# Using EV conversion as emergency home power backup



## MattsAwesomeStuff (Aug 10, 2017)

http://secondlifestorage.com <-- Tech-wise they're a few years behind this community I find, but, they're all doing basically what you're planning, minus the car.

https://www.youtube.com/channel/UC0pBauLp63yzf6sVdEOIUbA <-- This guy's Youtube channel might have good info for you. He's a bit of a... he thinks his way is the only way. I think he's the guy who founded the above community.


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## major (Apr 4, 2008)

westwallaby said:


> ...
> Has anyone done this for a reasonable price?


Hi west,

Basically yes, I have. I live in a rural area with a well. Grid power has a habit of going down in storms and other incidents. I'm left with no water as well as the usual stuff like lights, furnace blowers and such. So for emergency power I use spare EV batteries and surplus UPS units. The well pump inrush required a hefty kVA. I bought a used 4.3 kVA Ferrups for $100. Drove 200 miles to get it. Only thing wrong was dead batteries. Uses 48 V battery bank. I installed cables with Anderson connector so I can use various batteries. The Enerdel subpacks work well. I do not use the UPS built in charger. Here is a unit like mine on eBay. 
https://www.ebay.com/itm/Best-FERRU...401083?hash=item3d6c8109fb:g:960AAOSwU3VbSNVY 

Before that one, I bought a 3.1 kVA unit which a guy salvaged from a hospital basement. It was a spare, never used. Batteries were dead. Price tag still on it said like $3700. Cost me $100.

Hope that gives you a idea.

major


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## SeanOrk (Jul 7, 2016)

MattsAwesomeStuff said:


> http://secondlifestorage.com <-- Tech-wise they're a few years behind this community I find.


Would you mind explaining how they are a "few years behind this community" please.


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## boekel (Nov 10, 2010)

SeanOrk said:


> Would you mind explaining how they are a "few years behind this community" please.


One of the things is they end up paying more for low quality cells than we do for used EV batteries, and have to test every cell, use questionable safety measures (fuses / fuse wires that either don't work or have such a high resistance they're a fire hazard in itself, combine lots of different cells to get to a capacity, etc. etc)

But all that means more EV batteries for us...so maybe don't wake 'm up too fast..


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## SeanOrk (Jul 7, 2016)

boekel said:


> One of the things is they end up paying more for low quality cells than we do for used EV batteries, and have to test every cell, use questionable safety measures (fuses / fuse wires that either don't work or have such a high resistance they're a fire hazard in itself, combine lots of different cells to get to a capacity, etc. etc)


I think that's just the result of following what others do without a full comprehension of what they are doing - some do eventually see the errors of their way.

I suspect more ex EV packs are currently being repurposed for home energy storage projects than for traction battery usage in conversions.


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## westwallaby (Jul 9, 2016)

My EV car battery configuration is fixed at 150 V so it is really finding an inverter at a reasonable price that can accept this high voltage input that is the problem i need to solve. UPS systems are also mostly lower voltage (<48 V DC), however i had overlooked ebay, so will look to see if i can repurpose soemthing from there. I've trawled over the second life forum and again mostly found low voltage (<48 V) inverters. It appears that field is highly motivated by safety and avoids the higher voltage battery packs. Ironically, a thread on high voltage DC pointed back towards the EV community, which is more familiar with operating with high voltage packs.


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## major (Apr 4, 2008)

50 VDC. Is a cutoff for safety with many agencies. Something you should consider. Even many OEM automotive packs use 50V subpacks. 

I think the larger UPS use higher voltage batteries. Like 10 kVA 120VDC. But I suggest that you consider to modify your EV pack to 3 modules of 50V each so you can use standard low voltage equipment for the repurpose. Do it with a fuse in each subpack and Anderson connector. Make a parallel harness for UPS or use sequentially. Or go my route and get spare EV modules to use at home. 

Using your EV battery sounds like an eloquent solution but you may be better off finding salvaged Volt or Leaf modules for the stationary application. 

Good luck,

major


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## MattsAwesomeStuff (Aug 10, 2017)

SeanOrk said:


> Would you mind explaining how they are a "few years behind this community" please.


Sure,

Ten+ years ago, people were building EVs with lead acid batteries.

5-8-ish years ago people were building EVs out of large format single cell LiFePO4 batteries.

3-5 years ago, people were looking into building EVs out of 18650s or recycled laptop packs, and paying for them, though I don't think many did.

Today, people are almost exclusively using recycled OEM vehicle packs for EV batteries.


As in, if you do the math, it's cheaper ($/kwh) to buy OEM packs than it is to buy recycled laptop packs at the going (and competed) rates that people are paying for them from computer recycling places.

Elements of both communities are looking to do things on a budget (moreso there than here, with, the whole point of SecondLifeStorage being recycling), but the other community is recommending a less cost effective way using the status quo from a few years ago.

Just my two cents. I like both communities.


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## electro wrks (Mar 5, 2012)

I scored 3 of these discontinued UPS models as freebies from a local ISP: https://www.tripplite.com/smartonli...-option-db9-bypass-switch-hardwire~SU6000RT3U
They are set up to use a 240V (20 X 12V) battery pack. The replacement model uses a 192V battery.
I'm looking into hooking a solar array directly to the 240V battery (set-up with larger cells), but haven't been able to find a readily available solar controller rated above 96V. Anybody have any ideas? I hadn't thought about using a EV battery as a supplemental battery in the set-up.


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## Functional Artist (Aug 8, 2016)

I have found these guys very helpful (battery charging/DC experts)
...or just browse around, it's packed with lots of good info 

https://forum.solar-electric.com/


Hope it helps


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## summetj (Mar 30, 2011)

I've done this on a smaller scale using a 12v battery bank that powers a 2000 Watt inverter (120 volt output for fridge or microwave). My EV has a 120-130 volt pack, but I have a 500 watt power supply that keeps my 12v accessory battery charged. What I do is run a set of jumper cables from the trucks accessory battery to the 12 volt battery bank on the UPS and keep my DC->DC converter running.


The 12 volt battery bank (2x 6v golf cart batteries) can provide high current to the inverter for short periods of time (such as when running the 1500 watt microwave to heat food up), while the jumper cables allow the truck's DC->DC converter to "top up" the 12 volt battery bank. 



Obviously, I can't use more than 500 watts continuous, but this works well for running my fridge (which draws about 800 watts when running, but has a relatively low duty cycle). You could certainly put multiple DC2DC power supplies in parallel to improve the watts you can draw from the EV pack battery if needed. 



A more powerful version would use an off grid solar charger/inverter that is designed to have DC input from solar panels in the 120 volt range, so that I could wire up my truck pack as a very powerful solar cell that worked at night ;> This would basically integrate the 120->12v conversion into the solar charge controller.


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## westwallaby (Jul 9, 2016)

Good idea about the UPS. I've found a couple of models that use 148V packs, but these are 3-phase.
I'm also poring over the forums suggested - from which i've seen some cheap units offered by manufacturers from south east Asia. However, i'm not sure the specifications have been translated accurately. It would be money thrown away if i order a unit and it turns up with different specification to what i was expecting - i can hardly return it.


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