Batteries… now how to keep them charged
I have been toying with the idea of making my own charger, or to just buy one. To buy one, it will cost me a minimum of about $800, but probably more. The other day I was given a piece of equipment that had been junked, but saved because it had some possibly usefull parts in it. I believe the unit was an isolator, due to the huge capacitors and transformer in it. It has large gauge AC power wires going in, and 8 120vAC recepticles going out. The capacitors are the largest ones I have ever seen other than car stereo caps. If the unit is an isolator, the transformer is likely a 1:1 ratio, so I should be able to use that off of 110vAC to a rectifier circuit, which will give out roughly 150vDC. Of course there is more to it than that, and depending on how discharged the battery packis, the charge current should be different.
For a battery to be charged correctly, to improve performance and life, it should go through 3 stages during charge. It should pass through a bulk charge state with high current, then a slight overcharge state, and finally a float charge. Using a 144vDC charger also causes problems when it is charging a string of batteries like this. Depending on the battery’s internal resistance, it could be charged faster or slower than the other batteries, further causing certain batteries to degrade faster. I could install a regulator on each battery to keep the voltage regulated during charge, or just run 12 separate isolated battery chargers. It seems like the more research I do, I think 12 separate chargers may be more advantageous, although also more expensive, and maybe less efficient. I may be able to offset the cost by making the chargers myself, but do not know if I have the time or knowhow at this moment. I am looking at different options, and will try to keep the process updated on here. I think a constant 10 to 15 amp charge should be sufficient to get the pack charged back up over night.
144vDC to 12vDC Converter
Some stores are selling the DLS-45 charger from IOTA for the 144vDC to 12vDC conversion. This is actually a 110vAC to 12vDC charger. I am assuming that this just works to attach the leads to the 144vDC battery pack because it must be using a bridge rectifier circuit or something of the like. Needless to say, if it uses a rectifier circuit right off of the “110vAC” leads, I doubt that it keeps the battery pack and the accessory battery isolated from each other. The high voltage of the battery pack should be isolated so the grounds are not attached to one another. If the grounds are attached,and I lean up against the car while I touch the positive lead of the 144vDc pack, I could theoretically get shocked enough to kill me.
I think I will find a way to isolate the pack and accessory batteries, whether it is purchasing a converter or making something myself. I am currently thinking of making a charger by running a transformer off of something like a buck converter, or a PWM circuit to keep it isolated.