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Old 06-08-2019, 07:51 PM   #1
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48 or 60 Volt DC system anyone?

I am wondering whether anyone out there is using more that 24 Volt in their solar and house battery system.

While shopping around for Lithium-ion batteries I realized that there are several attractively priced sub-modules available from electric vehicles that have higher cell counts like 12s or 16s. Inverters are available for the resulting voltages. Building a dedicated driver for low voltage LED lighting is an additional task but feasible.

Aside from reducing cable losses, a higher system voltage would avoid the time and hassle of disassembling an EV battery and reassembling it for lower voltages like the traditional lead-acid voltages of 12V or 24V. The higher Lithium-ion cell counts are also easier to match to the high and low cut-off points of the commonly available inverters.

There is another incentive for me personally as I am in the process of building a small electric ATV that will run a 10kw motor with a 60V (16 cell) pack. If I use the same 60V modules for my house system, I could take one of the modules out of the RV for tooling around with the ATV. This way, I am not going to have $500 worth of battery sitting idle for most of the time. Designing a mechanical and electrical quick disconnect should be easy. Hooking the partially discharged battery back up to the fully charged house system will require some extra circuitry like separate BMS in each pack and "smart" interconnection relays.

The other downside I see with the higher voltage is that my second alternator would have to be rewound and I would probably have to custom build an external regulator, which is within my skill set. Solar charging is fortunately just a matter of putting enough panels in series and finding a suitable charge controller.
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Old 06-08-2019, 07:57 PM   #2
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Everything gets pretty dangerous at those voltages.

And more expensive.

Repurposing EV packs has much higher fire risks, to the point I say no for DIYers, only LFP is safe enough aside from lead.

But back to voltage - build 12V pack "modules" for charging and normal House usage in parallel, but only say 3-4 max in use concurrently.

Series them to get higher voltages for EV purposes.
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Old 06-08-2019, 09:43 PM   #3
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Originally Posted by john61ct View Post
Everything gets pretty dangerous at those voltages.

And more expensive.

Repurposing EV packs has much higher fire risks, to the point I say no for DIYers, only LFP is safe enough aside from lead.

But back to voltage - build 12V pack "modules" for charging and normal House usage in parallel, but only say 3-4 max in use concurrently.

Series them to get higher voltages for EV purposes.
What I was comparing are various packaging formats of LG Chem prismatic (pouch) cells. These cells have a solid safety and reliability record.

Yes, there is always somebody who pokes a screwdriver in the wrong spot or does not understand that maximum and minimum voltages are not vague suggestions but hard limits. But that same person also creates sparks next to a bubbling lead acid battery, puts metal tools on top of batteries, and the consequences of that never make it into the sensationalized headlines.

We should ask the local Emergency Room how many acid burns in face and eyes they treat per month. Honestly, I blew up a LA battery several years ago by being complacent and was just lucky that nothing squirted towards me.

After running high capacity Li-Po packs assembled from RC helicopter cells for almost a decade in various e-bikes and other contraptions I am not buying into the volatility hysteria against Lithium-ion batteries. The cells in the RC packs are considered the worst in terms of volatility but with proper care and early disposal of any cell that shows puffing or charge anomalies I am comfortable to have even that chemistry right under my bum.

When you are dealing with the energy densities Lithium-ion packs offer you should be concerned about currents long before you worry about voltages. Yes, 60 V is "up there" in terms of lethality potential but even at 12 Volt levels I apply assembly and maintenance precautions similar to handling the commercial explosives I am licensed to use. In both cases you have a lot of energy available either as your friend or your enemy. So make your moves consciously and wisely.

12 Volt is definitely out of the choices for the bus. Too much copper needed to keep the losses down. I considered serializing two 8 cell packs in the ATV but it drives up both the cost and weight per kilowatt hour. That's why I was curious if anybody out there is running at 48 Volt (gaining popularity in residential solar) or even 60 Volt in their bus.
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Old 06-08-2019, 10:16 PM   #4
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24V is still more expensive than 12V, but common enough from many boats & trucks, most device types can be found.

If you go higher, then you likely just end up running everything off inverters, and that has such a huge efficiency hit when off-grid.

Copper is a once-off, does not need replacing if done right. . .
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Old 06-08-2019, 10:20 PM   #5
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I ran into someone over on solarpaneltalk.com that is running 48v on his bus. If your power needs support it, why not go 48v?

48v is not dangerous to work with.

Quality 48v inverters are readily available.

48v to 12v converters are reasonable for the "must have" 12v loads.

Now 60v is a different story. I don't think that I have ever seen an inverter or DC appliance that would run on 60v.
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Old 06-09-2019, 05:45 AM   #6
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We run a 48 volt solar system at our house. 10 kW solar... 25 kWh NiMH battery backup.
Blew one inverter of the two after 4 yrs. Replaced under warranty.

In our electric solectria one we run 196 volt 20 kWh based on Nissan leaf batteries.
The leaf battery is very easy to re configure in 48 volt setup.

In our other solectria we run 172 volt about 14 kWh bases on Chevy volt batteries. Even easier to get 48 and 24 volt.

I would run the bus on 2 modules 48 volt in parallel and the ATV 2 modules in series for 96 volt.

For 48 and 96 and higher there at plenty DC/DC converters available in the 200 watt range.

For the alternator you can go to a rewound automotive with PM used for wind turbines and hydro. They are more efficient with not using a field. An ordinary switcher power supply can bring it back to your desired voltage.

For the solar charge controller .... Just set the battery temp compensation to zero. Then the max output voltage will be less dependent on temp.

If your bank is large relative to your solar then I would be not so worried about the charge controller... Your BMS will cut it off when it is full.

Johan
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Old 06-09-2019, 05:53 AM   #7
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Oh and I forgot.. The power stroke engine compartment is pretty full and hot. There is space for a second alternator but it is all hard to work on. Why not rewire your original alternator for house 48 volt and convert it back to 12 volt to keep the starter batteries in good shape.

In dory we had an alternator blowout and kept the electrical system going on the solar power.
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Old 06-09-2019, 09:17 AM   #8
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Originally Posted by joeblack5 View Post
Oh and I forgot.. The power stroke engine compartment is pretty full and hot. There is space for a second alternator but it is all hard to work on. Why not rewire your original alternator for house 48 volt and convert it back to 12 volt to keep the starter batteries in good shape.

In dory we had an alternator blowout and kept the electrical system going on the solar power.
Yes, I am dreading to mount that second alternator at the bottom of the engine after finding the additional bracket, idler, etc. Also, more bearings on the serpentine belt means more chance of getting stranded.

The idea of running the vehicle alternator at the higher "house" voltage and then stepping down to recharge the vehicle starting battery is appealing. Who worries about a few percent efficiency loss when the ICE is running.
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Old 06-09-2019, 09:29 AM   #9
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Originally Posted by PNW_Steve View Post
I ran into someone over on solarpaneltalk.com that is running 48v on his bus. If your power needs support it, why not go 48v?

48v is not dangerous to work with.

Quality 48v inverters are readily available.

48v to 12v converters are reasonable for the "must have" 12v loads.

Now 60v is a different story. I don't think that I have ever seen an inverter or DC appliance that would run on 60v.
Quote:
Originally Posted by joeblack5 View Post
We run a 48 volt solar system at our house. 10 kW solar... 25 kWh NiMH battery backup.
Blew one inverter of the two after 4 yrs. Replaced under warranty.

In our electric solectria one we run 196 volt 20 kWh based on Nissan leaf batteries.
The leaf battery is very easy to re configure in 48 volt setup.

In our other solectria we run 172 volt about 14 kWh bases on Chevy volt batteries. Even easier to get 48 and 24 volt.

I would run the bus on 2 modules 48 volt in parallel and the ATV 2 modules in series for 96 volt.

For 48 and 96 and higher there at plenty DC/DC converters available in the 200 watt range.

For the alternator you can go to a rewound automotive with PM used for wind turbines and hydro. They are more efficient with not using a field. An ordinary switcher power supply can bring it back to your desired voltage.

For the solar charge controller .... Just set the battery temp compensation to zero. Then the max output voltage will be less dependent on temp.

If your bank is large relative to your solar then I would be not so worried about the charge controller... Your BMS will cut it off when it is full.

Johan
Following your suggestions, I may go with somewhere around 48V for the "house" in multiple parallel packs if I can get a T-mount alternator rewound for that and then use two packs in series in the ATV.

I am planning to use the same pouches that are in the Leaf packs, just assembled differently. The Leaf packs would have a little too much capacity and weight at the voltage needed for the ATV motor. But if the price is right, I may reconsider. What is an additional 25 pounds compared to ATVs with lead acid batteries? The Leaf packs are certainly easy to assemble into a large "house" bank.
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Old 06-09-2019, 09:37 AM   #10
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Quote:
Originally Posted by joeblack5 View Post
...

For the alternator you can go to a rewound automotive with PM used for wind turbines and hydro. They are more efficient with not using a field. An ordinary switcher power supply can bring it back to your desired voltage.

...

Johan
Do you use 3 power supplies (one on each phase) for a PM alternator?
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Old 06-09-2019, 12:51 PM   #11
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The Chevy volt modules are 48 volt with nice screw terminal at each end.... Someone just hacked the BMS can bus for the individual modules...

The leaf are nice to..a little more expensive per watthour.

For the three phase alternator you will need a three phase bridge to DC. Many "mean well " switcher power supply can accept DC on the AC terminal. They also have wide range inputs from 85 volt to 240 may be more. Leese Neville and such might have 48 v alternators in stock.
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Old 06-09-2019, 01:12 PM   #12
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Originally Posted by alpine44 View Post
The idea of running the vehicle alternator at the higher "house" voltage and then stepping down to recharge the vehicle starting battery is appealing. Who worries about a few percent efficiency loss when the ICE is running.
Plus the Starter gets discharged under .0001% in normal usage, really the whole engine electrical needs set is trivial.
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Old 06-09-2019, 01:12 PM   #13
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Quote:
Originally Posted by joeblack5 View Post
The Chevy volt modules are 48 volt with nice screw terminal at each end.... Someone just hacked the BMS can bus for the individual modules...

The leaf are nice to..a little more expensive per watthour.

For the three phase alternator you will need a three phase bridge to DC. Many "mean well " switcher power supply can accept DC on the AC terminal. They also have wide range inputs from 85 volt to 240 may be more. Leese Neville and such might have 48 v alternators in stock.
Thanks, didn't think about feeding DC to a switcher.

Do you have a link to the BMS hack?

I was planning to call Prestolite/Leece-Neville tomorrow after seeing that some of their 4000 series alternators come with the T-mount case and also as 48V models albeit in a different case. Maybe I can clobber something together from different parts. Like bolting T-case halves to a 48V center section.

If that does not work I will have one of their 230 Amp alternators for the 7.3L PSD (AVI160T2002) rewound. At least there is a bolt-on alternative to the puny Ford alternators.
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Old 06-09-2019, 01:17 PM   #14
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Plus the Starter gets discharged under .0001% in normal usage, really the whole engine electrical needs set is trivial.
Unfortunately, there are also the headlights and other 12 Volt consumers but the total wattage could be handled by a DC-DC converter.
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Old 06-09-2019, 01:33 PM   #15
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Yes, it should all be one supply. Its continuous output rating does not need to handle brief peaks, the Starter will buffer.

Check if Sterling has a 48V DC-DC unit.

Also Victron Orion series, and they have another more recent line, very robust.

Samlex, Mastervolt, Osculati, Powerstream
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Old 06-09-2019, 01:35 PM   #16
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I used to have a Synocean Technology STC-48450, got it super cheap on eBay.

But computer / industrial / telecom units might not be designed to handle the shock / vibration.

Stick to the marine world IMO.
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Old 06-09-2019, 03:03 PM   #17
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chevy volt bms hack...
https://www.diyelectriccar.com/forum...ce-200023.html
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Old 06-09-2019, 04:34 PM   #18
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Do you guys have any good leads on reasonably priced Leaf / Volt batteries. I am still in the planning stages of my electrical and trying to balance cost vs weight vs capacity vs life.
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Old 06-09-2019, 04:54 PM   #19
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Go to DIY EV forums and Endless-sphere, start new threads with your need **and location** in the title.

Hazmat shipping makes it a pretty local quest.
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Old 06-09-2019, 05:51 PM   #20
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Awesome, thanks!
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