golf cart batteries for the golf cart.  it seems a shame that thiese cannot have a dual use.  Most of the time they are just sitting unless the golf cart is used, ( very rarely and mostly for grandkids or others grandkids).

Now at a minimum I do know that I get 12 volts from the golf cart battery bank for the lights and horn by using the negative post of battery one and the positive post of battery two.

Is there any way to do the same for batteries 3 and 4 and batteries 5 and 6?

Now right away I do realize that there is a voltage difference between negative post 1 and 3, they are not at the same ground level, (one is ground and the other is 12 volts is respect with ground one.  Also the ground at battery 5 is 24 volt with respect to negative post 1.

Now if I rewire them as one big 12 volt bank using normal series/parallel wiring I can certainly do that but it defeats the purpose of dual use without either switches or rewiring every time.

Question for the Electrical Engineer,  Is there a method for isolating the grounds to eliminate the differing voltage levels in the bank?

Idealy I would add a seperate set of cables just like the way the golf cart currently gets its 12 volt supply, but I would do this to three seperate sets of 2 6 volt batteries.  then I would combine these three 12 volt supplies to a common heavy connector, (like the charger plug to the golf cart).  This connector ideally would allow for supplying 12 volts as well as allowing for the charging of the entire battery bank using either solar panels or a 12 volt battery charger.

Hey, I said it was a brain teaser.  If anyone could do it. it must be this group of boondockers.

Again thanks in advance, at least if gets you thinking about it.

You can't get full battery capacity at 36 volts and 12 volts simultaneously and if you connect a high current draw like an inverter to just one pair of batteries you'll unbalance the battery pack.  If you discharge two batteries more deeply than the others they won't fully recharge unless you recharge them separately.  If you recharge them as part of the 36 volt pack you'll overcharge the others.  That's called an equalizing charge and the remaining batteries will outgass, boil and use water as they're overcharged.

There are two ways to do what you want.  The first is to get a 36 volt inverter and put it across all 6 batteries.  To charge the batteries from your 12 volt system get a 12 volt to 36 volt boost converter.  Or use a separate 12 volt inverter to run your existing 36 volt charger - true sine wave would work best.

Unfortunately, going the other way - converting from 36 volts to 12 volts at high current is expensive, probably due to much less demand.  Browse the Powerstream pages to see what I mean.

Or you could separate the batteries into three pairs of 12 volts each and put an Anderson Power Pole connector on each pair, then make two sets of terminations to change the configuration.

The first termination would be 3 Power Pole connectors in series to connect to the golf cart and restore the original 36 volt series configuration.

The second would have 3 Power Pole connectors wired in parallel for the inverter, so when the battery connectors are plugged in there, you have 3 pairs of batteries in parallel for 12 volts.

You'd just move the 3 battery connectors from one termination to the other to change from golf cart to inverter use.

 

[Kevin Means]

Hey Hes4all...

I see a little white space left on your roof. (Oh I forgot... you still have to have room to walk) 

Kev

 

[hes4all]

Hey Hes4all...

I see a little white space left on your roof. (Oh I forgot... you still have to have room to walk) 

Kev

You funny guy Kevin.

To be honest the last time I was plugged into shore power other than at my home was about 3 years ago and that was because we wanted a little bigger shower and needed water!

We do so much late season camping is why I went with the 900 watts and I don't have to angle them.
I did just up grade my batteries too, to Lipo's.  All I can is wow!

 

[eda239]

What are Lipo's ?? Lithiums?  If so I'm interested in hearing more. What little info published says they are lighter, smaller, safer, able to discharge way below 50% without permanent damage, etc etc.  But the only legit DIY info ( and limited info at that ) was on the Technomadia site where he bought bulk, disassembled and re-soldered the appropriate size, amperage/watts etc. Too much room for error doing that and I prefer something a little closer to "plug-n-play" type install. Would love to hear more about these batteries.
 

 

[Argo]

Have any of you thought of using the Tesla battery pack?  or even investigated it?  They weight 250 lbs and hold quite a bit of energy, enough for a house to run off of.... 

I have two 6v batteries on my new TT and want to hook up a few panels to it.  I have a couple of questions about this.

1)  do charge controllers have multiple ports to plug in multip panels or do you run them in circuit(maybe someone has a good diagram of the wiring for this)

2) when I connect the wiring to the battery I am assuming I put the neg on the end of one battery and the pos on the end of the other battery( I guess the wiring diagram will show that)

3)  has anyone used the Kyocera panels? " KD140SX-UFBS 140W 12V " maybe you guys have a lead on good priced panels that newcomers don't have?  I don't use much power when I am boondocking, I used my truck camper for the past 7 months for boondocking about 5 days a week and really just don't use too much energy but I will now want to run a fridge instead of using block ice..... 

4)  any input on a good control box, not top of the line but a good midline brand?  I hear these are a pretty important part of the system, more so than quality panels.....

Thanks in Advance.

 

[Lou Schneider]

I don't think anyone has used the Tesla Powerwall in an RV - it's liquid cooled, so it has to stay upright and can't be installed on it's back.  At 4 feet tall it's too large to fit in the storage compartments of most RVs.

Worst yet, it's restricted to authorized installers.

I'm anxiously waiting for Musk's Gigafactory to come on line and bring the price of Lithium batteries down to a reasonable level.

Multiple panels are connected in parallel (+ to + and - to -) and then brought down a single pair of wires to the controller.  Make sure the wire is rated to handle the sum of the panel's currents.

In a 12 volt system, 12 volt batteries are connected in parallel so their voltage stays the same.  If you're using 6 volt batteries, you put two in series (+ on one battery to - on the second one) to make 12 volts, then if you have more than 2 batteries you connect the pairs in parallel.

 

[JiminDenver]

Multiple panels can also be connected in parallel by combining the positive leads into one as well as the negative leads so that you have one positive and one negative going into the controller. A combination of things will decide if parallel or series works best for you.

 

[hes4all]

What are Lipo's ?? Lithiums?  If so I'm interested in hearing more. What little info published says they are lighter, smaller, safer, able to discharge way below 50% without permanent damage, etc etc.  But the only legit DIY info ( and limited info at that ) was on the Technomadia site where he bought bulk, disassembled and re-soldered the appropriate size, amperage/watts etc. Too much room for error doing that and I prefer something a little closer to "plug-n-play" type install. Would love to hear more about these batteries.

I meant to say Lithium batteries. I did a 700 amp pack a few months ago.

 

[eda239]

---->hes4all.  I would be very interested in something like that. Did you have to assemble it? Or were you able to purchase it? If so, could you share where you found the lithiums or point us in the right direction? Thanks.

 

[SilverMachine]

Resurrecting:

Has anyone here thought about or experimented with a 48v system?