Charging LiFePo4 batteries with AGM profiled chargers?

[damienperu]

Hi all,

I'm very close to the point of changing from an AGM bank to a single 200Ah lithium auxiliary battery, however the question is how much of my existing charging hardware will still work adequately?, and I think this will be question that many will be facing in the coming years. Anyone here have any experience or knowledge on charging them with devices designed for AGM?

I will be maintaining a Bosch S6 crank battery (or similar technology) for the high output winching ability and have the following chargers:
- 270amp alternator (SBC-T4.2-270XP) that outputs up to 15V, sits mostly around 14.6V so I'm much better from the outset than most standard alternators
- Xantrex TRUECHARGE2 10amp dual battery AC charger with selectable profiles (except for lithium)
- EP 20amp dual battery solar controller with an 'industrial' profile for charging at 14.6V with 30 mins boost at 14.8V

Of course some battery sellers that also sell dc-dc chargers say that devices with AGM charging profiles or straight from the alternator is incompatible with the constant 14.6V apparently required for lithium, and that all hell will break loose (including the warranty) if i don't use a dc-dc lithium profiled charger (limited to 40amps from what i've seen so far), but I'm sure the batteries are more resilient than that, and I've read that lithium actually accepts even higher amperage than AGM (like that a 200ah LiFePo4 will accept up to 500amps). Smart Battery actually told me the opposite in an unconvincing one-liner, that all my stuff would be fine. So just how inefficient and damaging will be charging a LiFePo4 with my high output alternator?, which varies from 14.2V (under massive load) to 15v (under no load).

There are two reasons i don't already have a dc-dc charger for my AGMs, the first - and the reason i got the high output alternator - was to not be limited by the dc-dc charger low amperage limitations, as i run a lot of 50amp gear and professional camera battery chargers via inverter whilst running. So the last thing i want to do is drain the battery whilst running the engine when i have an alternator perfectly capable of running everything as well as charging the battery. The second is emergency starting, I have a blue sea 500amp isolator that allows me to crank from the auxiliary in emergencies, a key feature for me as i usually run solo.

I guess i could just spend more money and setup a huge +250amp manual bypass relay for a dc-dc charger and manually flick a switch when wanting an emergency start or running a big load when driving, but if i can avoid having any of that extra complexity I'll be happy.

Any insight will be greatly appreciated.

Cheers,

 

[DiploStrat]

Hard to Say

Sounds like your alternator is similar to mine.

The first, obvious, thing is to check with the maker of your battery. That said, there are two downsides, that I know of, to lithium:

-- They don't like being charged when they are below freezing; a real issue on the Altiplano, and,

-- There are some rumors that the charging voltages may be as low as the 13v range. (http://www.technomadia.com/2012/09/a-year-on-lithium-rv-batteries/

The problem seems to be that there are simply not enough large lithium banks that have been out there long enough to collect meaningful data.

This is why I am still running AGM.

¡Buena suerte, chico!

See LeishaShannon's post, up next. The Sterling B2B (DC-DC) line may get a new lease on life with Lithium, but the question is whether their profiles are right, either.

 

[LeishaShannon]

My 2 cents...

The Chinese lithium market is like the wild west at the moment with manufacturers making all sorts of crazy claims to push product, which local resellers with little hands on experience then recite as gospel. A battery reseller only cares that your batteries last the period they're prepared to warranty the product for which is usually no more than a few years (and thats assuming the seller is still around....)

Personally I take a more cautious approach and use for 3.45vpc (27.6v on our battery) because on a properly balanced pack there will be little to no cell divergence at this level, and 98% full is good enough for me.

While they will accept high charge rates, .5C is probably the highest you'd want to charge at for longevity.

Lithium doesn't require complicated multistage charging like lead, so a simple on/off relay @ 13.8v is all thats required to get the battery to ~98%

I'm not familiar with your alternator but while it might be "rated" at 260A , it probably isn't designed for 100% duty cycle and will reduce output due to excess heat.
If it is able to deliver 260A continuously you then have the problem of only having a 200Ah battery so you'd be charging at close to 1C after the other vehicle loads...

Ideally you want an external regulator so you can dial in the voltage and current limit suitable for your batteries, but I'm not sure if your alternator supports that? if not a programmable (not lithium preset) DCDC charger would be the next best option. Sterling make some quite high capacity models.

 

[damienperu]

thanks for those replies... here's my alternator if you want to have a look, although the voltage specs are buried in the installation manual. The ratings are continuous. I can't imagine how a vehicle alternator rating could be anything else really.

http://www.m2kinc.com/detail-sbc-t4-2-270xp-25-40-38-2.html

i mostly got it for winching and to be able to run high loads while driving and still be charging the batteries.

I'll have a look at the sterling dc-dc chargers

 

[damienperu]

¡Buena suerte, chico!

gracias, lo necesito... my entire expo build journey so far has been an showpiece for Murphy's law!

yeah the maker of the battery i'm thinking of getting is one of those suggesting the 40amp dc-dc charger.

that link looks like a great read for this evening, thanks for that.

the cold thing is a bit worrying... you can see in the specs for these one's how from 25C to 0C you loose 20% capacity and 50% at -20. although my auxiliaries are located inside my truck where we sleep in cold weather, so even if i leave the truck abandoned, as long as i can start the car with teh non-lithium cranker its temperature should be above 10C most of the time... but you just triggered me to think of doing a bit of insulation in the battery box. https://www.victronenergy.com/upload/documents/Datasheet-12,8-Volt-lithium-iron-phosphate-batteries-EN.pdf

i know what you mean about waiting, i love embracing new technology but have been tossing and turning on lithium for well over a year now... if it wasn't many thousands of dollars per battery i would have changed over a year ago and would just apply trial and error to sorting the charging process, but it seems foolish to dump a ton of cash with so few testimonies out there when you already have an AGM system working well. SPEAK UP YOU BRAVE LITHIUM USERS!!!

 

[damienperu]

My 2 cents....

I'd say a good few dollars at least! thanks!

i had a quick look at the sterlings, and among the myriad of products this caught my eye... this link says it has a 180amp model, but i could only find buying options for the 120amp, which i think would be enough for my auxiliary system. is this the product you were thinking of? https://cdn.shopify.com/s/files/1/0658/7343/files/instructions_ad8deb3d-b2a9-4f6c-bf8d-7b95407ab43b.pdf?11538045812489177130

now while this product is still obviously geared for staged lead-acid charging, according to this next link if you buy the remote controller, those stages can be customized to suit whatever you want, except that the absorb stage appears to have a minimum of 10-minutes, although not sure if you could pick a setting to skip the absorb stage and go straight to float or just set the absorb voltage to suit. https://cdn.shopify.com/s/files/1/0658/7343/files/Custom_Profile_Remote.pdf?12238550496116774793

lots of free advertising for sterling here! i have no association clearly, for all i know they could be rubbish.

edit: i just found another version of the same sterling product that says it has a lithium profile http://www.sterling-power-usa.com/library/B2B120%20sheet.pdf, the question is 120 or 180 amps?

 

[DiploStrat]

One more thought. I am far from a Toyota expert, but, from what I have been told, Toyotas are regulated to 13.9v. Can be a big issue for AGM but might be right on the money for Lithium.

NOTE: The above is not/not confirmed - do due diligence!

 

[LeishaShannon]

now while this product is still obviously geared for staged lead-acid charging, according to this next link if you buy the remote controller, those stages can be customized to suit whatever you want, except that the absorb stage appears to have a minimum of 10-minutes, although not sure if you could pick a setting to skip the absorb stage and go straight to float or just set the absorb voltage to suit. https://cdn.shopify.com/s/files/1/0658/7343/files/Custom_Profile_Remote.pdf?12238550496116774793

I'm not all that familiar with sterling's specific models as our battery is 300Ah @ 24v and our alternator is 130A so I just use a simple relay to control charging. (Fun fact - with 1200W of solar on the roof we usually have the alternator turned off to save fuel and reduce load on the engine)

the question is 120 or 180 amps?

I'd go with 120A unless the 180A model can be current limited some how and you're planning to add more battery capacity in the future.

 

[damienperu]

I'm not all that familiar with sterling's specific models as our battery is 300Ah @ 24v and our alternator is 130A so I just use a simple relay to control charging. (Fun fact - with 1200W of solar on the roof we usually have the alternator turned off to save fuel and reduce load on the engine)



I'd go with 120A unless the 180A model can be current limited some how and you're planning to add more battery capacity in the future.

wow, it would be nice to have that much roof space!

can i ask what brand and type of battery you have and how long it takes to charge? you mentioned before that you charge @13.8V, and the seller of the battery i'm thinking of says theirs must be charged @14.6V... does that mean there are the different deep cycle LiFePo4's? I've seen some like the smart battery and stark power that are crankers that must have different internals I asume.

 

[LeishaShannon]

can i ask what brand and type of battery you have and how long it takes to charge?

I built ours using 8 of these http://en.winston-battery.com/index.php/products/power-battery/item/wb-lyp300aha?category_id=176 300Ah cells. If we're charging using the alternator (3500W) and roof top solar (1200W) we can go from flat to full in 2 hours or so. Using solar only we're usually fully charged by lunchtime.

the seller of the battery i'm thinking of says theirs must be charged @14.6V... does that mean there are the different deep cycle LiFePo4's? I've seen some like the smart battery and stark power that are crankers that must have different internals I asume.

Different cell packaging and different chemistries. eg. the "smart battery" is made up of 100s of tiny cylindrical cells. I don't like this approach because of the number of cells and the delicate connections required.

Using large format prismatic cells like the Winstons requires less connections and should prove more reliable in my opinion.

The seller wants the battery charged at 14.6v because the onboard cell balancing system probably starts shunting current at 3.6vpc (14.4v) but in our experience there is no need to constantly balance the cells if they're balanced properly initially and you stick to reasonable (3.45vpc) charge voltages.

Lithium are awesome, but they're new and not always well understood even by those that sell them. Everyone's application is different too, so what works for me may not be right for you and your battery chemistry / usage pattern.

 

[damienperu]

thanks for the info mate, your a wealth of knowledge! the one's i am looking at are prismatic, so that's good to know.

so to the original issue of my existing staged AC and solar charging hardware designed for lead-acid... if i connect the auxiliary charging circuits of both those directly to the input of the big dc-dc lithium charger, then it seems I won't have to ditch them and that they will continue to charge my cranker correctly as well. i haven't thought about how the lead-acid profiles on those will behave in reaction to what they sense from the dc-dc charger, but i guess it doesn't really matter.