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Connection of two Battery Systems with BMS, different charger, temperature and shunt monitoring


for the connection of two Battery Banks i need a little help about which Product is for the application the best.

In my Truck I have two Battery Banks.

Bank 1 are 2x 260Ah Varta AGM 24V

Charger of this Bank is a 110A 24V Alternator (and a Victron Blue Smart 24/13A Charger every 2 times per month)

Loads are the Starter for the Engine and a small DC Air Condition.

To monitor Bank 1, i use a SmartShunt IP65 which is connected to the Cerbo

Bank 2 are 4x 200Ah (2 more are coming) Victron Lithium 24V Battery's.

Charger of this Bank is a Skylla i with 80 A

Loads are a Phoenix Inverter and smaller DC Loads

To control/monitor Bank 2, i use Lynx Smart BMS which is connected to the Cerbo

Case 1

While driving Bank 1 is charging by the Alternator with max 110A

When it's full, i want to charge Bank 2, when the BMS ATC (allow to charge)

Case 2

While standing Bank 2 is charged by the Skylla i with max 80A.

Bank 1 with 4A (second connection at the Skylla)

When it's full, i want to charge Bank 1, when the BMS ATD (allow to discharge)

Which product can manage bidirectional charging and is able to stop charging Lithium Bank (because low temperature) but allowed discharging at the same time?

Or charging but not discharging?

My quick and dirty solution is to use two relays and two diodes in parallel.

Relay 1 is connected to the ATC from the BMS and let with the diode current only from Bank1 (AGM)

to Bank 2 (Lithium)

Relay 2 is connected to the ATD from the BMS and let with the diode current only from Bank 2 (Lithium)

to Bank 1 (AGM)

To protect overheating Alternator, i build in a temperature sensor inside the Alternator which disconnect a third relay (AGM to Lithium)

This relay is connected to the SmartShunt as well and prevents too low discharging of Bank 1.

Please let me know if this ideal is brilliant, stupid, dangerous or not necessary because one product can handle this….

Best regards Robert

Robert asked
Robert answered ·

1 Answer

Two LFP battery banks

We have a sailing catamaran with two house banks of FLA batteries, one bank in each hull. The banks combine via a make-before-break manual battery switch (select bank 1, 2, both, or off). We plan to upgrade to LFP batteries but seek to maintain the two-bank arrangement such that, should one bank have a BTV fault, we can switch off that bank (maintaining system functionality with power from the working bank), while we work to isolate that fault or remove a faulty battery, etc. This could be done relatively quickly and without tearing apart beds to gain battery compartment access while sailing in rough seas at night (Because that is when things go wrong). Battery cable runs to the switch would be balanced in length. Both banks will be identical (2x 330aH smart LFP each). We would have a documented protocol for disengaging and engaging the banks to assure no charging and minimal loads during switching and to make sure the battery voltages are balanced between the two banks before recombining. The combining switch would be labeled with a warning to not change connections without first walking through the protocol. Normal operating procedure would be to run with both banks connected which we expect to be virtually a constant situation. Isolating a bank would only be done if absolutely necessary and after all attempts to correct the BTV fault without bank isolation are exhausted.

We currently have a Victron Energy (VE) Multiplus II, VE MPPTS, BMV-712 and a CerboGx. We plan to stay with VE components throughout, including the LFPs. We would use a Lynx Smart BMS as the BMS management device as well as battery monitor (retiring the BMV-712). The Lynx would be connected directly to the common contact on the battery combiner switch and all loads and charging devices connected downstream of the Lynx via 1-2 Lynx distributors. For the system to operate on a single bank we need to bypass the disconnected bank from the BMS monitoring. Unless someone has a better suggestion, I would simply disconnect the BMS extension cables connecting the two banks in the BMS daisy chain and connect the working bank cable direct to the Lynx.

We would use DVCC charge control to provide ATC control of the Multiplus and the MPPTs and supply power to the loads via BatteryProtects controlled by the ATD signal. We will implement Wakespeed WS500 regulators, following the Lynx integration protocol to assure protection of the alternators from LFP charging loads and protection of the batteries with the Lynx ATC connection to the WS500s.

We would of course follow all other safety protocols for LFP including class T fuses at each battery and appropriately sized conductors and fuses/breakers for each load and charging source.

We would appreciate constructive input on this concept, especially that which is useful to safe implementation. Thank you.

mkgsail asked
kevgermany answered ·

1 Answer

Low SOC Alarm- Battery Level is Fine

Hi everyone.

I am getting a Low SOC alarm from my Lynx BMS, even though the battery levels are well above 50% when the alarm trips. It's happening over and over after I reset the alarm.

Has anyone experienced Low SOC alarms seemingly for no reason?

Is there a way to disable these alarms for my client? He is concerned about the alarm, even though the system is working just fine.

Here's the setup:

Full Victron Power System

  • Victron Batteries (200ah x 3)
  • Victron Lynx BMS
  • Victron Lynx Distributor
  • Victron Multiplus 3000
  • Victron MPPT 30 Amp
  • Victron Cerbo GX and Display

I also have a Wakespeed controller for my dual alternator setup which is connected to the Lynx BMS. I'm wondering if the Wakespeed connection is causing the problem.

Thanks in advance, any help is appreciated.

van-land asked
Daniël Boekel (Victron Energy Staff) answered ·

4 Answers

BMS Cable type

I have an Easysolar 11 48/5000 and Pylontech US 5000 batteries

1 The BMS cable I have is W10SCAN30RJ1 is this correct?. Other information specifies a special cable.

2 A voltage sensing cable is supplied there is only one terminal but 2 wires and the connection is impossible to reach with a screwdriver. I this wire needed or is there an internal connection on the Easy Solar 11

delta5 asked
nickdb answered ·

1 Answer

100/30 Mppt allowed to charge via VE Direct?

Hi Guys,

Long time lurker, first time poster.

I’ve noticed on the older VE Bus BMS schematics there is usually a Cyrix relay between the Smart Solar MPPT and the main system bus. Now with the Lynx Smart BMS the same connection is direct. Does this mean there is now an ,”allowed to charge”, signal from the BMS via the VE direct cable? Or is there something else that I’m missing here?

Thanks in advance.


harris-marine asked
klim8skeptic answered ·

4 Answers

Skylla-IP65 Charger Control

I'm planning a system that includes a Lynx Smart BMS, a Cerbo, and a Skylla-IP65 charger. In the Specifications section of the manual it says "Li-Ion Charge Curve: 2 stage, with on-off control or VE.Can bus control."

I understand the part about on-off control wired to ATD on the BMS.

The "or VE.Can bus control" part suggests that the BMS can take full control of the Skylla including charging current and voltage without need to hardwire the ATD connection. Do I understand this correctly? Is this the same as DVCC?

Rob asked

0 Answers

Lynx Smart BMS settings, Number of batteries in parallel

I have Lynx smart BMS connected to a 48V system with 8 batteries 24V 200Ah. This is 4 parallel branches with 2 batteries in series in each branch. Can somebody confirm that my setting in the Lynxs are correct?

I setup the system as



4 batteries in parallel

If this is correct, I believe the setting should be called "number of parallel battery branches" as opposed to number of batteries in parallel. Number of batteries in parallel is confusing when you have combination of series/parallel batteries.


chelo122 asked
chelo122 answered ·

2 Answers

Lynx Shunt VE.Can did not shut down MPPT charger due to High Battery Temp

A terminal fault in the battery caused one string to overheat, received battery over temp alarm however had to disable solar charger manually as the BMS did not shut off charging. This would have caused the batteries to severely overheat. Does the BMS in the Lynx shunt not provide this failsafe?

wysiwyg asked
wysiwyg commented ·

5 Answers

Victron Lynx Smart BMS 500

Has Victron-energy not considered supporting 3rd party battery makers on its lists via can-bus link. Such as pylontech, so that this could be apart of a lynx bus bar system. Instead of as I am planning having too use the lynx smart shunt.

As the lynx smart bms can be firmware updated but not the other!

gunzenbomz asked
gunzenbomz edited ·

1 Answer

Solar charger before or after bms?


I'm just building a system with the following devices:

LiIon 200ah/25,6v smart, lynx bms, cerbo gx, smartsolar 150/35, quattro 5000...

I'll be using the bms relay as a remote main switch, does it make sense to connect the solar charger before bms (using a Cyrix LiCharge for safety) to keep the battery charged while the boat is not in use?

Will the ATC contact be positive even if the remote port on lynx bms is open?

Thx for your help!

alfred0905 asked
Stefanie (Victron Energy Staff) answered ·

4 Answers

ATD control wiring - Lynx Smart BMS to Orion DC-DC converter

I'd like to configure the "Orion-Tr Smart Isolated 12/12-30" in "Power Supply Mode". Charging functionality is not needed.

To make sure that Orion is stopped discharging the battery when battery SOC is low, i intend to connect grey part of the "Orion-Tr DC-DC Charger Isolated remote cable" ( to the Orion Remote On/Off sockets and the yellow and black cable to the Lynx Smart BMS 500 ATD socket (Pin 5 & 6). Cable to pin order does not matter.

Is this wiring correct?

Thank you very much,

flare1000 asked
flare1000 answered ·

1 Answer

Issues with Lynx BMS going into Safe mode , limiting charging

Hello Id be super grateful if there were any ideas on the below.

We are in a very remote part of the south pacific with almost no internet bandwith about to leave on a 4000 miles passage in the southern ocean to Cape Horn. I have a bout 10 days to try and get this sorted and downloading firmware if needed would need to be done on a satellite terminal, so any suggestions , ideas or thoughts before we start burning up airtime would be great

The system was working perfectly and now The Lynx BMS is doing some weird stuff and not functioning correctly when it get to 100% and hits Absorption mode.

System setup:

Lynx Smart BMS 500 serial number Hq21232t9qp; firmware V1.04

Set to 24V

realy Mode Alternator ATC

Absorption time 5 min ( this was changed so I could get a better undersatning of hat was happening

(3) 200 ah smart Li for a total of 600ah in 24v

Cerbo GX –firmware 2.90-22

Wakespeed WS500’s Firmware v2.5 and then back to v2.43

There are two wakespeed 500 set ups on the boat. One controlling the high out put 24v alternator on the DC Generator and controlling the 120amp 24V second alternator on the propulsion motor.

Around when I update to WS firmware 2.5 and GX 2.8 for the enhanced features just before I left Panama for the Galapagos I noticed that while charging once the batteries got to100% and at the end of Absorption time the Wakespeed dumped the field and disconnected instead of going into float voltage @ 27.2V as it had been..

The system charges normally or as you would expect it to getting to 100% SOC , At 100% SOC the voltage increases to 28.4 and the amperage drops from 90 Amp or 180 amps depending on the system to <10 amps, as it should. It then sits there for the Absorption period, until it try to go to float.

If I turn off the motor , and then restart it - the BMS /wakespeed will run but at a very slow pace, and a field of no more the 50% with max voltage of 26.8. When loads are turned on , it slowly ramps up and slowly ramps down to compensate. I was convinced it was the WS 2.5 firmware., I got ahold of Al at WS and we spoke about it , he seemed to think it was the BMS and that it sounded like the BMS was putting the WS into get home mode Or safe mode what ever you want to call it . The fact the voltage output was 26.8 and max field of 50% where the key indicators to him. AL sent me 2.43 via email which had worked previously .. I uploaded 2.43 and it continues to do the same thing.

Whats leads me to think it is a BMS issue is If I turn the power off at the Lynx BMS , and reset the system, then start the engine I can charge normally again with the alternator. The field come straight up and does the amperage, until we get to 100% SOC, and finish the absorption cycle , then the problem shows up again.

I then noticed it was doing the same thing with the Smart Solar controller that is networked via the GX device that is being controlled by the BMS. For example if I charge the system with the motor or generator to 95 % SOC and let the solar controller run and toke it to 100% it does the exactly same thing. Once the it gets into absorption it shuts down the solar controller , I see voltage 65 +- but no amperage output (displayed on GX display). If I reset the BMS by cycling power , the solar controller starts charging again .

I have someone traveing to the Gmabier this week and they are bringing another BMS, but I would think this has to be software related as it worked and then all of a sudden it didnt.

I did notice at some point the firmware updated on the Lynx BMS , could that be it ?

Is there any way the cerbo GX firm ware could be causing the problem .

Anyone have any thoughts?

gringosailingexpeditions asked
ludo edited ·

11 Answers

Can I parrallel the the 25.6/200 with 25.6/200-a?

So, when looking through the community, I see a couple of posts regarding this question. However, with mixed responses.

I have an existing battery bank with 3 sets of 2 (48v) with the BAT524120410 (old revision).

I want to expand this to the maximum allowed by the BMS (5 sets in parallel). The new revision seems to be the one that's the best available for purchase (also it's lighter). Can I expand my existing 3 sets of 2, by adding another 2 sets of 2 of the new revision?

The conflicted answers came from

Where someone (non-expert) mentioned, a sales rep told them it's fine.

Here, an "expert answer" said it's probably not possible.

Before I buy these (unfortunately overpriced) batteries, I'd like to know for sure I'm not going to run into issues.

Additionally, from my understanding the limit of maximum 5 sets of batteries is caused by the BMS cable signal strength, is there anyway to create a bigger battery bank? Does the Cerbo GX support multiple Smart BMS so I can multiple banks?

Marco Nijholt asked
Stefanie (Victron Energy Staff) commented ·

1 Answer

Buck Boost vs Lynx Smart BMS for alternator charging

Hi, I am in the planning stages of my camper van conversion. 2023 Ford transit AWD LWB. I plan to have an all victron system: one 24v Victron 100ah battery, and charge it with shore power and alternator power (no solar). I won’t have a lot of access to shore power so alternator charging is my main charging source. For alternator charger, I am debating between buck boost 50a plus VE.Bus BMS or Lynx smart BMS. I saw from Van Land YouTube channel that they are charging their batteries using Lynx smart BMS. What’s the pros and cons of each approach? The prices are similar. Thanks for your help!

angeljia asked
angeljia commented ·

1 Answer

Do you need Orion Tr Smart with Lynx Smart BMS?

If you already have a Lynx smart BMS in your system, do you still need the Orion DC to DC charger to charge your house battery from the van battery/ alternator?

angeljia asked
Stefanie (Victron Energy Staff) answered ·

1 Answer

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