Charger recommendation for daysailer/weekender

kappykaplan · May 16, 2011

The batteries provide house power. The chargers charge the batteries.

Don S/V ILLusion · May 16, 2011

Actually, most chargers serve both purposes when powered by shore power of 1. charging the batteries and 2. also providing house power by virtue of proving the capacity to run onboard electronics while simultaneously charging the battery bank.

The charger should be sized according to your battery capacity. As batteries are theoretically supposed to be charged at 20% of their rated capacity, it's pretty simple to figure out your charger rating needs. 20% of 2 x Gr27 batteries with 90 amp capacity each or 180 amps total = a 36 amp charger. Change the battery rating to fit your specific batteries.

This isn't to say you need a 36 amp charger; just that anything over that rating is wasteful. Anything smaller will suffice albeit the time to reach full charge obviously is longer.

Snotter · May 16, 2011

Stay away from fero-resonant chargers. You want something with a computer built in.

Stephen K · May 16, 2011

The DC loads you will be drawing are going to be pretty small and the Xantrex 10 amp will be fine. In addition, it is a very reliable three stage "smart" charger that will treat your batteries well. For a good overview of battery systems and tutorials you should check out the following website: www.amplepower.com/primer/

Joe · May 16, 2011

I have a truepower 10amp for my 2 x group 27's. It's perfect for the job, takes about 3-4 hours to charge bank back up. A 20 amp will lower that time some, but may not be worth the extra cost for you.

berner73 · May 16, 2011

We went with an Iota (w/IQ4) and are pleased with the decision. Just another option to help confuse you...

http://www.solar-electric.com/bach1.html

FourPoints · May 16, 2011

I rarely plug into shore power. My primary source of charging for my 2 group 24 batteries is a 12w solar panel, plus the 30min time the engine is running each way when exiting / entering the harbor. Since I don't manage to go out often during the week, it has all week to recharge normally. As long as it's sunny during the week, my batteries will be fully recharged by Friday from whatever I used on the previous weekend, it helps that I've converted all the lights on the boat except the steaming light and the light in the head to LEDs.

Not exactly a solution for cruising, but it works well for me.

FourPoints · May 16, 2011

Mad Dog said:
So is the house load just a parallel load to the batteries? Sounds like a simple electrical resistance equation - the charger provides amps based on the resistance it sees from the house and the batteries. Or can you priority select, so the house load gets priority and the batteries get whatever's "left over"?

simple resistance equation, there is no way to prioritize charging without disconnecting the battery from the house draw

Capt. Kermie · May 16, 2011

Do any of these chargers impact polarity? I used an automotive smart charger on my batteries and as soon as I placed it anywhere near my fluxgate compass the compass went awry and was off reading. I had to get the charger completely off and away from the boat to remove the magnetic field it created. Was it just that type of charger or do they all emit a magnetic field?

JohnShannon · May 16, 2011

Charger is plugged in AC, battery and DC loads are both on the output of the charger in parallel.

In the event you have a 10A charger when the battery is discharged 10A will be coming out of the charger. If you have DC loads ON (say 2A) then 8A will charge the battery and 2A will go to the load. If you have huge DC load (say 11A) then all the charger current goes to the load and the battery discharges at 1A.

Once the battery is charged (voltage rises) then charger current output decreases as the output voltage regulation takes over from output current regulation.

As far as compasses go (fluxgate or otherwise) DC currents make magnetic fields. The field can be made smaller by making the current loop smaller. This is done by twisting the positive and negative wires together so that the loop area between the two wires is small. Also the charger may have a bunch of iron in it which will also affect a compass.

Joe · May 17, 2011

Mad Dog said:
Joe - do you run your house power while you're charging? I'm wondering how much that extends the charge time (obviously depends on what you're running...)

Yes.... I leave the charger on all the time, as long as shore power is hooked up, of course. It's maintenance free... a computer chip controls everything. I have no idea how much longer it extends the charge time... can't be much because it only runs the interior lights and radio when at the dock. The other stuff.. TV for instance ... is 110 AC shore power.

Joe Diver · May 17, 2011

I have 2 group 27's, marine deep cycles, matched with 210 aH in the bank total. I bought a Guest charger that connects to each battery. It's a nice multi stage charger, all the electronics sealed inside. I haven't hard wired it in to the AC system yet, but will do so soon, so right now it's plugged into an AC outlet. At sea the DC system runs the lights, radio, cabin fans. I don't have a TV, just use my 17" MacBool Pro. I'm considering a small inverter to recharge the MBP if needed, but it get's 8+ hours on battery...and I'm a weekender so usually only 1 overnight.

As far as recharge time, I don't know. I have enough in the bank to get me through the day or weekend, so when I get back to the dock and hook into shore power it may be a week before I get back to the boat. (next weekend) Recharge time isn't really a factor for me.

flynfol · May 20, 2011

I also give a thumbs up to the Iota IQ4 chargers. I have been using them (one converted, one onboard IQ4) for years without any issues. Bear in mind they are not water resistant/waterproof.