busted_bike
100 mW
- Joined
- Jun 24, 2010
- Messages
- 42
I have an application in mind for a battery pack as short-term energy absorption. It has little to do with EVs, but I figured I’d ask the question here since the folks on this forum have, collectively, as much battery knowledge as I’ve seen just about anywhere.
Anyway, I’m working on a circuit which will occasionally feed current back onto its power supply bus. Left unmanaged, this condition would result in huge voltage spikes on the power bus which would destroy all sorts of things. One management strategy I'm considering is to detect this condition and engage a load circuit to burn off the excess power resistively. But on thinking through it, a battery pack seems like a more elegant solution.
When the load circuit deposits energy on the power bus, the cells will naturally absorb it and the bus voltage will rise. When the circuit begins consuming energy again, the battery will discharge to supply the load and the bus voltage will drop until the main power supply re-engages to hold up the voltage. The aspects of this solution that I’m unsure about are as follows: the battery would be connected to a live power bus at a relatively low working voltage (lets say 3V/cell), nominally <10%SOC when not absorbing or supplying energy (i.e. most of the time).
Though I’m not necessarily looking for recommendations for a particular cell or chemistry at this point, long working lifespan is an important feature which the newer Li-Ion chemistries seem to lend themselves well to. Am I setting myself up for spectacular failure? This seems different enough from most battery applications I’m aware of (where the battery is charge online and discharged offline) that I’m afraid I’m missing something. Are there any similar applications that I’m not aware of? I’d feel a whole lot better if others were/are successfully doing something like this.
A couple of other notes, which might help to clarify:
• It is acceptable to employ a full-time circuit to monitor and balance at low current.
• Per-cell LVC / OVP is also acceptable, though neither of these conditions should occur if the circuit is working properly.
• It is acceptable to tune the power supply circuit so as not to trip its OVP over the working voltage range of the battery.
Anyway, I’m working on a circuit which will occasionally feed current back onto its power supply bus. Left unmanaged, this condition would result in huge voltage spikes on the power bus which would destroy all sorts of things. One management strategy I'm considering is to detect this condition and engage a load circuit to burn off the excess power resistively. But on thinking through it, a battery pack seems like a more elegant solution.
When the load circuit deposits energy on the power bus, the cells will naturally absorb it and the bus voltage will rise. When the circuit begins consuming energy again, the battery will discharge to supply the load and the bus voltage will drop until the main power supply re-engages to hold up the voltage. The aspects of this solution that I’m unsure about are as follows: the battery would be connected to a live power bus at a relatively low working voltage (lets say 3V/cell), nominally <10%SOC when not absorbing or supplying energy (i.e. most of the time).
Though I’m not necessarily looking for recommendations for a particular cell or chemistry at this point, long working lifespan is an important feature which the newer Li-Ion chemistries seem to lend themselves well to. Am I setting myself up for spectacular failure? This seems different enough from most battery applications I’m aware of (where the battery is charge online and discharged offline) that I’m afraid I’m missing something. Are there any similar applications that I’m not aware of? I’d feel a whole lot better if others were/are successfully doing something like this.
A couple of other notes, which might help to clarify:
• It is acceptable to employ a full-time circuit to monitor and balance at low current.
• Per-cell LVC / OVP is also acceptable, though neither of these conditions should occur if the circuit is working properly.
• It is acceptable to tune the power supply circuit so as not to trip its OVP over the working voltage range of the battery.