I have a 1995 Oceanis 440 with a house battery bank of 4, 6V batteries that are only charged when plugged into shore power. I also have 4, 6V starting batteries that are charged by the 100 Amp engine alternator. I want to have the engine alternator charge the house bank as well, but suspect the alternator is under-powered and would be in danger of overheating. Does anyone know what my options are?
House battery charging
- Thread starter JDREHER
- Start date
Four 6V batteries for starting is a ton of misplaced lead. I call this "dead lead" meaning you are lugging around almost 300 pounds of batteries that never even see a discharge of 0.5% of capacity..
Rx- Combine house bank and start bank into one contiguous bank and keep a single Group 31 battery for starting. Then redirect the alternator to directly charge the house bank properly fused of course within 7" of the battery.
You can then add an Echo Charger, Duo Charger or an ACR between the house & start banks. Without knowing what your alt is it is impossible o say if it will overheat... I can say however that if this is a factory alt it will be woefully inadequate for charging such a large bank...
We really need a lot more info on your use, wiring configuration etc..
Rx- Combine house bank and start bank into one contiguous bank and keep a single Group 31 battery for starting. Then redirect the alternator to directly charge the house bank properly fused of course within 7" of the battery.
You can then add an Echo Charger, Duo Charger or an ACR between the house & start banks. Without knowing what your alt is it is impossible o say if it will overheat... I can say however that if this is a factory alt it will be woefully inadequate for charging such a large bank...
We really need a lot more info on your use, wiring configuration etc..
I agree and why would need 4-6 volt batteries for starting and agree one good 12 volt for starting and solar would do great for charging your 4-6 volt batteries,I have 1 -12 volt for
starting my yanmar 3YM30 and for starting my Gen and 4-6 volt house bank with solar for most of the charging of the house bank and start battery.
Nick
starting my yanmar 3YM30 and for starting my Gen and 4-6 volt house bank with solar for most of the charging of the house bank and start battery.
Nick
Gunni,
You are correct. My "starting batteries" also run my instruments, autopilot, radar, etc...
You are correct. My "starting batteries" also run my instruments, autopilot, radar, etc...
Well, then the good news is you have an immense Amp-hour capacity available! A single standard size battery dedicated to engine start would free the rest up for the House. In fact I am pretty sure that was your OEM install. You just need to find a way to keep all batteries at a high state of charge. Maine Sail is the man on that puzzle.
It all depends on the use and needs. It seems that the PO concentrated all the navigation functions around the bank used to start the engine. Perhaps he realized he could not adequately charge such a large array of batteries with the existing alternator and elected just to segregate a smaller bank to handle the important navigation functions . Is there or was there a generator aboard the boat that could have been used to charge the house bank when underway? It does not make sense to me that someone would not provide mobile charge capabilities to the bank that runs the refrigerator. You might need to conduct an electrical survey to determine your needs and to size the battery banks and charging systems appropriately. Maine Sail has a wealth of knowledge and information for battery systems and I'm sure if you provide all the information on what is there now and what are your needs as far as using the boat that he could give you some valuable recommendations.
There wasn't ever a generator aboard. I am interested in going cruising in the Great Lakes. I just completed the Race to Mackinac and brought along a 2KW generator for the house bank. Problem was whenever I started the generator the initial draw on the generator was to much and it would go into an overload state and shut down. I then had to plug it into a 10Amp battery charger and run the generator for extended periods of time to get the batteries up enough that the generator would handle the initial draw. Then the batteries would charge at 50 Amps or so. Very cumbersome to anticipate how often to run the genny. I am thinking that a battery charger that allows 50 Amps through it might work.
I have owned motor homes for 20 plus years and they have all used 100 amp chargers with no problems. We currently have three 200# 12volt batteries which get down to around 10 volt and they take about 45 minutes to come back to a 90% charge state. Being an electronics tech. for the last 45plus years I prefer the use of an amp meter in addition to the volt meter. My amp meter shows a 100 amp charge for the first 5 minutes then it starts dropping off. The belt upgrade is a great option, make sure and keep an additional belt on board.
The belt upgrade is to change it from the older style V belt to the newer style serpentine which gives more surface area to grab onto and therefore reducing the amount of slip and in turn less wear.
Craig,
I am not in any way trying to single you out here but you make an excellent case to showcase how and why lead acid batteries get murdered.
Depth of Discharge:
No lead acid battery used as a house bank on a boat should ever dip below 12.1V, even when under your average house load. The ONLY TIME it is allowed to dip below 12.1V is under high discharge, short duration loads, such as motor starting, windlass use, bow thruster use or inverter use. After using these devices the rebound voltage should quickly rise back to well above 12.1V, after the load is turned off..
Discharging 10V is well below 0% battery capacity and the end result is battery homicide. At the 20 hour discharge rate (5A for a 100Ah batnk or 30A for a 600Ah bank) a battery should cross the 50% DOD threshold at approx 12.1V +/- give or take age & health.
On boats our banks are large compared to the average load, thus the average discharge load is usually on the order of just 15-30% of the 20 hour discharge rate. In order to help compensate for the low average draw against the large bank we up the discharge cut off to 12.2V under average house loads to prevent discharging much more than 50% of the battery capacity. For optimal cycling life battery manufacturer don't want to see more than a 50% discharge per cycle.
Charge Rate & Speed of Charge:
Three 200 pound batteries is likely three 8D's or even larger batteries. If you actually do have 600 pounds of batteries you are looking at somewhere around 700-900 Ah's of capacity, or more. Simple math shows us that even if the charger could put out 100A for 45 minutes this is only 75Ah's returned to a 700Ah battery bank which was already at less than 0% SOC. Regardless of your lead acid bank size it is pretty much impossible to attain 90% SOC in an hour, even with a charge rate of .4C (40% of Ah capacity) or more when starting from 0% SOC.
Even when starting from 50% DOD with healthy AGM batteries it still takes well in excess of an hour to hit 90% SOC even with a massive charge rate of .4C (40A for a 100Ah or 240A for a 600Ah Bank). Your 100A charge rate on a 400Ah bank is would be just a .25C charge rate or 25% of Ah capacity. On a 600Ah bank a 100A charger is just .17C or just 17% of Ah capacity.. If the bank is really 600 pounds and upwards of 900Ah your charge rate could be as low at .1C or just about 10% of Ah capacity.
I won't even go into Coulombic efficiency as related to charge rate but this also throws a wrench into usable capacity from XX hours of charging time.
Monitoring Batteries:
An ammeter is only telling you the amperage draw now. Due to Peukert, load and variable loads it is extremely difficult to predict SOC by ammeter.. An Ah counter tells you cumulative Ah capacity removed and tries to account for Peukert, temp, Coulombic efficiency etc. but they require careful use in order to remain as accurate as they can be.. A voltmeter tells you terminal voltage, which should not dip below 12.2V in order to maintain healthy batteries. A volt meter can also tell you rough SOC if the batteries are allowed to rest, no loads no charging, for 24 hours or more at 77F.
In an RV it is simple to call AAA or drive to a battery shop so dires situations occur less frequently in regards to battery abuse. When out cruising a Sea Tow call or failure of a bank can result in thousands of dollars of expenses..
If this is from 0% SOC your batteries are simply beyond useful life.. Even if you were charging a bank that large from 50% SOC this tells me the bank is also toast. A 100A charge rate on a 600 pound bank is a small charge rate and bulk should last well in excess of an hour or more before current begins decline. Charge current can't decline until voltage is held steady this stage is called CV/constant voltage or absorption. The only other way it can decline is if the charger has overheat circuitry which reduces output or the battery temp has risen to a point where the temp sensor reduces charger voltage. Only sulfated batteries in poor health will come up to absorption voltage that fast, especially if they have been discharge to 10V or less than 0%.
If what you are using is an Ah counter, also called a Coulomb counter or "Battery Monitor", the proper use & understanding of how they work is absolutely critical.
Keeping Your Battery Monitor More Accurate (ARTICLE LINK)