Wagan inverters not suitable for lithium batteries?

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. ;)

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-12.8V-110Ah

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.

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?

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

Hi BFL13,

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

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

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.

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"