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Another Lithium battery thread


Dr Bob

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Just now, nicknorman said:

Yes there are two “separate” ground planes on the underside, one for the digital and one for the analogue. They join at that point simply by having 2 overlapping pads. There is a pin soldered in there, temporarily for test purposes.

Although of course the “analogue” pressure sensors have digital (I2C) outputs, so I just wanted to try to minimise noise in the vicinity of the actual sensors. When the 24 bit AtoD process is ongoing (10mS or so) I take care to avoid any I2C bus activity.

 

Noisiest thing I’m sure is the MAX3232 which uses charge pumps to generate +-5v from the 3v3 supply, for the RS232 interface. That is far left of the board.

 

Anyway good news is that the processor runs fine. I do have a problem with one of the sensors not working, I’ve taken it off and on again and can’t see a soldering issue so I think it must be duff. Third sensor is much bigger and through hole, yet to be soldered in and I have run out of time as leaving for the airport shortly to fly down to the boat (snow in Aberdeen permitting!)

It looks nice.

 

MP.

 

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14 minutes ago, nicknorman said:

As I’ve said, dead easy with solder paste and a hot air rework gun. Virtually impossible with a soldering iron!

Yeah but there’s not stacks there, you could have made it old-school with through-hole components. ;)

 

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25 minutes ago, WotEver said:

Yeah but there’s not stacks there, you could have made it old-school with through-hole components. ;)

 

Yes probably could, except the pressure sensors which are only available SM. But I think it may have ended up bigger. I chose to go for as much SM as possible as an experiment to see how it would turn out. So far so good.

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Just now, nicknorman said:

Yes probably could, except the pressure sensors which are only available SM. But I think it may have ended up bigger. I chose to go for as much SM as possible as an experiment to see how it would turn out. So far so good.

Yeah, I like it. The last thing I lashed up used a couple of relays and some diodes so I made it on Veroboard, but all the links made it messy. I’m now thinking of a project that could need a board making just so’s I can give smd a try. 

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11 minutes ago, WotEver said:

Yeah, I like it. The last thing I lashed up used a couple of relays and some diodes so I made it on Veroboard, but all the links made it messy. I’m now thinking of a project that could need a board making just so’s I can give smd a try. 

Well you can get 10 PCBs up to 100 x 100 mm for US$13 if you don’t mind waiting for Chinese snail post. Nearly cheaper than veroboard!

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2 minutes ago, nicknorman said:

Well you can get 10 PCBs up to 100 x 100 mm for US$13 if you don’t mind waiting for Chinese snail post. Nearly cheaper than veroboard!

I think that IS cheaper than Veroboard :)

 

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I've been asked to put together a lithium battery system for a friend's camper as he's been impressed with mine so far, so thought I'd share my ideas. Although only a low power system, with a change of relay or substitution for another cut off device, I think this may work quite well for a low cost install on a boat, with virtually no alterations needed to existing systems.

 

He likes to camp off grid for 2-3 days, and although generally low usage, does have a propex heater that he uses quite a bit, particularly in winter. Currently has a single 110ah sealed leisure battery charged with 50a alternator via split charge relay when driving, and with fixed battery charger at home. No monitoring of any sort, nor is he interested in any. Just uses battery until propex and lights no longer work! Generally gets 2 years out of batteries before replacement, but struggles to go more than 1-2 days without charging and hates running engine parked up. He's going to use the 2nd hand 160ah Thundersky cells from ev-support.co.uk which is what I and I think a couple others here have used.

 

I'm then going to use this battery protection board from eBay set up to connect the lithiums in parallel with the existing leisure battery when voltage is 12.8-14.0v (on the leisure battery). This should charge them to about 80% then cut off, leaving all loads running from the alternator whilst driving, and similarly cut back in when stopped to run from lithiums until voltage drops below 12.8 when the existing leisure battery will take over again. The final voltages used may be tweaked a bit with experience when setting up, and will be monitored during initial charge and discharge cycles to ensure optimum high and low voltage limits have been chosen. The connecting relay will just be a standard 70a automotive one such as this  as he only has a low power system. Finally, hidden away in a cupboard (as he refuses to have any monitoring!) will be the ISDT BC-8S battery monitor with individual cell monitoring and alarms for high and low voltage cells, and cell differential voltage (although no disconnect function). This will be connected via a 4 way fuse box such as this fitted with 1a fuses and this cable. All in all a basic and cheap, but hopefully reliable system that should give several trouble free years use. Total cost just over £30 excluding cells and wiring. With addition of a heavy duty relay or motorised battery disconnect switch, this system should also work well on boats with very little modifications to existing electrical installation. 

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1 hour ago, Tom and Bex said:

I've been asked to put together a lithium battery system for a friend's camper as he's been impressed with mine so far, so thought I'd share my ideas. Although only a low power system, with a change of relay or substitution for another cut off device, I think this may work quite well for a low cost install on a boat, with virtually no alterations needed to existing systems.

 

He likes to camp off grid for 2-3 days, and although generally low usage, does have a propex heater that he uses quite a bit, particularly in winter. Currently has a single 110ah sealed leisure battery charged with 50a alternator via split charge relay when driving, and with fixed battery charger at home. No monitoring of any sort, nor is he interested in any. Just uses battery until propex and lights no longer work! Generally gets 2 years out of batteries before replacement, but struggles to go more than 1-2 days without charging and hates running engine parked up. He's going to use the 2nd hand 160ah Thundersky cells from ev-support.co.uk which is what I and I think a couple others here have used.

 

I'm then going to use this battery protection board from eBay set up to connect the lithiums in parallel with the existing leisure battery when voltage is 12.8-14.0v (on the leisure battery). This should charge them to about 80% then cut off, leaving all loads running from the alternator whilst driving, and similarly cut back in when stopped to run from lithiums until voltage drops below 12.8 when the existing leisure battery will take over again. The final voltages used may be tweaked a bit with experience when setting up, and will be monitored during initial charge and discharge cycles to ensure optimum high and low voltage limits have been chosen. The connecting relay will just be a standard 70a automotive one such as this  as he only has a low power system. Finally, hidden away in a cupboard (as he refuses to have any monitoring!) will be the ISDT BC-8S battery monitor with individual cell monitoring and alarms for high and low voltage cells, and cell differential voltage (although no disconnect function). This will be connected via a 4 way fuse box such as this fitted with 1a fuses and this cable. All in all a basic and cheap, but hopefully reliable system that should give several trouble free years use. Total cost just over £30 excluding cells and wiring. With addition of a heavy duty relay or motorised battery disconnect switch, this system should also work well on boats with very little modifications to existing electrical installation. 

Two worries about the relay.

 

1) The continuous coil current will use quite a few precious amp-hours.

2) If the relay is closed during engine start, the lithiums are going to supply the majority of the starter motot current and way exceed the 70A rating. You may have to interlock with the starter circuit somehow.

 

MP.

 

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1 hour ago, MoominPapa said:

Two worries about the relay.

 

1) The continuous coil current will use quite a few precious amp-hours.

2) If the relay is closed during engine start, the lithiums are going to supply the majority of the starter motot current and way exceed the 70A rating. You may have to interlock with the starter circuit somehow.

 

MP.

 

1. I was initially concerned about this, but I've measured the coil resistance of a couple 70a relays I have and it's about 80ohm so less than 4ah a day at 13v. Considered using an economizer circuit, but decided it's not worth it for such a small drain. Granted it would be more of an issue if using the size relay needed for an average narrow boat install. 

 

2. Leisure battery is isolated from start battery using split charge relay wired (I presume but will check) via ignition warning lamp so only closes when alternator is charging. Worth bearing in mind though for a voltage sensing relay, as the voltage on the lithiums would probably keep it closed. Thanks for the warning, I need to double check split charge wiring now!

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4 hours ago, Tom and Bex said:

I was initially concerned about this, but I've measured the coil resistance of a couple 70a relays I have and it's about 80ohm so less than 4ah a day at 13v. Considered using an economizer circuit, but decided it's not worth it for such a small drain.

The hold-in current of a relay is generally a lot less than the pull-in current so you could implement a little timer to drop the voltage once it’s pulled in if you wanted. 

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32 minutes ago, WotEver said:

The hold-in current of a relay is generally a lot less than the pull-in current so you could implement a little timer to drop the voltage once it’s pulled in if you wanted. 

I think that’s what he means by an economiser circuit.

Edited by nicknorman
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  • 2 weeks later...

Just thought I would mention this, James who I bought my batteries from, has after a year checked all of the bank to see how they are fairing, he has an all electric boat. charging is taken care of by solar and whispergen, on plugging in the puter it turns out that all of the batteries have remained balanced with no BMS in use! So for me that seals the deal, restricting charging voltage to 13.8 volts is the way forward to long battery life with LifePo4s, and making sure you dont run them flat helps as well?

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9 hours ago, peterboat said:

Just thought I would mention this, James who I bought my batteries from, has after a year checked all of the bank to see how they are fairing, he has an all electric boat. charging is taken care of by solar and whispergen, on plugging in the puter it turns out that all of the batteries have remained balanced with no BMS in use! So for me that seals the deal, restricting charging voltage to 13.8 volts is the way forward to long battery life with LifePo4s, and making sure you dont run them flat helps as well?

Peter,

Can you remind us of what James is charging from and particularly which MMPT controller and its settings? Also what MPPT controller are you using and its settings?

I have now ordered 12*Thundersky cells (to be picked up later in Feb) and trying to dot 'I's and cross 'T's. I am trying to engineer the system so that the charge systems match the LiFePo's and follow the mantra of forgetting all there is to know about LA's. I have two MPPT's. One is a victron 100/15 and the other an older MPPT (supplier unknown) which can be set for an Absorbtion voltage of 13.8V and a float of 13.2V. The victron can be configured to a LiFePo setting but I am really concerned that the LiFePo setting on my Victron IP22 Bluesmart controller has an Absorption voltage of 14.2V and a float of 13.5V.  Everything I have read says charge to 13.8V (maybe 14.0V at a stretch) AND THEN TURN OFF...no float! The IP22 certainly wont turn off (and the Absorption voltage is too high anyway and likely too long). I worry that the Victron MPPT may be similar in that the voltage cant be reduced below 14V....cant find anything on the internet.....and it will have a significant time at absorbtion voltage. Do your (+ James) MPPT's get to 13.8V at the end of 'bulk' and then have 0 mins in absorption? I will buy a new MPPT if I need to.

I will post a description of what I am intending to build later today to get everyone's input.

 

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3 minutes ago, Dr Bob said:

Peter,

Can you remind us of what James is charging from and particularly which MMPT controller and its settings? Also what MPPT controller are you using and its settings?

I have now ordered 12*Thundersky cells (to be picked up later in Feb) and trying to dot 'I's and cross 'T's. I am trying to engineer the system so that the charge systems match the LiFePo's and follow the mantra of forgetting all there is to know about LA's. I have two MPPT's. One is a victron 100/15 and the other an older MPPT (supplier unknown) which can be set for an Absorbtion voltage of 13.8V and a float of 13.2V. The victron can be configured to a LiFePo setting but I am really concerned that the LiFePo setting on my Victron IP22 Bluesmart controller has an Absorption voltage of 14.2V and a float of 13.5V.  Everything I have read says charge to 13.8V (maybe 14.0V at a stretch) AND THEN TURN OFF...no float! The IP22 certainly wont turn off (and the Absorption voltage is too high anyway and likely too long). I worry that the Victron MPPT may be similar in that the voltage cant be reduced below 14V....cant find anything on the internet.....and it will have a significant time at absorbtion voltage. Do your (+ James) MPPT's get to 13.8V at the end of 'bulk' and then have 0 mins in absorption? I will buy a new MPPT if I need to.

I will post a description of what I am intending to build later today to get everyone's input.

 

No probs Bob, James has outbacks, I have two midnites, classic 200 series I can put you in touch with a dealer in UK/Spain who can flog you one. read up on them they can be set to whatever you want I consider them to be the best available

3 minutes ago, rusty69 said:

I haven't been following this thread, but am looking at theses mppt controllers, which say they are good for Lifepo4.

 

https://www.bimblesolar.com/offgrid/mppt/Waterproof-Tracer7810BP

Not big enough for me I have 3.6KW of solar

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27 minutes ago, rusty69 said:

I haven't been following this thread, but am looking at theses mppt controllers, which say they are good for Lifepo4.

 

https://www.bimblesolar.com/offgrid/mppt/Waterproof-Tracer7810BP

I am getting very confused with all of these 'good for LifePo'  claims!

The bumf on this charger says for LifePo bulk charging to 14.6v and a float of 14.4V. WTF!!!!!!!

How can you trust this info!

I see there is a 'user' voltage that can probably be set to anything for bulk and float, but then is there a time that the unit will hold at the peak voltage before it goes to float? It doesnt say if you can control the time spent in absorption and more importantly set that to zero.

Also I have 500W of solar so would need a slightly bigger one.

Thanks for the info anyway. I will check out Peter's link on the midnights.

Screen Shot 2019-02-01 at 10.42.49.png

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13 minutes ago, Dr Bob said:

Also I have 500W of solar so would need a slightly bigger one.

I have 1000 W. I was just gonna buy two controllers:)

 

ETA. I expect never to get 1000W out of my setup anyway.

Edited by rusty69
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38 minutes ago, peterboat said:

No probs Bob, James has outbacks, I have two midnites, classic 200 series I can put you in touch with a dealer in UK/Spain who can flog you one. read up on them they can be set to whatever you want I consider them to be the best available

 

The midnites seem to be well over the top for me. I only have 500W of power so looking for an MPPT that can cope with 40A max.

 

1 minute ago, rusty69 said:

I have 1000 W. I was just gonna buy two controllers:)

The two controllers I have now my be ok as long as they dont hold at the max voltage for a lengthy absorbtion period. I cant find any info on the Victron site about how far the voltages can be adjusted or how long it will hold at an adsorption voltage.

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MP, well done on getting your wiring done! Keep us posted.

Ok, an update on where I am. I have ordered 12*Thuderskys for pick up later in February. So now I need to sort out the rest of the system. I visited both MP and T&B over the past week and got a huge amount of vital information plus I have scoured the internet picking up all the important stuff including following Peterboat's postings on the various EV forums (well done Peter).

I spend a lot of time keeping my LA's in shape so reading bedtime stories to my new Lithium bank will not be an issue. My current cheapo LA's are now 2 years old and have circa 90% of the original capacity. In the summer, we are out all the time and we tend to motor for 2-3 hours each morning and then top up with 500W of solar in the afternoon keeping the LA's full at the end of each day and then using circa 100Ahrs overnight which needs replacing the next day. In winter, we are out 3 days a week with the rest of the time on shore power in a marina.

Our strategy for getting Lithiums is purely to stop having to run the engine to get the LA's up to full and not having to worry about getting to 100% all the time.

The plan then is to piggy back our current 660Ahr LA bank with circa 400Ahr + Lithiums as per the diagram in my first post. In the event of any disconnects during operation, the charge sources can then discharge into the LA's. All I need to do is connect the +ve of the lithiums into the +ve of the LA circuit via:

  • a manual isolation switch (likely a Blue Sea E series)

  • a 200A fuse (ANL)

  • an autodisconnect switch ( likely a BEP 701 mn motorised switch – but see below)

and connect the -ve of the lithiums to the -ve of the LA circuit via a BMV 712 shunt. That means not much change to the existing wiring – just need to add a lot more.

I will be aiming to ensure the charge sources (Alternator/MPPTs/Battery charger) work within the ranges of the Lithiums ie max voltage charge 13.9V and then turn off, but know this is going to be difficult. For battery management I will use the following:

  • The Aus unit that T&B have fitted. Viz http://www.zeva.com.au/Products/datasheets/BMM8v2_Manual.pdf which monitors individual cells and activates the disconnect switch on over or under voltage. This is an emergency cut out and will only activate as a final action

  • A voltage board to display all 4 cell voltages with audible alarms set lower than the Aus unit viz https://www.hobbyrc.co.uk/isdt-bg-8s-battery-checker This will therefore give me a warning before the Aus unit isolates the Lithium circuit

  • Use my BMV 712 to monitor high/low voltage and temperature to give I) a verbal alarm or II) to activate the disconnect switch.

I therefore have two levels of redundancy to disconnect the Lithiums on voltage and two levels of redundancy on audible alarms on voltage. I am relying only on one temperature audible alarm and disconnect though.

In terms of how I run the system, I need to ensure my charging systems are compatible. At the moment I am sure the alternator charger is not set up properly so the plan is to maximise charging via the solar and isolate from the alternator (manually) when the engine is running. I will therefore change the Solar input from the MPPTs to the Lithium side of the manual isolation switch. In the morning I will turn the manual isolation switch off so the Lithiums are only charged by the solar. Start the engine when motoring and the alternator will only be used on the LA's. When I stop the engine, I then reconnect the manual disconnect. I reckon I only use 25% of the power of the solar at the moment as every day we are out, the batteries are 95% full by the time we turn the engine off and the MPPTs have gone to float so loosing out. If we cycle our new lithiums from 80% SOC down to 20% (ie 250Ahrs), that is 2 days of use and with the solar putting max power available to it into the Lithiums (as they will now take full power and not in float) we should get a lot of that back. I reckon we will have the batteries in place by April so we will have 6 months to run this way before we start loosing the sun.

The alternator (90A) has a Sterling AtoB which will regulate the voltage down to 14.0V or even 13.9V BUT could have too long an absorption period which could move me up to the 'knee' which I want to avoid to minimise cell balancing (which I will do manually). With the alternator though I am more worried about it getting too hot with all this power it can deliver. For the first few months then I will try and scope out how the alternator is working monitoring voltage, currents and temperatures and seeing if it will charge the Lithiums safely and then if not, I know I will need to invest in a new alternator controller as per T&B or change alternators. Looking at the Balmar alternators/controllers, they look good in having a belt manager which reduces power out so controls the temperature. I the summer, I doubt I need much alternator power. In the winter then maybe alternator temp is not so much of a problem.

When back in the marina, I will go onto shore power, disconnect the lithiums and use the shore power + LA's. Probably little likelyhood of using the IP22 charger to charge the lithiums. When we leave the boat for anytime (24 hours), just disconnect the lithiums.

Cost looks to be about £500 plus the batteries (£1000)

So, the big question for me now is how to wire up the auto disconnect to the various management devices. Both the Aus unit and the BMV 712 have relay outputs (I assume they just close a circuit?). I am thinking of using the BEP 701 mn motorised switch as it seems easy to wire (Tom confirmed that) but how would I wire in one of these latching relays?

www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7FV23130-X0000-A001%7F0612%7Fpdf%7FEnglish%7FENG_DS_V23130-X0000-A001_0612.pdf%7F1-1414939-4 REC

Most of the BMS systems I have seen switch disconnect and reconnect automatically but I only want to disconnect. I will reconnect manually as the disconnect will have been a fault condition that I want to investigate before allowing the Lithiums back in the system. Does that make control of the relay easier? Is it possible to wire 2 separate activation circuits into one disconnect relay, ie connect the Aus unit and the BMV712 to the same TE relay? My simple understanding of circuits say it is but need to check. Any help with how to wire up the Aus unit or BMV712 to a disconnect relay would be great.

Any comments on all the above ?

Well done to T&B, MB and Peterboat for getting me this far.

@peterboat

@MoominPapa

@Tom and Bex

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