batteries for 8.2L Detroit diesel

[Jim Manning]

I have a 36 Cape Dory powerboat with 8.2L Detroit diesels.Does anyone know what size batteries it requires? Thanks.
Jim



NH10d@aol.com

[Walt Bilofsky]

I have a 36 Cape Dory powerboat with 8.2L Detroit diesels.Does anyone know what size batteries it requires? Thanks.

Jim -

Not clear what you mean by size - whether you're talking about physical measurements, ampere-hours or cranking amps.

My CD 30 powerboat has a glassed-in battery box with space for five type 27 batteries. Type 27 refers to a physical size. You can find the sizes listed in any large marine catalog, such as West Marine, and measure your battery box. Or look for the type number on the existing battery.

The other "size" requirements are cranking amps - which is an engine spec you can get from the manufacturer - and ampere-hours, which depends on how you use your boat - whether you stay aboard for days at a time disconnected from shorepower.

Originally, my boat came with four deep cycle batteries - two in parallel for each engine - and one space for a spare. So there were two separate banks of batteries, each of which was responsible for starting one engine, and also could be used as a house bank for refrigeration, lights, etc. (There's also a crossover relay, so once one engine is going it can be used to start the other one.)

When it came time to replace batteries, I decided to create a larger house bank, so I put four type 27s in parallel on the port engine, giving about 400 Ah of capacity. I bought a type 27 automobile starting battery, and have that alone on the starboard engine.

The advantage is that when I use 200 Ah of power at anchor (which takes a couple of days on the hook), the house bank is only halfway down, which is lots better than (a) running two 100 Ah batteries until they're near dead, which is real bad for them, and then (b) wondering if the other bank will have enough juice left to start the engines if I run the house off of them for a while.

The only downside is that when one of the four batteries goes bad, it drags down the other three, so you have to replace all of them at once. But by that time they're usually near the end of their life.

Now, the reason the boat originally had two type 27s on each side is that these diesels need more cranking amps than one deep cycle marine battery can deliver reliably. I called Volvo-Penta and they gave me the battery requirements for the engine - I think it was 650 CCA. You might call Detroit Diesel and get the requirements for your engine. It'll either be in Cold Cranking Amps (the current that the battery can deliver for 30 seconds at 0 degrees) or MCA - Marine Cranking Amps, which is the same thing at 32 degrees. The MCA rating will be higher than CCA for any given battery.

Anyway, one type 27 deep cycle battery won't deliver the requirements for the engine. Neither will most automotive batteries, but I located one high-current battery that met the spec, and it's worked just fine.

Some people say that automotive batteries won't stand up to marine use because of the vibration. I got advice to the contrary, and the auto battery has worked just fine. The other reason not to use auto batteries is that they have thinner plates that can't stand up to the repeated deep discharge and recharge in marine (or RV) use. But I never use that battery for anything except starting the engine, so that's not a problem. In fact, I just put in a new three-stage battery charger, and am not even connecting the starting battery up to it - chargers can wear a battery down prematurely if they're not real intelligent about charging different banks differently.

Hope some of this blather answers your question.

- Walt Bilofsky



bilofsky@toolworks.com

[Chris Reinke]

Walt - I recently met a fellow CD enthusiast at the Cape Hatteras NC Coast Guard station (the events leading up to our meeting is another long story). He suggested the use of 6 volt golf cart betteries for house batteries. The golf cart batteries are placed in series, as opposed to a parrellel configuration which is standard for 12 volt systems. By connecting them in series they generate the required 12 volts. The cart batteries are VERY deep cycle. The cost of purchasing two 6 volt cart batteries is comprable to that of a single 12 volt marine deep cycle. However, the two 6 cart batteries will provide a substantially greater Ah rating.

I have a 36 Cape Dory powerboat with 8.2L Detroit diesels.Does anyone know what size batteries it requires? Thanks.

Jim -

Not clear what you mean by size - whether you're talking about physical measurements, ampere-hour or cranking amps.

My CD 30 powerboat has a glassed-in battery box with space for five type 27 batteries. Type 27 refers to a physical size. You can find the sizes listed in any large marine catalog, such as West Marine, and measure your battery box. Or look for the type number on the existing battery.

The other "size" requirements are cranking amps - which is an engine spec you can get from the manufacturer - and ampere-hours, which depends on how you use your boat - whether you stay aboard for days at a time disconnected from shorepower.

Originally, my boat came with four deep cycle batteries - two in parallel for each engine - and one space for a spare. So there were two separate banks of batteries, each of which was responsible for starting one engine, and also could be used as a house bank for refrigeration, lights, etc. (There's also a crossover relay, so once one engine is going it can be used to start the other one.)

When it came time to replace batteries, I decided to create a larger house bank, so I put four type 27s in parallel on the port engine, giving about 400 Ah of capacity. I bought a type 27 automobile starting battery, and have that alone on the starboard engine.

The advantage is that when I use 200 Ah of power at anchor (which takes a couple of days on the hook), the house bank is only halfway down, which is lots better than (a) running two 100 Ah batteries until they're near dead, which is real bad for them, and then (b) wondering if the other bank will have enough juice left to start the engines if I run the house off of them for a while.

The only downside is that when one of the four batteries goes bad, it drags down the other three, so you have to replace all of them at once. But by that time they're usually near the end of their life.

Now, the reason the boat originally had two type 27s on each side is that these diesels need more cranking amps than one deep cycle marine battery can deliver reliably. I called Volvo-Penta and they gave me the battery requirements for the engine - I think it was 650 CCA. You might call Detroit Diesel and get the requirements for your engine. It'll either be in Cold Cranking Amps (the current that the battery can deliver for 30 seconds at 0 degrees) or MCA - Marine Cranking Amps, which is the same thing at 32 degrees. The MCA rating will be higher than CCA for any given battery.

Anyway, one type 27 deep cycle battery won't deliver the requirements for the engine. Neither will most automotive batteries, but I located one high-current battery that met the spec, and it's worked just fine.

Some people say that automotive batteries won't stand up to marine use because of the vibration. I got advice to the contrary, and the auto battery has worked just fine. The other reason not to use auto batteries is that they have thinner plates that can't stand up to the repeated deep discharge and recharge in marine (or RV) use. But I never use that battery for anything except starting the engine, so that's not a problem. In fact, I just put in a new three-stage battery charger, and am not even connecting the starting battery up to it - chargers can wear a battery down prematurely if they're not real intelligent about charging different banks differently.

Hope some of this blather answers your question.

- Walt Bilofsky

Chris.reinke@transamerica.com

[Walt Bilofsky]

Walt - I recently met a fellow CD enthusiast at the Cape Hatteras NC Coast Guard station (the events leading up to our meeting is another long story). He suggested the use of 6 volt golf cart betteries for house batteries. The golf cart batteries are placed in series, as opposed to a parrellel configuration which is standard for 12 volt systems. By connecting them in series they generate the required 12 volts. The cart batteries are VERY deep cycle. The cost of purchasing two 6 volt cart batteries is comprable to that of a single 12 volt marine deep cycle. However, the two 6 cart batteries will provide a substantially greater Ah rating.

Chris -

Yes, 6 volt golf cart batteries are very useful. The nice thing about putting them in series is it avoids the problem with one weak battery dragging down the others with which it is paralleled. The trap about comparing the ampere hour ratings is that you're looking at amperes at 6 volts - in other words, paralleling two 105 Ah 12 volt batteries gets you 210 Ah at 12v; putting in series two 225 Ah 6 volt golf cart batteries of about the same size gets you 225 Ah at 12v. So the ampere hour advantage isn't really that great - it's more the durability of both the batteries and the configuration.

Unfortunately for the golf cart approach, my CD 30 flybridge boat has a lovely glassed-in battery compartment which is exactly sized for five type 27 batteries. The size GC2H golf cart battery in the West Marine catalog is shorter, wider and taller than a type 27, by 3/4" or more in each dimension. So it just won't fit. And unfortunately, the batteries are staggered in the box which makes reconfiguring it even harder.

I don't know if Jim's CD 36 has the same battery box - the 30, 33 and 36 are quite similar boats - but if so, we're both pretty well committed to type 27s unless we want to start ripping out fiberglass.

- Walt



bilofsky@toolworks.com