Lithium battery parallel with old lead acid

Buzz Lightbulb · Guru

Lithium battery parallel with old lead acid

Whenarewethere · Guru

Do you need to save weight? That would be the first question I would ask myself.

Lithium & lead have different charging profiles.

Tony Bev · Guru

I am not a techie, but my research told me

(As Whenarewethere has already said) lead acid, and lithium batteries, have different charging profiles

Below snip is from an American reputable (to me) website

For battery safety, we do not recommend combining different types of lithium batteries and lead-acid batteries.
This is because the load characteristics and capabilities of these batteries are drastically different which can lead to safety issues.
Due to this, do not directly combine these batteries in parallel or series.

Link to website

https://battlebornbatteries.com/battery-isolator-with-lithium-lead-acid/#:~:text=For%20battery%20safety%2C%20we%20do,can%20lead%20to%20safety%20issues.

Peter_n_Margaret · Guru

I know of no reason why a LA and a Li battery should not be used in parallel, provided they are charged according to the lithium requirements (not too high voltage).
Cheers,
Peter

Whenarewethere · Guru

Worth a read:

https://community.victronenergy.com/questions/19981/mixing-lead-acid-and-lithium.html

Buzz Lightbulb · Guru

Thanks for the information. I'll read up on it soon.

I don't need to reduce weight. I just thought it would be an opportunity to switch to a better option.

Peter_n_Margaret · Guru

If you don't need the weight saving and you don't have very high amperage draws to supply, staying with AGMs will still likely be the best option.
Cheers,
Peter

Whenarewethere · Guru

If it basically works as is leave it alone. Depending on your AHs maybe up the size a touch or double your solar capacity. This will probably be of more value.

Dicko1 · Senior Member

If you compare available amp hours per dollar lithium is very close to agm prices...Full River 120 a/h $440 + delivery...ITech 120 a/h $780 + delivery. The lithium is cheaper, lighter, charges quicker, higher amp output and longer lasting.

I have yet to see any battery manufacturer advise that mixing of battery types is recommended..actually..its quite the opposite.

Jaahn · Guru

Hi Buzz :)
I have a lithium battery that i have had for quite some years. I often connect it in parallel with my lead acid AGM to charge it with the solar, but it is under my manual observation and i remove it when charged or soon there after.
I would not leave it connected permanently together with the AGM as it was too bloody expensive to charge in a manner that is not recommended by the supplier ! Seems a no-brainer to me but you could have different ideas. :(
Good luck Jaahn

dabbler · Guru

https://www.evakool.com.au/EVAPOWER-KIT-WITH-BATT-BOX-WIRING-HARNESS-VSR-WATT-METER?location=401&quantity=1 Buy one of these while it's still on special, plonk your AGM inside and use it as an extra camp battery. Replace van battery with Lithium along with any necessary charging bits. The Lithium alone will easily meet you power requirements. Much simpler, much safer.

dabbler · Guru

https://www.evakool.com.au/EVAPOWER-KIT-WITH-BATT-BOX-WIRING-HARNESS-VSR-WATT-METER?location=401&quantity=1

Peter_n_Margaret · Guru

Dicko1 wrote:
If you compare available amp hours per dollar lithium is very close to agm prices...Full River 120 a/h $440 + delivery...ITech 120 a/h $780 + delivery. The lithium is cheaper, lighter, charges quicker, higher amp output and longer lasting.

Your maths is clearly different to mine.

Unless you are drawing very high currents (and many can not, due to BMS limitations), 100Ah of AGM has no less usable energy stored than 100Ah of Lithium.

And I have never paid anything like $440 for 120Ah of AGMs. Battery Value home page

Cheers,

Peter

Dicko1 · Senior Member

Peter_n_Margaret wrote:
Dicko1 wrote:
If you compare available amp hours per dollar lithium is very close to agm prices...Full River 120 a/h $440 + delivery...ITech 120 a/h $780 + delivery. The lithium is cheaper, lighter, charges quicker, higher amp output and longer lasting.

Your maths is clearly different to mine.
Unless you are drawing very high currents (and many can not, due to BMS limitations), 100Ah of AGM has no less usable energy stored than 100Ah of Lithium.
And I have never paid anything like $440 for 120Ah of AGMs. Battery Value home page
Cheers,
Peter

Yes..my maths are based on a quality, proven long life battery. After many years of working in remote areas I have learnt that quality is paramount for a reliable system. The Fullriver is a known top quality battery. I,ve had a few sets and have gotten 8 years from them. My last set I sold that were 5 years old and in nearly 90+% original specs. I went lithium to save weight. I know of heaps of people on various forums who have bought cheap "over spec" agm batteries for around $200 and found that they are no where near the advertised a/h. There are also cheap lithium batteries out there for around $500 for 100a/h...crap batteries that wont last. AGM and lithium may well be 100a/h each of stored energy....but at 12.0 volts your agm is at 50% used. My lithiums supply 12.6+ till about 80% used. Vast majority of quality lithiums allow high current draw as well. After having had battery banks for camping and work for several decades the switch to lithium was a no brainer.

-- Edited by Dicko1 on Thursday 3rd of June 2021 06:22:09 AM

-- Edited by Dicko1 on Thursday 3rd of June 2021 08:08:11 AM

John Kay · Veteran Member

You should not mix different chemistry batteries. They have different charging parameters.

Peter_n_Margaret · Guru

John Kay wrote:
You should not mix different chemistry batteries. They have different charging parameters.

Both LA and Lithium will charge (and float) well at 14.3 to 14.4V. This also happens to be the typical voltage of traditional alternators.

Cheers,

Peter

Dicko1 · Senior Member

Peter_n_Margaret wrote:
John Kay wrote:
You should not mix different chemistry batteries. They have different charging parameters.
Both LA and Lithium will charge (and float) well at 14.3 to 14.4V. This also happens to be the typical voltage of traditional alternators.
Cheers,
Peter

This is from the OPTIMA battery site. They probably know a bit more about batteries than most on here...

We would strongly discourage anyone from connecting batteries in series or parallel applications, if the batteries are not identical in age, size and type. It sounds like your batteries are different in each of those ways. Different brands of batteries can have different charging and discharging characteristics, with some accepting a charge or delivering current faster than others. That can be true even if the batteries are the same size. Different types of batteries (flooded or AGM) also can have different charge/discharge characteristics. When you connect two or more batteries that don't charge and discharge at the same rate, one battery will probably end up overcharged and/or one battery will end up undercharged. Neither is a scenario you want to have happen to your batteries, as it will probably shorten the lifespan of both and could create a potentially create a dangerous situation, if one battery gets severely overcharged.

The same is also true of batteries that are identical in every way, except that one battery is older than the other. As batteries age (or get used), their charge/discharge profile changes. As such, they essentially charge and discharge at a different rate a year later, than they did when they were brand-new. That means you shouldn't connect batteries together that aren't the same age or haven't been used in the same application since they were new, even if they are the exact same make and model.

Unfortunately, that means when one battery in a bank of two or more batteries needs to be replaced, they should all be replaced at the same time. That doesn't mean the other functioning batteries should be discarded entirely, but they should not be used in an application that has batteries that differ in age, size or type. For some marine and RV applications that use a lot of batteries, it may make sense to isolate a larger bank of nine batteries into three smaller banks of three batteries, instead of connecting them all together. That way, if one battery goes bad, far fewer batteries need to be replaced.

PeterD · Guru

QED

VK2FJW · Veteran Member

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And they are dinky dye Aussies!

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