Multi Battery Charger (Richard)

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Conversation with Richard Smith at OLPC about a multi battery charger

Subject: Multi battery charger

From: Beth Santos <>
Date: Thu, Sep 16, 2010 at 10:29 AM
To: Richard Smith <>

Hi Richard!

Long time no see! How are things going for you?

Tim and I are looking at alternative energy solutions in case we wanted to do a pilot in rural Haiti. We thought maybe you could get a solar panel to charge one of the multi battery chargers that OLPC designed. I figured I'd go to you for help as we're trying to figure out how much it'd cost to make one of these chargers, what kind of solar panel it'd need to power it, etc. Got a second?

Feel free to email, Skype ("notonfriday" is my handle), or call 603.661.1273 (my cell)

Thanks much!


Beth SantosOutreach Coordinator
Waveplace Foundation

Tel: +1 610 797 3100 x 44
Fax: +1 610 797 3199
Cell: +1 603 661 1273

Waveplace on Facebook

Twitter: @waveplace

From: Richard Smith <>
Date: Fri, Sep 17, 2010 at 9:57 AM
To: Beth Santos <>

The MBC has a DC-DC converter option that you can feed the input from
a solar panel into.  If you are going to charge all 15 batteries at
once you need around 300W of solar input.

The problem for you however would be MOQ.  As we don't have the MBC in
production you can only get them in quantities of 200 or more.

How many XO's are we talking about here?  Are individual 10W panels an option?
Richard A. Smith

From: Beth Santos <>
Date: Fri, Sep 17, 2010 at 10:10 AM
To: Richard Smith <>

Hmmm...yes, individual panels are an option if you can hook them up to each other, which I'm assuming you can? Our pilots use 25 laptops (20 for kids, 5 for mentors/teachers) so we'd need some way to pretty much charge 25 laptops/batteries at once. Since the pilot would potentially be in an area where electricity is scarce, we're looking into generators, a solar panel/battery system that powers a bunch of XOs through a couple of power strips plugged into the battery, or a solar panel/XO battery charger hookup. Considering the price of gas and upkeep for a generator, I'm thinking solar is the way to go, but not quite sure how to work it.


From: Richard Smith <>
Date: Fri, Sep 17, 2010 at 10:57 AM
To: Beth Santos <>

No I was referring to the 10W panels that plug directly into the XO.
Does not sound like that would work for you.
The first thing you have to decide when using solar is how long can
you go without power.  That dictates what sort of system you have to
install to meet the requirements.

I usually specify no more than 1 consecutive day.  ie you can be out
for 1 day but the system should recover on the next day. (under normal

Next you need your usage model.  How many hours are day are the XO's used?

At the wall plug each XO needs 48Wh to recharge and roughly 10Wh to run.

Lets pick 4 hours of use and 1 recharge per day thats 48 + ( 10 * 4)
or 88Wh /day/XO.
Total of 2200 Wh/day.  You need a system that can provide that much
output power per day.   If you want back up juice then your batteries
need to be sized to provide that much power/day.  If you wan to be
able to recover in 1 day then you need at least 2x that in input power
so you can both meet your daily needs and recharge the system.

So can you live with longer periods of no power or does this have to
be a daily thing?
Richard A. Smith

From: Beth Santos <>
Date: Fri, Sep 17, 2010 at 2:03 PM
To: Timothy Falconer <>


From: Beth Santos <>
Date: Tue, Sep 21, 2010 at 9:42 AM
To: Richard Smith <>

Hm, this is a good question. Normally we use the laptops for about three hours (max) per day, five days per week (M-F). So the only "recharge days" they'd have would potentially be on the weekend, but even then the kids are going to want to use the laptops while at home so it could be a sticky situation. However, definitely could be workable.

I'll check with Tim and see what he thinks.

Thanks Richard!


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