Electronic load testing - NiMH batteries - Energy storage

[Transformedmaggot]

Hey everyone,

I recently found a way to recondition used cylindrical NiMH batteries pretty well (typically those used in the Honda Insight series). However, I want to know whether the batteries will hold practically in the real world outside the laboratory. My aim is to utilize these batteries as back-up storage for a house or maybe even put them back into the car. These batteries have a nominal voltage of 7.2 Volts and a rated capacity of 6.5 Ah (Though the reconditioned pack is obviously lesser than this value). To succeed in this, I'm aware that I need to test these batteries and mimic real world situations.

I purchased the Agilant N3301A/N3304 electronic load tester to help me do just that. The device can do a lot with various settings - CC discharge, CV discharge, constant resistance discharge, pulsed discharge, transient discharge etc etc. I'm completely new to this so my question is:
What tests should I typically run to mimic that of the battery being deployed in a hybrid vehicle? In addition to that, what tests should I perform to know whether these batteries can sustain being used as a back-up storage center for residential purposes? In other words, what are the key things to look out for during these tests.

All inputs on different tests to perform are hugely appreciated! I'm still an amateur at this, but I'm keen to learn and continue developing. Thanks for the time guys!

 

[GregLocock]

I don't think it is that important to get the duty cycle exactly right.

My off grid 200Ah system in winter charges at 20A for 2 hours from the generator, 4 hours at say 3A from the panels, and then gently discharges that over the remaining 18 hours.

In summer it follows the usual sun curve peaking at 25A charge at mid day. By then the pV controller takes over and limits the charge current to float the batteries.

Max current draw would be 60A, that would be unusual, but 30A is not unusual for an hour at a time.

The duty cycle in a car would depend entirely on the details of the cars architecture, control systems, and driving cycle.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Mongrel]

I can't speak much about house batteries. But have noted in automotive applications, there are two types of operators - one will run it to dead empty before recharge, often just enough to get home, then charge overnight. Sometimes a few small charges, just to get to the next stop each time.
The second type is terrified of getting stranded and will not let the batteries drop below around half, roughly.
The point being, make sure you factor charge cycles that the average user might put them through - many don't know the best way to treat a battery! I would suggest it's probably just as important as discharge cycles. More so, maybe, as in automotive service, the discharge cycle can be so hugely variable.