Ready for Lithium and Solar - advice?

[pteck]

There's a lot of opportunity to gain more efficiency with the various devices in the trailer. From TV, to fans, etc.

The Fantastic Fans stock can only run in low mode down to ~1.9 amps draw. Yet they are relatively easy to upgrade with various strategies, down to .2amps per hour.

Some strategies can be found here:
https://littleguy.vanillacommunities...0-model-or-kit

[TouringDan]

Originally Posted by pteck

Using reasonable depths of discharge per battery types:

A 230Ah golf car battery pair is about 160Ah usable.

A pair of lithium 100Ah batts rated for 200Ah is also about 160Ah usable.

pteck

I believe the accepted reasonable depth of discharge for golf cart batteries is 50% which results in 115 Ah usable not 160 Ah.

Dan

[pteck]

Originally Posted by TouringDan

pteck

I believe the accepted reasonable depth of discharge for golf cart batteries is 50% which results in 115 Ah usable not 160 Ah.

Dan

The 50% guidance is for typical 12V hybrid or deep cycle batteries. There is more to this story.

With higher quality flooded batts or heavy duty 6V golf cart batts, there is the opportunity to utilize more reserve capacity.

With any battery, lithiums included, there is a sliding scale between depth of discharge (DoD) and cycle life.

6V golf cart batts are known to have upwards of 3x the cycle life of common 12V batteries at 50% DoD (~700 cycles vs. ~250 cycles). So the opportunity is to have more usable capacity. At 80% depth of discharge, there is still more cycle life in a 6V golf cart battery, than a common 12V battery.

I was being conservative with my numbers before. I'm wholly comfortable utilizing upwards of 180Ah+, while still getting great battery life. I'm not saying to run it deep like this every day, but there is emergency reserves to the full 230Ah. I consider that a "feature" of wet cell batts.

When you consider the negligible cost of 6V batts and ease to source and replace, especially versus lithiums, I'm comfortable running them deep if for example I want heat through a cold night. Rather than babying my batteries that may not have been well charged the day before. It happens. With the cost investment, I sure wouldn't treat lithiums like that. Lithiums are selfish anyways and will cut you off with their BMS. Leaving one perhaps "out in the cold", on a frigid night.

[TouringDan]

Originally Posted by pteck

The 50% guidance is for typical 12V hybrid or deep cycle batteries. There is more to this story.

With higher quality flooded batts or heavy duty 6V golf cart batts, there is the opportunity to utilize more reserve capacity.

With any battery, lithiums included, there is a sliding scale between depth of discharge (DoD) and cycle life.

6V golf cart batts are known to have upwards of 3x the cycle life of common 12V batteries at 50% DoD (~700 cycles vs. ~250 cycles). So the opportunity is to have more usable capacity. At 80% depth of discharge, there is still more cycle life in a 6V golf cart battery, than a common 12V battery.

I was being conservative with my numbers before. I'm wholly comfortable utilizing upwards of 180Ah+, while still getting great battery life. I'm not saying to run it deep like this every day, but there is emergency reserves to the full 230Ah. I consider that a "feature" of wet cell batts.

When you consider the negligible cost of 6V batts and ease to source and replace, especially versus lithiums, I'm comfortable running them deep if for example I want heat through a cold night. Rather than babying my batteries that may not have been well charged the day before. It happens. With the cost investment, I sure wouldn't treat lithiums like that. Lithiums are selfish anyways and will cut you off with their BMS. Leaving one perhaps "out in the cold", on a frigid night.

pteck

Thanks for the education. I had no idea. Maybe that is why my 2 Sam’s Club golf cart batteries lasted 8 yrs before I replaced them with 2 BB lithium’s.

Dan

[AirMiles]

Originally Posted by pteck

https://littleguy.vanillacommunities...0-model-or-kit

1) Excellent link about making the Fantastic Fan draw less power. If it as simple as adding the resistor (its not), I would do this. But based on the $200 upgrade kit cost, I'll just stick with my original fans. My 400W of solar can run the fans 24 hrs/day plus completely charge my batteries by evening, so they only use half of the Amps from the battery at night and half of the Amps are provided by the excess power being generated by my solar during the day. On dark days and/or with full tree canopy, the lower Amp draw would be beneficial. But that happens so rarely that I'm willing to run the generator on the few days per year when that happens.

2) On the topic of how low you can discharge Golf Cart Batteries, I agree that 80% draw downs are fine for golf cart batteries. See post 17 above for my full explanation: http://www.airforums.com/forums/f37/...ml#post2222745 . "I treat my $200 Golf Cart battery bank like I treat propane exchange tanks. When they run out of juice I replace them." Even after boondocking with this attitude for 130 days, my batteries still test and perform as new.

[pwlldvd]

I used the Victron BMV to measure dc current draws and got the following. DC amps. Running on low if there is a choice.

ItemDC Running/Low
Hair Dryer108.3
Microwave87.5
Furnace7.3
Water Pump5.5
TV3.3
Stove Fan1.9
Inverter1.7
Radio0.6
Fantastic Fan0.6
Lights: Sink0.4
Lights: Stove0.4
Refrigerator0.3
Lights: Stem each0.3
Lights: Closet0.2
Lights: Puck each0.2
Lights: Door0.2
Awning On, Idle0.2
Lights: Door handle0.1
Lights: Awning0.1
Lights: Cieling0.0
Stove0.0
Tank Monitor0.0
Thermostat0.0

[pwlldvd]

Air miles,

Looks like we have similar numbers on the furnace. I timed it running about a third of the time on nights in the 30s or low 40s. We don’t run it 24 hours, and that’s where I get 34 ah per day. Also matches the amp draw observed from when we go to bed til we get up.

[pwlldvd]

So I’ve been talking to AM Solar for advice. They put together their kits to do what I want, for a price not much more than the parts I would have to order myself. It looks like an easier install plus everything will be on the inverter so if we do decide to run the a/c for a few minutes, we can. Sounds crazy but we make all our own meals and sometimes when on the road the trailer can be crazy hot at lunchtime.

Anybody used their kits? They look very complete.

[AirMiles]

I used AM Solar for my complete solar installation, panels, mounts, solar converter and cabling. I felt their pricing was great, their kits were complete, and their support was priceless. I would highly recommend purchasing a complete kit from AM Solar.

Also, thanks for the Amp loads. I just used a clamp Amp meter to get my readings.

[lewster]

Originally Posted by pwlldvd

So I’ve been talking to AM Solar for advice. They put together their kits to do what I want, for a price not much more than the parts I would have to order myself. It looks like an easier install plus everything will be on the inverter so if we do decide to run the a/c for a few minutes, we can. Sounds crazy but we make all our own meals and sometimes when on the road the trailer can be crazy hot at lunchtime.

Anybody used their kits? They look very complete.

AM Solar's stuff is great! I use their components exclusively in my installs. You can't go wrong!

[rmkrum]

Ditto. We have a kit that’s been in and on our Airstream since before 2013. Works solid and manages our batteries well.

Only issue was at some point having the temperature sensor wire fall out of the battery box, drag on the road for hundreds of miles, and basically vanish. One call to AMSolar got a replacement sensor, installation instructions and all parts to put it all back together and operational. My fault for not properly securing the sensor and wiring when I installed the original kit.

Highly recommended!

[pwlldvd]

It’s been almost a year and I thought I should post an update on the results of my upgrade. We’ve had two trips to report on, one without much sun, the next with full sun.

First trip (shade)
After spending several weeks on the install, we left on our trip to volunteer in a national park for almost three months with water and sewer only, no electric, internet or phones.

Our campsite was in tall trees with maybe 2 to 3 hours direct sun a day. The system worked well. We could go 4 or 5 days before firing up the generator. That’s without really thinking much about conserving energy. A typical days use included:

Furnace 8 hours (it was cold at 7500 feet ASL). This was by far the biggest drain, about 15% of AH capacity.

Satellite/TV 4 hours
Microwave 15 minutes.
Lights whenever we felt like it
Coffee pot 1 hour.

Also:
Hair dryer 10 minutes every 3-4 days
Recharging the ancient park radio every 2 or 3 days, for 6 hours on AC.

Conservation measures: not much except to turn the inverter off whenever possible.

Second trip ( full sun)
This time to sunny California for a shorter trip.
Usage was pretty much the same, but we had full sun at a state beach with no hookups at all. Maybe a little less furnace time with 50 degree nights instead of 40 degrees.

In full sun we would deplete the batteries about 15 to 20% each evening through breakfast (same routine as before). The system fully recharged every day (100%). We were gone most days but the couple of times I checked around 2:00 pm the batteries were already 100%.

So happy I did the conversion.

Self install was a lot of work. Mostly it went well. I did drill through some wiring in the ceiling. @#$&. Lights in the cabinet over the bed still don’t work. Oh well.

If I had it to do over again I would hire a pro. But no regrets!

[AirMiles]

Originally Posted by pwlldvd

It’s been almost a year and I thought I should post an update on the results of my upgrade. We’ve had two trips to report on, one without much sun, the next with full sun.

First trip (shade)
After spending several weeks on the install, we left on our trip to volunteer in a national park for almost three months with water and sewer only, no electric, internet or phones.

Our campsite was in tall trees with maybe 2 to 3 hours direct sun a day. The system worked well. We could go 4 or 5 days before firing up the generator. That’s without really thinking much about conserving energy. A typical days use included:

Furnace 8 hours (it was cold at 7500 feet ASL). This was by far the biggest drain, about 15% of AH capacity.

Satellite/TV 4 hours
Microwave 15 minutes.
Lights whenever we felt like it
Coffee pot 1 hour.

Also:
Hair dryer 10 minutes every 3-4 days
Recharging the ancient park radio every 2 or 3 days, for 6 hours on AC.

Conservation measures: not much except to turn the inverter off whenever possible.

Second trip ( full sun)
This time to sunny California for a shorter trip.
Usage was pretty much the same, but we had full sun at a state beach with no hookups at all. Maybe a little less furnace time with 50 degree nights instead of 40 degrees.

In full sun we would deplete the batteries about 15 to 20% each evening through breakfast (same routine as before). The system fully recharged every day (100%). We were gone most days but the couple of times I checked around 2:00 pm the batteries were already 100%.

So happy I did the conversion.

Self install was a lot of work. Mostly it went well. I did drill through some wiring in the ceiling. @#$&. Lights in the cabinet over the bed still don’t work. Oh well.

If I had it to do over again I would hire a pro. But no regrets!

What did you actually install? 400W or 600W? 200AH or 400AH? I assume multiplus and sub-panel. On new rooftop box and heavy gauge wire or prewire? I looked through the thread and never saw what you actually installed.