Another lithium battery question.

[Soundsailor]

Charging batteries, especially lithium, can actually be very complicated. Unfortunately, the consumer doesn’t generally get to know the different charging algorithms set by the manufacturer.

While voltage is one factor determining charge rate, current is just as important. Yes, a charger designed for LiFePo4 batteries has a higher voltage output - somewhere around 14.6 volts. Today’s “smart chargers” (CCCV) are able to switch from constant current (CC) to constant voltage (CV) as the battery approaches 100% SOC.

When your non-lithium Charger reaches max voltage - short of the LiFePo4 100% SOC, the secondary Charger should sense that current is still flowing into the battery and continue to charge bringing it up to 100% SOC.

Using a secondary charger may very well result in your non-lithium converter/charger never going into bulk mode - the full load being shouldered by the secondary charger.

IMO, you should not use the secondary charger full time, but rather use it to bring the battery up to 100% SOC when needed, then turn it off.

Some good points here. Thanks for your response @Jomani.

If I could share my setup, it might offer some info for the OP.

Lithium-aware converter/charger
50 Amp solar controller in lithium mode
20 Amp lithium aware charger
800 Ah lithium battery bank in 4 200 Ah batteries connected by bus bars

Since the converter/charger I have is one of the WFCO auto-detect models that is not very reliable, I sometimes use the standalone 20 Amp charger to supplement the charging when the battery bank is depleted. But it is always off once the batteries are charged. My experience is that the batteries will accept charging from whatever source is connected. It's true that the converter/charger can get confused when it is not the only charging source. But that won't damage them or stop the charging, it might just be at a different rate.

To the OP's question, yes, you can connect both the trailer's converter/charger and a stand-alone charger at the same time, I've been doing it for some time and it works. And yes, the stand-alone charger would charge your lithium battery fully, even if the stock charger/converter has stopped when it reaches its limit.

[robmcqueen]

Some good points here. Thanks for your response @Jomani.

If I could share my setup, it might offer some info for the OP.

Lithium-aware converter/charger
50 Amp solar controller in lithium mode
20 Amp lithium aware charger
800 Ah lithium battery bank in 4 200 Ah batteries connected by bus bars

Since the converter/charger I have is one of the WFCO auto-detect models that is not very reliable, I sometimes use the standalone 20 Amp charger to supplement the charging when the battery bank is depleted. But it is always off once the batteries are charged. My experience is that the batteries will accept charging from whatever source is connected. It's true that the converter/charger can get confused when it is not the only charging source. But that won't damage them or stop the charging, it might just be at a different rate.

To the OP's question, yes, you can connect both the trailer's converter/charger and a stand-alone charger at the same time, I've been doing it for some time and it works. And yes, the stand-alone charger would charge your lithium battery fully, even if the stock charger/converter has stopped when it reaches its limit.

Thanks for that info.

[ajg617]

I'm not sure about that. I think both look at battery voltage and operate according to their own programming. If the converter/charger doesn't top off the LiFePO4 batteries, I think the solar system will - if it has a LiFePO4 setting on the controller.

Again, others with more knowledge please weigh in. Is Najataagihe correct?

My solar continues to charge while on shore power while the lithium only Progressive Dynamics charger does as well. As @Jomani mentioned, I have had the issue where the PD would not go back into bulk mode (nearly two weeks on the road) - that's described in their documentation.

[Jomani]

Thanks for explaining that to me. Just watched your YouTube videos they are great very well done. I see your using a transfer switch and a inverter. Is there a reason you do not use a inverter with a built in transfer switch ?

Nothing more than personal preference. I have always preferred separate components to all in one units. You can’t go wrong with something like a Victron Multiplus - they have a proven track record, but at a premium cost. I just like knowing that I can replace individual components if/when they fail.

[TorrieNY]

I have a 2021 Transcend Xplor 231rk. I have a dead lead acid battery and while getting ready for the new season, I want to switch to lithium… Will I have to redo chargers and converters as well?? I have been doing research but they make it sound so simple - like just getting a new battery and plugging it in. Ugh… So that’s not so?? Plus our rig came with solar panels - does that matter?
TorrieNY

[Soundsailor]

I have a 2021 Transcend Xplor 231rk. I have a dead lead acid battery and while getting ready for the new season, I want to switch to lithium… Will I have to redo chargers and converters as well?? I have been doing research but they make it sound so simple - like just getting a new battery and plugging it in. Ugh… So that’s not so?? Plus our rig came with solar panels - does that matter?
TorrieNY

Yes, most lithium batteries can simply be put in instead of lead acid. You won't need to vent them. And yes, your solar should be able to charge the lithium batteries, you'll need to reset the controller to lithium mode.