parallax power supply 7345ru parts PWM
My 7345 is not charging the coach batteries but does supply 12power to all accessories. The transformer, fan and relays work fine. Think i need a PWM circuit for it. Contacted PP tec support and th...
Forum Discussion
Sal,
Hmmmm....
1) Your sensing line mod will set the 7345's Vout value in accordance with the diode and summing point configuration behind the error op amp.
2) Your sensing line mod will hold the voltage on the battery terminals to Vout.
3) Your sensing line serves to force Vout on the battery terminals all the way up to 45 amps coming out of the 7345.
4) Your mod will do 3), above, regardless of the awg size of the main cable between the 7345 and the batteries. It will do this until failure of the cable if one was to use an unfused cable that just happens to be too small to carry 45 amps for long periods without over-heating.
5) Even though 8 awg cabling will of course carry 45 amps, some folks may try your mod using existing RV cabling smaller than 8 awg and think everything is OK. Hence my warning concerning use of your mod with small awg cabling that is not fused to the maximum that the cable can carry over time if that maximum is less than 45 amps - regardless of internal 45 amp fusing inside the 7345.
I'm not aware of any accusations or bellyaching. You did your mod to eliminate line losses between a 7345 and batteries it's charging ... plus (I think - per your 2009 explanations) raise the fixed output of a 7345 to higher than 13.8 volts.
For my AGM battery situation I don't want higher than 13.8 volts coming from my fixed voltage converter and I don't want to mess around modifying anything. I merely want a 7345, as delivered, to hold close to 13.8 volts on it's terminals all the way up to 45 amps ... as it's advertised performance curves says it will approximately do. I'll take care of voltage drop in the lines between it and the batteries - and I believe I've already stated earlier that I'll take the responsibility for doing this. BTW, this is easy to do safely because, as I've already stated, a 7345's terminals are big enough for up to about 2 awg cables and loss with 45 amps through 2 awg cables would be acceptably small for my needs.
In the final analysis, your mod is a great hobby project to demonstrate getting around a product's deficiencies. In the long run, I'll probably do what MEX and BFL13 do - use an inexpensive high voltage charger in parrallel with a 7345 to up the current a bit when charging my AGM batteries, as they charge so fast anyway even with only voltages in the 13.8 range.
BTW, thanks again for the quick math analysis you did in 2009 showing how low the internal resistance really was on the somewhat unusual Interstate wheelchair batteries I'm using!
Hmmmm....
1) Your sensing line mod will set the 7345's Vout value in accordance with the diode and summing point configuration behind the error op amp.
2) Your sensing line mod will hold the voltage on the battery terminals to Vout.
3) Your sensing line serves to force Vout on the battery terminals all the way up to 45 amps coming out of the 7345.
4) Your mod will do 3), above, regardless of the awg size of the main cable between the 7345 and the batteries. It will do this until failure of the cable if one was to use an unfused cable that just happens to be too small to carry 45 amps for long periods without over-heating.
5) Even though 8 awg cabling will of course carry 45 amps, some folks may try your mod using existing RV cabling smaller than 8 awg and think everything is OK. Hence my warning concerning use of your mod with small awg cabling that is not fused to the maximum that the cable can carry over time if that maximum is less than 45 amps - regardless of internal 45 amp fusing inside the 7345.
I'm not aware of any accusations or bellyaching. You did your mod to eliminate line losses between a 7345 and batteries it's charging ... plus (I think - per your 2009 explanations) raise the fixed output of a 7345 to higher than 13.8 volts.
For my AGM battery situation I don't want higher than 13.8 volts coming from my fixed voltage converter and I don't want to mess around modifying anything. I merely want a 7345, as delivered, to hold close to 13.8 volts on it's terminals all the way up to 45 amps ... as it's advertised performance curves says it will approximately do. I'll take care of voltage drop in the lines between it and the batteries - and I believe I've already stated earlier that I'll take the responsibility for doing this. BTW, this is easy to do safely because, as I've already stated, a 7345's terminals are big enough for up to about 2 awg cables and loss with 45 amps through 2 awg cables would be acceptably small for my needs.
In the final analysis, your mod is a great hobby project to demonstrate getting around a product's deficiencies. In the long run, I'll probably do what MEX and BFL13 do - use an inexpensive high voltage charger in parrallel with a 7345 to up the current a bit when charging my AGM batteries, as they charge so fast anyway even with only voltages in the 13.8 range.
BTW, thanks again for the quick math analysis you did in 2009 showing how low the internal resistance really was on the somewhat unusual Interstate wheelchair batteries I'm using!
