Alternator and BMS shut off

[Steel sails]

My Lifepo4 batteries have the charger , solar and alternator on the dc side.
When the BMS shuts off where the alternator was frying the charger before the alternator controller reacted and shut down the alternator.
The installer has now installed a complex set of relays to shut the alternator down with the BMs
How are others handling this
Regards
Paul

[exMaggieDrum]

There is a huge thread on this subject right above on today's new posts. Use the search function on CF and it will turn up as the first, or at leas near the top, thread. You'll have to get in to it a bit to get the details you are looking for. Mbartosch and Maine Sail and many others have specifically talked about your question. I'm am designing my own system right now and that thread and the included attachments and links have been invaluable.

[Maine Sail]

Originally Posted by Steel sails

My Lifepo4 batteries have the charger , solar and alternator on the dc side.
When the BMS shuts off where the alternator was frying the charger before the alternator controller reacted and shut down the alternator.
The installer has now installed a complex set of relays to shut the alternator down with the BMs
How are others handling this
Regards
Paul

Why is the BMS shutting off in the first place? If it is disconnecting charge sources then something is not set up correctly.

Think of the BMS main disconnect as the ejector seat button on a fighter jet. I am sure you'd be asking why the canopy on your plane is now gone too? The main bank disconnect is the last resort.

My guess would be that your BMS is trying to "manage" your charging and that is really not the role a BMS should play. Charge sources should be properly programmed for the LFP bank and ONLY when an incident occurs would the HVC come into play and then if for some very odd reason HVC did not stop it the main bank disconnect would open.

Ideally there should be an HVC disconnect point that is before any 100% bank disconnect. If using an external regulator such as a Balmar the red B+ wire is used for HVC not the brown ignition wire. Open circuiting an alternator can cause a transient this is why a well designed HVC shut down cuts power to the field and the alternator shuts down correctly or you dump it to another bank before it trips..

[Steel sails]

Thanks for answering Maine Sail. I realize it's probably been covered in the Lifepo4 thread but that is over 300 pages long.
My charge shut off is 29.4 volts and the BMs shut off is 30v. We think the alternator wire was to small causing a voltage drop and therefore still sending current once the battery reached 30v
We ran a heavier wire and that seems to have resolved the problem
The alternator uses the Mastervolt alpha pro.
As a back up they installed a relay that on the alternator field that cuts power in the event of BMs cut off.
Maybe the charge shut off and BMs cut out are too close
Batteries are Winston 400 AH x8 for 24v system
Charged
Mastervolt 2500
100 amp alternator
750 watts solar through 2 genasun smart controllers
Thanks Paul


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