max. amount of Lithium batt. in parallel

[goboatingnow]

I’ve done quite a bit of work in the LiFePO4 field but not on boats. But the issues are the same

My own view is that protection both HVC and LVC is needed on a cell level no matter what configuration of cells is deployed , i agree that 4 in Parallel is a practical limit but I have seen successful installs with larger parallel configurations. I don’t think there’s a hard and fast rule.

The big issue is lithium’s on a boat is a complete system level rethink and I get worried about “ drop in “ solutions.

[Philtao]

Originally Posted by The Sun King

The thing I don't like about lithium is that when the BMS turns off, you go dark. No more squeezing out a few more hours by dropping below the lead acid's 50% level. Hence, my redundancy plan.

It depends on the BMS! Some of them allow to set multiple thresholds (cell voltage, cell temperature, SOC) with visual and audible warning PLUS time delayed control of up to six outputs. Like that a first level of warning can cut non-critical loads (keeping vital equipment operational: pilot, instruments, navigation lights, plotter, bilge pumps...), and a second level can isolate the battery.
Another point to be careful about is what happens if the BMS has a heart attack? will it shut down the power? some BMS give you the option...
See the thread https://www.cruisersforum.com/forums...o4-251905.html

[Stu Jackson]

Originally Posted by henryk

......................

Electrical and electronics are not my forte , so i would like to make it as simple as possible. .......................
.....................................

Henry,


I'm going out on a limb here, but I would venture to state definitively that not one single one of the qualified respondents on this thread was born an electrician. They all studied hard and learned.


Most us can agree that KISS is always a good thing to do. Lack of simplicity leads to complications and unforeseen consequences.



In some cases, folks just aren't into certain subjects. Like artists tend not to be good plumbers...with exceptions of course!


But, please, look at it this way: what many are suggesting has to do with YOUR SAFETY. The more you know of the How and Why things work the safer you will be.


I recommend you learn to find and use trusted sources. marinehowto is one of them. As you spend more time on this and other boating and battery forums and blogs and websites, you will soon begin to learn who you can trust and who's blowing smoke, sometimes literally.


Often folks whose writing makes you wonder what they're smoking would be less trusted than those who can put a complete sentence together and who can and will point you to authoritative references sources.


I encourage you to learn as much as you can. You learned how to sail and run a boat. Lotsa people think just doing that is impossible.


None of was born an electrician. We all learned, You can and should, too.


Good luck, you can do it.

[hzcruiser]

Originally Posted by more

2P4S,3P4S ,4P4S,100P4S this is only path for small user and medium company go. also forget 1C charging minimum 2C better 3-5C CC charge.
[...]

Again a very bold and strong statement from you and, sorry, but again I can't agree with you nor verify where you get this information from ?

2-5C of charging current?

I've never seen that as a recommendation by anyone, it's more like 0.5 to max 1C:
https://www.powerstream.com/LLLF.htm
https://en.wikipedia.org/wiki/Lithiu...sphate_battery
https://www.power-sonic.com/blog/how...ld%20be%200.5A.

and many more. Where are your sources?

[hzcruiser]

Originally Posted by The Sun King

Batteries in any chemistry are best not run in parallel. In large systems, the fewer the parallels the better. [...]

I'd say that's oversimplifying things a bit. Different solutions often have different pro and cons. Just going up with voltage means you need to step it down again for the many 12V consumers on board plus you need a charger with a high output voltage. Also, above 30V DC becomes more and more dangerous to handle compared to lower voltages or similar AC voltages.

Charging a large 12v bank of any chemistry is likely to upset an ordinary alternator. You'll need one that can limit current or it will overheat.

Now why is that? An alternator puts out a fixed voltage and then all the current it can produce, if the batts can absorb it. "Ordinary alternators" are just not built for the continuous high load or duty cycle that a large bank would require, that's all.
Hence the alternator throttles down very soon once the rectifier or armature is getting too hot. If it doesn't throttle back, it'll kill itself, yes.

The thing I don't like about lithium is that when the BMS turns off, you go dark. No more squeezing out a few more hours by dropping below the lead acid's 50% level. Hence, my redundancy plan.

So at the top you're saying parallel is not good, yet you're planning for a redundant batt bank which would effectively run _in parallel_ with the main bank?

Either way, that's what I've been proposing and implemented, too. More than one battery (with latching relays to disconnect them if needed) feeding the bus but located in different spots. Yes, they'll see slightly different charging voltages and the discharge rate will also be different, depending which consumer is drawing how much power, but that's not going reduce the lifetime or number of charge cycles of the LFP. (With FLAs that would be a different story)

[Philip Hoag]

First you need to get lithium iron phosphate batteries and NOT lithium batteries. Lithium iron phosphate batteries are far superior to "lithium" batteries in terms of safety.

Second, you need to make sure you have a Victron Energy Orion-Tr Smart 12/12-Volt 30 amp 360-Watt DC-DC Charger in between the alternator and the lithium iron phosphate batteries. The lithium iron phosphate batteries charge so fast that you will typically burn our the alternator in three days time. It happened to a friend of mine who hooked his alternator direct to the lithium iron phosphate batteries.

Third, in regard to the "higher resistance" issue with multiple lithium iron phosphate batteries "parallel" you need to make sure the "battery cables" going to to each of the multiple batteries are of "exactly equal" length!

[Philip Hoag]

My drawing does not show cables of equal length.
See attached drawing I just did.

[CruiseN]

Originally Posted by Stu Jackson

Henry,





Most us can agree that KISS is always a good thing to do. Lack of simplicity leads to complications and unforeseen consequences.






But, please, look at it this way: what many are suggesting has to do with YOUR SAFETY. The more you know of the How and Why things work the safer you will be.


I recommend you learn to find and use trusted sources. marinehowto is one of them. As you spend more time on this and other boating and battery forums and blogs and websites, you will soon begin to learn who you can trust and who's blowing smoke, sometimes literally.


Often folks whose writing makes you wonder what they're smoking would be less trusted than those who can put a complete sentence together and who can and will point you to authoritative references sources.


I encourage you to learn as much as you can. You learned how to sail and run a boat. Lotsa people think just doing that is impossible.


None of was born an electrician. We all learned, You can and should, too.


Good luck, you can do it.

I agree with he.

From my eyes. Granddad was an electrician and an electrical engineer. Dad was an instrument technician (fine electronics) and some sort of engineer in electrical discipline field. I studied electrical AND electronic engineering for many years at uni.

Can take my time to type correctly but if you can't embrace a clue, it'd be dangerous to do IT and have it operational. Pitch yaw rotation underway.

I'd look into switches brother and share via isolation one simple system of multiple banks.
Then if times did get awkward, mix and match battery techs via seperate banks would not only be allowable depending upon availability; it'd be safe to do so.

[Hermia II]

Hi again, As to how many LiFePo4 batteries can be connected in parallel and series, according to Victron their batteries can be connected 4x12v batteries in series (48v) AND 5x such array in parallel. This means 20x12v batteries (I have confirmed this with Victron).

I think this has something to do with the capacity of the BMS, but that is a guess.

Here's a good link: https://www.victronenergy.com/upload...limited-EN.pdf

[mitiempo]

Originally Posted by Hermia II

Hi again, As to how many LiFePo4 batteries can be connected in parallel and series, according to Victron their batteries can be connected 4x12v batteries in series (48v) AND 5x such array in parallel. This means 20x12v batteries (I have confirmed this with Victron).

I think this has something to do with the capacity of the BMS, but that is a guess.

Here's a good link: https://www.victronenergy.com/upload...limited-EN.pdf

That only applies to Victron.

[Philip Hoag]

"what they're smoking".
Big egos.
The system I suggested had input from many "experienced" including a "lowly" electrical engineer. But most important, it has been working flawlessly for over 6 months. Beware of armchair experts!

[Paul54]

Contact the manufacturer of the batteries you are wanting to buy. Hopefully they will know. Lots of information in this thread, some good, some bad, and some scary.
The term BMS has been bandied about, as if they are all the same. They are not.
Some can be paralleled, some can with limitations, some cannot. Ask the manufacturer.

Somethings to consider:

What happens to your alternator when the batteries disconnect?

Many BMS have no low temperature or high temperature disconnect. Some say they have it, but it doesn’t work. Are you ever going to send a charge to your batteries when they are below 0 degrees C?

How do you deal with “float” voltage?

I was originally going to buy pre-made 12 volt drop in replacement batteries, just to avoid all of the confusion. But no one manufacturer or multiples could meet my needs or answer my questions. Also the moneys without guarantees got to be too high for me. At the time my only recourse was to begin a DIY solution and keep asking questions. Good luck to you.

[T1 Terry]

Originally Posted by Philip Hoag

"what they're smoking".
Big egos.
The system I suggested had input from many "experienced" including a "lowly" electrical engineer. But most important, it has been working flawlessly for over 6 months. Beware of armchair experts!

I would not be using a 6 mth faultless operation as a recommendation the system is working well. Even some of the clearly bad installs I've had through the shop lasted more than 6 mths before the problems surfaced.
Simply not knowing what is happening inside a sealed drop in battery doesn't mean everything is working fine, it just means that when it fails it will come as a surprise and without warning ..... the death spiral for the whole battery pack from a single bad cell in one of a parallel string of batteries, is near vertical.
About the only thing that might slow the death down a bit is the charge current limiting within each drop in battery. It should open circuit the charging and isolate the battery if the charge rate is exceeded ...... how long it remains disconnected is an unknown and what parameters are set for a re-connect will vary between different BMS systems. Our system for instance, required a manual re-connect to the system and the fault that caused the disconnect would have to be corrected before it will reset.
Some systems are just a heat related by metal strip disconnect, so once it cools it will reconnect until eventually the BMS itself fails.

Has anyone got 5 yrs or more information from a paralleled battery bank used for long term operation or full time use?

As I said previously, we have systems over 10yrs old that are in use 24/7 and when tested they delivered over 100% of the advertised capacity using the same test loading as the manufacturer uses.

We are about to service and test a battery pack that is just over 8 yrs continuous operation. This system is in a van that doubles as the camp kitchen during harvest on their kids properties, so they get worked real hard

T1 Terry

[piloto]

Originally Posted by henryk

I'm getting a 'drop in' boxes with BMS built in. Electrical and electronics are not my forte , so i would like to make it as simple as possible. So, getting to my first questions. If I will get 6 batteries, 12 V, 100 AH each and connect them in parallel,would BMS take care of even charging distribution ?

The way around the parallel problem would be to connect the batteries to a common buss bar (one + and one -), thus providing equal draw and charging capability.

[T1 Terry]

Originally Posted by henryk View Post
I'm getting a 'drop in' boxes with BMS built in. Electrical and electronics are not my forte , so i would like to make it as simple as possible. So, getting to my first questions. If I will get 6 batteries, 12 V, 100 AH each and connect them in parallel,would BMS take care of even charging distribution ?

Originally Posted by piloto

The way around the parallel problem would be to connect the batteries to a common buss bar (one + and one -), thus providing equal draw and charging capability.

The only BMS that will go close is the Victron system using all Victron equipment. The batteries still have to be individually charged and balanced, but apparently the system can handle it from there ...... but I don't know if there is a maintenance period where the system needs to be pulled down again and each battery charged and balanced again.

Unless the BMS can communicate with each cell in all the batteries
and
be able to move capacity from one cell in any battery to another cell in any battery
and
able to identify which battery has the high cell so it can stop charging that battery and/or the low cell so it can isolate the load from that battery but keep the charging going
and
calculate the loss of capacity for each battery isolated so the total load can be adjusted so the remaining battery pack is not overloaded
and
limit the maximum charge or discharge to any single battery so the batteries charge or discharge rating is not exceeded

then the BMS can't do what you ask ....... As far as I know, there is no such BMS available because there is no access for a BMS to communicate with a drop in battery and there is no separate terminals for charging and discharging ...... Unobtainium would be a good name for the particular BMS you are looking for ......

T1 Terry