Monitoring LiFePO4 Lithium Batteries

[sparrowhawk1]

Originally Posted by Maine Sail

I don't agree BMS balancing is not good or perhaps not necessary... In some cases it could be a good thing to have mid season to push your cells CAREFULLY into shunt balancing if they became out of balance.. I would not however aimlessly want someone to read the Chinese manual and think it is okay to continually push a bank to shunting levels every time they charge...

The House Power BMS can shunt but if you use the HVC function it will not be activated unless you do it manually because HVC cuts out before shunting level voltage is attained....

I keep my bank out of BMS range but I do believe in one as part of a safe and sound system design and to protect your investment..

I use it as an insurance policy above and beyond my system design because things happen especially on boats...

Thanks I'm on a little bit of a information overload it's hard to keep straight what everyone says

[goboatingnow]

My own view is that in fractional C systems, balancing isn't neccessary and overly complicates the BMS , which really is just needed for voltage limit protection.

It's also difficult to design good high power shunt balancing systems , several have failed in this.

It's important to keep in mind that out of balance cels aren't the end of the world, once you have cell level charge monitoring. A 10% imbalance , for example, can be " lived with", all it means is you loose some overall capacity in the bank until you rebalance. Small imbalances have little effect.

Where you are in high C discharge or trying to extract max capacity, then obviously balancing is important

Dave

[Hyprdrv]

I want to say thanks to everone posting on this subject. I'm starting to feel better about my gap of knowledge on this. Keep it coming!

Steve in Solomons MD

[campr]

I am going to be building my own Arduino based solution. It will incorporate an DC amp-meter, take samples every second of the current drawn, work out the SOC based on Ah consumed.

Then output the whole thing as an NMEA 0183 scentence to my logging system. It wil also detach the battery from loads as soon as a lower limit of remaining Ah is reached. I will be posting the hardware design and code on the internet dor other people to copy and improve upon.

[gael]

Originally Posted by sparrowhawk1

I also found one on ebay that shows voltage and amp hours at the same time and has a 100 amp shunt and goes for $40. There are also ones with higher amperage shunts for slightly more Sorry I don't know how to post links. But I googled 12 volt amp hour meters. and the eBay site came up

Hi sparrowhawk,

Two 130Ah/24V pack with CALB prismatic cells.
- BMS from Genasun. So with HV and LV alarms and cells balance.
- Two Victron BMV600 for Ah monitoring and HV and LV alarms.
Working since 2010.

Like to add two comments:
* Two different HV's and different LV's allow to separate the Alarm from the Action. Ie cut the alternator field before open the charge relay for HV or trig your attention before openning the discharge relay -and stopping your autopilot ect... for LV.
* LiPo is a superb technology, but with a bunch of electronic around. Potentially a weakness if you are hit by a strike. You should have the capacity to bypass all this stuff and connect directly to the cells.

cheers
gael

[sparrowhawk1]

[QUOTE="gael;1463329"]

Hi sparrowhawk,

Two 130Ah/24V pack with CALB prismatic cells.
- BMS from Genasun. So with HV and LV alarms and cells balance.
- Two Victron BMV600 for Ah monitoring and HV and LV alarms.
Working since 2010.

Like to add two comments:
* Two different HV's and different LV's allow to separate the Alarm from the Action. Ie cut the alternator field before open the charge relay for HV or trig your attention before openning the discharge relay -and stopping your autopilot ect... for LV.
* LiPo is a superb technology, but with a bunch of electronic around. Potentially a weakness if you are hit by a strike. You should have the capacity to bypass all this stuff and connect directly to the cells.

cheers
gael[/QUOTE

Working since 2010 that's great. This is something totally new to me I've been living with lead acid for 20 years. I don't even know the right questions to ask. The more specific about your BMS you can be the better. like how exactly does it cut off your chargers and loads. and anything that you think is important like I said I don't even know what questions to ask. Thank you.

[gael]

[QUOTE=sparrowhawk1;1464298
Working since 2010 that's great. This is something totally new to me I've been living with lead acid for 20 years. I don't even know the right questions to ask. The more specific about your BMS you can be the better. like how exactly does it cut off your chargers and loads. and anything that you think is important like I said I don't even know what questions to ask. Thank you.[/QUOTE]

Hi,
You will find a lot of information on the Genasun site. To be short
the BMS handle the 8cell monitors (for 24V) It checks individually every cells for V , température , balance and the full pack. The BMS controls two relay drivers . One the charge bus and one for discharge/service. Also there is an extra driver for auxilliary purpose that I dnt use.
So when the pack reachs its HV , the BMS open the charge relay, disconnecting the power sources.
Same when the pack reachs its LV , the discharge relay is openned cutting off the supply.
Both LV and HV are factory tuned for our cells. I have in mind 28V for HV and 25.4 for LV.
This is a true Bang Bang approach.
As the Victron monitors offers also an LV and HV alarm and relay drivers you set as you need. And all of them with hysteresis; This is a much more sophisticated. For the time bieng I just use the HV relay to cut the alternator field (I my mind 27.9V). I could also control in a same way the shore charger.
I have now only one solar pannel with a MPPT directly connected to one bank. I let the BMS handle the HV directly.
The alternator is a leece neville heavy duty w/o fancy regulation. Just trimmed to 28V. Delivering 65Amp non stop but badly hot (105C). It feed the 2banks via a FET isolator from Victron.
In parralel I have wired the shore charger; It is also victron Skilla 50Amp.
I have removed again all fancy regulation and set is as a "constant V source" trimmed to 28V. And I let the 50Amp current clamp regulates the current flow.

From my own mistake, if you have several banks, dnt put 2 banks in parrallel as several selectors allow the "1 + 2". I have blown up cables on my prototype connecting 2 unbalanced bank.
Also I dislike the self contained pack (cells and electronic), looking as a "standart" lead battery
If there is any software problem in the BMS ect.. you will be just trap. I fell much more confortable to have access to the cells.
Otherwise I feel this kind of battery to be much more simple to use compared to lead acid.
Cheers

[Maine Sail]

Originally Posted by gael

Hi,
You will find a lot of information on the Genasun site. To be short
the BMS handle the 8cell monitors (for 24V) It checks individually every cells for V , température , balance and the full pack. The BMS controls two relay drivers . One the charge bus and one for discharge/service. Also there is an extra driver for auxilliary purpose that I dnt use.
So when the pack reachs its HV , the BMS open the charge relay, disconnecting the power sources.
Same when the pack reachs its LV , the discharge relay is openned cutting off the supply.
Both LV and HV are factory tuned for our cells. I have in mind 28V for HV and 25.4 for LV.
This is a true Bang Bang approach.
As the Victron monitors offers also an LV and HV alarm and relay drivers you set as you need. And all of them with hysteresis; This is a much more sophisticated. For the time bieng I just use the HV relay to cut the alternator field (I my mind 27.9V). I could also control in a same way the shore charger.
I have now only one solar pannel with a MPPT directly connected to one bank. I let the BMS handle the HV directly.
The alternator is a leece neville heavy duty w/o fancy regulation. Just trimmed to 28V. Delivering 65Amp non stop but badly hot (105C). It feed the 2banks via a FET isolator from Victron.
In parralel I have wired the shore charger; It is also victron Skilla 50Amp.
I have removed again all fancy regulation and set is as a "constant V source" trimmed to 28V. And I let the 50Amp current clamp regulates the current flow.

From my own mistake, if you have several banks, dnt put 2 banks in parrallel as several selectors allow the "1 + 2". I have blown up cables on my prototype connecting 2 unbalanced bank.
Also I dislike the self contained pack (cells and electronic), looking as a "standart" lead battery
If there is any software problem in the BMS ect.. you will be just trap. I fell much more confortable to have access to the cells.
Otherwise I feel this kind of battery to be much more simple to use compared to lead acid.
Cheers

Unfortunately Genasun no longer sells just BMS units. They made a great one though......

[campr]

Originally Posted by Maine Sail

Unfortunately Genasun no longer sells just BMS units. They made a great one though......

Is this not it then? GLi-CP-1 | Genasun Sounds pretty much like a BMS to me, reading the specifications.

[Maine Sail]

Originally Posted by campr

Is this not it then? GLi-CP-1 | Genasun Sounds pretty much like a BMS to me, reading the specifications.

Yes but you can't buy one and it is not in-stock... That page is old and needs to be updated.. Trust me I have begged Bruce and Alex for one, but they now only come with a battery pack as a complete kit...

[ColdEH]

Hey Maine Sail , have you ever seen one of these in use?

EV Display - CleanPowerAuto LLC

Looks simple to use , I like simple

Regards

[OceanPlanet]

Originally Posted by Maine Sail

Yes but you can't buy one and it is not in-stock... That page is old and needs to be updated.. Trust me I have begged Bruce and Alex for one, but they now only come with a battery pack as a complete kit...

We get asked all the time...

[Maine Sail]

Originally Posted by OceanPlanet

We get asked all the time...

I know, I will probably ask you again next week..... Alex builds a sweet BMS!!

[ColdEH]

I actually found some good information on another forum on this

EV Display - CleanPowerAuto LLC

EV Display - Customer review thread - DIY Electric Car Forums

But it is not geared toward the boats , but should work the same for us.

Regards

[Maine Sail]

Originally Posted by typhoon

I actually found some good information on another forum on this

EV Display - CleanPowerAuto LLC

EV Display - Customer review thread - DIY Electric Car Forums

But it is not geared toward the boats , but should work the same for us.

Regards

It is an Ah counter really not much more. So is the Victron BMV-600 and it was designed for marine applications and has numerous programing options.I use a Link-Pro does the same thing as the Victron or the CPA EV Display...