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TOPIC: Li Ion Battery Modules

Li Ion Battery Modules 14 Jun 2018 13:19 #99368

Hi, Colin

I’m sure Daniel will come back to you in more detail, but the Tesla’s he installed in Emma are in 7s. I’ve played with the system for the last couple of months and this weekend we are going to reconfigure the BMS and other devices onboard so we will only be using about 16KWhrs of the 22 installed, so about 75 per cent.

With the solar panels installed I have not been using the available capacity so I’ve asked Daniel to reconfigure to charge to a lower level and stop drawing power at a higher level. As you say, it makes a huge difference to longevity. Furthermore, our charge rate is much lower than 1C and the discharge rate muuuchhh lower, so this helps, too.

From my research long term storage is optimal around the capacity mid-point and Daniel’s been looking at a “switch” which will change the BMS settings to a ‘storage mode’. Which will have an even lower/higher settings.

These batteries and upgraded system have really transformed our life onboard.

Happy to help further if I can. Daniel’s the tech, though of course .


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Li Ion Battery Modules 14 Jun 2018 13:17 #99367

Hi Colin,

I use other modules from Mercedes Benz, made by Tesla (from before Mercedes made their own EV systems), these are 7s, so perfect for 24v.

Battery life is indeed longest when not using the top part of the SOC, so we try to not charge 'fuller' than necessary, and also add a 'storage mode' to keep batteries on 50% charge when not being used (and most boats have more 'unused' time than used time.

So with a little care, you can expect a 3500 cycles lifetime, meaning 10 years every day cycling...and 'lifetime' is described as 80% remaining charge capacity, so still very usable.
Also it's no problem to add more capacity later (preferably the same chemistry of lithium, but not necessarily), something unheard of with lead-acid batteries.

I have tested battery modules 3,5 years old (from both fully electric cars as hybrids), still keeping 100% of original capacity, so I'm quite optimistic on 'real world' life expectancy.

The BMW i3 battery: I have access to only 6 'older' modules (60Ah, 12s), these are very usable for a 48v system, difficult to convert to 6s (but not impossible) see attachment.
The following user(s) said Thank You: Paul Strawbridge

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Li Ion Battery Modules 14 Jun 2018 12:25 #99366

  • Colin Stone
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Very interesting. Do you rebuild the Tesla modules to 7s to get a slightly higher voltage?

Reading the EV forums, I found this table based on tests of Samsung 18650 cells - 3.7v 2600mah.
( pushevs.com/2018/04/27/battery-charging-full-versus-partial/ )

Cycling from 100 to 0 % we get 500 cycles
Cycling from 100 to 10 % we get 500 cycles
Cycling from 100 to 20 % we get 1.000 cycles

Cycling from 90 to 0 % we get 1.500 cycles
Cycling from 90 to 10 % we get 1.500 cycles
Cycling from 90 to 20 % we get 2.000 cycles

Cycling from 80 to 0 % we get 3.000 cycles
Cycling from 80 to 10 % we get 3.000 cycles
Cycling from 80 to 20 % we get 3.500 cycles

Cycling from 70 to 0 % we get 5.000 cycles
Cycling from 70 to 10 % we get 5.500 cycles
Cycling from 70 to 20 % we get 6.000 cycles

As you can see it’s better to cycle battery cells at lower SOC. For example, if you decide to constantly fully charge a battery cell (100 %) and discharge it till 20 % you can expect 1.000 cycles until reaching the EOL. However, if you charge it till 80 % and discharge it fully (till 0 %), you can expect to triple the cycles (3.000) before reaching the EOL. In both cases you’re only using 80 % of the total battery cell capacity.

Battery experts on phone batteries say they should be kept between 80% and 20% SOC for long life.

BMW i3 has interesting Samsung cells. SDI94 - 3.68v and 94Ah, but increasing to 120Ah. Car has 96 2kg cells only in series which is described as being KISS!!
So around 45kwh and 192kg without BMS etc.
94Ah cell in Czech Republic £178.
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Colin Stone

Li Ion Battery Modules 09 Jun 2018 16:11 #99293

A couple of points I should have added:
Next week we are going to tweak the battery BMS settings. The reason being we are not fully utilising the battery power. We configured them so around 19 of the >22KWhrs was useable. I now plan to reduce the max charge voltageand raise the minimum slightly so we will have about 17KWhrs useable. Unlike lead/gels the Lithiums prefer not to be fully chargedor held there. They don’t like being completely discharged either, but go far lower than you’d take a lead/agm. They are far happier in the mid-range. With these setting I fully expect the batteries to last longer than I will.
One other key point is the speed of charge of these little suckers. We limited the genny to about 80% power (4KW) and the new Victron charger uses pretty-much all of that at 120A (48VDC) and the batteries swallow it up. Or if motoring with a decent alternator (typical output of ours is 1.5-3KW at sensible speeds, a depleted battery system is charged in no time. With our settings (below the actual max voltage of the batteries for longevity) the charge rate is pretty-much maintained right up to the target voltage.
We’ve a swish Victron manager (that I can also access remotely) and can capture screen shots if anyone’s interested.

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Li Ion Battery Modules 09 Jun 2018 15:53 #99292

This winter (17/18) Daniel fitted >22KWhrs of Lithium batteries (these happened to be ex-Tesla but the VW versions are more widely available of course), fitted 6x300W solar panels, upgraded my charger/inverter to 8KW and converted the 3-phase genny (don’t ask!) to single phase, unrated the measly original alternator and fitted a “smart charger’, plus some other smaller jobs. Been on the barge in The Netherlands for 14 weeks so far. We do very few miles, often in the same place for 3 days and if we do move it’s rarely for more then a couple of (slow) hours motoring. Not “plugged in” even once. Only run the genny twice for a couple of hours (and once we tweak the threshold settings of the battery minimum voltages for larger current draw devices like the hob next week, we would not have had to have done that). We no longer consider “can I switch “x’ on as “y “is running, and can I flush the loo which will run the pump”. We can have the oven and the hob on and run the pumps. We put the washining machine on when needed (but usually when sunny for solar power and drying). It’s almost like being at home; a complete revelation to what was on her when we bought her - we had to keep running the genny to cook and charge the gel batteries (but never much over 85% as it takes so long). It has changed our life aboard to a *huuuuge* degree. I keep asking SWMBO if she can cook or iron or wash or something as we’ve solar volts going to waste!
I, and The Boss, are so pleased we did this and Daniël was a pleasure to work with.
Any questions, please let me know.

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Li Ion Battery Modules 03 Jun 2018 22:39 #99163

I had 'too many links' in the message, so had to cut-out a bit:

I will try to make a better post sometimes, there is lots more to show...520V / 67kWh battery in 26(ish) meter Stijlsteven, electric propulsion. a 20m Stijlsteven with 26 solar panels (300Wp each) and 30kW electric propulsion + 48v / 20kWh battery + 3x Victton 8k units, etc.

50kWh / 24kVA system for 'on-land' use:

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Li Ion Battery Modules 03 Jun 2018 22:38 #99162

These are usable, they are quite expensive though.
The Model S/X modules are 6s (6 groups of cells in series), for 24v use; 7s batteries are more suitable.

here are some batteries being dismantled:

To use 6s modules, maximum charge voltage is about 25.2v, and for long life of lithium batteries: 24,6 volt.

I've been planning to write a topic on lithium batteries, but haven't yet...kind of busy.

The Model S modules (from a 85kWh battery pack) are about 5 kWh per module, usable energy a little less even. in Amps: 200 Ah

I've started a small business last year, firstly to convert barges and small boats to electric propulsion, and when I found a company that is legally allowed to recycle lithium car batteries for re-use (second life), I also ventured into energy storage solutions for homes and businesses .

I've made some 24 batteries, this is a 7 kWh one (300Ah):

these are 7s modules, 2,8 kWh each, I make those with 4 modules in an enclosure for a 10kWh battery:

Prices: about €350,- per kWh, small batteries a bit more, because of production costs, bms, etc. (ex VAT)

When you use lithium batteries you -MUST- use a BMS system, (Battery Management System). This bms tells the inverter(s) / charger(s) etc. to stop when there is something wrong with the battery, and keeps the battery 'balanced' (all cells at the same voltage when charged) to prevent one cell / group of cells to go to a higher voltage than the rest, potentially damaging the cell or even catching fire.
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Li Ion Battery Modules 03 Jun 2018 22:11 #99161

Daniel Boekel ( a DBA member ) with Oving 1 has been producing these with a BVM system. He installed them on several barges already

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Li Ion Battery Modules 03 Jun 2018 17:01 #99159

  • Colin Stone
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Just been noodling on www and read that Tesla Model S, and X, battery modules may be ideal for boats. Each module of 444 18650 Panasonic laptop cells is rated at 24v and 232Ah.
Two such modules would provide the same useable energy as a 24v 600-700Ah lead acid battery.

Becoming available from car breakers. In USA a module is around $1500.

They only weighs 55lbs, so perhaps not good if ballast is also required!!

RV owner has put a module in his RV to use with his solar panels and generator etc.

A thought??

Colin Stone

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Colin Stone
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