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Use GreenWorks 80v packs
#1
I would like to utilize my GreenWorks 80 volt battery packs to supplement my home's UPS whenever the packs aren't needed in the lawn mower or other yard tools.

I have Qty.2 of the 2ah packs, and Qty.2 of the 4ah packs.  Commonly I rotate the 2ah packs between the leaf blower and snow thrower, and the 4ah packs in the lawn mower.  It is extremely uncommon any two packs are used simultaneously.  I already have wide input (80v) to 12v and 24v DC-DC converters that I use with these packs to power things when camping, or when home utility power goes out.  I have already made a connector that interfaces with the 80v battery pack socket (pos. neg. terminals only, not any of the charge status/balancing terminals)

My UPS (a TrippLite SU750XL 750VA 600W UPS Smart Online) has an internal 24V battery string (two 12v SLA type) and an external connector for another 24V battery string.  Input to this connector should keep the UPS inverter working.  Problem is it also acts as a 24VDC output for charging the battery.

Any suggestions/ideas/brainstorming on how I could do something like this...
80v pack(s) --> DC-DC converter --> 24VDC --> into UPS (but also blocking diodes??? so UPS could not force power back into the DC-DC converter?)

Other unknowns I'd like to explore...
- Can I combine the pos./neg. rails of multiple GreenWorks 80v packs for longer runtime? safely?
- Is it the Greenworks battery pack internal circuitry, or is it the tool, that shuts off the battery when it drops below a minimum safe voltage?
- Is this stupid / overly complicated ... to re-utilize the 80v packs when they are sitting idle 6+ days out of the week?  (for example, I only mow the lawn once a week, the rest of the time they sit in the house)
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#2
Open one of the batteries if possible. If there is a BMS inside and it is not the tool that shuts down then you probably can't use them in parallel. If there isn't then you can.

If you can DC-DC to 24V at 95% efficiency you have 152 Wh of extra energy for your UPS. With one of the 2 Ah batteries that is. The specs say it runs 11 minutes at 300W load when fully charged with the internal batteries. If the inverter works at 85% then the system draws about 353W from the 24V batteries for 11 minutes. So you are getting about 65 Wh from the internal batteries. You could add more than double that again with one of the 80V 2Ah batteries. I am totally tired, I hope I got the maths right Smile

Given the complications I wouldn't do that. If this UPS needs more capacity I would add more or bigger lead acid batteries or do a full conversion to lithium. Adding lithium via DC-DC to a lead acid system doesn't seem like the way to go. But if you like the idea then go for it. It is possible for sure if you really want it, just needs a bit of tinkering.
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#3
I'm sure the Tripplite UPS's have some kind of software for altering its parameters just the like the APC ones do. I doubt the batteries have any kind of bms on them as they are probably just standard UPS batteries connected in series.
There is no reason why you can't just connect the GreenWorks with a bidirectional buck converter. Julian Illet has done several buck converters and he's even made a bidirectional one. There's also one that's already made and you have two pots you adjust to get the voltage right on both ends. https://www.youtube.com/user/julius256/s...query=buck

There'd be no reason the UPS can't charge the batteries as long as you have a bms that will adjust the input voltage/current for the proper curves. Or, you can turn off charging by adjusting the parameters of the UPS so it stops charging once a lower voltage is reached (instead of 24V, you'd make it like 18V or something) and that would effectively stop it from charging.
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#4
Pictures of the 80v 2ah pack here: http://imgur.com/a/o0qS6

This is the DC to DC 24V converter I have: https://www.meanwell-web.com/en-gb/dcdc-...--100d--24
...4.2amp, will the UPS potentially draw more than that?

There is no way in the UPS software to "turn off" the external battery pack connector/charge port, it is always outputting 24vdc :-(

Current UPS load: http://imgur.com/a/HOlJD
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#5
I would go the simple way. You want them as emergency. Then you have no input power right? If so they wont charge the pack either right?

Just go with a DC/DC. Make sure you have atleast 2x the current needed. The UPS will take alot during startup and that can shut down the DC/DC easily.

I have done exactly above a year back or so and it works fine.

If you got AC connected to the UPS you either need to shutdown the charge or use diodes. Though Diodes could cause issues...
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#6
Here's a few pages for communicating with the UPS:
http://networkupstools.org/docs/man/tripplite_usb.html
http://networkupstools.org/docs/man/ups.conf.html (linked to in the above, but extra commands listed so it's not overlooked)

You may be able to use NUT (which is mentioned in those links) to do the communication. There are versions for linux as well. Tripp Lite is very hush hush on their protocols, apparently. At least with the above, you can set the float super low (this may have the benefit of shutting down output charge voltage)
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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#7
Interesting, thanks for all the info so far.

I'm considering that perhaps I'm going about this the wrong way...
Instead of trying to convert the 80v pack down to 24v to feed the UPS, why not just convert the 80v packs up to 120v ?
Isn't this more efficient?
Then I have the advantage of using these instead of a generator/car inverter when/where ever I want.
Suggestions on an inverter that takes 83vdc (fully charged pack) to 70vdc (low pack) and coverts to 120vac?
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#8
So as long as your inverter can handle that voltage, then yes, 120V DC to 120V AC is more efficient. You could also see how hard it'd be to change to 60V as that would be almost as good.

Taking an input voltage of around 80V DC is kinda odd. Now, 96V DC is a different story. You can find those, though a bit pricey. The 120V DC->AC setup is pricey, too. It requires a bigger transformer as there is more windings on the coils. Well, on the "battery" side of it. Both primary and secondary has to be the same number of turns. Normally the secondary is less turns thereby the transformer is smaller and lighter.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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#9
There are some china companies that have it. But quality is what you pay for Smile

I dont find the link right now for the seller i had in mind that had high voltage inverter and could customize for the user need.
Follow me! >> YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#10
(09-09-2017, 03:57 PM)jpm Wrote: Suggestions on an inverter that takes 83vdc (fully charged pack) to 70vdc (low pack)

Isn't it more like 84V to 60V as this is probably a 20S pack?
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