My Renogy DC-DC charger says "Connect the ACC wire if you have a smart alternator". What if I don't do it?

[overl4nd]

The Title is basically the question. As per from what I could gather from the docs, without the ACC wire if the voltage falls below 12.5 the house battery will stop charging unless I have the ACC connected. So I will have periods of no charging happening. Any other downsides?

 

[mikefitz]

. Any other downsides?

You won't get a charge into the house battery. It's possible the vehicle battery won't drop that low, 12.5 volts. Perrhaps a trail drive with a volt meter connected would give an idea as to the situation .
The DCC50 has reverse charging of the vehicle battery from the house battery, its not clear from the liturature what conditions trigger this.

 

[uksuntimes]

I found a few things with mine

- I had to connect the signal switch. So I used the fuel pump fuse to get the live signal using a piggy back fuse holder.

- when your house batteries hit 100%, and if you have solar, it’ll then start charging the starter battery assuming the car isn’t currently running

- if you have solar connected, regardless how little current is coming in, then the charger will only take a max of 25amps from the alternator when it’s running. If you don’t have solar, it will take 50amps from the alternator when it is running.

So for the last part, added a relay on my solar cables that disconnect them from the charger when the car is running. That way whenever I am driving, I get the full 50amp charging.

 

[uksuntimes]

Added bonus of maxing the amps from alternator is that means I could charge my 200ah battery to full in 2 hours from the car engine if really needed / easy top up of power if the weather is no good for solar during winter etc. Without the relay / without disconnecting the panels, it would take twice as long. Not a deal breaker but certainly changes the efficiency.

 

[uksuntimes]

But as for your specific question. I’m not aware of any other issues but I imagine it depends on your specific car battery and alternator to some extent. Different smart alternators do different things. I think the main thing is to ensure your alternator actually provides enough amps / power because the DC charger will “open” and ask for the charge. But if the alternator stops putting out enough volts because it thinks your car battery is charged enough (yet that remains below the trigger point) and you don’t have the signal cable to say the alternator is running … then you’d never be charging your house battery in that state while driving.

I could be mistaken. This was just my understanding. I’m still a beginner.

 

[Hedges]

I think what's happening is some alternators, when there is light load, turn off and let electrical system run off battery. I observed low voltage in my Honda Civic, thought alternator had failed, may have bought a new one. It of course behaved the same. Whenever I turned on lights, voltage came up to what I expected.

If you know you have the issue while driving, just turn on your lights.

The DC/DC may be looking for ripple from alternator, not voltage. Either way, it would me you get no charge to house battery under some conditions. When you first start car, I'd expect alternator to recharge starting battery, and so DC/DC would start charging house battery, and that should keep alternator active. But if house battery is lead-acid, as current tails off, might cause alternator to sleep and you'd fail to get full absorption. Depends on alternator's switching threshold, and maybe PV panels will finish the job.


You ought to be able to find a switched wire somewhere. Older cars, that was simply ignition coil terminal.

 

[overl4nd]

Thanks for your answers. I will use a fuse tap cable and tap into one of the unused fuse blocks in the car. I don't plan to add solar. So its just car 30A

 

[Hedges]

Your car may have an "accessory" position for ignition key. That lets you operate radio, maybe windows, without the larger drain of ignition system and fuel pump.

Avoid using that signal, because if someone enables radio while sitting with engine off, it will run down the starter battery. Need to find a wire that only comes on with ignition, not just accessory.

Does your vehicle even have a smart alternator? If not, shouldn't be any need to connect this wire.
The way to determine is connect a volt meter, e.g. to cigarette lighter outlet or any other point, and operate the vehicle. It will be 14.xxV for a while, and if it later drops to 12.5 ~ 13.0V, that's a smart alternator. If it remains at charge/float voltage, it isn't.

 

[overl4nd]

I connnected the 30A Renogy charger today and drove around. My vehicle does not have an alternator. The OBD showed voltage always above 13.5V when truck was on, did not matter whether engine was running or not. Dropped below 12.5 when the truck shut down, turning off the DC-DC charger. Looks like I wont need the ACC cable

 

[MisterB1959]

I connnected the 30A Renogy charger today and drove around. My vehicle does not have an alternator. The OBD showed voltage always above 13.5V when truck was on, did not matter whether engine was running or not. Dropped below 12.5 when the truck shut down, turning off the DC-DC charger. Looks like I wont need the ACC cable

Did you mean that your vehicle doesn't have a smart alternator?

 

[MisterB1959]

I found a few things with mine


- if you have solar connected, regardless how little current is coming in, then the charger will only take a max of 25amps from the alternator when it’s running. If you don’t have solar, it will take 50amps from the alternator when it is running.

So for the last part, added a relay on my solar cables that disconnect them from the charger when the car is running. That way whenever I am driving, I get the full 50amp charging.

That's interesting. I need to check on mine when I get chance or start using it again and introduce a 12v relay if necessary. Which relay did you use?

 

[MisterB1959]

I found a few things with mine

- I had to connect the signal switch. So I used the fuel pump fuse to get the live signal using a piggy back fuse holder.

- when your house batteries hit 100%, and if you have solar, it’ll then start charging the starter battery assuming the car isn’t currently running

- if you have solar connected, regardless how little current is coming in, then the charger will only take a max of 25amps from the alternator when it’s running. If you don’t have solar, it will take 50amps from the alternator when it is running.

So for the last part, added a relay on my solar cables that disconnect them from the charger when the car is running. That way whenever I am driving, I get the full 50amp charging.

Are you talking about a combined DC-DC MPPT charger or just a standalone DC-DC charger?

 

[overl4nd]

Did you mean that your vehicle doesn't have a smart alternator?

My vehicle does not have any alternator. It is a hybrid so it has a hybrid battery pack charging the Lead Acid battery. It also connects to a motor generator which spins the engine whenever it shuts off (hybrid keeps shutting off during stops and coasting)

Are you talking about a combined DC-DC MPPT charger or just a standalone DC-DC charger?

Its the MPPT.
Input : PV, Alternator
Output : Lifepo4 battery

I don't have any PV panels, but got this one just in case I do a future upgrade

Its a 30A Renogy MPPT DC-DC charger

 

[uksuntimes]

Are you talking about a combined DC-DC MPPT charger or just a standalone DC-DC charger?

Combined 40a one from renogy for me.

 

[uksuntimes]

That's interesting. I need to check on mine when I get chance or start using it again and introduce a 12v relay if necessary. Which relay did you use?

all the commentary and suggestions etc happened here

What type of relay turns things OFF when the ignition 12v comes on? [SOLVED]

This was solved thanks to everyone's help. Details and items are in all the posts below for anyone else that might arrive here one day :) ---- ORIGINAL MESSAGE Hey everyone! I am struggling to know what to search for and would love a little guidance as I suspect there is a special type of name...

diysolarforum.com

 

[overl4nd]

After using it for some time, it is clear that the aCC wire connection is not needed at all. Even when engine is off (car on) the Renogy charger is charging at 19A and shutting down when vehicle is turned off. The voltage at battery stays over 13.5V when you start the vehicle irrespective of the whether the gas engine is on or not.

However I did discover that if the lithum battery goes to zero the Renogy will not charge it anymore. I discharged the battery 100% and had to use an AC charger to charge it a bit before the Renogy kicked in.

AC charge 20A + Renogy in parallel showed me 38A charging current.

 

[overl4nd]

Okay I was wrong. I finally went on a long drive, and after quite some time the voltage dropped and it shut off. Since everything is on can bus, I am having a hard time getting a IGN activated fuse. But the wiper blade fuse seems to be it.
Otherwise, will just use the 12V socket to provide the signal, it can't be more than half an amp I guess

 

[uksuntimes]

Okay I was wrong. I finally went on a long drive, and after quite some time the voltage dropped and it shut off. Since everything is on can bus, I am having a hard time getting a IGN activated fuse. But the wiper blade fuse seems to be it.
Otherwise, will just use the 12V socket to provide the signal, it can't be more than half an amp I guess

Do you have a fuel pump fuse? That’s what I use.

 

[overl4nd]

I am scared to touch the critical fuses, will probably go for Wiper fuse of USB 7.5A fuse. The ACC wire should pull very little current