Greetings,
I'm new to the forum and looking for some guidance. I have a twin engine boat that has a fairly complex electrical system and has 7 AGM batteries divided into 3 banks (originally it was 4 banks, but I joined 3 & 4 into a single bank). I added a 100 watt Renogy solar charging system with a 10 amp Voyager controller feeding into a Victron ArgoFET 3 bank isolator. The system has worked well in maintaining the batteries, as the boat sits on a mooring away from shore power when not in use. The boat was made in 2015 and the batteries (original) are at their end of life (~ 9 years).
My plan is to re-design the electrical power system to have 2 AGM batteries (one of each engine) and 2 LiFePO4 batteries (100Ah) to supply the house & 2000 watt inverter (Xantrex SW2012). The engine alternators are rated at 70 amp and feed into a 2 alternator/3 bank isolator.
My design challenge has been to come up with a system that can charge/maintain the batteries via solar when the boat is not in use and then rely on the alternators for charging when the engines are running, and shore power when the boat is at a slip for overnights. I also have a ProNautic 1230 shore power charger when the boat is at a slip (occasional overnights). When on shore power, both the ProNautic and the Xantrex can charge batteries.
I'm fairly new to the details of lithium battery technology, but have learned the basics. After some guidance from several electrical engineering types, I have come up with the following schematic . . .
Looking for comments and guidance. . . . will it work? If not what changes may be advised to make things work (work better). Thanks in Advance . . .
View attachment 193843
I claim no expertise, but if you're looking to create a mixed lead-acid/lithium system, you should take a look at Emily&Clark's Battery Bank Manager System.
BankManager™ System
You may not decide to get one, but reading through his explanations of why he designed it will probably help.
Hello All, newbie here. jdege suggested the BankManager for tpenfield application. I would appreciate reports / reviews of experience with this device.
There's a world of blue water cruisers that depend on reliable on-board electric systems. BankManager was developed for that market, and it has apparently been recognized by that market.
If you read the white papers referenced by Clark, designer of BankManager, he has devised a charging algorithm that will protect the LiFePo battery from overcharging.
As I understand his design, this accomplished by measuring the charge voltage AND current. The charge circuit is interrupted when the battery rejects or no longer accepts amps, preventing damage from overcharging regardless of the charge rate or controller ability to regulate. When the BankManager recognizes voltage rise (volt-time line slope increase) and current rate drop (decrease) which occurs at the end of the charge cycle, the lithium bank is disconnected.
Overcharge damage cause, in particular, when a solar panel is charging a system at low power, adequate voltage but low amps, with no / low system load, the (some, most?) controllers can over-voltage the lithium bank (float voltage), and, over time, cause irreversible loss of battery capacity. Most controllers are built to operate like an acid charging device, not completely stop and shut off charge current when "full" is detected.
There are probably chargers out there that cut off when full. I can't imagine an electric automobile charging system that would not absolutely protect the battery from charging error.
Which controller manufactures recognize this peculiar lithium charging requirement?
The AIMS MPPT lithium charging selection from the users manual is 13.7 to 15v (bulk charge setting) with no absorption or float function. Have faith that the controller will not over-volt the battery. As near as I can tell, it does not shut off when full.
AIMS battery charging specification 14.4 to 14.6 max.
Wattcycle battery specification calls for charge voltage of 14.6 +/- 0.2v. No mention regarding float.
BMS is set to cut out charging at 14.4 volts. Yes, the instructions really do say this. Maybe I'm reading it wrong, or chinese translation confusion.
I have not researched any other manufactures battery charging instructions.
Clark lists a number of advantages for connection of acid and lithium batteries in parallel. For this thread, I'm interested in the prevention of over-charging lithium, and selection of the best charge controller. jdege offers a link to the Proposed Standard that better describes the need and solution to improved lithium application. See post in this thread.
Also refer to the White Paper
https://cdn.shopify.com/s/files/1/0568/1011/1110/files/Math_ScienceOfBBMS_Grillo.pdf?v=1730396821
that goes into the weeds regarding lithium science and application. This report is linked in the BankManager sales website.
Considering all the thousands of lithium batteries sold and in service, I wonder why this charging nuance is not addressed by now. Maybe it is and I have not found it yet. This appears to be the premier user forum regarding lithium applications. Congrats to Will Prouse.
No, I'm not schilling for BankManager.... just trying to find any charge controllers that recognize or address the issues described by BankManager. Does it work? This is a great project for Will Prouse to bench test. I would like to see the report.
Looking forward to replies.
Lou
Bluetent1
