Lithium batteries LiFePo4 with WFCO 8735 AD charges approx. 5.5A

californication

Hi,

2 weeks ago I switched an acid battery to LiFePo4: 2x100Ah LiTime with smart monitoring.

When I initially connected them, the WFCO showed "green light" which meant it still kept an acid profile. I discharged batteries close to 3% (based on smart monitoring) and I started it charging. The WFCO detected batteries as LiFePo4 and switched LED to "blue", which means it should start using a lithium profile.

Initially, batteries were charged close to 30A, but overtime the charge went down to 8A and slowly down to 6A. It ended up on 5.5A. I called WFCO Support, but they never picked up the phone. I left a voice message, but no one called me back.

Today, after I noticed my batteries went down to approx. 13%, I plugged in a cord to the Tab. It started charging batteries. My smart monitoring showed that WFCO is delivering approx. 5.5A (only blue LED is on, no red LED which would meant "fast charging").

It means it's delivering about 180W, even though batteries are capable to get more.

Am I missing something here?

Thanks.

pthomas745

The charging rate of a battery with any sort of charger is related to the charging needed by the battery, not the total amp rating of a charger.  At the start of battery charging, depending on the state of charge of the battery, the charger will be in "bulk" charging mode, which could be the highest amp rate into the battery.  As the battery continues to charge, the charge rate drops to "absorption" and then moves to "float".  (This is a generic description!)  A battery just cannot handle being crammed with 30 amps through out the entire charging cycle. 

This is a Battleborn page that describes the basics.....there are more parameters here, since lithium batteries have their own built in battery management systems.  LiTime may have a generic description on what their bulk and absorption modes are, also.

https://battlebornbatteries.com/charging-battleborn-lifepo4-batteries/

californication

Hi pthomas745,

Thanks for the link. The batteries I got are: 12V 100Ah group24 bluetooth deep cycle by LiTime. Based on the manual the charge voltage should be 14.4V +- 0.2V wlfh a recommended charge current 20A. I've never seen these values with WFCO.

Currently, it would take about 16-18h to charge batteries full, with an shore power supply.

rfuss928

The discussion I had with a technician at WFCO indicated the long wiring to the tongue box on the 320 T@Bs causes problems with the AD function and charger performance because of the resulting voltage drop.  The converter senses a higher voltage than the actual battery voltage and adjusts the charge current based on the higher detected voltage.
After trying an install in the front box, I moved my LiFePo batteries to an interior bench and the much shorter wiring to the converter made the WFCO perform as expected or better.

https://tab-rv.vanillacommunity.com/discussion/18199/ultimate-toys-cs-s-lifepo4-upgrade#latest

californication

Thanks for the link rfuss928
I wanted to do an easy replacement. However, if further changes are required, I'm gonna reconsider doing them.

rfuss928

I just wanted to simply replace the aged AGMs we used our first season with the UT.  When I moved the LiPo batteries to the interior, the recovered space in the front box was a significant bonus I hadn't anticipated.  Very satisfied with the results.

californication

My lithium batteries installation was dictated by similar idea. I was tired of acid battery 75Ah dying in 24h so I went with 2x 100Ah (immediate gain of 6x more power!)

I'm bummed that Tab is not prepared for such an easy swap.

Sharon_is_SAM

@rfuss928 - was there any change to the operation of the break away brakes when you moved/rewired the batteries and cut off switch close to the converter?  Any change at the front junction box?

rfuss928

Sharon_is_SAM said:

@rfuss928 - was there any change to the operation of the break away brakes when you moved/rewired the batteries and cut off switch close to the converter?  Any change at the front junction box?

All the original wiring to the Junction box and front box remained in place.  The break away switch is still powered by the batteries if the disconnect switch is "ON".

californication

I'm currently on a day 5 of recharging my batteries. It takes too long... so @rfuss928 it sounds like I'm gonna be following your steps soon

californication

I spent last 2.5 days working on the relocation of my batteries: Tab 2022 320s

Saturday

First thing first. I spent couple hours trying to trace most of the wires. It took me a while, because I had to relocate air ducts from the AC. They were just placed on the floor.
I decided to move 2x group 24 batteries to the AC compartment. The compartment with WFCO doesn't have enough space, with wires on the floor. The one with ALDE is crowded with water pipes, etc. The other, passenger site, I wasn't feeling comfortable due to heater and higher temperatures.

I started with repurposing existing wiring. I noticed that the tub in front had 2 set of red+white wires. One set is from Victron MPPT 75/10 (the one bypassing the main switch), another set is to batteries. The red wire was connected to WAGO 221 connector, and it ended up in the WFCO. The white wire goes to the ground bar.

I purchased Victron MPPT 75/15 and Victron Orion-TR 12/12 30A.

The idea being: solar panels are already wired to the Tab, they connect to the existing MPPT 75/10. I can take red+white wires which go to the tub, and reuse them for an external solar panel.

Orion-TR is for DC/DC charging. I noticed the hard way, that existing 7-pin wiring doesn't provide enough power to batteries to move the needle. So I could use another set of wires, connect them to 7-pin and charge batteries while driving.

I also moved batteries next to the AC.

It took me most of Saturday to figure that out.

Sunday

It took me at least 4 trips to a hardware store to buy all wires, connectors, clamps I went with 10AWG which is rated 30A

Now, going back and forth with multimeter. Checking which wires were really the ones I was interested in.

Wiring "batt" from 75/10 and 75/15 was (almost) an easy task. I had to drill a hole big enough to trace wires between WFCO and AC compartments. Then I added battery line going from battery to the WFCO. It was another couple hours of just playing with wires, clamps, connectors.

I was still missing the main switch.

Monday

Today, I decided to wrap it up (we're leaving Friday to Death Valley). I started by adding the main switch.

I was about to call it a day! but then I started wondering what about the emergency brakes. Indeed... they weren't wired, so they weren't working.

That was the sign, I had to go down on my knees (and my back) to read 7-pin box, and verify connections.

I noticed that original battery wires were going down to the same 7-pin box, and the 7-pin box is used as a main point of entry to the Tab.

It is good, but also it is bad. Good, because everything is already wired. Bad, because there is no isolation between TV (tow vehicle) battery ground and RV battery ground.

After going back and forth between inside and outside, I finally knew. The original red wire, which was connected to the WFCO unit, could be used for powering brakes. So, I replaced original WAGO 221 2-pin to 3-pin and connected: battery wire, WFCO wire and "brakes" wire altogether. Thanks to that, my brakes are working only when the main switch is ON.

2.5 days later and I'm in the same place that when I started... OK, not really.

First, I checked how fast I can charge batteries. Granted, they were 98-99%, I still got about 180W.

Second, my front tub is... EMPTY! I immediately gained all the space for blocks, wires, pipes, etc. All my clutter, we had to tow inside of the Tab, is moved out.

Third, when I was playing with batteries, I noticed that the space under bed incliners is empty... so I started looking around for bed hinges, that I could install instead of existing ones. We don't use incliners, so I could remove hinges, and I could make another storage room.

Future plans

1. I'm gonna need to revisit 10AWG vs. 8AWG story. Based on my readings, I'm safe.

2. Install of Orion-TR. I'm still planning to add it, to improve the way how we charge batteries.

3. MPPT 75/15 is unused at this moment. I'm playing with two ideas:

- add SAE either inside of the tab and reuse existing wiring for ORION

- or move the SAE outside to the tub, and use red-wire from 7-pin

This is the place where non-isolated white-wire (ground) could be improved.

But that's the story for another time.

rfuss928

californication
This is all sounding very familiar.  You seem to have a good handle on the details.
You will need to disconnect the 7-pin pigtail +12v lead from the terminal block in the junction box to avoid the higher LiFePO4 battery voltage from pushing charge current to the TVs lower lead acid battery system.  The T@B's LiFePO4 "+12v" and e-brake wiring can remain in place as you described.  This is where I used one of the abandoned solar wires to connect the 7-pin +12v to the Orion DC-DC I located near the solar controllers.  The 10awg wiring everywhere in that path significantly limits the current and voltage available to the DC-DC.  To maximize performance, heavier gage wiring from the TV battery to the DC-DC is needed.  I managed to set voltage limits with the Orion's tools to get satisfactory charging with the wiring described. 
IMO - The isolation provided by the Orion DC-DC is necessary to protect the TV's electrical system from the higher system voltage of the T@B's LiFePO4 batteries. 

californication

Oh, that's an important info! I didn't think about that, thank you @rfuss928.

In the past I added a switch to my TV, which I need to flip ON to send the power back through 7-pin. For incoming trip, I'm just gonna keep it OFF so no further rewiring would be required before the trip.

Few questions for the future:

If I recall correctly my Tab uses 10AWG for solar wires. However there are red/white 8AWG wires, which go to the junction box under the frame (the very same one which connects RV <=> TV 7-pin). I was thinking about using them for pulling 7-pin +12V to Orion-TR. This would leave me with solar wires, which could be used to "send back" e-brake +12V. I don't believe I'm able to pull extra wires due to limited space under the wet bath. It's very tight there.

@rfuss928, in your install I noticed you have SAE plug inside of the front tub. Do you recall how many wires you repurposed? Which ones were reused? Did you add any new ones?

rfuss928

californication said:

@rfuss928, in your install I noticed you have SAE plug inside of the front tub. Do you recall how many wires you repurposed? Which ones were reused? Did you add any new ones?

I left the 8awg pair in the tub and connected them to a terminal block.  This is where the SAE plug is connected and also a light for the tub.
The red 10awg solar wire went from the 7-pin +12v to the DC-DC.  The white solar wire remains unused.  No new wires.