LTO Starter Battery

grinchy

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Here’s how to raise the alternator voltage to above 15v


I haven’t seen where to LOWER the voltage. I watch mine and it never goes above 13.9, but that probably isn’t good enough to design a system around.
 
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I'm all for hacking but I just don't get the why. It's like shoehorning in a solution that is a compromise to the original system design.

LTO just aren't great for 12V systems because of the voltage mismatch. Either too high or too low. Risk overtaxing the native 12V system, or too low and either way are a compromise to capacity. Then a 35Ah LTO is ~1/3rd of the original group 27 battery capacity. It's often said for a FLA, only use half the capacity. The reality is that there is still utility of the full amount, built in emergency reserves if you will. Just that using more half capacity (regularly) may trade life to some minor degree. With such a small LTO battery the likelihood of being stranded is still much higher. Then considering the overload risk to the alternator for a battery in a low state of charge.

It's designed as a system. A great battery in a system designed for a different chemistry....makes for an objectively worse system.


Since we're talking about alternative batteries, meet this bad boy. Not for the car but an RV. The cruiser gets a high quality FLA.

View attachment 3007369

TL:DR.
IF cars couldn't run properly on 11-14v (which they can) FLA would be the better option.
IF you are not using the car as a weekly driven car, you would need to charge manually, FLA or LTO
IF you charged the LTO from flat to full, you may have an issue (which doesn't happen)
Given real-world scenarios, FLA is objectively worse than LTO, although some adjustment is required for LTO (such as running 5s and lowering charge voltage to 13.5)

I am all for constructive criticism, it makes me consider more variables than I may have originally. Yes, LTO is not great for 12v systems. The question then becomes "Is it really a 12v system?" If you look at car audio guys, they regularly run 15v and don't seem to have any issues. Considering the inherent voltage drop to the car systems, plus the built-in capacity to go higher than 12 v, LTO doesn't look so bad. The starter seems to be the most directly connected system, which is not really an issue. Other systems will have some inherent voltage drop as well, also a capacity to run at 14v (or so).
In regards to them not being ideal, you are absolutely correct! In regards to "will it work?" that seems fairly certain.

35Ah is consistent with most FLA batteries sold in Aus, taking into account the 50% margin you mention. Is this an issue for a rarely driven car? Absolutely!* Is it an issue with a daily driver? No. The same goes for charging an LTO battery from an alternator. Assuming you have a "dumb" alternator, then charging for an hour at 35 amps is probably not good for it (or charging at 70 amps for 30 minutes). Will that even happen? Probably not. Taking into account my use case as a daily driver, the only drains will be starting and parasitic drains (car alarm etc). Starting takes 2 seconds (at worst) at 300 amps. The sitting drain should be 0.05 amp. So to recharge the battery after sitting for 5 days, starting draw for 2 seconds, would take a total of 30 seconds or less. (cranking amps at 300 amps for 2 seconds, idle draw 0.05 amp for 24x5 hours, recharging from alt at 30 amps)

I am unsure how you mean the power system is designed for a different chemistry. I see this as an argument similar to "the existing charging is inefficient, so if you put it on yours, the inefficiencies will make it bad." However, if you work from first principles and ask "can the charging system work, even though it is made to work with poor batteries?" you have a different question.
Yes, FLA needs float etc, but this is not required for LTO. FLA has a charging efficiency of 75-80%, whereas LTO is close to 100%. This means an LTO system is inherently "better" for the charging system. It also means that the "reserves" of a FLA are only available if/when you inefficiently charge them for extended periods, thus putting more strain on the alternator. I can't say that FLA is better for the charging system, given these numbers, and the use case.

Given the use case, and the capacity of the car's electronics to work comfortably at 14.5v, I don't see FLA being better. Plus they cost more...

The server rack LiFePO4 batteries are amazing, best chemistry for solar setups.

*On further consideration... a FLA will self-discharge at about 4%/week. LTO will self-discharge negligibly in that time. A 300 Ah FLA will discharge about 12 amp in the first week, so at some point the LTO will be better, in regards to capacity remaining. The math is too hard for me to bother doing atm though :D You would expect about 8Ah draw from sitting draws per week. An LTO would probably start a car after 2+ weeks, same as a FLA. Any more than that and I would expect you to charge/run either battery for s while. The FLA will take longer to recharge in this case.
 
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TL:DR.
IF cars couldn't run properly on 11-14v (which they can) FLA would be the better option.
IF you are not using the car as a weekly driven car, you would need to charge manually, FLA or LTO
IF you charged the LTO from flat to full, you may have an issue (which doesn't happen)
Given real-world scenarios, FLA is objectively worse than LTO, although some adjustment is required for LTO (such as running 5s and lowering charge voltage to 13.5)

I am all for constructive criticism, it makes me consider more variables than I may have originally. Yes, LTO is not great for 12v systems. The question then becomes "Is it really a 12v system?" If you look at car audio guys, they regularly run 15v and don't seem to have any issues. Considering the inherent voltage drop to the car systems, plus the built-in capacity to go higher than 12 v, LTO doesn't look so bad. The starter seems to be the most directly connected system, which is not really an issue. Other systems will have some inherent voltage drop as well, also a capacity to run at 14v (or so).
In regards to them not being ideal, you are absolutely correct! In regards to "will it work?" that seems fairly certain.

35Ah is consistent with most FLA batteries sold in Aus, taking into account the 50% margin you mention. Is this an issue for a rarely driven car? Absolutely!* Is it an issue with a daily driver? No. The same goes for charging an LTO battery from an alternator. Assuming you have a "dumb" alternator, then charging for an hour at 35 amps is probably not good for it (or charging at 70 amps for 30 minutes). Will that even happen? Probably not. Taking into account my use case as a daily driver, the only drains will be starting and parasitic drains (car alarm etc). Starting takes 2 seconds (at worst) at 300 amps. The sitting drain should be 0.05 amp. So to recharge the battery after sitting for 5 days, starting draw for 2 seconds, would take a total of 30 seconds or less. (cranking amps at 300 amps for 2 seconds, idle draw 0.05 amp for 24x5 hours, recharging from alt at 30 amps)

I am unsure how you mean the power system is designed for a different chemistry. I see this as an argument similar to "the existing charging is inefficient, so if you put it on yours, the inefficiencies will make it bad." However, if you work from first principles and ask "can the charging system work, even though it is made to work with poor batteries?" you have a different question.
Yes, FLA needs float etc, but this is not required for LTO. FLA has a charging efficiency of 75-80%, whereas LTO is close to 100%. This means an LTO system is inherently "better" for the charging system. It also means that the "reserves" of a FLA are only available if/when you inefficiently charge them for extended periods, thus putting more strain on the alternator. I can't say that FLA is better for the charging system, given these numbers, and the use case.

Given the use case, and the capacity of the car's electronics to work comfortably at 14.5v, I don't see FLA being better. Plus they cost more...

The server rack LiFePO4 batteries are amazing, best chemistry for solar setups.

*On further consideration... a FLA will self-discharge at about 4%/week. LTO will self-discharge negligibly in that time. A 300 Ah FLA will discharge about 12 amp in the first week, so at some point the LTO will be better, in regards to capacity remaining. The math is too hard for me to bother doing atm though :D You would expect about 8Ah draw from sitting draws per week. An LTO would probably start a car after 2+ weeks, same as a FLA. Any more than that and I would expect you to charge/run either battery for s while. The FLA will take longer to recharge in this case.

All good points. I'm in for a good technical discussion so don't take my points as argumentative. Trying to help with "systems thinking" which sometimes gets lost at the detail pro/con level.

What I mean by compromise to a vehicles 12V system, is that it's hard to realize its full capacity potential, because of the charging profile and voltage mismatch
-5S: 11.25 - 13v, only ~402Wh of potential, and uncomfortably close or will be overcharged
-6s: 13.5 - 15.6, never going to charge to 15.6V, with possible max charge about 14V on a good day, so about ~490Wh

A standard OEM battery is worth 800Wh+. If we're conservative and assume half draw, matches LTO.

In a car, self-discharge isn't the big variable. It's parasitic draw of the car itself. As demonstrated above, lead acid will easily match reserve wise, with full capacity reserves to go beyond LTO.

A real upgrade would be a group 31 lead acid. Sure, the weight point is a good one, and 20lbs more than the factory group 31 maybe a good trade for something that has 1500Wh of juice. And drops right in without any compatibility issues to solve.
 
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All good points. I'm in for a good technical discussion so don't take my points as argumentative. Trying to help with "systems thinking" which sometimes gets lost at the detail pro/con level.

What I mean by compromise to a vehicles 12V system, is that it's hard to realize its full capacity potential, because of the charging profile and voltage mismatch
-5S: 11.25 - 13v, only ~402Wh of potential, and uncomfortably close or will be overcharged
-6s: 13.5 - 15.6, never going to charge to 15.6V, with possible max charge about 14V on a good day, so about ~490Wh

A standard OEM battery is worth 800Wh+. If we're conservative and assume half draw, matches LTO.

In a car, self-discharge isn't the big variable. It's parasitic draw of the car itself. As demonstrated above, lead acid will easily match reserve wise, with full capacity reserves to go beyond LTO.

A real upgrade would be a group 31 lead acid. Sure, the weight point is a good one, and 20lbs more than the factory group 31 maybe a good trade for something that has 1500Wh of juice. And drops right in without any compatibility issues to solve.

I took your points as factual rebuttals to what I said, all being factually correct!

Yeah, I DO sound like I want to believe that LTO is better, which is a good indicator that I am trying to MAKE it better, rather than being more objective.

Essentially I will be trying a 5s, as long as the alt doesn't charge it too high. If it does charge it too high, I will go to 6s and do the "big 3" that the audio guys do, and have the LTO's charge to at least 14.5v, and see how that goes.

My biggest issue with FLA? They cost a bunch and need to be replaced often. Or cost even more, and need to be replaced less often. Objectively I should be looking at LiFePO4 like Headway cells, 5s2p usable between 12 and 15v. They fit much better for the use case and can be cycled 2k times, probably more with car use. The thing I keep coming back to is that LTO's are as close to a "forever" battery as you can get. (Aside from Edison batteries, which have terrible other characteristics) You can even buy the headway cells and case for less than FLA and they should last longer....

Regardless I am committed to trying, we will see if I can make it work!
 

linuxgod

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I took your points as factual rebuttals to what I said, all being factually correct!

Yeah, I DO sound like I want to believe that LTO is better, which is a good indicator that I am trying to MAKE it better, rather than being more objective.

Essentially I will be trying a 5s, as long as the alt doesn't charge it too high. If it does charge it too high, I will go to 6s and do the "big 3" that the audio guys do, and have the LTO's charge to at least 14.5v, and see how that goes.

My biggest issue with FLA? They cost a bunch and need to be replaced often. Or cost even more, and need to be replaced less often. Objectively I should be looking at LiFePO4 like Headway cells, 5s2p usable between 12 and 15v. They fit much better for the use case and can be cycled 2k times, probably more with car use. The thing I keep coming back to is that LTO's are as close to a "forever" battery as you can get. (Aside from Edison batteries, which have terrible other characteristics) You can even buy the headway cells and case for less than FLA and they should last longer....

Regardless I am committed to trying, we will see if I can make it work!
I have an LFP in my camper. They will suck as a starting battery. They have less cranking power than an SLA/FLA and you can’t charge them below 32F or discharge below about 15F. Similar limits on the high side after 120-130F.
 
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All righty then. Slow boat has arrived, LTO cells are getting a test. Computer died yesterday, so testing and reporting may take a while.
Interestingly the LTO Yinlong cells I have, seem to have a voltage range of 1.9-2.5v, rather than the usual LTO of 1.8-2.8v. Not that I used that anyway, but it is interesting none the less.

As for having LFP as solar, they are amazing, the standard cells are not capable of high discharge rates, but that isn't an issue usually. The Headways are specifically designed for high amps, most LFP are not.
 

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