Project Everest

Work Update

Timor-Leste: Analysis of battery options

Timor-Leste has an excellent incoming solar resource throughout the year (on an average 4.8 kWh/m2/day) (https://eosweb.larc.nasa.go) and to take full advantage of this resource, the February Energy team has been looking for interested businesses and households for Solar Energy.

 

The team has researched battery suppliers for solar and also researched the following battery technologies:

 

1. Lead Acid Batteries

 

  • Conventional - Flooded Type
  • Valve Regulated Lead Acid (VRLA) - Gel/Mat Type

2. Lithium Ion Batteries

A brief summary of these technologies is given in the table attached below.

 

From our research, we realised that purchasing batteries from solar suppliers is a costly option. Adding a battery to the solar energy system almost triples the initial capital investment required. Hence the team changed our sales approach and began focussing on businesses which run only during the day and don’t require large amounts of electricity storage. This limited the scope of our project and reduced the number of prospective clients.

 

Accompanied by this roadblock, we headed into a weekend getaway to Atauro Island. The island is a completely off-grid location. During our weekend getaway at Barry’s Place (Atauro Island) we were struck by an interesting idea. We were impressed by how Barry was utilising car batteries and small solar panel arrays to power a few lights and a fan in each of the rooms.

 

Car batteries are flooded type lead acid batteries which have less capacity compared to other available battery technologies. We had an idea to use two-wheeler batteries that are gel type. The VRLA gel type batteries cover most of the disadvantages of conventional lead acid batteries and could be a great option. With these batteries, we can make small solar energy systems that can be used to power lights fans and charge mobile phones.

 

Reusing car/two-wheeler batteries for such small solar applications also encourages recycling along with offering a cheaper alternative to buying new batteries.

 

We heard that the Malawi energy team also looked into reusing old batteries and it would be great to receive input and feedback from them. We would like to know:

 

How they are progressing with this?

How did it work for them?

What kind of problems they encountered while developing the prototype?

What was the lifetime (in years) for these recycled batteries?

 

And finally, can it be implemented for businesses?

 

edited on 2nd July 2018, 06:07 by Wade Tink

Scott Jucius Feb 15, 2018

The Malawi energy team is currently following on from previous team’s work with the use of lead-acid batteries. These batteries aren’t recycled but are actually new. In Malawi our current target market are those in villages where we aim to sell a solar panel and battery product that will enable them to charge phones and power lighting. Lead-acid batteries are currently being utilised due to its lower cost and its availability in country. One of the biggest issues surrounding this type of battery is the deep-discharge which is currently being worked on. This is currently a work in progress as this month the team has had more of a focus on the business aspect and supply chain. The January team believed to have solved deep discharge before blowing a circuit due to either component issues or incorrect installation. Therefore, we are currently ensuring that we don’t drain our battery when powering electronics. We also potentially have a few other issues including reverse charge, short circuiting and overcharge of devices, these are all currently being solved.

Due to the price we are looking into the importation of batteries from other countries to lower the COGS. But we have found that importing batteries via air into Malawi is illegal due to safety concerns, therefore must be shipped. As Malawi is landlocked, any batteries imported will take a considerable after ordering.

If you want further clarification or have any other questions I will be more than happy to answer them.

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Ishpreet Singh Chawla Feb 16, 2018

What kind of Lead acid batteries did you consider. Conventional type or the VRLA type?
What is the Amp-hour capacity of the batteries which you looked at?
Did you try using blocking diodes etc. in your charging and discharging circuits to prevent the reverse charging issue?
Thanks!

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Ira Dudley-Bestow Feb 16, 2018

Ok, so we are using a 7.2 Ah VRLA Lead Acid battery, and we have a diode in the circuit to prevent reverse charge. Although the circuitry also prevents overcharge and deep discharge, although this circuitry is currently expensive and we're looking to simplify the circuit further.

Attached is the circuit that we are currently relying on, this was sourced from one of our stakeholders at Polytech University of Malawi. Although when we tried to put it together we attached one of the diodes round the wrong way and fried the N-Mosfet.

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Ira Dudley-Bestow Feb 16, 2018

One of our interns recently found this IC chip which might do a fair bit of the work for us though, but I have no idea if it works, how to test it or even if we can get it in Malawi. Would been keen to here your thoughts on it.

http://cds.linear.com/docs/en/datasheet/1573fa.pdf

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Ishpreet Singh Chawla Feb 19, 2018

I've personally lost touch with electronics..would be helpful to get some feedback from someone who knows their circuits. You can also contact companies who make small-scale battery charging circuits and see if they can provide some help.

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Wade Tink Jul 2, 2018

Status label added: Work Update

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