batteriesbattery-chargingcurrent-limitingpowerswitch-mode-power-supply
i have 3 X 12V battery i use them to drive a dirt bike .i want to charge them with a 36v-30A power supply the maximum charge current is 6 amps that is given by the manufacturer . will this damage my battery packs ? more over how many amps would the battery draw? i am not using current limiting circuits
Building a 28.8 Volt @ 30A power supply (> 860 Watts) is not a trivial exercise even for an experienced power supply design engineer. Getting it to be accurate to 0.1V (+/- 0.35 %) probably doubles the challenge!!
This would not something that you could successfully "hack together".
I would encourage you to look around at some electronics equipment surplus yards to see if you can find a ready built 28V supply (28V DC was common in military, aerospace and some communications applications). Look for a high power linear power supply. These are usually adjustable (or can be modified to be adjustable). Linear power supplies can be adjusted up and down by a volt or so to get to your unusual voltage requirement.
One name to look for is Lambda. If you find the type of thing I have in mind it would likely look like this:
Battery with nominal voltage 12V usually is charged with a little higher voltage. If this is lead-acid battery - that voltage should be 13.8 - 14.4V.
Computer power supply is definetly not designed to be connected to battery. Partially discharged 12V battery can have voltage higher than 12V. If you connect it to computer power supply - you may feed power supply with energy. Power supply will "see" too high voltage on its output and will try to lower it to 12V. Depending on design of that power supply - bad things can happen.
You would need some circuit to limit current or some battery charging circuit anyway. Depending on battery type and size - you will probably damage battery or power supply. Battery can even explode, so never try charging when you can't measure current.
Many (if not all) computer power supply units can't work without some minimum load. You shall not power on computer power supply without load.
If you have no multimeter and no experience with electronics at all - I would recommend you to buy battery charger for that specyfic battery type (chemistry) and size.
Best Answer
To properly charge three 12 volt lead-acid batteries connected in series, you will need about 43 volts, but should limit the current to under 4 amps or so.
A 36 volt charging source will leave the batteries well below full charge.