Battery Condition

[noelex]

So you are saying that cheap batteries with a built in BMS is safe as long as it has BlueTooth communication and safer than a cheap battery with an internal BMS, no Blue Tooth. You are saying that a battery with Blue Tooth, obviously, monitors individual batteries whereas all internal BMS, without Blue Tooth, only look at the average, and do not react to the performance to individual cells.

Do you have examples, brands, to support this as I think specific data on which brands are safe, or not, would be invaluable.

Jonathan

All BMS units in even in the cheapest batteries monitor individual cell voltages. Lithium cells become permanently damaged if their voltage falls outside of a relatively narrow range, either too high or too low. A 12v battery is composed of 4 cells and if one of these cells falls outside the safe range then the BMS will shut the battery down to protect against permanent damage. It is one of the fundamental roles of a BMS. This will happen even if the total battery voltage is inside the acceptable range.

Knowing the individual cell voltages provides some warning that a cell voltage is approaching the shut down voltage. It also provides some insight into the health of the battery. Unmatched grade B cells will be more unbalanced. As the BMS is internal in these drop-in batteries, some form of external communication is needed to be able to monitor individual cell voltages. Bluetooth is the most common and least expensive system.

Even some quite cheap drop-in batteries are available with a Bluetooth equipped BMS. The BMS unit is essential and monitoring this data anyway so adding a Bluetooth transmitter is not particularly expensive.

In applications where an unexpected battery shut down can cause a safety issue or damage to other equipment (such as when installing these batteries in a yacht) a Bluetooth equipped BMS is sensible. Bluetooth communication with the BMS is also helpful in other ways. Some units will report the state of charge of the battery, the current in and out, the battery temperature (important in cold climates) the BMS temperature, if any balance current is activated, in addition to the individual cell voltages. These are all useful diagnostic tools.

Batteries with external BMS units (such as a DIY lithium battery) or the more expensive drop-in batteries that use a wired communication system don’t necessarily also need Bluetooth communication as all the data is available to an operator anyway. However, as Bluetooth is cheap to incorporate most will have this as standard.

 

[Neeves]

This

Battery breakthrough brings ‘unprecedented performance’ to next-gen cells — The Independent

Looks like it might be the start of bringing the size of sodium batteries down to equivalent lithium levels.

Coincidentally I noticed that China banned the export of graphite.

Graphite deposits are not very common and the article seems to suggest that the graphite needs process, its not simply a carbon rod, to achieve an improved performance for Sodium.

Lots of development work going on.

Jonathan

 

[Refueler]

Am I alone in thinking that OP's post has been 'forgotten' as we progress through the thread ??

I know this happens a lot - but here - the simple first post has degenerated (forgive the pun !) into the Lithium saga yet again.

 

[diverd]

I had an interesting battery day today. I tested all 4 of my batteries with a small computer tester that gives state of health and charge. They are the ones with the small green indicator and all 4 were showing good. I knew something was wrong, as the voltage was dropping way more than i would have expected. The computer tested showed 3 of the 4 failed, and i thought 1 would have been the problem. My large solar set up was hiding the problem during the day, but at night it was clear something was not right.
However, a mecanic friend with a boat not far from mine showed me something shocking. We crawled into his engine bay, he closed the hatch and we could see a blue static kind of line between the battery terminals. I have never seen the like before. Basically a charge is going from one terminal to the other. He says he was shown this years ago and its the salt environment that causes it. He also said if you lat a tube type bulb on it, it will try to light.
So we were losing power across the exterior of the batteries due to salt air contamination. He solved it with some silicon grease in moments, and i wish i had managed to check mine for this, but by this time they were all in a trolley to come home. Learn something new every day, my new batteries will be treated with silicon grease before they go in and i will check them from time to time.

 

[stranded]

Am I alone in thinking that OP's post has been 'forgotten' as we progress through the thread ??

I know this happens a lot - but here - the simple first post has degenerated (forgive the pun !) into the Lithium saga yet again.

That’s very kind of you - but I’ve learnt loads. Bottom line I think is that when two major parameters change it is very difficult to separate out the effect of one of them. So to test the impact of the change of use I need to start with known good batteries and see how things work out next summer.