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LifePo4 Starting battery for Diesel van
#1
I've got 3 Mercedes diesel vans. I've used Optima Yellow top batteries for years now, and I've managed to kill even them, draining them over multiple long weekends. I must have had some high drain devices in them at times

I'm looking at the HEADWAY 200A cells from batteryhookup. First thoughts are a 4S4P pack to start.

With a 750 CCA I'm thinking a BMS to handle that might be out of budget, (and perhaps not available?) - does the starter have to draw through the BMS? I am sure I can separate the cable to the starter and have it direct to the batteries and the alternator and rest of the vehicle through the BMS.

So...
Where do I get empty battery shells, particularly one that I can have multiple terminals?
What would you recommend and where do I get a suitable BMS?
If I want to increase the capacity beyond a 4P pack, is there a more economical cell for the job?
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#2
In a car its more likely just to have a bms with reporting and balancing. Cutoff is not doable and not used
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#3
For high current wouldn't you just need a high current contactor that the bms can control? If you go lifepo don't forget to make sure that the alternator is setup for charging lifepo. The lithium cells can potentially pull a ton of current that can burn up the alternator.
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#4
Quote:For high current wouldn't you just need a high current contactor that the bms can control?
I assume you mean for the starter - Do you mean like a heavy duty relay? How would the BMS control that?


Quote:If you go lifepo don't forget to make sure that the alternator is setup for charging lifepo.
Isn't that what the BMS is for? What would I need to change?

Quote:The lithium cells can potentially pull a ton of current that can burn up the alternator.
Again - Isn't that what the BMS is for? What am I missing?
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#5
(04-01-2020, 06:56 AM)Wayne\s World Wrote:
Quote:For high current wouldn't you just need a high current contactor that the bms can control?
I assume you mean for the starter - Do you mean like a heavy duty relay? How would the BMS control that?


Quote:If you go lifepo don't forget to make sure that the alternator is setup for charging lifepo.
Isn't that what the BMS is for? What would I need to change?

Quote:The lithium cells can potentially pull a ton of current that can burn up the alternator.
Again - Isn't that what the BMS is for? What am I missing?
Regular lead acid car batteries have higher internal impedance so an alternator only pumps so much current into them.
A Lithium battery has quite low internal impedance & it's terminal voltage holds firm when charging vs rising like the LA.

An alternator is a constant voltage device & most don't current limit well, hence the rock & a hard place burn up result. 

Starter currents are huge (hundreds of amps turning & peaks > 1,000A) & you need a seriously big contactor (big relay) or things will melt.

Because a lithium battery can deliver more current you may have issues with starter motor as well.

A BMS's function may include high & low voltage cut off (which you would re-direct to controlling the contactor) but a BMS won't reduce current in/out of the battery, eg reduce alternator's charging current. 

You can get commercially available lithium batteries intended for automotive use, yes they cost $ but they might a be a better bet.
Running off solar, DIY & electronics fan :-)
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#6
They do make starter BMS for lifepo4 chemistry , check out Ebay

https://www.ebay.com/itm/4S-100A-200A-30...V04tkRSR8A

https://www.ebay.com/itm/12V-14-6V-4S-15...7E0Q1wQQHw

Depending on how big the motor is and how many CCA you need , these are something to look at .

The headway cells will work for a while , but there isn't any reserve capacity and there is a 85 amp charge max (4S1P ) configuration .
Any max usage on lifepo4 cells do not hold up for long. I limit 50% usage of stated limits of the cells.
You need a BMS because lifepo4 cells will die if they are discharged  or charged too far.

I use LTO cells . They are alot more tolerant to abuse and have more available CCA's per AH capacity. They also have a flatter discharge
curve for starting.

I have a 6S1P 30AH LTO battery with grade A cells in it. The CCA's are 1000A . I have it in a 2014 F-150 with a 5L v8. I tested at 14.4v charge with all the lights , heater blower and radio on . I stopped the test (45 minutes ) at 10.5 volts and it still started the motor. I did this at 25C degrees.
I have had the battery in the truck for about 2 years and had zero problems

I also have another test battery 30AH with grade C cells ,my first buy , two of the cells had a self discharge of 50% at a months time.
 This one is on a 8L diesel farm tractor and gets started 3 times a day with the occasional left the lights on till 0V battery.
After 2.5 years on 1 of the self discharge cells is down to @ 50% capacity , but still starts  the tractor. It will be replaced with a 40AH one with 1600 CCA so there isn't any future problems

None of these batteries have a BMS , but they have a active battery cell equalizer. At a 6S1P configuration the max volt is 16.2 and the charging system is max 14.8 to 14.7 volts . i have zero problems with alternators  . The truck has a 100 amp(140K miles) one and the tractor has 35 amp at 20 years old .

Right now I am putting together a group 65 aluminum case battery with 40AH cells at 1600 CCA.


Please forgive my lack of grammar , Because I don't a have a grammar checker yet

Jim
jr.
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#7
Interesting stuff Jim. I have not heard of LTO cells. I'll do some research. What's your locale - I'm guessing not Australia?
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#8
(04-02-2020, 07:34 AM)Wayne\s World Wrote: Interesting stuff Jim. I have not heard of LTO cells. I'll do some research. What's your locale - I'm guessing not Australia?


Hello :


BaronVonChickenPants my have some cells left

Ohio location

JimJr
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