Saturday, January 29, 2011

Active Battery Balancing

A while back, I had a problem with the AGM battery bank getting out of balance. This would have damaged it by having one 12V battery under charge all the time, while the other one over charged and gassed (eventually drying up and being killed).

Luckily, I found a fairly cheap (£29) battery balancer that has fixed this.
This one is from Rapid Electronics, made by a British company called Camden Boss.
You connect the balancer to the 24V + terminal and the 0V - terminal and the yellow wire to the 12V middle point. It then works when each battery is over 12.8V (when being charged) and shunts up to 1A of current across either battery, to keep the mid-point at exactly half the full terminal Voltage, ensuring that the batteries charge evenly and fully.

I actually ordered two of these but one hasn't turned up yet, on back order from the maker.

It gets a bit warm when it's working but as the batteries get to be equal in charge, it gradually stops taking power and cools down. So it wastes a bit of solar power by dumping it as heat, but that's better than a fried battery :/

When you've discharging the batteries, they are below 12.8V each and so the balancer does not work and draws no power.

In order for the balancer to work across all the batteries in the AGM bank, I installed the equalisation network that I said I was going to install months ago (but was too lazy to actually do :D ).
It has fuses in the links so that if there is a problem with one string of batteries or the balancing current is too big, the fuse will prevent a melt-down. It doesn't matter so much that the wires are not going to a star point as the current across the links should be zero (or close to it over time). The battery balancing module only moves 1A so that doesn't cause any real Voltage drop either.

The whole thing seems to be behaving itself perfectly and the six batteries now charge much more evenly and fully than before.

Friday, January 28, 2011

No International Battery. Hello GWL!

Well the International Battery guys totally ignored me, so I'll return the favour as a lost customer.

But later I discovered a EU stockist of the Chinese large EV batteries that Thundersky (now renamed Winston Battery) and they were happy to answer questions. They reckon that the Moriningstar controller, suitably programmed, can safely charge their lithium iron yttrium phosphate (LiFeYPO4) cells. They also have a web shop with all the prices and ordering for any user (not just big car manufacturers).

Saturday, January 15, 2011

Fuelly... Track and share your fuel figures

Like the new gadget on my page?

Click on it and you'll be taken to the web site where you can sign up for a free fuel economy tracking database.  You can also compare how well your driving and car fare against other cars and drivers.

Can you beat my high-score?

Friday, January 7, 2011

2010 10:10 Challenge Results

So 2010 came to a close. How did I do on my 10:10 challenge?

.                  2009 kWh  Demand %  2010 kWh  Demand % 
Electricity (grid)  4379      94.2%     3448      83.0%
Electricity (solar)  269       5.8%      705      17.0%
Total Demand        4648                4153

So, from 2009 to 2010, I reduced my total demand for electricity by 10.6%. This was due to better efficiency in use of power (turning things off at the wall to prevent standby power leeching, running a laptop as a server instead of a desktop PC, using the coldest setting on the washing machine, etc.).

Looking at grid power only, I reduced my consumption by over 21%, compared to 2009 levels. This was largely driven by steadily increasing solar power capacity over late 2009 and early 2010, as I bought more panels, bigger charge controllers and bigger batteries to capture and store more power.

But that's only half the story. We use gas to heat the house and provide hot water. In 2010, I started using spare solar power in the Summer to pre-heat the water with the immersion heater; reducing the need for gas in the evenings. But even with the additional wall and roof insulation, the record-breaking severe cold weather we had in early and late 2010 pushed the total demand for gas up by 16.8% (10,295kWh in 2009, to 12,025kWh in 2010). So there's still work to be done.

Our windows aren't very good. The old double glazing isn't very good quality (old types have thin air gaps) and there are three small port-hole windows in the upstairs landing and bathroom that are only single glazed. Our boiler is very old and should be upgraded to a condensing type. We could build a front door porch so that when we open the front door, there's an 'air lock' to prevent cold air blowing into the hall and through the house.

More projects for 2011...