What is going on with my Renogy 40a DC-DC charger?

[Rob.]

I installed my Renogy 40a DC-DC charger a few days ago, and everything is not going smoothly!

I would say I have a reasonable knowledge of 12v wiring - I've been installing car audio for myself and friends for about 20 years, but there's certainly a lot I don't know.

I'll try to keep it as brief as possible:

• I have a Yinglong LTO lithium main battery (charges at 15v, floats at about 14-14.4v), then 2 x 50mm2 pos and neg cables to the back of the van to a copper bus bar. The Renogy ALT- and ALT+ are connected to this bus bar with 4awg cable, then the BAT- and BAT+ to 4 x 280ah LiFePo4 cells via a JK BMS. It's all charged via a 210a non-smart alternator.
• When I first wired up the Renogy, it stayed on permanently. The main battery used to last about 14days before needing a top up charge, but it was flat within 2 or 3.
• When checking the JK BMS app, the Renogy was charging the leisure battery even with the engine off. It was charging in 38A bursts of only a few seconds, then stopping. This would repeat, presumably indefinitely.
• I went for a drive to get some charge into both batteries. The JK BMS app was still only showing short bursts of charge, even with the alternator putting out 15v (over about 30 minutes). I was expecting a constant charge, as the SOC of the leisure battery is showing at about 70%
• I unplugged both + connections from the Renogy and left it overnight last night. When re-wiring this morning, I connected the IGN+ plug to the remote turn on from my Kenwood head unit (also powering 2 x amps) as I read a few posts online of people having similar issues with the auto-sensing of the Renogy DC-DC. The Renogy powered up, even with the ignition off. I primed the ignition, head unit and amps turn on. Turn off the ignition, head unit and amps turn off. Renogy stays on

Am I doing something wrong? Or is something not right with this Renogy charger?

Thanks,

Rob

 

[Dellmassive]

Got some pics?

What Renogy dc-dc you got?

 

[Rob.]

Excuse the mess - I need to clip a lot of them back.

 

[Rob.]

Also, I timed the charge cycle. It's 33s on, then 2m15s off. Strange!

 

[Sim60]

You are using the renogy to charge your lifepo4 cells from the Yinglong battery?
I would say the Renogy is expecting a lead acid battery and the Yingling voltage is too high.
From the manual:-
.....Traditional DC Alternator (IGN connection not required): The starter battery begins charging the
auxiliary battery when its voltage reaches 13.2V & 15s and stops charging when the voltage drops to
12.7V.
.....Smart DC Alternator (IGN connection required):The starter battery begins charging the auxiliary battery when its voltage reaches 12V & 15s and stops charging when the voltage drops to 11V.

 

[Rob.]

You are using the renogy to charge your lifepo4 cells from the Yinglong battery?
I would say the Renogy is expecting a lead acid battery and the Yingling voltage is too high.

Yes. That could be true, but surely the IGN feed should shut it down when 0v is detected? Or does the starter battery voltage override the IGN sensing?

I read some posts online about installing a 40A relay on the Renogy + feed, giving the ability to properly turn it off.

 

[Sim60]

You’ll have to check with renogy, but may default back to standard alternator settings when IGN+ is off

 

[Rob.]

You’ll have to check with renogy, but may default back to standard alternator settings when IGN+ is off

I raised a case with them online today. I found another thread on here that referred to the charger still staying on based on starter batt voltage, despite the IGN wire being used

 

[Rob.]

Renogy responded to say they believe it's faulty, so they have sent me a return shipping label.

 

[Rob.]

Well, within 2 minutes of fitting the replacement it's clear it does the exact same thing. Clearly not faulty, but seemingly not compatible with a lithium starter battery!

May have to try out Victron instead.