Dual Batteries with Lithium - a cryptozoological study

[CoyoteThistle]

Good discussion going here.

For those interested in a very comprehensive take on lithium house batteries and charging challenges in vehicles take a look here

Couple take home-messages from all my research: (1) there is certainly a lot of bad info out there on the interweb from so-called experts - beware, and (2) The "lithium" settings on a lot of gear out there are not really ideal for lithium - beware.

I am certainly no expert but I just did a pretty geeky and detailed write-up of the setup I'm just installing in my camper build thread for anyone interested in a different approach.

http://forum.expeditionportal.com/threads/168085-Pro-Rig-V2-0-Home-Built-Compact-Composite-Pop-up/page4

matt

 

[rlynch356]

While i love lithium for the weight savings - i'm really wondering if the trade-offs are worth it? I used early LiPo 12v batteries (Voltage Phreaks) in my autocross cars for the weight savings (which made it very worth while on a # vs $ perspective) but for an overland truck, does it make sense?
You have increased fire risk, charging difficulties (unless that has been solved which i think for the aftermarket Alternator market is not), massively increased cost vs agm or (gasp) flooded cell batteries.....

I guess its all what you want to do.. for me (in this) is simplicity, reliability, and replaceability.. I don't see Lithium giving that.

My 2 cents....

 

[LeishaShannon]

You have increased fire risk, charging difficulties (unless that has been solved which i think for the aftermarket Alternator market is not), massively increased cost vs agm or (gasp) flooded cell batteries.....

There is no increased fire risk with LIFEPO4 (you can shoot the battery and it won't ignite, unlike other unrelated lipo chemistries you may be thinking of...)
Ideally you want to use a programmable charger so you can set the voltages to your specific battery (similar to charging a good AGM... you want to match exactly what the manufacturer recommends.) If using an alternator simply use a programmable relay to disconnect the battery at 13.8v , its then fully charged. There is no need for complicated multistage charging with lithium. Simple on/off is fine.
They're much cheaper than AGM when you consider cycle life


Lets compare a quality deep cycle AGM with Lithium:

Full River 12v 105ah deep cycle battery (DC105-12 ) $328USD https://www.civicsolar.com/product/fullriver-sealed-dc105-12-12v-105ah-agm-battery
67.0 lbs (30.4 kg)
900 cycles to 70% (which is exceptional for an AGM) = 66150Ah over the lifetime of the battery

$0.0049 per Ah

Winston 12v 90Ah $516USD http://www.evworks.com.au/winston-battery-lp12v90ah-lifepo4-cell-12v-90ah
33.7 lbs (15.3 kg)
5000 cycles to 70% = 315000Ah over the lifetime of the battery

$0.0016 per Ah

Lithium is less than 3 times the price of AGM and half the weight.

Then you have other benefits such as:
Higher voltage (lithium doesn't drop below 13v unless you're really smashing it)
~1 Peukert factor
~99% charge efficiency
Low internal resistance (charge it as fast as you can up to 1C)
No long drawn out absorption charge phase - no wasting your solar input

When you consider the "Ah" sticker on a battery can't really be compared across chemistries you'll realise that Lithium is cheaper and better in a lot of use cases.

We've been travelling in our electric only camper (Air con, induction cooking, electric HWS) for 2 years full time and the batteries still provide more than the rated energy on the sticker... :Wow1:

 

[Hillbilly Heaven]

I know the built in BMS handles the cell balancing required. Once the battery is fully charge do I have to wait till after cell balancing to use the battery?

The Winston battery listed is not available here in the states and does not include a BMS. A BMS would add an additional $150-$450 depending on how advance you wanted to get.

 

[CoyoteThistle]

Here's a calculation based on recent prices/availability in the US:

I just bought four CALB 100AH cells with BMS and Cell balancers for $653.

Rated at 4,000 cycles at 80% discharge = 320,000Ah over the life of the battery

$0.0020 per Ah

Still lots of reasons not to use lithium, but cost, factored over the long term at least, isn't really one.

The balancing process does not interfere with use of the battery and is occurring during the very end of the charge process as the battery nears 100% state of charge (at least with typical BMS/balancing systems).

 

[LeishaShannon]

I know the built in BMS handles the cell balancing required. Once the battery is fully charge do I have to wait till after cell balancing to use the battery?

The Winston battery listed is not available here in the states and does not include a BMS. A BMS would add an additional $150-$450 depending on how advance you wanted to get.

Its true Lithium cells are not self balancing , which also means they're not self unbalancing
I have found if you balance the cells initially and keep the charge/discharge voltages sane, you do not require balancing (I haven't re-balanced mine and they're almost 3 years old now with 2 years of daily use and are in perfect balance)

Where you -might- need a BMS is if you're using chargers designed for AGM charging and you're pushing the voltages way above what they should be. I have seen 0 balance issues with batteries charged to 3.45vpc (13.8v nominal)

 

[dwh]

Wooo...

https://news.utexas.edu/2017/02/28/goodenough-introduces-new-battery-technology

 

[Wyuna]

Wooo...

https://news.utexas.edu/2017/02/28/goodenough-introduces-new-battery-technology

Interesting,

In the next 10 years i really think we will see some huge advances on battery storage, increasing battery energy density will be one of them.

Then we will spend the next 10 years debating on how best to look after them :coffeedrink:

 

[Rando]

I am curious what those with LiFePO4 packs are doing about the cold temperature charging limitations? I have a DIY CALB pack sitting on the shelf, but have not installed it as I can't figure out a good way to avoid charging it when temperatures are below 0C. Not an issue for those in Brisbane and Arizona, but an issue for those of us in the Rockies.

 

[CoyoteThistle]

I am curious what those with LiFePO4 packs are doing about the cold temperature charging limitations? I have a DIY CALB pack sitting on the shelf, but have not installed it as I can't figure out a good way to avoid charging it when temperatures are below 0C. Not an issue for those in Brisbane and Arizona, but an issue for those of us in the Rockies.

For some this is a good reason to not go LiFePO4 but for most there are ways around it.

One little detail to clarify, it's the temperature of the battery, not necessarily the air, that is the important factor. When the electrolyte in the battery gets close to 0*C, that's when you mustn't charge (discharge okay down to -20*C they say). There are BMS systems that include cell temp monitoring - I don't know much about these, but it's probably the best way to not damage your battery if temps are really low. Even with protection, you should design your system to try to keep the battery as warm as possible when the air temperature drops.

Few ways to do this depending on when and how you charge and how low air temps get. Most people mount their battery inside their camper (a little greenhouse effect from windows or running the heater). I saw someone mount the battery in the cab of their truck - should stay above freezing in there while driving (and charging off the alternator). If it's cold and sunny and charging off solar, cab of the truck probably stays above freezing until it's pretty darn cold out (greenhouse effect).

I mounted my battery close to my water tank - the thermal mass of the water may keep things a little bit warmer. Some use a heater in their battery compartment - if it's a small space, something that puts out maybe 100watts might do it - this of course decreases your charging efficiency (not a problem for an alternator).

 

[grizzlyj]

Hi

LED lights are quoted as having a huge (average?) lifespan, but since I've changed over nearly all household bulbs to LED quite a few have popped. Maybe more often than before.

Similarly, if you work out lithium costs based on quoted lifespan, they come out cheaply. But unlike lead acid etc, have batteries with current lithium tech actually been around long enough for those lifespans to be proven?

Just wondering, and something I'm ignoring anyway

 

[CoyoteThistle]

Good points and good questions grizzly.

I think dropping lithium batteries in to charging systems set up for lead acid is going to lead to significantly shorter life spans. Already lots of complaints out there about capacity dropping off after just a few years of use. Float charging is slow death to lithium but most people are still doing it.

On the other hand, folks setting up good BMS's and charging correctly are still getting full rated Ah (or more) after many hundreds of cycles.

Then again, how many of us are going to put thousands of cycles on our batteries? Maybe if you live full time in your rig off grid. I might put 50 cycles a year on mine - I should be good until I'm too old to drive :elkgrin:

 

[mathews]

Lithium batteris are better than the AGM batteies because they are light in weight and aslo price is less.
Therse is a charging problems with the lithium ion batteires.

We need a programmble charger, so we can adjust the charger according to the sepcification of the battery.

Due to overcharging or charging with another charger causes explosion of lithium batteries.

 

[mathews]

Ok ... I'm just spitballing an idea because recently I ran across this issue with a Segway that was given to me ... (yes, I said Segway. It's an old E model - the big one with saddle bags, etc)

If you check out the cost of the parts for a charging system from a Segway you will find a very compact and sophisticated charging algorithm is used. I was a little surprised when I found out how it charges (I guess I shouldn't have been - the batteries are $900 each and it requires 2 of them) You might want to e-mail Segway and see if the parts can be obtained to use for your purposes.

New models of segway coming up with UL certified lithium batteries. These segways can be charge easily and all faults with the old segways are resolved.

New hoverboard reviews are good.

Charging issue is also resolved.

 

[witt]

I know this is a pretty old thread, but I thought I'd share my experience in case it's helpful to others...

I installed a 100AH LIon battery (from smartbattery.com) in my RV alongside the vehicle's two stock lead acid starting batteries. The house battery is separated using a standard dual battery isolator system. I have a 100W solar panel which charges all three batteries when the isolator is "connected" and just the house battery when it's disconnected.

I've run this setup for the past five years, with half of that living in the van full time during a trip through the Americas. During that trip, the battery performed great, and had no problem starting and running our diesel cooktop and heater (which take quite a bit of juice to get going). Depending on the amount of sun and how much we used our computer and other devices, the battery would last us about three days while parked.

About six months ago, the battery completely died. After charging it will indicate 13.3V, but on connecting a load it will shut itself off almost immediately.

The battery came with a five year warranty, and it was supposed to have 80% of its capacity left after that time. I've been trying without success to get a warranty repair from smartbattery.com for the past four months. They will answer my phone calls, but never respond to emails or voice mails. They have not explicitly stated that they won't honor their warranty, but I've pretty much given up on them.

I love the light weight and compact nature of lithium ion, especially in comparison with the 100AH deep cycle lead acid battery I've temporarily replaced it with. I will probably end out buying another LIon battery, but not from the same company.