Fastest to charge longevity balance

[IIHomieII]

Hello all!

I am in the design phase of my solar system and would love some advice from the experts (Will Prowse you listening?)

My system will not be needed for 2 more years so I am in absolutely no rush as battery technology will change over 2 years so even new on the horizon untested battery tech (IBM) is fine with me for this discussion.

I will be limited in RV roof real estate to 300 ish watts of panels (Class B RV) so that is that..

My concern is that if I bought something simple like a Goal Zero 3000 which uses NMC that I am losing out versus going DIY but I might be wrong.

Again, cost is NOT the question but rather shortest charge time 1st and charge cycles life 2nd.

Here is the question: At present and in the near future (2 years) what is the best battery technology to charge quickly and get maximum charge cycles since 300 watts of solar mixed with alternator charging will be my only input for recharging the system. Lets say a 3000 watt hours system?

Its not that I have a problem replacing individual components overtime as they fail from normal use but I am wanting to know where the cut-off is, so lets say its Battery Tech A = fastest charging and less charging cycles OR Battery Tech B = middle of the road for both OR Battery Tech C which is slower to charge but maximum charging cycles.

Since I will only have alternator charging and 300 watts solar for restoring battery capacity I assume fastest charging is king.

I will be using most of the 3000 watt hours capacity on most days. (assume 80% usage of total capacity 5 days a week)

Considering my usage, is it best to accept that there will be a need to charge via an external power source?

I can obviously drive longer and use the alternator to charge but if gas costs for driving only to charge vs finding an external power source such as a camp ground etc (perhaps twice a week) I would rather be parked if its the same costs.

I don't expect anyone to know the costs of driving a 15 mpg vehicle for charging sake compared to varying campground costs but knowing I have the fastest charging rate (the solar controller I know, I know but just Battery Tech please) with a good or even poor charging cycle life is where I need guidance from the experts.

Any bonus advice that can be offered is also greatly appreciated!

 

[nosys70]

LFP (LiFePo4) charge usually at 1C maximum , advised 0.5C or even 0.3.
that could be important for small batteries, but for a 200Amps batteries, i doubt you would find enough current to overload the battery.
So with big batteries, the problem is usually the time required to charge batteries while sun is available.

 

[MisterSandals]

Just out of curiosity, how are you using 3000wh per day in a Class B rv?
Air conditioning?
Electric fridge?
Server farm?

 

[SolarRat]

Considering my usage, is it best to accept that there will be a need to charge via an external power source?

Yup, but you could always carry another ~350w panel on board, and deploy it once parked, which may give you enough charge on a sunny day.

Any type of lithium will charge much faster than lead acids, and accept a higher charge rate as well. Li-ion can probably accept a higher charge rate than most LFP's, but probably isn't worth the trade-offs, unless a really high charge rate is needed.

 

[IIHomieII]

Usage, 110-120v mini/dorm size compressor fridge running 24/7, 2 laptops with 2 people using them 8 - 10 hours a day 4 - 5 days a week, charging misc items like cell phones, tablets, perhaps a router. Basic home office stuff really. The stock interior lights and 12v water pump will be ran off a standard AGM 12v deep cycle battery. (The stock RV and all its systems will stay as a separate system)

As for carrying extra panels, it's just not an option but thanks for the suggestion.

That being said, I still need to know how superior LiFepo4 is compared to other lithium systems with this level of usage and speed difference in charging. For example does an NMC lithium setup take longer or just has a shorter life with charges. Again, fastest recharging type of battery tech. And if LiFepo4 is the quickest.. is it a minor difference to where it's only on paper but real world usage in my scenario will go unnoticed?. Thanks again for everyone who can add to the discussion!

 

[nosys70]

2 laptop : 100W/h
misc :50W/h
lights: 30W/h
fridge 300Wh.

so 500wh, for 10 hours is 5KWh then you need a 400A battery under 12V.
at 5 sunny hours a day, it is about 80Ah to charge the battery+ the 40A to get the 500W.
you need 120Ah from the solar panels. (1400W).

 

[IIHomieII]

Thank you, I think my problem is is giving too much detail and thus blurring the real question.

Instead I should just ask this one question:

When charging a lithium battery, which lithium battery type will recharge fastest and will it be noticable under the above conditions or just on paper?

Thank you!

 

[electric]

Thank you, I think my problem is is giving too much detail and thus blurring the real question.

Instead I should just ask this one question:

When charging a lithium battery, which lithium battery type will recharge fastest and will it be noticable under the above conditions or just on paper?

Thank you!

Hands down LiFePO4 ( a.k.a. LFP ) is the best for fastest recharge and longest life.

 

[nosys70]

every battery technology can use fast charge. (fast charge usually refers to 1C, if you need more, the term used is ultra fast charging)
but fast charging use different profile than linear charging, so you need to find a charger that allows that.(for example fast charge is used for the first 50-70% of capacity)
And with fast charge, you pay it by reducing the battery life, so it may be a concern.
Some special LiPo can be charged at 15C, but regular batteries usually advise 1C in normal condition and 2C in fast charge.
If we follow the calculation i gave above, your battery should be around 400Ah, so a 2C fast charge would be 800A.
i do not think you would find an alternator powerfull enough to deliver such current.

lithium titanate offers the best fast charging capacity.

 

[Craig]

Yes LTO batteries have highest lifecycle and can be charged at 10C. So 400 AH. Could take 4000 amps.
If you can find a cable large enough. 400 AH at 24v would cost about 6k.

 

[IIHomieII]

Hands down LiFePO4 ( a.k.a. LFP ) is the best for fastest recharge and longest life.

I have now read about Lithium Titanate or Li4Ti5O12 aka LTO (thanks for educating me!)

Yes, I agree according to what I and others such as yourself have read and researched but is it notiecable in real world usage under these conditions?

Or is it a nominal margin of improvement so a consumer could still opt for something like the Goal Zero which doesn't utilize LiFePO4 and not notice the difference??

In my calculations I see my usage on a work day as little as 1300W to as much as 2300W.

No RV Lights or pumps etc. Just 1 mini fridge, 2 laptops, 2 phones, 2 tablets. 1 Router, 1 5g Cellular Booster.

Depending on the temperature inside the vehicle, the Laptop fans and Mini Fridge may pull more or less power)

I included my usage because if somebody was/is using less power they certainly could buy a Jackery or Goal Zero and call it a day.

My power consumption (which is on the cusp of simple and overboard) defines the question of how much better IS LiFePO4 vs NMC, Titanate etc. with this level of consumption in a real world way. (Standard Home Office Usage)

Will it be noticed or is it irrelevant and either lithium battery type will suffice because the charging speed difference is moot at that consumption and recharge rate?

The LiFePO4 will win on paper and is a great tried and true option but what are we talking about?? 9 minutes of charging speed difference in a day? 2 hours? That's the question.. Nothing above 1C on the charge rate for an apples to apples comparison. The Yeti for example using NMC can still receive 300 watts to 750 watts via the vehicle alternator. That being the case (according to Yeti) even on the low side of 300 watts from the alternator, the system requires a 10 hour drive to recharge from near empty battery capacity. So if the Yeti did use LiFePO4? or Lithium Titanate? Would it be a large enough difference? a 9 hour drive to recharge? or 8 hours and 42 minutes? 6 hours!! lol.. That's what I am trying to determine at a normal 1C recharge rate if I should DIY and go with LiFePO4 or whatever.. besides saving money on the build/purchase.. what amount of recharge time am I really saving??

Its' like this is one of those questions in 14 parts

 

[Craig]

I honestly do not think you can throw enough power from a mobile system for it to make a difference. Here you are limited by how many panels you can place and process the energy from. In a stationary off grid system you can throw 100's of panels and tens of chargers at your batteries to utilize the fastest charging batteries possible.

 

[IIHomieII]

Thanks for all your help! great forum..

I figured it out enough anyways..

This level of consumption is definitely more simple than overboard for a drop in system.

For my usage, I will be under budget (power budget) for this home/mobile office setup.

Despite using a sub-par system like the Goal Zero compared to a DIY system with superior components and options galore, I will be able to recharge and discharge without concern. Despite using the Goal Zero lower performance PWM charger and the NMC Lithium Battery tech.
(You can't charge from the alternator and use the MPPT module at the same time so the built in PWM is the only option)

Even with only 300 watts of solar panels averaging around 200 watts of actual solar input for 5 - 6 hours a day I can stay under my power budget.

I still don't know what the speed difference in charging would be with a better DIY system using a MPPT controller and LiFePO4 battery tech but I can tell after an extensive power audit that this simple power usage will not need to be tweaked to the level of requiring a DIY system.

The above mentioned power usage is minimal enough to utilize a drop in system.

If in the future, if my power consumption changes to a greater amount or if another person with a larger consumption chose the drop in system they might regret it since a DIY system offers scalability but for now, I and anyone with similar power usage are in the clear with watts to spare and recharge time is definitely NOT a concern.

Here is a good example of this type of usage:

Home lost power because of storm etc.
You work from home AND your child is home schooled.

Utilizing a Goal Zero and setting some solar panels outside will enable you to conduct business/education repetitiously with phones, tablets and a mini fridge. You really don't even need the alternator (its just a bonus for bad solar days) let alone the fastest lithium recharging system.


Thanks again for everyone's comments and advice!