Is it okay to mix old and new batteries?

Most batteries would come with the same standard advice in full caps DO NOT MIX NEW AND OLD BATTERIES. Now, we all know that mixing new and old batteries will mean that the old battery will be the first to go, dragging down the performance of the entire group of batteries hence, we mixing is a bad idea. But is it really a bad idea all the time?

But wait. Why would you want to mix old batteries with new ones anyway? Chances are, some batteries are "half used" and it is difficult to say which ones should be thrown away. This is especially so for "drained" batteries that were used in digital cameras. These batteries often have enough remaining capacity to serve low powered devices such as remote controls, sensor lights and calculators for a very long time.

If you have a at least cheapo multimeter, you would be able to find out the voltage of the battery. Although this is not exactly a scientific way to tell the remaining capacity of your battery, it at least give a very rough estimate about when you should actually throw the battery away.

A typical AA/AAA battery should read 1.5V without load. Without load means the battery is not being used at the moment. Normally, the voltage reading of a battery will sag if it is being used. This is more prominent under more demanding loads.

Ok, if you want to mix batteries, read on. But be reminded that this advice is only applicable to non-rechargeable batteries! Mixing full and near-empty rechargeable batteries will certainly damage the near-empty ones as they go beyond empty.

1st step: Check the voltage under no load!
- Put the voltmeter to read "DC voltage"
- Touch the terminals with the probes.
- Is it between 1-1.5V? If it is, re-use it for less demanding devices!

 Information is key...

Step 2:

- Mix those batteries!

Step 3:

When the device is once again low on power, re-check those batteries and see which ones are low. I found that for a 3-battery device, usually only 1 battery is completely dead and needs replacing. Once that dead battery is replaced, it works well again! By doing this, I saved many batteries while keeping my sensor light bright and nice.

Why oh why manufacturers make devices that uses odd number of batteries?

Disclaimer: Alkaline and carbon zinc batteries may leak after a while, regardless of whether they are empty or not. However, driving them till empty increases the chance of leakage, which is corrosive to metal contacts. Do check your battery powered devices once in a while.

I discourage the use of non-rechargeable batteries because they are extremely low on value since they only work once. Rechargeable batteries are slightly more expensive, lasts at least 500 cycles and the electricity used to recharge them is negligible compared to the price of new non-rechargeable batteries. However, they can be rather cheap when bought it bulk for devices that you don't want to keep on an eye on, such as remote controls. These low powered devices have the capability to operate even at very low voltages. This means that you'll have no clue that the battery is almost dead. Rechargeable batteries should never be brought below too low a voltage as it will damage them.

NUS attempts conversion of petrol powered motorcycles to electric.

http://usp.nus.edu.sg/whats-new/2013/usp-launch-demo-electric-bike.html

A bunch of USP students managed to convert an old petrol powered bike into electric propulsion.

The main point of this seems to be aimed at extending the life of really old motorcycles with failing engines. Given the small capacity of most motorcycles, these bikes are usually ridden hard in Singapore in order to keep up with the pace of the roads and expressways. Particularly bikes under the 2B category.

The new electric propulsion makes use of seal-lead acid batteries which are typically very heavy while carrying little capacity, takes a hell of a long time to charge and its lifespan will be shortened every time the battery is used near its full capacity. On the flip side, they are relatively cheap to buy and cheap to maintain.

The only problem this project has is that the costs:

"...costs for the average motorcycle rider using the converted electric engine would drop from about S$121.11 to S$29.79 per month"

The estimate of $121.11/month is overly high if they are only considering petrol costs of a typical 200cc motorbike. Although the chassis used in this project is probably one that came with a 400cc engine, I sincerely doubt that the new electric motor has the same performance as a 400cc engine. Hence, it is fairer to compare it with a petrol engine of similar performance, which will be one that is 200cc and below. Unfortunately, the petrol costs for engines this small typically achieves very high fuel efficiency of about 30-40km/l, which means that it will cost about $70 per month if it is used for 38.5km per day. This means a saving of only $40 per month with the additional inconvenience of range anxiety, inability to follow the pace of other vehicles on the road and the initial conversion price of $3500 is already enough to buy a used bike with about 3-5years COE left.

In terms of overall running costs, an electric bike will save on maintenance fees that a petrol powered bike has to go through every 3 months, however, it is important to note that when the batteries are at its end of life, the replacement will cost quite a bit. In the end, it is difficult to tell which one will cost more in the long run.

While this project demonstrates the feasibility of converting the an old petrol bike into an electric one, the economic feasibility of this endeavor is not good because of the other costs of owning such a motorbike in the first place. This includes insurance, the need to renew the COE of the old bike and road taxes. All these additional fees make it hard for anyone to consider having an electric bike especially when the owner gets charged the same disincentives as one who owns a traditional motorcycle.