Renogy DC-DC Charger relay

[Murray Argo]

I am adding a renogy dc-dc charger to my van. I know I need to hook the remote signal wires up to an ignition wire as well as the EXT IO3 in between. Should I do this with a simple relay or could this cause issues?

[Dacian Todea]

You will likely use the IO3 for inverter or other loads while the IO4 can be directly used in series with the ignition on renogy but if you need the IO4 for some other charge sources like maybe the DSSR20

The EXT IOx are Toshiba optoisolators TLP187 in case of v02b SBMS0 and they are capable of max 50mA.

So if you have multiple remote ON/OFF charge sources you will need some similar optoisolators one for each charge source and then all of those will be controlled by EXT IO4 set as type 1

If you do not want to solder anything you can search for the MRD-060D2 you should find them at 5 to $7 each.

[Murray Argo]

I mean what should be used to put IO4 in series with the ignition wire? I am planning to run the DC-DC positive to the vans battery block and not the alternator. So The DC -DC charger can only be on when it has signal from both the ignition wire and IO4

[FilterGuy]

Connect your ACC to ExtIO4+ and then connect  ExtIO4- to the Renogy.   The Renogy control is a high impedance input so it will take very little current.   Consequently, you can use almost any wire.   I like 18AWG for things like this.  For safety, put a 470ohm to  1Kohm resister in the line close to where you tap into the ACC.    If a short happens, the resister will limit the current to a non-damaging level.

With that set-up,  ACC has to be on and the BMS has to turn ExtIO on before the Renogy will turn on.

[Murray Argo]

Do I need to change any settings or anything? I have it all hooked up. I am getting voltage to ExtIO4+ but nothing out of ExtIO4-. 

[FilterGuy]

You need to set the ExtIO you are using (ExtIO4?) to type 1.

https://diysolarforum.com/resources/electrodacus-sbms0-i-o-summary-chart.112/

Before you do that you may want to hook the ACC directly to the Renogy and measure the current.   (The SBMS0 has a limit of 50mA).    It is most likely fine but If it measures to be higher than 50mA,  let us know.

[Murray Argo]

Okay, ExtIO4 is set to 1 already. So I guess thats not the issue. Could it be because my aux battery and my starter battery do not share grounds? so maybe the acc is not giving the sbms signal? Not sure if it works that way

[FilterGuy]

First,  Lets make sure I understand your wiring.

The resistor is there as a current limiting safety.

If you are sure you have voltage at pin 12 and no voltage at pin 11,  then the SBMS0 is not turning on EXTIO4.   

1) Try putting the ACC directly on the D+ pin of the Renogy.   Does it turn on?    What is the current?

2) Does the SBMS0 think the battery is in an over-voltage condition.

Note, The grounding of the renogy vs the SBMS0 should not matter.

[Murray Argo]

correct. I got it working now. I changed the acc wire. Still not sure what the issue was but its good now. 

How can a shunt be added at this point to calculate soc? The shunt would not go to the ADC1 wires would they?

[FilterGuy]

> How can a shunt be added at this point to calculate soc?

That is shown in the manual.    (One warning:   Do not put a disconnect or fuse between the battery + and the shunt.    If the fuse blows or switch opens it can damage the SMBS0.

In addition, here is a supplement to the manual that I have pulled together and posted on a different forum:

https://diysolarforum.com/resources/electrodacus-sbms0-i-o-summary-chart.112/

[Murray Argo]

I have the sbms40. Sorry I didn’t specify that. I don’t really remember seeing charge shunts in the manual. I assume it can be done similar to the sbms0 manual?

[Dacian Todea]

FilterGuy, Thanks for all the support provided.

Murray,  See the SBMS40 manual there is a battery shunt that can be added ADC1n/ADC1p and there is where you will connect the inverter if you have one and als where you will connect Renogy DC-DC that way the SBMS40 can see the current and correctly calculate the SOC.

[Murray Argo]

Dacian, Do I need to turn extload on in the settings, even though this is a charger and not an inverter in my case? 

Currently I have ADC1N on the charger side of the shunt and ADC1P on the battery side of the shunt. I have external load set to on and the shunt resistance value put in. Will this charge current show up anywhere in monitoring?

[Dacian Todea]

Yes the EXTLoad needs to be turn ON (set to 1) in settings as that activates the external current shunt measurement. Yes the battery current will show the current provided by the charger.

So if there is no load and no other charge source connected you will see the battery current as a positive current going in to battery not sure if you have the 20 or 40A version but you will see 20A or 40A respectfully or very close to that. Of course SBMS0 charging will need to be enabled that means battery not full and your engine will need to be ON.  

[Murray Argo]

I noticed that when the 40a charger is on, I see +100 on the battery reading for the sbms40. I do not see anything in extload, is this correct? Not entirely sure why its +100 amps instead of 40amp. I assume I messed up something with the config of the shunt

[Dacian Todea]

Do you see 0A when charger is OFF ?  If so then yes you set the current shunt resistance value incorrectly.

[Murray Argo]

0A in the Batt row? When the charger is off I am currently seeing +0.2A in Batt. I also have solar connected

[Dacian Todea]

How many panels ? is it sunny ? +0.2A sound very low.  Hope is not the solar that was connected when you powered on the SBMS0 and incorrect EXT IO4 connected not able to turn OFF the solar.

Seem like you mentioned you have the SBMS40 and for that you normally do not mess with the  internal shunts value only the external one.

Where have you connected the external shunt ? Maybe some photos will be needed.  Hope you do not have the external current shunt between the battery+ and the Batt+ connector on the SBMS40 as then you will measure the current twice.

A few photos with the connections and maybe what you set in ADC menu and the diagnostic screen will be helpful.

[Murray Argo]

I can't upload pictures for some reason. Server is rejecting it, but I have 2 100w panels and it was raining. 

I have the battery positive going to a positive bus bar. The SBMS40 Batt+ also goes to this bus bar. The shunt for the charger is coming off of this busbar as well. let me know if this is not correct. 

The ext adc values are as follows:

1

Extload shunt 0.1500

extload offset 0

[Dacian Todea]

Murray,

The Batt+ needs to connect directly to Battery+ terminal with nothing in between. If the external current shunt is between the Battery+ and the SBMS40 Batt+ that may explain why you see such a large current as current will be measured twice.

What is your shunt spec ? If your shunt is 500A / 75mV then 0.1500 will be correct else is likely incorrect.

You can send me the photos trough email.

[Murray Argo]

I connected batt+ directly to the terminal. That seems to have fixed the issue with the reading. I am getting about 15amps at idle. Seems about right. My shunt is 500A/75mV.

 I did notice that the sbms was turning the pv and charger off and back on in a matter of seconds. I assume this was because I was at a pretty high SOC and the dc -dc charger brings one cells voltage high enough to trigger the charger to turn off, then when the charger is disconnected the voltage falls a little and lets the charger turn back on?

[Dacian Todea]

What do you mean by 15A idle (What is at idle?)

You should maybe check your cells connections and it should be minutes and not seconds between charging turning ON and OFF

Or maybe your battery is to small for the charge/discharge rate you are using at.

[Murray Argo]

My battery is about 200ah. Is there an instance where the sbms would turn the dc-dc charger off for 30 seconds or so? The charger turns on and off constantly. I checked the voltage at my cells in relation to what the sbms is showing. the largest drop I had was one cell showed 3.36 on the volt meter compared to 3.33 on the sbms 

[Dacian Todea]

Check that none of the EXT IOx are set as type 6. If any is set as type 6 set it to type 0.  As if there is an EXTIOx set as type 6 it will think you have a dual PV array and try to switch to second array for lower charge current.

[Murray Argo]

None of the EXTIOx are set to 6. I am only using EXT IOx 4, which is set to type 1.

[Dacian Todea]

You have a 200Ah battery and I think you charge at max 40A ?  What is discharge current when you see that cycle 30 second ON/OFF ?

You likely have a bad connection between cells or maybe you changed the default settings.

What is your overvoltage ? Overvoltage Lock ? Overvoltage delay ? and Overvoltage recovery ?

[Murray Argo]

Discharge current was not very high. I'm using all 12v, fridge, lights, glow plug for diesel heater at times. 

I do not believe I have ever changed the advanced settings.  

over voltage is at 3.58v

overvoltage lock is at 3.75

end of charge is 3.55

It seems like the dc-dc charger start turning on and off around 3.58 but it does not stay off.

[Dacian Todea]

What is the overvoltage recovery set at ?

For the charger to be allowed to start again highest cell voltage needs to drop below that over-voltage recovery limit say 3.4V

If it only takes 30 seconds or less for that to happen it means that maybe charge rate is to high for your battery but 40A charge for a 200Ah should be fine. It may also be possible that connections between cells are not that great so high contact resistance.

You can decrease that over-voltage recovery a bit maybe to 3.35V but I will first check that connections between cells are good. You can check the voltage drop on the connection while under a known load or known charge current (multi-meter set on mV) then you can calculate the contact resistance.

It may also be that cells are fairly low temperature as internal resistance increases quite a bit with lower temperature.

It will typically take minutes between charge stopping and re-enabling not seconds.