LifePo4 Charge Performance

[otrfun]

Thinking seriously about replacing our two GC2's with a pair of 100ah LifePo4's. Hearing a lot of chatter about how lithiums accept a charge much quicker than lead cells.

Very familiar with how our GC2's charge after being discharged to 50%. It typically takes our 45a converter 2.5 - 3.0 hours to charge them from 50% to ~90% (at 14.4v).

Assuming a pair of 100ah LifePo4's were discharged to say, 10-20%, roughly how long would it take a 45a converter to charge two 100ah LifePo4 batteries to 90-95% assuming the converter remained at 14.4v the entire time?

Thanks!

[StirCrazy]

BFL13 wrote:
"Trillium features a Trojan-specific cell...... It’s cobalt-free and nickel-free, and it features the industry’s safest chemistry"

They say it is "Lithium-ion". If that is not LFP ??, then perhaps it acts differently. Not a clue.

This explains the various types of Lithium-ion cells. It mentions the 41F figure in the part about charging, so it might apply to the LFP versions ?????

https://en.wikipedia.org/wiki/Lithium-ion_battery

"Li?ion batteries offer good charging performance at cooler temperatures and may even allow 'fast-charging' within a temperature range of 5 to 45 °C (41 to 113 °F).[134][better source needed] Charging should be performed within this temperature range.

At temperatures from 0 to 5 °C charging is possible, but the charge current should be reduced"

no lithium ion has many different forms and LiFePo4 is only one of them. Nickel cadium is a type of Li and so on, there are at least 6 different Li types out there in use. this is why it can get confusing.

oh and dont take wikipedia as gospal, anyone can edit it, plus you dont know what format of Li the author was talking about. this is the most confusing part about Li, everyone refurs to it in the generic but each type has its own properties. for instance LifePo4 is the least likly to catch on fire during use LOL.. it is considered the safest. mind you I havent read much about tirillium yet so that might be even better.

Steve

Steve

[BFL13]

"Trillium features a Trojan-specific cell...... It’s cobalt-free and nickel-free, and it features the industry’s safest chemistry"

They say it is "Lithium-ion". If that is not LFP ??, then perhaps it acts differently. Not a clue.

This explains the various types of Lithium-ion cells. It mentions the 41F figure in the part about charging, so it might apply to the LFP versions ?????

https://en.wikipedia.org/wiki/Lithium-ion_battery

"Li?ion batteries offer good charging performance at cooler temperatures and may even allow 'fast-charging' within a temperature range of 5 to 45 °C (41 to 113 °F).[134][better source needed] Charging should be performed within this temperature range.

At temperatures from 0 to 5 °C charging is possible, but the charge current should be reduced"

[StirCrazy]

BFL13 wrote:
Trillium guide linked earlier and your post about BMS.

I got my SiO2 in October, and local LFPs were and are still high priced for drop-ins.

Things are getting better for LFP pricing according to reports on this forum. Local pricing depends on what the dealers' costs were when they got them for how much they can lower them if forced to by the market.

eg, http://www.wegosolar.com/categories.php?........ory=Deep-Cycle-Batteries/CAN-BAT-Lithium

I saw that one PT recently posted at a very low price for LFP.

well the BMS website doesnt talk about tempature variations, and neither does any LiFepo4 spec sheet I have seen so that might just be a trillium thing. but thinking about it why does that matter, if you put the battery bank inside the heated rv then it becomes a non issue, as as far as I know it is a non issue with LiFeP04, unless I can find something that says other wise but nothing mentions anything with cold charging except don't do it under 0C.

I keep looking but I have read through several papers and several sights now and none mention that. also if it was an issue none of this is dealing with the tempature outside, but rather the actual tempature of the battery its self. I have also read of people when it is -4 or 5 out they put a load on the battery and it has warmed it up so the battery was above 0 then they could start charging it and the charge curent warmed it up further but thats not what we are looking for here and I am digressing. just remember trillium is a different tech than Lfp and has different requirments and such, just like niCad has totaly different peramiters than LFP and so on.

Steve

[StirCrazy]

BFL13 wrote:
Be worth knowing for those interested if the heating blankets need PSW 120v like electric blankets do.

Reminds me, itinerant1 explained how he uses a heater to warm up his batts before charging them in cold temps. So that means he has to not get the batts so low that they can't run the heater for long enough to warm the batts. You would need to work out the AH the heater would need next morning and be careful to not let the furnace run the batts down past that SOC overnight.

Nothing very complicated, but you would be stuck if you forgot.

you can still discharge down to -20C, just have to be above -1C to charge, so there shpould be an issue there.

Steve

[Itinerant1]

BFL13 wrote:
Be worth knowing for those interested if the heating blankets need PSW 120v like electric blankets do.

Reminds me, itinerant1 explained how he uses a heater to warm up his batts before charging them in cold temps. So that means he has to not get the batts so low that they can't run the heater for long enough to warm the batts. You would need to work out the AH the heater would need next morning and be careful to not let the furnace run the batts down past that SOC overnight.

Nothing very complicated, but you would be stuck if you forgot.

Using the heater uses a litte more than the my mw (148a) as long as SOC 35-40% no problem for 30 minutes. You just must learn to know your system and having individual cell readings takes ALL guess work out of it.

[BFL13]

Be worth knowing for those interested if the heating blankets need PSW 120v like electric blankets do.

Reminds me, itinerant1 explained how he uses a heater to warm up his batts before charging them in cold temps. So that means he has to not get the batts so low that they can't run the heater for long enough to warm the batts. You would need to work out the AH the heater would need next morning and be careful to not let the furnace run the batts down past that SOC overnight.

Nothing very complicated, but you would be stuck if you forgot.

[3_tons]

BTW, For those interested in LiFePo4 for cold weather applications but have exterior unheated battery compartments, I just ran across this heating blanket which can be easily repurposed to heat a Li battery (per Expion) with the addition of a simple thermostatic switch. These heating blankets come in either 12 or 120v versions.

Blanket choices from Amazon:

https://www.amazon.com/gp/product/B01N7QVBJJ/ref=as_li_ss_tl?ie=UTF8&linkCode=sl1&tag=melmikstrucam-20&linkId=8e2d19695250a95c07cae395b2a99353&language=en_US&th=1

Thermostat Switch at Expion’s site:

One Battery Heater Switch (Part No. EV-V120-BHS $8.00 ea. Retail plus shipping).

Expion also sells thermal insulating blankets.

Available at: https://www.expion360.com

3 tons

[time2roll]

BFL13 wrote:
The BMS keeps the amps under its size of 200 amps, but how does it keep the 100a charger at 30 amps when the temp is below 41F?

Seems like you need a 30 amp charger

PWM in the BMS based on temperature would work.

[BFL13]

Trillium guide linked earlier and your post about BMS.

I got my SiO2 in October, and local LFPs were and are still high priced for drop-ins.

Things are getting better for LFP pricing according to reports on this forum. Local pricing depends on what the dealers' costs were when they got them for how much they can lower them if forced to by the market.

eg, http://www.wegosolar.com/categories.php?category=Deep-Cycle-Batteries/CAN-BAT-Lithium

I saw that one PT recently posted at a very low price for LFP.

[StirCrazy]

BFL13 wrote:
The BMS amps size is chosen for your intended discharge to run the MW say 200 amps size to cover the 150 amps and a bit so you can leave the TV on while running the MW.

Now the charging spec says (on 200AH) you can charge at 200a if above 73F, 112a if above 41F, and 30 amps if under 41F.

You have a 100a charger and a gen to run that, so you can use that above 41F, but it is 35F and you need a recharge. Now what?

The BMS keeps the amps under its size of 200 amps, but how does it keep the 100a charger at 30 amps when the temp is below 41F?

Seems like you need a 30 amp charger

where did you read this, I cant find anything like that.

Steve

[StirCrazy]

BFL13 wrote:


That's way better on one 100AH batt than with regular AGMs, and why I got the battery. LFPs can do that too or even more so, but I had no need to spend twice as much for an LFP, and I was nervous about the low temp issue for our scenarios.

where are you getting twice as much for a 100amp LFP? Pianotuna posted some that are about 400 bucks, the Sio2 was surley more than that as when I called and asked about it it was about 600 plus shipping. I could see if you were looking at the battleborn as they were early to the market and realy inflated the pricing, but all of them should be coming down in price now that there are others in the lower price range. unless they just launch a markiting campain to try slam the other brands and continue to charge way to much for what they are..

Steve

[BFL13]

pianotuna wrote:
Hi Steve,

The SiO2 specification is zero volts and over six hundred cycles to 80% of OEM capacity. Whether that is "puffery" or a real honest to goodness number, I do not know.

I don't know which site I found it on, unfortunately.

Soneil specs say you will get 620 cycles with 100% DOD, 1500 with 80% DOD etc.

Resting voltage at 100% DOD is 11.1v.

When I ran my test with 65 amps draw on the 100AH batt with inverter doing the MW in the TC (small MW with MSW inverter so amps not so many as with PSW) the inverter eventually alarmed at 11v, then the battery bounced back to 11.7v, which is 20% SOC/80% DOD.

I am not sure how the discharge table works, but seems to say that a 62 amp draw should take an hour to run the battery down and the "end-voltage per cell" would be 1.6v so x 6 = 9.6v I didn't run the battery down that far. ( ISTR I got over 30 min of MW run time before it alarmed, but don't have my notes on that)

So "end-voltage" is not the resting voltage for 100% DOD? You would get bounce back from the end-voltage to go up to the resting voltage?

That's way better on one 100AH batt than with regular AGMs, and why I got the battery. LFPs can do that too or even more so, but I had no need to spend twice as much for an LFP, and I was nervous about the low temp issue for our scenarios.

[3_tons]

3 tons wrote:

“The primary function of the BMS is to avoid catastrophic events and to perform individual cell balancing - the BMS does not govern charging amperage, and for some manufacturers serves as a low temp charge disconnect.”

StirCrazy wrote:

“only if your talking the cheep 15 to 30 buck ones.”

Thanks for clarifying this fact, I mentioned this in the context (AFAIK) of a drop in type battery - it’s very interesting what these custom LiFePo4 builders are able to!

3 tons

[BFL13]

The BMS amps size is chosen for your intended discharge to run the MW say 200 amps size to cover the 150 amps and a bit so you can leave the TV on while running the MW.

Now the charging spec says (on 200AH) you can charge at 200a if above 73F, 112a if above 41F, and 30 amps if under 41F.

You have a 100a charger and a gen to run that, so you can use that above 41F, but it is 35F and you need a recharge. Now what?

The BMS keeps the amps under its size of 200 amps, but how does it keep the 100a charger at 30 amps when the temp is below 41F?

Seems like you need a 30 amp charger

[pianotuna]

Hi Steve,

The SiO2 specification is zero volts and over six hundred cycles to 80% of OEM capacity. Whether that is "puffery" or a real honest to goodness number, I do not know.

I don't know which site I found it on, unfortunately.