Ebike battery as power hub after a disaster.

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spinningmagnets
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Ebike battery as power hub after a disaster.

Post by spinningmagnets » Sep 07, 2017 8:03 pm

The power inverters that convert 48V or 52V ebike batteries into 120V AC are common and well understood. However, they are not well known.

For food storage, most people want to have access to a refrigerator or freezer. Of course cans of food are a vital addition to any preparedness plan, as is a propane barbecue, which does not rely on grid electricity. That being said. Imagine your home has been devastated by flooding, and after it recedes, you must decide what to buy with the insurance check. I now believe a chest-style freezer that is rated to be very efficient is a very useful option.

If you have no back-up power, then over the course of the next few days, the frozen food will thaw out and should be cooked and eaten rather than allow it to spoil. Food in a chest freezer will last longer than a cabinet-style kitchen fridge/freezer. Once the frozen food is consumed, you can use any available power to run it as a fridge, with the temps adjusted to 40F.

If running off of a 48V bank of deep-cycle Flooded Lead Acid / FLA, there are charge control units that are readily available which can run off of a small solar panel array.

"2 Solar panels to run old freezer after hurricane"
https://endless-sphere.com/forums/viewt ... 41&t=89525

My first question is...if we have very small loads (no A/C, no TV, very small fridge, etc) then...I am sure it is possible to run off of a large ebike pack. Of course we can charge laptops, 18650-cell flashlights, and cell-phones off of ebike packs through a DC /DC power supply (I have a 12V output unit, plus 5V USB).

If we are running a small fridge to keep precious food from spoiling just a few days, using an ebike pack...will adding one or several large capacitors to the fridge compressor help on start-up?

If yes, what are the best bang-for-your-buck large capacitors (model numbers), and where would we attach them?

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Re: Ebike battery as power hub after a disaster.

Post by dustNbone » Sep 07, 2017 10:06 pm

Most of the 48V inverters I've seen have a peak rating double their continuous rating, and should have no problem at all starting a compressor. Domestic refrigeration appliances have a start capacitor built in, I would think it would be fairly simple to replace that with a larger one if you're having startup issues, but honestly I don't think it's necessary. I have one of these

http://www.ebay.ca/itm/2000W-Pure-Sine- ... 2442279505

but honestly I've never used it for anything more demanding than my computer/monitors/audio workstation gear during an outage. I will try and remember to test it with my freezer (though it's not a very big freezer) before the weather cools off. I'll use the 16S A123 stack to rule out any sag issues on the battery side.

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Re: Ebike battery as power hub after a disaster.

Post by Ozzzz » Sep 07, 2017 10:14 pm

I'd skip using the battery for such heavy draw. The company i'm involved with supply foodstuffs for extended hiking. Dehy (as opposed to freeze dry) comes back as good as fresh. Meats will last 12 weeks unfridged.

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Re: Ebike battery as power hub after a disaster.

Post by spinningmagnets » Sep 07, 2017 10:26 pm

One of my thought behind starting this thread is that often, people who are on the edge of a disaster have not been directly hit, but still suffer from electrical outages and gasoline shortages.

An ebike is better than walking, or having only a pedal-bicycle in a "no gasoline for two weeks" situation.

If all you have are four large FLAs as a home back-up power supply, it's impractical to take four large deep-cycle FLAs on a trailer to power an ebike, but...I would rather buy several large 48V ebike packs to accomplish the same thing (ebike power, plus home back-up power). They can power the ebike, and also act as a mini "Tesla power-wall".

The common solar-PV panels and chargers are set up to provide either 12V, 24V, and 48V. This means that 48V is the sweet spot where back-up power and ebikes overlap. Many of the inverters and charge-controllers will take up to 60V (so 14S 52V is acceptable). However, ALL the mass-produced items that are available and affordable are 48V.

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Re: Ebike battery as power hub after a disaster.

Post by dustNbone » Sep 07, 2017 10:27 pm

It's not really that big of a continuous draw. I just threw my clamp meter on my fridges cord for a second when I heard it start up, it's a fair size side by side, 25cu ft or so, and it's pulling 2.7 amps, so about 300 watts give or take. I have about 2000Wh of 48V battery laying around here, could probably keep it running for a few days if need be.

If you're stationary there's way better (cheaper, better tasting) ways to preserve food than what you'd want if you were on an extended hike.

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Re: Ebike battery as power hub after a disaster.

Post by dustNbone » Sep 07, 2017 10:32 pm

spinningmagnets also don't forget that you could potentially transport the depleted ebike batteries with your ebike and charge them somewhere that power is available, and bring them home to continue providing emergency power at home. You could fairly easily transport 4000Wh of electricity with you this way, if you have the batteries and a way to carry them on your bike (maybe a trailer at that point).

I know here when destructive weather happens power tends to go out in blocks, if you're near the edge of the outage area you might not be too far from somewhere that still has power.

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Re: Ebike battery as power hub after a disaster.

Post by amberwolf » Sep 08, 2017 3:24 am

spinningmagnets wrote:If we are running a small fridge to keep precious food from spoiling just a few days, using an ebike pack...will adding one or several large capacitors to the fridge compressor help on start-up?
AFAIUI, no, because the compressors are AC induction motors.

If you have a DC-motor system (BLDC with electronic control) then that'd be different. They do exist, but I haven't had any refrigeration or A/C system that had one. (other than the blower motor in the main roof A/C we have now). If it was a DC-powered system, then you could put the caps on the input of the main DC bus line inside the system.


Now, if the AC source (inverter) can handle the startup surge, but your battery powering the inverter can't, *then* you could use capacitors on the input to the inverter (output of battery) to provide the surge current without tripping the battery's BMS (or causing voltage sag so great the inverter cuts out from it's own LVC).

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Re: Ebike battery as power hub after a disaster.

Post by spinningmagnets » Sep 08, 2017 4:52 am

Now, if the AC source (inverter) can handle the startup surge, but your battery powering the inverter can't, *then* you could use capacitors on the input to the inverter (output of battery) to provide the surge current without tripping the battery's BMS (or causing voltage sag so great the inverter cuts out from it's own LVC)
I didn't know the right question to ask, but I can tell that this is the answer I was looking for! Thanks...

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Re: Ebike battery as power hub after a disaster.

Post by dustNbone » Sep 08, 2017 12:37 pm

Simple diagram of the starting circuit for a single phase AC compressor. Actually almost any single phase AC motor with a substantial startup load will use a variant of one of these systems. Most fridges I've seen use the middle (B) one but it's easy to tell by looking at the wiring. There's probably a diagram very similar to this on the back of your fridge.
domestic-refrigerator-starting-relays.jpg
domestic-refrigerator-starting-relays.jpg (107.38 KiB) Viewed 554 times

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Re: Ebike battery as power hub after a disaster.

Post by amberwolf » Sep 08, 2017 2:37 pm

Just keep in mind that "starting capacitor" is not a buffer cap like in DC, it's used for a different purpose, so making it bigger doesn't ease the load on the inverter.

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Re: Ebike battery as power hub after a disaster.

Post by fechter » Sep 08, 2017 3:05 pm

I have a Meanwell true sine wave inverter made for 48v. It works great off any of my 52v bike batteries. My inverter is small (300W) so not strong enough to run the refrigerator, but they do make larger models. During a recent power failure, I used it to power my TV and internet modem/router and charge some cell phones. It worked great and I don't think it used even 25% of the charge to run my big TV for a few hours. I have 3 bike batteries in that voltage range, so I could go for quite a while. In the old days, I used to try using car batteries, but that was very inconvenient and the Peukert effect really limited the run time.

I think the 1500W version would run the refrigerator. A true sine wave output will be much better for running an induction motor than a 'modified sine wave'.

Search eBay or Amazon for "48v to 120v true sine wave inverter" and you will see some. They are much more affordable than they used to be. I saw a 1500W version for under $200.
"One test is worth a thousand opinions"

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Re: Ebike battery as power hub after a disaster.

Post by amberwolf » Sep 09, 2017 2:17 am

I've not yet tested it with motors/freezer/etc, but I still have this inverter
https://endless-sphere.com/forums/viewt ... =9&t=75149
Image
and a reasonably-easy-to-reconfigure set of ebike batteries to supply the 12VDC it needs to operate.

Around here the power hasn't failed in years, and the worst it's been was maybe a couple hours (usually a few minutes). I think when I was in the apartment it was out for several hours, maybe overnight, because of a vehicle crash into a transformer or something a mile or two down the road (was quite a fireworks show, with fire, etc, as seen from the apartment). Something similar happened more than a couple of decades ago when I lived in a different house a few miles from here, though that was storm-caused, IIRC.


But at least I have it if I have to. :)

I also have a small deepfreeze, kept full of icepacks filling space between food, plus I have lots of styrofoam I can use to put under and around it should power fail, to keep it colder longer. The refrigerator only holds things defrosting for meals about to be made, and already-cooked things to be eaten for the week, plus again a lot of icepacks and water bottles to fill the airspace to keep it colder for longer, including the two cold-mats for the dog crate when taking them for trips.

I've also got a small solar water heater setup (not presently assembled), if it was long enough outage to need that, too.

I have a few small propane-torch canisters with a little gas in them if I *had* to use fire to cook with.

Only solar I have is three 1-foot-square panels made sometime in the 1970s or '80s, most likely. But I could use them to charge cells slowly if I had to. :)

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Re: Ebike battery as power hub after a disaster.

Post by Matt Gruber » Sep 14, 2017 3:16 pm

i had trouble starting the freezer on 2 FLA's that start my cars easy. why? i ran 30' of 14awg from the cars, to the inverter, and the v drop set off the ups alarm. no start.
SO i had to jump start it using 2 9ah SLA's right at the ups. i used a foot of 12awg wire and it got warm fast! so it must have one heck of a surge to get warm while connected to 2 car FLA's. :shock:
running it takes 100-135w.
At 1st i wanted to use my ebike pack, but having 2 cars doing nothing made more sense for me for a 24v inverter. "Get to work, you lazy cars" :lol:

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Re: Ebike battery as power hub after a disaster.

Post by fechter » Sep 14, 2017 3:22 pm

You're supposed to put the inverter next to the cars and run a long wire for the 120v. 10X less current at 120v.
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Re: Ebike battery as power hub after a disaster.

Post by Matt Gruber » Sep 14, 2017 5:15 pm

fechter wrote:You're supposed to put the inverter next to the cars and run a long wire for the 120v. 10X less current at 120v.
i know. BUT
cars in a 100F garage, 30' away my 84F workshop.
there was also 70' of 14 from the panels to the workshop. aren't you supposed to put the PV AND LA's all near each other, then run 120v the long run? of course, but sometimes. like the hot garage all boarded up, it just is not going to happen in an emergency. NO WAY i'd do this experiment in 100F.
One of the things i learned was, where to put the PV next time. i plan to drill a hole in the rear wall and shorten the 70' to 20'. Now with the MPPT working so well, i might stick it and the ups in the hot garage, as i now have the confidence that it won't catch fire :lol: and i won't have to baby sit as much.
i wish it were this easy. every 1/2 hour i noticed the amps drop, and the PV needed an adjustment. I found it entertaining to watch the amps vs. sun-clouds, so the cooler workshop was nice.
i'll probably try it different next time. It all depends on the mosquitoes! WITH LOTS of bugs, i go into workshop.
NO bugs and i could open 1 gar door and cool the place off.

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