[RE-wrenches] Load testing Lithium battery bank

Ray Walters ray at solarray.com
Tue Mar 17 13:07:00 PDT 2015


Those look like your solution.  Also water can take more heat with less 
trouble than air heaters.  I've had air heaters start melting things, 
etc.  You can just install those in the side of a 55 gal barrel with a 
bulkhead fitting, or yes, weld the appropriate plumbing fitting to the 
side of the barrel. Might even be able to install them into a section of 
pipe with  Ts and run water through it to cool the elements.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 3/17/2015 1:40 PM, Larry wrote:
> Hey Ray,
>
> I remember seeing huge banks of light bulbs as loads back in the early 
> 70's.
>
> I need to test the entire bank as one unit as the first cell of 32 to 
> reach 2.8 volts determines the capacity for the bank. I just saw Home 
> Depot has a 2kW 120 volt water heater for $10. Guess I need to do some 
> welding.
>
> Thank you,
>
> Larry Crutcher
> Starlight Solar Power Systems
>
> On 3/17/15 11:59 AM, Ray Walters wrote:
>> Hi Larry,
>>
>> I think you hit on the best load already: water heater elements rated 
>> for 120 v.  We have also used dump loads for wind turbines like the 
>> air heating elements from Bergey, but they are only about 1 kW each.  
>> Another possible source are the resistor banks for old golf carts 
>> (before they had controllers, they used resistor banks to operate at 
>> slow speeds)
>> A very long time ago, an inverter company had a demonstration that 
>> used a large bank of incandescent light bulbs.  They used to make a 
>> 300 watt bulb for mining, so 33 of those would work. (maybe a few 
>> more bulbs, since your voltage is bit lower than 120 v)  Cheap 
>> electric space heaters would work too.  You also might look around at 
>> an electronics surplus store.
>> Whatever you do, it sounds like a lot of time and work to set up. Any 
>> chance of doing a smaller load test for subsets of the total bank?  
>> You might be able to use a standard 12 v battery load tester then.
>>
>> Good Luck.
>>
>> R.Ray Walters
>> CTO, Solarray, Inc
>> Nabcep Certified PV Installer,
>> Licensed Master Electrician
>> Solar Design Engineer
>> 303 505-8760
>>
>> On 3/17/2015 12:41 PM, Larry wrote:
>>> I am repairing and restoring a pair of poorly designed lithium-ion 
>>> battery bank that suffered over discharge, damaging many cells. 
>>> After cell replacement I need to perform a discharge test with a 
>>> 10kW load to verify the remaining capacity. The battery voltage is 
>>> 105 volts @ 100% SoC and 89.6 volts @ 0%
>>>
>>> I would like advice on how I can create an economical 10kW load. 
>>> Water heating element? Wire wound resistors? Are there any GT 
>>> inverters that will operate at these voltages?
>>>
>>> Thanks.
>>>
>>
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