battery charger hack

[michaelmrc]

question on battery charging, if your charger does not have an equalize function could you not install a diode inline with the pos output of the charger tricking it into a higher voltage thus creating some equalization.

[donradcliffe]

No-- you can get lower voltages with the diode, not higher.

[michaelmrc]

yes but wouldnt the charger sense a lower voltage from the batteries and increase the voltage to compensate. i know car audio installers have been modifying car alternators for years by adding a diode into the regulators voltage sense line just wondering if anyone has tried this with a battery charger

[a64pilot]

You sure you don't mean resistor instead of diode?

[michaelmrc]

nope i mean diode. thus creating an approx .6 voltage drop that the regulator has to compensate for. just like in this article.
SmartGauge Electronics - Increasing alternator charge voltages

[michaelmrc]

decided to try a little experiment. taking my old school non intelligent cheapo battery charger and connecting it to my test bench battery. this charger never charges past 14.2 volts no matter how long it charges. i added a 1n5404 diode inline with the pos cable and immediately the voltage started to climb. peaking after a few minutes at 14.8 volts. a.6 volt increase which makes sense. next i decided to try adding another diode and again the voltage increased although not to the same extent. after a few minutes voltage reading was 15.15V and measuring current with my ampclamp meter current has settled between 900 milliamps and 1 amp.
so my thinking is that in theory and practice i can raise the voltage with this simple trick in order to equalize a battery with a non equalizing charger.
next test i guess is to try doing this same setup with an intelligent charger.

[F51]

I love it when somebody does a bit of creative tinkering like this. For an intelligent charger I suspect that the diodes need to be in the voltage sense lines. Wish I had a test bench on board to try this!

[michaelmrc]

thanks but realistically the intelligent charger still senses voltage from the battery in the same way so cant think of a reason why the results wouldn't be similar to what i got with the first tests.

[F51]

Hmmm, I thought that's what the voltage sense lines on my smart charger were for. Hopefully somebody smarter than me will pick up on this. MaineSail? BTrayfors?

[michaelmrc]

your correct some smart chargers have a dedicated voltage sense lines but they still connect to the battery. so yes in this case would have to go in to the sense line versus the charge line. i just meant that they work off the same principle sensing battery voltage smart chargers just have sophisticated microprocessors built in to determine their charging cycles.

[smac999]

the test doesn't make any sense. unless it has a sense wire which I've never seen on a charger before. the charger output should remain at 14v (because that is the voltage it is seeing and using to adjust) and the battery voltage would drop instead.

this is also how a diode behaves on an standard alternator. alternator remains at 14v but battery only sees 13.

so the 15v was at the charger before diodes? what the voltage at the batteries? they probably didn't go up.

[michaelmrc]

Voltage was tested at battery. Before diode 14.2 volts after 1 diode 14.8volts after 2 diodes in series 15.15 volts. standard charger no extra sense wire if you read the article on the smart Guage site it shows how adding a diode can trick the alternator into higher voltage output.

[alamoana]

BTDT with and Amplepower Smart charger, with 2 diodes in series to trIck the SC into equalzing batteries. It worked fine.

[michaelmrc]

Thanks for the info alamoana will have to try it with my smart charger. Did a few more tests this morning with different batteries same results. I used a 15amp load to discharge the battery for a few minutes then hooked up my test charger. Voltage climbed to 15.45 volts and held steady.

[smac999]

that still doesn't make any sense. you can't increase voltage across a diode. they drop voltage. the alt webpage is effecting the control wires. yours is direct in the output path. big difference.

if you have 2 diodes in series in the pos line between the charger and battery with correct polarity your charger would be at 14.2 and your battery would be at 13.

reverse polarity it just wouldn't charge and the charger would be at 14.2 and battery at 12.

can you draw a diagram of what you have? maybe I'm missing something.