Charging lithium batteries from shore power?

[RobOfYork]

I'm looking at battery chargers and getting confused.

I want to be able to charge lithium batteries by plugging into shore power when it is available.

Any charger recommendations? Also I am confused on amp sizes. The more amps the better? How do you select the amp size of the charger?

[kazetsukai]

Originally Posted by RobOfYork

I'm looking at battery chargers and getting confused.

I want to be able to charge lithium batteries by plugging into shore power when it is available.

Any charger recommendations? Also I am confused on amp sizes. The more amps the better? How do you select the amp size of the charger?

Will Prowse over on YouTube ( https://www.youtube.com/user/errolprowse ) swears by this AIMS charger:
https://www.amazon.com/AIMS-Power-CO.../dp/B07N1K43NQ


More amps the better (faster charge), but your battery determines how fast you can charge- usually the manufacturer provides a "C-rate"for charge/discharge to let you know how fast you can charge.


I believe you can even parallel multiple of those AIMS chargers if need be to get even faster charging.

[Simplicity]

Are you using an inverter/charger combo or separate inverter and charger?

Per amperage, think of a water hose. Say a 1" hose puts out 10gal a minute, but a fire hose puts out 100gal a minute. Cool, but are you putting out a fire or filling up your kiddie pool.

Supercars are great, but for normal driving, it's overkill.

You get my point. Your batteries should be properly maintained (that I believe was part of your other thread). While Lithium is a special animal, in general, you are wanting to keep them pretty well charged. This means there "should not" be a reason to have a supercar charger.

That said, when connected to shore power, your charger will only use whatever is available after your AC appliances use up what they need.

So, if you have a 30a shore connection, but you're running a microwave, a/c unit and have a t.v. on, that all takes 20a, so you only have 10a left for your charger to charge your batteries.

Understanding what kind (AC / DC) of electrical loads you have, how much load each device draws, if they are drawing from shore or batteries (through an inverter) or directly (12v) from the batteries all are part of the equation to determine what size charger you need for your system.

Best of luck.

[RobOfYork]

Originally Posted by Simplicity

Are you using an inverter/charger combo or separate inverter and charger?

Trying to decide on that now. Trying to learn the benefits of combined and separate.

I think I grasp the amp sizing now. Thank you. I need one with enough amps to run everything with overhead to still charge when needed. Up to what the batteries will charge at.

My confusion was I noticed some chargers did not mention lithium. So I was guessing that I need a charger designed to charge lithium batteries.

[kazetsukai]

Originally Posted by RobOfYork

So I was guessing that I need a charger designed to charge lithium batteries.

Yes and no. There are lithium batteries that act like drop in replacements to AGM, these are designed with an internal BMS that allows for use with said chargers. Still, it is best if you can configure the charger's absorb/float settings for lithium chemistry.


Virtually any charger with configurable voltage settings can charge lithium, however there is a caveat. Lithium chemistries tend to be in the 2.8v-4.2v range, they are wired in series to achieve near-standardlead acid 12v/24v/48v voltage ranges. Batteries wired in series do not self equalize- and thus individual cells in a lithium battery can drift apart. A BMS is required to be able to disconnect the battery from loads in case any cell gets beneath it's rated voltage, or chargers in case any cell is in danger of being over charged.


DIY lithium batteries are much cheaper than drop in replacements however you will be the one wiring in the BMS. Drop ins come with an internal BMS that does this job.

[Simplicity]

Originally Posted by kazetsukai

Yes and no. There are lithium batteries that act like drop in replacements to AGM, these are designed with an internal BMS that allows for use with said chargers. Still, it is best if you can configure the charger's absorb/float settings for lithium chemistry.


Virtually any charger with configurable voltage settings can charge lithium, however there is a caveat. Lithium chemistries tend to be in the 2.8v-4.2v range, they are wired in series to achieve near-standard lead acid 12v/24v/48v voltage ranges. Batteries wired in series do not self equalize- and thus individual cells in a lithium battery can drift apart. A BMS is required to be able to disconnect the battery from loads in case any cell gets beneath it's rated voltage, or chargers in case any cell is in danger of being over charged.


DIY lithium batteries are much cheaper than drop in replacements however you will be the one wiring in the BMS. Drop ins come with an internal BMS that does this job.

Good education moment there Kaz. Thanks!

To be clear, does the BMS disconnect the entire battery from loads if even one cell falls below its rated voltage?

I'm assuming if each cell is 3-4v, then you have 3 to 4 cells in series (~12v) and those series banks are in parallel to build up the amp hours?

So, why doesn't the BMS just take the one bad bank out versus the whole battery? Be nice if it did that and then texted you. Ha!

[kazetsukai]

Originally Posted by Simplicity

To be clear, does the BMS disconnect the entire battery from loads if even one cell falls below its rated voltage?

A good BMS does this, or at least has a mechanism to do so. This is to protect every individual cell in the pack.

The idea is that you shouldn't deplete the battery to the point of damage, the cutoff voltage is around the area damage or an otherwise unsafe condition is likely to start occurring. Same with charging. If the charger doesn't stop in time something else has to, or you may get a fire.

Originally Posted by Simplicity

I'm assuming if each cell is 3-4v, then you have 3 to 4 cells in series (~12v) and those series banks are in parallel to build up the amp hours?

NO- best practice mandates you wire cells in parallel FIRST and then wire those cell groups in series. This is why I don't like drop in replacement lithium (like battle born), those batteries are internally wired in series, but you see a bunch of people out there running 2 or 4 of them in parallel. In no other context is this considered acceptable- if you do series then parallel with a DIY pack you will have people on the solar forums hounding you about it.

Parallel first is why I'm abandoning Tesla packs (which are internally wired in series) for LiFePo4. You can series connect packs safely, but parallelizing them at any scale will cause longevity issues and introduces some pretty nasty catastrophic failure scenarios.

My new bank is wired 3P16S. 3 cells wired in a Parallel group, 16 groups in Series. 48V (51.2V Nominal). If I want more capacity I bump all 16 groups to 4 cells or more.

Originally Posted by Simplicity

So, why doesn't the BMS just take the one bad bank out versus the whole battery? Be nice if it did that and then texted you. Ha!

Because its a failure condition that can damage the battery or worse cause a fire.

When recharged from low-voltage cutoff, the BMS will once again allow loads. When the highest cell is discharged below maximum voltage, the BMS will allow the pack to charge. The BMS keeps the pack in a safe voltage range for long term operation.