Cheap LiFePO4 BMS?

[Richard10002]

9 hours ago, ivan&alice said:

Yes, the alternator side is definitely the tricky bit. @Richard10002 what are you using to disconnect your alternator?

Not much help to you here Ivan - At the moment I only use a generator for charging. As the sun is coming out, I'm currently thinking about adding my solar into the mix, which actually only means moving one cable, and resetting the controller. Given it was winter when I fitted them solar there was no urgency.

 

There is a chance that I wont use the alternator for charging..... I don't go far, so don't run the engine much, and it all sounds very complicated. I may use the inverter to power the charger as a work around, or maybe not.

[Richard10002]

8 hours ago, ivan&alice said:

Yeah perhaps I need one of these too. Going to see what I can get out of the GWL BMS before I drop the 170 GBP+ on the BMV 712! The main advantage seems to be to give you an easy-to-understand "fuel gauge" so you know your SoC rather than volts and amps.

If you have the Bluetooth version, you get SOC, Amps, Volts, Consumed Amps, and all kinds of other stuff if you want, on one screen.

 

If money is an issue, there is a cheap version that Will Prowse reviewed, which does not have bluetooth,

 

https://www.amazon.co.uk/Battery-Monitor-Voltmeter-Motorhome-Lead-Acid/dp/B07CTKYFTG/ref=sr_1_6?dchild=1&keywords=battery+monitor&qid=1586027397&sr=8-6

 

Not sure what happens if the current exceeds 100A. The NASA monitors just dont count it AFAICT.

 

 

[Tom and Bex]

5 hours ago, ivan&alice said:

 

Option 1 seems like the simplest and cheapest option then. Modifying the alternator seems more elegant. But why complicate things if there's no downside?

Not complicating things, if anything simplifying it by using separate alternator reg together with simple modification to alternator. Always feels a bit of a wrong to me switching high currents instead of controlling those currents at source, but lots do it with no problems. 

 

Quote

As I understand it the Li's are parallelised with the LAs, no split charge is needed since the LAs run at a lower voltage. It's OK (beneficial actually) for the LA to be taken to 100% while the Li's are still charging.

Depends what you mean by split charge. The way I see it working is the alternator(s) are permanently connected to the lead acid start battery, and the lithiums are connected to the LA start battery by a simple high power relay until full charge is reached, then the relay is simply switched off (by whatever method is decided on). As it's a straightforward relay, it could be easily controlled by a Victron BMV, or the voltage control board linked to earlier. If power taken from ignition switch, then would only be activated when ignition is on.

 

If using the voltage control board, would suggest connecting this to sense voltage from lead acid side, otherwise you risk it cycling. If sensing voltage from lithiums, then charge gets disconnected at set voltage point, voltage falls, board reconnects etc. If sensing start battery voltage, charge gets disconnected at set point, voltage on lead acid rises to alternator regulated voltage, relay stays disconnected until engine switched off. 

 

Id also consider a manual switch to force the relay on as we have (relay usually controlled from alternator controller). Maybe a brightly illuminated switch so you couldn't forget it! This would enable manual charging beyond the point it would usually terminate charge, option for emergency charging if control of relay fails, and importantly, option for starting engine from lithiums if start battery fails (we've used ours for this a few times when start battery failed on us).

 

Quote

Is this the downside? I would have to tackle the problem of the overheating alternator somehow, and a simple dump load won't help with that. Does anyone here actually use the dump load in routine use, or is it only in the case that the charging is shut off in an emergency?

 

 

Overheating of alternator not to be underestimated. I thought ours would be fine, but it lasted less than 8 months before burning rotor out. I think MP had problems as well. Cheap enough to replace an a127, but might not be for you depending on alternator model. We've used the settings on our alternator controller to reduce max charge from 90-100a, down to 70-80a (when both alternators connected), but only time will tell if this is enough. 

 

Can't see any long term problem to alternator or lead acid start battery if using as a dump load on regular basis. Not sure how long the relay would last though, guess it would depend on relay specs and charge current at time of disconnection. 

 

 

5 hours ago, Dr Bob said:

For me there is a downside.

I have 5 levels of safety on my system for most of the troubling stuff. So for instance take over charging. I manage mine in 5 steps

1) the charge sources cut back when the SoC is high enough.

if that goes wrong then

2) Alarms sound on the BMV to show over voltage

If that fails - or I dont hear it

3) the auto disconnect then disconnects at a higher voltage from the BMV

if that fails then

4) the BMS sounds an alarm for cell over voltage

If that fails  - or I dont hear it

5) the BMS activates the auto disconnect based on high cell voltage.

Mine has never gone wrong at level 1.

 

If you rely just on the BMS for auto disconnect then you are significantly reducing the safety net and you are reliant on the tyco switch to work all the time - and not just in emergency.

 

We don't have quite the same level of protection! We (only!) rely on 3 protection levels! Firstly our charge sources are set not to overcharge in the first place. Secondly we have the isdt bc-8s for monitoring cell voltages and providing alarms for cell over and under voltage, and cell differential voltage. Thirdly we have the bms as our last ditch protection, that cuts loads if a cell goes under 2.5v (reconnects at 3.0v) and cuts charge sources if a cell goes over 3.8v (reconnects at 3.4v). Finally, as a bit of an extra discharge protection, we have low soc alarm on the BMV set to 20%. 

 

The low soc alarm is the only protection that's activated on our setup, and that's because it has been so maintenance free, we forgot they would need charging when solar stopped providing our daily usage in October! The bms has never activated the high or low cut except in testing. 

 

We did have some cell differential voltage alarms initially when pushing charging to 100%, however I think that was down to insufficient balancing and being too impatient to get the cells installed! Following further balancing, and now following the addition of a battery balancer, we've had noi further issues.

[jetzi]

16 hours ago, Dr Bob said:

For me there is a downside.

I have 5 levels of safety on my system

Ok fair enough - the downside is one fewer layer of safety on the overcharging side. I'm all for more levels of safety, but it does seem that no one on the forum has ever needed more than one so far!

 

15 hours ago, Col_T said:

Don't all ammeters have shunts?

I was thinking of those ammeters that have an induction ring around the wire. Just wanted one on the charging and one on the load side, so I can see at a glance how much is going in/out of the batteries. Although if I shell out for a BMV I guess that won't be needed.

 

14 hours ago, Richard10002 said:

There is a chance that I wont use the alternator for charging..... I don't go far, so don't run the engine much, and it all sounds very complicated.

Unless you need to use the alternator, I think it would be wise to steer clear if you can. The alternator regulation seems by far the most complicated part of this endeavour - and the one most likely to go wrong!

 

14 hours ago, Richard10002 said:

If money is an issue, there is a cheap version that Will Prowse reviewed, which does not have bluetooth,

Money's always an issue I guess, but I'd be happy to spend money to get something that is really useful. At 180 GBP (from Bimble) the Victron BMV does seem expensive for what it is, but it's telling that even those who prefer Midnite or Mastervolt kit still recommend the Victron BMV.

 

10 hours ago, Tom and Bex said:

Not complicating things, if anything simplifying it by using separate alternator reg together with simple modification to alternator.

Arguably simpler conceptually, but not in the installation!

 

a) Hooking up a bistable relay to the BMS you already have (option 1)

vs

b) Doing the above (for emergencies) PLUS removing and dismantling your alternator, figuring out how to turn the alternator field off (or building programming and installing custom kit to regulate the voltage), adding an extra overvoltage board (and an alternator temperature sensor), and programming it. (option 2)

 

I'm not saying it's a bad idea, and I will explore this when I hook up the alternator - but it's a very intimidating job compared to (option 1) setting up the "emergency" shutoff relay!

 

 

10 hours ago, Tom and Bex said:

Overheating of alternator not to be underestimated.

 

This actually seems like the biggest reason not to go with option 1. Without any smart regulation of the alternator, how can you stop it from overheating, other than blowing a bunch of cold air on it? Here's a video on that topic, with the Victron recommendation (of course) be to buy a 600 GBP+ alternator! https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/

 

 

 

10 hours ago, Tom and Bex said:

Depends what you mean by split charge.

I meant a voltage sensitive split charge relay, like the one I currently have between my starter and 110Ah domestic LA battery. My understanding is:

 

In a simple circuit with a charge source connected to a LA and LiFePO fixed in parallel, the LA would fill first (being that it's at a lower voltage) and then the LiFePO would slowly increase the voltage of the whole system until we turn off charging. Then when discharging, the LiFePO will discharge first (since it's at the higher voltage). Therefore in most cases the LA will stay fully charged at all times. Am I right?

 

 

10 hours ago, Tom and Bex said:

the alternator(s) are permanently connected to the lead acid start battery, and the lithiums are connected to the LA start battery by a simple high power relay until full charge is reached, then the relay is simply switched off (by whatever method is decided on).

I think this will depend a bit on the method that is decided on, won't it?

 

If you use a high-current disconnect relay (option 1, and also the emergency for options 2 and 3), then yes permanently connecting the LA and alternator makes sense - the start battery will stay connected to the alternator and act as a load dump.

 

If you choose to turn off the alternator field (option 2), then overvoltage will turn off charging to the start battery as well (fine to do, since the start battery will be full).

 

If you regulate the alternator voltage to "float", then the LiFePOs will stop charging (since the float charge is less than their voltage) but the start battery (if it wasn't quite at 100%) could still take charge. Since the alternator is connected to the system any domestic loads could take power from the alternator.
 

[Dr Bob]

10 minutes ago, ivan&alice said:

Ok fair enough - the downside is one fewer layer of safety on the overcharging side. I'm all for more levels of safety, but it does seem that no one on the forum has ever needed more than one so far!

The 'paranoia' of 5 safety levels for me was more about protecting my 'huge' investment in LiFePO4s so I dont wreck them. Mine were only £1000 so I originally thought I HAD to do everything possible to safeguard my investment. I note your investement is <£700 which is only twice what you would pay for cheapo lead acids. We are starting to approach the point where it is unlikely you are going to wreck them (as long as you follow the rules) so why bother with 5 levels of of safety!

[Dr Bob]

17 minutes ago, ivan&alice said:

In a simple circuit with a charge source connected to a LA and LiFePO fixed in parallel, the LA would fill first (being that it's at a lower voltage) and then the LiFePO would slowly increase the voltage of the whole system until we turn off charging. Then when discharging, the LiFePO will discharge first (since it's at the higher voltage). Therefore in most cases the LA will stay fully charged at all times. Am I right?

 

That is a very simple way of looking at it.

If the engine start battery is almost fully charged then yes, that fits.....but not if it starts to get heavily discharged.

My system is slightly different as I have 660Ahrs of lead acids connected in parallel. Charging of the lead acids though is far from simple.

Think of a lead acid battery having 10 different types of active sites. When full and you apply a load, the first power that comes out is from the surface charge. The next 10% of the battery capacity is from the sites that are on the 'easy to get at' surface of the plates. The next 10% is sites that are slightly more difficult to get at. Once you get down to the sites active producing power when down to 50% full, you are using sites buried in the pores and quite difficult to get at. Ok, that is discharging.

On charging back up,  the first power put back in is to the top 10%, NOT the buried 50% sites and charging continues that way with the last sites to be filled being the buried ones. The important thing here is that to get those last ones filled, you need a good voltage ie 14.4V or more. This is why peeps have problems with sulphation because if you dont get back to full and I mean 100% then those few sites not converted back to lead will sulphate and not be available any more.

How does this concern charging with Li's? When you discharge Li/LA in parallel, current flows from both not just the LI. This may be just surface charge (or the top 10%) but if the LA are full to start with, it is easy to recharge the LA and I see that with my system...I have a BMV on the Li's and another on the LA. The problem will be though if you discharge the LA to 50% then the system will never see more than  14.0V so there will not be the driving force to get the buried sites converted back to lead. With my system, if I discharge the LA bank to anything below 90% (very rarely), when I can, I isolate the Li's and charge via the alternator at 14.4V to get the LAs full again.

None of this should affect you Ivan but I wanted to show that it is not as simple as your initial question.

[peterboat]

3 minutes ago, Dr Bob said:

That is a very simple way of looking at it.

If the engine start battery is almost fully charged then yes, that fits.....but not if it starts to get heavily discharged.

My system is slightly different as I have 660Ahrs of lead acids connected in parallel. Charging of the lead acids though is far from simple.

Think of a lead acid battery having 10 different types of active sites. When full and you apply a load, the first power that comes out is from the surface charge. The next 10% of the battery capacity is from the sites that are on the 'easy to get at' surface of the plates. The next 10% is sites that are slightly more difficult to get at. Once you get down to the sites active producing power when down to 50% full, you are using sites buried in the pores and quite difficult to get at. Ok, that is discharging.

On charging back up,  the first power put back in is to the top 10%, NOT the buried 50% sites and charging continues that way with the last sites to be filled being the buried ones. The important thing here is that to get those last ones filled, you need a good voltage ie 14.4V or more. This is why peeps have problems with sulphation because if you dont get back to full and I mean 100% then those few sites not converted back to lead will sulphate and not be available any more.

How does this concern charging with Li's? When you discharge Li/LA in parallel, current flows from both not just the LI. This may be just surface charge (or the top 10%) but if the LA are full to start with, it is easy to recharge the LA and I see that with my system...I have a BMV on the Li's and another on the LA. The problem will be though if you discharge the LA to 50% then the system will never see more than  14.0V so there will not be the driving force to get the buried sites converted back to lead. With my system, if I discharge the LA bank to anything below 90% (very rarely), when I can, I isolate the Li's and charge via the alternator at 14.4V to get the LAs full again.

None of this should affect you Ivan but I wanted to show that it is not as simple as your initial question.

What are you going to do on your new boat? I think the battery to battery charger is very elegant whilst expensive and with a blower may provide protection to your alternator 

[Dr Bob]

2 minutes ago, peterboat said:

What are you going to do on your new boat? I think the battery to battery charger is very elegant whilst expensive and with a blower may provide protection to your alternator 

Basically set it up as per this one with the Li's in parallel with the 440Ahr LAs that come with the boat. Initially I will use the BMV to monitor voltage and cut alternator charge at a set point via the BEP switch ....but that will be a day to day occurance not the emergency mode, plus put the temperature sensor from the BMV on the alternator and isolate the BEP when the temp gets too high. I will see how it goes in the very short term. The plan then is either to do surgery on the alternator and fit one of Nick's controllers - or buy a BtoB. As the alternator is 240A then the BtoB (at 120A) would be a simple (if expensive) solution.....but if I turn on the engine and it pumps in 120A to the lithiums then it will be full in an hour ....and the BtoB will have a customisable setting to turn off after the batteries get to 90%. I am not fitting solar as the alternator will cope and we can park under trees.

I have now disconnected all the wires and taken the lithiums off the current boat ready to put on the new one in May.

[MtB]

1 hour ago, ivan&alice said:

Without any smart regulation of the alternator, how can you stop it from overheating, other than blowing a bunch of cold air on it?

 

Cereal Tiller of this parish fixed a central heating boiler overheat protection thermostat to his alternators, which opened when the temp rose to 90c or whatever, interrupting the field current.

 

Very effective, he used to say. 

 

 

[peterboat]

1 hour ago, Dr Bob said:

Basically set it up as per this one with the Li's in parallel with the 440Ahr LAs that come with the boat. Initially I will use the BMV to monitor voltage and cut alternator charge at a set point via the BEP switch ....but that will be a day to day occurance not the emergency mode, plus put the temperature sensor from the BMV on the alternator and isolate the BEP when the temp gets too high. I will see how it goes in the very short term. The plan then is either to do surgery on the alternator and fit one of Nick's controllers - or buy a BtoB. As the alternator is 240A then the BtoB (at 120A) would be a simple (if expensive) solution.....but if I turn on the engine and it pumps in 120A to the lithiums then it will be full in an hour ....and the BtoB will have a customisable setting to turn off after the batteries get to 90%. I am not fitting solar as the alternator will cope and we can park under trees.

I have now disconnected all the wires and taken the lithiums off the current boat ready to put on the new one in May.

I like the idea of the B to B charger it won't invalidate the warranty on the alternator either I think I would still have the blower on  though with maybe the boiler switch Mike mentioned? I am glad my needs are met by solar with the occasional whispergen in winter 

[Dr Bob]

15 minutes ago, peterboat said:

I like the idea of the B to B charger it won't invalidate the warranty on the alternator either I think I would still have the blower on  though with maybe the boiler switch Mike mentioned? I am glad my needs are met by solar with the occasional whispergen in winter 

I will defo fit the blower and have ordered the boat with a 12V switched supply to somewhere near the alternator. It really did work well and kept the temperature down during the winter. I think the new boat will have far better ventilation in the engine 'ole as well. I am reckoning on the 240A alternator to be able to give out 120A for a few hours with decent cooling.

Most important tool for all of this is an infrequent red thermometer to measure alternator temp. Make sure you get one Ivan!

[jetzi]

On 04/04/2020 at 14:42, Dr Bob said:

I think the BG-8S is great. The numbers on the display are bigger than the Bc-8s so easier to read. I got a BG8s first and started to use it - then discovered it didnt have the high voltage alarm (IIRC it has the low voltage alarm only). I therefore found a BC-8s and bought one but never replaced the BG8S with it as the display is smaller. I would defo recommend the BG8S as the way to see all the cell voltages in one  simple display.

It's a bit of a shame that it doesn't have the high voltage alarm, that's almost more important given the complexities of charging. But as they are so cheap I'll get one for the low voltages. Will have to have a think about how I'm going to do the backup high voltage cell-level alarms.

[Dr Bob]

23 minutes ago, ivan&alice said:

It's a bit of a shame that it doesn't have the high voltage alarm, that's almost more important given the complexities of charging. But as they are so cheap I'll get one for the low voltages. Will have to have a think about how I'm going to do the backup high voltage cell-level alarms.

I think the BMV is the way to go. It gives you a lot of information....I think knowing Amps out, Ahrs out and voltage is essential in a simple one off package and can act as an alarm AND relay. Ok its nearly £200 but you are spending 10 times that. I think the BMV is probably the most useful bit of 'informative' kit on our boat.

My BMVs connected to a Rasp Pi so I can see all the power data on the internet inc remotely and it stores all the data so you can interpretate the data later and understand your power. Using this data to plot out graphs of voltage v Ahrs used or volts and Amps during charging etc you can set base lines for normal usage so simple to check where you are when charging or discharging. Because I check the Ahrs used each morning I know if I am going to even get near full charge so never really need the overcharge protection.

Edited April 6, 2020 by Dr Bob

[jetzi]

Placed my order for the solar. Got the BMV 712, it comes too highly recommended not to! I also got the ISDT BG-8S since it was only 28 GBP. Went with the larger 3kVA inverter, I didn't want to have regrets down the line. I got four of those Tyco 190A relays. Intention is to have one on the charge side and one on the load side, and a third on the whole positive. Those three connected to the BMS. And then a spare in case they burn out.

 

First phase - I'll hook the solar and MPPT up to my lead acid while I wait for my LiFePOs sometime this week.

Second phase - hook up the lithium to solar, then I'll report back on how the GWL BMS and relays work out.

Third phase - figure out the alternator charging.

 

Thanks for all the advice and help everyone, it's been so valuable!

[Richard10002]

7 hours ago, ivan&alice said:

Placed my order for the solar. Got the BMV 712, it comes too highly recommended not to!

My BMV is hidden away by the batteries and I rely totally on the bluetooth transmitted wirelessly to my phone. However, it has all kinds of alarms, which are loud enough to be irritating, and the ability to control a relay, so worth more than just a monitor. 

 

[Dr Bob]

10 hours ago, Richard10002 said:

My BMV is hidden away by the batteries and I rely totally on the bluetooth transmitted wirelessly to my phone. However, it has all kinds of alarms, which are loud enough to be irritating, and the ability to control a relay, so worth more than just a monitor. 

 

Yep, I hardly look at the meter as I use the mobile to look at the data when trundling along via Bluetooth and the iPad/Mac when moored up from the comfort of my chair .....via the rasp pi link. On our new boat I will bury the BMV in a cupboard rather than drill a big hole in the main panel and access it only remotely.

[MtB]

2 hours ago, Dr Bob said:

Yep, I hardly look at the meter as I use the mobile to look at the data when trundling along via Bluetooth and the iPad/Mac when moored up from the comfort of my chair .....via the rasp pi link. On our new boat I will bury the BMV in a cupboard rather than drill a big hole in the main panel and access it only remotely.

 

I'm not sure this is such a great idea, as it leaves you 100% dependent on having a working mobile with you on the boat, and a working BT adaptor too. 

 

If the bluetooth connection or the phone fails, I suggest it would be nice to be able to walk up to the BMV712 on the wall and see it and press the buttons, rather than have to take all the crap out of the cupboard and peer at it with a torch. 

 

Just another of my hobby horses, the fitting of essential equipment in hard-to-get-at places, when it didn't have to be that way

 

 

[Richard10002]

4 minutes ago, Mike the Boilerman said:

 

I'm not sure this is such a great idea, as it leaves you 100% dependent on having a working mobile with you on the boat, and a working BT adaptor too. 

 

If the bluetooth connection or the phone fails, I suggest it would be nice to be able to walk up to the BMV712 on the wall and see it and press the buttons, rather than have to take all the crap out of the cupboard and peer at it with a torch. 

 

Just another of my hobby horses, the fitting of essential equipment in hard-to-get-at places, when it didn't have to be that way

 

 

I’m sure that, after the first time the Bluetooth facility fails/isn’t available, for whatever reason, I’ll be uncoiling the cable and slotting the BMV unit next to the MT50, or the NASA and Smartgauge.

 

Until then, on the first occasion, it won’t be a very big deal to recover it to where the buttons can be pressed and the display read.

 

Having said that, I’d have to have the small print manual to hand as I won’t remember what to press and in what order  

[MtB]

6 minutes ago, Richard10002 said:

I’m sure that, after the first time the Bluetooth facility fails/isn’t available, for whatever reason, I’ll be uncoiling the cable and slotting the BMV unit next to the MT50, or the NASA and Smartgauge.

 

Until then, on the first occasion, it won’t be a very big deal to recover it to where the buttons can be pressed and the display read.

 

Having said that, I’d have to have the small print manual to hand as I won’t remember what to press and in what order  

 

Smartgauge? I don't think that's much use with Lithiums.

 

Or is it?

 

 

[Dr Bob]

11 minutes ago, Mike the Boilerman said:

 

I'm not sure this is such a great idea, as it leaves you 100% dependent on having a working mobile with you on the boat, and a working BT adaptor too. 

 

If the bluetooth connection or the phone fails, I suggest it would be nice to be able to walk up to the BMV712 on the wall and see it and press the buttons, rather than have to take all the crap out of the cupboard and peer at it with a torch. 

 

Just another of my hobby horses, the fitting of essential equipment in hard-to-get-at places, when it didn't have to be that way

 

 

Its on a £40 asda phone that lives at the back of the boat. Its on my phone too and even Mrs Bob has the Victon app on her phone.

Just as likely that BMV will fail as the BT on it! My iPad/mac is via wifi and LAN cable.

 

Mike you worry too much!

 

I agree with Richard. The first time it fails, it will be brought out into the open. Not failed in 3 years though.

[peterboat]

2 minutes ago, Mike the Boilerman said:

 

Smartgauge? I don't think that's much use with Lithiums.

 

Or is it?

 

 

My NASA isnt great with it either 

[MtB]

4 minutes ago, Dr Bob said:

Its on a £40 asda phone that lives at the back of the boat. Its on my phone too and even Mrs Bob has the Victon app on her phone.

Just as likely that BMV will fail as the BT on it! My iPad/mac is via wifi and LAN cable.

 

Mike you worry too much!

 

I agree with Richard. The first time it fails, it will be brought out into the open. Not failed in 3 years though.

 

It's just that I encounter it most days in my professional life. Commonly (or even uncommonly) failing components fitted in inaccessible places by installers who knew they would not be the ones mending it ten years in the future.

 

Your choice entirely, clearly! I was just saying, in case the thought hadn't occurred to you. 

 

 

[jetzi]

Question about initial battery charging.

 

As a CCer I don't usually have access to shore power and I can't plug my 3kVA inverter in until I power up my batteries. Nor do I have a "laboratory charger" as I've seen in videos where I can precisely set the charging voltage.

 

I do have a workshop battery charger that is marked 12.8V, 20A RMS, which I used to charge my domestic battery while I was in dry dock.

 

How did you guys do your initial charging and balancing of the cells? Did Jeremy supply them charged/balanced?

 

Should I either book myself into a marina to get shore power, or perhaps find a friend and do the initial work on land?

Will I need to buy a fancy lab charger that I can set to 3.55 volts?

 

Lastly would you recommend charging to 100% during this careful initial charging phase?

[Tom and Bex]

Mine came reasonably well balanced from Jeremy, but still needed more (and in initial installation, discovered they still weren't balanced enough). Definitely worth taking the tune to get initial balancing right 

 

I didn't have any special equipment, but followed the ideas on the http://nordkyndesign.com/ website, using a standard 12v battery charger. Think I checked iindividual cell voltages, got them as close as possible, then connected in parallel, and charged to 3.65v using my 12v charger, bit with very careful CONTINUOUS monitoring. That did rely on using charger via inverter and existing batteries though. 

[Dr Bob]

2 hours ago, ivan&alice said:

Question about initial battery charging.

 

As a CCer I don't usually have access to shore power and I can't plug my 3kVA inverter in until I power up my batteries. Nor do I have a "laboratory charger" as I've seen in videos where I can precisely set the charging voltage.

 

I do have a workshop battery charger that is marked 12.8V, 20A RMS, which I used to charge my domestic battery while I was in dry dock.

 

How did you guys do your initial charging and balancing of the cells? Did Jeremy supply them charged/balanced?

 

Should I either book myself into a marina to get shore power, or perhaps find a friend and do the initial work on land?

Will I need to buy a fancy lab charger that I can set to 3.55 volts?

 

Lastly would you recommend charging to 100% during this careful initial charging phase?

My batteries from Jeremy were reasonably balanced but needed more balancing. Tom's approach is the best - setting them all up in parallel and then taking them up to 3.65V with a 12V battery charger - keeping a very close eye on them. I didnt like the idea of changing all the 'shorting bars' on the batteries or taking off the aluminium bands so did it the hard way.

I put them in the 3P 4S config and charged until one cell reached 3.60V and then put them all under load to reduce voltage, then took power from the highest of the 3P cells via a resistor circuit ie taking 10A out for a set period of time. I then charged the bank till the highest got to 3.6V and then discharged that cell at 10A for a set period of time. After a few goes, it was easy to estimate the Ahrs needed to be removed to balance the cells. It takes more time than putting them all in parallel (took me around 3 days initially) but once done Ive only needed to do a couple of cell balances.

The other way is to put some power into the lowest cell - once the highest one is up to 3.60V - via the LA battery. Rig up some not too thick wire and run from the engine start battery to the cell in question - Use at least 5 metres of wire. Put a clamp meter on to monitor current and you can then put in a set number of Ahrs. I did actually buy a lab power supply that will do 10A at 3.65V which was around £100 IIRC.

It would make it much easier to go into a marina for 3-4 days to use the battery charger to do the charging. I doubt you could do it on solar - it would take too long. Maybe you could do it with your alternator but not when you dont know how the alternator is going to work with the LI's.