Agm to Lithium conversion?

[SunUpNeverdown]

if I’m switching from 238ah of agm to lithium, how many amp hours of lithium would I need? 25, 35?

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[wew lad 5,000+ posts]

if I’m switching from 238ah of agm to lithium, how many amp hours of lithium would I need? 25, 35?

Depends on your alternator output and your current draw. I wouldn't go less than 50ah of lithium if you have one or two alts

 

[SunUpNeverdown]

One 390 amp alternator. Will be using on about 5000 rms before rise and about 3500 to 4000 rms after rise

 

[SunUpNeverdown]

On the limitless Lithium website it says the 25ah batt is equivalent to 2.5 100ah agm batts, so 250ah. And it says on a 150 amp alternator for charging. So I’m guessing those numbers are the numbers on a 150 amp alternator or greater.

 

[SunUpNeverdown]

I’ll be drawing about 450 to 475 amps even at the biggest draws. But after rise, less amps probably like 100 or so amps less if I had to guess.

 

[wew lad 5,000+ posts]

150a into a 25ah lithium is stupid. The ratings these manufacturers put out are absurd for longevity. That's 6c of charging and more when the alt is cold. Most lithium batteries want 1-2c of charging max. But whatever, what do I know?

I refuse to touch any lithium battery unless I know the cells being used along with a spec sheet for a reason. 99% of the packs out there are <2 years old. I expect to see bad news in the next year or two for those abusing them.

You aren't running that much power. I'd consider 1-2 banks of caps as a better solution with around 100ah of AGM's considering you have ~200a of charging capacity.

For reference, I have 2 alts, clamp around 315dca at idle with two 55ah AGM's and 2 banks of caps on a taramps hd15k at .5 and unless it's really hot and I'm soft clipping I don't drop below 12v. I have two mid range amps but they're negligable. 800-1000a of draw at peak. Tones are obviously a different situation.

 

[SunUpNeverdown]

I thought capacitors aren’t the way to go? I thought capacitors were a waste of money? What do you mean 1 or 2 banks of caps. I’m confused. I have 2 119ah agm batteries. Can I just run one and be fine? Because one of the batteries is old and only charges to 12.69 and has dropped to 12.61 in 2 weeks. So I’m thinking of getting rid of it. Idk. What should I do and can you explain the whole cap thing to me? I’m not a noob but I’m not an expert. I know a little something but still need help.

 

[SunUpNeverdown]

What do you recommend in the cap department, what brand and how much farad?

 

[wew lad 5,000+ posts]

I thought capacitors aren’t the way to go? I thought capacitors were a waste of money? What do you mean 1 or 2 banks of caps. I’m confused. I have 2 119ah agm batteries. Can I just run one and be fine? Because one of the batteries is old and only charges to 12.69 and has dropped to 12.61 in 2 weeks. So I’m thinking of getting rid of it. Idk. What should I do and can you explain the whole cap thing to me? I’m not a noob but I’m not an expert. I know a little something but still need help.

Yes. If you convert to lithium you have to completely get rid of lead acid (AGM) batteries due to differences in nominal voltages between them.

1-5f caps are garbage. They're usually the large 2 liter bottle looking things. Maxwell or XS power banks of caps end up being around 450f (3000f per cap, in series it's 3000f/6).

One battery and 1-2 banks of caps along with your alts will give you what you need. There's a lot of hype around lithium right now. Whether it be LTO (which look decent) and other chemistries but there's a lot of unknowns when it comes to longevity. On music, a cap can discharge and charge at a rate that well exceeds alternator and amplifier output so your alternators will essentially see a constant "max" load and the caps take care of the rest.

Hard to describe until you see a build in person and watch the voltage. You're talking <$400 for 2 banks of caps and the life cycle is a factor of 10 or even 100x as long

I have a few extra banks hanging around if you want to buy one and see how it goes (not trying to push selling them, clearly I haven't even listed them for sale). Otherwise there's a bunch of facebook groups you can buy a bank for <$200 on.

 

[SunUpNeverdown]

so I just get 6 of these?

 

[SunUpNeverdown]

or do I just get one of these?

 

[SunUpNeverdown]

or do I get this?

 

[SunUpNeverdown]

And if I go with the cells I would have to wire them in series? Could I just get the 12v Xs power SuperBank cap (the second pic that looks like a regular car battery) to make it easier?

 

[SunUpNeverdown]

Never mind. I found out. It’s all the same. Can I get away with just running one bank?

 

[SunUpNeverdown]

And where do I wire the superbank in unison with my front battery, one agm battery and amp?