SteveO wrote:Burgerman wrote:The chip is fixed with epoxy inside the case, the wires go in series with the computer fan. And a resistor to give approx 12V and connected permanantly to the 24V supply.
So I epoxy the switch directly to the inside of the case near the mossfets and run two wires to the positive wire on the fan, obviously splicing into the pos wire. The connect the fan wire direct to the batteries via a resistor? Or even just to one of the batteries? Sorry to be a pain in the ass but I don't want to get it wrong.
Thanks John
NEVER, EVER, CONNECT ANYTHING TO JUST ONE BATTERY IN A SERIES SET!!!! Always connect across the entire set and design the circuit to produce the desired voltage to the important bits if they don't run on the set voltage*.... Tapping into just one battery in the set will produce an imbalanced load and damage the batteries by causing them to charge unevenly. Search for threads on the need to 'balance' or equalize the charge in the batteries if one wants maximum life out of them. One of the minor advantages of BM's car charging setup is that it automatically balances the batteries any time he hooks up to it.
In theory if one only charged in parallel, the imbalance caused by connecting to just one battery would be corrected each time you charged, but it still isn't a good idea, as you'd be discharging to unequal depths of discharge.
* Getting the desired voltage is an electronics 101 thing, as it is pretty simple, and it is best if you understand the theory, but for chair stuff, the three basic approaches are to:
1. Use two identical 12V devices in series, so they split the 24V from the pack;
2. Use an equivalent value resistor to drop the undesired voltage and dissipate it as heat - make sure the resistor has the wattage rating and be careful where you put it!
3. Use a DC-DC converter.
I will leave it as 'an exercise for the student' to explain how / why each approach works, and the costs / benefits of each....
(doing this will help your understanding, so it's worth the effort....)
ex-Gooserider