Guest Dual Charger Bleeding between Banks

[foxden]

Sorry for the strange title, but that is what is happening, I have an older Guest Dual on board charger connected to each battery through a Perko Battery Selector switch.

I removed battery two from the boat, and still read 12 volts at its disconnected leads. No charger was plugged in and the switch was set at Battery 1. The batteries are isolated and I shouldn't get a reading unless the switch was at All.

I thought maybe the switch was bad, but I removed the wires and tested and found that was good. I did read connectivity between the two positive leads of the charger(also off) so,determined that was how voltage was leaking from the battery one cables to the battery two.

Ok, question, is the recharger serviceable? Are there rectifiers or something else shot inside? I am correct that the two sides of the charger are independent and I shouldn't read some connectivity between the two sides of the charger?

Hope I made enough sense for so done to help me out.

I know I need one new battery, but do I need a new charger, too.

Thanks.

 

[UncleWillie]

Re: Guest Dual Charger Bleeding between Banks

You may be seeing leakage voltage between the banks.
The typical DVM has a 10 million (Mega) Ohm Impedance.
If the leakage is only a very few Milli Amps (Thousands), You will measure the 12 volts btu the current would be so small as to be insignificant.
It wouldn't light a light bulb and would take thousands of hours to drain the battery.

Place a small 12 volt load (Lamp) on the leads to see if there is any current backing up the voltage.
If the voltage disappears with the lamp in place, You may not have any issue at all. :joyous:
If the bulb lights, that is a different story!

 

[Barnacle_Bill]

Re: Guest Dual Charger Bleeding between Banks

When they first came out with on board chargers the leads themselves were not isolated. The first Guest I had had a common ground for the 2 banks.

 

[wrench 3]

Re: Guest Dual Charger Bleeding between Banks

Question, is it still charging both batteries. Those chargers have automatic charge rates controlled by a power transistor for each bank. So I would go with UncleWillie's suggestion.
BTW replacement parts are not usually available. They just want to sell you a new charger.

 

[foxden]

Re: Guest Dual Charger Bleeding between Banks

It does charge both batteries, but one was bad and seemed to keep the good one from fully charging. With the bad one removed, the good charges to capacity. I'll try the light bulb thing next week and see if I am getting much current.

But I should measure infinite resistance between the two positive leads on the charger when it's unplugged, right?

 

[wrench 3]

Re: Guest Dual Charger Bleeding between Banks

The dual battery chargers have one transformer with a preset maximum output. Lets say it's 10 amps. If one battery is taking 7 amps, then there's only 3 amp left for the other one.
A transistor is not like an on off switch. although it can be used for the same purpose. It may only shut off to 99.9%.(figerativley speaking)

 

[bruceb58]

Re: Guest Dual Charger Bleeding between Banks

But I should measure infinite resistance between the two positive leads on the charger when it's unplugged, right?

No. Any measurement circuitry that connects to the outputs in the charger will be in your measurement so its not a valid reading for what you are trying to do.

 

[UncleWillie]

Re: Guest Dual Charger Bleeding between Banks

No. Any measurement circuitry that connects to the outputs in the charger will be in your measurement so its not a valid reading for what you are trying to do.

+1 ^^^

I would expect the measurement to be in the few hundreds to few thousand Ohm range, but far from an infinite open circuit.
The reading may also be extremely different depending on which lead you choose to place the positive meter lead on. (Diodes!)

 

[bruceb58]

Re: Guest Dual Charger Bleeding between Banks

The reading may also be extremely different depending on which lead you choose to place the positive meter lead on. (Diodes!)

Yep, the meter is probably turning on transistors.

 

[bassman284]

Re: Guest Dual Charger Bleeding between Banks

OK, maybe I'm missing something or just lacking in knowledge, but why would you hook up an onboard charger through the Perko switch? Wouldn't you want the charger leads hooked directly to the batteries?

 

[foxden]

Re: Guest Dual Charger Bleeding between Banks

While it would be ideal to hook the charger to each battery, I am able (because of location) to put the positive leads of the charger's banks on the terminals for battery 1 and 2 on the switch. As long as the switch is not on "both", each battery is connected to a separate bank of the charger.

 

[bruceb58]

Re: Guest Dual Charger Bleeding between Banks

As long as the switch is not on "both", each battery is connected to a separate bank of the charger.

Yes, That is fine.

 

[UncleWillie]

Re: Guest Dual Charger Bleeding between Banks

Sorry for the strange title, but that is what is happening, I have an older Guest Dual on board charger connected to each battery through a Perko Battery Selector switch...

While it would be ideal to hook the charger to each battery, I am able (because of location) to put the positive leads of the charger's banks on the terminals for battery 1 and 2 on the switch. As long as the switch is not on "both", each battery is connected to a separate bank of the charger.

To describe it accurately, the charger is connected to each battery AT the Switch, and not THROUGH the Switch.

 

[foxden]

Re: Guest Dual Charger Bleeding between Banks

Yes, the lead from the positive lead from the charger and from the positive lead from the battery share the same terminal post on the switch, one at post 1 and one at post 2.

I called Guest and they told me as long as I was reading 13.5 volts from each side of the charger with no batteries connected the charger was in float mode and should be good to go. I replaced my one bad battery and a battery cable that was corroding and reconnected the charger. I will see how things go, but I suspect I will be ok.

I will monitor the charging and post back if I have any more issues.

 

[UncleWillie]

Re: Guest Dual Charger Bleeding between Banks

From your opening Post...

...I removed battery two from the boat, and still read 12 volts at its disconnected leads. No charger was plugged in and the switch was set at Battery 1... I did read connectivity between the two positive leads of the charger(Also OFF) so,determined that was how voltage was leaking from the Battery One cables to the Battery Two...

This indicates that the Charger was NOT powered (Plugged In) and the continuity was measured with an OhmMeter and Not a conclusion drawn from a voltage measurement.

I called Guest and they told me as long as I was reading 13.5 volts from each side of the charger with no batteries connected, the charger was in float mode and should be good to go.

This indicates that the voltage is being produced by a charger that is being powered from AC.

The mixed measurements can give rise to a lot of confusion.
However, it would appear safe to assume that the charger is functioning as designed.
Let us know how it goes. :joyous:

 

[foxden]

Re: Guest Dual Charger Bleeding between Banks

Thanks to all of you that have advised me. You really helped me troubleshoot the battery, cables, fuses and charger. The charger is working fine, just warm not hot like before. Also, both batteries are cool to the touch and charged to capacity. The unit is floating and with the new battery cable it starts in a heartbeat from either battery.

If only fishing went so smoothly - incidentally my flats boat is named. Chaos.