diy solar

diy solar

I need a standalone BMS that tracks current uptake to the LiPo4 cells

Yes, 14.0 is 3.5 volts per cell. 13.35 Float is 3.34 per cell which is where my cells rest and my Float turns off when the sun goes down so it is not on for long,
If i am motoring all night, im at float when the sun comes up. Then what? 12hrs of 14v - bad bad idead - hence this thread
 
If i am motoring all night, im at float when the sun comes up. Then what? 12hrs of 14v - bad bad idead - hence this thread

14 V is bulk... float is at 13.35 in the line you quoted and that's basically resting voltage so it's fine.
 
14 V is bulk... float is at 13.35 in the line you quoted and that's basically resting voltage so it's fine.
Yes those are the settings @Cronk should use to solve the motoring problem. Or do not motor long stretches until he finds the perfect solution using current as his cutoff point per the title to this thread. His quest for a current device is guided buy a misunderstanding of basic LFP charging characteristics. Furthermore he is influenced by out of context qoutes and misunderstandings of the important ideas in the the Marine Guide cited at the beginning of this thread. Voltage is used as a charge setting along with other parameters in charging Lithium. However, as explained in that guide, using FLA settings can shorten life of LFP.
One also needs to be careful with Alternators, as many do not tolerate having their load disconnected. Solutions are probably explained in the Marine Guide.
 
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@Cronk
I apologize for my negativity but it seems you are taking a lot of the good posts in the Marine Guide out of context. There is a thread here that might give you some help:
 
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in reading the very good article about charging LiPo4 drop ins (4 in parallel) on
ALL CHARIUNG MUST STOP once current drops to <5% of bank capacity
BNS that rely on voltage are not able to understand the history of the charging of the bank from various sources (alternator, solar, shorepower charger) and rely on voltage to indicate state of charge. This is unreliable with one or more charging sources in whats called the absorbtion phase (a misnomer in lipo world)

Drop in BMS is not programmable. The high cutoff is set to 14.8v (too high) instead of 14.7, which will impact cycle life of batteries, and has no capability for trtacking history and doing something intelligent with this information, l.ike denying all charging until bank drops to say 80% of capacity.

This results in batterys constantly being charged to 100% (every day)

I am looking for an externam "BMS" that can monitor/regulate all charging sources via say a relay and just cut out the bank leaving the LA to be charged constantly to 14.x volts or whatever.

It seems there is nothing available. The wakespeed WS500 (very expensive) will control the 160A alternator but not the solar. The solar charger will regulate the solar panels reasonably well but not the other sources.

In fact all i really need is a diverting relay that can monitor/remember current uptake history!

Perhaps its time for a Tensy project?
This could be done using a Victron Battery Monitor. There is an alarm relay in the Victron that could control a disconnect on the charging circuit.
 
@Cronk
Here is a stickie that summarizes on the first page what the Marine Guide takes many pages to describe. There should be no inconsistencies between these two documents other than perhaps the style that each author chose to write. If you do find and inconsistency, I would be happy to try to explain. It might be a good idea to download it and keep it close until you are comfortable with the concepts.
 
I skipped past a bit.
I use an orionJr2 BMS on my boat. It uses a hall effect current sensor and talks canbus to my victron system.
As a backup, I have outputs from it that feed into some optoisolators to deliver enable signals to charging and discharging systems.
This also lets me integrate into a Wakespeed 500 regulator.

My pack is very large - 28v @915ah.

The downfall of the orion BMS is that it's so tunable that it's easy to make mistakes.
But I am impressed by it.
 
I use an orionJr2 BMS on my boat.
I also use an Orion and like it. It did not have enough current to balance my cells so I turned off the balancing and used an active balancer. I like the report from the Orion and wish mine integrated with my Outback Skybox.
 
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I actually need to have a convo with them - I've yet to see it show active balancing. I've had tons of other things to deal with that took priority over it tho
 
I think the more important issue for me is that, ideally you shouldn't be paralleling your FLA and Lifepo4 packs.

What are the capacities and purposes of each pack? What is you charging current into each pack?

Lead does best when not cycled. If you're two packs are there to extend capacity, could you separate them. Have a DCDC charger (Victron makes one) float the lead acid from your lifepo4 pack?

Is the lead your starter battery?

Also, you complain about the BMS you purchased in your drop in packs? Seems like your the kind of person who would have researched that before. I probably would haven't gone with those batteries.
 
The problem is sensing the cell conditions in a sealed LFP. Any BMS will be totally clueless without that data.
That is why dropins are not so good, unless they have a builtin canbus com like Victron LFP and Lithionics.
 
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