Lithium battery limitation

George
As I see it,
A 1000w load will be drawing well over 80 amps from the battery, 12.5v X 80 = 1000, then there is losses in the switching and even more amps drawn than the basic equation, because of losses and not just the load. Do you know the acceptable discharge current for the battery and it's BMS? That constant battery discharge ability will govern it. A 2500 inverter may not be quite as efficient as a smaller unit and although possibly limiting the load to less than 1000w the power consumed from the battery may be more than 1000 anyway. A bit hard to quantify it all without test gear.
I have a few inverters and the smaller 300w Pure sine wave uses less current than the 1000w pure Sine wave while running the same load.

This might help George:

What size Inverter can I use on my lithium battery (Enerdrive)?

Keep in mind that Enerdrive is talking about their own B-TEC battery with INTERNAL BMS here (extract):
"The internal BMS setups have a safeguard built into their system. If a battery reaches/exceeds the maximum current output, the battery will switch off internally to protect the BMS and the cells from over discharge......."

I'm no expert but have been doing a LOT of reading about lithiums in recent weeks. Would have thought that most decent BMS' should ensure no damage is done if you overload the battery (should shut down). Also seems reasonable to assume that keeping your total load under 1000w ought not have any effect (other than depleting your battery of course) but if the "manufacturer" says damage might be done to the BMS itself then you're risking that AND your warranty to boot. How will you ensure that you (plural) won't exceed the load?

Btw LiFePO4s should be ~13V at ~80% DoD if you want to be more precise in your calcs: https://enerdrive.com.au/2017/11/29/can-charge-lithium-battery-lead-acid-charger/

"A 12v lithium LiFePO4 battery fully charged to 100% will hold voltage around 13.3-13.4v. Its lead acid cousin will be approx 12.6-12.7v. A lithium battery at 20% capacity will hold voltage around 13V, its lead acid cousin will be approx 11.8v at the same capacity.

What brand battery if you don't mind me asking?

My answer is..... yes you can...... I'd just keep loads to less than 1,000w continous..... which would keep your current draw to around 80amps .... no worries at all.

I would suggest a larger (ie 2500w) inverter "idling" at 1,000w would most probally be cleaner or a nicer load then a 1,000w one running flat out at 1,000w..... especially if the 1,000w one overloads and drops out from time to time.

A bit more investigation and it seems 100A max continuous discharge current is pretty standard for 200Ah lithiums George. That equates to about 1330W (13.3V x 100A) continuous power usage.

If your battery has a 75A "Continuous Discharge Limit (BMS)" or "max continuous discharge current" (same thing) that is pretty much spot on the 1000W inverter limit suggested by your maker. At that point the BMS should disconnect, not self-destruct as they seem to be suggesting.

Edit: I re-read your replies and see your battery is 200A max (presumably continuous). That makes their 1000W inverter limit even more puzzling.

Interested to hear what they say after you've spoken to them because I'm close to buying a lithium (~120Ah) for camping.

.
Hi George,

The simple answer to your question is 'yes'.
Limiting your inverter load to 1000W would satisfy the battery manufacturer's requirement.
No need to theorise why the manufacturer imposed that limit. It would be pure conjecture.
I can imagine possible reasons for the limitation but would not indulge in conjecture.
If you cannot accept the 1000W load limit then ask the manufacturer's advice.

LiFePO4 lithium batteries have only 3 or 4 useful advantages over AGMs.
1. Lower weight.
2. Longer life (probably/maybe).
3. The ability to deliver higher discharge rates with less voltage drop.

I don't understand why one of those would be so compromised by a manufacturer/seller to destroy that feature.
That only leaves lower weight as a reason I would buy one of these particular batteries and since there are better choices, that won't happen.
Cheers,
Peter
OKA196 motorhome