Solar and battery help
Good Morning. I am hoping someone can provide a simple answer or 4 for me. I just read a post on the TC forum about flexible, light weight 100 watt solar panels and love the look of this, I have a Nor...
Forum Discussion
Don't get all that excited with 100WATT SOLAR PANELS... A 100WATT Panel will only produce around 4-5AMPS DC CURRENT for the time they are in HIGH SUN. The rule of thumb is around 5-6 hours each day is the normal time you can expect full output of the panels. Out west in wide open country gives you more high sun of course...
Your SRM-27 with a Reserve Capacity of 160 minutes will only produce 12VDC Power@25 AMPS for around 160 minutes (2.7Hrs). Having two in parallel will raise this to around 5.3 HRS... If you do this your batteries will be drained to their 0% charge state or 10.5VDC. You really don't want to ever do this to your batteries and most of us respect the 50% charge state and I really get excited when my batteries drop below 12.0VDC. Most of us think continuing to drop below the 50% charge state will do harm to your batteries.
My thinking is to beef the battery banks and battery associated battery cables etc to run the thing you want to run when camping off the power grid so that you can operate things until 8AM the next morning when you are allowed to run a generator to re-charge your batteries...
To me adding solar panels only enhances this operation and perhaps you won't have to run your generator as long each day to keep up with battery drains.
All of us knows that in order to re-charge a 50% depleted battery it will take around 14.4VDC at a 20AMP DC Source for each battery in the battery bank. This will drop back to 13.6VDC after a two hour run and give you a safe 90% charge state on the batteries in around three hours total time. With a 90% charge state you can do the run off the batteries again for the next day/night battery run.
If by adding solar panels you can expect around 5AMP of charge current going into your battery bank and if you have enough panels you might get this up to around 15AMPS for 6 hours on your TC roof size. In 5-6 hours this will put back around 30AHs into your batteries. If you day/night run off the batteries is less than 30AHs then the solar panels will be great for you to have. You will never get behind the battery drain curve having them.
Of course this is not always guaranteed as some days will be cloudy and this could last several days where you won't get any charge at all that you can use. You would need to have the generator running your on-board converter/charger to replenish your battery charge for these days...
I have been playing this day/night run on my batteries for a few years and we get by pretty good with our routine with around 255AH Battery Bank capacity. This of course have to be re-charged each day starting at 8AM each morning with our 2KW Generator running our trailer and allowing the on-board converter/charger to bring them back up to their 90% charge state so we can do it all over again the next day/night run off the batteries.
My OFF-ROAD POPUP Trailer roof is much the same size as your TC ROOF and I am planning on adding two 120WATT Panels in the front and then a 240large panel on the rear side. This 480 Watts of solar should give me a good 14.4VDC @ 20AMPS for around 5-6 hours a day (160AHs) and really help me out keeping my battery bank drain so that using the generator will be minimal. Since my three batteries normally draw about 53AMPS DC current when first hit with 14.4VDC charge voltage I will have to use the generator for that first 0NE hour charge period. After the battery start tapering off the solar panels can deal with the charge source amps pretty good then. Then I can hopefully switch to the solar panels for the rest of the day to top off my battery bank to the 90% charge before the high sun goes away... This is going to be my basic routine at any rate when camping off the power grid.
This is my take on adding solar panels for our camping off the power grid routine. All of this takes planning... Others have different ideas on what to expect but I am pretty confident based on my few years of running entirely off the batteries this is what will happen for us when we finally get solar panels installed. We watch our BATTERY MONITOR PANEL like a hawk knowing when it hits 12.0VDC we have to shut it all down... This is planned to happen at 8AM the next morning when I can deal with it...
For your situation you may get by just fine having the solar panels and not get into your battery reserve capacity. What happens if it doesn't work like you have planned. Got to have a good PLAN B hehe... Not fun when lights go out at 10PM at night especially for needing the CPAP at night... For us a generator is must have item and as you know we folks that live on the East side of the US have all of the generator run time restrictions to deal with. So bigger battery banks and solar is good way to go...
Just adding another GP27 battery will only give you an additional 96AH of capacity. So you question is can you live on 192AHs of battery capacity especially when you can only use 96AHs of that total so that your batteries will not go below 50% charge state. Add up your DC power drain and how long you expect to use it and see how you want to be battery wise. i.e your CPAP draining 12VDC@3AMPS needing to run for 8 hours will consume 24AHs of capacity... Just considering that only leaves you 72Ahs for other 12VDC drains. Not much to play with. Watching TV for 6 hours will eat up at least 24AHs... Hopefully you have changed over to LED lights already.
Just passing along for food for thought on your end...
Roy Ken
Your SRM-27 with a Reserve Capacity of 160 minutes will only produce 12VDC Power@25 AMPS for around 160 minutes (2.7Hrs). Having two in parallel will raise this to around 5.3 HRS... If you do this your batteries will be drained to their 0% charge state or 10.5VDC. You really don't want to ever do this to your batteries and most of us respect the 50% charge state and I really get excited when my batteries drop below 12.0VDC. Most of us think continuing to drop below the 50% charge state will do harm to your batteries.
My thinking is to beef the battery banks and battery associated battery cables etc to run the thing you want to run when camping off the power grid so that you can operate things until 8AM the next morning when you are allowed to run a generator to re-charge your batteries...
To me adding solar panels only enhances this operation and perhaps you won't have to run your generator as long each day to keep up with battery drains.
All of us knows that in order to re-charge a 50% depleted battery it will take around 14.4VDC at a 20AMP DC Source for each battery in the battery bank. This will drop back to 13.6VDC after a two hour run and give you a safe 90% charge state on the batteries in around three hours total time. With a 90% charge state you can do the run off the batteries again for the next day/night battery run.
If by adding solar panels you can expect around 5AMP of charge current going into your battery bank and if you have enough panels you might get this up to around 15AMPS for 6 hours on your TC roof size. In 5-6 hours this will put back around 30AHs into your batteries. If you day/night run off the batteries is less than 30AHs then the solar panels will be great for you to have. You will never get behind the battery drain curve having them.
Of course this is not always guaranteed as some days will be cloudy and this could last several days where you won't get any charge at all that you can use. You would need to have the generator running your on-board converter/charger to replenish your battery charge for these days...
I have been playing this day/night run on my batteries for a few years and we get by pretty good with our routine with around 255AH Battery Bank capacity. This of course have to be re-charged each day starting at 8AM each morning with our 2KW Generator running our trailer and allowing the on-board converter/charger to bring them back up to their 90% charge state so we can do it all over again the next day/night run off the batteries.
My OFF-ROAD POPUP Trailer roof is much the same size as your TC ROOF and I am planning on adding two 120WATT Panels in the front and then a 240large panel on the rear side. This 480 Watts of solar should give me a good 14.4VDC @ 20AMPS for around 5-6 hours a day (160AHs) and really help me out keeping my battery bank drain so that using the generator will be minimal. Since my three batteries normally draw about 53AMPS DC current when first hit with 14.4VDC charge voltage I will have to use the generator for that first 0NE hour charge period. After the battery start tapering off the solar panels can deal with the charge source amps pretty good then. Then I can hopefully switch to the solar panels for the rest of the day to top off my battery bank to the 90% charge before the high sun goes away... This is going to be my basic routine at any rate when camping off the power grid.
This is my take on adding solar panels for our camping off the power grid routine. All of this takes planning... Others have different ideas on what to expect but I am pretty confident based on my few years of running entirely off the batteries this is what will happen for us when we finally get solar panels installed. We watch our BATTERY MONITOR PANEL like a hawk knowing when it hits 12.0VDC we have to shut it all down... This is planned to happen at 8AM the next morning when I can deal with it...
For your situation you may get by just fine having the solar panels and not get into your battery reserve capacity. What happens if it doesn't work like you have planned. Got to have a good PLAN B hehe... Not fun when lights go out at 10PM at night especially for needing the CPAP at night... For us a generator is must have item and as you know we folks that live on the East side of the US have all of the generator run time restrictions to deal with. So bigger battery banks and solar is good way to go...
Just adding another GP27 battery will only give you an additional 96AH of capacity. So you question is can you live on 192AHs of battery capacity especially when you can only use 96AHs of that total so that your batteries will not go below 50% charge state. Add up your DC power drain and how long you expect to use it and see how you want to be battery wise. i.e your CPAP draining 12VDC@3AMPS needing to run for 8 hours will consume 24AHs of capacity... Just considering that only leaves you 72Ahs for other 12VDC drains. Not much to play with. Watching TV for 6 hours will eat up at least 24AHs... Hopefully you have changed over to LED lights already.
Just passing along for food for thought on your end...
Roy Ken
