Multiple charger mayhem ...

[richierni]

Hi, this is a follow on to Elektroblock 252 solar connection question - cable sizing

I'm currently lead acid and slowly en route to going Lithium. First step was to add a Renogy DCC30S (30A) combined DC to DC charger and solar controller. I've added the solar via the Renogy and my EBL's solar inputs, all working grand.

Next step is to add the B2B capability of the Renogy. I believe I can do this by removing the existing starter battery wire from the back of the EBL and connecting it to the Renogy input instead. Then take the Renogy output into the EBL, effectively putting the Renogy inline. I'll also remove the current solar specific connection from the Renogy to the EBL as the Renogy will combine the solar/alternator charging and supply it directly to the EBL which will pass it to the house battery.

My question relates to how the Renogy decides when to charge via B2B - it just bases it on the voltage of the starter battery rather than a D+ connection to tell it when the engine is running, which was a bit of a surprise! Here's the section from the manual:

So, now I'm wondering what happens when I'm on EHU. The EBL will trickle charge my starter battery, presumably at > 13.2V, which will trigger the Renogy to start charging the house battery, which the EBL is already charging via the mains charger ...

What on earth will happen!?

 

[Lenny HB]

So, now I'm wondering what happens when I'm on EHU. The EBL will trickle charge my starter battery, presumably at > 13.2V, which will trigger the Renogy to start charging the house battery, which the EBL is already charging via the mains charger ...

What on earth will happen!?

YEP, that is what will happen it is always best to operate the B2B via the D+ so it only turns on when the engine is running.
Also better to connect the output from the B2B direct to the leisure battery not via the EBL.

 

[richierni]

YEP, that is what will happen it is always best to operate the B2B via the D+ so it only turns on when the engine is running.

Well, I agree, but from my reading of the manual, the Renogy doesn't allow that. You can connect a signal wire but it says only required for smart alternators, and even then it doesn't seem to be used as a trigger as you can see from the table in my post.

 

[autorouter]

As Lenny HB says, the Renogy device will start charging the leisure battery from the starter battery. But actually it's worse than Lenny HB says, because even if you trigger the Renogy from a D+ signal, it will still turn on when the voltage rises above the threshold. It's a known feature of that Renogy device, and Renogy recommend that you put a relay in the starter battery input wire, triggered by a D+ signal, so it only turns on when the engine is running and the alternator is sending a D+ signal.

Other B2B chargers have had similar problems in the past, such as the Sterling B2B, which was fixed by an extra mode added called Pure Ignition Mode, that turns on the B2B only if a D+ signal is present, regardless of voltages. All the Victron B2Bs can be put into a pure D+ mode that disregards any voltages. Presumably Renogy are working on the problem and may eventually come out with a new improved model, or maybe even a firmware upgrade with any luck.

 

[richierni]

Thanks guys, just found another thread on the subject, wish I'd found it before I bought the Renogy charger! Seemed the perfect device given it did solar and B2B and I've limited space, but this is a pretty dire flaw!

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[G7UXG]

You could take a look at the Votronic VBCS triple chargers if you have limited space. They are Solar/B2B/Mains. B2B is via D+

I’ve had one fitted for 4 or 5 years now without any problems.

Original systems still in place, so if Votronic unit fails, I can revert to originals fairly easily.

 

[Pausim]

Can you return the Renogy if it is still unused?

 

[richierni]

Unfortunately I'm already using it for solar, I've opened a "case" with Renogy to ask the questions about why it works like this, will let everyone know what they say just in case there's any new info.

Just had one thought, I think the EBL uses D+ to close a relay to connect the starter battery to the house one when the engine is running. Does this mean they're not connected when the engine is not running? And if so, having the EBL in line between starter battery and EBL, would this stop the Renogy B2B charging when the engine stops which is exactly what I want?

The complicating factor is when on EHU. Will that close the relay again and allow the Renogy to start B2B again? Or is mains charging via a separate connection in the EBL?

Clutching at straws ...

 

[Pausim]

Unfortunately I'm already using it for solar, I've opened a "case" with Renogy to ask the questions about why it works like this, will let everyone know what they say just in case there's any new info.

Just had one thought, I think the EBL uses D+ to close a relay to connect the starter battery to the house one when the engine is running. Does this mean they're not connected when the engine is not running? And if so, having the EBL in line between starter battery and EBL, would this stop the Renogy B2B charging when the engine stops which is exactly what I want?

The complicating factor is when on EHU. Will that close the relay again and allow the Renogy to start B2B again? Or is mains charging via a separate connection in the EBL?

Clutching at straws ...

Possibly not totally clutching at straws in that the split charge relay in the EBL should keep the B2B from connecting to the leisure battery when the engine is off. However if the Renogy outputs the solar down the same output then that will also be separated, no idea how this combined unit is wired or works. I also suspect that having the B2B live when it shouldn’t be is probably inefficient even when it is prevented from outputting. I would be thinking about adding a D+ activated relay to the engine battery connection to the B2B to stop it working except when the alternator was active.

 

[Lenny HB]

Unfortunately I'm already using it for solar, I've opened a "case" with Renogy to ask the questions about why it works like this, will let everyone know what they say just in case there's any new info.

Just had one thought, I think the EBL uses D+ to close a relay to connect the starter battery to the house one when the engine is running. Does this mean they're not connected when the engine is not running? And if so, having the EBL in line between starter battery and EBL, would this stop the Renogy B2B charging when the engine stops which is exactly what I want?

The complicating factor is when on EHU. Will that close the relay again and allow the Renogy to start B2B again? Or is mains charging via a separate connection in the EBL?

Clutching at straws ...

It would work for when the engine isn't running but not EHU as the EBL uses the fridge connection to the starter battery for charging on EHU. Also it wouldn't when solar is charging, more important to stop it working when on solar.

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[richierni]

Thanks Pausim and Lenny HB I'd completely forgotten the solar aspect.
Yes, the solar & B2B do go via the same output from the Renogy which internally prioritises solar over B2B and merges the two up to the defined max current output. So if the Renogy is inline between the starter battery and the EBL and the EBL cuts the connection between starter and leisure battery when the engine isn't running, I'd only get solar charging when the engine is on
So looks like having the Renogy inline like that just isn't an option at all.
I guess I'll have to work out how to wire it direct to the leisure battery and use a relay as others have mentioned.

Is there a way to stop the EBL doing alternator charging (because I'll be doing it via the Renogy) but keep it charging when on EHU?

 

[Lenny HB]

Is there a way to stop the EBL doing alternator charging (because I'll be doing it via the Renogy) but keep it charging when on EHU?

Disconnect the starter battery input on the back of the EBL or pull the 50 amp fuse at the other end of the cable.
It won't affect charging while on EHU that is done via the fridge connection.

 

[richierni]

That sounds perfect, thanks all! I'll draw a logical diagram and post it here shortly just to confirm my understanding.

 

[richierni]

So, how's this look? What have I forgotten? Appreciate any reviews.
Still no reply from Renogy support on my questions as to why on earth it works like that, will report back when they do respond.

 

[Pausim]

That looks ok to me but I would wait for the real experts Lenny HB and autorouter to comment.

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[Lenny HB]

Looks OK, don't forget to fuse everything.

 

[Trackman]

You could take a look at the Votronic VBCS triple chargers if you have limited space. They are Solar/B2B/Mains. B2B is via D+

I’ve had one fitted for 4 or 5 years now without any problems.

Original systems still in place, so if Votronic unit fails, I can revert to originals fairly easily.

For anyone considering buying a similar unit, I'd give the Votronic one a favourable comment too.
My one is brilliant for our needs. The original one, fitted by our van's converter, failed at about 2 years old. That sounds bad, but I contacted both the converter (SMC) and Votronic. Fortunately the converter replaced the unit free, under warranty, but Votronic also responded promptly with an offer to replace it if I couldn't get it changed by the converter.
Good service by both organisations imho.