How many batteries do you Have?

[jrpla]

HiMy boat is a beneteau 32, with basic equipment plus a Norcold SCQT-4407 icebox refrigerator system. My motor have an 75amp alternatorI have 1 motor group 27 battery and 2 trojan T-105 as my house bank.My question is, do you use more batteries or 2 is fine for the house bank moving a refrigerator?My concern is because I have seen the need to start the engine 1 hour in the morning and night to charge batteries and will like to see if sailors with 30 to 33 foot boat installed more batteries to avoid this.Thanks

 

[BobW]

The price of cold beer!

Your T-105s, with a nominal capacity of 200 amp/hours, will accept about 25 amps of charge when they are less than 90%. (Charging for flooded batteries is calculated at capacity/8).This means that more than 1/2 of your alternator capacity is being wasted - in addition to the down-side of running your engine with a light load - diesels don't like that very much.If you add another pair of T-105s, you should be able to cut your engine use for charging in half, because you have excess alternator capacity available.As an alternative, have you considered adding solar/wind charging capability? Higher up-front cost, but cheaper to operate than your engine. One advantage of these is that they will let you leave your boat for a few days and still keep your beer cold. Cheers,Bobs/v X SAIL R 8

 

[Shippy]

4 T105s

My 356 has 4 T105s for house and two group 27s for starting. We can stay at anchor for about 2 days without running the motor to recharge...that is with reefer, some lights, stereo, etc. I'd add the second set of T105s. I'm thinking about adding one of the portable solar chargers to help.

 

[Stu Jackson]

We have 3 -- 130 ah wet cells

and a separate start bank. You should do an energy budget, because it doesn't matter how many batteries you have, but rather how you use your boat. Wanna stay out a long time w/out engine charging, or do you hop from marina to marina?See the West Marine Advisors for an energy budget calc form: http://www.westmarine.com/pdf/Elecbugt.pdf Their catalogs and any good electrical reference book or website link, like Don Casey at BoatUS.com will have the electrical loads for each item.

 

[Andy]

Turn off the fridge

You don't have to run the fridge non-stop! Keep some bottled water in the freezer. Run the fridge whenever you run the motor, and a little more if you need, but keep the lid on the fridge as much as possible. Hopefully the water bottles in the freezer will store some cooling capacity. (And freeze all that you can prior to putting it in the fridge. Keep as seperate ice chest handy for frequent drinks so you are not opening the deep freeze all the time.

 

[Steve Dion]

Add a block of ice for an extended cruise.

I would suggest that you consider adding a block of ice for an extended outing. This will help minimize your power consumption regarding your refrigeration and help keep everything cooler. You can then turn UP the temp in the box to also conserve energy.

 

[partick]

more power

I've got the same fridge.... I've got 6 golf cart batteries (6v wired to 12) and we suppliment them with 2 60w solar panels. I've lived on the hook for up to 2 weeks straight running the fridge 24/7 plus anchor and interior lights, fans, cd player, ect wthout having to start the engine once.

 

[Derek Rowell]

BobW: Capacity/8?

BobW, I don't understand what you are saying about charging rate. Charging rate is determined by the alternator/regulator. For example, I have a 110 amp alternator and a Balmar smart regulator and I regularly see 90 amps into my house bank (4 T105s) - that's 45 amps/pair - during the bulk charging phase. Where does the capacity/8 come from?

 

[camaraderie]

25% rule

General rule is that flooded cells can accept a charge during bulk stage equivilent to about 25% of rated a/h capacity. Thus a 200A/H bank can be bulk charged at 50 amps. Thi explains how Derek gets 45 amps into a pair or 90 ampos into four T105's. Assuming you follow the 50% discharge principle you will need to put 100 amps back into the 200a/h bank. You can charge for a little over 1 hour with the 75 amp alternator and this will get you to around 80% capacity in about 1 hour or so. From there you go to acceptance rates and finally to float rates which can take several more hours so it is a good idea when on the hook to size your battery bank for maximum daily loads that let you cycle between 50 and 80% charged. Example: Dereks capacity of 400A/H...lets him run down to 200A/H remaining and put back 125 A/H or so in just about an hour+ with his alternator. Nice if you don't like running the engine too much and use around 100A/H a day on the hook. Does that clear it up? BTW...this only applies to flooded. AGM's can accept virtually unlimited amps during bulk stage so it is the size of the alternator which is the limiting factor in bulk charging with those. As a practical matter it is generally not a good idea to try to mate anything larger than 120Amps on a typical small marine diesel...so all things must be considered when setting up your energy plan.

 

[Leviosa]

5 gels

we have 4- 8D Gels on our house bank at 225 AH each and a starting battery Gel 31 at 97Ahfridge runs off the 12volt and with fans and kids, tv stereo ect......we upped from our 6-6volt golf carts to this....not too worried about running low on juice anymore.

 

[BobW]

It's a 'can' vs. 'should' situation, Derek.....

A battery 'can' take a HUGE amount of amperage, especially if it is deeply discharged. On another thread I posted an account from my 'battery boy' days of charging a large set of batteries (total of 360 gallons of electrolyte) with 800 amps at 48vdc. We didn't do that for long, even though the capacity of the bank was 3300 amp/hours and we were within the 25% window, because we could see them gassing and feel the heat rising.What current a battery 'should' take while charging is dependent on a lot of factors, and alternator capacity is not one of them. If you hooked up a second alternator, enabling you to pump 200 amps to your bank, would that be better? It is also a mistake to assume that just because an amp-meter in line with the alternator output reads a certain figure - say 90 amps - that all 90 of those amps are being stored in the battery. So if you're intent on pumping current into your batteries, you should at least consider the pros and cons of fast charging, and decide on the safest, most efficient rate.Excessive current during charging causes several problems, which must be either dealt with or at least kept in mind:1. Overheating - Batteries always heat up during the charging process, and that is mostly wasted amps. The faster you try to charge your batteries, the more amps you will waste generating heat. Does your regulator have a temperature sensor attached to EACH bank? 2. Gassing - except during equalizing or top-off - is also a waste of amps. Hydrogen gas is explosive, and many boats lack an isolated battery space, so it is critical to be aware of when/if your batteries are gassing.3. Stress on the battery - every charge/discharge cycle eats into the total lifetime of the battery. Charging rate effects battery life, just as the rate/depth of the discharge does.4. Stress on the wiring/connections - you're pumping up to 110 amps out of your alternator; what size wire are you running? Is it 1 AWG or larger? All the way to both battery banks? How good are the connections? Now, having delivered my lecture let me say that nothing in what I just wrote is intended to criticize you or tell you how fast you should or shouldn't charge your batteries - I'm only pointing out the factors involved, and that based on these, 'Capacity/8' is a generally accepted 'rule-of-thumb'.Cheers,Bobs/v X SAIL R 8

 

[Derek Rowell]

I'll settle for 25%

Bob,May I respectfully disagree with you (we can still be friends ). As camaraderie says, the accepted max current during the bulk charging phase (constant current) is 25% of the bank capacity. From the Balmar website FAQ section (see the link below)"How much amperage is safe for my system?""Forget the rumor that an oversized alternator will destroy your batteries ... the truth is that the acceptance rate of your batteries will dictate how much amperage the alternator will provide. While we recommend that you try to size your alternator to represent 25% to 40% of your overall battery capacity, an oversized alternator will not pose a danger to your batteries and, in most cases, will provide a much longer alternator life, as the alternator is required to work at a much lower percentage of its capacity."Gassing will not take place until the charger voltage exceeds the out-gassing voltage. In a multistage charger the bulk (constant current) phase is held until the terminal voltage rises to about 14.4 - 14.5v (which is generally below the out-gassing voltage), and then it switches to the constant voltage (absorbtion) phase to add the remaining 20% or so of the charge.

 

[Bill Roosa]

It is all about voltage

The voltage regulator does not regulate amperage, it regulates voltage. The internal resistance of the battery determines how many amps get pushed into it and that depends on how much they are discharged. A discharged battery has low resistance and a charged one high. So you would have to tinker with the regulator voltage to adjust the amperage for each discharge state. Not much fun to have to monitor the voltage minute by minute and that is why most manufactures don't allow you to adjust the voltage in a "while operating" fashion.With that said, the regulator does a pretty good job of "keeping the voltage up" so you don't have to worry. But if you have a 100 amp alternator and can only consume 50 you have a lot of excess capacity you didn't need to buy and the batteries will not charge as fast as you would think because they are not drawing 100 amps. Your alternator will last a long time however.The battery-alternator-loads arrangement is a system and needs to be designed as a system. You really can't get around this.

 

[Derek Rowell]

Not true for smart regulators

Actually Bill, modern external "smart" multi-stage regulators control the current into the battery (within limits). This bulk phase, as I said above, replaces the first approx. 80% of the charge - during this stage the current is controlled electronically and the terminal voltage is allowed to rise from its discharged state. When the battery voltage reaches a pre-set value (around 14.5v) the regulator switches to a constant voltage mode (absorbtion phase) and the current then slowly decreases as the remaining 20% charge is added. When the current falls below a certain value many chargers/regulators enter a "float mode" where the output voltage is reduced to 13.6 v. (the no-load terminal voltage of a fully charged battery.Many regulators also use electronic timers to limit the time the charging program is allowed to stay in the bulk/absorbtion phases.

 

[BobW]

Voltage and current are functions of each other...

and in a system like this, you control the current by varying the voltage. There isn't any realistic way I can think of to directly affect the current being sent to a load (the battery, in this case) without changing the voltage in the part of the circuit that contains the load. The power equation:P = I x EP = WattsI = Current in ampsE = VoltsSince you're actually sending POWER to the battery, the only way to send fewer amps is to lower the voltage. So Derek and Bill, you are both right - you are just looking at the equation from either end. Gassing occurs at ALL stages of the charging process, not just at the end. Some 'experts' claim that gassing is actually BOILING of the water in the battery, but this is patently false: go boil some water on your stove.... did you get separate atoms of HYDROGEN and OXYGEN??? Hopefully not, especially if you have a gas stove. ;DGassing is a chemical reaction that occurs when excess current is forced into a battery, which is why it is mainly associated with the tail end of charging, when the voltage is kept high for a short period even though the battery is using very little current for charging. Incidentally, gassing occurs even in 'sealed' batteries, AGMs and gel cells. These batteries typically use a catalyst to recombine the hydrogen and oxygen, so as not to lose water in the electrolyte. For flooded batteries you can buy 'Hydrocaps' which do the same thing and will cut water loss drastically.Excess current is also turned into heat in the battery, which is why 'smart' alternators/regulators always have temperature sensing (at least as an option). If you have a large 'smart' alternator/regulator but don't have temperature sensing hooked up to your batteries, you are taking a serious risk.So you might ask 'why doesn't a 'dumb' alternator have these problems'? Dumb alternators run on a fixed voltage - about 14 volts - which isn't enough to create the problems like gassing and overheating. It also isn't enough to charge your batteries fully to the point of gassing, either, so it's a compromise.Derek, none of what I am writing is saying you shouldn't charge your batteries at 25% or any other rate. I am merely attempting to point out that the faster you charge your batteries, the more stress you put on your system, and that there are some dangers involved, particularly from gassing and overheating.Do you have the battery temperature sensors installed on your smart regulator? If not, I think you're missing a critical piece of the system.Cheers,Bobs/v X SAIL R 8

 

[Tom]

More Batteries maybe a small Generator

A small generator or solar panel might do the trick. I have three batteries with one as a fully charged backup ,one starting and one house. I'd like to have two or three house batteries but finding a place to put them is a problem. I bought a solar panel but haven't installed it yet. It's a 110 watt. Several people at my old marina bout small generators. The small generators are cheaper than solar panels and work when you want them to work. This is to avoid running their diesels long periods under light loads. One decided that he wanted air conditioning and bought a generator large enough to run is AC.  My refrigerator uses a lot of amps and doesn't seem to work that well. I plan to install some ductwork to pull cooler air from the bilge and exhaust the warmer air and maybe this will improve the refrigerators efficency. The PO installed it in the lazerette which had little ventilation and gets warm from the engine. It's surprising that it works at all.

 

[Terry Cox]

Our boat came with two 8D wet cell...

house bank batteries rated at 240 amps each, a group 24 starter battery and a 8kw Onan Genset. Although we have increased the onboard electronics (GPS chart plotter, DVD player, diesel furnace, etc.) since taking ownership five years ago we still manage our amp hour consumption to around 48 hours before recharging.We prefer spending our mooring time on the hook or buoy and after a couple of days the house bank will draw down to around 12 volts. At that point I run the genset for two hours to heat water for washing and cleaning, and filling up the house bank with amp hours. So far this routine has worked for our PNW cruising needs. Terry

 

[Rapport]

Five 27 Group Batteries 110 Ah Flooded type

I am in total agreement with all replies. If you wish to keep beer cold, icebox refrigerator system usually require 60 Ah/day. Using the 50% rule for discharge four 27 batteries (440 Ah Battery bank discounted 10 %) you would have a margin to allow a full weekend before charging. Battery five is used only as a back up starting battery. This works for weekends with some engine time to charge batteries, using 60 Amp alternators and the 25% rule or less, or about four hours per three days (bulk stage) charge). (35 Degree Beer) Ice consumption is about 15# per day. With a boat on a mooring for daily use, 100 # block ice per week (40 Degree beer), Occasional use 25 # ice cubes on cans (32 degree beer) per 36 hours, given Chicago summer weather. The 440 Ah Battery bank also allows for some use (30 minutes) to run 1K Freedom inverter/charger for water heater, microwave, or toaster ( draw down of 60 ah)Boat size 30' S-2 9.2A 13 Hp. Yamnar 2GM Due to battery size group 27 was use vs. T105 (golf cart)Due to how the boat is used (life cycle cost) flooded vs AGM or Gel.