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Lifepo4 battery too cheap?


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12 minutes ago, MtB said:

 

The bod who bought the boat weirdly perceived me as some sort of technical wizard (gawd knows why) and the lithiums were part of my mystical unfathomable machinations and he wanted all trace of them removed before he collected the boat. So I have them here in my rain room at the hovel! 

 

 

Tbh, if I ever flogged my boat, I'd remove the lithium batteries plus related gear, and buy with three mid range lead acid batteries plus a suitable device to manage charging them from the alternator. Keep it all simple.

There are a fair few boaters who aren't fussed at all about lithium batteries, and I suspect that the presence of expensive lithium batteries and any associated gear might not be reflected in the sale price.

Also, the replacement boat probably wouldn't have lithium, so it might make sense to take that sort of gear with you.  

 

 

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1 minute ago, Tony1 said:

 

Tbh, if I ever flogged my boat, I'd remove the lithium batteries plus related gear, and buy with three mid range lead acid batteries plus a suitable device to manage charging them from the alternator. Keep it all simple.

There are a fair few boaters who aren't fussed at all about lithium batteries, and I suspect that the presence of expensive lithium batteries and any associated gear might not be reflected in the sale price.

Also, the replacement boat probably wouldn't have lithium, so it might make sense to take that sort of gear with you.  

 

Yes to all of that. Except the boat I sold was a 24v boat and my current two are 12v! 

 

So I have a 24v bank of lithiums all factory-enclosed in a nice case, bought from a breaker dismantling a vandalised EV in Cobham. The interconnects are factory-welded onto the terminals and separating the cells would make a right mess. So at the moment, it's being pressed into service as a door stop. 

 

 

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12 hours ago, Tony1 said:

I've set my BMV712 so that when the battery SoC rises to the target value (usually 85%), the internal relay on the BMV712 sends a 12v signal to all the chargers via a very small gauge wire, and that tells them to switch off safely, rather than just disconnecting the charge cable, which sounds a bit 'heavy handed'.

 

 

Does this mean you don't need a lead acid in the circuit, since the charge cables are always connected to the lithium bank?

Edited by 170968
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3 minutes ago, 170968 said:

 

Does this mean you don't need a lead acid in the circuit, since the charge cables are always connected to the lithium bank?

He has a LA connected to the alternator. The B2Bs pump current from the LA to the Li, and can be switched off. The solar is connected to the Li and can be switched off. So there is no LA directly in parallel with the Li, but it is in there somewhere. And I have no idea why I am answering his question for him.

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2 minutes ago, nicknorman said:

He has a LA connected to the alternator. The B2Bs pump current from the LA to the Li, and can be switched off. The solar is connected to the Li and can be switched off. So there is no LA directly in parallel with the Li, but it is in there somewhere. And I have no idea why I am answering his question for him.

I thought he had one of them BEP motorised switches in between the two? No idea why I am asking you this.

Edited by rusty69
BEP not BMS
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17 minutes ago, nicknorman said:

He has a LA connected to the alternator. The B2Bs pump current from the LA to the Li, and can be switched off. The solar is connected to the Li and can be switched off. So there is no LA directly in parallel with the Li, but it is in there somewhere. And I have no idea why I am answering his question for him.

 

What he said 🤣

 

Thanks Nick, I would have given the poor chap some ill-defined guff, but that was much more clear and concise. 

 

As I understand it, you cant take current directly from an alternator into a B2B charger (and then to the lithiums)- you need a lead acid in the setup. 

 

ETA- I'm not sure if this device allows an exception to that statement above. 

It looks as if it connects to the output of an A2B charger, and can then connects directly to the lithium batteries, and can thus manage the charging in a safe way for lithium batteries, without the need for a lead acid battery in the 'chain'. 

So an alternative to a B2B charger for some folks, maybe?

 

https://sterling-power.com/products/multi-chemistry-battery-charging-module

 

That said, I dont mind having a lead acid in the charging train- it feels like it gives a bit more safety in that if the lithiums are suddenly disconnected for some reason, the alternator isnt put at risk of damage. 

 

Edited by Tony1
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To add to the above, I've got my Cerbo controlling the alternator controller so on its Node Red dashboard, I've programmed in an button to disable alternator charging. Quite useful when I'm setting off for a cruise on a sunny day and the solar will fill the batteries by the time I stop, no need to burn diesel. Could probably achieve the same thing with most alternator controllers minus the Cerbo by just cutting power to it.

 

Still haven't got over the issue of the engine RPMs being dragged down too low when in gear at idle and charging though, Small Engine Mode on the Balmars just isn't enough. Think a proper Wakespeed is on the cards!

 

 

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27 minutes ago, rusty69 said:

I thought he had one of them BEP motorised switches in between the two? No idea why I am asking you this.

 

I heard that he does have a BEP switch, but its not involved in charging - apparently he uses that as an emergency disconnect for the loads,  if/when the voltage ever gets too low. 

Some say he even has a separate disconnect in the event of a high voltage event, but that one only disconnects the chargers, and leaves the loads working. 

The story goes that he bought a victron battery protect to act as a low voltage emergency disconnect, but then found that the thing doesn't work with inverters. Apparently he was fuming when he found that out.  

So the cunning devil used his new 'battery protect' as a high voltage disconnect instead (controlled by a BMV712), and he used his BEP switch as the low voltage disconnect.

At least that's what I heard.....

 

 

Edited by Tony1
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6 minutes ago, Tony1 said:

 

I heard that he does have a BEP switch, but its not involved in charging - apparently he uses that as an emergency disconnect for the loads,  if/when the voltage ever gets too low. 

Some say he even has a separate disconnect in the event of a high voltage event, but that one only disconnects the chargers, and leaves the loads working. 

The story goes that he bought a victron battery protect to act as a low voltage emergency disconnect, but then found that the thing doesn't work with inverters. Apparently he was fuming when he found that out.  

So he used the battery protect as a high voltage disconnect instead (controlled by a BMV712), and he used his BEP switch as the low voltage disconnect.

At least that's what I heard.....

 

 

Some people might wonder why he doesn't use the BEP as a high voltage disconnect too. 

 

Not me though. 

 

Your engine room sounds a bit like the bridge of the starship enterprise. 

Edited by rusty69
BEP, not BMS.
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12 minutes ago, cheesegas said:

 

Still haven't got over the issue of the engine RPMs being dragged down too low when in gear at idle and charging though, Small Engine Mode on the Balmars just isn't enough. Think a proper Wakespeed is on the cards!

 


Which Balmar do you have, the MC-618? If so I’m surprised that halving the field current isn’t enough. Depends on engine and alternator size, I suppose. We lose about 50rpm between in gear idle not charging, and ditto charging at 1/2 field current which is not too bad. I did up the idle speed slightly so it is at the minimum of 850 under load, and 900 not under load.

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30 minutes ago, 170968 said:

Thanks to all three of you! Funny how you all know each others setups so well.

 

Nick knows my setup pretty well because he very kindly advised me on how to wire it all. 

It got to the point of 'where do I connect that red wire?' .....

 

 

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2 minutes ago, nicknorman said:

Which Balmar do you have, the MC-618? If so I’m surprised that halving the field current isn’t enough. Depends on engine and alternator size, I suppose. We lose about 50rpm between in gear idle not charging, and ditto charging at 1/2 field current which is not too bad. I did up the idle speed slightly so it is at the minimum of 850 under load, and 900 not under load.

It's an old ARS-5, with the Cerbo disabling it when SOC hits 100% and then re enabling at 90%. I've set it up so the ARS-5 never goes into to float mode and always aims for 14v.

 

I've got idle speed at 1000rpm as per the engine datasheet, it's a 90a alternator run with the beltsaver switched on level 1 so it puts out around 70-80a. The engine's a 3 cylinder 30hp Isuzu, when in gear and charging at 40a, engine speed drops to 900rpm when it's very vibey and bounces around a lot, makes a racket. Don't really want to raise the idle speed further as it'll strain the gearbox...

Considering some sort of servo driven cam on the throttle to raise the idle speed when the charge current is above a certain threshold. Simple to do in software but not so much mechanically!

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11 minutes ago, rusty69 said:

Some people might wonder why he doesn't use the BEP as a high voltage disconnect too. 

 

Not me though. 

 

Your engine room sounds a bit like the bridge of the starship enterprise. 

 

To be honest the high and low voltage disconnects are only there because I have ex-EV batteries which dont have a built in BMS with an emergency disconnect. So they are the last-ditch emergency measures that you hope wont ever be used (other than me testing them).

But my SoC monitor also provides some protection, in that it will remotely switch off the chargers if the SoC gets too high.

The final protective measure is the normal thing of the charging profile set on the chargers, which will ensure that they go into float once the battery voltage gets to 14.6v. 

It looks horrendously complicated, and there are more blinking lights than the bridge of the Enterprise.

I think the electrical cupboard is now so complex it has become self aware, and its trying to absorb my intelligence. 

 

 

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2 minutes ago, Tony1 said:

 

To be honest the high and low voltage disconnects are only there because I have ex-EV batteries which dont have a built in BMS with an emergency disconnect. So they are the last-ditch emergency measures that you hope wont ever be used (other than me testing them).

But my SoC monitor also provides some protection, in that it will remotely switch off the chargers if the SoC gets too high.

The final protective measure is the normal thing of the charging profile set on the chargers, which will ensure that they go into float once the battery voltage gets to 14.6v. 

It looks horrendously complicated, and there are more blinking lights than the bridge of the Enterprise.

I think the electrical cupboard is now so complex it has become self aware, and its trying to absorb my intelligence. 

 

 

Why don't you have a BMS? They are pretty cheap these days, unless you demand a huge draw from them. I have both a BMS and a BEP on my setup.

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Just now, rusty69 said:

Why don't you have a BMS? They are pretty cheap these days, unless you demand a huge draw from them. I have both a BMS and a BEP on my setup.

 

They are Valence batteries, made for EVs. The idea was you put lots of them in a vehicle but you only need one BMS module, which is a separate item.

So they didnt fit a BMS in each battery because for the intended purpose, they didnt need one.  

You could install a BMS, there are a few videos giving some guidance, but I just didnt fancy it:

 

 

 

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30 minutes ago, cheesegas said:

Considering some sort of servo driven cam on the throttle to raise the idle speed when the charge current is above a certain threshold. Simple to do in software but not so much mechanically!

 

That was exactly my problem when we first got the boat, with the tumble drier on (steady 2kw draw) from the travelpower, it really dipped the rpm and made the engine struggle at tickover passing moored boat, belt squeaking a bit. I considered some kind of idle-upping device but never got around to it.

Now I use the travelpower going into the Combi with the current limit set at 4A (AC) and use "power asssit" for the rest which comes from the inverter mode of the combi. The alternator is only putting out 75A or so, the remaining 1/4 kw coming from the batteries. Which helps, but still rather slow. At least the load is shared between the two belts.

 

Of course it would be fine if I ran the tumble drier only from the inverter, fed by the alternator and the batteries, but that means running the inverter fairly close to its max for an hour or so, not sure if that is the best idea long term.

 

Just had a look at the MC-618 data sheet, even that fairly new regulator doesn't seem to do it well. The "Small engine mode" just reduces the field current across the rpm range, whereas what you want is only to reduce it at low rpm. It looks like the Wakespeed or the Alpha Pro III are the only ones that do it properly!

 

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27 minutes ago, Tony1 said:

 

They are Valence batteries, made for EVs. The idea was you put lots of them in a vehicle but you only need one BMS module, which is a separate item.

So they didnt fit a BMS in each battery because for the intended purpose, they didnt need one.  

You could install a BMS, there are a few videos giving some guidance, but I just didnt fancy it:

 

 

well to be fair there is a BMS inside the Valence, BMS being Battery Monitoring not Battery Management. In other words there is no disconnect. But there is balancing and SoC tracking.

Interesting video on the guts of a Valence though!

Edited by nicknorman
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10 minutes ago, nicknorman said:

Just had a look at the MC-618 data sheet, even that fairly new regulator doesn't seem to do it well. The "Small engine mode" just reduces the field current across the rpm range, whereas what you want is only to reduce it at low rpm. It looks like the Wakespeed or the Alpha Pro III are the only ones that do it properly!

Yep, there's no smartness to it, it just reduces the field across the RPM range. It knows the RPM too, via the tacho take off so it's a shame it's not more configurable. I don't like Balmar regs for lithium (without external control) as they can't sense battery current, only a guess at alternator output done by working out how much field current is used to maintain a certain voltage.

Wakespeeds are £££ but I think I'll have to plump for it as you can configure the load at low RPMs..

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2 minutes ago, cheesegas said:

Yep, there's no smartness to it, it just reduces the field across the RPM range. It knows the RPM too, via the tacho take off so it's a shame it's not more configurable. I don't like Balmar regs for lithium (without external control) as they can't sense battery current, only a guess at alternator output done by working out how much field current is used to maintain a certain voltage.
 

 

These things must be designed by people that have never owned a boat!

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1 hour ago, cheesegas said:

Yep, there's no smartness to it, it just reduces the field across the RPM range. It knows the RPM too, via the tacho take off so it's a shame it's not more configurable. I don't like Balmar regs for lithium (without external control) as they can't sense battery current, only a guess at alternator output done by working out how much field current is used to maintain a certain voltage.

Wakespeeds are £££ but I think I'll have to plump for it as you can configure the load at low RPMs..

They're now officially supported by Victron too...

4 hours ago, rusty69 said:

I get the impression every man and his dog has lithium batteries on their boat now. I reckon the trailblazers are those that installed them 5 years ago. 

 

You just need to look on the 12V boating Facebook page to see hundreds of people adopting the hybrid approach and relying on the BMS and a long length of cable (unfused?) to do all the work. 

Lots of people are doing this, and it works fine in the short term. In the long term it's almost certain to reduce battery life, which given their cost seems like unwise penny-pinching to me.

 

AFAIK none of the FB bods have had a hybrid setup running long enough for this to show up...

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