Wagan inverters not suitable for lithium batteries?

[jaycocreek]

I was reading the reviews on amazon for Wagan inverters and wagon CS said there 1000 watt psw is not ideal for lithium batteries with the different voltage parameters..

Is this true and are there other inverters that are not ideal for lithium batteries and especially,what inverter is ideal/the best for lithium because I am needing a 1000-1500 PSW that doesn't break the bank...

[BFL13]

Itinerant1 wrote:
Note that most of the bms's are not shutting down to low pack voltage but most likely to low cell voltage. The drop in manufacturers wouldn't want the packs eatting their own cells.

That is why it's best if possible to have a user adjustable inverter for low shutoff than have the battery use it last hail mary shutdown event.

The Victron monitor has something going about that as one of its features for how to install it, except it is for whole batteries in series too:

"More about midpoint voltage:

One bad cell or one bad battery can destroy a large, expensive battery bank. When batteries are connected in
series, a timely warning can be generated by measuring the midpoint voltage. Please see the BMV manual,
section 5.2, for more information.
We recommend our Battery Balancer (BMS012201000) to maximize service life of series-connected batteries"

[Itinerant1]

Here are some #s.

Today using 15k air conditioner off of batteries and some sun.
3:07pm 99% soc, batteries 13.31v -54.8a load, Inverting 13.0v -119a 715.5w solar (AC just started)
4:06pm 83% soc, batteries 13.13v -78.7a load, Inverting 12.8v -130a
526.6w solar (AC running)
4:37pm 75% soc, batteries 13.06v -86.5a load, Inverting 12.7v -130a
410.8w solar
4:39pm 75% soc, batteries 13.24v +19.6a charging, Inverting 13.1 -9a 401.6 w solar (AC shutdown 1 minute ago)

This was a low SOC high amp load with little to sun helping (overcast, raining) from the past.
12:11pm 29% soc batteries 13.03v -2.9a, Inverting 12.9v -9a humidifier running, just before using microwave.
12:11pm 29% soc batteries 12.74v -127a, Inverting 12.4v -147a microwave started.
12:15pm 28% soc batteries 12.65v -125.9a, Inverting 12.3v -146a microwave finishing use.
12:16pm 28% soc batteries 12.93v -1.7a, Inverting 12.8v -9a after shutting microwave off.

[2oldman]

time2roll wrote:
Yes wait 'till sundown for the test.

Starting voltage 52.2. A/C on, drop to 51.4. After 3 minutes, 51.0. Recovered in 2 minutes to 52.2

[pianotuna]

Hi BFL13,

The Magnum hybrid inverter/charger does allow me to adjust the low voltage cut out iirc.

[BFL13]

I don't know of any user adjustable low voltage shut-down or alarms in inverters (? perhaps in inverter/chargers?)

There is an adjustable shut down in ISTR a Victron battery monitor that might do the job. some also have an auto gen start, but I would hate for the gen to come on in the night and wake everyone up for miles around!

What would be suitable shut off voltages for a 12v LFP above the BMS shut off voltage?

Victron:
- Programmable visual and audible alarm
- Programmable relay, to turn off non critical loads or to run a generator when needed

[pianotuna]

LiFePo4 are clearly not for the faint of heart.

I saw a William Prous video today where he suggested that the battery management system might be permanently damaged by the capacitors in a large inverter charging from the battery.

I've never heard of such an issue before--and he is a bit of a nutter in some ways.

Has anyone seen another report of this phenomenon?

[Itinerant1]

Note that most of the bms's are not shutting down to low pack voltage but most likely to low cell voltage. The drop in manufacturers wouldn't want the packs eatting their own cells.

That is why it's best if possible to have a user adjustable inverter for low shutoff than have the battery use it last hail mary shutdown event.

[BFL13]

It does appear that the "smart BMS" with SOC indicator such as Trillium has in a drop-in, or one that you can get for a roll-your-own, will not allow you to go without an AH counter as well.

http://www.wegosolar.com/products.php?product=Trillium-Battery-%252d-Trojan-Intelligent-Lithium-12.8...

[Itinerant1]

I'm going to chime in and say that using lfp and inverter with high amp draws at a low SOC without a minitor or knowing it's at a low SOC and still want to watch Mary Poppins you deserve to have the system shutdown if your not smart enough charge the battery. 😉

[time2roll]

Yes wait 'till sundown for the test.

[2oldman]

time2roll wrote:
Maybe 2oldman can share how much voltage bounce back is seen after running the air conditioner or microwave.

Sure will, although I usually do that with the solar attached. I assume you mean with no charging attached....

[BFL13]

time2roll wrote:
Maybe 2oldman can share how much voltage bounce back is seen after running the air conditioner or microwave.

Using Battle Born - 20% SOC = 12.9v resting and another LFP's BMS low voltage cut off is at 10v +/- 0.2v (Don't know what us typical BMS shut off)

If total voltage drop from an inverter load of X amps is 0.6v, at 20% SOC inverter will see 12.3v well above its alarm, but then you run the load for a time to get some AH as the voltage comes down.

You could run it to when inverter shuts down at 10.5v while battery is at 11.1v which is well above the BMS shut down of 10v. Battle Born 11.1v resting is about ? SOC (12.0v= 9% and 10.0v = 0 dead)

Pretty close though--watching TV with its lower amps draw and less voltage drop would have the battery voltage lower when the inverter sees 10.5, but that is closer to the BMS shut off.

Then the furnace starts up and adds to the total draw so inverter sees 10.5. You don't want to miss the rest of the TV show, so leave some for the furnace!

If the BMS did get triggered, you need to get the battery bank working again. You have a "reconnect" voltage of 11.x or ?? a "reset" button some have. Is the reset for the BMS at any voltage or do you have to get the batts up in voltage if the "bounce back" is not to the "reconnect" voltage

BMS shut off from here:

https://www.canbat.com/downloads/CLI100-12.pdf

[3_tons]

Well, one possible interpretation is that the battery is at 100% SOC yet the BMS Balancing process is still underway, thus the 13.x volts concurrent with 10.x amps - if this is in fact the case, the display amps and volts values will alternate to-and-fro to say 14.x v and zero amps and back again (per display) until amps stay at zero (assuming no parasitical loses)...But there’s no real need to fully charge the battery after every use - occasional full charges are enough to allow for BMS cell balancing...

3 tons

[time2roll]

Seems like a long way to 14.6 volts. I assume it will pop at the end very quickly.
The good part is the NOCO should run full 10 amps to the top.