Solar power

[petarm1]

Still looking at generators, thats a whole nother topic, going to do a lot of sound proofing in that bay

[windtrader]

Depending on how much backup power you need for your solar system, there are several very quiet self-contained generators. Some here have experienced excellent performance and value, no need for added sound abatement.

[petarm1]

I was looking at a honda generator setup that is 2 2000 watt that join together if needed for 4000 watt power. I am really only using the solar and generator as back up power incase of a power outage. Maybe in 5 years when i retire and travel it will be used for off grid parking. But 90 percent of the time i will be pluged into shore power.

[windtrader]

Does your controller allow for inputs from two sources: primary- the generator (AC), secondary - battery bank (DC)?Maybe one 2k gen would be sufficient if the battery bank could take over when the draw exceeds the generator's max output.

[petarm1]

The way i have it planned in my head it should all work together. I like the generator i am chooseing because i could either leave it as a 4000 watt unit, ad a third to make 6000 watts or remove one unit and have it in my camervan as a 2000 watt unit. Which i am also going to put a couple solar panels on.

[neoneddy]

https://www.youtube.com/watch?v=VLzXBOWFM3c   Here is how I installed my solar panels.  I used commercial panels bought for about $.50 / watt.

So I have 1950 watts on the roof, in practice I pull down 1200-1500 watts from the hours of 10 am to 3 pm in full sun.   For a battery bank I have 6 x 12v 205 ah AGM Telecom batteries, for 14,000 kw of battery capacity.  2 Victron 100 / 50a solar chargers - 2 victron multi plus inverters.

As the summer winds down I've  done some reflecting.  I love my solar system, but... it's not been everything I've hoped it would be.  I have plans to improve it.  Here is the thing I've come to learn but never realized.  When you have a big battery bank, you need a way to charge it up in the day plus meet your current energy needs.  I can usually do one or another, both is hard while staying cool.

While traveling this last week we stopped at Mears Beach in Michigan, parked in the parking lot during the day, pulled in enough power to run 1 AC unit while the kids played at the beach and I worked.  It was fine, but we were still sitting at 80% battery from the draw down the night before, we couldn't make up much ground.   

Now here is where a generator can come in, I've made the mistake of trying to get by on a smaller 3-4kw options.  It can work, but it didn't for me.  I tried both a 4kw Onan BFA and a predator 3500 from Harbor Freight.  I think both would work fine, but not when you run them exclusively at their amp limits.   I just this week upgraded to a 7kw Onan, it just fits in the MCI ac condenser bay, it seems to be very happy running 35 amps all day long.

I'm all over the place here, but I feel like I'm trying to talk to myself 2 years ago.   If you don't need or want to run AC from solar / battery, 800 watts might work just fine, but don't plan for more than 600 watts for 4-6 hours a day.   I have 2 more panels to bring my total capacity to 2600 watts, hopefully getting 1600 - 1800 for 4-6 hours a day.  I think that will reduce generator run time while still staying cool.   

Anyway, I think solar is a great way to go, but you'll still need some genny time.  Also make sure to have roof vents, that's another issue, I don't yet. 

[chessie4905]

Good report. Too many solar enthusiasts want to run everything off them. Reefer, ac, and enough left over to supply the nearest city. I think they are fine for battery charging and refer and small fans, but it starts getting complicated when you want do do cooling or heating, especially with any sunlight issues and limit to roof space. Great for western US, but here in the east, there are a lot of cloudy days reducing potential output. Maybe a pull behind trailer with a folding out panel array would be a consideration.

[lostagain]

Some solar on a motorhome is a great addition to the electrical system. However, it is not as good as some people dream it is. I have 700 watts on the roof and 8 6 volt batteries. It helps a lot when the sun shines high and bright. But if it is cloudy, or winter up North, or in the shade (you don't always have a choice of where to park), it doesn't do s..t. So, as has been mentioned above, you need a generator, 6 or 8 kw minimum.

JC

[petarm1]

All good things i am reading. The plan for the bus is 3 a/c units and 4 maxx air on the roof. Heating will be done with the a/c and baseboard heaters. The solar and generator  are backup units incase power goes out. I need to run at least one of the a/c or the fans in the summer, and if a winter power outage happens at least the  mid bus baseboard heaters. I was thinking of just getting one large generator but the place to put it is the problem since i am keeping the factory airconditioner. Just removing the upper compartment a/c from the bus. Appreciate all the comments on the subject.
Thanks

[buswarrior]

The trick is in the blending. no single way is going to work well alone.

And any discussion about these "power acquisition" strategies cannot help but be disjointed blurbs...!

Batteries and Solar are tough ways to do the heavy lifting of heating and cooling, there's a lot of energy needed for HVAC purposes.

A generator or a power pole are really good at heavy lifting.

However, a generator is not a good use for topping off batteries. Lots of batteries have been murdered by busnuts who kept them perpetually discharged because they didn't ever get them back to 100%. Run time on the generator to accomplish this is very long, relatively speaking.

Modern house refrigerators are using very little power compared to only a few years ago, so a new house refrigerator running via an inverter off the batteries is a lot more viable today, than it was a shorter time ago. If you haven't, go look at the labels on new refrigerators, a couple of amps at most for many of them!

So how big do you go with solar? Well, how about size the solar to reasonably recover an overnight of refrigerator running and those couple of lights, CPAP etc.

If you are camping in pleasant temps, that's all you really consume in power.

If you run the generator for anything, it will be putting power back into the batteries while you cook, dry hair, HVAC, etc.

The generator doesn't have to be run to just charge batteries, the solar panels can "put the polish" onto the bank, and get it to 100% pretty much every day.

Solar is also VERY good for keeping the batteries healthy during times of storage.

Those couple of solar panels and decent charge controller will likely pay you back in the battery budget, as your batteries should live a longer and healthier life.

Don't aim for everything, aim for something, several ways?

happy coaching!
buswarrior

[windtrader]

Sean,
Thanks for the introspective and insightful update on your solar experience and system design. Solar is still on my list, just not near the top. I'm considering lithium batteries, more as prices keep generally trending lower.
Using lithium for storing for solar generated energy in a bus conversion offers enough benefits to be considered.

Lithium charges faster.1C is generally a good general max charge rate for LiFePo4. Using 5 hours daytime sun as the primary energy collection period, this battery can be charged up.

Lithium has greater capacity and depth of discharge. With increased usable watts, fewer batteries are required, weigh less, and battery bank takes less space.
Lithium should last longer with 1000 charge cycles.

Lithium is more costly. This battery is 12v x 100ah, about 1200 watts capacity, usable 800 watts (2/3 DOD). Four of them makes a battery pack with 24v x 200ah, 4800w max/3200w usable. This seems sufficient for running everything except the AC. Something like this runs around $3000.

I'm not making the argument that solar can do it all, all the time, but it seems like running the AC via the generator, even a smaller one, bridges the gap to keep the battery bank charged up or at least enough to supply energy for the bus.

https://www.batteryspace.com/lifepo4-rechargeable-battery-12-8v-100ah-1269-7wh-100a-rate-with-bluetooth-option---un38-3-passed.aspx Features 

Battery	Replace Lead Acid Battery with lighter weight and Higher Capacity
Voltage	Nominal Voltage: 12.8V; Charge Voltage: 14.40±0.25V Discharge end of Voltage: 11V±0.1V (2.75V/cell) Overdischarge  protection voltage :8.8V±0.1V (2.2V/cell)
Capacity	Typical: 100Ah; Minimum: 96.2Ah @0.2C discharge
Charge Current	Standard: 20A  Maximum: 99.2A
Charge Time	Standard: 5-7 hrs Maximum: 2-3 hrs
Discharge Current	Standard: 20A Maximum Continues: 100A Maximum Surge: 150A
Internal Resistance	<20mΩ; AC Impedance 1KHz
Weight	Net Weight: 33 LB (15Kg); Shipping Weight: 35LB (16Kg)
Temperature	Charge: 0 to 40°C Discharge: -20 to 60°C Storage: 1 month: -20 to 60°C; 3 month: -20 to 45°C; 1 Year: -20 to 20°C
Dimension	With Connector 13" x 6.8" x 8.75" (340mm x 173mm x 222mm) Without Connector 13" 6.8" x 8.25" (340mm x 173mm x 210mm)
Terminal	Copper Pillar, DiaxH : 19x30mm
Charger Option	You can purchase 12.8V 15A LiFePO4 charger for this battery with CAN Communication switch overrided 'ON'
Notes	Can be connected in series upto 4S and unlimited in parallel Must use LiFePO4 charger to charge each module. Do not use Lead Acid charger to charge this battery. There are some milliampere consumption due to digitlal output, please maintenance it on time base on its remaining capacity to prevent it from over-discharge. This battery must be shipped by Class 9 package, and there is extra handling fee, please add handling fee into shopping cart        Ship with US address: handling fee Ship to Canada address: Please choose UPS Standard

[richard5933]

What do you do with the lithium batteries in the cold weather?

My wet cell batteries stay put all year - I just keep them plugged in and charged. This allows for us to use the bus and camp as long into the winter fall as we dare. Our wet bay is heated to keep the water flowing, but our battery bank is not.

From the information you posted the lithium don't seem to like the cold (assuming my C to F translation is accurate). Would they need to be pulled when the temps gets below freezing? Or, are there setups which include heaters just for the batteries?

[neoneddy]

Don't get me wrong,  I don't regret the solar one bit, I still plan to expand it.   I've not known rving without batteries and solar.  I don't think I'd like having to run a genny all the time like I've seen many other campers in no hookups campsites.

On batteries.   I forget if I mentioned, but I went to some telecom cells this year.  They are still lead acid technology, but AGM cells handle deeper discharges and faster charge acceptance.  They also seem to have better cold weather performance than typical flooded lead acid.  I found these for $160/ea  hard to beat that.

I went with these batteries in part because of the cold weather worries of lithium.  Now from what I gather the issue with freeing temps and lithium is more on the charge side than discharge side.  As luck would have it, if you discharge them they heat up.  So, if I had a good sized lithium bank, I could run the electric hot water heater to draw enough amps to heat them up above freezing.  Then I could charge them which would continue to warm them.   I suspect if they are getting cycled daily, it would be difficult to get them below freezing in even below 0 temps inside a bay with just a  thermal blanket for insulation.

One downside to mysetup and an upside to lithium is not needing to be fully charged, my AGM cells need a full charge every 2-3 days, that can be hard if it's cloudy.  Now I usually hit 28v at some point, but they really need to see that for 2-3 hours or more for a full charge.

That said even at $650 per 100ah @12v I can't justify lithium, when I'm buying 200ah @12v for $150.  I know AGMs should only be used to 50%, but even at that, it's less than 1/2 the cost... aaaand in a pinch I can go past 50%  without much damage if I recharge shortly after.   I've done a 90% capacity test with no measurable loss of capacity.

[windtrader]

Keeping Li batteries in the recommended operating range is addressed by electric motor vehicle designers. Seems like you need to keep the batteries in a heated compartment. It would not take much to keep it warm given the small volume of the storage compartment. In my case, the bus is fully equipped for cold weather. Electric heating wire on all externally exposed piping, hot water radiators in all bays connected to webasto, and engine block heater.

[chessie4905]

Lithium sound like the perfect solution...in probably 7 to 15 years. Too expensive, too fussy as to recharging and temps in our situation. As well as they work in compact drills, phones, and other items, they are very impressive. Maybe sooner. Look how far solar has come in a few years. The way the voltage output is climbing in these larger hand held items, shouldn't  be too long till they are up to 120 volt. When that time comes, I wonder how many it would take to run one rooftop air conditioner. Just line up as many batteries with their own chargers as needed, wire them to output while still in their respective chargers, and cut output and turn chargers on to recharge. I know that is an elaborate way to do it, but would be an easier way to get started.