Renogy 3000w inverter charging voltage spikes

[swest99]

Hey Everyone!

I'm new to solar but did lots of research before attempting to setup my own system.
My current setup:
1. 3000w Renogy inverter/charger
2. 60 amp Renogy Rover MPPT
3. 800w solar (not currently hooked up)
4. Two sok 206 ah lithium batteries in parallel

I've set my inverter to charge the batteries according to Renogy and the SOK recommendations.
Charge voltage: 14.6v
Float voltage: 13.6v
Reconnect voltage 12v (thats the lowest the inverter will go)
Cut off voltage: 11.2v

I currently am using a 15 amp to 30 amp conversion cord, and I've set the incoming amperage to 15 amps.
My system has mainly 12v (lights, outlets, hw heater ignition, stove ignition, fans) with the exception of about eight 120v outlets used for a fridge and other basic appliances.
When the system isn't utilizing the charger function on the inverter, it works well. As soon as I try to charge the batteries using the incoming shore power, the voltage/amperage jumps sporadically. So much so, that I will get overcharge cutoff or fault codes.

What's the potential reason for voltage spikes? Could it be the inverter, the batteries, or both? I'm wondering if perhaps the batteries and inverter aren't synced properly... maybe the inverter is getting bad information about the batteries soc causing it to have this issue.
Any input is welcome!

 

[chrisski]

You may drop the incoming amps to 12 amps.

There's an 80% rule where you shouldn't be pushing more than 12 amps for extended periods. 15 amps for a short time is OK. 12 amps is around 1400 watts and 15 amps around 1800 watts.

I'm not sure how you have the 15 amp wired, too small a wire and there could be voltage loss, especially if a longer run.
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You could take voltage readings at different points along the circuit and find out if there's any loss. There will be some, but something excessive is what you're looking for.
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15 amps does not seem like much to charge that bank. 15 amps at 12 volts is around 180 watts for a around 5 kWh battery bank.

 

[Rocketman]

Your settings are off.

Drop the charge voltage down to 14.4 (at a max - I use 14.2 - but different bms).
Drop the float to 13.5v
What is reconnect voltage?

Cutoff - raise it up a bit 11.5v

My guess is the voltage spikes are caused by the BMS shutting off - because cell voltage is too high. (Can you verify that? Does your bms have Bluetooth?)

 

[Rocketman]

I believe when he says he has 15a incoming - that is 15a @120v - or 1800w or enough 12v charge to charge the battery at over 100amps.

Also you need a shunt based battery monitor. Like a Victron Smartshunt or BMV712. I know there are others.

 

[swest99]

You may drop the incoming amps to 12 amps.

There's an 80% rule where you shouldn't be pushing more than 12 amps for extended periods. 15 amps for a short time is OK. 12 amps is around 1400 watts and 15 amps around 1800 watts.

I'm not sure how you have the 15 amp wired, too small a wire and there could be voltage loss, especially if a longer run.
========
You could take voltage readings at different points along the circuit and find out if there's any loss. There will be some, but something excessive is what you're looking for.
========
15 amps does not seem like much to charge that bank. 15 amps at 12 volts is around 180 watts for a around 5 kWh battery bank.

Thanks! That's good info. I originally set it at 15amps because that's what renogy support recommended. I'll lower it down and check the voltage along the way.

I did wonder if it had to do with the incoming voltage. I don't currently have access to a 30 amp hookup but I thought I'd see if this could be sorted out with what I have.

The odd thing is, I've had the cycle work perfectly on a few separate occasions. The voltage lowered to the low setpoint, then the charger kicked in and charged to the high setpoint.

I'll also mention that this voltage spike during charging is happening before the batteries are low enough to trigger the charger.

 

[swest99]

I believe when he says he has 15a incoming - that is 15a @120v - or 1800w or enough 12v charge to charge the battery at over 100amps.

Also you need a shunt based battery monitor. Like a Victron Smartshunt or BMV712. I know there are others.

I do have the renogy shunt.

 

[swest99]

Your settings are off.

Drop the charge voltage down to 14.4 (at a max - I use 14.2 - but different bms).
Drop the float to 13.5v
What is reconnect voltage?

Cutoff - raise it up a bit 11.5v

My guess is the voltage spikes are caused by the BMS shutting off - because cell voltage is too high. (Can you verify that? Does your bms have Bluetooth?)

Gotcha. Good info. The reconnect voltage is 12v. Again, most of this info was from the SOK specs.
I do have Bluetooth, but the app is basically garbage from what I've experienced.

 

[Rocketman]

How many amps are you charging the batteries at? Can you control the output charging amps?

It could be the inverter/charger is trying to push way too many amps at the batteries - (which I think is what @chrisski was saying).

The SOK app might be garbage (I don’t know - don’t have those batteries), but it should be able to tell you the cell voltages and why the bms/battery is shutting down? Overamps, overvoltage, or cell balance. Each of those has a different fix.

 

[swest99]

How many amps are you charging the batteries at? Can you control the output charging amps?

It could be the inverter/charger is trying to push way too many amps at the batteries - (which I think is what @chrisski was saying).

The SOK app might be garbage (I don’t know - don’t have those batteries), but it should be able to tell you the cell voltages and why the bms/battery is shutting down? Overamps, overvoltage, or cell balance. Each of those has a different fix.

So, the utility charger amperage setting is currently at 15 amps. I have dropped it down to 10 amps in the past but didn't see any change in the voltage spiking.

Okay, I'll take a look at the app to find out more information.

Thanks for the input!

 

[mikefitz]

I've set my inverter to charge the batteries according to Renogy and the SOK recommendations.
Charge voltage: 14.6v
Float voltage: 13.6v
Reconnect voltage 12v

It's probable the batteries BMS is shutting down the charge path due to cell over volts. The charger cannot respond fast enough and you get voltage spikes.
I suggest.
Charge volts 14.2 volts, ( lower to 13.8, or 14.0 if you still get voltage spikes)
Float volts 13.4 volts