Lithium hybrid set up help required

[nicknorman]

6 minutes ago, MtB said:

You're both overlooking the point of keeping a LA in parallel, which is nice simple way to save the alternator in the event of a high voltage automatic disconnect. 

Not overlooking it, but it is of course a factor. However if you have a smart alternator regulator, why would you have a high voltage automatic disconnect? And there are other ways of dealing with that problem such as Sterling's alternator protection device https://sterling-power.com/products/alternator-open-circuit-protection-device Not expensive

I suppose this is one reason why I am glad I went for bare cells rather than a battery with built in BMS - the BMS behaviour is controlled by me, not by some anonymous software engineer in china.

[IanD]

31 minutes ago, nicknorman said:

Not overlooking it, but it is of course a factor. However if you have a smart alternator regulator, why would you have a high voltage automatic disconnect? And there are other ways of dealing with that problem such as Sterling's alternator protection device https://sterling-power.com/products/alternator-open-circuit-protection-device Not expensive

I suppose this is one reason why I am glad I went for bare cells rather than a battery with built in BMS - the BMS behaviour is controlled by me, not by some anonymous software engineer in china.

Posts that cross in the night... 😉

 

The real problem with Li batteries (and even more so with Li+LA) is that people hope or believe that they can just drop them into an existing system (e.g. dumb automotive alternator+cheap solar/charger) and their battery/charging problems will be magically fixed without spending much money -- and blogs and web videos are partly to blame for this. They're wrong, and there are a lot of dead batteries and alternators out there to prove it... 😞

 

https://marinehowto.com/lifepo4-batteries-on-boats/

 

"I do not believe LiFePO4 is ready for mass DIY prime time builds. Read with caution, and especially focus on the things that you don’t want to hear rather than only what you want to hear."

"Frustratingly only a few of the cases of destroyed LFP batteries we’ve been contacted about are getting reported in on-line in forums, on blogs, groups etc.. The folks who’ve ruined these LFP batteries are not all boaters. Some are electric vehicle guys, many are RV owners, a few of them were off-grid and the rest are boaters. "

"Drop-in batteries will be a huge part of the future of LFP, and there are currently a few good manufacturers working to improve the marine specific shortcomings but, in my opinion, many of them are still not prime time ready, so purchase carefully. "

"The Sterling Power Alternator Protection Device is an inexpensive insurance policy against a BMS load dump destroying your alternator. If you can afford to purchase drop-in LFP batteries you can also afford to protect your alternator from a BMS load dump."

 

The bare cells+custom BMS comment is interesting, because that's exactly what some "do-it-right" hybrid boatbuilders do (e.g. Finesse) for exactly the same reasons... 😉

Edited February 5, 2022 by IanD

[ditchcrawler]

15 minutes ago, nicknorman said:

Not overlooking it, but it is of course a factor. However if you have a smart alternator regulator, why would you have a high voltage automatic disconnect? And there are other ways of dealing with that problem such as Sterling's alternator protection device https://sterling-power.com/products/alternator-open-circuit-protection-device Not expensive

I suppose this is one reason why I am glad I went for bare cells rather than a battery with built in BMS - the BMS behaviour is controlled by me, not by some anonymous software engineer in china.

I think you will find Mr Stirling doesn't recommend it for that duty

[StephenA]

6 hours ago, Murflynn said:

 

..... or keyboard warrior.

 

Never been called a keyboard warrior since I started working in software development back in 1989. I think a keyboard warrior is something completely different. I have been called a code monkey in the past though.

[nicknorman]

48 minutes ago, ditchcrawler said:

I think you will find Mr Stirling doesn't recommend it for that duty

Do you mean for regular use in a system where the BMS regularly shuts off the battery when it gets fully charged? In which case I’d agree with you. But surely for a once in a blue moon event when something goes wrong, that is what it is there for.

Edited February 5, 2022 by nicknorman

[ditchcrawler]

59 minutes ago, nicknorman said:

Do you mean for regular use in a system where the BMS regularly shuts off the battery when it gets fully charged? In which case I’d agree with you. But surely for a once in a blue moon event when something goes wrong, that is what it is there for.

Right first time. 

[nicknorman]

2 minutes ago, ditchcrawler said:

Right first time. 

Fair enough, but any Li installation that relies on the BMS over-voltage shut off for day to day operation, is an incredibly badly designed system doomed to a short life.

Edited February 5, 2022 by nicknorman

[IanD]

10 minutes ago, nicknorman said:

Fair enough, but any Li installation that relies on the BMS over-voltage shut off for day to day operation, is an incredibly badly designed system doomed to a short life.

Which takes us back to where we started, the mistaken idea that you can easily drop-in a lithium battery to an old-tech lead-acid electrical system...

Edited February 5, 2022 by IanD

[rusty69]

There is a group  on facebook who advocates the lithium hybrid setup which seems to rely on the BMS to 'Isolate' the lithium batteries from the lead acids, on each charge cycle. This method then allows the charge source to continue charging the lead acid batteries once the lithiums are suitably charged.

 

I just wondered what the assembled experts think of this method, as quite a lot of people seem to be adopting it, particularly in regard to the longevity of the BMS.

Edited December 10, 2022 by rusty69

[MtB]

15 minutes ago, rusty69 said:

There is a group  on facebook who advocates the lithium hybrid setup which seems to rely on the BMS to 'Isolate' the lithium batteries from the lead acids, on each charge cycle. This method then allows the charge source to continue charging the lead acid batteries once the lithiums are suitably charged.

 

I just wondered what the assembled experts think of this method, as quite a lot of people see to be adopting it, particularly in regard to the longevity of the BMS.

 

 

I agree it seems to be gaining currency as THE way to do it. 

 

The assembled experts on here have regularly condemned it as stoopid but the tens of thousands of cheapo drop-in lithium batteries being sold these days all appear to do it, most using that ubiquitous Overkill BMS, and no problems seem to get reported.

 

 

 

P.S. Got a link to the FB group you are seeing this on, please? 

 

[rusty69]

2 minutes ago, MtB said:

 

 

I agree it seems to be gaining currency as THE way to do it. 

 

The assembled experts on here have regularly condemned it as stoopid but the tens of thousands of cheapo drop-in lithium batteries being sold these days all appear to do it, most using that ubiquitous Overkill BMS, and no problems seem to get reported.

 

 

 

P.S. Got a link to the FB group you are seeing this on, please? 

 

It's called '12 volt boating group'.

[MtB]

5 minutes ago, rusty69 said:

It's called '12 volt boating group'.

 

Oh thanks. I'm in that already. It's a right bear garden. 

 

There are a couple of groups devoted specifically to LiFePO4 bat trees. I wondered if one of those was any better.

 

 

Edited December 10, 2022 by MtB

[rusty69]

1 minute ago, MtB said:

 

Oh thanks. I'm in that already. It's a right bear garden. 

 

There are a couple devote specifically to LiFePO4 bat trees. 

 

 

I've no idea what a bear garden is. Is it like a beer garden I wonder.

 

I've got the ubiquitous overkill/JBD BMS on my setup too,but just wondering if the new perceived wisdom was to solely rely on one.

[nicknorman]

2 minutes ago, rusty69 said:

I've no idea what a bear garden is. Is it like a beer garden I wonder.

 

I've got the ubiquitous overkill/JBD BMS on my setup too,but just wondering if the new perceived wisdom was to solely rely on one.

Well nobody quite knows, but IMO the purpose of the BMS disconnect is to protect the battery from immediate damage so routinely taking it up to that point may shorten its life. Of course the life is very long, so even  in life to 50% will take several years to manifest. The wisdom seems to be that early drop-in replacements had a short life/early failures and it seems likely that routinely relying on the BMS disconnect could be one reason. I don’t know how the BMS disconnect works, but presumably during a long cruise at some point it reconnects when the cell voltages naturally drop a bit, resulting in the battery being absolutely rammed full, which is bad for it.

 

I lasted 2 days on the 12volt boating group and then got banned for suggesting that a refractometer was in many ways an easier way to measure battery sg than a floaty thing. Dissent from the groupthink is not allowed.

[rusty69]

4 minutes ago, nicknorman said:

Well nobody quite knows, but IMO the purpose of the BMS disconnect is to protect the battery from immediate damage so routinely taking it up to that point may shorten its life. Of course the life is very long, so even  in life to 50% will take several years to manifest. The wisdom seems to be that early drop-in replacements had a short life/early failures and it seems likely that routinely relying on the BMS disconnect could be one reason. I don’t know how the BMS disconnect works, but presumably during a long cruise at some point it reconnects when the cell voltages naturally drop a bit, resulting in the battery being absolutely rammed full, which is bad for it.

 

I lasted 2 days on the 12volt boating group and then got banned for suggesting that a refractometer was in many ways an easier way to measure battery sg than a floaty thing. Dissent from the groupthink is not allowed.

 

The JBD BMS is configurable in that you can select the cut off voltage (s), so if it is set to say 14V will cut off the Lithium cells and not reconnect until it has reached the reconnect voltage, which is also configurable. This should prevent the lithiums reconnecting to the charging circuit when the engine is running. I assume the BMS is FET based, and it is likely the failure of one or more of these will result in the overall failure of the device. But how they fail, and what the MTBF is, I don't know, or even if this MTBF is based on using the BMS as a charge termination device.

 

Wow, you lasted 2 days. Impressive. I'm surprised you lasted that long TBH.

[nicknorman]

4 minutes ago, rusty69 said:

 

The JBD BMS is configurable in that you can select the cut off voltage (s), so if it is set to say 14V will cut off the Lithium cells and not reconnect until it has reached the reconnect voltage, which is also configurable. This should prevent the lithiums reconnecting to the charging circuit when the engine is running. I assume the BMS is FET based, and it is likely the failure of one or more of these will result in the overall failure of the device. But how they fail, and what the MTBF is, I don't know, or even if this MTBF is based on using the BMS as a charge termination device.

 

Wow, you lasted 2 days. Impressive. I'm surprised you lasted that long TBH.

What I hate about Facebook… well, one of the many things I hate about Facebook, is that once banned from that group it ceases to exist. It’s not just that it’s there but I can’t access it, it is completely invisible. Horrid thing. Dangerous thing in fact, because it is easy to see how it can be used for indoctrination and radicalisation regarding subjects somewhat more significant than boating electrics. Surround yourself only with people who agree with you and you start to think that that is the only way to think.

 

Back on the subject, I think MOSFETS are likely to fail due to passing high currents / getting hot. There is no “wear” related to actually switching.  Even moderate voltage spikes on the gate can be destructive, but unless the circuitry is designed really badly this shouldn’t be an issue.

Edited December 10, 2022 by nicknorman

[MtB]

3 minutes ago, rusty69 said:

 

The JBD BMS is configurable in that you can select the cut off voltage (s), so if it is set to say 14V will cut off the Lithium cells and not reconnect until it has reached the reconnect voltage, which is also configurable. This should prevent the lithiums reconnecting to the charging circuit when the engine is running. I assume the BMS is FET based, and it is likely the failure of one or more of these will result in the overall failure of the device. But how they fail, and what the MTBF is, I don't know, or even if this MTBF is based on using the BMS as a charge termination device.

 

Wow, you lasted 2 days. Impressive. I'm surprised you lasted that long TBH.

 

 

I've just ordered a drop in battery with the Overkill wossname in it too, and I too was planning to set all my own voltages etc. But I will also fit an isolator switch like in the boat I recently sold and monitor it manually as the main control. The BMS will just supervise and step in if it decides I'm not paying attention. 

 

 

[nicknorman]

9 minutes ago, rusty69 said:

 

The JBD BMS is configurable in that you can select the cut off voltage (s), so if it is set to say 14V will cut off the Lithium cells and not reconnect until it has reached the reconnect voltage, which is also configurable. This should prevent the lithiums reconnecting to the charging circuit when the engine is running. I assume the BMS is FET based, and it is likely the failure of one or more of these will result in the overall failure of the device. But how they fail, and what the MTBF is, I don't know, or even if this MTBF is based on using the BMS as a charge termination device.

 

Wow, you lasted 2 days. Impressive. I'm surprised you lasted that long TBH.

Oh and coming back to the point, IMO there should be independent 2 levels of control, ie one normal control system to charge the Li “nicely”, and then a second level of “emergency disconnect” if things go wrong. If you just rely on the BMS a single failure could damage the batteries. Depends on how lucky you feel.

[rusty69]

Just now, MtB said:

 

 

I've just ordered a drop in battery with the Overkill wossname in it too, and I too was planning to set all my own voltages etc. But I will also fit an isolator switch like in the boat I recently sold and monitor it manually as the main control. The BMS will just supervise and step in if it decides I'm not paying attention. 

 

 

Oh, which supplier you get it from?

 

The isolator switch seems like a great idea for 'switching off' the lithiums but I suppose some care must be taken that the LA batteries are nearer fully charged then fully discharged before reconnecting them. I suppose you could disable the 'charging' function in the BMS before doing so, but given human error is what it is you (or rather I), am likely to forget.

 

Do you foresee any problems with switch contacts deteriorating using this method?

8 minutes ago, nicknorman said:

 

Back on the subject, I think MOSFETS are likely to fail due to passing high currents / getting hot. There is no “wear” related to actually switching.  Even moderate voltage spikes on the gate can be destructive, but unless the circuitry is designed really badly this shouldn’t be an issue.

 

That's interesting. I wonder if a computer fan might make a good addition to a battery box. Actually, come to think of it, I seem to recall you added one to your set up?

[rusty69]

3 minutes ago, nicknorman said:

Oh and coming back to the point, IMO there should be independent 2 levels of control, ie one normal control system to charge the Li “nicely”, and then a second level of “emergency disconnect” if things go wrong. If you just rely on the BMS a single failure could damage the batteries. Depends on how lucky you feel.

I've got one of these motorised switch things separating my batteries, but the majority of people seem (if you believe facebook) to be relying on just the BMS.

[MtB]

7 minutes ago, nicknorman said:

What I hate about Facebook… well, one of the many things I hate about Facebook, is that once banned from that group it ceases to exist. It’s not just that it’s there but I can’t access it, it is completely invisible. Horrid thing. Dangerous thing in fact, because it is easy to see how it can be used for indoctrination and radicalisation regarding subjects somewhat more significant than boating electrics. Surround yourself only with people who agree with you and you start to think that that is the only way to think.

 

Totally agree with all that.

 

But just get another alias and use that if you really want to read the12V group. It will drive you demented though as the majority of posts are short on detail and badly informed. Unlike here the format is horrendous and I find it really difficult to find decent content in amongst the dross. I'm probably too short on patience to learn to operate the platform....

 

 

[rusty69]

1 minute ago, MtB said:

 

Totally agree with all that.

 

But just get another alias and use that if you really want to read the12V group. It will drive you demented though as the majority of posts are short on detail and badly informed. Unlike here the format is horrendous and I find it really difficult to find decent content in amongst the dross. I'm probably too short on patience to learn to operate the platform....

 

 

I find it hard to use too, particularly reading through any comments that have been made. It seems really difficult to navigate.

[nicknorman]

Just now, MtB said:

 

Totally agree with all that.

 

But just get another alias and use that if you really want to read the12V group. It will drive you demented though as the majority of posts are short on detail and badly informed. Unlike here the format is horrendous and I find it really difficult to find decent content in amongst the dross. I'm probably too short on patience to learn to operate the platform....

 

 

Yes that is another thing I hate about Facebook, having to constantly click to view more comments and there is no thread organisation. I did create a new alias but unless you populate it with some dross, a photo etc people think it’s just a sock puppet account and don’t let you in. So I wasn’t let in. You probably need to invest time posting multiple links to cats doing funny things etc, and have lots of “friends” (even though you never met them) to be accepted.

4 minutes ago, rusty69 said:

I've got one of these motorised switch things separating my batteries, but the majority of people seem (if you believe facebook) to be relying on just the BMS.

Well that is good, we will get to know whether that is a good idea or not, eventually. Well except that they will be banned if they reveal that the groupthink is faulty!

[IanD]

8 minutes ago, rusty69 said:

I find it hard to use too, particularly reading through any comments that have been made. It seems really difficult to navigate.

FB isn't meant to show you everything you need to know or make it easy to find stuff, it's purpose is to surround you with like-minded people and posts and maximise the time you spend on it to pull in targeted advertising revenue.

 

You're the product, not the customer...

Edited December 10, 2022 by IanD

[MtB]

10 minutes ago, rusty69 said:

I've got one of these motorised switch things separating my batteries, but the majority of people seem (if you believe facebook) to be relying on just the BMS.

 

 

Oh that reminds me, prior to flogging the other boat I was hatching a plan to install two of the highly configurable Overkill BMSs in series, to provide exactly this function. One I would set to do the day-to-day controlling, and the other given more extreme settings (e.g. lower and higher disconnect voltages etc) to step in if the main day-to-day BMS fails. 

 

So the operating envelope of the day-to-day BMS lies wholly inside the (larger) backup BMS envelope.

 

The main problem with this I can imagine would be getting one's phone to look at the D2D BMS with Bluetooth, not the backup one. 

 

 

 

 

Edited December 10, 2022 by MtB
Missing word