Lithium Upgrade - Step-by-Step?

[heizer1]

Hello everybody,

we renewed our lithium house bank this year with drop-ins with an overall capacity of 600ah.

As we are currently do not live on the boat, this is more than plenty. Still, we plan to move onboard within the next 3 years. As we are thinking of adding an AC, we will then need more ah in our house bank.

So, is it okay to upgrade the system maybe in 2 years with the same drop-ins to make it 1000-1200ah or is there any problem associated with that?

We had some help from a local marinero when installing the actual batteries, he mentioned that if we want to upgrade, we should do it within one year (with the same brand and size of battery), but wasn't really able to tell us why this is needed.

From a budget perspective we could also upgrade now, the bigger constraints I'm having is
- lack of time to implement it / make it work
- technology is advancing / batteries are getting cheaper
- having load on the new batteries / decreasing their lifespan without really needing it.

Really appreciate your thoughts and what you would do in this situation...

Thanks

[Pandor]

Advice given to add additional batteries within 1 year or sooner was accurate. Besides the difference in battery life left, you can’t count on the batteries still being available or manufactured the same two or more years down the road.

You want all cells to be as close to identical for optimal bank performance.

[pbiJim]

When I look at currently available, lower priced, "drop in" Lithium Iron Phosphate batteries with built in BMS, I often see statements that the number of batteries you can put into series or parallel is limited to 3 or 4. No explanation is given as to why this is. I am left curious.

The prices certainly have come down. I am seeing some drop in lithium batteries that are little more than $2 per Amp hour.

[wholybee]

The importance of matching LFP batteries that are placed in parallel is exaggerated. You could add capacity that is not only a different brand, but a totally different capacity, for example adding 200Ah to a 300Ah battery, and not likely notice any performance issues at all.

[Pete7]

Originally Posted by wholybee

The importance of matching LFP batteries that are placed in parallel is exaggerated. You could add capacity that is not only a different brand, but a totally different capacity, for example adding 200Ah to a 300Ah battery, and not likely notice any performance issues at all.

Indeed, we added a 100Ah LFP to the existing 2 year old 120Ah LFP this summer. During a 3 week trip away didn't notice anything untoward happening with the different sizes and age.

The only thing we need to take into account is the SOC percentage is different. This is because if you draw a heavy load eg cooking, then the smaller LFP will supply a larger percentage of power. Not that a % is particularly accurate and should only be used as a quick reference to see the % SOC.

Pete

[donradcliffe]

Originally Posted by Pandor

You want all cells to be as close to identical for optimal bank performance.

Optimal profits for the seller?

[Polar Opposite]

Originally Posted by wholybee

The importance of matching LFP batteries that are placed in parallel is exaggerated. .

I'm glad to read common sense answers that are matched with experience. Too often, advice veers toward high-end (expensive) gold-standard replies that are pure hearsay.

[sailorboy1]

Originally Posted by wholybee

The importance of matching LFP batteries that are placed in parallel is exaggerated. You could add capacity that is not only a different brand, but a totally different capacity, for example adding 200Ah to a 300Ah battery, and not likely notice any performance issues at all.

I agree and feel the same applies to batteries of different age. Yes not a "perfect" system, but hey we live on boats and nothing about the operation is perfect!

Maybe you only get 90% capacity of the new battery, but hey that is 90% MORE than you had.

[Tortuga's Lie]

Originally Posted by heizer1

Hello everybody,

we renewed our lithium house bank this year with drop-ins with an overall capacity of 600ah.

As we are currently do not live on the boat, this is more than plenty. Still, we plan to move onboard within the next 3 years. As we are thinking of adding an AC, we will then need more ah in our house bank.

So, is it okay to upgrade the system maybe in 2 years with the same drop-ins to make it 1000-1200ah or is there any problem associated with that?

We had some help from a local marinero when installing the actual batteries, he mentioned that if we want to upgrade, we should do it within one year (with the same brand and size of battery), but wasn't really able to tell us why this is needed.

From a budget perspective we could also upgrade now, the bigger constraints I'm having is
- lack of time to implement it / make it work
- technology is advancing / batteries are getting cheaper
- having load on the new batteries / decreasing their lifespan without really needing it.

Really appreciate your thoughts and what you would do in this situation...

Thanks

Did you go all LFP or do you still have lead? I ask this because all LFP may cause issues with your alternator.......

[heizer1]

Originally Posted by Tortuga's Lie

Did you go all LFP or do you still have lead? I ask this because all LFP may cause issues with your alternator.......

We had LFP before and have measurements for the alternators in place:::

Thank you for all the replies, calms me down to concentrate on projects which are more urgent.