Turd Furguson
it's a funny name.
- Joined
- Jan 27, 2020
- Messages
- 64
Charging LifePo4 with an alternator will melt it.
This is true, but what about high-amp units that are designed for smarter charging with an external regulator?
Consider an alternator controlled by a Xantrex XAR that has variable settings for voltage, current, etc. It also has temperature control which prevents overheating. Victron demonstrates similar capabilities for Balmar in this video:
https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/
With the exception of PRG-2 & PRG-5 in the table below for the Xantrex unit, a LifePo4 battery would never achieve a maximum charge at 14.6v, or higher, that would threaten approaching a high-voltage shutdown by the BMS. 100% SOC couldn’t be achieved but we are close enough at the PRG-4 setting of 14.4v. PRG-1 gives more buffer for increased comfort.
This controller can also limit maximum current as a percentage of alternator capability from 40-100%. So, if we didn’t want to rely on thermal throttling entirely we could limit output to 40amps as an example, aligning with a DC-DC converter.
Given this, how is direct LifePo4 charging a significant risk over a deeply-depleted SLA bank when you’re not seeking a full 100% SOC? From what I see, current limiting & temperature control is already provided by the alternator controller, and risk of a high-voltage disconnect is very low as we’d never get there on a bulk charge profile under 14.6v.
Risk of disconnect in this scenario isn’t much different than pulling the cables on an SLA bank. We can also leverage the full output potential of the alternator if/when the conditions support it.
DC-DC chargers are recommended in many articles - these could load an alternator similarly and we’d rely on the same thermal throttling to protect it. Therefore, this device would only serve to prevent a disconnect scenario that is mitigated by a voltage setting below 14.6; we can also control alternator current as mentioned above to the same 40amps if desired. DC-DC chargers also introduce another box and potential point of failure in the system.
I see the overall risks & problems with alternator charging reduced significantly if you're not chasing maximum charge.
Thoughts?
This is true, but what about high-amp units that are designed for smarter charging with an external regulator?
Consider an alternator controlled by a Xantrex XAR that has variable settings for voltage, current, etc. It also has temperature control which prevents overheating. Victron demonstrates similar capabilities for Balmar in this video:
https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/
With the exception of PRG-2 & PRG-5 in the table below for the Xantrex unit, a LifePo4 battery would never achieve a maximum charge at 14.6v, or higher, that would threaten approaching a high-voltage shutdown by the BMS. 100% SOC couldn’t be achieved but we are close enough at the PRG-4 setting of 14.4v. PRG-1 gives more buffer for increased comfort.
This controller can also limit maximum current as a percentage of alternator capability from 40-100%. So, if we didn’t want to rely on thermal throttling entirely we could limit output to 40amps as an example, aligning with a DC-DC converter.
Given this, how is direct LifePo4 charging a significant risk over a deeply-depleted SLA bank when you’re not seeking a full 100% SOC? From what I see, current limiting & temperature control is already provided by the alternator controller, and risk of a high-voltage disconnect is very low as we’d never get there on a bulk charge profile under 14.6v.
Risk of disconnect in this scenario isn’t much different than pulling the cables on an SLA bank. We can also leverage the full output potential of the alternator if/when the conditions support it.
DC-DC chargers are recommended in many articles - these could load an alternator similarly and we’d rely on the same thermal throttling to protect it. Therefore, this device would only serve to prevent a disconnect scenario that is mitigated by a voltage setting below 14.6; we can also control alternator current as mentioned above to the same 40amps if desired. DC-DC chargers also introduce another box and potential point of failure in the system.
I see the overall risks & problems with alternator charging reduced significantly if you're not chasing maximum charge.
Thoughts?
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