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