Testing an Aux batt solution...

[HammaMan]

Thats nice. No wonder you are having such good luck with the LEP battery then. Fan 5 is great for keeping the voltage up, But still won't charge the AGM if there isn't any amperage behind it. I'm not finding any patterns with the cold weather like I could in the warm. I'm not sure what the truck is looking for but it seems the rules change every week lol!

During the warm months the truck will NEVER charge the AGM unless the voltage is 12.49 or less at startup. I have hundreds of captures showing this.

Now that its cold, Sometimes its 12.29, 12.39, it varies.

All this at fan setting 5.

I ordered a DiamondBack HD cover the other day. Really tempted on putting a flexible solar charger on it. I'm always parked in the sun when its out.

I wish there were some variables we could change.

So very frustrating.

There's plenty of 'amperage' present. AGM just needs much higher charging voltage. LFP doesn't. Cell chemistries are different. A 1 volt difference on LFP can see even a 'small' battery draw 100+ amps, AGM won't even do that at 2 volts difference. It has to do with the internal resistance of the batt. The way the LFP is able to charge up the AGM is that it's always there at higher voltage and over time it the AGM will eventually charge. The LFP will just soak up energy like crazy compared to AGM which is why it makes it a great choice for short trips. It'll take loads of ah in short order and then charge up the AGM. However once the AGM is at 100%, outside of starting, the LFP is providing all of the reserve capacity.

A single 10 minute trip a day is enough to keep the pair of batts fully charged. Not at 70% or 80% SOC, 100%

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[ReverendQ]

Hey @HammaMan , I was considering adding a second FoMoCo auxiliary battery in parallel to the first to double the power available for accessories as I add them to my 302A PB. After reading this, it appears that you would advise adding the LPO at much more available current (total and faster). Please verify swapping out the current auxiliary FoMoCo 7.5Ah AGM for the 30Ah LPO is all that is needed to add the extra available auxiliary power and that the PB systems, including powering, starting and charging need no other modification. TIA

 

[HammaMan]

Truck sat for 2 weeks with the 30ah LFP in it. Voltage after the 1/29 run was 13.3v, today before taking it on a quick trip to the post office was 12.8v.

~15m of remote start followed by a ~11 minute trip

After 11 minutes of charging it's back up to a 13.2v resting voltage (disregard that state of charge meter, it has no idea how much energy is in the batt)

 

[HammaMan]

I've kept the test going on the little 30ah aux batt, no additional charging just a handful of short 15 minute trips. The option is to select 15 days, but I chose 14 days as it's easier to sort so the end of 1 chart is also the first day of the next one. The "dip" seen is the remote start where it starts to consume the batts until the fan 5 trick is enabled w/ fob in the truck. Some of the random dips are OTAs or a lock command. Both use ~8amps of current for the systems it wakes up before going back to sleep.

on 2/25 that was a trip to the store, left the truck on while in the store, took fob with me for so it'd still be there when I came out.

 

[LouDog]

wow. I would like to do this. Do you still think it's not wise for a laymen like myself?

 

[notabot]

8 amps? Yikes!

 

[HammaMan]

8 amps? Yikes!

It falls back off pretty quick as it sleeps the various computer modules. Somewhere I've documented the total energy usage for each 'action'. A simple remote lock command will eat about .5ah of capacity.

 

[Jmitchelltfo]

@HammaMan

I’ve gotten my first low battery warning so I’m shopping for an auxiliary replacement right now. If I want to set it and forget it, with an occasional hookup to a battery tender would you recommend the LFP option?

I noticed that 30ah battery you bought is out of stock, but they have a 20h available.

Would you recommend this battery/charger as a replacement?

If I go with another AGM, I was looking at this one since it has such good reviews.

Weize YTX14AH-BS High Performance - Maintenance Free-Sealed AGM ATV Motorcycle Battery for Polaris Sportsman 570 Trail Blazer 250 Ranger 400 500 Suzuki King Quad 300 QuadRunner 250 https://www.amazon.com/dp/B07VWVTL1V?psc=1&ref_=cm_sw_r_apin_ct_NQWS589X8C96SV01932J&language=en_US

 

[HammaMan]

I'm cautious to recommend an LFP aux to anyone straight up. When they're charged below freezing, it can impact their lifespan. Traditional testing methodologies in a lab are always done on full discharges, and in as few as 100 full depth discharge/recharge cycles below freezing, reduced capacity can be seen. There are much larger batteries with far better BMSs that can heat the battery and maintain strict temperature/charge rates to keep the battery's life in-tact, which to be clear is often measured in decades. Sans those features someone in the northern latitudes may only get 3 years of life out of the aux batt whereas those of us in the south will likely never need to replace it.

As for a charging it, well once the battery is balanced, something you'll need a benchtop power supply to do, fan 5 will keep it ~97% fully charged. At the same time, below fan 5 you're not charging it. Some people don't want to deal with such things. It's not to say that normal operation not using fan 5 won't keep juice in it, it's a different chemistry and sub 13v the truck will otherwise feed it leaves it less than fully charged. For some that's not really a big deal as it's still got plenty of reserve capacity left in it. I haven't left it alone to see what the truck will do to the system otherwise as it will bump up voltage when it thinks it needs to charge the batteries. I don't drive it daily to track such things. I use it every 10-14 days on average and it's happy, that's all that matters to me.

 

[Snakebitten]

HammaMan is stand-up for not recommending. And he explains why he takes that stance.

But I read between the lines and chose to see for myself how my 2022 Powerboost, with the original factory AGM under the hood and back seat, would respond to the auxiliary battery swap.
I purchased the cheap 25AH LFP from Amazon. And I did spend 3 nights balancing the cells in that battery since just as HammaMan predicted, it arrived way out of balance!

Note that I live on the Gulf Coast and will rarely have a frozen auxiliary LFP in the cab of the Powerboost. But I don't think I will ever be going back to the little baby AGM in this truck. For ME the LFP Auxiliary is the answer to keeping the resting voltage on this truck far above the danger zone. No more 12.1-12.3V at 4am. Instead, the little LFP props the battery bank up to 13-13.2V

I say battery bank since while parked, the isolator is not engaged, so the LV buss sees the voltage that both batteries supply in series. I could be wrong about the vernacular, but I think it's clear what I mean to convey.

As for the expected lifespan of the LFP?
I don't have a clue what to expect.
But for ~$50, I'm more than willing to find out.

 

[Jmitchelltfo]

I'm cautious to recommend an LFP aux to anyone straight up. When they're charged below freezing, it can impact their lifespan. Traditional testing methodologies in a lab are always done on full discharges, and in as few as 100 full depth discharge/recharge cycles below freezing, reduced capacity can be seen. There are much larger batteries with far better BMSs that can heat the battery and maintain strict temperature/charge rates to keep the battery's life in-tact, which to be clear is often measured in decades. Sans those features someone in the northern latitudes may only get 3 years of life out of the aux batt whereas those of us in the south will likely never need to replace it.

As for a charging it, well once the battery is balanced, something you'll need a benchtop power supply to do, fan 5 will keep it ~97% fully charged. At the same time, below fan 5 you're not charging it. Some people don't want to deal with such things. It's not to say that normal operation not using fan 5 won't keep juice in it, it's a different chemistry and sub 13v the truck will otherwise feed it leaves it less than fully charged. For some that's not really a big deal as it's still got plenty of reserve capacity left in it. I haven't left it alone to see what the truck will do to the system otherwise as it will bump up voltage when it thinks it needs to charge the batteries. I don't drive it daily to track such things. I use it every 10-14 days on average and it's happy, that's all that matters to me.

If I supply a little background maybe you’d be more inclined to make a recommendation one way or the other.

I always run my fan on 5 or higher, battery and climate control advantages mean that level 4 doesn’t get used in my pickup.

I live in the Ozarks, so our winters are mild. We rarely see temps below freezing for more than a week or two at a time. I’m not concerned about cutting a $60 battery slightly short of its lifespan. But if you think it would be a significant difference …….then AGM it is.

You talked about an advanced/better BMS…..if the cheap version on Amazon doesn’t fit the bill, would you recommend this one from batteries plus? I know it is pricey, but a 10 year free replacement means that I don’t need to worry about this issue even with my next powerboost.

https://www.batteriesplus.com/productdetails/slil12=20dcm=bt?variationCode=VI1387680

 

[Jmitchelltfo]

HammaMan is stand-up for not recommending. And he explains why he takes that stance.

But I read between the lines and chose to see for myself how my 2022 Powerboost, with the original factory AGM under the hood and back seat, would respond to the auxiliary battery swap.
I purchased the cheap 25AH LFP from Amazon. And I did spend 3 nights balancing the cells in that battery since just as HammaMan predicted, it arrived way out of balance!

Note that I live on the Gulf Coast and will rarely have a frozen auxiliary LFP in the cab of the Powerboost. But I don't think I will ever be going back to the little baby AGM in this truck. For ME the LFP Auxiliary is the answer to keeping the resting voltage on this truck far above the danger zone. No more 12.1-12.3V at 4am. Instead, the little LFP props the battery bank up to 13-13.2V

I say battery bank since while parked, the isolator is not engaged, so the LV buss sees the voltage that both batteries supply in series. I could be wrong about the vernacular, but I think it's clear what I mean to convey.

As for the expected lifespan of the LFP?
I don't have a clue what to expect.
But for ~$50, I'm more than willing to find out.

Thanks for your insight! I definitely live further north than you, but probably not far enough to worry about issues with an LFP.

I will call the batteries plus store 30 minutes down the road and see if they have the 20ah LFP in stock. A 10 year free replacement warranty would be something I’ve never had on a battery before. I’m tempted to try it out based on the awesome warranty.

 

[Snakebitten]

For full disclosure, I bought this one

And I also needed one of those bench/lab chargers/power supplies.
(which I had to learn how to use properly to balance that Chinese battery)

 

[Snakebitten]

I have the Bluetooth voltometer on my Powerboost.
I have been monitoring the 24/7 voltage on this truck for many months. Especially when I let the truck sit for days at a time.

Once I swapped for the little LFP Auxiliary, everything changed. ?
Note that the underhood battery is 1000 days old (original factory)

Here's 5 days of the truck sitting

 

[Jmitchelltfo]

I have the Bluetooth voltometer on my Powerboost.
I have been monitoring the 24/7 voltage on this truck for many months. Especially when I let the truck sit for days at a time.

Once I swapped for the little LFP Auxiliary, everything changed. ?
Note that the underhood battery is 1000 days old (original factory)

Here's 5 days of the truck sitting

I was planning to swap both batteries at the same time, but I might just go your route and replace the auxiliary. No low voltage warnings this morning. I also ordered the Bluetooth monitor so I can keep track of my 12v system too. I just hope the battery tray is able to fit the wider X2 design. If the dremel or small amount of cutting is needed, I’d be ok with that.

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