Help with my Renogy 30amp DCDC MPPT

[Craig07]

Hi All,
I'm new to the forum and was wondering if anyone could help.

I have a Renogy 170A Lithium battery working in conjunction with the 30amp DCDC MPPT and Renogy Shunt, no solar connected as I'm having a custom rack built.

Anyway, something strange is happening and I'm struggling to figure it out, basically when I have the engine running the DCDC MPPT shows a green light and it's display shows the battery is fully charged but when I look at the shunt battery monitor is only showing 85% charged with no charge going in.

I'm getting 14.9V from the alternator.

The Lithium battery is at 12.5v when all loads are disconnected.

Any help with this would be appreciated.

Craig

 

[justinm001]

Are you able to adjust the voltage? I think that's pretty normal that it won't charge fully off a dc to dc charger unless the voltage is cranked up. It should use the dc to dc charger for the loads still.

My victron dc to dc chargers won't charge my 12v over around 80% but will charge my 48v closer to 95%. I believe it's because the batteries need a couple volts higher to get more charge and the dc to dc can't get there.

12.5v is very low like 15% charged

 

[Craig07]

Sorry, I cant adjust the voltage.
I've read that the DCDC chargers don't typically charge them to 100%, I previously I had my solar installed which would trickle charge them to 100%.
I'm so confused with what going on now, like you said 12.5v seems low but the DCDC MMPT is showing a green light like its fully charged and the display is showing full bars. The shunt is showing 85%.

Noticed something else now, when I have the engine running and put a load on the system such as my diesel heater, the DCDC MMPT display shows 7amps going into the starter battery and 7amps going into the house battery, the shunt display is still reading 85% with no charge going in.

Starting to think I have a damaged cell or something.

 

[justinm001]

Renogy gear is all junk so it's hard to tell but would bet it's the charger and not the battery. You certain you have it set to lithium?

What should happen is the dc/dc charger should be putting out just over 14v. The batteries will charge to a point then it'll sit idle and the dc/DC charger will pickup all loads up to that 30a or whatever the limit is set to. If the battery starts at 100 then it'll stay at 100 as long as you don't go over that 30a limit on the dc to dc charger. If you do then it'll use the battery for the additional load but not recharge unless it gets under that 80% or whatever.

You need to plug it into an actual lithium charger every once in a while. The dc/dc charger won't bring it high enough for the battery bms ro balance the cells so without a real charger like an ac to dc charger with a lithium profile you'll have issues. Not sure if the mppt part will do it when you get solar but maybe.

I keep a couple ac to dc cheap chargers off Amazon and they work. But haven't found a cheap 12v charger with multiple profiles that doesn't stay on when ac power is lost. They all seem to drain the battery when not plugged in because their screen stays on when connected to 12v.

 

[Craig07]

Hi, yeah totally get what you saying regarding the DCDC charger taking the load. was confused about the 7amp into the starter battery though.
The charger is set to Lithium. Was trying to avoid buying a lithium charger. My solar panel did keep it charged to 100% all of the time when it was connected.
Please see the attached pics of both monitors, my shunt is not reading any charge coming in at all and I should see at least 30amp coming in from the DCDC display whilst running but the DCDC charger thinks that the battery is full and will only provide 0.1 to boost.
Also, worried that 12.5v means 15% when both monitors are showing 85%

 

[uksuntimes]

How many amps are you getting from the starter/alternator? And are you using the switch cable to tell the DC charger that the alternator is on / have you tried to test with that cable connected and running 12v through it?

 

[justinm001]

Starter battery 7amps doesn't matter if the alternator is running likely the alternator was turned on by the dc/dc load then pumped some excess power into the lead acid.

The shunt needs to be calibrated to the SOC however it does it. Shunts just measure the flow in either direction and add up to calculate the SoC. Could be the battery size isn't right on the shunt or it needs calibrated.

Hook up an actual charger to the batteries and let it tell you the battery is full then see the voltage.

I think the issue is the DC-DC charger isn't charging for some reason. Could be the alternator doesn't have high enough voltage or the wiring. What gauge wire from the alternator to the DC-DC charger, and how long? Same with from DC-DC to battery. Cable size plays a huge role because voltage drop determines how much charge will get into the lithium.

When alt is running check the voltage alt, the starter battery, the ports on the DC-DC charger and the lithium. 14.4v is the ideal charge rate so needs power above that coming out of the DC-DC

 

[uksuntimes]

Also in the DC home app, you can change the settings on the DCMPPT charger to set what the target voltages should be. These are set by default by the profile you pick, e.g. Lithium, but can be overridden. However, proceed with caution / research before changing any of those values.

I use my Renogy DCMPPT to charge my Renogy battery to 100% from the alternator without issue, however I do not have any experience with the smart shunt / 3rd party batteries.

That said, the DC charger is picky with regard to alternator charging when just using the starter battery voltage sensing, especially if you have a smart alternator, so an easy test is as per the above, to try the signal cable that will then tell the DC charger the alternator is on/running and see if that changes what happens for you. Given it seemed to start doing something when you added 'load' it might suggest you have a smart alternator and the sensor wire (included in the box) may resolve the problem.

 

[uksuntimes]

Also, I know you said you have no solar connected, but can you confirm you literally have nothing - not even a 'dead' cable - connected to the PV+ on the DC charger?

 

[mikefitz]

Renogy 170A Lithium battery

These batteries can enter protection mode and indicates a voltage that's not true battery volts. Either a load of a few amps or a charge will cause the protection to reset and you should see the actual volts.

I'm getting 14.9V from the alternator

Where in the system, at dcc input or output?

Lithium battery is at 12.5v when all loads are disconnected.

It's entered protection. This is normal and something a competent battery designer would perhaps not incorporate in the design. Apply a small load and you will see the actual battery volts.

All the issues you are seeing are created by battery protection. Nothing is actually faulty, it's all down to Renogy selling product that's not really well designed. And as products are from different manufactures design teams there are sometimes minor issues when a system is put together.

The Renogy battery has slightly different capacity cells, and at 14.4 volts output from the DCC, the battery will encounter cell overvolts and enter protection. Because the battery has the charge path shutdown, it accepts no current and due to the volt drop across the internal management in shutdown mode the voltage seen 'outside' the battery is lower than expected.

 

[Craig07]

Good shout, I'll give it a test to check amps
All cable sizes are good with less than 1M runs between batteries.
The voltage at the alternator is 14.9v running into the DCDC charger.
When I installed the system about a year ago, I tested the alternator to see if it was producing a variable voltage which it was, so I hooked up the smart alternator cable and everything worked fine, I've since tested the alternator today and it producing a steady non changing 14.9V.
I do have a dead solar cable that is hooked up to the DCDC, checked the voltage at the connection and I have a slight draw, surely this isn't the culprit???

I'll give those "actual battery volts" a try just now...

Thanks to everyone so far......

 

[uksuntimes]

Disconnect the PV+ cable and try again.

 

[uksuntimes]

If there is even a tiny amount on the PV cable, the DC charger will only allow half the draw from the alternator.

This exact issue for me a few weeks ago meant my battery never charged to 100% from the alternator.

As soon as I removed the PV+ cable, it took all it needed from the alternator and fully charged.

Since then I have installed a relay so that if the car/alternator is on, it disconnects the PV so I get full charging from the alternator.
Still with the 12v signal cable that lets the DC charger know the alternator is running. Also, make sure it is plugged into the right port on the DC charger. I accidentally put it in the temp port before now.

Not saying this is your issue, but worth a quick/easy test.

 

[Craig07]

Slight voltage drop when applying a load....

 

[Craig07]

Sorry, this just refreshed, I'll remove the PV cable just now...

The cable is in the correct port.. ?

 

[mikefitz]

checked the voltage at the connection and I have a slight draw, surely this isn't the culprit???

This could backfeed from internal circuits.

How cold is your battery, it wont charge below 5deg C

 

[uksuntimes]

Sorry, this just refreshed, I'll remove the PV cable just now...

The cable is in the correct port.. ?

Look forward to the report. Any voltage on that terminal and it will half the allowed input from the alternator. So fingers crossed this solves your issue

Though as per Mike above, a cold battery will also resist taking any charge if the BMS is correctly protecting it.

 

[Craig07]

Sorry bud, disconnected the dead PV cable, and it still has the same results.

When I test the connection at the DCDC PV intake with nothing connected, I still get a 0.57v draw...

The battery is sitting at 6 degrees, Renogy states that 0-55 is optimal.

 

[uksuntimes]

When you have the car/alternator running, does the red 'alternator' light come on, on the DC charger? It should illuminate even if not taking any draw for the battery. (Just want to sense check this one).

 

[Craig07]

Yes, solid red.