off grid solar discussion

17 views
Skip to first unread message

James Manley

unread,
Mar 19, 2020, 4:27:58 PM3/19/20
to atxhs-...@googlegroups.com
recently I've been looking into off-grid solar setups.

was wondering who at the space has had experince with setting up solar power systems, what equipment y'all have used, and what capacity your systems have.

Charles Wyble

unread,
Mar 19, 2020, 4:42:01 PM3/19/20
to atxhs-...@googlegroups.com
How many kwh do you need?

What’s your capex budget ? 50k? 100k?

It’s not cheap. 


On Mar 19, 2020, at 15:28, James Manley <jamesma...@gmail.com> wrote:


recently I've been looking into off-grid solar setups.

was wondering who at the space has had experince with setting up solar power systems, what equipment y'all have used, and what capacity your systems have.

--
You received this message because you are subscribed to the Google Groups "ATXHS Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email to atxhs-discus...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/atxhs-discuss/CAOL5BA2isiBTQp59Tchr4OFJq9D%3DaMv9OwwABERPUp6DzYpuNw%40mail.gmail.com.

Danny Miller

unread,
Mar 19, 2020, 5:01:14 PM3/19/20
to atxhs-...@googlegroups.com
Jay really opened my eyes on the cost-effectiveness of reusing salvaged Tesla battery modules.  ~$1000 for a 5.2kwh 24v.  It is possible to reconfigure as 12v and often that's a good idea.

When managed properly, these packs will last basically forever even if you run them all the way down and fast charge them all the time, and 5.2kwh is quite a lot to work with.  By contrast, the biggest deep cycle lead acid battery is about 1.2kw, but in practice you don't want to cycle them that deeply, so you might derate it to about half that in practical use, and still, they're not all that reliable in the long run.

But it's hardly the only option, salvaged Nissan Leaf G2 cells are also huge, cost effective, and reliable.  

Other options keep coming up, as tech is moving so fast.  So much that "slack factor" comes up.  i.e. spending a lot on a setup now with cells that could be expected to last 20+ years could be superceded by an option that costs less and has twice the capacity or otherwise obsoletes it within even a year or two.

Interfacing with common inverters may be a problem.  I have long been a fan of Xantrex Xpower on lead-acid batteries, which has a specified range of 15v-11v (alarm at 11v, auto-shutdown at 10.5v).  The range of a 4-cell lithium pack is 16.8v to 10v if you use the entire capacity.  Shutting down at 2.75v/cell is not any loss, that's pretty much fully discharged past 3.2v anyhow.  However, charging only to 3.75v instead of 4.2v would be failing to use a substantial amount of capacity as it's far from full charge at that point.  Putting such an inverter on a 16.8V battery, that's a tough question.  It may run just fine, but being outside ratings, it may die an early death, or behave oddly, and what ultimately happens may vary greatly from unit to unit as, say, the input caps may not have been from the same manufacturer from year to year.

There is of course inverter hardware specifically designed for lithium voltages, but I don't see it coming up cheap and common yet.

Danny



On Thu, Mar 19, 2020 at 3:27 PM James Manley <jamesma...@gmail.com> wrote:
recently I've been looking into off-grid solar setups.

was wondering who at the space has had experince with setting up solar power systems, what equipment y'all have used, and what capacity your systems have.

--

Jack Foy

unread,
Mar 19, 2020, 6:10:43 PM3/19/20
to atxhs-...@googlegroups.com
I put together a 2.4kW array to power my travel trailer on some property I own. Panels were ~ .35/W with two 60A MPPT charge controllers (~$180 ea.) and Aims 3000W, 24V input pure sine inverter ($950) and 4 flooded lead-acid 6V floor scrubber batteries, 235Ah @20hr rate (~$110 each).
Inverter info:
POWERFUL: 3000W continuous, 9000W surge for 20 seconds, 24VDC, 25 amps, 120VAC pure sine clean power, low frequency, auto transfer switch and 40A smart battery charger for 8 different battery technologies including lithium. 
 
With miscellaneous wire, connectors etc. call it $3000 total. I still need a generator at night if I use the AC but it handles the full trailer AC and all in July during the day

The deal of the day was buying panels from Kinect Solar. They buy loose lots from big solar projects leftovers and resell them I got five 315W 72 cell panels for $85 ea. then three more of the same type at a later buy for $110 each.

Lessons learned: I don't have enough capacity and will need to add more batteries. If I had done that up front, I could have opted for a 48V inverter and only used one charge controller. The Tesla (or Prius) used batteries would also have been a smarter choice.


To view this discussion on the web visit https://groups.google.com/d/msgid/atxhs-discuss/CAPSfvmOdGWvMcHJKJ7miQa8eGUgcnaDf1ZEiGKsV92g2ARsCiQ%40mail.gmail.com.

Dan DeFelippi

unread,
Mar 21, 2020, 11:34:39 AM3/21/20
to ATXHS Discuss
To add to what Jack said, if you plan on getting <100A from your panels and never expanding, 12V would be a reasonable option. Once you get around 100A or more you should run at least 24V if not 48V.

I built my bus' system at 12V since it's the easiest to do. It also allows me to charge directly off my alternator. But that was with 800W of solar. After expanding to 1800W I can easily max out my 100A solar controller. It also means I can't get Tesla or other used batteries without modification since they're all in 24V+ configurations. Higher voltage also means smaller wiring, lowering costs.

Much like buying a car used panels and batteries are the best way to go. You'll pay half as much used, if not less.


On Thursday, March 19, 2020 at 5:10:43 PM UTC-5, Jack Foy wrote:
I put together a 2.4kW array to power my travel trailer on some property I own. Panels were ~ .35/W with two 60A MPPT charge controllers (~$180 ea.) and Aims 3000W, 24V input pure sine inverter ($950) and 4 flooded lead-acid 6V floor scrubber batteries, 235Ah @20hr rate (~$110 each).
Inverter info:
POWERFUL: 3000W continuous, 9000W surge for 20 seconds, 24VDC, 25 amps, 120VAC pure sine clean power, low frequency, auto transfer switch and 40A smart battery charger for 8 different battery technologies including lithium. 
 
With miscellaneous wire, connectors etc. call it $3000 total. I still need a generator at night if I use the AC but it handles the full trailer AC and all in July during the day

The deal of the day was buying panels from Kinect Solar. They buy loose lots from big solar projects leftovers and resell them I got five 315W 72 cell panels for $85 ea. then three more of the same type at a later buy for $110 each.

Lessons learned: I don't have enough capacity and will need to add more batteries. If I had done that up front, I could have opted for a 48V inverter and only used one charge controller. The Tesla (or Prius) used batteries would also have been a smarter choice.


On Thu, Mar 19, 2020 at 4:01 PM Danny Miller <da...@atxhs.org> wrote:
Jay really opened my eyes on the cost-effectiveness of reusing salvaged Tesla battery modules.  ~$1000 for a 5.2kwh 24v.  It is possible to reconfigure as 12v and often that's a good idea.

When managed properly, these packs will last basically forever even if you run them all the way down and fast charge them all the time, and 5.2kwh is quite a lot to work with.  By contrast, the biggest deep cycle lead acid battery is about 1.2kw, but in practice you don't want to cycle them that deeply, so you might derate it to about half that in practical use, and still, they're not all that reliable in the long run.

But it's hardly the only option, salvaged Nissan Leaf G2 cells are also huge, cost effective, and reliable.  

Other options keep coming up, as tech is moving so fast.  So much that "slack factor" comes up.  i.e. spending a lot on a setup now with cells that could be expected to last 20+ years could be superceded by an option that costs less and has twice the capacity or otherwise obsoletes it within even a year or two.

Interfacing with common inverters may be a problem.  I have long been a fan of Xantrex Xpower on lead-acid batteries, which has a specified range of 15v-11v (alarm at 11v, auto-shutdown at 10.5v).  The range of a 4-cell lithium pack is 16.8v to 10v if you use the entire capacity.  Shutting down at 2.75v/cell is not any loss, that's pretty much fully discharged past 3.2v anyhow.  However, charging only to 3.75v instead of 4.2v would be failing to use a substantial amount of capacity as it's far from full charge at that point.  Putting such an inverter on a 16.8V battery, that's a tough question.  It may run just fine, but being outside ratings, it may die an early death, or behave oddly, and what ultimately happens may vary greatly from unit to unit as, say, the input caps may not have been from the same manufacturer from year to year.

There is of course inverter hardware specifically designed for lithium voltages, but I don't see it coming up cheap and common yet.

Danny



On Thu, Mar 19, 2020 at 3:27 PM James Manley <jamesma...@gmail.com> wrote:
recently I've been looking into off-grid solar setups.

was wondering who at the space has had experince with setting up solar power systems, what equipment y'all have used, and what capacity your systems have.

--
You received this message because you are subscribed to the Google Groups "ATXHS Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email to atxhs-discuss+unsubscribe@googlegroups.com.

--
You received this message because you are subscribed to the Google Groups "ATXHS Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email to atxhs-discuss+unsubscribe@googlegroups.com.

Kevin Hilliard

unread,
Mar 21, 2020, 1:23:56 PM3/21/20
to atxhs-...@googlegroups.com
Hi James,

I worked at both residential and commercial capacity in Solar for 5 years. I was employed with Tesla up until 2019, working as a specialist in battery backup systems. 
There are many different options you can move forward with; however, it's easier to plan a best course of action if you have a clear understanding and definition of your NEEDS. 
A system complete off-grid has additional difficulties that might not be present with a grid-tied system. Share some details about your project so I can get an understanding of what you're looking to achieve.

Cheers,
Kevin

On Sat, Mar 21, 2020 at 10:34 AM Dan DeFelippi <d...@driverdan.com> wrote:
To add to what Jack said, if you plan on getting <100A from your panels and never expanding, 12V would be a reasonable option. Once you get around 100A or more you should run at least 24V if not 48V.

I built my bus' system at 12V since it's the easiest to do. It also allows me to charge directly off my alternator. But that was with 800W of solar. After expanding to 1800W I can easily max out my 100A solar controller. It also means I can't get Tesla or other used batteries without modification since they're all in 24V+ configurations. Higher voltage also means smaller wiring, lowering costs.

Much like buying a car used panels and batteries are the best way to go. You'll pay half as much used, if not less.


On Thursday, March 19, 2020 at 5:10:43 PM UTC-5, Jack Foy wrote:
I put together a 2.4kW array to power my travel trailer on some property I own. Panels were ~ .35/W with two 60A MPPT charge controllers (~$180 ea.) and Aims 3000W, 24V input pure sine inverter ($950) and 4 flooded lead-acid 6V floor scrubber batteries, 235Ah @20hr rate (~$110 each).
Inverter info:
POWERFUL: 3000W continuous, 9000W surge for 20 seconds, 24VDC, 25 amps, 120VAC pure sine clean power, low frequency, auto transfer switch and 40A smart battery charger for 8 different battery technologies including lithium. 
 
With miscellaneous wire, connectors etc. call it $3000 total. I still need a generator at night if I use the AC but it handles the full trailer AC and all in July during the day

The deal of the day was buying panels from Kinect Solar. They buy loose lots from big solar projects leftovers and resell them I got five 315W 72 cell panels for $85 ea. then three more of the same type at a later buy for $110 each.

Lessons learned: I don't have enough capacity and will need to add more batteries. If I had done that up front, I could have opted for a 48V inverter and only used one charge controller. The Tesla (or Prius) used batteries would also have been a smarter choice.


On Thu, Mar 19, 2020 at 4:01 PM Danny Miller <da...@atxhs.org> wrote:
Jay really opened my eyes on the cost-effectiveness of reusing salvaged Tesla battery modules.  ~$1000 for a 5.2kwh 24v.  It is possible to reconfigure as 12v and often that's a good idea.

When managed properly, these packs will last basically forever even if you run them all the way down and fast charge them all the time, and 5.2kwh is quite a lot to work with.  By contrast, the biggest deep cycle lead acid battery is about 1.2kw, but in practice you don't want to cycle them that deeply, so you might derate it to about half that in practical use, and still, they're not all that reliable in the long run.

But it's hardly the only option, salvaged Nissan Leaf G2 cells are also huge, cost effective, and reliable.  

Other options keep coming up, as tech is moving so fast.  So much that "slack factor" comes up.  i.e. spending a lot on a setup now with cells that could be expected to last 20+ years could be superceded by an option that costs less and has twice the capacity or otherwise obsoletes it within even a year or two.

Interfacing with common inverters may be a problem.  I have long been a fan of Xantrex Xpower on lead-acid batteries, which has a specified range of 15v-11v (alarm at 11v, auto-shutdown at 10.5v).  The range of a 4-cell lithium pack is 16.8v to 10v if you use the entire capacity.  Shutting down at 2.75v/cell is not any loss, that's pretty much fully discharged past 3.2v anyhow.  However, charging only to 3.75v instead of 4.2v would be failing to use a substantial amount of capacity as it's far from full charge at that point.  Putting such an inverter on a 16.8V battery, that's a tough question.  It may run just fine, but being outside ratings, it may die an early death, or behave oddly, and what ultimately happens may vary greatly from unit to unit as, say, the input caps may not have been from the same manufacturer from year to year.

There is of course inverter hardware specifically designed for lithium voltages, but I don't see it coming up cheap and common yet.

Danny



On Thu, Mar 19, 2020 at 3:27 PM James Manley <jamesma...@gmail.com> wrote:
recently I've been looking into off-grid solar setups.

was wondering who at the space has had experince with setting up solar power systems, what equipment y'all have used, and what capacity your systems have.

--
You received this message because you are subscribed to the Google Groups "ATXHS Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email to atxhs-discus...@googlegroups.com.

--
You received this message because you are subscribed to the Google Groups "ATXHS Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email to atxhs-discus...@googlegroups.com.

--
You received this message because you are subscribed to the Google Groups "ATXHS Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email to atxhs-discus...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/atxhs-discuss/cd5f991a-8d06-4667-9e59-aca31af44733%40googlegroups.com.

James Manley

unread,
Mar 21, 2020, 2:45:54 PM3/21/20
to atxhs-...@googlegroups.com
I still live with my folks so not currently able to do anything, more just a curiosity I look into every now and then.

But i have had a interest in trying to get a tiny home in a couple years. so was wondering how much power those in a tiny home tend to use, and what their systems look like.

As far as the power usage i have where i live it ranges from as high as 2600 KWH in August to as low as 700 KWH in February

I am a bit of a doomsday prepper, so i try to think of complete off grid solutions when i can. The issue i have with grid tie systems is that they usually require that your system go offline if the grid goes down for the safety of utility workers.

I looked into the tesla power wall before and found that they required a network connection to function, which seems silly to me lol.

made a bit of a spreadsheet with the info ive thought about

To view this discussion on the web visit https://groups.google.com/d/msgid/atxhs-discuss/CAJ_PZ2uFgZANNVXyGjkvR7JyYy%3D3zy4Om%3DU5M7koV5ygmrcn3w%40mail.gmail.com.

Dan DeFelippi

unread,
Mar 21, 2020, 8:29:46 PM3/21/20
to atxhs-...@googlegroups.com
Unless you want to spend tens of thousands on a big system you'd want to cut your power use to 10-20% of that.

--
Dan DeFelippi
http://driverdan.com


You received this message because you are subscribed to a topic in the Google Groups "ATXHS Discuss" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/atxhs-discuss/qwzouimrMH4/unsubscribe.
To unsubscribe from this group and all its topics, send an email to atxhs-discus...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/atxhs-discuss/CAOL5BA1oQCibfx-fhMeJU5s-PfSkrdtsDdNwU7Hrc03hoCKbSQ%40mail.gmail.com.

Ben Johnson

unread,
Apr 7, 2020, 11:57:52 AM4/7/20
to atxhs-...@googlegroups.com
Hey everyone,

I'm self quarantined in my campervan, and my agm batteries  just died and my modified sine wave inverter  caught fire when I attempted to charge the batteries last night.

I'm looking to buy a lithium ion battery by renogy and have a brand new samlex pure sine wave inverter. Unfortunately I dont have the expertise when it comes to this stuff or the education and I am afraid to do tje installs all myself but really need it done asap.

If anyone is willing to help me install my new setup/educate me for the future I would gladly pay for your time of course.

I know its alot to ask given the current situation but I really could use the help and maybe can help someone else in turn.

Thanks 

Ben Johnson 

To view this discussion on the web visit https://groups.google.com/d/msgid/atxhs-discuss/CA%2Bvo8J4CAHApE%2BZbfxpQjG1V8cD1uSsi9UtG4E2VFHiTTJRYHw%40mail.gmail.com.
Reply all
Reply to author
Forward
0 new messages