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Documentation for Alternator Regulator
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Lifepo4 charging parameters #2

Closed newbezz closed 6 years ago

newbezz commented 6 years ago

Hello First I should thank you for all your contributions to the creation of intelligent systems we can use for our boats etc. I were already aware of you contributions to the development of CAN-systems, but had completely overlooked your work on regulators. This is (also) of great use to so many of us!

From my first browsing through the documentation on the charging regulator I am left with one observation concerning Lifep04-batteries (well knowing that you say that this subject is all still in a developing phase): In the settings-table, you assign a comparable low charging voltage of 13,8V to these batteries. You also suggest to shut off charging after 1 hour. To me (and from what I have learned from the dokumentation for the so-called Winston cells), this seems a very cautious approach, and one that might not fully harvest the full potential of these batteries. I'm most probably missing something here, but what? Kind regards Jorgen

rgleason commented 6 years ago

Jorgen, there are active users of LiFePo4 who believe they will get longer life by not pressing up the curve further, and they are suggesting 13.8v as the stop point and 14.0v as HVD High voltage disconnect.

High Voltage Disconnect 3.50 14.00 HVD   User set
Stop charging 3.47 13.88     MaineSail Graph-Max charge LiFePo4 Graph  0.4C charge rate cut back at end  2hr 30 min
Stop charging 3.45 13.80   100% Johnct - stop charging
Stop charging 3.45 13.80 I taper   Travelerw - charge to & hold CV until the current tails to C/100ish (5a for 400Ah). consider it %100 full (actually %92-%95)
Stop charging   13.80 I taper   MaineSail - Current limiting or acceptance taper is 10-20 min at 13.8v 14.0V / 3.45 - 3.5vpc
thomasonw commented 6 years ago

Hello, and thank you for the question (and the compliment : - )

As rgleason pointed out, there is evidence that using a lower terminal voltage when charging Li based batteries will result in longer life-span. However I also note that there is still a bit being learned about larger Li based battery banks deployed in house usages. AND I am also noting several key players (Lithionics, Trojan) have charge profiles with higher terminal voltages.

It may well be that higher voltages are acceptable in the end, certainly it would shorten the charge time. One can always adjust CPE #8 to match these higher values.

But for the Regulator, there is one other reason for using the lower terminal voltages by default: I am not always assured a deployment has a BMS. By choosing the values I did, it kind of places me in the middle of the knee - providing a bit of margin for individual cells which might be slightly higher or lower SOC then the rest of the bank.

rgleason commented 6 years ago

AND I am also noting several key players (Lithionics, Trojan) have charge profiles with higher terminal voltages.

Yes, we've noticed this. I have not seen what Genasun does.

for the Regulator, there is one other reason for using the lower terminal voltages by default: I am not always assured a deployment has a BMS.

Yes, there is a group of users who do not have BMS. I think your approach makes sense.

I guess the values are all adjustable?
Thank you! for your work!

thomasonw commented 6 years ago

@rgleason Adjustable? Absolutely. Fully adjustable! A prime goal for this project was to have an "engine" if you will that was very flexible and able accommodate different deployments - including technology that is evolving ass well as technologies which are not out there yet. With that I have indeed per-defined 8x 'default' profiles, but by no means is one locked into it. Take a look at the Comms manual and you can see how to adjust the CPEs to your liking. CPE #7 and #8 are configurable.