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Old 02-16-2021, 10:05 PM   #21
Mini-Skoolie
 
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Ugh, where are you located?
I'm in the middle of Wisconsin. we've been getting down into the -teens F at night and maybe mid single digits in the day for the last couple of weeks but it is warming up some this week. The cold weather makes for slow bus progress.

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Old 02-17-2021, 05:16 AM   #22
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Hi all... love the thread.

First don't listen to me. I've never rolled my skoolie off the driveway! I'm in year six of my build and already upgrading the electrical system. So don't listen to me! Ha!

That said... LISTEN... don't even THiNK about lead acid batteries anymore. The price for new lithium batteries has dropped and it just doesn't make sense not to use lithium. So much more power available, so much less worry about keeping them watered or fully charged. You have a solid 80 to 90% of the available capacity of lithium with no out-gassing, no acid and half the weight.

Most of us on here are doityourselfers and have some knowledge of electricity to begin with but if you aren't one of those people and you're stuck with purchasing all pre-made components then lithium can still be pretty expensive. But you can put together a DIY 480ah lithium battery these days for about $500 purchasing lithium cells direct and the prices keep dropping while your choices keep expanding.

One caution... design the whole system with component choices and prices all on paper before you purchase the first thing. Lots of 12volt system components, a growing array of 24volt system components and a small list of 48volt system components are available. Each system has it's advantages and disadvantages. When your choices are fewer, the prices go up.

This post was not meant to provide details... it was meant to entice you to consider lithium. Don't consider lead acid the cheaper alternative. It's not anymore. A decent lithium system can last twenty years and longer, without the weight, the outgassing, the worry of always keeping them fully charged. Lithium likes sitting half charged and can be left that way for years! Six years ago, lithium batteries cost three times as much or more than they do now. I couldn't even entertain the cost back then.

A good resource of information to start with is diysolarforum.com. Also lots of good DIY lithium battery informative videos on YouTube by Will Prouse. He has a lot of videos showing multiple lithium battery builds.

Learn about lithium.

Regards!

Ross
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Old 02-17-2021, 07:40 AM   #23
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But you can put together a DIY 480ah lithium battery these days for about $500 purchasing lithium cells direct and the prices keep dropping while your choices keep expanding.


Ross
Here again without specifying the voltage Ah is useless and misleading. If you do not want to use the voltage then use watthour.
About the price.. unless you buy used.. please share your source.

1 cell at 3.2 volt and 272 ah manufacturer in china alibaba in bulk was about $110.
Even at 12 volt that would be $440 but only 272Ah.

Although there is nothing complicated about DIY plenty of things can go wrong. Lithium is unforgiving upto dangerous with overcharge. Fires can be impossible to put out. Accidental full shorts can be a disaster because the internal resistance is so low. Inhaling a vaporized screwdriver is bad for health..read potential deadly..

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Old 02-17-2021, 12:28 PM   #24
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My bad... don’t know where I got 480ah. I meant 4800watt hours and it is more... AliExpress has them for around $800. For $900 you can get eight 280ah cells. That would be 6700 watt hours! Using 90% would give you roughly 6000 watt hours and twenty plus years of life!

You will spend money on a good BMS (I am using an SBMS0 from Electrodacus) but with panels sized to the right 12 or 24v system, using the SBMS0 you can go without a solar charge controller. Two shunts, normal fusing and circuit breakers... and with lithium you get the added advantage of banking more solar energy from your panels. As lead acid batteries fill they resist charge current. Not so with lithium! So charging is more efficient.

My system can be charged with solar, shore power or a dc to dc charge from my bus alternator. All autonomously.

Look... I’m no expert on lithium. But you can fry a screwdriver on lead acid too. Nothing takes the place of safety. All I’m suggesting is give lithium another look. There is no cost advantage anymore using lead acid batteries. You can use lithium and not worry about recharging them right away. They’re happy at a 10% charge! Not so with lead acid. Lighter weight, more efficient charging, more usable energy, twenty plus years of use, no out gassing... and putting your own pack together is easier than it’s ever been.

I misspoke before and stand corrected. The prices fluctuate a lot as well. At Christmas I saw the cells I purchase for 1/2 what I paid last fall. Consider AliExpress for purchase you can wait a couple of months for. It worked out for me.

Regards!

Ross
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Old 02-17-2021, 02:23 PM   #25
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No problem Ross,

I agree with you on most accounts.

I use a chargery. Does your SBMS0 has an mppt build in? You could loose some efficiency without the mppt.
Also the added safety of two overcharge limiting devices instead of one might be worth in with lithium. It is amazing how sharp that overcharge / voltage curve is. Lead acid does bad things when shorted as well but the internal resistance is a lot higher for similar size Ah, so the boom is a little bigger.
Also additional heaters have to be installed to allow charging at low temperatures.
Charging directly from the alternator might work Ok but is not guaranteed. because of the low internal resistance the alternator might have to put out its max. power for extended period of time. Depending on RPM and cooling issues it could / and others have experienced an early alternator death.



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Old 02-17-2021, 09:42 PM   #26
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Johan,

There is so much to say around the Electrodacus BMS I wouldn't begin to give it justice. I'll cover what I think are the highlights.

It's strength is in separating the brain from braun. The SBMS0 receives input from sensors and sends out control signals. The control signals turn on or off charge and load devices. It also logs data on system operation and can store 12 months for download (if you're into that sort of thing). The braun is done by external devices supplied by Electrodacus or other vendors. The DSSR20 is a special solid state relay used to control current from solar panels in parallel with a maximum current of 20 amps. Typically only two panels in parallel. But, the same control signal can control many relays up to 30kw of power.

In this system, there is no charge controller. That goes against all we learned but these controllers were originally built to charge lead acid batteries. Lithium essentially takes anything you got, and MPPT looses it's advertised advantages when the solar panels chosen are closely matched to the battery bank voltage used. In fact, when the right panels are used, MPPT may actually come in lower because of losses inherent to the system. Even if the MPPT charge controller comes in slightly higher, it doesn't justify the added cost and complexity... that is, if you choose the right panels in the first place. If you already have a system in place, it may be best to keep what you have but that needs to be determined on an individual basis.

It has been confused that the SBMS0 sends PWM to the SS relays to control power from the solar panels. It does not. It simply turns them on or off based on individual cell and pack voltages set by the user (the default values are pretty much dead on). Also, the SBMS0 balances the cells during both charge and discharge. Most BMS' balance only during charge cycles.

It has an input for sensing pack temperature and will turn off charge and load currents if temperature falls below or above set points.

If you have an inverter with a toggle switch, the SBMS0 can be wired into the inverter to turn it off if the cell voltages drop to low. It can also turn off other loads in a similar fashion. My inverter has a momentary push-button power switch so I designed a small control board that would turn it off by signal from the BMS. I posted the schematic for others to try.

A typical Electrodacus installation uses two shunts instead of one. It tracks load current, charge current and the difference is calculated to show how much reaches or is taken from the battery pack in real time. There are six "pages" of information through the display. More than most of us need or want.

Since I already had a system in place and had 96 cell solar panels already, I kept the MPPT charge controller and set the output parameters to match my lithium battery bank voltage. The SS relay merely connects or disconnects the panels to the charge controller.

I plan to rebuild my battery box to include insulation and heaters I purchased to keep them warm in winter. I should have done that in the first place. I knew better.

The link below brings you to pictures in random order of my bus project. Way too many pictures! But if your interested, you'll find work I was doing around the lithium upgrade and the new BMS.

https://drive.google.com/drive/folders/0B3GV_wV9HoXaR245OHVtMHJCVXM?usp=sharing

I'm aware of burning up the alternator. The DC charge controller I have allows you to throttle the current draw from 40 to 20 amps. I'll start with 20 and go from there. I think the alternator is capable but the bus needs to be moving to cool the alternator properly for 40amps. The load seen by the alternator is generally twice that. Efficiency be damned.

I've rambled on... I hope I covered your questions. I think we all fall in love with the components we chose. So far, I can't fault a single thing with this BMS.

Regards!

Ross
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Old 02-18-2021, 06:47 AM   #27
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Previous link didn't work. Maybe this time...

https://drive.google.com/drive/folde...XM?usp=sharing
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Old 02-18-2021, 02:30 PM   #28
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My type of thread

So this seems like a great thread for me. I'm just starting out my conversion and am looking into electrical pretty heavy.

I have on order 32 of the 280Ah LifePo4 cells. I'm planning on building a 48v 16s2p setup, I think it's about 23KWh.

I'm also going to have 8x400w Trina solar panels.

I'm trying to spec out the system to be both comprehensive but as simple/straight forward as I can.

The core of my inverter/charger is most likely going to be Victron equipment, but I'm hoping that the mulitplus II gets released in the US before I need to start buying equipment. Part of what I'm still researching is a BMS that will communicate with the Victron equipment. I'm thinking either an orion jr 2 or batrium wattmon as they both seem to work over canbus to communicate correctly with Victron stuff.

I'd like to be able to charge the batteries efficiently, run electric for all services (water, cooking, AC and hopefully both house and bus battery charging), all while keeping the core simple. Then expand for as much solar utilization as possible. For instance, I'd like to build in a solar water heater as I've seen units that work with the Victron setup and shunt extra power to heat water once the load and batteries are handled.

I'm also looking to run pex under the floor when installing the insulation, I'm just trying to figure out how to heat that and also water efficiently. Not sure if that's all based on my hot water circuit or if I go diesel heater with a heating circuit.

All the questions!
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Old 02-18-2021, 05:31 PM   #29
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Originally Posted by EvBindAZ View Post
So this seems like a great thread for me. I'm just starting out my conversion and am looking into electrical pretty heavy.

I have on order 32 of the 280Ah LifePo4 cells. I'm planning on building a 48v 16s2p setup, I think it's about 23KWh.

I'm also going to have 8x400w Trina solar panels.

I'm trying to spec out the system to be both comprehensive but as simple/straight forward as I can.

The core of my inverter/charger is most likely going to be Victron equipment, but I'm hoping that the mulitplus II gets released in the US before I need to start buying equipment. Part of what I'm still researching is a BMS that will communicate with the Victron equipment. I'm thinking either an orion jr 2 or batrium wattmon as they both seem to work over canbus to communicate correctly with Victron stuff.

I'd like to be able to charge the batteries efficiently, run electric for all services (water, cooking, AC and hopefully both house and bus battery charging), all while keeping the core simple. Then expand for as much solar utilization as possible. For instance, I'd like to build in a solar water heater as I've seen units that work with the Victron setup and shunt extra power to heat water once the load and batteries are handled.

I'm also looking to run pex under the floor when installing the insulation, I'm just trying to figure out how to heat that and also water efficiently. Not sure if that's all based on my hot water circuit or if I go diesel heater with a heating circuit.

All the questions!
Hi EVbindAZ

It sounds like we are at about the same place in the build. I think I'm planning about the same system. But I'm concurrently deep in rust mitigation, new metal coming soon. IMO go with the diesel heat for the cabin and hot water.
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Old 02-19-2021, 11:10 AM   #30
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Hi EVbindAZ

It sounds like we are at about the same place in the build. I think I'm planning about the same system. But I'm concurrently deep in rust mitigation, new metal coming soon. IMO go with the diesel heat for the cabin and hot water.
What do you have planned for hot water?
I've been looking at some 240v electric water heaters as I haven't been able ot find anything at 120v that seems to provide enough heat to make it useful.

I was hoping to keep out of needing 240v as that changes the inverter side.

Are you using diesel heat for both house water and home heat, or just one of the two?
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Old 02-19-2021, 11:28 AM   #31
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What do you have planned for hot water?
I've been looking at some 240v electric water heaters as I haven't been able ot find anything at 120v that seems to provide enough heat to make it useful.

I was hoping to keep out of needing 240v as that changes the inverter side.

Are you using diesel heat for both house water and home heat, or just one of the two?
Even the smallest 120V water heaters are going to near saturate a standard 15A/20A outlet on their on. If you are hoping to hook up to shore power for hot water, you need either 30A or 50A hookups.

Personally, if you have enough AC appliances to collectively pull > 1500W I think you're better off planning for split phase/240V/50A service from the start. It will make things simpler and more future proof.


For hot water, we use a Girard tankless/on demand propane heater, it is the only propane appliance we have- a 25lb tank lasts forever. For heat, we have a 9000BTU a mini-split that until two days ago was our only heat source. Now we also have diesel heaters- only one in the front at this point, after the snow melts I'll put another in the rear.
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Old 02-19-2021, 03:56 PM   #32
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Originally Posted by EvBindAZ View Post
What do you have planned for hot water?
I've been looking at some 240v electric water heaters as I haven't been able ot find anything at 120v that seems to provide enough heat to make it useful.

I was hoping to keep out of needing 240v as that changes the inverter side.

Are you using diesel heat for both house water and home heat, or just one of the two?
EV,
I'm planning on a diesel hydronic heating system for both the cabin heat and hot water.

something like https://www.heatso.com/espar-d5e-rv-heater-kit-12v-5kw/
or https://www.dieselheat.com.au/produc...d4wsc-furnace/
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Old 02-20-2021, 07:06 PM   #33
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Ridiculously good thread. Good enough to entice me into commenting. Well done, gang.
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Old 02-24-2021, 07:06 PM   #34
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Yeah, but those are 2k and 3k items. That's a lot more than I was looking to spend on something I'm hoping to not have to use. I was looking at a solar to water heat diverter for when the batteries were full and possibly a diesel heater for if we get into could trouble that the mini-split heat pump can't handle.
I'm wondering if I bump up the power side to 240 if I can run a water heater that will also do some hydronic... but I'm pretty worried it's way over the service interval for a unit like that. I did see some of the diesel stoves that would also run hot water through them. I might look into those more.
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Old 02-25-2021, 01:21 PM   #35
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Yeah, but those are 2k and 3k items. That's a lot more than I was looking to spend on something I'm hoping to not have to use. I was looking at a solar to water heat diverter for when the batteries were full and possibly a diesel heater for if we get into could trouble that the mini-split heat pump can't handle.
I'm wondering if I bump up the power side to 240 if I can run a water heater that will also do some hydronic... but I'm pretty worried it's way over the service interval for a unit like that. I did see some of the diesel stoves that would also run hot water through them. I might look into those more.

Look into the Chinese diesel heaters on ali express if you’re into a cheap solution for non-mission critical items. They’re dirt cheap and by most accounts reliable and broadly tested in this community. They’re also like 1/5 the price of the name brands so you can buy 2 if you’re worried about reliability and still come out far ahead.

Also, a 120v 15a 20 gallon storage hot water heater would be fine in an emergency if you had a place to store it, and they’re like $400 new.
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Old 03-12-2021, 02:54 PM   #36
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Welp... batteries are here.

Now to decide on a BMS.
Electrodacus, Rec BMS, Batrium, or something else...
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Old 03-22-2021, 02:14 PM   #37
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Welp... batteries are here.

Now to decide on a BMS.
Electrodacus, Rec BMS, Batrium, or something else...
Just to make your decision on a BMS more difficult there is also one from Ewert called the orion and orion jr.

good luck.
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Old 03-22-2021, 03:22 PM   #38
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So it looks like Electrodacus doesn't have a 16s version.

Has anyone tried one of the others?
Orion Jr, Rec, Batrium or even just a simple Overkill.

I'm thinking a pair of https://www.solar-electric.com/victr...50-120vac.html for 240v output.
I'm trying to find an electric water heater I can use that won't overwhelm the 6kVA that I'd have available without having to get up into the big quatro line of inverters.
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