10, 20, OR 30 Amp Charger? What Do You Recommend?

Don S/V ILLusion · Jun 26, 2011

He is correct. The only advantage a larger charger would serve, other than the obvious, is that most have an equalizer function. As you describe your use being mostly at the dock and charging, equalizing the batteries becomes more important for increasing battery life as batteries do best when being used and not being constantly charged.

flynfol · Jun 26, 2011

Just an option........but look into Iota chargers with IQ4. I have used them for an offgrid cabin, boat, benchtop power supply, and battery backup sump pump........very pleased with their operation.

MaranaF · Jun 26, 2011

Hi Joe

In my experience an under rated charger is a false economy. Here follows my reasoning...

Firstly, received wisdom says the charger should be able to supply a constant charge at 10% of the banks capacity, so about 40A for you. I am reading between the lines a bit here but I think that battery bank is proportionally large for your boat size. (I run 220AH for the house batteries and another 110AH for engine start on my 50ft ketch) so I don't think your placing a huge drain on them, simply making sure you have enough reserve to run everything for extended stays away from shore power. This is great but when you do switch on the charger how flat are your batteries? Let's say they are down 40%, that's four hours for your charger to run at 100% capacity in a perfect world but as the battery heats up during the charge the cycle is extended.

Basically your charger is placed under a huge load for extended periods of time, it will get hot, it will temperature cycle components and over a relatively short period of time it will fail.

Cooling fans (I hate them) are common in modern compact chargers and always fail if they are permanently on. The mean time between failures, the moving parts, the clogging with dust and general lack of interest we show them means they will invariably be the first thing to fail on your charger.

Me? I would buy a big, heavy, 40AH charger with a big passive heat sink. Unfortunately I don't think anyone makes one any more so I have a Victron Energy one and have had no problems with it.

Hope that helps

Stephen

kloudie1 · Jun 26, 2011

Joe, I have half your bank size and have the Xantrex 20 ampere because when I get to shore power when cruising, I want the bank at 100% before I leave..

Andy1237 · Jun 26, 2011

Joe, go big or go home! I just replied to a post about batteries, chargers, and refrigerators. The cold plate compressor takes 10 amps at start-up so when you are in the slip and the frig kicks on, it will take all your charger can give. This will probably over heat the charger. I think that may be why my 30 amp charger is inadequate.

John Nantz · Jun 27, 2011

What about adding solar panels?

If you're on the boat a couple panels would help to counteract the usage so the charger wouldn't have to work so long when you returned.

Last winter a garage with a couple antique cars in it near us burned down. Cause: a battery charger.

Picture: Couple Kyocera 130s. Could go with smaller or just one for starters. I'm using a Blue Sky controller.

Maine Sail · Jun 27, 2011

Andy1237 said:
Joe, go big or go home! I just replied to a post about batteries, chargers, and refrigerators. The cold plate compressor takes 10 amps at start-up so when you are in the slip and the frig kicks on, it will take all your charger can give. This will probably over heat the charger. I think that may be why my 30 amp charger is inadequate.

Andy,

A charger will be mostly unaffected by a 10A inrush current. Most all of that very short inrush will come from the battery not the charger. Most good quality marine chargers are built to run at full rated output for long periods of time. A fridge will not draw an inrush starting current for more than a few seconds at best.

I own a portable Guest 6A charger that has been used to charge banks up to 900Ah with zero issues. It has run at full output for more than four days straight before, as it should be able to, without any issues. I use this charger when working on boats on the hard as it is much easier than connecting up a shore-power cord. Most of these boats draw more than 6A just powering the interior lights so I can see. This charger is now almost ten years old and nearly every time it runs it is at or darn near the full rated output of 6A..

A good quality 10A charger should have zero issues charging a 450Ah bank dockside..

Bill Roosa · Jun 27, 2011

designing an electrical SYSTEM

Pulling soap box from under my desk
You CANNOT design an electrical system by choosing parts from a cataloge or going with what others do. Your situation is different.
You must balance production, loads, and storage to get a system that works long term and does not run into problems down the road.
More storage is better, more production is better and fewer loads is better. The absolute best way to cut cost is to cut the loads to the max extent possible. There is also the concept of "use as you produce" that can save lots as you do not suffer the inefficiencies of storing and retrieving power from the batteries. Running the electric winch or windlass while the engine is running is more efficient than using batteries and recharging later as an example.

I have a spread sheet that lets you calculate loads and play with storage and production to see how things interact if you would like a copy. william-roosa@us.army.mil

Shoving soap box back under desk

What loads do you have turned on while you are away during the week?
Any other electrical production means other than the alternator? How much do you motor while sailing? And how big is the alternator (max amp wise)?

Also, and I think this is just a typo, you said you have 4 golf cart batteries wired in series. Clearly they are not 12 volt as that would be 48 volts and things would start popping when you turn them on. The size is also a multiple of the 6 volt Trojans that a lot of us use but said you wired them in series you would get 24 volts. Most of the electronics can handle 9-32 volts and the electrical motors don’t really care (just run faster), the lights would pop when you turned them on however. Since you didn’t report any such issues I assume you meant 4 six volt batteries wired in series-parallel for 12 volts, or you have 2 banks of 2 batts each wired in series for 12 volts. The reason I make the comment is there are some boats out there with 24 volt systems.
Also, if you have a 12 volt system then you only have 210 AH at your disposal. Series does nothing for AH it just raises the voltage, for parallel connections or separate banks you add the totals.

jtm · Jun 27, 2011

Interesting posts....and Ii wonder about the limits of the boat's panel AC fuses. I installed a Promariner 12 for 2 batteries - M27 house and M24 cranking. I got the 12A model (vs the Promariner 20) because my panel fuse for the 120v AC outlets that I plug the promariner into has a 15Amp fuse capacity and I didn't want to to have the chargers ' draw throw my panel fuse. Am I right in having stayed to 12amp charger ????

Karl13259 · Jun 27, 2011

Joe,
Sounds like we have a similar house bank set-up. 4 Golf Car batteries: 2 each in series and then the 2 sets in parallel. I also get 440 A-H this way.
I think the answer to your question is largely dependent on the way you use your boat. For your day cruising, even with minimal motoring (ie. alternator use), you could expect to replenish the A-H use easily overnight at the marina. On the other hand, if you want to go out for 3 days on the hook, you will be looking to resupply upwards of 300 A-H which could take as long as a day and a half. Could be a problem (or more accurately, inconvenience) if you were planning some extended cruising. Lastly, what about the situation where you are cruising (or on the hook) for really long time frame (think Bahamas) and need to recharge via a portable generator (arguably, the most cost effective way to generate electricity on the boat, at least without using the engine). Having it power a 10A charger means that you need to run the generator for 10 hrs every day. So do you think your needs might change in the future? What about the positive impact on resale value by installing a larger charger? Just some additional thoughts to consider. Best of luck.
Karl Mielenhausen
Commodore, Catalina 320 Association

kloudie1 · Jun 27, 2011

jtmccue, Is ok, but a 12 ampere charger is 12 amperes output capacity at 12 volts.. the AC draw for that charger is 2-4 amperes ..at 120 Volts AC..
Basic electrics: 12 V *12 Amps = 144 Watts
so to figure the AC draw, 144 watts/120 V = 1.2 amperes.. then ya have a BUNCH of inefficiencies that take the actual draw up to around 2-4 amperes.. so your 15 amp breaker is fine.. you could go to much bigger charger if you have a reason to..

Anchorsaweigh · Jun 27, 2011

Joe,

Dig a little at Xantrex and you will find that they will take your unit in trade for a remanufactured one at a fraction of the price of a new one. It took about half and hour and being handed off to several poeple, but in the end I got a remanufactured TruCharge 20 for $125.00 plus exchange and shipping for a total of $145.00. Not too shabby.

Cheers,

Bob

Karl13259 · Jun 27, 2011

AC Draw

jtmccue said:
Interesting posts....and Ii wonder about the limits of the boat's panel AC fuses. I installed a Promariner 12 for 2 batteries - M27 house and M24 cranking. I got the 12A model (vs the Promariner 20) because my panel fuse for the 120v AC outlets that I plug the promariner into has a 15Amp fuse capacity and I didn't want to to have the chargers ' draw throw my panel fuse. Am I right in having stayed to 12amp charger ????

No, you are confusing AC draw with DC output. Even with the typical efficiencies of 80-85%, a 12 DC A charger should not draw more than 2 A of AC current.
On the other hand, if you upsize your charger, make sure the DC wiring from the charger to the batteries can handle the increased load.

Bill1565 · Jun 27, 2011

Maine Sail said:
Andy,
A good quality 10A charger should have zero issues charging a 450Ah bank dockside..

I'm with Maine. Your current use pattern of weekending and leaving the boat plugged in all week should not require anything more than your current 10 amp unit.

My use pattern is different, house bank 450 AH. I anchor out for days at a time, recharge with a Honda 2000 gas generator. I pulled my 30 amp charger and replaced with a 50 amp charger/ inverter to cut down on the Honda run time.

Bill Roosa · Jun 27, 2011

Without knowing what Joe M leaves running on the boat while he is away for the week you cannot tell if a 10 amp charger is big enough or not.
For instance, let’s say he leaves the reefer on and it draws 8 amps at a 50% duty cycle (it is hot out and he has an air cooled condenser). That is 4 amps effective as seen by the system. That leaves 6 amps left over to charge the batteries.
5 days * 24 hours/day * 6 amps = 720 AH in a perfect world with no losses
Solved he has no problem and his batteries will be charged no matter how badly they are drained over the weekend.
If he runs the reefer and freezer and 3 fans to keep the place cool and they draw 9 amps effective (making up stuff for examples here) that leave 1 amp to charge the batteries
5 days * 24 hours/day * 1 amp = 120 AH in a perfect world with no losses.
So if Joe uses more than 120 AH during the weekend he is not going to be charging up the batts fully and will eventually drain (over several weeks) the banks.
So until we know the “how he uses the boat” we can’t say one way or the other. Given it is a 34’ I’d think it is probably more toward the first example then the second but you don’t know till you know.

So Joe, what do you leave on during the week? Bilge pump for sure. Does the prop shaft gland leak much?

Ron20324 · Jun 27, 2011

Joe Mullee said:
There's a lot of people on this forum that know a lot more about batteries and chargers than me so I'm looking for and suggestions or comments.

If you have a West Catalog to look at, they suggest a charger that is rated at 10 percent of the battery-bank's ah rating, plus the load(s). Page 387 for the battery charger advisory.

Stu Jackson · Jun 27, 2011

Ron's right, and you can find the same material right online:

http://www.westmarine.com/webapp/wc...d=11151&catalogId=10001&page=Battery-Charging

JVB · Jun 27, 2011

You said "My house bank is now 440 AH powered by four golf cart batteries wired in series." Really ? In series four batteries would give you 24 or 48 volts depending on whether they are 6 volt or 12 volt batteries.

More likely you have four batteries wired in parallel i.e. all the + terminals tied together and all the "-" terminals tied together. Then the bank gives you the same voltage as the individual batteries.

Did you have a problem with the charger not keeping up with your electricity usage, i.e. not getting the battery bank back to full charge before each week-end ? It seems to me that only if the charger (before the fan failed) wasn't keeping up do you need a bigger charger.

Anchor Down · Jun 27, 2011

It'll Get There: Just Give it Time

Joe, sorry you have to read everyone trying to solve problems for you that don't exist and descriptions of their set-ups and their charging regimens that don't apply to you.

And I'm also sorry that you have to deal with several people who are taking you to task for not using precise language when describing your battery bank, by pretending to not have enough common sense to understand that you have arguably the most common house bank system on a yacht your size. As if that minor point has anything to do with your question, anyway.

Now,
If the boat sits at the dock most of the week, whether between daysails or weekend trips, then you're giving the 10a charger plenty of time to re-charge your house bank. No need to go all Tim-the-Toolman-Taylor on it.

A 10a charger, charging a 400 amp-hour bank, is not bad for the batteries. You're fine. Take a clue that the Xantrex guy didn't try to up-sell you.

Fair Winds,
Jeff

10, 20, OR 30 Amp Charger? What Do You Recommend?

.

.

.

.

.

.

.

Attachments

.

.

.

.

.

.

.

.

.

.

.

.

.