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HP R/T3000 UPS
#1
HI All,

Hoping for some idea if I can use a HP R/T 3000 UPS as my Rolleyes .

The battery string is 120v, so do you know of a way to use 18650 battery's to run this?

The 3kv would be enough to run my shed so it would be a cheap start to my powerwall.

I have 10 190w solar panels which I plan to connect to the battery to charge them.

Thanks for your time.

Troy.
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#2
(06-09-2019, 03:56 AM)TroyD Wrote: The battery string is 120v, so do you know of a way to use 18650 battery's to run this?

Don't take offence at my reply.

On the basis that you are asking such a simple question, for your own safety you really shouldn't be considering the construction of a DIY 120v DC battery.

Find yourself another smaller UPS to play with.
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#3
You would need to connect enough packs in series to get the 120VDC, or about 32s. You would need to know the upper/lower limit of the UPS before you know if 31s, 32s, or 33s is needed to fit the range the best.

I agree with Sean that safety at these voltages is of utmost importance. 120VDC will kill you if you become the load.

I would recommend that you have several smaller strings, say 4 strings ( 32 / 4 = 8s, or high 28V, for example) and then only when sliding the packs into a holder do they come in contact with the other packs to make a full 32s string. And ALWAYS have the main connectors covered. NEVER leave any terminal connector over 72V uncovered and exposed. Bad things can happen at such high voltage. Either a tool/wire can short them out, or "you" could short them out and cause a nasty burn or lead to death.
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Proceed with caution. Knowledge is Power! Literally! Cool 
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#4
Thanks for the advice, I do understand the dangers of high voltage, and my question was more along the line if any one has tried to convert this kind of UPS, I do have a DELL 1k that is 36v which I will use for camping and easy to setup.

Korishan I am interested in your idea of 4 strings, how would this work, do you have some links to ideas? How do you charge just one of the packs at a time ?

Again this is just looking at ideas, I may just go and buy an inverter, just did not want to wast money if I could use what I have access to.

Thanks every one.
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#5
For the 4 strings, you could either use the UPS to charge the whole string with a proper BMS interface, or if you wanted to charge each sub-string separately, just use a 28V charger, and again with a proper bms to handle each pack.
You could even use the cheaper bms units for each pack, and then when assembled together to make the full string, they are disconnected/bypassed and switched over to the beefy bms.

Interconnecting the string-packs together would be like sliding anderson connectors together. If I were building this type of setup, I would probably make each string-pack have an anderson connector. Then when sliding the series-pack into a holder, the anderson mates with the other in the holder. Considering the size of the series-packs, it wouldn't be that difficult to shove the pack to make a solid connection, or yank on it hard to disconnect. I say this as anderson connectors have a habit of being very difficult to disconnect at times, which I'm sure you're aware of dealing with other UPS units.

So each series-pack would be like a carriage unit that is used on large battery systems. Or like the way server PSU's are done, or anything else that makes a carriage have heavy connectors on the main unit.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
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#6
(06-10-2019, 01:51 AM)TroyD Wrote: Thanks for the advice, I do understand the dangers of high voltage, and my question was more along the line if any one has tried to convert this kind of UPS, I do have a DELL 1k that is 36v which I will use for camping and easy to setup.

Korishan I am interested in your idea of 4 strings, how would this work, do you have some links to ideas?  How do you charge just one of the packs at a time ?

Again this is just looking at ideas, I may just go and buy an inverter, just did not want to wast money if I could use what I have access to.

Thanks every one.

Stick to the 36v setup. Although, if you plan to go bigger in future, you would be better off investing in a 48v setup. There are not a whole lot of options when it comes to 36v inverters or charge controllers.

Aside of the hazards of 120v DC, you also need to consider the hardware required to maintain a 120v lithium battery. 32s would require appropriate balancing hardware, which would be expensive. Also if you were considering second hand cells, it would be difficult to capacity match 32 series packs. It would probably require some fine tuning after construction.

There are other considerations with high voltage DC. PV (solar) chargers are not readily available for such high voltages. Breakers and switches become very expensive, as high voltage DC has the potential to arc.

In short, the expense buying the hardware to support a 120v DC battery, would most likely exceed the price of buying a 48v inverter.
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#7
(06-10-2019, 01:51 AM)TroyD Wrote: Thanks for the advice, I do understand the dangers of high voltage, and my question was more along the line if any one has tried to convert this kind of UPS, I do have a DELL 1k that is 36v which I will use for camping and easy to setup.

Korishan I am interested in your idea of 4 strings, how would this work, do you have some links to ideas?  How do you charge just one of the packs at a time ?

Again this is just looking at ideas, I may just go and buy an inverter, just did not want to wast money if I could use what I have access to.

Thanks every one.

I started with APC UPS(s).  I had 8 of them around the house and one of my first thoughts was to use these as battery bank / 120v emergency power.   Tests revealed that they charge up to 27.8v (at 7s that's 3.97v per cell) and 'cut-off' at 20.1v (at 7s 18650 that's 2.87v per cell).  So great - it is 'kind of' in range of a 7s 18650 battery pack and I made a few packs.
Lesson learned:
- The top voltage of 3.97 does not allow full utilization.
- The cutt-off at 2.87v per cell is in theory OK but at extreme low end and if cells not balanced, this is risky!
- The APC itself has to be initialized with 120v external source to startup  -  its not just a simple inverter and you add a battery and turn it on.
- The unit burns 40watts/hour just sitting there...  that's 960watts in 24hr period - so inverter power would have to be used in first few hours of power outage.   

It could be that an HP UPS works quite differently...   but the conclusion for me - Its better to do a coordinated battery + inverter + charger.  A simple/flexible charger such as MPT-7210a will accept DC power supply and/or PV panel to charge.
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#8
(06-10-2019, 02:05 AM)Korishan Wrote: For the 4 strings, you could either use the UPS to charge the whole string with a proper BMS interface, or if you wanted to charge each sub-string separately, just use a 28V charger, and again with a proper bms to handle each pack.
You could even use the cheaper bms units for each pack, and then when assembled together to make the full string, they are disconnected/bypassed and switched over to the beefy bms.

Interconnecting the string-packs together would be like sliding anderson connectors together. If I were building this type of setup, I would probably make each string-pack have an anderson connector. Then when sliding the series-pack into a holder, the anderson mates with the other in the holder. Considering the size of the series-packs, it wouldn't be that difficult to shove the pack to make a solid connection, or yank on it hard to disconnect. I say this as anderson connectors have a habit of being very difficult to disconnect at times, which I'm sure you're aware of dealing with other UPS units.

So each series-pack would be like a carriage unit that is used on large battery systems. Or like the way server PSU's are done, or anything else that makes a carriage have heavy connectors on the main unit.

I do like this idea. However I wonder if a cheap BMS would be safe to use with upwards of 100v at full charge. Like 4s(7sXp). 4 series of 7s BMS to give 120v?

I acquired 3 very similar UPS myself, and I am toying with the idea of a lithium conversion. I will post some photos tonight. They seem to only have 3 small toroidal transformers. I am guessing it should prove rather efficient.

One still has enough life left in the original batteries to test its efficiency, but I need to get myself an AMP clamp.
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#9
For balancing, split the cells into isolated module stacks of say 5x24V (or 4x7s) with any comms opto isolated (1000V standard). This would then be safer and reduce the incident points/issue or 120V DC 3rd degree burns. With AC you feel the voltage before it burns and damages, with DC you get burnt and then feel the damage already done. Rubber gloves (not fight club style, lol.)....

The charger within UPS units tend to be low current and take a lot of hours to charge the existing small capacity, so adding a lot more Ah the integrated charger is pretty useless.

Split charge with fully isolated chargers (switch mode units may share a common neutral) at say 24V.

In terms of overhead (no load power draw) the larger UPS untis can be quite bad/high draw. They may be cheap to buy and use but in the long term the additional lost kWh of power can far outvalue the purchase price....

Lower voltage UPS units (12/24V) can be quite good as some of them have low idle losses, albeit your not going to boil the kettle with them.

Server units are a bit more robust, but the trade off is higher idle losses and more fan noise.

That's my input..
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#10
(07-03-2019, 07:17 PM)completelycharged Wrote: For balancing, split the cells into isolated module stacks of say 5x24V (or 4x7s) with any comms opto isolated (1000V standard). This would then be safer and reduce the incident points/issue or 120V DC 3rd degree burns. With AC you feel the voltage before it burns and damages, with DC you get burnt and then feel the damage already done. Rubber gloves (not fight club style, lol.)....

The charger within UPS units tend to be low current and take a lot of hours to charge the existing small capacity, so adding a lot more Ah the integrated charger is pretty useless.

Split charge with fully isolated chargers (switch mode units may share a common neutral) at say 24V.

In terms of overhead (no load power draw) the larger UPS untis can be quite bad/high draw. They may be cheap to buy and use but in the long term the additional lost kWh of power can far outvalue the purchase price....

Lower voltage UPS units (12/24V) can be quite good as some of them have low idle losses, albeit your not going to boil the kettle with them.

Server units are a bit more robust, but the trade off is higher idle losses and more fan noise.

That's my input..

I was more thinking of using the UPS as a UPS - not an inverter. Just giving it some longer legs. I may even consider using some lead acid batteries instead. However, at risk of hijacking this thread, I will start my own once I get some numbers together.

Great idea for external charging though.
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