T-Pain Is On A Boat: Re: [Electric Boats] battery charging question...

Tuesday, August 20, 2013

Re: [Electric Boats] battery charging question...

Yes, let's hope there OK!
This can be very bad for flooded batts. I just went through this myself on a pair of 140 AH floodeds.
Last year I checked the levels on a regular basis (monthly) and I only topped up in the spring and then in the fall.
This spring I put them on the boat charged and topped up. They have been running great all summer and based on last years maintenance, I neglected to check them.
Well they lost a lot more this year and were way down! They had been performing quite well and showed no signs of losing charge. Since topping them off I have had to cycle them and give them a good "stir" with a bad boy charger. A bad boy is basically an auto transformer and bridge rectifier! You can vary the voltage output and when connected to a battery this also varies the current. It runs directly off the mains with no isolation, hence the "bad boy" designation. This allowed me to really put some current into them, about 30 amps at 30 volts (24 volt system)!
They seem fine now but I know I've taken some life out of them.
My house batteris are AGMs and now I find myself really wanting Lithium for the boat. Just for the maintenance factor and how forgiving they are due to the BMS that you need to have.

mattelderca

From: oak <oak_box@yahoo.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Tuesday, August 20, 2013 12:05:22 AM
Subject: Re: [Electric Boats] battery charging question...

BINGO!

I checked on the batteries tonight, afer leaving them on the charger overnight. The voltage was up, but died as soon as I unplugged the charger.

I checked the water level as you suggested. Though the batteries were relatively new, they were bone dry. I topped them off, and they are now (hopefully) *really* charging now. Will check on them again tomorrow...

From: matt elder <mattelderca@yahoo.ca>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Monday, August 19, 2013 11:40 AM
Subject: Re: [Electric Boats] battery charging question...

What is the electrolyte level in the batteries? If they are extremely low you can get readings like this.

mattelderca

From: oak <oak_box@yahoo.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Monday, August 19, 2013 12:25:23 PM
Subject: [Electric Boats] battery charging question...

Curious issue....

I went out to the boat Friday evening. Checked the battery bank voltage for the 48V Torqeedo - the display read 56V (fully charged, maybe a tad high). Note that the charger was still plugged in. I left the Torqeedo "on", but unplugged, cast off, and motored out using the GAS engine.

When I checked a few minutes later, the motor indicated an error: Dead batteries.

Back at the dock, the battery voltage for the batteries read almost zero. Very strange. To go from what I thought was fully charged to completely dead without running the motor? I could understand a short - but that would generally also give lots of smoke... I went ahead and unplugged the charger from the battery bank and went home for the night.

The bank is made up of 4 x 12V deep cycle lead/acid marine batteries. They are relatively new (9 months old?). Not used much. The charger is a Soneil 48V, 2A charger from Thunderstruck.

Since I suspect the charger, and hope the batteries are still good, I bought 4 cheap 12V chargers locally, and took them out the next day.

By now, the battery voltage on all 4 batteries "floated up / recovered" to 9V. This was borderline too low for a trickle charger to work - they tend to read that voltage and shut down, rather than try to charge. I had also brought along an "old school" charger (probably a transformer and diode inside) that I put on each of the batteries for about 15 min to bring it up enough that the 4 trickle chargers would work....

Once I had all 4 trickle chargers going, I was able to turn the Torqeedo on, and run the Torqeedo (at VERY LOW POWER) for a minute or two, just to ensure that the motor and wiring was good. All seems to be ok.

SOOOOO>>>>>

Is it possible to have a battery bank that is essentially DEAD, but still reads enough voltage (at no load) to trick the charger into thinking it's fully charged??

How does one get a "smart charger" to fully charge a battery?

We've had a couple of weeks of temps over 100 degrees (which would be VERY hot inside the locker in the boat). Would this likely be the problem?

I'm still tempted to build a batch of "old school" chargers that just dump a regulated voltage at low current... But I haven't found a good schematic for anything that I can easily put together to put out up to 2 amps.