What Brand and Size Battery Charger should I buy?

[rajhnsn]

I just replaced my house bank of (4) six volt flooded batteries on my O'day 35. One week later when I returned to the boat the fridge had thawed and my volt meter was reading 12.7 for both banks (house and start). The Amp meter on the Charge Pro 15 Amp charger was reading about 1 to 2 amps. I shut off the charger and started the motor. The volt meter went to 13.8. Ran the motor for about 10 to 15 minutes, shut it off and went back to shore power. The amp meter on the charger went to close to 15 amps and then leveled off at about 6 amps. I checked the shore power cable for a tight fit. Around 5 hours later the batteries were reading 13.4, the fridge was working normally and the charger was reading 0 amps. I had to leave the boat at that time but I'll bet that the fridge is defrosted again the next time I go down. I think its time for a new Battery Charger. The Charge Pro 15 is probably original to the boat. The boat is on shore power most of the time. I go out for a few days at a time and stay on the hook throughout the summer and usually one long trim down the Chesapeake in the spring and fall. The fridge is probably my biggest load but I have an electric head too. Auto pilot and Raymarine Axiom 9 are being used while sailing and motor sailing. What do you think is a good brand for under $500.00 and how many amps should a new charger be?

 

[Davidasailor26]

12.7 V is not really a dead battery - that’s pretty much where a battery will float in the absence of of charging or loads. If your fridge is not running at that voltage there might be other problems, like voltage drop in the fridge circuit.

There are some chargers that have a Power Supply or California Compliance mode, where they stop giving a float charge and instead just give enough power to offset any loads once the batteries are full. It’s possible yours got switched into that mode.

The rule of thumb is to size your charger at 10% of the bank’s capacity plus your normal loads. For 4x 6V batteries that’s probably about a 30A charger ideally.

 

[Ralph Johnstone]

As @Davidasailor26 summed it up, if your batteries are at 12.7V and the fridge is not running, the fridge and/or its circuit is the problem. 12.7V is about 90% SOC..

 

[jssailem]

You have made an investment in your new battery bank. It is wise too protect that with a charging system that will let you enjoy the longest life of the battery bank. To accomplish this you need to think about the whole battery charge system.

10 minutes of engine charge is not enough to accomplish anything on a battery bank of 4 - 6volt batteries. Unless you have a extra large engine alternator, you will need to run the engine for several hours.

To learn about charge systems, I would encourage you to explore the information at MaineSail's "Marine How To" website.
Installing A Marine Battery Charger- Marine How To.com

I bought the Sterling Ultra 40 Amps. The 30 amp unit would support the battery bank you describe.

 

[Ralph Johnstone]

In addition to @jssailem 's suggestions, consider installing an external alternator regulator for keeping your batteries as fully charged as possible when away from shore power and pulling amps.

 

[rajhnsn]

Thank you all. Good ideas. I've been looking for Mainesail's information on this. I knew it was out there but did not know how to get to it. I'll definitely read this area. I have a 120 Amp Alternator and a Balmar Regulator so that can take care of the system pretty well when I'm off of shore power. I don't know if the Pro Charge 15 Amp has a step charging feature. The Isotherm water cooled fridge has a low battery feature that comes on at a certain point whereas the fridge draws minimal power but I don't think it was able to maintain the temperature for the length of time that it was on that setting. Thanks again.

 

[twodzusfittings]

Have you considered a solar array? I made mine for about $600 including the panels. 200watts total, wired to a dual battery controller sending the power to two batteries.The panels are mounted on a SS 1" frame, all basic hardware bought on line. The only custom part is the bracketry for the uprights attaching them to the stern rail.

 

[MikeHoncho]

Thank you all. Good ideas. I've been looking for Mainesail's information on this. I knew it was out there but did not know how to get to it. I'll definitely read this area. I have a 120 Amp Alternator and a Balmar Regulator so that can take care of the system pretty well when I'm off of shore power. I don't know if the Pro Charge 15 Amp has a step charging feature. The Isotherm water cooled fridge has a low battery feature that comes on at a certain point whereas the fridge draws minimal power but I don't think it was able to maintain the temperature for the length of time that it was on that setting. Thanks again.

Check the water flow for the refer unit. Also check for voltage drop in the refer circuit. I had the Isotherm “smart”blue box on my unit that was so sensitive to voltage changes it would run erratically and I removed it.

 

[LouisMK]

Your 15A charger is way undersized for a 200A battery bank. I have had excellent luck w/ both Pro-Mariner on my previous O’DAY 34 and Sterling on my O’40. The Pro-Mariner is a re-badged Sterling however if you’ll search for the Sterling you’ll likely find it at a better price. Tried to purchase from Maine Sail last year but unfortunately he had left the business. Anyway, have been completely satisfied with both the 30 and 40 amp models. Install is pretty straight forward & should take you about an hour.

Also installed a 375W LG solar panel on Kato dingy davits w/Victron controller- seems to be working fine so far.

 

[Tin Kicker]

Size of charger relates directly to how fast you want the batteries to charge. If you go out for weekends and the boat sits all week, a small charger is just fine.

On a related topic, I wouldn't touch one that is not a newer smart charger. The old style chargers basically provide an amount of amperage that uses the battery as a resistor which can lead to running a battery dry. The old dogs would get down to a minimum current whether the battery needed it or not. For example, the radio/nav stack takes a few milliamps to keep their memories intact and in the aft of my boat are two exhaust fans to keep air constantly moving through the cabin which are about 0.1A each. The boat charger I removed was either off or on at a minimum of 1 amp and I installed a NOCO Genius GENPRO unit. I've had a 10A NOCO unit in my camper van for a year and the van has 200 Ah of AGM.

Smart chargers monitor ambient temp to limit charge rates when cold or undercharging, can limit charge when hot, can desulfate if needed, charge nearly dead batteries, & are able to recognize a full charge so they can reduce the input from full amperage to a trickle to match any parasitic loads. Most can determine what type of battery they are charging, so you can switch the same unit from charging an AGM or lead to a Li-Ion. (Not try to charge both at once.) They are also generally sealed to be waterproof.

 

[MikeHoncho]

My AGM recommends a minimum charging amp which is 20 if I remember so chemistry might have a say in the size regardless of how long the battery will sit on the charger.

 

[Tin Kicker]

My AGM recommends a minimum charging amp which is 20 if I remember so chemistry might have a say in the size regardless of how long the battery will sit on the charger.

My guess is that it is based on battery size, if you have a 100 Ah battery. The one "C" rate is what it takes to charge a battery 100% within one hour, and a 20% charge rate is a typical max. That comes to 20A for a 100 Ah battery.

Slower charging can never hurt, it just can take painfully long sometimes.

 

[Maine Sail]

My guess is that it is based on battery size, if you have a 100 Ah battery. The one "C" rate is what it takes to charge a battery 100% within one hour, and a 20% charge rate is a typical max. That comes to 20A for a 100 Ah battery.

Slower charging can never hurt, it just can take painfully long sometimes.

it should be noted that no lead acid battery can charge to100% in one hour no matter how much current you have. Some li-ion chemistries can charge at 1C but .3C to .4 C is what is optimal for LiFePO4 which is what is used on boats.

Many small chargers will literally burn themselves up trying to charge a large bank.It can also throw off the charge algorithms..

Pro mariner specifically states this in the ProSport manual Course no one reads the manual so we used to replace a slew of them that had cooked themselves. A min of 10% of installed Ah capacity is what should be aimed for in charger sizing.

There is only one small charger I know of that can charge huge banks and not suffer from heat damage and those are the Victron IP65 Series..

Choose your Portable/Maintenance Chargers Carefully!! - Marine How To

 

[heritage]

I'm using a Victron IP65 for charging the AGM starting battery and a Victron IP67 for the lithium batteries. The Victron smartphone app is great. Easy to see what is going on between the chargers and batteries.

 

[Tin Kicker]

it should be noted that no lead acid battery can charge to100% in one hour no matter how much current you have. Some li-ion chemistries can charge at 1C but .3C to .4 C is what is optimal for LiFePO4 which is what is used on boats.
...

I never wrote that any battery should be charged at 100% in one hour, only that this is "1C" because this is the definition for how fast batteries charge. Even in the lithium world, there are very few that can charge at or above 1C and those are generally for specific mission hardware.

...
Many small chargers will literally burn themselves up trying to charge a large bank.It can also throw off the charge algorithms..
...A min of 10% of installed Ah capacity is what should be aimed for in charger sizing.
...

Yes, going to the other end of plausible with an extremely undersized charger can lead to the charger failing. But then manufacturer recommendations can be anywhere from 5-45% Ah capacity, so the 10A charger on my 200 Ah bank is not unreasonable. The other key was that like the original poster, my van and boat batteries are seldom run down or need to quickly come up from deep discharges. Like him, my boat is generally plugged in. I'll agree with you that a going less than 5-10% is too small to recommend.

You have a great website and done a lot of good for the community, so noted your comment about needing to replace smaller chargers. Having decades of investigating fires which included from failed chargers, I can tell you the typical reasons are that the less expensive ones either don't have an internal thermal switch for self protection, or are not designed to balance shedding the heat produced by the coil windings. Below is a photo of an older ProMariner charger which failed and that led to a fire in the wiring. This model had a built in cooling fan and I couldn't prove it conclusively but due to the lack of soot signature suspected that the fan first failed. You can see how the melted insulation from the coil flowed downward, sufficient current reached the cable to one bank (lower right) to burn off the insulation, and fortunately the owner was aboard to catch this while it was lots of smoke with small flames.

While I didn't mention it in my previous post, this is another reason I promote smart chargers which have temperature sensors. The sensor is also used to monitor for charger failures and can shut them down.

Bob
www.HowItBroke.com

 

[Maine Sail]

I never wrote that any battery should be charged at 100% in one hour, only that this is "1C" because this is the definition for how fast batteries charge. Even in the lithium world, there are very few that can charge at or above 1C and those are generally for specific mission hardware.



Yes, going to the other end of plausible with an extremely undersized charger can lead to the charger failing. But then manufacturer recommendations can be anywhere from 5-45% Ah capacity, so the 10A charger on my 200 Ah bank is not unreasonable. The other key was that like the original poster, my van and boat batteries are seldom run down or need to quickly come up from deep discharges. Like him, my boat is generally plugged in. I'll agree with you that a going less than 5-10% is too small to recommend.

You have a great website and done a lot of good for the community, so noted your comment about needing to replace smaller chargers. Having decades of investigating fires which included from failed chargers, I can tell you the typical reasons are that the less expensive ones either don't have an internal thermal switch for self protection, or are not designed to balance shedding the heat produced by the coil windings. Below is a photo of an older ProMariner charger which failed and that led to a fire in the wiring. This model had a built in cooling fan and I couldn't prove it conclusively but due to the lack of soot signature suspected that the fan first failed. You can see how the melted insulation from the coil flowed downward, sufficient current reached the cable to one bank (lower right) to burn off the insulation, and fortunately the owner was aboard to catch this while it was lots of smoke with small flames.

While I didn't mention it in my previous post, this is another reason I promote smart chargers which have temperature sensors. The sensor is also used to monitor for charger failures and can shut them down.

Bob
www.HowItBroke.com

That generation of pro-mariner, and the Sterlings of that generation, had a horrendous reputation for failures. You are correct that it usually started with a fan failure. The ProSport series is a fanless waterproof design. so they need to be sized correctly as they can't shed the heat a dry mount charger with a fan can. The small Victron chargers are an extremely efficient design that develops less heat to begin with.. Still for a large bank that gets deep cycled 10% should be the min goal..

I had seen your site before when doing reasearch for an ABYC committee I am on..It is excellent!

 

[heritage]

I am not understanding why my Victron IP67 cannot operate continuously and safely at its maximum current of 17 amps regardless of the size of the battery bank.
It has a Power Supply mode where the voltage and amperage are settable. There is no warning that the power supply is limited in how long you can run it at max output.