Word of warning for LiFePO4 battery conversions (Battle Born)

[waninae39]

this is what my BB lion looks like

plugged into the 120 AC
victron 3k converter/inverter
solar on the rook with a BMV 712

the voltage goes up to 14.1V, then settles at 13.5V steady state

i used the parameters from victron for Lion batteries to set my system
it seems to work fine

[uncle_bob]

Originally Posted by waninae39

this is what my BB lion looks like

plugged into the 120 AC
victron 3k converter/inverter
solar on the rook with a BMV 712

the voltage goes up to 14.1V, then settles at 13.5V steady state

i used the parameters from victron for Lion batteries to set my system
it seems to work fine

Hi

The Victron numbers are for their version of lithium batteries. Bumping the high voltage end up by a bit is probably a good idea for the BB's. You don't want to go over 14.6, but you do want to get above 14.2 at the battery. 14.4 seems like a good compromise.

Why? The internal BMS in the BB's is triggered to equalize the cells when things get to some "magic" voltage. You don't have to do this very often, but it does need to happen occasionally. You want to keep things properly balanced between the banks of cells.

There is also no real need to do it *both* with solar and with shore. If you alternate back and forth between them a lot, having one or the other run up to the high voltage will do the trick.

Bob

[Rocinante]

Originally Posted by rickst29

...
And so, I 'm leaving the DIP switch on "Lithium"I still won't be leaving it "plugged in" all winter...

When we stored our AS last winter, we brought our Victron LiFePO4 batteries to a full charge and then turned everything off. Not just that phoney baloney "use / store" switch, mind you, but BRS (Big Red Switch) off. She was stored inside a building for the winter, so no solar either. Zero inputs, zero draws. Not even the jack had any current.

With zero draws over the winter, when we pulled it out in the spring to go camping we still had a full charge. We simply turned everything back on again, hitched up, and started our next round of adventures. With our system we had none of that slow discharge nonsense that haunts improperly tended lead-acid batteries while stored.

[uncle_bob]

Originally Posted by Rocinante

When we stored our AS last winter, we brought our Victron LiFePO4 batteries to a full charge and then turned everything off. Not just that phoney baloney "use / store" switch, mind you, but BRS (Big Red Switch) off. She was stored inside a building for the winter, so no solar either. Zero inputs, zero draws. Not even the jack had any current.

With zero draws over the winter, when we pulled it out in the spring to go camping we still had a full charge. We simply turned everything back on again, hitched up, and started our next round of adventures. With our system we had none of that slow discharge nonsense that haunts improperly tended lead-acid batteries while stored.

Hi

I saw the same thing. 13.4V going into storage and 13.4V coming out of storage.

Bob

[SilverHouseDreams]

Originally Posted by uncle_bob

Hi

The Victron numbers are for their version of lithium batteries. Bumping the high voltage end up by a bit is probably a good idea for the BB's. You don't want to go over 14.6, but you do want to get above 14.2 at the battery. 14.4 seems like a good compromise.

Why? The internal BMS in the BB's is triggered to equalize the cells when things get to some "magic" voltage. You don't have to do this very often, but it does need to happen occasionally. You want to keep things properly balanced between the banks of cells.

There is also no real need to do it *both* with solar and with shore. If you alternate back and forth between them a lot, having one or the other run up to the high voltage will do the trick.

Bob

Bob is very much right. The BB battery uses cells that should be charged to 3.6V minimum to 3.65V, in order to balance the cells. These are in 4-series, so 4*3.6=14.4 to get 100%, 4*4.65=14.6V. If you never get to 14.6V the BMS cannot balance the cells, and with ~160-200 cells you could easily have a few that slowly fall behind...and then they fail. The BMS works by bleeding excess voltage off, when a cell gets over something that BB picks over 3.6V the BMS drains off the voltage of the cell.


Now the other side of this is that the BMS is using small resistors to bleed off the excess energy as heat...so leaving it in “balancing” voltage range 24x7 definitely puts some wear on the BMS. Will it ever matter? Really depends on the details of the BMS, which BB doesn’t share.

[ROBERT CROSS]

I'm using the 14.4 BB recommends.

Bob
🇺🇸

[rickst29]

Originally Posted by uncle_bob

Hi
What did it do instead?

Lithium's run pretty much up to full charge at full current. The battery then drops way back and the load on the charger drops accordingly. Even if the voltage stays at 14.6V, the fans should stop spinning.

A lot of these chargers *do* stay at max voltage when set to Lithium. There isn't a lot of data, but it would appear that dropping back to around 13.5V *might* be a better approach.

Bob

During charge, at constant Voltage 14.6V, the current dropped from maximum down to zero over a period of about 15 minutes.

I put on some light loads, and IIRC the Converter did not come back "on" until battery (and DC Bus Voltage dropped) much lower than 14.6V. I don't remember the figure - but I will measure it and post another reply, when I get access the Trailer in setup for another trip (about 2 weeks). Good comment, good question!

[rickst29]

Originally Posted by Troutboy

Good info, but still wonder why folks don’t use the Orion DC/DC converter that Wulfraat keeps discussing. It works beautifully and solves this issue. Isolating the TV and TT systems is a must for a proper install.

I guess disabling the connection is one way to isolate the systems....

I didn't find the specific Victron "Orion" Model which creates a Lithium-compatible 'constant Voltage charging Voltage (14.6V). Renogy now sells a similar converter, and it includes DIP switch settings for battery type: https://www.renogy.com/renogy-12v-dc-to-dc-on-board-battery-charger. For other battery types, it is a 3-stage charger.

It's basically a DC-to-DC "Boost" Converter, followed by a PWM Solar Controller in the same box. Clever! But for power demand above 250 watts (which would necesitate the the "40A maximum output" model), you need to carefully consider whether the high input Current (approximately 50A) might burn your Bargman Cable. Because of that very possible disaster, I have been recommending only the 20A version.

Many years ago (before either of these products came into existence) I built my own: A Voltage Booster" under the hood of the truck (pulling "12V" from the battery on a dedicated big wire and circuit breaker), controlled by a dashboard switch. That converts the Bargman "12V" Battery Charge wire to 36V, at much lower current.

Then, in the Trailer, a "detector" Relay sees high Voltage on the incoming wire and controls a secondary "switcher" Relay. The "switcher" Relay disconnects the real solar panels from my MPPT Solar Input "+" terminal, and connects from the bargman "trailer battery charge" wire instead. The MPPT sees the input as a 520W Solar Panel, but it's only allowed to put out about 480 watts maximum (via the programmable maximum MPPT battery output current).

That's important, because the MPPT must never try to pull more than 80-90% of the Boost Converter's maximum current capability. A genuine Solar Panel doesn't get hurt by high demand from the MPPT (which will take all that it can get), but the boost computer would be fried.

My way is better, with 1/4 - 1/3 as much current on the Bargman and Tow Vehicle "Battery Charge" cables. (Much less heat, much less power loss). My way is also better for SLA and AGM battery users, because the MPPT Controller should already include a Battery Temp Sensor. And my way costs much less, when you already own a good Solar MPPT.

But my is complicated and time-consuming, adding lots of Relays and Corresponding control wiring into both the Tow Vehicle and (to a smaller extent) the Trailer.

[rickst29]

Originally Posted by ROBERT CROSS

I'm using the 14.4 BB recommends.

Bob
🇺🇸

That can work OK, but it's the absolute bottom of Trojan's recommended range for their Trilliums (14.4 - 14.8V). The Trillium BMS may be better than the BB BMS, when subjected to high voltage for an extended period, but 14.6V is the sweet spot, right in the middle of the recommended range. And Battle Born agrees that 14.6V is excellent, I asked them.


14.6V provides a bit more headroom for the BMS to re-balance the low cells at the end of charging cycles. Fully completed re-balancing is a key factor in extending the lifespan of our '4S' batteries.

[uncle_bob]

Hi

There will always be small differences in how people design BMS setups. You can play with bleed resistors. You can do capacitor based switchers to balance charge. There are lots of options. The key is being able to specifically program in what *your* battery wants. This is rarely "run at high voltage all the time". Getting it up and equalizing once in a while - fine. Doing that 100% of the time .... yikes ..... Give the poor BMS a rest !!!

Bob

[BAB]

I really sympathize with the guys at Battle Born. There are so many permutations in RV converter and charger equipment that it boggles my aging brain. My install went extremely well, and the set up was just a bunch of buttons to push on my controller. I continue to reap benefits from having installed the Magnum MSH3012 converter/charger. I thought $1,700 was very expensive when I installed it in 2016. But, I think it fits really well with the 4 Battle Borns. Taking my first long distance camping trip later this week, and I'm anxious to see how the new batteries perform.

[switz]

We have a heavily modifed 2015 23D International Serenity with five 100 watt solar panels and a 300 amp hour lithium battery. The heart of the system is the Magnum MSH3012.

I checked on the 23D in storage and the extension cord was showing power. I opened the door and there was no 120Vac or 12Vdc active in the coach. There was power coming to the new master 30 amp breaker but no further.

So I had to remove the street side dinnete seating area to get to the Magnum under it. There was 120Vac power on the input line. I discovered that the relay between the input and output wiring also interrupts the neutral wire continuity. After removing the MSH3012 from the coach, I wire nutted the three incoming and three outgoing wires together and had power in the trailer. We had a three way switch that interrupted the 120VAC power lead with Bypass the Magnum - OFF - Magnum. Bypass position did not have anything to do with the neutral which was interrupted by an open relay in the MSH3012. Thus even though we were in bypass mode, there was not a complete circuit.

Interesting wiring problem.

Thus the lithium battery was drained down and we had no 12Vdc.

[1919]

Please read the manual for the Victron Solar controller. Might want to put a piece of aluminum behind it. Should NOT be mounted directly to wood per the instructions.
I just used a 1/8" aluminum sheet, an inch bigger in each direction behind the Victron.
Just a word of caution.....

[1919]

You guys need a Victron Buck Boost system.
Please google it, they describe it better.
Separates the tow or chassis from the house.
AND will charge your lithium from the chassis, properly.
(therefore the boost in the name)
You are welcome..