M Rives

pollinator
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since May 07, 2021
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Electrical engineer living off grid.
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Recent posts by M Rives

John Weiland wrote:

larry kidd wrote:
Also, my impression is that 48V battery systems are winning out in the popularity battle for alt-energy based systems for home, cabins, etc.  Yet I can see advantages of 24V systems...especially with LiFePO4 batteries....when considering weight and safety.  In my case, I'm potentially looking at a 10 kW hybrid inverter/charger with solar, but initially only for a few critical items like well pump and propane furnace and a few light circuits. Only rarely would the batteries be drawn down to 50% with ample anticipated time to recharge before needing again.  The inverter system and batteries would be wall-mounted in a basement ranging from 50F to 65F winter to summer and ~2 kW of solar PV capacity used for charging. About 30 ft of cabling would separate the PV panels from an MPPT charge controller. So to be clear, this would be an introductory backup system for when grid power failure occurs.  Is there some reason that for such a system I should go with 48V instead?  Thanks!



A 10kW inverter will draw about 400A at 24V at full load. It will only draw about 200A at 48V. Generally the charge and discharge current for LiFePO4 batteries should not exceed their amp-hour rating. For example, Eve 280AH cells should not be charged or discharged at more than 280A maximum, 140A nominal. You would need multiple battery packs in parallel and some really big wire to support a 400A discharge rate in a 24V system. A 400A disconnect / breaker  would also be required. Charging will not be a problem with a 2kW solar array since it would only charge at about 80A at 24V or 40A at 48V. Keeping the charge current well below the maximum will reduce heating. Excess heat is one of the biggest factors in reducing LiFePO4 battery life.

LiFePO4 batteries will degrade not only as the cycle count increases but also based on their calendar age. The battery capacity will decline over time even if it is not cycled. I hope to get more than 10 years usage at a reduced capacity but the actual longevity of the Eve cells is hard to pin down.

In our off-grid location the winter days are short and often overcast. The backup generator had to run much more often and longer with the prior lead acid battery bank. If lead acid batteries are not fully charged on a regular basis (maybe every 5-7 days?) sulfate will accumulate on the lead plates reducing the battery capacity. They can be over-charged (equalized) to counteract this effect somewhat but it is best to fully charge them on a regular basis. They also require a relatively long absorption time during which the charge current is continually dropping. This means the generator runs a long time at a partial load which is not as fuel efficient as running at full load. In contrast, the LiFePO4 batteries are happy running from 20% to 80% which means the generator does not have to run as often. For example, I might run it for an hour or two in the evening every few days while waiting for a sunny day. If it runs long enough to fully charge the batteries it runs at near full load the whole time since LiFePO4 don't need a long absorb time.

Check out Will Prouse's YouTube channel for his independent battery and equipment test results.
1 week ago
It does not meet your cold weather requirement as-is but this family in northern BC uses their outhouse year round. You might be able to add insulation, a door and a small propane Buddy heater for intermittant heat. Even a small electric heater would work in a small space if you run power out there. Gridlessness put up this video of their composting outhouse 8 years ago:

https://www.youtube.com/watch?v=v2ZViclQbc0

There was an update 2 years ago where Jeff explains how their outhouse has saved them around $250,000 based on an initial cost of $100,000 borrowed for 30 years at 8%. Most of the info is in the second video so you can skip the first one, although it has a few humorous moments...

https://www.youtube.com/watch?v=INy12evR-IU

You could also use garbage cans to collect the output (like Paul's willow feeder approach) in a structure like this.
3 weeks ago

John F Dean wrote:As part of an Operations Management course I was teaching, I attempted to go into business ethics using a functional approach.  Such as if I screw over the best suppliers and screw over my best customers, how long can I expect to remain in business?   Silly me. I thought the concept was obvious.   About 50% of the class thought I was speaking a foreign language.  Their concern was only for the short term. Once they had padded their resume they would be with a new  employer.  Now, for the real scary part.  These were healthcare management students, and most of them were already working in the field.



It sounds like many of your classmates would fit in perfectly at the company in this humorous public service announcement from the Norwegian Consumer Council. It's calling out the increasing ensh*tification of everything. They even touch on Paul's issues with web pages and calling for customer support. Truly, the love of money is the root of all kinds of evil.

Warning: If you are offended by the use of the word sh*t, just use "sleaze" and DO NOT click

https://www.youtube.com/watch?v=T4Upf_B9RLQ

r ransom wrote:Better than 1080 is promised to paying subscribers, but they seem to be complaining about this issue just as much as advert watchers like me.

As for "free", 2 to 3, 15 to 20 second, non skipabble ads every 55 seconds of video,  isn't exactly free.  For some reason, I ended up stuck on that experiment of theis for the last 2.5 years.  That's a lot of income they are getting from a free service, combined with data gathering and selling permissions we grant them...



Using Brave, Opera or Firefox with the uBlock Origin extension you won't see any of those ads...

The videos look fine to me with Firefox on a Linux PC. I'm not signed in to YouTube in case that makes a difference.
1 month ago
This is a great thread on drying firewood:

https://www.hearth.com/talk/threads/solar-kiln-for-hardwoods-part-deux.175875/

Summary: The firewood should be stacked off the ground with air space underneath. IBC totes, pallet crates or any way to stack the wood in a sunny place. Create a peak at the top with a board or some of the stacked firewood. Cover the stack with clear plastic sheeting. Wrap the base with stretch wrap to hold down the cover. Cut u-shaped vent holes in the side near the top to allow air circulation. Adjust the vent hole size to limit the maximum temperature.

The thread also discusses target temps and how long to dry the wood.
3 months ago
Finally, a use for the silly hog ring pliers that have been in my toolbox for years... So far, it looks like using a hog ring instead of thread to tie the end of the rope will work out fine.

To cut nylon rope I grab an old utility knife blade in some vise grips, heat it red hot with a propane torch then slowly melt through the rope. Pushing the ends of the cut rope against the blade will fuse all the fibers together nicely. You might have to heat the blade more than once depending on the rope.

5 months ago

wayne fajkus wrote:
I am not sure if groundfos is the only pump or if there are cheaper alternatives with ick free auto (dry) shutoffs. If there are, i'd love to hear about them.



Long ago I had a Grundfos pump like yours to boost our incoming water pressure from about 20psi to about 65psi. The dry-run protection did not always turn it off when there was no input water which resulted in a warped housing and leaks. It was discontinued and parts like the leaking seals were no longer available. After searching for an alternative, I found a similar pump from Walrus:

https://www.walrusamerica.com/product/hq/

It worked great. Like the Grundfos, the small pressure tank on it and the variable speed pump held a surprisingly constant output pressure regardless of water flow. It was all engineered plastic and stainless like the Grundfos (no ick) and also had the dry-run protection. It was a lot less expensive than the Grundfos at that time. We sold that house so I don't know about its longevity.
5 months ago
We've had some indoor-only cats for many years. As a bonus, we have stacks of kitty litter buckets which are super useful - until the handle breaks, that is...

These buckets have either a slot or a hole for a tab on the end of the strap-type handle. Normally, the strap breaks right at the round grip section in the middle. Once it breaks, it's much harder to carry a full bucket and the remaining handle straps dangle below the bottom of the bucket.

Does anyone have suggestions on how to easily add a new handle? I've thought about punching a slot on each side and threading through some mule tape or it's cousin, pallet banding but haven't tried this yet. A piece of old garden hose could be added for more comfort. Depending on the stiffness of the strap it might not easily fold down out of the way. Ideas?
7 months ago
This is not for everyone, but... We live where the ground freezes and there is snow. Normally I take down trees in the spring right when the ground thaws. When the surface is saturated the subsoil will turn to goo. At that time it's usually pretty easy to use a 15' ladder to attach a 100' cable around the tree as high as you can reach then the tractor can easily pull even huge trees right over. An extra snatch block (pulley) can be used to turn the cable if needed. All of the roots come out of the ground easy peasy. It's the cleanup after you take down a bunch of trees that's the hard part. The window of time where this works is very short but it's much faster easier than knocking trees over with the backhoe in the summer.
8 months ago

William Bronson wrote:Fish skin,that's where it's at!
Seriously though, it's thing.
Ever since I found out about alligator gar I've wanted a jacket made of the skin!



You can see them make and use Fish Leather in this Gridlessness video:

https://youtu.be/CgxMkA1tFkE?t=551

It's from a burbot (ling cod) and they make a wallet (shown at the end of the video).
9 months ago