Hi everyone, I'm new to this forum and this is my first post. I have a small 14 foot boat I use to get across the lake to my cottage. I recently upgraded my outboard motor from 12 V to 24 V, but I can't get my system to work. The batteries run dry, and I can't tell whether the charge controller is charging them at all. My system is: **4 x 50W panels, two pairs in series, then connected in parallel. **A simple PWM charge controller that automatically detects whether my batteries are 12V or 24V. **2 x 105 amphour deep cycle batteries in series. **An 80lb thrust 24V Minn Kota motor, max amp 56. Here's what happens. I get a 25.3V reading from the batteries, then connect them to the controller. I get a 44V reading from the panels. I connect them to the controller and the voltage immediately drops to 33V. I get a flashing green light indicating charging and a faint red light on the "sun" (i.e. PV) monitor. The motor runs with full strength, but gradually slows, and the voltage of the batteries drops. On a good day the boat gets 8 hours of sun! Can anyone tell me what I can do?
Charge system failing
- Thread starter JackJohn
- Start date
It wasn't just me using the boat so it's hard to say. I'm guessing about an hour? possibly a bit more...
nosys70
Solar Enthusiast
- Joined
- Jan 15, 2020
- Messages
- 839
about 1 hours seems normal.
a 56 Amps motor will run about 90 min on a 105Ah , if they are new, fully charged.
Since you discharge at fast rate , it will be less, especially if it is lead battery.
the question is , what were your expectations ?
a 56 Amps motor will run about 90 min on a 105Ah , if they are new, fully charged.
Since you discharge at fast rate , it will be less, especially if it is lead battery.
the question is , what were your expectations ?
Running for an hour on the battery is fine, but then the battery doesn't recharge! Do I maybe need a better charge controller? The guy who sold me my system said the charge controller automatically decides on 12V or 24V depending on the battery. Is it possible that running the motor brings the batteries down to below 12V, then the controller thinks it's only a 12V system and won't recharge it?
MisterSandals
Participation Medalist
You should NOT discharge 24v lead acid batteries below 24v. If you discharge them below 12v they become compromised very quickly.
And yes, your charge controller only has the battery voltage to determine if it should charge to 12 or 24v. In the event it can be set from automatic to 24v, that should get you charging to 24v.
I've got a really basic controller, so I can't tell the rate. If the charge is too slow, do I need more panels? Would you upgrade the controller AND get more PV wattage?
nosys70
Solar Enthusiast
- Joined
- Jan 15, 2020
- Messages
- 839
200w panels on paper is more 130W in reality. so to charge a 105Ah 24V battery that is 2520W, you need 4 hours.
So you batteries must be connected to panels at the right time (when sun is at is best) for 4-5 hours,
and you need a charger able to deliver about 25 Amps.
if you do not use panels but shore power, you can take more time to charge (at night for example) and span the charge over 10 hours for example, so you would need a less powerfull charger (like 12Amps only)
Seems you installation is bottlenecked somewhere.
So you batteries must be connected to panels at the right time (when sun is at is best) for 4-5 hours,
and you need a charger able to deliver about 25 Amps.
if you do not use panels but shore power, you can take more time to charge (at night for example) and span the charge over 10 hours for example, so you would need a less powerfull charger (like 12Amps only)
Seems you installation is bottlenecked somewhere.
Right. From what you say it sounds like I need more wattage in the PV and a better controller. I only 80W now. And my controller is so basic, I cant see the amperage charge. But I'll bet it's way less than 12 amp.
PHoganDive
Solar Enthusiast
80 watts at 24 volts is 3.33 amp charge rate.
Thanks @nosys70 and @PHoganDive. I'm finding it really hard to work the numbers. Getting confused between the amps and the amp hours. Is this right--- my two 105 amp hour batteries in series give me 105 amp hours at 24V. If I run the motor for 15 minutes and it draws the full 56 amps it's rated at, then I've used 14 amp hours (1/4 of a full hour at 56 amps). So I've basically taken those 14 amp hours out of the batteries and need to replace them. Charging from my 80 W panels at 3 1/3 amps means I need 4 1/2 hours of full sunlight to get the battery back to 100%. Does that make sense? Thanks for your patience folks.
MisterSandals
Participation Medalist
You got it!
Can be done with watts too...
56 amps x 24v = 1344w
1344w x .25h = 366wh
charging @ 80w... 366wh/80w = 4.575h
ianganderton
Auckland, NZ
boom. You got it right there!!!
love both seeing (others) and feeling (myself) what light ? come on
