EV batteries tester

[Mantas]

Hello,
I know, that this is not EV forum, but you know a lot about chargers
I am looking for charger, which could test electric car battery capacity. I am very interested in iCharger 4010Duo. It seems strong enough even for bigger capacity batteries.
I have some lithium and some NiCd batteries to test. The problem is with NiCd - there is 5 cells (1.2V) connected in series. They are sealed and flooded with electrolyte and I cannot connect each cell to balancing port. Can I connect all battery (with 5 cells) to one channel of balancing port? I need only to test capacity of these batteries. How many of these batteries I could test on one channel?

[RedOctobyr]

Lithium batteries are the only ones that will use balance connectors.

Your NiCd packs will just use the main red & black leads, and that's it, going to the main charge ports on the charger. No balance connections will be used.

I don't have the 4010Duo manual handy, but my 308Duo can handle up to 20-cells-in-series NiCd setups on each channel. I'd assume the 4010Duo can do more, as it can handle higher battery voltages (10S LiPos, vs my 8S), but check its manual.

So you could connect up to (4) of your 5-cell NiCd packs in series on a single channel, if you wanted.

Bear in mind, though, that if just one of the NiCd cells in series drops off earlier than the rest, it won't be as obvious, when testing more cells in series. You'd be setting a discharge target voltage that's much lower than your starting voltage. One cell could completely disappear, and that still might not drop things low enough to hit your target, and stop the charge. Put differently, the test is more sensitive/safer if you are testing fewer cells in series, as there is no balance lead.

What sort of capacity test do you have in mind? Slow and gradual? Or are you trying to put a "big" load on the packs you're testing? The 4010Duo will let you apply up to a 1000W load, discharging into a suitable external resistive load on the other channel. You'd likely have to assemble this load yourself. The other Duos can do this as well, but with a lower wattage load (650W for the 308Duo, 700W for the 406Duo).

[Mantas]

Hi,
Thank you for reply.
What could happen if I connect all battery with 5 cells to one cell balancing port channel? What is maximum one channel input voltage? In that case I could adjust min voltage for each battery at 4,5V (empty battery voltage) and test more (4-5) batteries in series. Then I would avoid problem, when one of the cells is discharged earlier.
Anyway, it is not problem to test batteries one by one, I have enough time for that. The main thing that I need to get from the test is battery capacity.
Nominal NiCd battery capacity is 100 Ah. Of course they will have 70-90% of their capacity now. For my test I will charge battery with 20A (that is normal charging current in my EV), and discharge with 100A. So maybe I can charge some batteries in series, but discharge them one by one. Overcharging is not problem for these flooded NiCd batteries, EV is always overcharging them in order to balance.

[RedOctobyr]

I don't know the maximum voltage for the balance port. The Duos can charge a LiPo as high as 4.35V/cell, so they can at least handle 4.35V.

But if discharged is already 4.5V, I would not assume there balance port can handle the voltage you're talking about.

You could email ProgressiveRC, perhaps they know. Or email Junsi, or ask in the Duos thread on RCGroups.

Any of the Duos can do a 20A charge. But none can discharge (or charge) faster than 40A. If you want a 100A discharge, you will have to provide your own external load, connected directly to the battery. But you will give up the ability to measure capacity, as the current will no longer be flowing through the charger.

If you can manage with a 40A discharge, the 406Duo or 4010Duo will give you that, if you build/provide a suitable external resistive load. There is info available to help with doing that.

If you need 100A, then I'm not sure of a good commercial solution. There are power meters you can hook to your RC aircraft, to check peak current draw, etc. 100A is not unreasonable there. But I don't know if any of those systems can provide the total capacity used.

You would need something that can measure the current flow at regular time intervals, and log that data, so that you could later calculate capacity by importing the data to Excel, or similar.

Sent using Tapatalk.

[RedOctobyr]

I was thinking about this some more, in terms of options to let you discharge at 100A. If you can apply your own 100A load directly to the battery being tested, you could try to make your own capacity-measuring setup.

A data-logging multimeter, and a suitable current shunt, might let you indirectly measure current, and record that data. Then later, you could calculate the total amp-hours passed during the test.

If you added a second multimeter, logging the voltage from the battery, you could also calculate watt-hours, in addition to amp-hours. As an example, if one battery provided 100A for 30 minutes, but held at 5.5V, and another provided 100A for 30 minutes, but did it at 5.2V, measuring voltage in addition to amps would let you understand that the first battery effectively had more capacity, as the watt-hours for it would be higher than the second.

A quick Google search turned up this as an inexpensive (~$50) multimeter that can output data over a serial connection, to a PC. UNI-T model UT61E:

http://www.amazon.com/UNI-T-Digital-.../dp/B007THZMWI

This is the discussion where I saw it mentioned:
http://www.eevblog.com/forum/testgea...ter-yes-or-no/

This is an example of a 100A current shunt:
http://www.ebay.com/itm/100A-75mV-Sh...item51c76ed824

With 100A flowing through it, you'd measure a 75mV voltage drop across the shunt. So you could use a multimeter to measure the voltage drop across it. Then, from the measured voltage, you can calculate the current that's flowing.

Log that data, with a known time interval between samples, and you can calculate the Amp-hours passed during your test.

But if you simply connected a big external load, you'd need to manually stop the discharge once it reached a voltage of your choosing. If you used the charger, it would let you hold at that voltage, until the current tapered down to a certain % of your initial current. If doing it manually, you'd lose that ability, you'd have to just stop the process completely once you hit a certain voltage.

If you have a very large battery that you can dump the discharged energy into, you could use the Regenerative Discharge feature of the Duos. This *might* let you draw 40A on each channel of a 406 or 4010, for a total of 80A. Possibly even from a single battery, if you can combine the two channels in Sync mode. Then the charger will dump that energy into a large, discharged battery that would be powering the charger.

I've never needed to use Regenerative mode, personally, but it might let you get closer to your goal of 100A discharge. But you would need a source battery, powering the charger, that could safely accept a 500-600W charge, assuming a single 5-6V NiCd module, connected to both output channels using the proper cables.