Capebuild wrote:This thread has gotten me to re-think my battery decision or to at least make double sure of my decision.Socal Tom wrote: For the typical weekend warrior the occasional dip down to 20 or 25% probably won’t make a difference.
For the sake of discussion, lets say your trailer will not only see the life of a "weekend warrior", but will be on the road for a month at a time, maybe even longer.... and maybe twice a year. And let's also say there are numerous week+ plus long trips. So more than weekend get aways. And given this usage if one didn't really want to have to always be concerned about whether their battery was going to hold up or be concerned about running it below the threshold (define that as you may)..... would a lithium make sense?
Thanks
John
It would depend on a couple of things
1) The most important question is "How much reserve power do you have?" ( In my case a 100AH battery would have about 1250 watt hours max capacity, at 50% I have 625 to play with, I use about 250 per day ( assuming no solar) so I can go about 2 days with no sun before I drop below 50%, the third day with no sun gets me into the yellow zone, a 4th day would be bad.
2) How quickly can I recharge?
My solar setup makes about 450watt hours on a sunny day. So if I go 2 days with no charging, I can make it up in one sunny day.
3) How frequent are days with no sun? I'm in So California, so I rarely have 2 days with no sun . So the probability that I need to go 3 days and take it down to 25% would be low ( and there are things I can do to conserve if that happens).
4)- Since my battery is lead acid, I can use TV charging in a pinch. Its not fast, but it does work. I've tested it with my Baylite meters and the charging I get provides enough power to power my 12V fridge and put 6 to 10 watt hours back into the battery per hour.( which is about the same as the standard 120V battery charger). I'm assuming if you are going on the road for a month it means driving frequently, so if you are without sun, you can at least reduce the load on your battery while driving.
So for me to justify a lithium battery, It would probably be about size and weight.
Lets say that I used more like 500 watt hours per day. Then I would only have 1 day reserve power, so 1 day without sun would get me near 50%. If I expected to be without solar charging for more than one day frequently, then I need more battery capacity. If I set my reserve power at 1000 watt hours, ( 2 days reserve ) then with Lead acid I would want about 160 AH of battery capacity. But I didnt have space or the weight was important, then with LIPO you could get by with a 100AH battery ( assuming 13V nominal and 30% min charge). But the LIPO reserve is a hard cut off. If you go 2 days without sun, you are out of power. With the lead acid, the 50% is a soft cut off, you can still go lower if you need to .
It seem's like your real concern is worrying about the state of charge on your battery. Here is my suggestion. Install some kind of battery monitor like the Baylites https://www.amazon.com/bayite-6-5-100V- ... B013PKYILS
I'm sure there are better ones, but I have 2 of these. One monitors power in one monitors power out. You can set alarms ( just flashing, no sound) . I have mine set at 12.2 volts ( roughly 50% for a lead acid battery). Then most of my power goes through my solar charger, which will cutoff power if voltage goes below 11.9 about 40%.( fridge doesn't go through here, but has a built in voltage cut off). If the flashing alarm goes off, then I make sure we aren't wasting power and I verify the solar is working properly, and I will set up TV charging if necessary.( I carry jumper cables, so I can always hook the cables between the TV and the battery directly to speed the charging). For short trips If this occurs I'm probably packing up to go home anyhow.
If for some reason I don't notice the flashing alarm, then when the lights stop working at 40% I notice for sure.
However, what really happens.
Once you put in the Baylite meters, you start watching them. ( hourly or less). You realize that when the sun is up your battery voltage stays above 12.4 almost constantly, and that during the night you use very little power ( except the nights I hook up a portable video projector), and when you wake up the power is still 12.3 or higher. I never get below 20% with my battery on a sunny day.
I think in your case, if you were on the road for a month, you would probably spend at least sometime in camp sites with power ( and showers), which also gives the option for plugging in and charging.
So in the end, for a towed trailer I think the easiest option is lead acid, it can be charged by the TV easily and the 50% cut off is a soft cutoff, vs a hard cutoff for LIPo. However, it size and weight are more important than cost, then LIPO makes sense, but I would include the ability to charge with my TV if I'm really concerned about not having enough sunny days.