Some very geeky lithium battery questions

[Unicorn Driver]

Hi,

I am setting my rig up for lithium and have some questions I need some help on :-)

1. Can I mix heated and unheated lithium?

2. Can I mix diffent sized lithium batteries in a bank or do they need to be the same size?

3. Is it OK to have a heated lithium battery on a outside battery tray in winter or best to have it in a insulated bay or inside heated rig?

4. Are there any advantages to having 2 different evenly sized battery banks on a physical switch?

5. If yes for number 4 is it better to do that for number 1 and 2?

6. Can I hook up a lithium battery to a rig with a msw inverter/non lithium converter, not hooked up to solar and power et al?

Thanks,

[Unicorn Driver]

Hi,

On app and cannot edit. For my question of hooking upmthe lithium battery is only so I can get 12 volt in the rig until I wait for new inverter/converter.

Thanks,

[nvs4602]

1. Can I mix heated and unheated lithium?
No, the heated batteries will discharge faster then non heated.


2. Can I mix diffent sized lithium batteries in a bank or do they need to be the same size?
No. All must be same capacity.


3. Is it OK to have a heated lithium battery on a outside battery tray in winter or best to have it in a insulated bay or inside heated rig

Best to keep them insulated or at constant temp. They will last longer.

4. Are there any advantages to having 2 different evenly sized battery banks on a physical switch?

Not sure what you mean. Better to keep one bank so batteries are aged equally.

5. If yes for number 4 is it better to do that for number 1 and 2?



6. Can I hook up a lithium battery to a rig with a msw inverter/non lithium converter, not hooked up to solar and power et al?

Yes. But they will not fully charge.

[vsheetz]

Question #1

Assuming talking about batteries with internal heating to mitigate the limitation of lithium can't be charged below freezing temperatures.

The heater typically is only active when charging (so no impact on discharge). So some charging current would be diverted to the heater. This unto itself is not a problem. But if needing operation at such temperatures the non heated batteries would go into low temp cutoff - or potentially be damaged if not having low temp cutoff feature. So I'm not understanding the usage senario of mixing such batteries.

Alternatively, mitigate the cold temperature operation via another method where the heaters of the heated batteries won't activate. Heated battery pads, provide heat to the battery area, move into conditioned area, etc

Question #2

Same

Question #3

Depends on the temperature. If below what the heaters will mitigate.

Question #4

Keeping separate typically adds unneeded complexity in implementation and usage. But can be useful if wanting to ensure battery availability if one bank inadvertently depleted. Or in the case of dissimilar battery banks.

Question #5

In the case of dissimilar battery banks.

Question #6

Considerations of using a charger not designed for lithium batteries:

1) voltages.

A multistage converter/charger designed for lead acid will typically have absorb and float stage voltages that are ok for lithium.

If a basic fixed voltage converter that outputs only 13.x volts, it likely will not fully charge lithium nor allow them to reach balancing voltage.

2) absorb time.

A lead acid charger typically expects the battery bank needing hours of time in absorb. Lithium does not. See what control you have over this.

3) Charge cycle compatibility.

A multistage charger not designed for lithium may not transition through the charge cycle correctly or restart the charge cycle correctly (I had a older xantrex inverter/charger. With lithium it would exit bulk early and move to floating).

##

So... you can try the charger you have, selecting, if selectable, a charge profile with closest appropriate voltages for absorb and float, adjusting absorb time as available, and give it a try. But have a backup plan should it not perform adequately.

This $35 gizmo has a feature that charts voltage over time. With it you can see the charge cycle working properly, or not.

Bluetooth Battery Monitor Auto... https://www.amazon.com/dp/B074ZCM6YC...p_mob_ap_share

[Unicorn Driver]

Thanks Vince,


All great answers, I really appreciate it.

I can fit 400AH in a bay which I can insulate, I will buy ones with heaters. I got to 100AH as they are they only size that will fit in the bay as need to go in sideways.

I have a Lithium charger trickwl charger at home so can charge the battery with that until the inverter/converter as my Lifeline need rescuing.

[twinboat]

Originally Posted by Unicorn Driver

Thanks Vince,


All great answers, I really appreciate it.

I can fit 400AH in a bay which I can insulate, I will buy ones with heaters. I got to 100AH as they are they only size that will fit in the bay as need to go in sideways.

I have a Lithium charger trickwl charger at home so can charge the battery with that until the inverter/converter as my Lifeline need rescuing.

It's an inverter/charger. It does not have a converter function in it. Converters can run without batteries, chargers can not.

You can split your battery bank with an A-B switch but your better off not.
Every discharge takes something out of a battery's life. The less the discharge, the less life is used. One large bank will have a lower discharge then a small one in the same situation, although with lithium 10,000 full cycles is a long long life.

As far as mixing different AH capacities, since all batteries are charged and discharged by volts, I don't see where it will mater.

Edit: Relion says yes, if within the first year.
Battleborn says no. Then goes on to mention in series.

Mixed answers from others.

[Unicorn Driver]

Thanks Twinboat :-)

[vsheetz]

Originally Posted by twinboat

As far as mixing different AH capacities, since all batteries are charged and discharged by volts, I don't see where it will mater.

I've seen various discussions and opinions on mixing battery capacities. But I've not seen a test - such as a 100ah and 200ah battery connected in parallel. Showing the 200ah battery flowing half the current of the 100ah battery, with them reaching zero SoC at pretty much the the same time. Have you seen such a test?

[Persistent]

You have asked questions about some very complicated questions. I can see from posts above there are different points of view for the questions. I am a little reluctant to add my point of view, since I am likely to miss subtle points as well. However, everyone is entitled to my opinion.

1. Can I mix heated and unheated lithium?

Obviously the answer is "yes". There will be no police to stop you.

Efficiency and compatibility are the actual question. Heated lithium will charge and discharge differently from unheated, but different designs are also different.

Assuming individual batteries have a BMS, each will manage itself, but efficiency will suffer. Life will also be affected differently.

2. Can I mix diffent sized lithium batteries in a bank or do they need to be the same size?

Again, assuming each battery has its own BMS, each will manage its own charge profile.

Depending on the design, different batteries will charge and discharge differently. Performance will suffer. Battery life will suffer.

3. Is it OK to have a heated lithium battery on a outside battery tray in winter or best to have it in a insulated bay or inside heated rig?

Heated Li batteries are necessary for charging in freezing temperatures. A good BMS will prevent charging when too cold.

Discharge also suffers from even lower temperatures. You will get better performance if batteries are located in a temperature controlled environment like the inside of an occupied RV.

On the other hand, taking an RV out of storage in extremely cold weather and running the furnace to heat the interior requires another power source. Li batteries must be at a certain temperature before they can power the furnace.

Battery heaters always require an outside power source to get started.

If you live and camp in AZ outside storage is fine. If you live and camp near the arctic circle other measures are required. On Mars, maintaining battery heat during winter shut down is mandatory. Heat failure means total failure.

4. Are there any advantages to having 2 different evenly sized battery banks on a physical switch?

I don't know of any that apply to most RV use. I am sure there are some is some conditions. Only the battery designers know for sure.

It usually depends on the BMS design. Batteries without a BMS must be the same chemistry when combined into a battery bank.

The bank must be charged using different profiles for different chemistries. Often discharge has similar issues.

5. If yes for number 4 is it better to do that for number 1 and 2?

Ask the battery manufacturers. Only they know how they have designed their battery systems. Customer help desk people probably do not know.

You probably have to compare charging and discharging specifications for different brands yourself.

6. Can I hook up a lithium battery to a rig with a msw inverter/non lithium converter, not hooked up to solar and power et al?

The inverter has no bearing. The charger side of an inverter/charger does matter.

It depends on the Li battery BMS. Battle Born brand usually work OK with some loss in performance.

Some older battery chargers are particularly bad for lithium charging. Battle Born maintains a list of tested models of chargers that work with their batteries. Ask the battery manufacturer.

[Pepperell]

And you'll need all interconnecting cables in your battery bank to be the same length. Cables of variable length will have different resistance, which can cause uneven charging.

[Winemaker2]

Here a great read re Li battys. He's a marine electrician but IMO boats & MHs have a lot in common.
https://marinehowto.com/drop-in-life...ated-consumer/

[Persistent]

Originally Posted by Winemaker2

Here a great read re Li battys. He's a marine electrician but IMO boats & MHs have a lot in common.
https://marinehowto.com/drop-in-life...ated-consumer/

I read this top to bottom. I have a lot of electrical and electronic background. I still learned a lot. It rearranges a lot of what I previously understood. I have given a lot of poor advice even in the last few days. I will try to find those posts and correct them.

If you read this article and you cannot understand it, you should not try to design your own LI battery system. First learn to understand and then follow the advice of one of the recommended battery suppliers. That supplier will not ship batteries to you until you work through your system design with them. Get with the manufacture and carefully work through the extensive issues.

Things I learned and am still processing:

Engine alternators of course fail due to overtemp trying to charge large LI banks. They also fail when the LI BMS automatically disconnects to protect the battery. Ok, I knew about high voltage from inductive devices (coils of wire). I did not mentally connect BMS behavior with with the coils of wire in an alternator. Disabled alternators result. Solid state electronics on the same circuit fry.

I did not understand the limitation of most drop in battery built-in BMS's. Even good designs cause serious problems with parallel and series battery banks. They are more sensitive to mismatch than lead acid batteries. All batteries must be same make, model, size, and carefully wired to balance the charge and discharge.

I did not understand how short the "absorption phase" of charging must be. 4 days or even 4 hours is too long. Some Li designs want 2 minutes. Do you know what your Li design requires?

Can you even get the relevant specifications from your battery manufacturer?

Don't try to use Li as an engine start battery, even if the drop-in says it can. Lots of technical issue need to be resolved first. Starting many built in generators can cause unexpected problems.

Disconnect your bridge circuit and use lead acid for engine start. Charge the two systems separately. Not all B2B chargers will protect your alternator and electronics in your chassis. Some configurations will cause your alternator to fail.

Large electric motors need special design considerations. Hydraulic jacks and slide working together may cause problems especially on smaller battery banks.

If you are designing a system for your all electric land yacht, you need a design review from the battery manufacturer before committing the money.

If you want to replace the 70 amp hour flooded cell on your trailer tongue with a Drop-In Li, buy a battery from a US manufacture. Skip Alixxxx and Ebay. Even Amazon sellers are suspect. Run your basic make and model 12 volt system by the manufactures customer service rep. Different designs have different requirements.

Generic advice I have been giving is not appropriate.:

[Persistent]

1. Can I mix heated and unheated lithium?

NO! Charge and discharge separately. Serious life issues with drop-in BMS capability.

2. Can I mix diffent sized lithium batteries in a bank or do they need to be the same size?

NO! Not without manufacturers specific instruction. Charge and discharge separately. Serious life issues with drop-in BMS capability.

3. Is it OK to have a heated lithium battery on a outside battery tray in winter or best to have it in a insulated bay or inside heated rig?

See manufactures specification. Most drop-in's must be protected from water, dirt, and corrosive stuff like salt water.

4. Are there any advantages to having 2 different evenly sized battery banks on a physical switch?

Yes if they are not identical. Charge and discharge separately for long life.

5. If yes for number 4 is it better to do that for number 1 and 2?

Yes. Charge and discharge separately for long life.

6. Can I hook up a lithium battery to a rig with a msw inverter/non lithium converter, not hooked up to solar and power et al?

Size of "in-rush" current matters. See battery and inverter manufacturer's specs.

Different drop-in batteries work differently with different converter/chargers. See battery manufacture for correct answer. The farther you get from the individual optimum charging profile, the worse battery life will be. Melt down failure is possible.

Sorry for the previous bad advice.

[Winemaker2]

Persistent
Great posts for those contemplating Li.
I know enough to be dangerous but recognized the quality of what RC put together. He is a great resource. Looks like you are way ahead of me & others.
I see lots of posts about folks considering the now low $$ drop ins and it seems like a problem waiting to happen.
I wish there was a way to put together a Li primer thread for those contemplating a conversion and make it a sticky in the appropriate section here on iRV2... is that something you would be willing / interested in tackling?