Tesla Off-Grid-Charging. Overheat, Overload and Disconnect... IT WORKS! 

Sry, I should have read your post first. didn't even realized how old this thread is.

Danke Dir vielmals. Es ist noch ein weiter Weg. Im Sommer klappt das nun schon gut aber im Winter ist einfach nicht genuegend Sonne da um die Battery zu laden. Ich arbeite daran und kurbele die Produktion kraeftig an...

Good info for anyone using this inverter.

I think MPP Solar inverters have an inner relay for that. So when your main power is down relay closes.

PIP 5048MK definitely has internal MEN relay. Uses upstream supply when power is on the input terminals. Switches in the internal if upstream supply is disconnected.

Thank you! Cheers!

Thank you! Cheers!

Much appreciate all your tips and comments, Jeremy. Thank you. I think I can set a delay time for the BMS to when it closes the contactor again to avoid this flip-flop. The Inverter was without load when this happens as the Tesla charger takes 15-20s to ramp up again. I'm not sure why it had this behaviour. If I set the low voltage disconnect to high it may trigger it already in peak situations? Is this something you have come across?

@@OffGridGarageAustralia I haven't had any issues with that, but I will confess that I think some of it could be because the Orion BMS has a really ingenious method of finding the actual cell voltage even while under load. They have some method of finding a cells "open circuit voltage" even while the battery is under load. When you configure voltage cut offs, it compares against this calculated "open circuit" voltage rather than the "under load" voltage which you'd read with a standard voltmeter. This helps remove the need to adjust the voltages lower to avoid tripping them while under load. It now occurs to me that other BMS units may not have this same functionality. The folks at Orion explained it to me once and they basically said that the BMS checks the voltages very rapidly, hundreds of times per second. It then compares the voltage readings against the current flowing in/out of the battery and adjusts the open circuit voltage accordingly. In the case of inverters, since inverters basically pull a rectified sine wave from the battery there are roughly 100 moments per second where the current is actually at or near 0. (Because the inverter pulls more current as the sine wave increases in amplitude and pulls less when the sine approaches 0 in magnitude). Because of this the BMS is able to simply wait for current to get near 0 and use that to find the open circuit voltage. If it can't get that measurement it can calculate it by adjusting for the current flow. Either way: The Orion basically accounts for any voltage drop that would be caused by load so it's less of an issue. However I just went back and checked the history log of my BMS and looked back to the last time I had a good solid discharge (Overnight where solar wouldn't affect the voltage readings) and even the "under load" voltages sagged by only 0.04v when drawing 20 amps from a 200 Ah battery. (Roughly 1100 watt load.) I've honestly never noticed any significant voltage sag on the cells even under much higher loads, not enough that I would necessarily worry about them tripping the under-voltage protection at 2.9v. A voltage drop of 0.1v would be quite unusual I would think.

This fine tuning is killing me!

I'll try that.

YES, I'm looking at some of them for a while but they were more like $600...

Good thinking

@@OffGridGarageAustralia your busbars seems different some square some round. You seem to have different areas covering the terminals. I would aim to cover the complete terminal. The busbars look small for the max amps these cell can handle according the spec. Super build very informative.

@@FKZNL the busbars came with the batteries youd think they were suitable for the spec of the batteries

Whats the fuse rated at?

@@grahamjones6712 look at the size, looks small to carry 280 amps. I orderd 4 of lishen 272 ah cells with dubbel busbars to carry 280 amps. 280 amps on that distance would require 50sqmm at least in wire. Compare the lugs he crimped to the busbars 1 vs 2mm in thickness 25mm wide vs 20mm. The klauke lugs will carry the amps the busbars wont carry 280 amps. In this installation its fine. The amps the inverter is pulling he can use single busbars. Dont expect the chinees to deliver to max spec of the cells if you have not stated that you want to pull ful amp rating. I think the advised discharge current is 0.5c so 140 apms. That wil be the amps the busbars are calqulated for. The cells are cheap for a reason one of them is they dont handle high C discharge.

Yes I would use 800 grit grade sand paper on all the bus bar ends including washers and studs' this will improve things a lot....

You must be a Chiefs fan 😉

Hahaha, wow, Peter. Better than Superbowl... 😂

@@Adlay_Eetswah Brady fan! I knew the Bucs would win anyway...

@@peterrock2838 The Man is a true Champion 👍🏽

Yep, they came in a pack of 4, cell 5-6-7-8 are from the same delivery.

Yes, I am agree with you. That should not be happen.

@@OffGridGarageAustralia I do t have the time to watch everything, did you top balance batteries before final assembly?

Before you condem those cell, remember these cells “fall off the cliff” when fully discharged. The other cells are also pretty much depleted. As I understand it Lifepo4 cell should not be discharged below 20%. Your cells are way lower than that.

I think Basen ship randomly used cells to the consumer for better prices but this destroy the whole package of 48V system 😕

I'm trying to calm down now!

Yeah, these fuses are not the greatest for these high current applications. A lot of resistance. I should have installed a proper 2-pole DC breaker with 100A. Next time, I guess 😊

I'm observing and learning

@@OffGridGarageAustralia and doing a dam good job keep it up my good sir

The BMS will protect from normal overload events, the fuse is there for when it's all gone to crap, the fault current to clear could be ten's of thousands of amps, you won't find a suitable circuit breaker for this application that can deal with that.

Only Active balancers do balance all the time. Passive balancer only burns away top cells power while charging.

@@mrzed6597 I did notice in one of his previous videos, Andy’s bms balancing cells while he had the battery constructed but not under load or taking any charge, perhaps he needs to tweak his balance settings via the app?

@@Adlay_Eetswah He set the cell V too low. Should be 3,65V. And because of this the BMS started to balance, burn the load. And so the cells where not equally discharged and gone out of balance. Simple.

@@mrzed6597 That’s an interesting argument you put forward.

@@Adlay_Eetswah I know. He made a perfect top balance ... and then let the BMS broke it. After top balance BMS balance needs to be turned off for at least a full cycle. And only when charging up enabled again. Now I think he charges the pack. I HOPE not to 3,65V, only 3,45-3,50V. So the cells first reaching it will not overcharge. Passive balance with 0,2A is a joke if you charge with 10-20A. Cells in 3,65V and charging are overcharged. That causes degradation.

It didn't even reach the 2.7V before it kicked in again. Also, the load is zero at the beginning as it takes the Tesla charger around 10s to ramp up again to full load.

@@OffGridGarageAustralia Of course, it was just the inverters fans kicking on as they are on a dumb temperature controller. So it was the SmartSolar feeding current in that was causing the bms to cycle.

@@OffGridGarageAustralia the inverter will have a load of capacitance on the input, don't you get a big arc when you connect it to the batteries? That Arc is what the BMS is seeing every time it switches, its not good and it will die quickly, in an automative application where those BYD relays are used there will be a pre-charge circuit to charge the caps before the relay switches in.

Thanks for your comment, Jim. These cells 6, 7 and 8 actually didn't have the 'bad' connections. These were on the other side of the pack. I have to check again.

@james: be careful as you're using copper busbars and aluminium terminals, this causes galvanic corruption in the aluminium. Ironically the best material may actually be aluminium or steel, the best ones I've heard are copper bars plated in another metal.

The bus bars are perfectly fine for 50-60A. The issue is getting good contact with the battery terminals. With only 6mm screws, the surfaces have to be as clean and flat as possible as you cannot torque the screws down very much. I helped install a 4S2P system on a yacht and running the bow 7kW thruster (500A) the BMS clearly showed the bad bus bar connections (the cell voltages were all over the place). After flattening all the bus bars with 800 grit wet-n-dry paper, the losses where drastically reduced and were consistent across all joints.

@@OffGridGarageAustralia Please do check the connections. You probably actually had "good" connections on those three cells, which is why they drained so quickly. Webb0y's comment is a good one, as with mis-matched materials you can get some corruptive effects given time, humidity, and high power. Remember, it's not just amperage, but power (wattage). 3000 watts is a lot of power, and can move mis matched materials given substantial time. I was using the same technique that Keven discuss's below, with 800 grit, you're actually still roughing up the surface, although to the touch, it seems smooth. The best monitor is still cells that drain quickly- they have the best connection.

Yep. Separate port BMS is better for a DC coupled system. Can charge without discharge.

All links are in the description. Shunt: off-grid-garage.com/battery-accessories/ BMS: off-grid-garage.com/battery-management-systems-bms/ Battery monitor: off-grid-garage.com/measurement-tools-and-analisers/

Thanks for your comment Lou!

I know, 2.5 is last resort before things get really worse. You mean no fuse at all? Just the BMS taken care of overcurrent?

@@OffGridGarageAustralia yeah, I guess it depends on the BMS, but I believe most will shutdown the relay/FETs in an overcurrent situation. I don’t know if your model does that or not.

Yeah, found the product link on AliExpress and it does mention over current protection, but that’s all it says. No idea how effective or reliable it would be

@@jeromehelbert2628 I wouldn't trust the BMS to handle it. His BMS is using a latching relay (Which is why it draws so little power when on) and they can easily fail / get stuck in the closed position. I always include a fuse (along with circuit breakers) because a fuse will not fail in the "on" position the way a latching relay or circuit breaker can.

You really don't want that relay trying to open with a 10,000Amp fault current running through it, you still want a fuse, you could probably size it quite high though.

It has to do with the safety system of the Tesla EVSE. It needs a proper grounding/M.E.N. link to work.

Uhm, I'm not sure what this does under high currents.

@DIY Projects Try silver. Just kidding. ;) Copper is good. :)

@DIY Projects Hmmm. :) I bought 1/8" copper stock on Amazon. Ni is convenient because it doesn't oxidize quick like Cu. I wish I knew more.

28.8kW - wows!

Yes, it can charge from DC power.

I need to do more testing. I wasn't planning of discharging that much. The situation just came along so I let it go to see what happens. I'm a tester ;)

Video is following...

Thanks!

I know. You're right at the beginning of my videos... there is more... 😉

@@OffGridGarageAustralia Yeah. Ive seen that. ☺️ great channel. Keep up your great work. But do think about replacing that bms. I’ve seen you use it in your later videos too. :-D Just a friendly tip. :)

@@pederb82 Still testing it in my production setup. I think it is important to show it off and make others aware of the pros and cons of such devices.

That was my question too. That's the first time I tested it. Might be that special BMS only?

@@OffGridGarageAustralia , my DALY BMS 16S does that, the SRNE 5kw inverter also have the same option to set the voltage. I believed it is done that way that battery cell should not stay long at that level of charge that is should be charged right away to a certain level and discharging should only be allowed at some higher level only that the chemistry have stabilized to a better level after being drained.

@@OffGridGarageAustralia It is a Common port BMS. It has to turn on to let you charge the battery. For a DC coupled system like this a Separate port BMS would be better. That can allow charge without allowing discharge.

@@OffGridGarageAustralia The problem is that it's a relay based common port BMS and the relay can only be on or off. So either needs to be a separate port with two relays or a mosfet based, because mosfets have polarity, so it can decide which way is allowed.

Yeah, correct, I looked at the shunt, not the inverter output.

Yeah, I don't have high loads on this battery. 60A max is the highest...

But on the other hand you will never identify these bad cells if the get constantly balanced from the other cells.

Very good observation 👍

Personally I would use a min 6kw inverter' to be on the safe side with these higher loads

Yep, I also get my capacity tester soon, so can test these three cells individually.

Wie hast du das gemacht? Schleifpapier?

@@OffGridGarageAustralia Ich habe mir 1000er Schleifpapier mit einem Tropfen Öl genommen und dazu ein Endmaß.

Well, I ordered a different inverter. I'm not happy with these 70VAC on the DC side and don't know what trouble it may cause later on...

We will see with the next test...

What would be the difference apart from going into the thread a tiny bit deeper?

@@OffGridGarageAustralia just using the whole depth of thread, then backing off a quarter turn, maybe more contact area and a stronger connection. Maybe ? I really don't know. I know you did a top balance, maybe a bottom balance might help ? I'm confused about this, I've seen some people do top balance and others do bottom balance. What's the difference ? I think a top balance should be good for a solar application and a bottom balance is better for a high discharge rate. Is this correct ? What I'm reading says top balance is fine with a BMS so you should be fine. Bottom balance if no BMS and high C rates.Thanks for posting these videos, very entertaining and educational too !

@@OffGridGarageAustralia Studs may actually help quite a lot. using more of the thread means more contact for the screw (Which means more current carrying capacity for the screw) and it also means you can torque things down tight more safely. By inserting a stud and then using a nut to tighten: As you tighten the nut you know you've already got the stud all the way in, so you can torque down a bit tighter without worrying that the threads of the battery terminal will strip. Where as with a screw you may not have the threads all the way in as you begin to increase torque, and then the only way to get more threads is to apply more torque which can result in stripping threads because you may start applying torque before there's sufficient thread contact to handle that torque.

no no no.

Mine beeps only once before it turns off. It's a long beeeeeeeeep.

I checked that and have the link only connected while charging. The fans are turned off when idling while they are on during higher loads.

Also while idling the switching losses on the MOSFETs and diodes become a significant percent of power usage. This no load loss is just part of life with off grid.

I know, the link is dodgy and only for test purposes, proof of concept.

Muss ich testen. Das war der erste Test...

The BMS stopped discharging at 2.5V. The balancing will start if one cell reaches 3.4V. There BMS will not charge the batteries or control the charging process unless you go below or above the thresholds set.

Rick, for a 16 cell battery, you need a 16s BMS. 16s stands for 16 cells in series.

???

Yeah nah

@@OffGridGarageAustralia - I said it was a guess.

Need more testing. I'm recharging atm so will see then if they also hit the top first, then they are bad, I guess.

@@OffGridGarageAustralia Yeah, please let us know. Thanks.

🤷‍♂️ I just used a fuse...