Solar top off system

[FR_off_road]

Hello,
I started car camping with my truck (Chevy Suburban) and noticed that after a few days the battery ran low. Opening the door and closing it even with light off takes power. Same with power door locks and windows, which are even more hungry. So far this has been camping with friends so a jump is possible but I want to go solo.

Need:

1. Top off car battery and maintain SOC. Required total power unknown but not huge. Power draw is from door locks, infrequent cabin light. Some window roll down and up. SWAG is 30 to 40 watts panel.
2. Charge control a must. Can’t risk battery failure in the field.
3. Batter soc display. Prefer LCD display. (Part of controller?)
4. When charging from solar a USB 5v outlet can be powered. Can top off power bank or phone. Not critical as I can use my ryobi battery packs with 5v converter
5. Small packable system. Mostly don’t want to deal with a full install this year.
6. Nice to have. When battery is full switch over and power other devices like fans, usb, misc. This could expand later to a house battery.

Solution:

This is a proof of concept system and a stop gap measure. Value system that could be repurposed as a small solar generator would be ideal. I’m saving up for making a toy hauler diy trailer. Getting solar experience here before I create that system is a plus.

I checked some top off systems that plug into the outlet but they do not seem to have charge controllers. This could be a solution but I did not find one that protects the battery or is in the 30W range. I found an inexpensive Renology setup in the 30W range but not sure if that’s the way to go yet.
I noticed that most system charge controllers seem to charge the battery and when no solar power switch to powering an output. This is not in line with primary battery and then auxiliary output configuration I want. And it seems I am not looking for the right term when I searc, since I am not finding them.


Would appreciate any insight with similar setups.
Thank you.

 

[NatersXJ6]

At 30 watts, 2.2-2.5 amps in ideal sun?, it seems unlikely that you could damage a Suburban battery with occasional use. You would be lucky to push 10 amp-hours a day into the battery.

 

[Hegear]

Check out battery tender brand, there panels have built in solar controllers designed for this purpose.

 

[FR_off_road]

Yes goal is to make up door locking windows and parasitic loads.

 

[telwyn]

Check out battery tender brand, there panels have built in solar controllers designed for this purpose.

Thanks for this tip. Was searching for this topic, found this post and ordered the Battery Tender 35 watt panel with the solar charger controller. Will use it on the roof rack of my Land Rover Lightweight to keep my batteries topped off.

 

[rruff]

That's the math, a ten amp hour charger takes 80 hours to completely charge a very dead battery.

An 800A car battery is nowhere near 800Ah. Maybe 50Ah? They only deliver 800A for a few seconds. And the units for the charger will be in A, not Ah.

1. Top off car battery and maintain SOC. Required total power unknown but not huge. Power draw is from door locks, infrequent cabin light. Some window roll down and up. SWAG is 30 to 40 watts panel.
2. Charge control a must. Can’t risk battery failure in the field.

Considering that most of us do fine without any of this, 30-40W seems huge.

Lead acid batteries are OK being trickle-charged when full. I'd find out what the max trickle is for the battery size/type you have and go with that.

 

[crazysccrmd]

An 800A car battery is nowhere near 800Ah. Maybe 50Ah? They only deliver 800A for a few seconds. And the units for the charger will be in A, not Ah.

You’re not wrong but in this case it’s really semantics. An 8amp charger (assuming at full rate and not trickling) still provides 8ah of power.

 

[rruff]

You’re not wrong but in this case it’s really semantics. An 8amp charger (assuming at full rate and not trickling) still provides 8ah of power.

It's not semantics, it's science and math. And in this case the conclusion of needing 800Ah to charge a car battery was wildly inaccurate.

8A for 1 hour is 8Ah. 8A for 10 hrs is 80Ah. And the units of power are watts. Amps are not energy or power... but if we multiply by voltage, then we get power. And if we multiply by voltage and time, we get energy.

 

[crazysccrmd]

It's not semantics, it's science and math. And in this case the conclusion of needing 800Ah to charge a car battery was wildly inaccurate.

8A for 1 hour is 8Ah. 8A for 10 hrs is 80Ah. And the units of power are watts. Amps are not energy or power... but if we multiply by voltage, then we get power. And if we multiply by voltage and time, we get energy.

Again, not wrong but overly complicating things for basic users. An 8amp charger delivers 8ah of charge per hour (the basic math). For the basic user there is no difference to what that means to them.

 

[Dave in AZ]

Again, not wrong but overly complicating things for basic users. An 8amp charger delivers 8ah of charge per hour (the basic math). For the basic user there is no difference to what that means to them.

No, I'm going to politely disagree with you here. What overly complicates things for basic users, and confuses them until someone explains it correctly, is people posting incorrect units, terms, nomenclature like you are. Instantaneous power use is Watts, stored power is Watt-hrs. If you use Amp-Hours, state the voltage or it's meaningless. You can't go wrong by using the correct units and terminology... takes less time to do it right, than trying to explain on here why it's OK for you to use wrong terms.
Amps and Ah only have meaning, as regards power storage, if the voltage is known and stated. With euro systems at 24V, most trucks at 24V, many folks using both 24V and 48V batteries now, 12-14V can't and shouldn't be assumed.
@rruff