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nice! ok so maybe the sound improvement wasn't just in my head lol
eager to hear more of your thoughts over the next few days!
i'd also recommend improving the insulation on the stock battery sleeve if you haven't done so yet
Thanks for the tip!

I love that I was able to crank up my music to 45 on the dial with the 1000W amp for 5 minutes before my ride and the battery only went down to 98%! 30 minutes of music listening with the engine off shouldn't make it break a sweat. Would it hurt the cells to test how long until it gets below a certain percentage with just music cranked up?

Turn-in feels slightly improved, but maybe indistinguishable from placebo effect.
 

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Discussion Starter · #43 ·
Thanks for the tip!

I love that I was able to crank up my music to 45 on the dial with the 1000W amp for 5 minutes before my ride and the battery only went down to 98%! 30 minutes of music listening with the engine off shouldn't make it break a sweat. Would it hurt the cells to test how long until it gets below a certain percentage with just music cranked up?

Turn-in feels slightly improved, but maybe indistinguishable from placebo effect.
If we look at this graph which shows the life cycle of A123's nanophosphate cells (2nd gen), then there shouldn't be any issue doing the occasional deep discharge. The ultraphosphate cells (3rd gen) in our batteries should last much longer ;)
281916

So you're saying reinforce the shielding to minimize engine heat on the battery? What did you use?
there's a link to the product from home depot i used in the post ;)
 

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If we look at this graph which shows the life cycle of A123's nanophosphate cells (2nd gen), then there shouldn't be any issue doing the occasional deep discharge. The ultraphosphate cells (3rd gen) in our batteries should last much longer ;)
View attachment 281916

there's a link to the product from home depot i used in the post ;)
Will look, thanks! I may run a back to back with the factory battery, seeing how long it takes each one to get to 75% with some hip hop cranked up. Do you know about how low it can go and still turn over the engine?
 

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Discussion Starter · #45 ·
Will look, thanks! I may run a back to back with the factory battery, seeing how long it takes each one to get to 75% with some hip hop cranked up. Do you know about how low it can go and still turn over the engine?
haha no i haven't tried running the battery down. i presume it'll still turn the engine over at 10% charge (~12.8V). a lead acid battery might struggle to start a car at 50% charge (~12.1V)
 

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haha no i haven't tried running the battery down. i presume it'll still turn the engine over at 10% charge (~12.8V). a lead acid battery might struggle to start a car at 50% charge (~12.1V)
The gen4 has a super quirky battery and electrical system. Having drained the battery several times while installing the sound system, it would go from 100% fine to not turning over the engine at all at the drop of a hat, and then charge back to 100% after a jump instantly. Maybe a fail safe of some sort where below X% it doesn't even bother trying to crank the engine.
 

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Discussion Starter · #48 ·
The gen4 has a super quirky battery and electrical system. Having drained the battery several times while installing the sound system, it would go from 100% fine to not turning over the engine at all at the drop of a hat, and then charge back to 100% after a jump instantly. Maybe a fail safe of some sort where below X% it doesn't even bother trying to crank the engine.
interesting... gen4s have a current meter on the battery terminals right? could be a loose connection/defective part.
i know most ECUs stop functioning at anything <9V
if you ran the OEM battery dead several times, then the battery is probably just dead and not holding a charge. lead acid batteries hate deep cycles
 

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interesting... gen4s have a current meter on the battery terminals right? could be a loose connection/defective part.
i know most ECUs stop functioning at anything <9V
if you ran the OEM battery dead several times, then the battery is probably just dead and not holding a charge. lead acid batteries hate deep cycles
Not aware of a current meter. It had no issues in the past months once I was done installing the sound system. Just that it drains super quick, and won't bother trying to turn over the engine below 9V or so. I'd be surprised if that's not all the gen4s based on reported issues so far.
 

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Discussion Starter · #50 ·
So i unintentionally found out what happens when the battery is discharged very low:

281978


11.5V on a 4S LiFePO4 battery is ~1% charge
at this level, it is not enough to provide any power to the vehicle (no remote unlock, no dash lights)
the voltmeter wont even turn on when connected to the vehicle, perhaps because quiescent draw from the vehicle drops the voltage too low.

after charging back up to 10% (12.2V), it will turn over the car albeit a little slower, but about the same as an old lead acid battery
@perseus so this answers the question of what the minimal SOC is for turning over a 2.5L 👍
 

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So i unintentionally found out what happens when the battery is discharged very low:

View attachment 281978

11.5V on a 4S LiFePO4 battery is ~1% charge
at this level, it is not enough to provide any power to the vehicle (no remote unlock, no dash lights)
the voltmeter wont even turn on when connected to the vehicle, perhaps because quiescent draw from the vehicle drops the voltage too low.

after charging back up to 10% (12.2V), it will turn over the car albeit a little slower, but about the same as an old lead acid battery
@perseus so this answers the question of what the minimal SOC is for turning over a 2.5L 👍
Neat! What did you use to charge or jump it and how long did that take?
 

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Discussion Starter · #52 · (Edited)
i put it on a cheap lifepo4 charger for a little less than an hour then tried starting up the car with it.
ETA: a round trip to+from work (~40-50 minutes total driving time), including a startup after work, was enough to bring it back to 100% charge
 

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Finally installed LifePo battery Antigravity ATX30-RS and loving it, also installed bluetoothooth battery tracker that is very handy way to keep tabs on the state of the battery (see screenshot of charge test)
I should have gotten a side by side picture of the stock battery next to this thing, stock battery was hard to lift with two hands whereas this 5.5lb little thing I could easily lift with one hand. The engine starts SO much faster, my stock battery was on its' way out so not necessarily a fair comparison, but really it cranks the motor faster than I can ever remember it cranking.

I used some foam to make the battery wide enough that it sits snuggly in the stock battery spot, and some old fuel line cut some little pieces to use as spacers to make the stock hold down work for this smaller battery

While I was in there I sanded off the paint on the grounding point and added a 2 gauge grounding wire in parallel to what is already there (that really thick wire visible in the attached pictures), I'm assuming that's upping my idle voltage a little, but I did not measure before and after, so maybe it's just piece of mind ;)
20210505_122520.jpg 20210505_122514.jpg Screenshot_20210505-125604.png
 

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Discussion Starter · #54 ·
The engine starts SO much faster, my stock battery was on its' way out so not necessarily a fair comparison, but really it cranks the motor faster than I can ever remember it cranking.
this is honestly my favorite thing about upgrading to LFP. The car starts up so eagerly like it's excited you're taking it for a drive lol.
 

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Finally installed LifePo battery Antigravity ATX30-RS and loving it, also installed bluetoothooth battery tracker that is very handy way to keep tabs on the state of the battery (see screenshot of charge test)
I should have gotten a side by side picture of the stock battery next to this thing, stock battery was hard to lift with two hands whereas this 5.5lb little thing I could easily lift with one hand. The engine starts SO much faster, my stock battery was on its' way out so not necessarily a fair comparison, but really it cranks the motor faster than I can ever remember it cranking.

I used some foam to make the battery wide enough that it sits snuggly in the stock battery spot, and some old fuel line cut some little pieces to use as spacers to make the stock hold down work for this smaller battery

While I was in there I sanded off the paint on the grounding point and added a 2 gauge grounding wire in parallel to what is already there (that really thick wire visible in the attached pictures), I'm assuming that's upping my idle voltage a little, but I did not measure before and after, so maybe it's just piece of mind ;)
View attachment 282023 View attachment 282024 View attachment 282025
Added a similar beefed up ground wire and insulation to mine today:

282173


Great battery so far. Have yet to go below 92%, even pushing it with the A/C on and music blaring. Always bounces back to 100% in under 10 seconds.
 

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Discussion Starter · #56 ·
Mazda was actually really smart about making the chassis-to-battery ground cable really short (=less voltage drop).

If you are to assume all 100A the alternator can put out is grounded through that wire, the voltage drop is still quite minimal (just 60mV):
282182

Beefing up that connection actually gains quite little (30mV):
282183


However, if you were to look at the engine ground, which goes through a tiny 8ga cable then through the chassis (which is by many accounts equivalent to 4ga OFC in modern cars), there is more voltage drop there:
282184

And if you ground the engine directly to the battery, you can reduce voltage drop by 0.14V, looking just at engine load (not including accessories):
282185


That's to say, there's more to gain from upgrading the ground from the engine (which also grounds the alternator, starter, throttle body), than from the chassis to battery.

And finally, the biggest source of voltage drop is probably from the alternator to the battery (490mV):
282186
 

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Mazda was actually really smart about making the chassis-to-battery ground cable really short (=less voltage drop).

If you are to assume all 100A the alternator can put out is grounded through that wire, the voltage drop is still quite minimal (just 60mV):

Beefing up that connection actually gains quite little (30mV):

However, if you were to look at the engine ground, which goes through a tiny 8ga cable then through the chassis (which is by many accounts equivalent to 4ga OFC in modern cars), there is more voltage drop there:

And if you ground the engine directly to the battery, you can reduce voltage drop by 0.14V, looking just at engine load (not including accessories):

That's to say, there's more to gain from upgrading the ground from the engine (which also grounds the alternator, starter, throttle body), than from the chassis to battery.

And finally, the biggest source of voltage drop is probably from the alternator to the battery (490mV):
So where is the engine ground and alternator ground?
Are you going to beef those up?
 
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