OVERTHUNK — AUX LiFePO4 100Ah battery

[82SC]

Here is a quick teaser shot.
Still working through the next steps.
Yes I know about the issues with running Li in hot and cold environments. The Aussies have had good success running them though.

Main issue with trying this is fitting a 100Ah battery in the tight space and I think I found the right combination.

A sharp eye may notice the scorch mark on the negative terminal. So…yes I can confirm the battery battery tie down bar does conduct electricity….

 

[zoned]

What did you do with the little doodad that sits in that spot?

 

[adashoe]

Here is a quick teaser shot.
Still working through the next steps.
Yes I know about the issues with running Li in hot and cold environments. The Aussies have had good success running them though.

Main issue with trying this is fitting a 100Ah battery in the tight space and I think I found the right combination.

View attachment 3100562

A sharp eye may notice the scorch mark on the negative terminal. So…yes I can confirm the battery battery tie down bar does conduct electricity….

The Aussies have Lipo batteries which are tested for use in engine bays, like the DCS batteries that have inbuild BMSs

 

[TeCKis300]

Kudos for the effort and it looks like you're doing some good work there. Not to take away from that, I'll still tell it straight.

This is arguable whether locating LiFePO4s underhood is a good idea. It will be weather and use case dependent. For someone that lives in hot regions and tends to do lots of low speed crawling over hours, I would advise against such chemistries under the hood. BMS or not, the hot environment would cause premature failure of the battery, all the way into potential fire risks.



This has also been true for AGM batteries like I've been saying for years that many now have experienced first hand. Sure, they might last 2-3 yrs, but that's surely not getting the value out of a premium battery.




That said, I think the forward location of the battery in the cruiser can help. Perhaps with a heat shield against the engine side, could make a difference.

 

[82SC]

Yeah this is all great info and I'm learning as I go.

So I am no expert but I am compiling info and I am always willing to try things out and do a little experimentation.




(Edit) I've seen numbers ranging from -30C to 110C
All of them vary, but those are the extremes.

Some BMS have low and high temp cutoff control in their BMS
Ideally I wanted a battery that has this built in but space constraints limited my option.
There are addon BMS that I am researching as well.

AGM is a tried and true setup.
I don't need to repeat all the advantages of AGM vs Li but the ones that affected me the most
Space to Amp hour ratio -- Li can be discharged 80%-90% of the rated Ah. AGM is ~50% so much less usable Ah for the given space
Full discharge damages AGM, less so for Li. (yes the heat/cold damage may offset this but is an unknown at this time)
Price of Li has been going down down. I know cheapo batteries come with their issues too but I think there is a balance for bang for your buck.
Also only accessories will be wired to this battery. Nothing essential so if things cut off it won't affect function.


This is a very elementary video. Would be better to get actual battery temp rather then air temps but gives at least a starting point



This one is a pretty good overall video too.



And here is some counterargument to it
Is It Safe To Put A Lithium Battery Under The Hood? We Test & Find Out! - https://www.youtube.com/watch?v=evghqj3SWPE

Couple thoughts....that rear location is probably the worst place in the engine bay
The LC location is near the radiator but also has much better ventilation

 

[tbisaacs]

I came really close to mounting under hood but as others pointed out I was really worried about thermal cutoff and longevity. Also if you mount battery inside you can use Victron DC/DC which IMO is far superior to the Redarc BCDC, with exception of being able to mount in engine bay.

 

[82SC]

The Aussies have Lipo batteries which are tested for use in engine bays, like the DCS batteries that have inbuild BMSs

Yeah I noticed alot of the Aussies use DCS, but I don't see anything specific in their documentation about okay for engine bay usage and their specs are similar to other Li batteries. One video did mention that DCS used "high temp insulation and glue" when assembling their batteries but haven't seen that in writing too.

iTech seems to be the only one actually mentioning engine bay usage.

 

[Sandroad]

I have no experience with LiFePO4 batteries in a vehicle, but I have lots of experience with them in RVs and solar installations.

First, you have the temperature range way wrong. Most 100Ah LiFePO4 batteries have an operation (charging-discharging) range of 0 degrees to 57 degree C or 32 degrees to 135 degrees F. As the temperatures get toward those extremes, the battery does not perform well and extended use at the extremes will damage it. Underhood temperatures will get beyond those extremes, at least where I live.

Second, I personally would never install a LiFePO4 battery without a factory installed battery management system built in. Way too much danger of damage or destruction.

 

[82SC]

Oh forgot this video too. I like this guy....

 

[TeCKis300]

This is a very elementary video. Would be better to get actual battery temp rather then air temps but gives at least a starting point

I thought it funny that this guy would conclude that all is good and well, based on a 75°C ambient temp. As your in LA, here in the southwest, ambient temps in the summer can easily be 105°F. So add a 30°F delta to his max temp results.

In the more interesting places in the desert, it's easy to go beyond that still. I can regularly see 160°F+ in off-road crawling in the engine bay area, from the intake air temps, which draws air very near where that battery is.

 

[TeCKis300]

I came really close to mounting under hood but as others pointed out I was really worried about thermal cutoff and longevity. Also if you mount battery inside you can use Victron DC/DC which IMO is far superior to the Redarc BCDC, with exception of being able to mount in engine bay.

I'm still working on details, and this may or may not be interesting. Lithiums have little to no need for complex multi-stage charging. They really only care about top end voltage. Even that to a degree is not a big deal as most have internal BMSs limiting top out voltage.

I was going down the path of Victron, and even their non-smart DC-DC converters can work.

Experimenting with a simple buck/boost converter. A LiFePO4 setup for around $400. More to come...

 

[82SC]

I have no experience with LiFePO4 batteries in a vehicle, but I have lots of experience with them in RVs and solar installations.

First, you have the temperature range way wrong. Most 100Ah LiFePO4 batteries have an operation (charging-discharging) range of 0 degrees to 57 degree C or 32 degrees to 135 degrees F. As the temperatures get toward those extremes, the battery does not perform well and extended use at the extremes will damage it. Underhood temperatures will get beyond those extremes, at least where I live.

Second, I personally would never install a LiFePO4 battery without a factory installed battery management system built in. Way too much danger of damage or destruction.

Sorry I think I mixed up some of the numbers but here is what I've seen

dcs says -30 to 110 C
Itech says -40 to 80C
eco worthy says -4 to 140F
Battle born says -4 to 135F

And these are operating temps not optimal temp.
Think they are saying the battery can still function at these extremes. But as people have mentioned that it will damage the batteries if you do so.

 

[Sandroad]

Sorry I think I mixed up some of the numbers but here is what I've seen

dcs says -30 to 110 C
Itech says -40 to 80C
eco worthy says -4 to 140F
Battle born says -4 to 135F

And these are operating temps not optimal temp.
Think they are saying the battery can still function at these extremes. But as people have mentioned that it will damage the batteries if you do so.

The extreme temps listed for the first 2 are for operation of the electronics in the BMS, not the operation of the battery, which are very different and similar to other LiFePO4 batteries. In the second 2, the low temperature listed is for the ability to discharge, not charge. With some limited exceptions, almost all LiFePO4 batteries cannot be charged below freezing (0C or 32F) unless they have built-in heaters.

 

[82SC]

Good info.

I hope to find a solution where I can have a Li battery with temp protection to cut off charging and discharge when too hot or cold.
Minimize battery degradation
But at the cost they are running now, I do want to get as much Ah per dollar and Li seems to be winning there.

Lot of good real world experiences with similar setups rather then pouring over numbers and hypotheticals.

It is for accessories so nothing essential will run off of them.
Back up to jump the starter if needed
And possible battery link if I ever get a winch.

In a cold environment I doubt I will ever be running battery in or out with the engine stone cold and off
In a hot environment I will likely be only running the battery in or out with the car moving with at least some airflow

I think the conditions that I need to really think about is the slow rock crawling mentioned above
And if I ever decide to get a winch. There are videos of guys running dual Li setups and winching.......which I don't know enough about yet

 

[tbisaacs]

And if I ever decide to get a winch. There are videos of guys running dual Li setups and winching.......which I don't know enough about yet

I dont think LI is great for winching application simply due to their limits on discharge current. BattleBorn is super premium and it's only 200amps for 30 seconds.

 

[82SC]

Geez this info is so varied all over the internet
His engine isn’t even running

 

[bigboo]

I tried a Gravity Zero battery in my DR650 and ran into too many problems. I just couldnt trust to start the bike in the morning.

 

[stonepa]

Geez this info is so varied all over the internet
His engine isn’t even running

Probably couldn’t hear him talking if that agricultural diesel was running.

 

[linuxgod]

Good info.

I hope to find a solution where I can have a Li battery with temp protection to cut off charging and discharge when too hot or cold.
Minimize battery degradation
But at the cost they are running now, I do want to get as much Ah per dollar and Li seems to be winning there.

Lot of good real world experiences with similar setups rather then pouring over numbers and hypotheticals.

It is for accessories so nothing essential will run off of them.
Back up to jump the starter if needed
And possible battery link if I ever get a winch.

In a cold environment I doubt I will ever be running battery in or out with the engine stone cold and off
In a hot environment I will likely be only running the battery in or out with the car moving with at least some airflow

I think the conditions that I need to really think about is the slow rock crawling mentioned above
And if I ever decide to get a winch. There are videos of guys running dual Li setups and winching.......which I don't know enough about yet

A good LiFePO4 will have temp protection. I built my own LFP battery for my trailer about 18 months ago and I used an Overkill (JBD) BMS. There are cheaper BMS options which are typically incorporated into the battery, but if it doesn't have its own protection then the battery is IMO garbage.

The BMS sits inline on the negative side of the battery. Most good BMS will have a ~120A discharge limit, give or take, and won't be suitable for winching. I've seen some higher discharge limits but they are via the crappier BMS options.

 

[linuxgod]

I have no experience with LiFePO4 batteries in a vehicle, but I have lots of experience with them in RVs and solar installations.

First, you have the temperature range way wrong. Most 100Ah LiFePO4 batteries have an operation (charging-discharging) range of 0 degrees to 57 degree C or 32 degrees to 135 degrees F. As the temperatures get toward those extremes, the battery does not perform well and extended use at the extremes will damage it. Underhood temperatures will get beyond those extremes, at least where I live.

Second, I personally would never install a LiFePO4 battery without a factory installed battery management system built in. Way too much danger of damage or destruction.

^ This. All of this.

This is an example of the cells I used. Every cell is different, but LFP chemistry is all the same so they're not THAT different. 60C (140F) is the limit but notice how above 45-50C the charge rate drops off precipitously. There's a window where LFP works well - about 20C to 45C - and a larger window where it's ok and outside that you're paying a lot of money for the wrong use case. LFP is good for running a fridge for a long time if you can reasonably control the battery temperature, but it's poor for vehicle starting or heavy loads like winching, especially when you can't control for the ambient temps

FWIW I don't think you have to worry about LFP catching on fire just sitting under the hood, but a high ambient temp plus a high charge current can absolutely cause the cells to swell and burst. Also if you charge an LFP below 0F you will almost certainly kill it after the first charge. Lots of lessons at Up in smoke... learn from my mistake! - https://diysolarforum.com/forums/up-in-smoke-learn-from-my-mistake.83/