How does an FET isolator, like Victron's Argofet handle different charging protocols? For example a house LFP bank is charing at 14.1v while the start AGM battery is at a float stage at 13.6v.
FET Battery Isolator and Different Charging Voltages
- Thread starter dlochner
- Start date
We have Cristec MOSFET based isolators taking the output of our alternator and splitting it to house, start, and thruster banks. When the alternator is running the isolators hold all banks at the same voltage. If the alternator is in absorption mode putting out 14.1V all of the banks are at that level.
Our only other charge source is a 3 bank charger, so I don’t know what happens if the banks are being charged by individual charge sources (eg solar charging only the house bank).
Our only other charge source is a 3 bank charger, so I don’t know what happens if the banks are being charged by individual charge sources (eg solar charging only the house bank).
Each bank gets what the alt is delivering. Impossible to have two different voltages through an argofet.. You would need an Orion TR Smart for that.
That does present a conundrum doesn't it. The alternator output would go first to the LFP house bank with the AGM start being charged by the Orion. This would work until the BMS dump and fried the Balmar alternator protection module. It would be wise then to carry an extra APM.
If I go the other direction, alt to start battery first, then I lose the advantage of a high output alt and LFP.
Hmmm.... decisions.
The APM is built for this. I was the one who pushed Balmar to build it and kept pushing them to do all the right testing. We had done plenty of it on our test bench but could only drive about 170A on our test bench. they are so confident in it they don’t even include a fuse.We saw too many Sterlings with blown fuses, and the owners never knew it had blown So the next time the BMS load dumped…..
I installed a Balmar APM when they first came out last year. I have conservative settings for the Balmar smart regulator, so I feel pretty safe with the alternator connected directly to the three lfp batteries. The batteries are parallel connected and each has its own bms. What are odds that all three of the bms would shut down and cause an alternator spike?
I'm still waiting like everyone else too.That'll be fine for the next generation.
A good solution might be to connect the alternator output to the LFP house bank and charge the start battery through a DC-DC charger. But the key is to use a Balmar APM. This is a little over simplified, but you get the idea.
How good is the APM at suppressing voltage spikes during a BMS disconnect?
How good is the APM at suppressing voltage spikes during a BMS disconnect?
Very effective on the first load dump. It is a one and done solution.
Another spare part to carry.
Completely untrue . This is NOT their olderTSP…Very effective on the first load dump. It is a one and done solution.
Another spare part to carry.
Thank you! A long time ago I had a ZapStop and I understood that to be a one and done product, I incorrectly assumed the APM was similar.
But will the Balmar APM suppress the huge voltage spike that can fry sensitive electronics when the BMS disconnects?
If I understand correctly, the Class T fuse protects against the spike and the APM protects the alternator. And If I had remembered what I read on the Balmar Site, I would have known the APM can "absorb multiple surges of such energy."
Alternator Protection Modules - Balmar
Alternators can be subjected to voltage spikes caused by lithium battery shutdowns, intermittent connections and other over-voltage events. Balmar has introduced a robust Alternator Protection Module which helps protect the alternator’s diodes and internal regulator against spikes (clamping up...
balmar.net
I think I'm conflating 2 scenarios. If a cell failed it would send a huge spike through the system which the Class T fuse would protect against. If the alternator was charging at the time, the BMS load dump would cause the alt output to spike frying the diodes. The APM protects against this.
If there was a BMS dump caused by some other issue which caused the Alt voltage to spike, then the Class T fuse would not protect the circuits. The APM would however protect the alternator and prevent a spike from the Alt into the system. I wonder if the small, 1 or 2 amp fuses at the electronics would protect the electronics in this situation.
If there was a BMS dump caused by some other issue which caused the Alt voltage to spike, then the Class T fuse would not protect the circuits. The APM would however protect the alternator and prevent a spike from the Alt into the system. I wonder if the small, 1 or 2 amp fuses at the electronics would protect the electronics in this situation.
I don’t believe this is the case with any internal BMS batteries. Victron Smart Batteries and Lithionics External BMS model, yes. But they have a single BMS communicating with the individual batteries.