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power management
Hi,
While waiting and planning for new LD, I read a lot about power management and even created a spreadsheet on how much power I will need. All of that was theoretical stuff to make sure that bipap/cpap machine can survive. I want to share actual usage data.

I added two additional batteries and a battery monitor and we do have two solar panels I think 120W each..,, We are average user of electric powers use lights when needed but are careful to turn them off (I know they are not power hungry but just habit), watch couple hours of tv if cell or tv signals are present and whenever needed we use the roof fans. We also have two small fans which we use as well. When I am lazy we run the furnace otherwise I bring the 5 gal propane tank from toad and use cat heater. Beside two additional batteries I do carry two 500 watt power stations with built in inverter and charger. Reason for two is to have manageable weight.

For Bipap machine (I am using it for about years and do have pretty high pressure settings) I need 24V DC and I bought a 12V DC to 24V DC converter to save on inverter overhead. I use battery pack for the bipap machine and if I turn off humidifier and tube heater for 8 hours of use I use 20-25% of 500 Watt battery pack. Between two battery pack I am set for at least 8 days. I also have portable 100W solar panels which I rarely use to charge battery pack. For those nights with stuffy nose, if I turn on the humidifier and tube heater, I do wake up with battery pack completely exhausted. Sometime we do use battery pack to have some outside decoration lights as well for longer stays.

As for regular RV usage, if we turn off all the optional equipment, we need .7-.8 amp for monitors etc. With regular use of lights, tv, fans etc., I do not see battery charge going below 90% in early am and of course when sun comes out it charge the batteries. Even with sites with shades or during cloudy days when we hit 80% mark we turn on the generator to charge the battery and in last one year there are only one or two times when we had to turn on the generator to charge the battery.

Generator put about 20-25 amp in the battery and when truck is running it is much more ... we usually stay 3-4 days in a place and longest we stayed in a place was a week without electricity and we were fine.

Hope this information will help with some newbie like me.

PS: I thought I will have to get more expensive lithium batteries along with other infrastructure components in future but with data so far, even when these batteries come to end of life, I don't think regular use require more elaborate setup (at least from our point of view). I also question the wisdom of adding two additional batteries and associated weight. Two 500W portable solar generators are doing the magic. Just one person's view of limited experience.

Regards,
Re: power management
Reply #1 –
Heated CPAPs can use a bit of power. you might be fine with the two 115-watt panels for summer travel but for winter use, with short days and limited sunlight, consider adding another solar panel or two.
Your LD has a big battery pack, it can handle a much larger solar array.

Never met anyone who complained about having too much solar.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: power management
Reply #2 –
Hi Muhammad;  I've been really happy with my Lithium conversion using two SOK-206 batteries. Almost the same footprint as GC2's with a little bit taller batteries. About the size of T-145 batteries.  At 48 pounds, each is 14 pounds lighter than the 62 pounds of one 6 volt T-105.  For your needs, you can fit two in the battery box and one inside just next to the two.  That would give you 500 AH of useable power available. (80% Depth of Discharge) that wouldn't damage the batteries.  They are 12V. (actually 13.4V most of their discharge curve) and can all be hooked up in parallel. A good battery charge status information is essential, since it is hard to estimate their charge level. 
    As Larry said, having at least 400 watts of Solar is handy. You have a large roof, so more, in the 600-700 Watt range is easy to do. I don't foresee any major improvements in PV efficiency on the horizon.  As noted, you won't actually get 400 watts out of a 400 Watt array, but my two SOK's are fully charged by 10:00 in the morning most times. My energy needs are modest, but  with a good converter you can maximize the run time of a generator. The LiF batteries charge much faster that WLA, and can accept power at a rapid pace until the built in BMS controllers shut off charging.  I still haven't hooked up my 60Amp DC to DC charger. With your larger DC alternator than my 130A, you can utilize that charge also, and may not need to run the generator except for air conditioning.
    While the cost seems high, in 22 years I've been through at least 4 sets of WLA  batteries. If those had been AGM's it would have cost more that these two SOK's.  Each SOK is more useable power than two Trojan 105's. 
     RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: power management
Reply #3 –
Quote from: Larry W  - 
Heated CPAPs can use a bit of power. you might be fine with the two 115-watt panels for summer travel but for winter use, with short days and limited sunlight, consider adding another solar panel or two.
Your LD has a big battery pack, it can handle a much larger solar array.

Never met anyone who complained about having too much solar.

Larry

Thanks Larry. I will take your advice if I find a place or person who can add more panels. I think factory put some reinforcement to put panels but perhaps I can get light weight panels which can use glue or some other ways to put on the roof without making holes or any other major structure change. Second issue may be existing wire gauge … will wait to find a person who knows how to add two panels without creating any intended issues. No emergency for now … alternator does charge batteries unless we stay at one place too long.

This motorhome is proof of concept and am learning …

Regards,
Re: power management
Reply #4 –
Ron B,
As for lithium conversion, it will also need  converter and perhaps solar controller reprogramming and may be few more components. I was paying attention when Ken and other members got upgrades done.

Point I was making was that for our use stock batteries are sufficient. For Bipap I got portable light lithium battery packs which are also helping with electronic toy charging and occasional decorative lights for few hours.

I understand the benefits of lithium and if given option at design time I will definitely go for it but stock AGM is good enough for our needs for now and I do not see making any major change to well designed electrical system.

I just wanted to share my limited experience. I was looking for similar input in past and hope this information will be useful for somebody in future.

Regards,

Quote from: RonB  - 
Hi Muhammad;  I've been really happy with my Lithium conversion using two SOK-206 batteries. Almost the same footprint as GC2's with a little bit taller batteries. About the size of T-145 batteries.  At 48 pounds, each is 14 pounds lighter than the 62 pounds of one 6 volt T-105.  For your needs, you can fit two in the battery box and one inside just next to the two.  That would give you 500 AH of useable power available. (80% Depth of Discharge) that wouldn't damage the batteries.  They are 12V. (actually 13.4V most of their discharge curve) and can all be hooked up in parallel. A good battery charge status information is essential, since it is hard to estimate their charge level. 
    As Larry said, having at least 400 watts of Solar is handy. You have a large roof, so more, in the 600-700 Watt range is easy to do. I don't foresee any major improvements in PV efficiency on the horizon.  As noted, you won't actually get 400 watts out of a 400 Watt array, but my two SOK's are fully charged by 10:00 in the morning most times. My energy needs are modest, but  with a good converter you can maximize the run time of a generator. The LiF batteries charge much faster that WLA, and can accept power at a rapid pace until the built in BMS controllers shut off charging.  I still haven't hooked up my 60Amp DC to DC charger. With your larger DC alternator than my 130A, you can utilize that charge also, and may not need to run the generator except for air conditioning.
    While the cost seems high, in 22 years I've been through at least 4 sets of WLA  batteries. If those had been AGM's it would have cost more that these two SOK's.  Each SOK is more useable power than two Trojan 105's. 
     RonB