320 Watt solar panel report

[coolfeet]

I want to share my latest success on my 320 Watt solar project for my E350 camping van. More Photos forthcoming.

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3 years ago I used at CTEK D250 S dual battery isolator connected to a Lifeline 80 amp battery. I have an ARB 60 quart freezer running off the battery. The CTEK was not functioning properly and barely kept the battery charged. After 2 weeks on the road, I connected the ARB to the cigarette outlet.

Next year, I added a 160 Watt solar panel. Again, I could not charge the battery. Lifeline advised me to take the battery to a dealer for free reconditioning.

Another year went by until we geared up for a month-long trip to Alaska and British Columbia. I tested the ARB on several weekend camping trips and everything seemed in order. I added a battery volt and amp meter. After 2 weeks on the road, I was back in the same boat. I bought a new 80 ah battery from Canadian Tire thinking I had a bad battery. No change in charging. I connected the ARB to the cigarette lighter again. It appeared that the charging voltage was never over 12 volts!

I contacted CTEK and they replaced the D250S for free. I tried the system out again over a 3 day weekend and noticed the batteries going low. I called an electrical engineer friend and he advised me to buy another 160 Watt solar panel and connected it in series to double the charging voltage. He mentioned that in his industry and experience, I was hitting the threshold voltage for charging the batteries for only 2 hours a day.

I just arrived from a 5-week cross country camping trip. Batteries stayed charged without any problems the entire trip. I did have a few days of dry camping in the woods without much sunlight. After 2 days, the batteries were getting low.

I want to mention that I connected 2 non-matching 80 ah AGM batteries in parallel. Both batteries were abused. I charged each separately before connecting them. Rather than tossing out $500 in batteries, I ran both through the CTEK 7.3 reconditioning cycle. I am hopeful of getting a few more years out these before purchasing new batteries.

Cosby Campground. Great Smoky Mountains National Park.

 

[jonyjoe101]

how much amps are you getting from the 2 panels when the sun is overhead? with 320 watts I would think about 16 amps charge power at least? I would check for voltage drop between controller and batteries. Fully charge the battery needs to read 14.4 volts (right at the battery terminals) , if you got voltage drop the controller could read 14.4 volts but your battery only reads 13.9 volts. The agms you got, need that 14.4 volts all the time to stay healthy. Anything below 14 volts and your only float charging. One thing I learned with solar is by cranking up the bulk/absorb voltage to 15 volts you get more amps going into the battery, if you have limited sunshine and need to fast charge them, take that voltage up, just monitor the voltage at the battery terminals, with solar you'll probably won't reach 14.4 volts, if you reach 14.4 volts too fast, then the batteries have lost capacity. Thats why I tell everyone to check for voltage drop, I was operating my system with .5 volts voltage drop for years, my battery never got a full charge, but the controller told me it did.

To me it looks like you got plenty of solar for your 160ah of batteries, as long as you don't drain them below 12.1 volts every day.

 

[luthj]

With voltage drop from the controller to batteries being so critical, and the panel voltage on a 300w high voltage panel being well over 20V, It makes sense to have the controller as close to the batteries as possible.