CPAP machine w/ inverter. How much power?
Hi Folks, A little background. Not new to RVing, but starting to deal with battery issues more, now that I have a week long music festival coming up w/ no hookups. I decided that after last year, n...
Forum Discussion
Hi,
2 amps @ 120 volts via an inverter may translate to 20 amps @ 12 volts. If the Group 27's are fully charged and you do not wish to go below 50% state of charge they will run the cpap for about 4 hours.
Don't dream that three hours is enough generator time to get back past about 85% state of charge.
The chart above shows the amount of time it took a PD9155 (55-amp) converter set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.
14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.
13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.
13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge.
This is what is balanced and best for twin twelve volt batteries.
As it often doesn't cost a dime more to do this, I think it is worth the trouble.
If you wish to understand the "why" surf here:
correctly interconnecting multiple twelve volt batteries
Others may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?
2 amps @ 120 volts via an inverter may translate to 20 amps @ 12 volts. If the Group 27's are fully charged and you do not wish to go below 50% state of charge they will run the cpap for about 4 hours.
Don't dream that three hours is enough generator time to get back past about 85% state of charge.
The chart above shows the amount of time it took a PD9155 (55-amp) converter set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.
14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.
13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.
13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge.
This is what is balanced and best for twin twelve volt batteries.
As it often doesn't cost a dime more to do this, I think it is worth the trouble.
If you wish to understand the "why" surf here:
correctly interconnecting multiple twelve volt batteries
Others may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?
bgrasspkr wrote:
Hi Folks,
I just purchased 2 brand new Exide Group 27 Marine batteries to use( in parallel) exclusively for the unit. I know, Exides probably suck, just like every other Marine dual-purpose, but for 85 bucks a piece, I figured what the heck. I couldn't justify the more than double that for a true Deep Cycle like a Trojan, especially only using them maybe two or three times a year for boondock camping.
1. Do you think I am good with the 2 Group 27s for a good 7 hours straight, with one or the other inverter, w/ the CPAP?
