Trying to destory my SCC's: I can't do it!

[gnubie]

Definitely not a dealer, but at least when it comes to the 100/20 not just a hobbiest either. They are being used in remote area sat comms systems.

 

[gnubie]

I tested a little further and it was the output of the cheap lab supply doing it. If the input voltage leaps the Victron can't react fast enough, with only a light load in its outputs, so the voltage rises. Abrupt jumps in input voltage would be an abnormal situation when feeding the controller from a solar array under normal circumstances, and even less likely to happen when the array itself is lightly loaded.

As a bit more information, from off and with no battery connected, the Victron bought the output voltage up to absorption stage for the manually configured time and then dropped to float voltage. In tail current mode it almost immediately switched to float voltage. In both cases, the exact behaviour expected.

 

[HaldorEE]

I tested a little further and it was the output of the cheap lab supply doing it. If the input voltage leaps the Victron can't react fast enough, with only a light load in its outputs, so the voltage rises. Abrupt jumps in input voltage would be an abnormal situation when feeding the controller from a solar array under normal circumstances, and even less likely to happen when the array itself is lightly loaded.

As a bit more information, from off and with no battery connected, the Victron bought the output voltage up to absorption stage for the manually configured time and then dropped to float voltage. In tail current mode it almost immediately switched to float voltage. In both cases, the exact behaviour expected.

Thanks.

What are your thoughts on the charge profile to use with these lithium NMC cells?

I want to use conservative settings. Charge to 4.05V per cell I think. I know I don't want to discharge below 10% SOC and Iwill use an active balancer circuit so I don't need to do top balancing. I haven't found a charge/voltage chart for these cells yet so this part is still hand waving.

I have 3000 WH of battery capacity which is double what I was originally planning. I think I will be able to take it easy on the batteries and still not run out of power.

I love the fact that I will not need propane in this van. Diesel heat and electric for everything else.

 

[gnubie]

Honestly I don't have a lot of experience with NMC cells, someone else would be best to answer that question.

 

[Solar1]

Can you kill a SCC by not having batteries...yes.

So I had an issue when installing a Morningstar controller and called up their tech line. Let me say I bought the unit USED and Morningstar KNEW it and still spent an hour on the phone and a followup call and email diagnosing the problem!! I can't believe such customer service!!

During the install I had a circuit breaker to the battery that tripped (repeatedly as it turns out) which resulted in solar input w/no batteries. Once I realized what had happened and having read the manual stating this could kill the controller I almost had several small heart attacks LOL.

I asked the Morningstar tech about it and he said not to worry. Yes, it can kill the controller, he explained what could happen (which I didn't understand anyway, something about a spike in some circuit) but he advised that it rarely does. When it does it is fatal to the controller but it is rare.

I hate posting something like this w/o specifics but I don't want folks thinking you can do this w/o any worries of failure because apparently it can happen and when it does it will ruin the SCC (or at least a Morningstar SCC).

 

[RickP]

I had the same concerns, especially considering placement of a breaker for that output. For Victron users only, and assuming your build has properly matched PV array to solar charge controller capacity, this is answered by Victron MPPT SCC engineers here: https://community.victronenergy.com...tsolar-mppt-10030-with-a-common-port-b-1.html. The engineer’s reply is about 2/3 down the page.

The very short answer is their first statement:

• The MPPT should NEVER break due to a battery disconnection. Even if that happens often

 

[Dzl]

I had the same concerns, especially considering placement of a breaker for that output. For Victron users only, and assuming your build has properly matched PV array to solar charge controller capacity, this is answered by Victron MPPT SCC engineers here: https://community.victronenergy.com...tsolar-mppt-10030-with-a-common-port-b-1.html. The engineer’s reply is about 2/3 down the page.

The very short answer is their first statement:

• The MPPT should NEVER break due to a battery disconnection. Even if that happens often

Thank you for finding this, this is useful info. I'm reposting the whole comment here since its pretty relevant to the topic:

I have got a few more comments back from the Victron MPPT hardware engineering dept:

• The MPPT should NEVER break due to a battery disconnection. Even if that happens often.
• If no other load is applied to the DC bus when the battery disconnects, a short voltage overshoot may occur.
• The overshoot should only last a second or two, if it occurs, then the voltage will stabilise at the voltage set point of the current charge state (eg float, absorption), including temperature compensation.
• Be careful if also using a remote battery sense option, if the MPPT sees a variation between the battery sense and the voltage at the terminals, it will adjust output to compensate (up to + - 2V)
• The MPPT is not designed to be a power supply, it is a battery charge controller. So fast load variations may lead to voltage dips and spikes when the battery is disconnected and loads turn on and off. The MPPT output voltage will stabilise when loads are stable though.
• Using the MPPT with a BMS like this that disconnects the battery is allowed by Victron, from our equipments perspective. In fact our own SuperPack lithium batteries operate on this same principle, where the battery disconnects itself internally to protect itself.

 

[RCinFLA]

Short of a poorly designed controller that smokes due to passing too much current, high input voltage is most likely to damage controller.

MOSFET breakdown ratings are based on repeative reverse pulses which trigger avalanch at lower voltages than static, non switching, high bias.

MOSFET manufactures keep their breakdown voltage margins pretty secret so folks don't design based on a available margin.

I would not be surprised for running switching maximum to be 30% greater then controller max voltage spec, but don't pick a cold panel Voc based on that.

Since 'morning sickness' (cold night on panels, as sun rises) is the most common occurance of high voltage failure, some controllers will take measures to avoid startup when they detect excessively high voltage. Just wait a little until sun warms up panel. This extends the margin on controller's overvoltage damage prevention.

MOSFET breakdown voltage varies only slightly with temp. Higher temps actually has slightly higher breakdown voltage.

 

[Zil]

Come on, Will. Put this to rest and test destruct some MPPT controllers.

 

[EricBarbour]

HAH

This thread reminds me of the time the "Goonzsquad" on YT decided to turn an old military truck into an RV. They mounted eight Renogy panels on the roof, wired them all IN SERIES (not knowing any better and evidently not being able to sit still long enough to RTFM), and ran it directly into a Renogy SCC meant for a maximum of 100v in. And blew it up. And got another Renogy SCC, and blew IT up. And babbled happily about their "learning experience". And finally went to a solar equipment dealer in Chattanooga for help. He sold them an AIMS SCC able to handle 150v and told them how to wire the damn panels.

Fair warning; if watching 2 ignorant caffeinated dudes babbling is a "trigger", do not watch this:

 

[Forbisher]

So I took every EPEver/Victron/PWM/Renogy solar charge controller, and tried to fry it by connecting it only to solar panels, and not to a battery... guess which one survived?

EVERY SINGLE ONE! I couldn't destroy any of them, and I left them connected to a high voltage array (80 volts) for 4+ hours each.

I connected each one to a lifepo4 bank after the test, and they functioned perfectly. Tested output with a watt meter before and after as well, no change.

I read in the manuals that you must NEVER connect an SCC to an array without connecting it to a battery first, because the potential that it can fry.

This thread reminds me of the time the "Goonzsquad" on YT decided to turn an old military truck into an RV. They mounted eight Renogy panels on the roof, wired them all IN SERIES (not knowing any better and evidently not being able to sit still long enough to RTFM), and ran it directly into a Renogy SCC meant for a maximum of 100v in. And blew it up. And got another Renogy SCC, and blew IT up.

Sorry but this thread has nothing to do with Blewing Up SCC's by over volting.
It is specific to having a SCC only connected to panels with the battery disconnected.
Nobody is saying over volting will not destroy a SCC unless it has safety cut offs like most of the solar generators and some SCC's.

 

[EricBarbour]

And as long as we're talking about blowing up SCCs, wanna know how to kill an AIMS SCC? Easier than you think, given how vague their owner's manuals are.

Most AIMS charge controllers have three pairs of terminals. One pair for panel input, one pair to the battery, and a third pair simply labeled "DC LOAD". What is "DC LOAD" for?

Allow me to exactly quote pages 11 and 12 of the official manual:
> Insert the wires through the bottom of the charge controller via the punch out
holes. 4 Solar Input 5 Battery Input 6 DC Load Output (#6 is not required)
and
> Connect the DC load+ (Positive) wire to the Load+ terminal on the controller,
> Connect the DC load- (Negative) wire to the Load - terminal on the controller.

Apart from the usual polarity warnings, the only "warning" for the DC LOAD port says:
>*NOTE – Do not connect the battery (s) to the DC load port. Only connect battery (s) to the “Battery Port”.

So I connected my 40A controller as such, with the "DC LOAD" going to the inverter. It worked fine with my 4000w inverter, ran the fridge and various small appliances---until we turned on the window air conditioner. The SCC instantly died, as in, smoke and zero function. No display.

Called AIMS Power and asked them why. Tech said "Oh, you should not connect the main inverter load to the DC LOAD terminals, connect the inverter directly across the batteries!" Asking why that was NOT stated in the manual produced only silence. They replaced the SCC with no questions asked.

So: if you have an SCC (of whatever brand!!) with a LOAD output, do NOT use it for the main load. No matter how vague the manual is. It's apparently okay for powering low-current loads like RV lighting or suchlike. Why do manufacturers do this? ¯\_(ツ)_/¯

(Funny thing, I attached the panels to that controller without any batteries or load a few times, and there was no damage.)

 

[efficientPV]

I have a large capacitor on the output of my charge controller, a legacy from a charge controller I built. I suppose it could add extra protection as it will act as a battery and absorb a spike should the controller be disconnected under load. I run only a single small battery and controllers could easily provide 100A. Just nice to get rid of some noise on the battery line.

 

[HaldorEE]

And as long as we're talking about blowing up SCCs, wanna know how to kill an AIMS SCC? Easier than you think, given how vague their owner's manuals are.

Most AIMS charge controllers have three pairs of terminals. One pair for panel input, one pair to the battery, and a third pair simply labeled "DC LOAD". What is "DC LOAD" for?

Allow me to exactly quote pages 11 and 12 of the official manual:
> Insert the wires through the bottom of the charge controller via the punch out
holes. 4 Solar Input 5 Battery Input 6 DC Load Output (#6 is not required)
and
> Connect the DC load+ (Positive) wire to the Load+ terminal on the controller,
> Connect the DC load- (Negative) wire to the Load - terminal on the controller.

Apart from the usual polarity warnings, the only "warning" for the DC LOAD port says:
>*NOTE – Do not connect the battery (s) to the DC load port. Only connect battery (s) to the “Battery Port”.
View attachment 18186
So I connected my 40A controller as such, with the "DC LOAD" going to the inverter. It worked fine with my 4000w inverter, ran the fridge and various small appliances---until we turned on the window air conditioner. The SCC instantly died, as in, smoke and zero function. No display.

Called AIMS Power and asked them why. Tech said "Oh, you should not connect the main inverter load to the DC LOAD terminals, connect the inverter directly across the batteries!" Asking why that was NOT stated in the manual produced only silence. They replaced the SCC with no questions asked.

So: if you have an SCC (of whatever brand!!) with a LOAD output, do NOT use it for the main load. No matter how vague the manual is. It's apparently okay for powering low-current loads like RV lighting or suchlike. Why do manufacturers do this? ¯\_(ツ)_/¯

(Funny thing, I attached the panels to that controller without any batteries or load a few times, and there was no damage.)

The load output is so you can connect a dumb DC load and the SCC provides a low voltage disconnect.

I plan on using the load output of my Victron Smartsolar 100/20 to power the LED lighting and fans. The Victron Multiplus will manage its own low voltage disconnect.

Didn't your SCC specify the max current rating of the load output? On the Victron units it is the same as the max charge current.

 

[HaldorEE]

The load output is so you can connect a dumb DC load and the SCC provides a low voltage disconnect.

I plan on using the load output of my Victron Smartsolar 100/20 to power the LED lighting and fans. The Victron Multiplus will manage its own low voltage disconnect.

Didn't your SCC specify the max current rating of the load output? On the Victron units it is the same as the max charge current.

The 60 A version has internal 50A fuses in the load output, the smaller SSC does not. You are right to be ticked, they did not mention the max current limit in the manual for the 20A/40A SCC. They did in the 60A manual.

I will use a 15A circuit breaker in series with the load output of my SCC.

 

[Dzl]

Pulling in a related discussion that is on topic:

Following your suggestions for reading including
Nordkyn Design: Introduction to Lithium Battery Systems // MarineHowto: Lifepo4 on boats. My question is do you think I can use the Van starter battery as a dump in the event of a high or low voltage disconnect leaving the solar charge controller with no where to go, particularly if I was not "home" when it happened.

I have 50 amps coming from the starter batteries to the Kisae DMT 1250 as well as 400 ah of solar. I am using a 50 amp breaker on the drivers seat to turn that charge source on when I drive and I know I would need to leave that on for the van batteries to be the the dump, also necessitating adding an ignition sense wire and some kind of relay/switch for the current to go the other way....can that be automatic? Also the Ford had a "live" all the time, without ignition power stud on the side of the drivers seat with the batteries, twin AGM'S under the drivers seat. Eric has the SLA in parallel with the LifePo4, in my case is that necessary? If you think I should repost this else where you won't hurt my feelings. Put it here because obviously you have read the articles. Thanks

It is my understanding that this isn't really a problem that needs solving. If I understand correctly what you are worried about (1) the BMS (or some other protection device) disconnecting the house batteries, while (2) the solar charge controller is still connected to the PV array. It is my understanding that this (while once thought to be a potential problem) is not an issue. At least with Victron and I believe Epever charge controllers. They do not need 'dump load' in the same way that a wind turbine would. See here. This has been confirmed by Victron. What charge controller are you using? Am I correctly understanding your question?

edit: I believe this is the particular Nordkyn article you are referencing right? I forgot how much was covered by this series, I think its time for a reread, There is soooo much info packed in this series and the marinehowto article, I'm lucky to retain 10% per read through.

The problem comes down to voltage spikes and is not particular to SCCs. If you take a simple buck converter there is a series inductor that is used to limit the current so that voltage can be regulated. If the load suddenly goes away, or drops, it's up to the control circuit/program to react quickly and cut back the on time of the transistor. The cheapies tend to have poor control, or deliberately loose control to make up for other design deficiencies, so they will spike up when the load goes away. That may well not be a problem for the SCC but any voltage sensitive loads still connected may not agree with getting 2 times their normal supply voltage for a moment. Victron, and probably other higher end SCCs, get it right and keep things under control. I've not tested an epever yet, but I suspect they may have voltage rise problems given their position in the market.

There are also SCCs that autosense battery voltage continually because of poor firmware etc and they will, from direct observation, go completely loopy if the battery goes away.

So while SCCs do not need a dump load you still need somewhere to throw the energy if the battery goes away. A hefty capacitor could do it if you play in the cheaper end of the pool.

@Mex Rider @gnubie lets move the convo over here

Would the sort of surge protector often used for lightning protection potentially fit the bill? (of course this would might end up being as expensive as just buying a better controller)

 

[gnubie]

You could add in your own protection components that sit a few volts above the maximum normally expected voltage of the SCC on the load and battery output. Considering the currents that are potentially involved you may want to go down the path of a disconnection system rather than crowbar style protection. Which ever way, it'd have be quick to clamp the voltage. Once that battery goes away what ever energy is stored in the inductor is going to push the voltage up and poor control in the SCC will only add to that.

Crowbar could be done, just that what ever is carrying the current to ground is going to been to be reasonably beefy. If you have an 80A SCC going full tilt when the battery goes away you need to be able to carry that full current plus including what ever is in the SCCs output capacitors and also in the load's input capacitors. That could be quite a lot to deal with. You could isolate the loads with transistors / diodes so that they can never discharge back towards the SCC.

A quick acting over voltage lockout circuit would just have to deal with the 80A from the SCC.

*edit to fix error*

 

[Dzl]

You could add in your own protection components that sit a few volts above the maximum normally expected voltage of the SCC on the load and battery output. Considering the currents that are potentially involved you may want to go down the path of a disconnection system rather than crowbar style protection. Which ever way, it'd have be quick to clamp the voltage. Once that battery goes away what ever energy is stored in the inductor is going to push the voltage up and poor control in the SCC will only add to that.

Crowbar could be done, just that what ever is carrying the current to ground is going to been to be reasonably beefy. If you have an 80A SCC going full tilt when the battery goes away you need to be able to carry that full current plus including what ever is in the SCCs output capacitors and also in the load's input capacitors. That could be quite a lot to deal with. You could isolate the loads with transistors / diodes so that they can never discharge back towards the SCC.

An quick acting over voltage lockout circuit would just have to deal with the 80A + output capacitors in the SCC.

sounds like a quality SCC is the path of least resistance

 

[erik.calco]

My friend has mad skills

 

[Bob142]

My friend has mad skills

Is your "friend" named Erik?...

That whole scene looks like a car crash and fire. What exactly happened there? Did someone do something bad like choose the wrong charge profile for the batteries or was it just a junky PWM SCC that smoked and melted?