Victron Smart Solar charger wake up feature

[james1]

My new 280ah cells are almost top balanced. I would like to do a capacity test once they are installed with Overkill bms in 16s conf.

I am completely off grid with no generator and no 48 volt battery and no 12 volt to 48 volt buck converter.

My question regards waking up the Overkill BMS from under-voltage protection.

Method 1: Temporarily change the settings on the bms so that it will turn on and allow the Victron Smart Solar 150-35 to start charging.
Question: Does this ALWAYS work?

Does anyone have actual experience with Victron Smart Solar actually waking up their bms from undervoltage protection? I have read that the Victron Smart Solar chargers can wake up a bms which is in undervoltage protection the very next morning when the sun provides power to the panels. Which means if it does work as described i wouldn't need to use Method 1.

But does anyone have actual experience that it works as described?

Because if those 2 methods are not definitely going to wake it up, then i won't do a total drain down to cut off point. I will drain down to maybe 56ah which is about 20%.

Thanks for your input!

 

[sunshine_eggo]

Victron absolutely, positively will provide absorption voltage (and current if something is connected) at the battery terminals even if a battery is not there. They can be powered exclusively by PV. It does need to be connected to a battery ONCE to set the system voltage, but then it can be disconnected.

Additionally, since most BMS will trigger short circuit protection due to connecting the battery to the inverter, this is avoided as the MPPT will charge the caps. Once the BMS comes out of protection, there is no significant surge when the inverter turns back on.

I validated this when I disconnected my battery from my system, and my inverters kept running... powered directly by the MPPT.

All that said, you should set your equipment to turn off BEFORE BMS triggered protection just like you set your charger to terminate charge BEFORE hitting BMS limits. That's just best practice and minimizes the potential for issues.

The ONLY complication I foresee is you might need to turn your inverter off or disconnect it temporarily if it's powering loads when it comes back on. The battery/MPPT might not be able to keep up.

 

[james1]

Wow. That is a most definitive answer. Thank you very much for taking the effort to explain in detail.

 

[james1]

Victron absolutely, positively will provide absorption voltage (and current if something is connected) at the battery terminals even if a battery is not there. They can be powered exclusively by PV. It does need to be connected to a battery ONCE to set the system voltage, but then it can be disconnected.

Additionally, since most BMS will trigger short circuit protection due to connecting the battery to the inverter, this is avoided as the MPPT will charge the caps. Once the BMS comes out of protection, there is no significant surge when the inverter turns back on.

I validated this when I disconnected my battery from my system, and my inverters kept running... powered directly by the MPPT.

All that said, you should set your equipment to turn off BEFORE BMS triggered protection just like you set your charger to terminate charge BEFORE hitting BMS limits. That's just best practice and minimizes the potential for issues.

The ONLY complication I foresee is you might need to turn your inverter off or disconnect it temporarily if it's powering loads when it comes back on. The battery/MPPT might not be able to keep up.

So, just to clarify my understanding of your foreseeable complication, if I make sure that I complete the final drain of my capacity test at night, then turn off the inverter, then in the morning when sun rises the controller should awaken the BMS and start charging without issues?

 

[james1]

Because, unfortunately, my inverter, Aims 1500 watt, does not have configurable settings, and it's low voltage cutoff is + or - 39 volts which is way below setting for bms under voltage cutoff. So the BMS will go of first.

 

[sunshine_eggo]

So, just to clarify my understanding of your foreseeable complication, if I make sure that I complete the final drain of my capacity test at night, then turn off the inverter, then in the morning when sun rises the controller should awaken the BMS and start charging without issues?

Yes. Provided there are no other loads on the battery that may exceed what the MPPT can provide.

Because, unfortunately, my inverter, Aims 1500 watt, does not have configurable settings, and it's low voltage cutoff is + or - 39 volts which is way below setting for bms under voltage cutoff. So the BMS will go of first.

Understood. Most non-configurable inverters seem to cut off at 42V or below.

 

[james1]

Thanks for posting such excellent explanations

 

[sunshine_eggo]

While we're at it, please provide your MPPT configuration with the Expert switch turned on.

 

[james1]

While we're at it, please provide your MPPT configuration with the Expert switch turned on.

I just left it on Battery Preset Smart Lithium(Lifepo4) so absorption 56.8 and Float 54.0 and I left the expert switch off

 

[chrisski]

I don’t have experience with exactly what you’re saying, but I do have two Overkill BMS’s for 2 X 280 ah 8S 24 volt batteries. I have never tripped those low voltage before, but I have tripped a smaller 24 volt portable homemade solar generator BMS and I have also tripped a bigger house battery.

IME, reactiving a BMS needs a proper voltage with a small amperage to wake a BMS up, and is not picky where this voltage comes from.

If my battery were to drain, I would hope one would still be able to jump the other (Useless in your example since you have 1 X 16S).

I also have a backup plan to jump It by taking the 2 X 12 V batteries out of my truck, and putting them in series for the 24 volts. If you have anyway of making a 48 volt pack this should work.

By jumping a battery, this is the part of the Overkill manual where you may have to put a 48 volt load from positive terminal to negative terminal, which bypasses the BMS and since it finally see an acceptable load, it will turn the BMS back on.

I think when you mention the MPPT, I think this is what you may mean bypassing the BMS with the current, which I think should work, but I would want to limit the BMS to 1 amp before I tried it.

I did have to bypass the BMS to activate it on a couple of batteries with the method I mentioned above because of low voltage cutoff. I used a power supply.

For my 48 volt battery for my house, when that died, that was brought to life with a tiny power supply with the terminals on the outside. If that did not work, then the procedures were to take it apart and jump the battery by bypassing the BMS.

========

On a separate note, I decided capacity checking my Grade A Cells would produce no usable data since I had the test data from the factory and top balanced them prior to install. Would not matter if they had 280 ah, 290 ah or 260 ah. I never plan to go down to 10% SOC, and in case I did, I use a low voltage cutoff well above the 260 ah level I mentioned.

 

[james1]

Thanks for describing your handling of this situation. And I think I will reconsider not doing a full capacity test after all cells are top balanced since they are new grade a.
But at least I can be assured that my Victron Smart controller will wake it up if I accidentally drain below cutoff(because of sunshine_eggo's excellent response)

 

[james1]

And thanks again for responding. Every response always gives some new insight into this whole world of solar.

 

[james1]

Victron absolutely, positively will provide absorption voltage (and current if something is connected) at the battery terminals even if a battery is not there. They can be powered exclusively by PV. It does need to be connected to a battery ONCE to set the system voltage, but then it can be disconnected.

Additionally, since most BMS will trigger short circuit protection due to connecting the battery to the inverter, this is avoided as the MPPT will charge the caps. Once the BMS comes out of protection, there is no significant surge when the inverter turns back on.

I validated this when I disconnected my battery from my system, and my inverters kept running... powered directly by the MPPT.

All that said, you should set your equipment to turn off BEFORE BMS triggered protection just like you set your charger to terminate charge BEFORE hitting BMS limits. That's just best practice and minimizes the potential for issues.

The ONLY complication I foresee is you might need to turn your inverter off or disconnect it temporarily if it's powering loads when it comes back on. The battery/MPPT might not be able to keep up.

This is another verification of your excellent response:
(This was sent to me by support at Overkill Solar)
"I have a Victron MPPT 75/15 in an out building with a 4s BMS and yes the Victron does wake the BMS up in the morning if the battery shuts off. I have had in use ~2 years without issue"

 

[james1]

This is another verification of your excellent response:
(This was sent to me by support at Overkill Solar)
"I have a Victron MPPT 75/15 in an out building with a 4s BMS and yes the Victron does wake the BMS up in the morning if the battery shuts off. I have had in use ~2 years without issue"

Actually I don't mean it's a verification of your response, it's a verification of the concept that you so well described.