sources of power
the CerfBoard requires a regulated 5v supply, aprox 900mA
we used clones of the Sony NP-F730/750 OR NP-F930/960 infoLithium Battery which could run something like 6hrs. a not so chunky option which lasted around 2hrs is the Sony NP-F550 - 3000mAh, 7.2V. (more details in Cerf Notes)
NiMH smart charger is to make it from a Maxim 712 chip. Maxim makes two very similar charger chips. The MAX 713 is for NiCad batteries, and the MAX 712 is for NiMH. The 713 turns off when the voltage drops after NiCad battery is fully charged. The 712 turns off when the voltage levels out rather than dropping. They felt that this was a safer approach than trying to detect the small drop that occurs. I think it makes sense, especially as it terminates charging a bit quicker, resulting in less overcharging. The MAX 712 also monitors temperature, and charging can be terminated by maximum temperature. But this requires you to make up battery packs with thermistors in them.
trickle charger However, since NiMH batteries are so very sensitive to overcharging, the best approach is to use a very low current in order to minimize overcharge damage. One frequent poster to the bikecurrent mailing list uses a charger that charges at a rate something like C/60 and has had good results with it. C/60 is the capacity of the battery in amp-hours divided by 60. So if you had a battery with capacity 4 amp-hours (4000 mAh), C/60 is 67 mA. At this current rate, the battery would be charged from empty in about 84 hours, i.e. about 3 and a half days.
There are techniques to restore batteries, in particular lead-acid batteries, that are beginning to lose power. The main problem seems to be that they develop a layer of crystals that blocks power. The capacitive chargers that use a capacitor to limit the amps that can flow to a battery seem to pulse the layer off the batteries.
The other main technique seems to be based around using chemicals to free the plates from the crystal layer. Epsom salts for instance. Some resources: http://www.warriorforum.com/off-topic-forum/525296-battery-trick-really-works.html
December 2015. We (TU) have ordered a Da PIMP (Power In My Pocket) charger / pulser / desulphater from Holy Scrap. We took the kit, so we need to follow the instructions to assemble it. Some Instructions too. We will test it on several car batteries, notes to follow. We do not know what this sulphination really looks like. But I suppose we will learn.
This product from the UK also looks good. And has a bit of a whinge about these “older” products. Let's see what the PIMP does. Perhaps the UK product is actually more appropriate! But it is only a desulphinator, albeit one that is always operational. It keeps batteries healthy for longer. The PIMP will recharge and desulphinate. So for now, we try the PIMP. If we end up with more complex systems, we can worry about the others.
Libarynth > Main Web > BatteryTechnology r5 - 07 Jul 2004 - 13:17