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The BMS knows the battery configuration so it corrects cell IR for the number of cells in parallel. But in the manual calculation I did earlier I did not and you are right: the individual cell IR is 0.50 mOhm (twice nominal value!). The difference is that the BMS only calculates IR under load...

Thank you all for your input. So after all my cells may not be as bad as I thought :) I'll keep investigating on the cell connection side... if / when the event happens again. I will measure cell voltage at the terminals as well as the terminal temperature. Then I will clean and redo the...

Yes balancing is independent from the BMS protection and energy management functions. But when the event occurred the cell voltage was too low to allow balancing. Just did that with 110 A load. Measured from cell terminal top to cell terminal top using a Blue Sea multimeter (1mV is the limit...

I did that on the first occurrence (a few months ago) and DMM reading were the same as reported by the BMS... but I did not record the measures in my log book :( If it happens again that will be the first thing I do and record data for reference.

Max load is the boiler with 110A load. All cells react the same way. Before load: 8.35 A charge - cell voltage from 3.280V to 3.289V (9 mV range) 3.5 seconds after applying 106 A load: cell voltage from 3.252V to 3.259V (7 mV range) Which approximate the cell IR between 0.245 and 0.262 mOhm...

Good idea... but that is a lot of work getting the battery out from where it is in the boat. Will do it tomorrow. The first 3 years for that battery was in the tropics (> 30°C) with a very basic BMS that did not control the chargers to stop charge at lower SOC . So I guess there must be some...

Thanks for the suggestion. I have plenty of sense wires in stock so I will replace with a new one.

Thanks @sunshine_eggo and @Skypower for your suggestions - that helps me in my thinking... and come to a conclusion. I use the BMS I have designed and sell: the TAO BMS The condition corrected by itself before I cleaned the connections. I cleaned the connections as, at that time, I did not...

Hi, On my boat I have a 600Ah DIY 12V bank with Winston cells installed 6.5 years ago (cells with sequential serial numbers). The cells are well top balanced and yesterday the voltage for one of the cells dropped suddenly by more than 100mV compared to the other cells... then later came back to...

My understanding is that absorption time exists to compensate the fact that most chargers cannot use the voltage + tail current criteria to stop charging. But some BMS can use those criteria to declare the battery full: minimum battery voltage (I use 13.8V) maximum tail current (I use 0.025C)...

I have been thinking about that for a while from a technical point of view (less on the cost and ease of installation) and this is what I came up with based on my readings and experience as EE. For most (all?) "drop-ins", each battery has its own independent BMS that will disconnect the...

Very good point raised by @Steve_S This is the cause of so many questions I receive like "why the charger goes to float before the battery is full?" In addition you must take into account that this voltage drop (loss) is not constant (proportional to the current)... and that makes it a...

I created that table for my own use, so I thought it might be a good idea to let others benefit from it. I am sure there are many more latching relays on the market and I welcome references I can add to this table. Click here for information on a newly released latching relay driver: TAO...

I had a look at the user manual, but it does not give much information on communication with the outside world. I did not find any mention of CAN bus there is a remote control port (ref 10 on page 4), but no details further! there is a BMS port (ref 14 on page 4), then on page 16 they say...

Added graphs

replaced the link with a PDF to download

Temperature is an important parameter that influences the aging of a lithium battery. At 35°C a lithium cell ages twice as fast as it does at 15°C. So if the battery’s useful life is 15 years at 15°C, it will be 7.5 years at 35°C. I summarize some research results and draw guidelines to better...

If you have not yet purchased your BMS, you can check the comparison chart I prepared trying to be objective based on information each vendor provide. Of course it all depends on the functionality you are looking for. If you want a worry free BMS that can manage the whole installation (including...

You may want to add TAO BMS to that list - see the comparison chart I did... BMS comparison chart

When power is first applied to a capacitive load (like inverters and chargers), a large inrush current is induced. This current creates an arc between the relay contacts… that are severely damaged. For that reason capacitive loads need to be pre-charged with a controlled current. TAO BMS can do...

For unplugged storage, the best is to charge to 50%, then disconnect all wires (including the BMS) from the battery, and keep the battery in a cool place. Like in your case, my system is also always on even if not on board for a long time (going overseas). Depending on location and length of...

When installing a lithium battery on a boat or a camping car you need to decide if and how the alternator will charge it at the same time as the starter battery. If not done the right way the alternator could be damaged. In this article I address some key questions you may ask yourself, I point...

Usually the "comm" you mention is done via CANbus. The BMS is the equipment that is closest to the battery and knows best what is required to optimize and protect it. It instructs the chargers with charge voltage / current, and the inverter on max discharge voltage / current. A few situations...

I fully agree with you that the BMS should shut down the battery only if all other warnings and corrective measures have failed... and give a lot of warning before it does. Instead of using multiple external systems, you can use a BMS that can do all of that on top of the basic protection /...

I do not know the functionality of the SMBS0, but Installation on a boat has some requirements that are different from a land installation: it could be unsafe if the BMS shuts down the battery in certain situation (no VHF, no lights, no autopilot..) so the BMS must give sufficient warning at...

In addition to the BMS listed above, the TAO BMS also supports the Victron CAN messages straight out of the box (as explained by @jwelter99). It has also the possibility to define custom messages to communicate with other equipment (or adapt to future capabilities)... as long as it is within...

Except for bluetooth, the basic version of the TAO BMS does exactly that. I see you are installing on a boat (like myself), so you will want to have advanced warning before external relays are activated (ABYC recommendation and common sense for the safety of the boat). TAO BMS has a led and...

Never been so close to the polar circle, the environment must be grandiose, but I guess it gets very cold most of the time. If temperature is below 32°F / 0°C, your BMS will be all the time in low temp cutoff and the battery will be useless. You may want to look at a BMS where you can set...

You can add TAO BMS to that list. You definitely need the Cerbo GX. Based on the conditions (cell voltage, temperature, SOC) the BMS sets max voltage / max current for charging, and min voltage / max current for inverter discharging. Have a look at the resource: BMS comparison chart

Some resources on this Forum... BMS Comparison chart Contactor (EMR) or Solid State Relay (SSR)?

Thanks, I am not in a rush and will wait a bit for the product to stabilize... keeping an eye on this thread.

First time I hear about the Chargery DCC. I rapidly went through the 20 pages of this thread and I may have missed some details. I am used to Electromagnetic Relays (EMR) and although temptation was great, I never installed a SSR on a charge or load bus... due to heat dissipation at high Amps...

added two examples that have good characteristics at a reasonable price point

It seems that you are going the integrated BMS route (the ones with integrated switching devices). I understand some can control charge and loads separately, but do not have experience with those and wish you to find what you need. I am used to BMS that control external switching devices...

Importants facts to be aware of when choosing a heavy duty switching device For both EMR ans SSR, I show specification examples. I highlight the specifications that are important to understand and that you should take into account when selecting a relay that will meet your installation needs...