Lithium Bat HELP PLS

RCB

Hello,
Problem: Lithium batts discharging (rapidly) and am in a campsite with no power.
2 new Eco-Worthy installed a few days ago.
Existing charger seemed to charge a at 13.8 the solar showing charging at 14.2 to top up. victron MPPT 75/15 settings changed 

Presently voltage showing 13.3 after a days drive when they should be about 13.8. Plugged in at previous campsite last night.
There is no amperage from the tow vehicle. If a blown fuse in the tv then assume no current could flow into the tv.
Not sure what to check. All 12 v systems working and off except small 12 v fridge and carbon monoxide detector.
Any help appreciated.
RCB

DaveAnna

Sounds like the camper is leaking to you vehicle. Unplug your tv and see if it stops discharging. If you have a shunt installed, you should see current flow, if not, maybe bad battery(ies)

rfuss928

It actually sounds like your batteries are doing okay.  Your voltage level expectations seem quite high.

My experience when using lead-acid chargers with LiFePo4 batteries is they provide very low current due to the very low voltage (13.6-13.8v) and therefore very slow charging.  They may eventually reach 85% but it will take days to add any meaningful capacity.  Your TV will not be able to provide any charge to the Li batteries due to lower system voltage with long wiring and as DaveAnna suggested may even draw down the trailer batteries. 
Your voltages indicate the solar is keeping you in the 70-90% SOC.  
Happy camping!

AnOldUR

Like @DaveAnna mentiones, your tow vehicle may not provide the correct charging profile and the wiring may be very slow to charge. Given enough time and good sun, your solar should top off lithium if configured properly.

I did not trust my alternator and wire size to provide the proper charging profile and rate. Rather than invest in a DC-DC charger and rewire, I disconnected all charging from the tow vehicle and have had no problem relying on solar to keep our LiFePO4's topped off. It also isolates the lead acid tow vehicle battery from the T@B's lithium.

RCB

AnOldUR. Thanks for the comments. What / how did you disconnect the charging from the tv ? 

I’ve turned the batt switch off and connected the tv and engine running and could not power any lights etc in the rv.

pthomas745

You can run yourself in loops with trying to charge from a tow vehicle.  Of all the ways to charge a battery, it can be the slowest possible way to charge a battery.

With the Victron devices, it is very easy to see if any charging is going on between the tow vehicle and the battery.  When you were driving, did the devices show any charging going to the battery at all?  Many tow vehicles simply do not charge any type of battery, and if they do, they are not really equipped to "completely charge" a lithium battery.  So: your Victron will show you if any charging is taking place.

If you look at the "Lithium State of Charge" chart posted by rfuss928, the voltage for a lithium battery is virtually identical for a lithium battery between 14.4 (which is close to the "charging voltage") and 13.4, which, in many cases, is the "resting voltage". 

Your solar setup is a much better charging device than your tow vehicle.

AnOldUR

RCB said:

AnOldUR. Thanks for the comments. What / how did you disconnect the charging from the tv ?

To isolate the trailer battery from the tow vehicle I disconnected the charge wire in the junction box behind the tub. 

RCB said:

I’ve turned the batt switch off and connected the tv and engine running and could not power any lights etc in the rv.

With the charge wire disconnected in our system, if the battery switch is off, the interior lights (or any 12V accessories) will not work even if connected to the tow vehicle. Without our mod being done, power from the tow vehicle's battery would be sent to the converter regardless of the battery switch being on of off. Newer vehicles have isolation relays, but with your trailers 7-pin connected, the engine running and the battery switch off, I believe you should still have 12V going to your trailers interior lights through the charge wire. Hopefully someone with more experience can determine why you're not getting power to your charge wire. As you said, it could be something as simple as a fuse.


The TRAILER PIGTAIL goes to pin #4, Aux 12v + Charging

Reminder, your breakaway brakes will not work with the battery switch off. Always leave the switch on while towing. 

Horigan

RCB said:

AnOldUR. Thanks for the comments. What / how did you disconnect the charging from the tv ? 

I’ve turned the batt switch off and connected the tv and engine running and could not power any lights etc in the rv.

Another option is to pull the fuse that may be on your TV firewall. When my brake controller was installed they put a fuse there for the charging wire. 

AnOldUR

Horigan said:
Another option is to pull the fuse that may be on your TV firewall.  

Damn! Where were you when I was crawling under the T@B to remove charge connection?