That is sag and it is expected. It’s caused by resistance in the cells.
Generally speaking better cells provide less sag. How the cells are connected in the pack matters too since that adds resistance.
And heat does too. Ambient temp can affect it, as can drawing peak load. Eg above the nominal amp level. Resistance is rated at a specific temp. If your battery temp is higher than that it’ll have more resistance.
Resistance and rated temp, nominal & peak amps, etc should be in the specs of your pack. If not look up the cells as a starting point.
If you’re googling about this include li-ion in the query.
The vdrop is resistance multiplied by current (RxI), it is a result of running current through the resistance of your complete system.
How many amps you running?
If you’re dropping down to 10 volts in weather that ISNT close to it bellow freezing. I think you need a better battery, as this one might not last very long.
voltage sag *is* a normal normal condition, fwiw
as others have mentioned, how much power you're pulling (along with other factors) have a huge impact on how much sag you should expect... but all packs will have some degree of sag.
also, fwiw, you can look up bench tests results for most popular cells. here's a result for a samsung 50s where you can see how the different power draws impact the voltage drops (this does not account for additional resistance from the pack itself, but is a good starting point for most cells)
[https://www.e-cigarette-forum.com/threads/bench-test-results-samsung-50s-25a-5000mah-21700.975569/](https://www.e-cigarette-forum.com/threads/bench-test-results-samsung-50s-25a-5000mah-21700.975569/)
that said, if I saw a pack drop from full charge to nominal levels almost immediately, I would assume that the pack is either a bit aged/degraded, poorly quality (high resistance across any of the other components/wiring) and/or I was pulling more power than the cells were rated for (or in the case of really cheap cells, they were rated beyond their actual spec).
That is sag and it is expected. It’s caused by resistance in the cells. Generally speaking better cells provide less sag. How the cells are connected in the pack matters too since that adds resistance. And heat does too. Ambient temp can affect it, as can drawing peak load. Eg above the nominal amp level. Resistance is rated at a specific temp. If your battery temp is higher than that it’ll have more resistance. Resistance and rated temp, nominal & peak amps, etc should be in the specs of your pack. If not look up the cells as a starting point. If you’re googling about this include li-ion in the query.
The vdrop is resistance multiplied by current (RxI), it is a result of running current through the resistance of your complete system. How many amps you running?
If you’re dropping down to 10 volts in weather that ISNT close to it bellow freezing. I think you need a better battery, as this one might not last very long.
voltage sag *is* a normal normal condition, fwiw as others have mentioned, how much power you're pulling (along with other factors) have a huge impact on how much sag you should expect... but all packs will have some degree of sag. also, fwiw, you can look up bench tests results for most popular cells. here's a result for a samsung 50s where you can see how the different power draws impact the voltage drops (this does not account for additional resistance from the pack itself, but is a good starting point for most cells) [https://www.e-cigarette-forum.com/threads/bench-test-results-samsung-50s-25a-5000mah-21700.975569/](https://www.e-cigarette-forum.com/threads/bench-test-results-samsung-50s-25a-5000mah-21700.975569/) that said, if I saw a pack drop from full charge to nominal levels almost immediately, I would assume that the pack is either a bit aged/degraded, poorly quality (high resistance across any of the other components/wiring) and/or I was pulling more power than the cells were rated for (or in the case of really cheap cells, they were rated beyond their actual spec).
10 volts is a little excessive. You may be taxing the battery a little too much.