DISCHARGE MYSTERY

[sailalong]

Recently I had installed two Solbian Flex SP100 140Watt solar panels along with two Genasun Charge Controllers. Prior to the installation I had my AGM batteries bench tested with positive results. The problem now is when under power my batteries are rapidly discharging. Is it possible that they are discharging through the solar panels. I am the first to admit that my knowledge about electrical systems is finite so any suggestions/help would be appreciated. I also have a 2000 watt inverter/battery charger on board. While dockside and plugged in the batteries come up to full charge. Thanks

[Captain Bill]

I don't think we have enough information to help. When you say "under Power" do you mean when your engines are running? Given your name can I assume a sailboat and that when your engine is not running the battery does not discharge abnormally? Is your inverter supplying power while you are underway?

[sailalong]

Yes, we are a sailboat and yes when under power we are using engine power. The inverter is used underway for any AC uses ie wall outlets, micro wave, lap top and other small appliances or chargers. Prior to the installation of the solar panels I never experienced this problem of rapid discharge. I also have two battery banks each with two large AGM batteries and each bank has its own battery switch.

[Captain Bill]

How big is your battery bank and how fast is it discharging. It's rather odd that this discharge is occurring only when the engine is running. I would think that anything that discharges only when the engine is running pretty much has to be controlled by the ignition switch. Since the discharge is not happening when the engine is off, what accessories are connected through your ignition switch. Most ignition switch controlled accessories don't normally draw much power so what ever it is should be getting hot. Is it possible that your starter is remaining engaged after the engine starts? That motor is a pretty big draw. Solar panels and controllers are not normally connected through an ignition switch so there us usually no way that the running status of the engine can effect them. Do you have separate start and house batteries? If so, to which bank is the engine alternator connected?

Some inverter/chargers have an ignition interconnect to prevent excessive batter draw down if the engine is not running. If the inverter is powering a large battery drain like a hot water heater only when the ignition is on this could explain a large drain. I don't know why this would not have occurred before the installation of the solar panels but perhaps something got changed in the wiring. A 1500 watt water heater element could suck down batteries pretty fast if a small engine alternator was all that was replenishing the batteries. Remember a small alternator can only put out it's rated power for a short period before they cut back due to heat. A 1500 watt draw on an inverter takes 150 amps from your batteries and your small alternator may only be putting back 30 so you are drawing down the batteries at a net of 120 amp/hrs per hour. This could easily put quite a dent in your battery bank. Most Inverter/chargers give you the ability to dsiable the inverter function so try turning it off next time you are motoring and see if it makes a difference. If your engine is a diesel most of them will stay running with the ignition switch in the off position. You can try running for a while with the switch off and see if the excessive drain continues. If not, you definitely know it's something connected to the ignition switch.

[Bleemus]

Two clues point me to a bad alternator or regulator. You say you run the inverter when the engine is running. So we can deduct that your batteries are charging when the engine isnt running.

You are drawing more than 15 amps on your inverter which is what two 140watt panels will put out in full sun.

Solar panels are working. Alternator is not.

Cover solar panels with a thick blanket. Start engine and run it at 1500 rpm and tell us what a multimeter says your voltage is at battery.

[jamhass]

Use a clamp - on ammeter and figure out where all those electrons are running to.

[Bleemus]

Based on their stating they were an electrical novice I didnt suggest an amp clamp. Most newbies dont have one.

[sailalong]

Thanks for all the responses and I do have a multi-meter. I will try the various suggestions and I think by the process of elimination I should be able to isolate the problem. Stay tuned!!

[DumnMad]

I too am a novice in this stuff but wonder if one bank is fully charged by solar to a higher voltage than the other. When you switch the engine on could there be a back-flow of current from one bank to the other?