Lithium charging too much?

[joebob25]

I tried asking this question in another thread but I think I got a little too wordy and probably confused the issue so I didn’t get any replies. I’m going to try again and hopefully be a little more succinct

I’m using a Renogy 30 amp DC-DC/MPPT charge controller to charge my SOK 206 AH Lifepo4. The “lithium” setting on the controller bulk charges fine, but when it hits the boost setting it seems to hold the battery at 14.6v indefinitely and stay in “boost”. The charging amps drop to zero/near zero, but the battery doesn’t ever drop down to the usual 13.8ish resting voltage. Is the a problem? It doesn’t seem that the controller is trying to cram more voltage into the battery, but I’m not used to seeing my battery sit at 14.6v all day either (coming from AGM batteries so still learning about lifepo4 charging) This happens when my camper is sitting outside in the sun while not being used. When I apply a load to the battery it rapidly drops to 13.7v or so and the charger returns to a bulk charging mode. Am I damaging my battery by letting it sit at 14.6v for an extended period of time? I can pull the fuse on the solar and stop the charging (which returns the battery to a normal resting voltage of 13.8v), but I don’t want to have to mess with this every time I let my camper sit idle in the sun for a few days.

In case you were going to suggest it, the “user” defined custom settings have the same effect even when I set them to stop “boosting” the battery after the recommended (per manufacturer) 15 minutes. Thanks for any advice!

 

[Vic Harder]

Have you got a link to the manual? I tried finding one online but struck out. And a model number?

You should not be using a BOOST setting of any kind. Even with the Victron gear I use, I set the "Float" voltage to lower than what the battery actually floats at. Can the boost voltage be set? Or disabled?

 

[TacomaAustin]

I'm in the process of installing this controller in a 2007 Bobcat and have yet to install the added battery monitor. So, I wish that I could be of more help.

In case you were going to suggest it, the “user” defined custom settings have the same effect even when I set them to stop “boosting” the battery after the recommended (per manufacturer) 15 minutes. Thanks for any advice!


As per page #12 of the user manual - have you set the "Battery Type" button, (located in the left hand interior of the unit between the terminals for the alternator and solar inputs), so that the battery indicator LED emits a way too bright sky blue color?

https://www.renogy.com/content/RBC3050D1S-G1/RBC3050D1S-Manual.pdf

If you glance at the battery charging parameter chart on top of page 22 of the user manual, it shows that once the boost stage is finished, there should not be voltage output from the controller when it is operating in the LiFePO4 setting. In other words, the chart does not show an "float" or "equalizer" voltage output for the lithium setting.

Last but not least - are you certain that the state of charge for the 205 AH SOK is at 100%? For safety reasons, LiiFePO4 batteries do not ship fully charged.

 

[joebob25]

https://www.renogy.c...0D1S-Manual.pdf

Here’s a link to the manual.

I have tried both using the factory lithium setting (yes indicated by a blue light on the unit) as well as trying to use my own settings via Bluetooth and the app. I see that on the factory lithium setting it has boost set to 14.4 (my charger seems to boost to 14.6) but the boost duration set to 0. I’ll have to wait until I get home tomorrow but I can attach screen shots of a charge cycle and what I am seeing on my app and battery shunt.

In short it bulk charges until it hits 14.6, changes to a “boost” setting, the charging amperage and volts drop to zero (it will show a tiny 0.1 amp charge occasionally during this time), and the battery sits at 14.6v in “boost” unless I intervene to lower the voltage by changing the settings on the app, or pull the fuse on the solar to stop the charging. I’m a little frustrated by Renogy, their customer service wasn’t much help. I’m a little short on space so this combo unit seemed like a slam dunk. I know Victron is the gold standard as far as quality but they didn’t have a combo DC-DC/mppt unit.

 

[joebob25]

I’m short I guess what I’m looking for is what a “normal” lithium charge profile should look like so I can find a suitable work around. Do most people bulk charge to their desired voltage and call it good? No “boost” no “float”? SOK has recommended settings for charging with a Renogy controller, but when I enter those settings in the app I get the same result where it gets stuck in a “boost” charge and the battery stays at 14.6v.

 

[TacomaAustin]

I’m a little short on space so this combo unit seemed like a slam dunk.

That was my reasoning upon purchasing the dual input DC-DC with MPPT - but the install ate up way more real estate than intended.

The image shows the install two weeks ago. I may attempt to update the image to show where the 100 AH battery is stowed and the extended shelf mounted to the cargo bed overhang.

 

[Vic Harder]

I’m short I guess what I’m looking for is what a “normal” lithium charge profile should look like so I can find a suitable work around. Do most people bulk charge to their desired voltage and call it good? No “boost” no “float”? SOK has recommended settings for charging with a Renogy controller, but when I enter those settings in the app I get the same result where it gets stuck in a “boost” charge and the battery stays at 14.6v.

Ideally, yes... bulk and then nothing. It getting "Stuck" at boost is a problem/bug. I would set the charging voltage to 14.4 and the boost voltage to just slightly below what your battery sits at when fully charged. I use 13.4 in my Victron setup for the "float" voltage. See if it still gets stuck doing the 14.6 boost stage.

 

[SkyP]

I have the same Renogy DC-DC charger.
The behavior of mine is exactly the same. My Battleborn Lithium battery sits at 14.6 if solar is charging.
FWIW I have a 45A (IIRC) Progressive Dynamics Lithium specific* AC powered charger in my travel trailer.
It too sits at 14.6 when the AC power is plugged in.

*I replaced the perfectly good regular Progressive Dynamics charger with the Lithium version.

 

[ckent323]

Of course the battery manufacturer instructions are preferred but in general here is some lithium ion battery charging info

BU-409: Charging Lithium-ion

https://batteryuniversity.com/article/bu-409-charging-lithium-ion#:~:text=Figure%201%3A%20Charge%20stages%20of%20lithium%2Dion&text=The%20advised%20charge%20rate%20of,C%2Drate%20with%20little%20stress.


Related:

BU-808: How to Prolong Lithium-based Batteries

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries


I hope this is useful.

Craig