100AH Lithium cant handle start up draw

[67cj5]

FWIW, I recently replaced my two 95 amp/hr FLA house batteries with one 100 amp/hr BB and after a 10 day off grid trip I'm thrilled to death with the change. Saves weight and space, performed much better, and can be recharged with my 45 amp charger in a fraction of the time compared to the old batteries. It's like my 12 v fridge, I'll never go back to an ice chest and I'll never go back to FLA.

This is a great time to be building these vehicles, There seems to be new high tech stuff coming out every week, And I agree about owning a good fridge, I use mine everyday.

 

[dreadlocks]

Yep, I too found that I didnt need as much AH on LFP as I did on Lead.. its a combination of factors and not just Oh well you can discharge it 30% more that are quite substantial when all added together.

Yes, you can discharge it deeper w/out abuse.. however they also:

• Take less capacity for intermittent high power things like Microwaves since it draws em down so much less.. Microwave using 10AH LFP would use 20AH+ of FLA capacity.
• Charge so much faster, that 6-8h of Generator/Engine/Solar input normal FLA's need to fully charge can charge you can recharge LFP 2-3 times..
  • This means if you run your generator/engine every 2-3 days, you can now run your generator daily and after 2-3 days still have less overall runtime/fuel required.. etc
  • You dont need to drive 6-8h between camps to show up at the next one with a full battery bank, 2-3h drive is all you need and your bank will be full.. if you drive daily, you dont need to drive much.
• Mobile Fixed/Portable Solar is far more effective when it can dump its full power into storage all the time, any time.. instead of sitting in perfect lighting conditions finally, yet the battery is only wanting a tiny fraction of its output.. with lead, 200W per 100AH is about as high as you can go before you stop seeing any returns for your money/space/weight.. with LFP, you can go up to like 600W+ per 100AH and it'll use it, and now you dont need a full solid day of direct sunlight to recharge, just a few hours.. this is alot easier to achieve on the road when conditions are unpredictable.
• Less anxiety about battery's getting low since it takes sooo little effort and time to get em back to full.. Suddenly the desire for 4-5 days of off the grid capacity is gone and 2-3 days seems plenty.. If my new found environment lets me get 3-4h of sunlight regularly every day, hell all I need to do is get through the night really, 80AH a day is a ton for me coming from I can barely make 20AH a day work.

All that and more adds up, I've found my tiny, seemingly weightless 100AH LFP bank provides me with more storage than I actually require.. compared to my last 260AH FLA bank, that had similar but ultimately lighter loads and did not seem like I had adequate enough storage since I was always struggling to get the batteries back to full with the time thats required and cant really be worked around easily.

 

[shade]

FWIW, I recently replaced my two 95 amp/hr FLA house batteries with one 100 amp/hr BB and after a 10 day off grid trip I'm thrilled to death with the change. Saves weight and space, performed much better, and can be recharged with my 45 amp charger in a fraction of the time compared to the old batteries. It's like my 12 v fridge, I'll never go back to an ice chest and I'll never go back to FLA.

Yep, I too found that I didnt need as much AH on LFP as I did on Lead.. its a combination of factors and not just Oh well you can discharge it 30% more that are quite substantial when all added together.

Yes, you can discharge it deeper w/out abuse.. however they also:

• Take less capacity for intermittent high power things like Microwaves since it draws em down so much less.. Microwave using 10AH LFP would use 20AH+ of FLA capacity.
• Charge so much faster, that 6-8h of Generator/Engine/Solar input normal FLA's need to fully charge can charge you can recharge LFP 2-3 times..
  • This means if you run your generator/engine every 2-3 days, you can now run your generator daily and after 2-3 days still have less overall runtime/fuel required.. etc
  • You dont need to drive 6-8h between camps to show up at the next one with a full battery bank, 2-3h drive is all you need and your bank will be full.. if you drive daily, you dont need to drive much.
• Mobile Fixed/Portable Solar is far more effective when it can dump its full power into storage all the time, any time.. instead of sitting in perfect lighting conditions finally, yet the battery is only wanting a tiny fraction of its output.. with lead, 200W per 100AH is about as high as you can go before you stop seeing any returns for your money/space/weight.. with LFP, you can go up to like 600W+ per 100AH and it'll use it, and now you dont need a full solid day of direct sunlight to recharge, just a few hours.. this is alot easier to achieve on the road when conditions are unpredictable.
• Less anxiety about battery's getting low since it takes sooo little effort and time to get em back to full.. Suddenly the desire for 4-5 days of off the grid capacity is gone and 2-3 days seems plenty.. If my new found environment lets me get 3-4h of sunlight regularly every day, hell all I need to do is get through the night really, 80AH a day is a ton for me coming from I can barely make 20AH a day work.

All that and more adds up, I've found my tiny, seemingly weightless 100AH LFP bank provides me with more storage than I actually require.. compared to my last 260AH FLA bank, that had similar but ultimately lighter loads and did not seem like I had adequate enough storage since I was always struggling to get the batteries back to full with the time thats required and cant really be worked around easily.

Both of you illustrated why I'm still considering LFP. I know my truck is fairly heavy, but it'd be far worse if I didn't keep an eye on weight.

Any reason not to put an LFP under the hood for use as a house battery? I know it can be done, but that's not the kindest environment. I'd rather not give up cargo space in the truck cab or bed, and installation in the engine bay would simplify wiring.

 

[luthj]

High underhood temps will reduce battery life due to aging. Some engine compartments aren't really that hot. some are crazy. Some well placed insulation/divider, which allows cooler external air around the battery, can help dramatically. Take a long drive on a hot day, idle for 10 minutes. Pop the hood and check the temperatures are your desired location.

Given they can be mounted in any orientation, you could just strap the (light/small) lithium pack to the frame rail, or any workable location.

 

[john61ct]

Many cell manufacturers state they should only be use in their upright position.

I would install them in the coolest possible location, huge longevity factor

 

[shade]

High underhood temps will reduce battery life due to aging. Some engine compartments aren't really that hot. some are crazy. Some well placed insulation/divider, which allows cooler external air around the battery, can help dramatically.

Given they can be mounted in any orientation, you could just strap the (light/small) lithium pack to the frame rail, or any workable location.

Either space I have under the hood can probably be isolated from heat fairly well. Space is tight, so another location might work better anyway.

I'm also considering building a battery box around a 50Ah battery, and isolating it to just powering a fridge, which is my only significant load over time. The battery box would be small enough to sit next to my fridge on the slide, and solar charging could keep it going for many days. A 50Ah battery would also keep the budget more reasonable. The rest of the minimal loads (LED lighting & phone charging, really) could still be run off the Group 31 starting battery under the hood, which would keep existing wiring as it is.

 

[shade]

Many cell manufacturers state they should only be use in their upright position.

I would install them in the coolest possible location, huge longevity factor

Thanks. I'd take a hard look at the specs of any battery I used, regardless of chemistry. After reading many of Rod's articles, I don't want to be added to his rogue's gallery of battery murderers on Marine How To.

 

[dreadlocks]

or just slap a cheap ass digital thermometer into your battery box for a few weeks now in the heat of the summer and then pull it out and check its max temp readings.. some double sided tape or something so its not making contact w/terminals.

this i think would be more accurate because the thermometer would be absorbing radiant heat off engine/radiator like a battery would.

 

[john61ct]

Thanks. I'd take a hard look at the specs of any battery I used, regardless of chemistry. After reading many of Rob's articles, I don't want to be added to his rogue's gallery of battery murderers on Marine How To.

Maine Sail or CMS are his online handles.

Actual name is RC (Rod) Collins, but hardly ever used in this context.

 

[shade]

Maine Sail or CMS are his online handles.

Actual name is RC (Rod) Collins, but hardly ever used in this context.

Yes, Rod. That man loves batteries.

 

[67cj5]

With the 100Ah version of these batteries If you used about 60% of it's power, If you sat it on the Bench How long would a 20/25 Amp smart charger take to recharge it ?,

I understand that they except being charged faster than an FLA DC which can take between 4 to 8 hours depending on the SoC but how much faster are they ?.

 

[dreadlocks]

With the 100Ah version of these batteries If you used about 60% of it's power, If you sat it on the Bench How long would a 20/25 Amp smart charger take to recharge it ?,

I understand that they except being charged faster than an FLA DC which can take between 4 to 8 hours depending on the SoC but how much faster are they ?.

Comparison Between Battle Born LiFePO4 and 6V GC2 Batteries in Series

The comparison of discharge & charging profiles between one Battle Born 12 V 100 Ah LiFePO4 battery and two GC2 batteries connected in series.

battlebornbatteries.com

TLDR: 11.8V to 14.4V @ 40A Charger, same charger/settings used on both.
LFP: 2.5h
FLA: 5h

Thats just at 0.4C charge rate, technically the BB will take up to 1C charge rate (100A) but they recommend not going over 0.5C (50A) for longevity.. more advanced LFP banks can go alot higher than that w/active cooling measures.

 

[dwh]

With the 100Ah version of these batteries If you used about 60% of it's power, If you sat it on the Bench How long would a 20/25 Amp smart charger take to recharge it ?,

I understand that they except being charged faster than an FLA DC which can take between 4 to 8 hours depending on the SoC but how much faster are they ?.

100-60=40

A 100ah LiFePo4 will easily accept 100a or more of current. So the 20a charger would be running flat out at its max of 20a...unless the smart charger did something stupid like throttle itself for some reason.

So, two hours, give or take.



They don't need, or want, an absorb stage, so just pump them up to VoltageX (whatever their specified voltage is) and turn off the charger, you're done.

 

[67cj5]

Simple math.
60% of 100Ah is 60Ah consumed..go figure...!
So, a 20A charger should take what, about 7 days to replenish ??
Lithiums can charge considerably faster. To know how fast, one needs to find the ”C” rating of the battery in question.

I don't understand why you say 7 days ?, At 60 Amps using a 20 Amp charger should equal 3 hours on paper,

Comparison Between Battle Born LiFePO4 and 6V GC2 Batteries in Series

The comparison of discharge & charging profiles between one Battle Born 12 V 100 Ah LiFePO4 battery and two GC2 batteries connected in series.

battlebornbatteries.com

TLDR: 11.8V to 14.4V @ 40A Charger, same charger/settings used on both.
LFP: 2.5h
FLA: 5h

Thats just at 0.4C charge rate, technically the BB will take up to 1C charge rate (100A) but they recommend not going over 0.5C (50A) for longevity.. more advanced LFP banks can go alot higher than that w/active cooling measures.

That is what I was thinking, So what your saying is that they can charge at the rated or speed of the charger they are connected to, ?

 

[shade]

100-60=40

A 100ah LiFePo4 will easily accept 100a or more of current. So the 20a charger would be running flat out at its max of 20a...unless the smart charger did something stupid like throttle itself for some reason.

So, two hours, give or take.



They don't need, or want, an absorb stage, so just pump them up to VoltageX (whatever their specified voltage is) and turn off the charger, you're done.

Without a battery management system limiting the current to an LFP battery, can it overload an alternator? I know this article is generally referring to much larger battery banks, but the principle seems to apply in this case, too.

Automotive Alternators vs. Deep Cycle Batteries - Marine How To

A Deep Cycle Battery Assassin The alternator pictured here helped to destroy a very expensive bank of TPPL AGM batteries in under two years. These batteries need an absorption voltage of 14.7V. The highest voltage I recorded on this vessel was 13.58V at the battery terminals. At this

marinehowto.com