# Charging/preparing and testing individual Tesla modules



## oudevolvo (Mar 10, 2015)

An update with some answers I found myself.
You can charge li-ion with a lab power supply quite good by limiting volts and amps.
Need to check on pre-charge and ending the charge process manually. 
https://www.youtube.com/watch?v=jNmlxBXEqW0

I need 44,4 V nominal so searched for a 60V lab power supply and found this one http://www.conrad.com/ce/en/product...wer-Supply-Switched-Mode-Remote-Control-Bench
However that is only for charging a whole module. Should be sufficient while testing on the bench.
Once in the car, the BMS will monitor and balance on cell level.

However, it might be worth buying a balancer/charger to connect to the lab power supply.
There are not many that support 12s, but found this one http://www.hobbypartz.com/75p-1220-charger.html


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## Karter2 (Nov 17, 2011)

Im assuming you are using "modified" 37p modules ?
Even so, you are going to need a lot of current either charging or discharging to see any significant temperature effect?
At 1C (3amps per cell) charge, you will need over 110amps from a 44v supply ...thats over 5 kW !....
...and if you really want to see any serious discharge load,..say 3C, that would be over 350amps or 15 kW to dump somehow ??


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## oudevolvo (Mar 10, 2015)

Thanks for the reality check!
It indeed is 37p
So you are right, the max 10A from the lab power supply is only 0,27A per cell. I agree that it probably won't reveal any temperature issues.
So the only added value would be is to check the healthyness of the module (see if all cells go up and down in the same manner) with the Thunder balancer/charger.
But also in this case, since the cells are not stretched at all possible issues will remain hidden.

Perhaps the best approach is to somehow use the car equipment for testing. Either by setting it up "stand alone" or while mounted in the car and hooking up the modules while not stacked yet or swapping them to be able to see the modules one by one on top and check them with the flir.


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## Karter2 (Nov 17, 2011)

High current discharges are relatively easy and practical to rig up without complex equipment.
Commercial heater elements, stainless wire in a water bath, even lengths of rebar have been employed.
EVTV has a video somewhere of a guy doing a 2000 amp discharge test on a large cell using only a rew pieces of copper , a wrench, and a bucket of Water !
....instrumentation is the biggest cost.


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## oudevolvo (Mar 10, 2015)

Thanks for that addition.
In that case I will change my test approach and while charging only check whether the voltages in the 1s strings go up and doen together nicely. Is it no problem that this can take quite a while with the equipent I found.

The temperature test will then only be done on discharge.
I have a flir already so next step is to find a safe/good and affordable way to dump the power.
Will continue my search, suggestions on how to set this up in more detail are welcome.


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## GoElectric (Nov 15, 2015)

I was going to say some of the same things. Having a 12s charger is a big step in the right direction, using your charger on the bench is a good idea too; I'll likely be trying that.

Let's keep talking about how to get high discharge rates - interesting to hear how simple/crude it can be.


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## Karter2 (Nov 17, 2011)

This is a good starting point..
19kW discharge tester...
https://endless-sphere.com/forums/viewtopic.php?f=14&t=74567&hilit=Hair+dryer


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## oudevolvo (Mar 10, 2015)

First an update on my charging ideas.
The Thunder 1220 I found http://www.hobbypartz.com/75p-1220-charger.html has a 20.000 Ah limit so that one won’t work.
After some further research I found another one http://www.elprog.com.pl/english/?strona=1_firma&pstrona=02/00
That device can handle 12S and capacity up until 200 Ah.
However, together with a suitable power supply it costs about EUR 1100 so a test setup becomes quite expensive.

I think I am going to stick to a lab power supply to be able to at least put in some energy in the modules and manually monitor the 1S strings with a multimeter.

Regarding discharge: Thanks Karter2, interesting approach.
In my case not very practical I guess since our outlet voltage is 240V and a hairdryer is approx. 2000W. When operating at 44,4V there will not be much dump capacity left (am I drawing the right conclusion?).
Furthermore I would need AC 240V to spin the fans.

However, I did do some further research and hope you can think along.
I wound this element
http://uk.rs-online.com/web/p/panel-mount-fixed-resistors/7015888/
It's 1Ω ±5% and 2500W

At my max voltage of 49,44V the current will be 49 Amps and thus the power is 2,4kW
If I put two of these in parallel I can have a current of 100A or perhaps with 3 or 4 even more.
Is that thinking correct?


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## GoElectric (Nov 15, 2015)

Hi. Yes, finding something which will have enough capacity to measure the capacity of a module 5.5KWh might be a challenge, I never thought of that. I plan to use my BMS etc....

As far as discharge goes, I think the idea of ordering some resistance wire and immersing it in water is the way to go. 

We are really struggling with how to get the wires for the BMS out of the box, but are likely going to build a small board with the same footprint as the original, put some fuses on it, and another connector which comes out of the box. Will post progress on that, as well as the battery heating-system.

jim


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## Karter2 (Nov 17, 2011)

These 48v , 2kW, water heaters are cheaper at $30 each.
http://www.ebay.com.au/itm/48-volt-...ter-Heater-element-4-solar-wind-/391328196721


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## electro wrks (Mar 5, 2012)

Here's a discussion on load testing from the ElMoto forum: http://elmoto.net/showthread.php?t=2481&page=3&highlight=load+test 

I like the load test in post 21 the best!


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