Please help me avoid a fire, 300A draw mixing chemistries & alternator charging only

[0bserver]

Hi folks long time lurker first time poster. Hopefully you can help me avoid building a fire hazard here.

I am building a 12 volt electrical bank to support a high current draw 100-250A continuous with 300A spikes. Hopefully you can help me clarify the best wiring configuration to make this work together safely or let me know if I need additional components. I am concerned about the BMS inside the Chins LifepO4 Bank. The specs give a max charge of 50A and max discharge of 100A. That is far below the 300A spikes it could see. After watching Will's video it looks like I can open the battery and upgrade all of the contacts, busbars and wires to thicker larger gauge but I am not sure if the components on the BMS are the actual bottleneck. If the BMS is the bottleneck can I add another BMS in Parallel to increase capacity? What BMS would you recommend?

Any input would be appreciated. I really want to get this right the first time and avoid frying equipment.

Components I have so far

1)The Chins LifepO4 he recommended here

2)Victron Energy 500A Smart Shunt

3)Maxwell Durablue 16V 500Farad Super Capacitor https://maxwell.com/products/ultracapacitors/modules/
4)DC Power High 270A High Output alternator https://cdn.shopify.com/s/files/1/0...-40fb-b418-46a4f9816d3f_900x.png?v=1549863543
5)12v XS Power AGM Battery

The BMS Specs are

Rated Capacity (0.2C): 100Ah / 1280Wh
Cycle life: 2000+ cycles at 80% discharge depth
Rated voltage: 12.8V
Charge voltage: 14.2 - 14.6V
Depth of Discharge (DoD): 100%
Standard charge current: 20A
Charging time: Approximately 6 hours
Max continuous charge current: 50A
Max continuous discharge current: 100A
Peak discharge current: 300A (Duration: less than 5 seconds)
Operating temperatures: Charge 0°C~50°C(32°F~122°F),
Discharge -20°C~60°C(-4°F~140°F), Storage -20°C~50°C(-4°F~122°F)
Impedance: ≤ 10mΩ


Thank you!

 

[rmaddy]

I am building an electrical bank to support a high current draw 100-250A continuous with 300A spikes.

Did you mean 100-250 watt with 300 watt spikes or do you really mean amps? And if you really do mean amps, are these at 12V? So are you really talking about 1200-3000 watt loads with 3600W spikes?

Assuming you do mean amps and at 12V then:

If you have a need for a 250A continuous draw and your battery is only rated for 100A max continuous draw then you need at least 3 of those batteries in parallel. And each battery should be fused at 125A.

Also note that a 100Ah battery will go from 100% to 0% in 24 minutes with a continuous 250A load. With 3 in parallel you get an hour of use.

You really need higher voltage (24V or 48V) and more capacity for such large continuous loads.

 

[0bserver]

Did you mean 100-250 watt with 300 watt spikes or do you really mean amps? And if you really do mean amps, are these at 12V? So are you really talking about 1200-3000 watt loads with 3600W spikes?

Assuming you do mean amps and at 12V then:

If you have a need for a 250A continuous draw and your battery is only rated for 100A max continuous draw then you need at least 3 of those batteries in parallel. And each battery should be fused at 125A.

Also note that a 100Ah battery will go from 100% to 0% in 24 minutes with a continuous 250A load. With 3 in parallel you get an hour of use.

You really need higher voltage (24V or 48V) and more capacity for such large continuous loads.

Thanks for the quick reply!

Yes, 12 volts and 300 amp spikes.

Does the AGM , ultracapacitors and HO Alternator fill the gap rather than additional batteries?

 

[rmaddy]

Yes, 12 volts and 300 amp spikes

You really need to look at higher voltage. 250A continuous with 300A spikes puts a lot stress on everything. Go to 24V and now you have 125A continuous with 150A spikes.

Does the AGM , ultracapacitors and HO Alternator fill the gap rather than additional batteries?

I didn't get that far in your post. I have no experience with any of those. But I do know you want avoid mixing battery chemistries since each one has different charging needs.

 

[0bserver]

You really need to look at higher voltage. 250A continuous with 300A spikes puts a lot stress on everything. Go to 24V and now you have 125A continuous with 150A spikes.


I didn't get that far in your post. I have no experience with any of those. But I do know you want avoid mixing battery chemistries since each one has different charging needs.

Unfortunately my equipment limits me to 12.6V-14.4 max

I was hoping the I could use the second battery hookup on the Smart Shunt to manage the lithium separately

 

[740GLE]

The smart shunt doesn’t manage anything, it just reports current flows.

Seems like an awful lot of load with minimal storage.

Will you be charging these via an alternator?

 

[0bserver]

The smart shunt doesn’t manage anything, it just reports current flows.

Seems like an awful lot of load with minimal storage.

Will you be charging these via an alternator?

I will be adding storage later. I would like to get the everything playing nice together first in regards to charge discharge.

All charging will be via 270A High Output alternator.

 

[soylentgreen]

I feel like we had a similar question before, and like before, my first response was "really? 300A at 12V" ?

Care to share what exactly you are doing that has such a high wattage + low voltage need? It's not impossible, just unusual.

Shorter answer:
If you really do need 300A @ 12V, then you need at least 3 of your batteries, wired in parallel.

 

[0bserver]

The biggest draw is an 8000 watt audio system.

I am open to changing configurations or adding components but I have to start at with a 12v alternator and end at 12V for the amplifiers.

 

[DerpsyDoodler]

Is your battery an auxillary battery primarily intended for car audio? It's easier for people to help if they better understand your application.

 

[0bserver]

Yes, the primary use will be for car audio. Limitless Lithium markets one for car audio but I cant justify $1,300 for 45ah. There has to be a cheaper safe way to incorporate lifepo4. What BMS do you think they are running in there?

Batteries - Page 1 - Limitless Lithium

limitlesslithium.com

 

[740GLE]

SPL competition? Or just rocking music on the commute to work?

A 6000w audio amplifier doesnt draw constant load like say a heater or something. So I think you’d be using this lifepo as a super cap, and let the alternator do the heavy lifting.

 

[0bserver]

It will be mostly Cars and coffee runs , Malibu if anyone wants to join. Rocking music for an hour or so at a time with the occasional full blast run for a song or two. Probably a few SPL burps in the parking lot. I picked up 100ah Lifepo4 & 500f Supercaps because some research like the video below (at the 15m mark) led me to believe the chemistries can compliment each other in these high current applications buffering the alternator and the AGM battery.

 

[fshan]

This is a site for 60Hz output from a dc source. Recovery for a capacitor going to an amp for subwoofers could be 1hz (mine) to 280hz according to your crossover. You're reactance changes according to the filters in your drivers so losing soundstage because of your bass is because of low impedence at that frequency. To maintain B+ you need capacitors. period. A battery can't respond and recover as fast as a capacitor no how no way. Then you need a power source(s) to maintain the voltage of your caps. Again it is too involved and not the correct forum.

 

[DerpsyDoodler]

It will be mostly Cars and coffee runs , Malibu if anyone wants to join. Rocking music for an hour or so at a time with the occasional full blast run for a song or two. Probably a few SPL burps in the parking lot. I picked up 100ah Lifepo4 & 500f Supercaps because some research like the video below (at the 15m mark) led me to believe the chemistries can compliment each other in these high current applications buffering the alternator and the AGM battery.

I don't think the guy in that video really knows what he's talking about.