how to TEST an onboard battery charger

last year i set up a dual battery system in my boat. with the battery switch and a Guest battery charger. I left the switch on "BOTH" for a month and a half after my last striper trip. this weekend the batteies were dead...

no problem, I figured there may be a slight draw in the boats wiring, so i plugged the onboard charger in and the next day went to check the boat. the batteies were still dead!!

i leaned over and sure enough the little green light on the charger was on....telling me the charger had power!

so I unplugged that charger and I plugged in my sears battery charger. It has a % reading and several other options for charging...its a nice charger... i selected deep cycle and 6 amp charge power and set the one scale on %. the % at the start was about 5%....after 5 hours or so the % was up to 65%, I did this for each battery one at a time...they both didnt seem to want to go past 65%

in the last few years these batteries always went to 100% when used with the sears charger. As well during the last year the onboard charger has never let me down... i plug it in the night before i use the boat and I always had full power the next morning!!

so now i want to see if the onboard charger is working...or if it some type of bad connection in my wiring contacts...or if the batteries are going bad and the charger cant charge them for some reason

how do i check the output of the onboard charger?

on another note....since the sears charger wont charge past 65%, is that telling me the batteries are dead....one is only 18 months old... a big interstate deep cycle I bought at the marine mechanics


thanks

bob

Re: how to TEST an onboard battery charger

First things first:
Is your on-board charger a single output or dual and what is the amp ranting per output? If it is a single output charger it would make sense to set the switch to both so both would charge. However, if the charger is a low output, then charging each battery individually makes sense. As for the batteries going dead, if the switch is set to BOTH the charger should have more than made up for the losses anything running would have drawn. I must assume you have a single output charger and you likely have it connected to the COM terminal on the switch. It could also be connected to either battery and both would charge with the switch in the BOTH position. If it's a dual bank each output should go directly to one of the batteries. Now to testing the charger:

1) Disconnect the POSITIVE lead from both batteries and then check the level of the water in each battery. Add distilled water if necessary.
2) Using a voltmeter, measure the battery voltage and note that reading.
3) Connect the charger leads directly to the battery.
4) Power up the charger
5) Measure the battery voltage after about five minutes.
6) If the charger is working the voltage should be higher than the reading you took in step 2.
7) Repeat this process for the other battery.
8) You can do an open circuit voltage check on each output if you wish but without a load (the battery) the charger voltage reading may be inconclusive.

If there is no change in voltage readings, the charger is not working.
I would advise you to charge the batteries as best you can with the portable charger, or borrow a known good one. Then take both batteries to most any auto store and have them load tested. If they test ok, then we need to look for other issues.

Re: how to TEST an onboard battery charger

I am 95% sure it is this unit:

Guest Onboard Battery Charger Model 2610A Battery Charger 10A 2 Output

I think the + leads go the battery switch( I am at work now and cant see the boat) and the negatives go to the terminals on the battery. which leads me to think it might be a headache to try and hook up the charger to one battery at a time..

the charger is NOT NORMALLY plugged in while the boat sits!

the charger ONLY charges when i plug and extention cord into the outlet on the boat that feeds the charger!!

so while the batteries were slowly going down, the onboard charger was not powered up !

I trust the sears charger...i bought the on board charger so i wouldnt have to climb into the boat and flip the seat to attach the battery charger... i just reach over the gunnel and plug the extention cord in...easy peasy!! i wish i had done that years ago!

bob

Re: how to TEST an onboard battery charger

I just checked and it is a dual battery 10 amp ( 5/5) charger by guest.

upon closer inspection I can clearly see I have a ton of yellow corrosion powder built up on and under the positive terminals from the battery switch on the battery itself..... I have a huge suspicion if i remove the terminals and thoroughly clean everything..ill get a good connection via the wires in the boat through the switch....

the reason the sears charger probably worked is because I connected them with the large alligator clips to the posts!!!

the batteries are maintenance free... I dont think you can open them to add water!

ill check back later


bob

Re: how to TEST an onboard battery charger

You can still open them to add water.

If you don't keep your batteries fully charged...ALWAYS, you are asking for what is happening to you now.

Measure the voltage at the battery with the charger on and tell us what you get.

Re: how to TEST an onboard battery charger

The battery swtich has an OFF position to prevent what is happening. If one of the two batteries is weak/bad, leaving the switch in the BOTH position parallels them and the weaker battery sucks the life out of the good one until they equalize. It also means that anything left on in the boat will be allowed to run until the batteries are dead. Run the charging leads directly to the batteries to eliminate one additional connections point. The negative cable is routed to the battery so why not the positive?. If you are in the habit of leaving the boat sit for a month at a time without charging the batteries it is no wonder they are dead. Plug the charger in and let it run. The charger will go into float mode to keep them topped off. If you don't like doing that, then use a 24 hour "programmable" timer so power shuts off automatically after whatever time you like. You could even set the timer to run the charger for a couple hours each day. Charing must occur immediately after use -- not just before you go out the next time.

Re: how to TEST an onboard battery charger

Silvertip said:

The battery swtich has an OFF position to prevent what is happening. If one of the two batteries is weak/bad, leaving the switch in the BOTH position parallels them and the weaker battery sucks the life out of the good one until they equalize. It also means that anything left on in the boat will be allowed to run until the batteries are dead. Run the charging leads directly to the batteries to eliminate one additional connections point. The negative cable is routed to the battery so why not the positive?. If you are in the habit of leaving the boat sit for a month at a time without charging the batteries it is no wonder they are dead. Plug the charger in and let it run. The charger will go into float mode to keep them topped off. If you don't like doing that, then use a 24 hour "programmable" timer so power shuts off automatically after whatever time you like. You could even set the timer to run the charger for a couple hours each day. Charing must occur immediately after use -- not just before you go out the next time.

Click to expand...

thanks for the tips, I use the boat weekely after the fall and through the winter... and sporatically during the summer. I should turn the switch to off, I know that, but i guess i forgot the last time out in may. the boat is parked 75 feet from electrical power, so i have to run an extension cord to charge the batteries. so there is a little more to it than leaving the wire on the boat all the time. if i pulled the boat into the garage every time i was done it would be easy. the charger is wired according to the instructions that came with it. with the use of the switch it would be a pain to undo everything. especially since you have to unbolt the switch to access all the connections and the battery cable is thick!!

but i will un do the batteries and clean all those connections this weekend. and ill be more dilligent in turning off the switch after use from now on. cant do much about not using the boat every qweekend...life is full of....life, I guess! ha ha

bob

Re: how to TEST an onboard battery charger

I cleaned up all the connections in the battery box.... and greased over them after I tightened everything.. here is a picture

I have a fused battery cable sized line running to an 4500 lb electric winch. thats why I have the extra ground....most everything else was grounded to my fuse panel and the fuse panel was wired to the battery.



bob

Re: how to TEST an onboard battery charger

To answer the first question as a simple test...

With the battery Charger/Maintainer plugged in and operating, The voltage on the batteries should be ABOVE 13 volts.
Make the measurement on the Actual Battery POST! NOT the Battery Clamp or screws or connections, The actual POST that is part of the battery.

When your posts were all crudded up, you likely would have measured >15 volts on the battery clamps, and <10 volts on the Battery Posts, 1/8 of an inch away.

Re: how to TEST an onboard battery charger

I'd assume the reason you're battery switch connection's were green is because the switch is so close to the battery's.
When battery's charge they give off fume's that will corrode anything nearby.

Re: how to TEST an onboard battery charger

grub1grub2 said:

I'd assume the reason you're battery switch connection's were green is because the switch is so close to the battery's.
When battery's charge they give off fume's that will corrode anything nearby.

Click to expand...

? I dont think I ever said the termials were green... i did say i had yellow corrosion on the BATTERY.....I cant see the connections for the battery switch, they are underneath the switch.

I have found that one battery is indeed dead.....i dont know if i drained it or its time was up... the other one seems to charge fine now.

bob