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

[Cronk]

in reading the very good article about charging LiPo4 drop ins (4 in parallel) on

DIY LiFePO4 Batteries On Boats - Marine How To

DIY LiFePo4 On Boats Last edit;3/26/23:The base of this article was written a number of years ago (2010) but this does not mean the information here is outdated. We have been keeping it updated and have added to it when ever we had the time. This article deals

marinehowto.com

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?

 

[DThames]

I would be looking at the charger for proper control.

 

[Cronk]

which one?

1. The solar charger
2. The Alternator charger
3. The 220v shore power charger

Thats the point... one or MORE may be acting at different times doing different things

 

[DThames]

which one?

1. The solar charger
2. The Alternator charger
3. The 220v shore power charger

Thats the point... one or MORE may be acting at different times doing different things

Do I understand that you have LiFePo4 and lead acid in parallel?

edit: If so, can you set the boost voltage down a bit for all of the chargers?

 

[Cronk]

Yes. Correct.
>can you set the boost voltage down a bit for all of the chargers?
no no no. This is approach is not going to work because holding LiPo4 cells above their resting voltage will continue to charge them and after a few hours, their life is cut in half

ALL CHARGNING MUST STOP

Please read my post carefully. This is not a fungable criteria :/

 

[DThames]

Yes. Correct.
>can you set the boost voltage down a bit for all of the chargers?
no no no. This is approach is not going to work because holding LiPo4 cells above their resting voltage will continue to charge them and after a few hours, their life is cut in half

ALL CHARGNING MUST STOP

Please read my post carefully. This is not a fungable criteria :/

You charge them until they reach the proper/desired voltage, hold that for X amount of time and then drop back to float. If you can adjust your boost voltage and boost duration you can solve the problem (mostly). The issue of having 3 separate chargers should not be a big issue if you are only using one at a time, so the boost hold time is not overlapped by a second charger.

If you don't address the problem at the charger level you will need something (which is what your question is) that will.
1. somehow completely disconnect the LiFePo4 once it is charged and allow the lead acid to be the only battery, charging to a higher voltage.
2. then somehow when the lead acid voltage drops back to be the same as the LiFePo4, to put the LiFePo4 back in the circuit, back in parallel again.

You can't keep the batteries in parallel and have them at different voltages. In parallel they will always be the same voltage, or draining one to be equal with the other. You might do something with some large power diodes. But if the batteries are in parallel you should only charge to the voltage of the lower tolerant chemistry and only discharge to the low voltage of the higher tolerant chemistry. You must give up something on each end of the charge discharge curve if you mix chemistries with different min and max voltages.

 

[Cronk]

>old that for X amount of time

That is an approximation only
The CORRECT method is to monitor CURRENT

Hence this thread...

 

[DThames]

>old that for X amount of time

That is an approximation only
The CECT method is to monitor CURRENT

Hence this thread...

So you want to stop all charging, including charging of the lead acid when some current monitor agrees that the LiFePo4 are fully charged?

 

[Horsefly]

because holding LiPo4 cells above their resting voltage will continue to charge them and after a few hours, their life is cut in half

Where did you hear this? Nothing I have experienced, seen posted anywhere including on this forum says this. You don't want to hold LiFePO4 at the full 3.65V/cell beyond absorption, as that can cause the cells to degrade some over time. But "life cut in half after a few hours" sounds like someone trying to scare you.

 

[BradCagle]

I'm not fully understanding what you're saying.

But Most smart BMS's like JBD know the capacity, and SOC of your battery. However these things are not super reliable because many shunts used in these, even vicrton smart shut does not count small currents, these will add up overtime.

Also don't worry about charging your batteries to 100%, it's fine with LiFePO4.

I set my chargers to do 3.4 -3.5 per cell, and all is well.

 

[DThames]

Where did you hear this? Nothing I have experienced, seen posted anywhere including on this forum says this. You don't want to hold LiFePO4 at the full 3.65V/cell beyond absorption, as that can cause the cells to degrade some over time. But "life cut in half after a few hours" sounds like someone trying to scare you.

Charge to 3.50 or 3.55v and you can hold that for a while and not do any harm at all. 3.5v x 4 is only 14.0, which might not be ideal boost for lead acid (he has lead acid in parallel) but 14.0 will pretty well fully charge lead acid. So crank down the boost voltage would be a fair solution.

 

[John Frum]

ALL CHARIUNG MUST STOP once current drops to <5% of bank capacity

Ok.

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.

I use jbdtool on a pi with a perl wrapper to terminate charge on tail current among other things.

Perhaps its time for a Tensy project?

Googling "Tensy" was not fruitful.

 

[Cronk]

So you want to stop all charging, including charging of the lead acid when some current monitor agrees that the LiFePo4 are fully charged?

No
As I stated in my first post: I am looking for an external "BMS" that can monitor/regulate all charging sources via say a relay and just cut out the lipo bank leaving the LA to be charged constantly at 14.x volts or whatever.

>Where did you hear this?
The link I posted at top :/

>"life cut in half after a few hours" sounds like someone trying to scare you.
Read the real world case studies on that link :/

>But Most smart BMS's like JBD know the capacity, and SOC of your battery.
That is what I need. an external BMS that can measure current uptake

>Also don't worry about charging your batteries to 100%, it's fine with LiFePO4.
As stated, chargning to 100% is NOT the problem. CONTINUING to charge thereafter IS
Float is a myth with lipo4 technology and absopbtion is only needed occasionally if cell life is important

>Googling "Tensy" was not fruitful.

TEENSY 3.2 Development Board

TEENSY 3.2 Development Board

components101.com

>I use jbdtool on a pi with a perl wrapper to terminate charge on tail current among other things.
now we are gettign somewhere. Let me google that...
THIS?

JBDTools V2.4

Hi does anyone have the above? I bought a BMS and the vendor says this is the correct PC software for it but all their attempts to get me the file seem to be blocked. They can't seem to dropbox it to me and their attempts to email it are failing maybe due to file size. Anyone have it? Thanks

diysolarforum.com

Is there a 160A rated version? Ill just treat each of the 4 batteries as a cell..

 

[John Frum]

THIS?

JBDTools V2.4

Hi does anyone have the above? I bought a BMS and the vendor says this is the correct PC software for it but all their attempts to get me the file seem to be blocked. They can't seem to dropbox it to me and their attempts to email it are failing maybe due to file size. Anyone have it? Thanks

diysolarforum.com

Yes

Is there a 160A rated version?

No

Ill just treat each of the 4 batteries as a cell..

No, jbdtool talks to your jbd bms which talks to your battery.
Which bms are you using and what is your battery configuration?

 

[John Frum]

I believe there is a 200 amp version.
Hopefully jbdtool will work with that.
In your case I would make a topology with a charge bus.
I would put a Victron battery protect between the charge bus and the battery.
Use the pi to control the battery protect probably need a solid state relay between the pi and the battery protect

 

[Cronk]

These are drop ins. (post #1 LiPo4 drop ins (4 in parallel) Drop in BMS is not programmable. The high cutoff is set to 14.8v (too high) instead of 14.7, )

 

[Cronk]

I believe there is a 200 amp version.
Hopefully jbdtool will work with that.
In your case I would make a topology with a charge bus.
I would put a Victron battery protect between the charge bus and the battery.
Use the pi to control the battery protect probably need a solid state relay between the pi and the battery protect

220a version of what?
does the victron battery protect monito current uptake? and retain the history?

 

[John Frum]

220a version of what?
does the victron battery protect monito current uptake? and retain the history?

200 amps not 220a.

BatteryProtect - Victron Energy

The BatteryProtect prevents the battery from being damaged. It disconnects the battery from non-essential loads before the battery is fully discharged.

www.victronenergy.com

The battery protect serves as a relatively high current logic controlled switch for the charging bus.
Since you are using a "drop" in battery complete with bms that can not interface with the jbdtool this will not work for you.

 

[Cronk]

>complete with bms that can not interface
Interfacing is not required
The drop in BMS are just there to prevent catastrophic revents
the External; BMS I will add will work within those paramaters so as far as its concerned, the srop in BMS doesnt exist

There is nothing on that vistron link that tells me what it does, or how it does whatever it does (
or this perhaps

Contact Information for Dongguan Jiabaida Electronic Technology Co., Ltd.

View contact details for Dongguan Jiabaida Electronic Technology Co., Ltd. including address, contact person, telephone and fax number.

dgjbd.en.alibaba.com

 

[John Frum]

the External; BMS I will add will work within those paramaters so as far as its concerned, the srop in BMS doesnt exist

I think we have different ideas of what a BMS is/does.

There is nothing on that vistron link that tells me what it does, or how it does whatever it does (
or this perhaps

"The BatteryProtect disconnects the battery from non essential loads before it is completely discharged (which would damage the battery) or before it has insufficient power left to crank the engine.

The BatteryProtect is a uni-directional device. It can only deal with current in one direction, so either current to a load, or current from a charger, but not both currents at the same time. In addition to this, current only can only flow from the Battery terminal to the Load terminal. In case of use with a load, the battery connects to the Battery terminal, and in case of use with a charger, the charger connects to the Battery terminal."
-- https://www.victronenergy.com/battery_protect/battery-protect