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bdosborn

Colorado

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Posted: 04/21/20 03:50pm Link  |  Quote  |  Print  |  Notify Moderator

They have bigger protectors, up to 220A. Victron Linky

My battery has a 2C discharge rate. I have them in a 2p4s arrangement so I have 360A of discharge current available. One of the nicest things about LiFePo4 batteries is there's no Puekert effect, the voltage stays fairly constant, even with large loads. My inverter is only 300W. I'm not a full timer so I don't run any large inverter loads. I want the capacity for the electric fridge.

Another often overlooked feature of LiFePO4 is their low internal resistance, which means they are 99% efficient when charging versus ~85% for lead acid.

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time2roll

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Posted: 04/21/20 04:03pm Link  |  Quote  |  Print  |  Notify Moderator

01tundra wrote:

We are running a PD4655L Wildkat converter set to the li setting.

It charges at a constant 14.6V until our single 100AH BattleBorn battery reaches 100% SOC. It starts out pushing 55 amps and then tapers off as the SOC gets higher, once the battery reaches 100% SOC the amperage tapers of to almost zero (usually around 0.25A or so).

I let it sit disconnected from the converter somewhere around 70-80% SOC and then charge it before we leave for the next trip, it charges so fast that it's no issue at all.
If plugged in running the air conditioner do you disconnect the battery or let it float at 14.6 for the full week?


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BFL13

Victoria, BC

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Posted: 04/21/20 04:10pm Link  |  Quote  |  Print  |  Notify Moderator

Very neat, thanks for sharing!

Any info on the BMS you chose and settings? Not clear on what it does compared with what the Victron protector does for operation and protection. Does it have a minimum voltage to activate it like Battle Born's ISTR 14.1?

Battle Born says they have a Peukert factor, I will edit that here later. Mobilesport and Itenerant1 both noted their banks do warm up under a recharge, so there must be some charging inefficiency. ISTR Trimetric has an Li setting for that too. Not as much as lead-acid though.

EDIT--BB says, "The Peukert exponent refers to the “shrink rate” of your battery bank. The more rapidly you discharge the batteries, the more their effective size shrinks. For example, a battery that can supply 200Ah when discharged over twenty hours may only provide 95Ah if discharged in one hour.

We recommend a Peukert compensation to be set at 1.05 for the best results."


(Haven't read that link on DIY Li yet)

* This post was edited 04/21/20 04:19pm by BFL13 *


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Itinerant1

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Posted: 04/21/20 04:33pm Link  |  Quote  |  Print  |  Notify Moderator

Warming up 5-10f degrees you wouldn't even notice if it wasn't for the individual cell temp sensors.

Unlike lead that you need to hammer them with high voltage occasionally for de-sulfation/ full. Lifepo4 is more forgiving for charging to reach the end users good enough full or what is needed for balancing/ capacity resetting. Mine have not seen higher than 14.2v in their 4 years with 11 months of a year using 14.1v as the bulk/ absorb setting.


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pianotuna

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Posted: 04/21/20 05:09pm Link  |  Quote  |  Print  |  Notify Moderator

Itinerent1,

Any signs of aging at all?


Regards, Don
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Itinerant1

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Posted: 04/21/20 05:53pm Link  |  Quote  |  Print  |  Notify Moderator

None that I can tell from everyday use, looking back at prior years notes and roughly same loads at low or high SOC's everything appears to be the same. I would think that it would show when using the microwave with other loads at the same time (fridge, humidifier, chargers, tv) 140-185 amp loads. If age was showing voltage would be lower now than when the cells were new and the are still the same.

BFL13

Victoria, BC

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Posted: 04/21/20 06:26pm Link  |  Quote  |  Print  |  Notify Moderator

Itinerant1 wrote:

None that I can tell from everyday use, looking back at prior years notes and roughly same loads at low or high SOC's everything appears to be the same. I would think that it would show when using the microwave with other loads at the same time (fridge, humidifier, chargers, tv) 140-185 amp loads. If age was showing voltage would be lower now than when the cells were new and the are still the same.


IIRC, Li age by shedding material. Does that show as a gradual loss of capacity like sulphation does with lead-acid batts? Or does it just mean the batts fail suddenly at some point more like with lead acid and shedding of the positive plate?

With such low R for Li so the voltage sag under load is so much less, would you really notice any difference in loaded voltage for a 150a load between a 500AH bank of Li and a 400AH bank at 70% SOC in each case?

I am thinking (don't know) if the loaded voltage on the 500AH bank at 70% is the same as when the bank is at 50%, then there would not be any difference between the 500AH bank at 70% from the 400AH bank at 70%.

Perhaps a better way to tell loss of capacity is to time the drop in monitored SOC using the same load in each test.

Just speculating here. Not a clue what is correct.

Itinerant1

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Posted: 04/21/20 07:35pm Link  |  Quote  |  Print  |  Notify Moderator

These are sorted from the largest discharge loads to give you an example. Looking to the left of the discharge column will be the pack voltage then the SOC%.

[image][image][image]

pianotuna

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Posted: 04/21/20 08:26pm Link  |  Quote  |  Print  |  Notify Moderator

Itinerant1,

Fantastic numbers. ty for taking the time to share them.

BFL13

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Posted: 04/21/20 08:39pm Link  |  Quote  |  Print  |  Notify Moderator

I find it hard to interpret the voltage drop vs SOC with the solar on supporting the voltage at times.

Perhaps Itinerant1 could walk us through it?

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