Solar Battery Tender vs Battery Shut Off

[BroRobin]

Looking to add either or both of these items.
I keep my Eagle 318RLS at home in my yard. I do not have a 30amp pedestal/supply for the TT, so a couple of days before a trip I use a super heavy extension cord to plug in the TT to charge batteries and cool the refrigerator down before loading. I’ll still do this to chill the ’fridge but I want to get the most life out of the batteries without them drawing them down completely between trips.

Here’s the Questions:
1. If you were to add only one of these two items, which would you choose and why?
2. With a battery shut off disallowing parasitic draw, how long will healthy charged batteries hold the charge.
3. With a solar battery tender, can I assume it’s safe to leave it connected 24/7 to maintain and “tend” the batteries?
4. Will 1 solar battery tender charge both batteries? If so what strength should I look for? Also how to connect 1 charger/tender to both batteries?
5. Would both a shutoff and solar tender/charger be advisable?

Thanks for the anticipated help.

[azreddot]

I'd say both cutoff and battery tender.

I installed a battery cut-off after my first pair of batteries died in less than 2 years from purchase. At that time I installed a cut-off switch and occassionally used the battery tender off my boat to top off the 12v. Apparently not often enough because at 2.5 years later the 2nd set were beyond saving and I had to buy another pair this summer. Lesson learned, I'll be setting up a regular schedule to 'top them off' once a month.

[Duke4857]

Turn off everything and leave it plugged in if you can find a 10 gauge cord if you can. Weather protect the plug ins. I have a dedicated 20 amp plug ran to the TT and leave it plugged in all the time. I just check the water in the batteries once a month. The distance I have to run power to the trailer would take 8 gauge wire to run a 30 amp plug. I have a 20 amp and 10 gauge wire. I just do not run the A/C and microwave at the same time. One or the other never both. Just what I do.

[tennistime99]

If I were to choose just one I'd probably go solar. It will work anywhere you have sun, not just at home.

I installed an SAE plug, positive on one battery and negative on the other for 2 batteries in parallel. I have a 100 watt solar suitcase with mc4 to SAE adapter. The solar charger has 4 stages and works with 4 different battery types. I use it to charge the battery I take camping for my CPAP as well.

A disconnect would help minimize drain, but doesn't give anything back out on the road.

[distracto]

I would do both. Cut off to remove parasitic draw while camping, and to isolate the battery to only be charged when at home.

Get a plug in noco charger like this one https://www.amazon.ca/dp/B07W3QT226 and hook it up to the battery when at home, and then disconnect the battery from the trailer. This ensures that the battery is only getting maintained by the noco and not both the trailer AND the noco.

Depending on the quality of the solar charge controller, you can trust it to run through the 4 stages of charging the batteries, however the noco running while the batteries are disconnected will make sure your batteries are maintained properly.

Solar power comes and goes with direct sunlight, the noco plugged into a standard 15 amp plug will run regardless of clouds and short winter days.

Just my 2 cents

[abbttb]

I have both on our TT. I have a solar maintaner by Coleman mounted on the top of our propane tank cover. When the trailer is in storage, I shut off all power to the trailer to elimate draws and the solar maintainer keeps our batteries up. This is the second TT we have setup this way and our batteries have always had a charge when we pull the TT out for a trip.

Coleman site
https://sunforceproducts.com/product...-maintainer-2/

[abbttb]

I use both options on our TT. I have a battery shut off to eliminate all draws while in storage. And I have a Coleman solar maintainer mounted on top of the propane tank cover that keeps a charge on our batteries. I have had this setup on two TT and we have always had a charged battery when we pull out for a trip.

Coleman site
https://sunforceproducts.com/product...-maintainer-2/

[sciencenerd]

Originally Posted by BroRobin

Looking to add either or both of these items.
I keep my Eagle 318RLS at home in my yard. I do not have a 30amp pedestal/supply for the TT, so a couple of days before a trip I use a super heavy extension cord to plug in the TT to charge batteries and cool the refrigerator down before loading. I’ll still do this to chill the ’fridge but I want to get the most life out of the batteries without them drawing them down completely between trips.

Here’s the Questions:
1. If you were to add only one of these two items, which would you choose and why?
2. With a battery shut off disallowing parasitic draw, how long will healthy charged batteries hold the charge.
3. With a solar battery tender, can I assume it’s safe to leave it connected 24/7 to maintain and “tend” the batteries?
4. Will 1 solar battery tender charge both batteries? If so what strength should I look for? Also how to connect 1 charger/tender to both batteries?
5. Would both a shutoff and solar tender/charger be advisable?

Thanks for the anticipated help.

My trailer, when everything is off, has a base power draw of about 0.5 A. That means you need to replenish about 12 Ah a day through solar, better go for 20 Ah, plus minus some loss. A 100 W panel gives you about 6-7 A in full sun, maybe 0.5-1.5 A when cloudy. So, with having to account for multiple days without sun, I would say a 50 W solar panel is absolute minimum, better to have 100 W. That means a small solar battery tender is not going to do it, unless you also have a battery switch that can turn off ALL loads.

[TCNashville]

I keep my camper in a storage facility. I installed a battery cutoff at the box a few years ago. Recently I purchased a 7.5 watt solar charger to keep the battery topped off between trips and it seems to do a good job. I still have the original Excide battery that came with the camper which is now 8 years old.

[Bob K]

Here’s the Questions:
1. If you were to add only one of these two items, which would you choose and why?

If I have access to a standard household receptacle I always prefer the always-on performance of shore power versus solar.

Through a dogbone, I run a heavy duty extension cord to the trailer from a standard 15A household receptacle in my garage. This powers the charge controller and keeps the coach battery at the proper non-gassing float charge voltage (about 13.2V). I also have a BatteryMINDer that tends and desulfates ("equalizes") the battery. The pigtail is connected directly to the battery. If I don't feel like running an extension cord to shore power and using the coach's charge controller, I'll just connect the BatterMINDer directly to the battery. Its 1.5A output and float voltage are more than sufficient to offset any parasitic drain, so no battery disconnect necessary.

2. With a battery shut off disallowing parasitic draw, how long will healthy charged batteries hold the charge.

A 100Ah battery will be completely dead (discharged to 50Ah, or 50%) in approximately 208 days. Discharge is pretty linear from what I understand. https://www.themechanicdoctor.com/ho...ry-sit-unused/

Sulfation via lead sulfate buildup is the primary killer of batteries, which occurs anytime the battery isn't at 100% SOC. Hence the reason we use battery tenders/float chargers: Lead sulfate doesn't form on a battery at 100% SOC. "Topping up" the battery once per month still allows the battery to be less than 100% SOC for most of the month, so sulfation will slowly build up and eventually prevent the battery from accepting a charge.

3. With a solar battery tender, can I assume it’s safe to leave it connected 24/7 to maintain and “tend” the batteries?

Yes so long as the solar powered battery tender is designed to output the proper float charge voltage of around 13.2V. If it doesn't come with a built-in charge controller and just shoots whatever voltage and amperage it has available into your battery, it'll eventually boil off the electrolyte via hydrolysis.

4. Will 1 solar battery tender charge both batteries? If so what strength should I look for? Also how to connect 1 charger/tender to both batteries?

Yes. If the batteries are connected together in parallel with no intervening switches, any charge controller will just see them as 1 giant 12V battery. Connect the positive clip to either positive terminal and connect the negative clip to either negative terminal.

5. Would both a shutoff and solar tender/charger be advisable?

I don't bother with a battery cutoff because I have shore power available right next to the trailer for use either through the coach charge controller or with a separate BatteryMINDer, and either of those is more than capable of offsetting the coach's parasitic draw.

If my trailer were elsewhere, I'd install a battery cutoff switch so that I didn't have to manually disconnect the terminals from the battery (to stop coach parasitic drain) every time I came home after a camping trip.

If your solar charger isn't up to the task of offsetting whatever parasitic drain your coach causes, then yes a cutoff would be advisable. That way the solar charger only has to offset the battery's own parasitic drain (about 10mA/h) instead of also making up for the coach's parasitic drain. This would let you get away with using a much smaller output solar tender.

Considering the heavy charge and discharge abuse that a coach battery experiences (especially if one boondocks a lot) and their concurrent propensity to sulfate, I'm a big fan of the desulfation feature available on BatteryMINDer chargers and tenders.

[Big1]

I turn my battery shut off and I install this what did it for me is when my wife and I went out to pick up our fiver to go on a trip my battery was totally dead so we was out to the storage for about 1 hour or more just try to charge up my batteries.

So I install the solar for my batteries and I haven't had any more problem, every time I go out to storage I can turn on my batteries shut off back on and I am good to go.

[Big1]

It's expensive but to me it's well worth it, this is what you need if you are going to charge two batteries in parallels. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1