question

Tex260Z avatar image

LiFePO4 regulator settings & 3 port BMS connections???

@Justin Cook - Bay Marine Supply USA


I am still waiting for anyone to confirm I am correct on the new battery presets (which I have been told don't exist), (see pics attached).

Or am I missing something?

I also have had no reply in about 6 weeks regarding confirmation of my BMS connections being correct or otherwise, I am not comfortable proceeding with the final connection of the BMV-712 to the battery positive until I receive same.

I have marked up a picture with labels for for all cables, hopefully that makes it clearer.

I actually just followed former advice to another person put the shunt in the Blue Bat Neg cable here: https://community.victronenergy.com/comments/22867/view.html

I also included a picture of the battery & BMS before any connections for clarification.

Stay safe folks.

MPPT - Solar Charge ControllerBMV Battery MonitorBMS
10 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

3 Answers
nebulight avatar image

That looks okay to me as the only common negative back to the battery is the main connection from the BMS to the battery so your shunt placement makes sense. The current draw of the BMS is only 1ma so it would take YEARS to draw down the battery, so I wouldn't worry about having it installed after the BMS.

With that said, are you sure that BMS is spec'd high enough for the use of an inverter and solar for charging? I don't think those cheap BMS units are really designed for high current draw like an inverter and those 3 port units typically have VERY low charge current allowances. Those are typically used for higher voltage lower current eBikes. I just see the large size of your inverter wire compared to the very small wire going to the battery from the BMS. I would only ever consider using one of those with a 12v battery for very low current applications.

Also your charge settings look fine (conservative which is fine), but keep in mind those BMS' passive balance on the charge cycle at higher voltages. The BMS will never balance your pack, though they also have VERY low passive balancing currents anyway.

1 comment Share
10 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Hi nebulight,

Sorry for the delay in answering, been otherwise occupied.

Many thanks for that confirmation. I presume that was a typo when you said "BMS only draws 1 ma" you meant BMV, correct? And yes I was aware of that, that's why I picked the 712.

Regarding the BMS, it wasn't particularly cheap and it has pretty impressive numbers:

Constant discharge is 200 amps (peak 400 amps for 10 seconds). My 1500 watt Latronics inverter only draws 4500 watts max (5 second overload). I have test run our new 2400 watt induction dual cooktop for 45 minutes at full bore, no problem. No heat detected in leads or battery, very little drop in battery volts.

The BMS (Max) charging rate is 50 amps, as I only have two 195 watt panels (about 10.5 amps max) on the roof that is never going to be an issue.

My battery Standard charging current is (0.2C) = 40 amps, and Max charging current is (1C) = 200 amps. so all good there as well.

Yes the leads are pretty small on the BMS, that's why I made up the bus bars, but they don't even get warm at full whack.

F.W.I.W the battery specs are:

Max cutoff voltage is 14.6 (I am aiming for 13.5 - 14).

Low voltage cutoff is 10 volts (I am aiming for 12 volts).

In addition to the SmartSolar MPPT 75/15 and the BMV-712, I have a small BG8S balancer which I can plug in to the battery any time to check and correct the top or bottom balance, slow but works a treat (see below).

So today I finally finished installing the BMV-712 and plugged it in, fired up Victron connect on the new Motorola phone, no existing devices in the BT list, connect ok only to be greeted with the dread "Firmware update" (as usual). Run the update with the phone right next to the device, fails at 4% (3 times). So then I connect to the SmartSolar MPPT 75/15 no problem, once again to be greeted with the "Firmware update" requirement. Same scenario, fails at 4% three times, gives me a B8 error, (Timeout waiting for access to the Victron BLE service).

So then I try my old MPPT 50/10 with a BT dongle, and it runs the update on that no problem,

I have tried to find an explanation in all of the Victron documentation, but as usual with them it doesn't give an explanation of what the issue means, or how to fix it.

I suspect it might be a software issue once again, have you seen anything related to this in the last day or so?

lifepo4-battery-s.jpg (254.4 KiB)
Matthias Lange avatar image

The Shunt wiring looks ok, but be aware that the BMV is connected directly to the battery without the BMS!
That means that the BMV can still draw power out of the battery even if the BMS cut-off!
In worst case the BMV will pull down the battery voltage to less than 6.5V (1.6V/cell)!

For the charging setting you should look into the datasheet of the batteries/cells.

1 comment Share
10 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Thanks, I was aware of that.

I did ask at one point if it was ok to leave my Victron Smart charger attached full time in LiFePO4 storage mode when the van is not in use, and I was told that was ok.

I was wondering though if it would be better to connect it via the BMS, or just direct to the battery, I suspect the latter?

Stefanie avatar image

Hi @Tex260Z,

regarding the battery settings it would be best to either refer to the data sheet that came with your cells or ask the manufacturer of the cells. Same for the BMS.
But the LiFePO4 settings you chose, look ok so far. They do no harm to your battery.

With regards to the shunt connection a diagram/system schematics will be very helpful for us to see if your wiring is ok.

1 comment Share
10 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Hi,


The battery settings are way outside what I would be comfortable with to get a decent life out of the batteries:

Battery specs are:

Max cutoff voltage is 14.6 (I am aiming for 13.5 - 14).

Low voltage cutoff is 10 volts (I am aiming for 12 volts).

I was just interested to know what the Victron "200 Amp Hr LifePO4" settings actually were?

I think we agree that setting does actually exist, even though I was told it didn't.

1593665547623.png (1.4 MiB)