solar charger overvoltage

Thread Starter

captoro

Joined Jun 21, 2009
150
Hello.

I bought a Coleman solar charger with panel. The charger now charges higher them usual. About 17volts.. can't return it. The charging voltage should be 14,3v or about.
To bypass the issue. Can I simply add a capacitor and a 14.3v zener diode on the output to keep the voltage lower then 14,3v ? Anyone has a better idea?

Keh
 

Externet

Joined Nov 29, 2005
1,737
Did it ever deliver the proper 14V before to the same battery in same conditions ?
Repairing it would be the proper way instead of diodes bandaids and tricks, to ensure regulated charging. A higher voltage can yes, be brought down to fit your wishes but try the correct fix before.
Many 12V nominal solar panels do supply around 18V by themselves and come down in voltage while connected charging a proper battery. Make sure you are not confused. Solar panels are current driving sources, not voltage sources.
What is the charging current measured while shows 17V ?
Come back with schematics, guts pictures, how many cells in the panel ?
 
Last edited:

Thread Starter

captoro

Joined Jun 21, 2009
150
Did it ever deliver the proper 14V before to the same battery in same conditions ?
Repairing it would be the proper way instead of diodes bandaids and tricks, to ensure regulated charging. A higher voltage can yes, be brought down to fit your wishes but try the correct fix before.
Many 12V nominal solar panels do supply around 18V by themselves and come down in voltage while connected charging a proper battery. Make sure you are not confused. Solar panels are current driving sources, not voltage sources.
What is the charging current measured while shows 17V ?
Come back with schematics, guts pictures, how many cells in the panel ?
I just used that one charger to charge a car battery. It usually was almost empty when I charged it so I had no issue. Now I'm float charging it and my battery bubbles. Checked the voltage and it was 17v. Way too much. Maybe it was always like that. It came with a 50watt solar panel. I don't have any schematic of the device. I'm brainstorming the idea now on how to fix it. My friend has an almost identical Coleman charger and has the same issue.
Actually. I don't want to fix the device. I want to add an external device so it can output 14.10v
Ken
 

Externet

Joined Nov 29, 2005
1,737
Well, if that is what you want; to bring 17V down to 14V you need to substract 3V. That is about 5 Si diodes in series capable of passing the current you want.

Panel+17V------|>|-------|>|-------|>|-------|>|------|>|-------14V+battery
 

Thread Starter

captoro

Joined Jun 21, 2009
150
Well, if that is what you want; to bring 17V down to 14V you need to substract 3V. That is about 5 Si diodes in series capable of passing the current you want.

Panel+17V------|>|-------|>|-------|>|-------|>|------|>|-------14V+battery
Ok. This issue is also I get 17volt at full sunlight. When there is less. I get 14v. The output voltage varies vs the input Sunlight. That's why I was thinking zener diode.
But I guess with the maximum power of the panel....50watt. it would be around 4amp..

Ken
 

MisterBill2

Joined Jan 23, 2018
10,580
If you bought the charger new, it should have some specifications with it, other wise you will need to get the specifications for the model that you have. Amazon will be totally useless, Coleman may have some specifications available.
Battery charging does require a voltage higher than the battery rating, so the no-load output will be higher.
There may possibly be some adjustments available to alter the characteristics.
OR, you may have a totally manual charger, meaning that you must disconnect the battery when the desired level of charge is achieved. Most of my battery chargers are manual, so that when I observe the current drops I disconnect them. If that is the case, then the answer is to disconnect the battery when it is fully charged.

But certainly, read all of the instructions on how to use it.
 

bassbindevil

Joined Jan 23, 2014
238
Those panels often come with a charge controller which regulates the voltage to the battery. You can get one from eBay for under $10; search for solar charge controller. I bought one rated at 10A a couple years ago and used it with a friend's panel to top up his collection of stray 12V batteries. The LCD display shows voltage reasonably accurately, the USB outputs charged my phone OK.
 
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