Proper size batteries?

[SEVEN]

I purchased all new 8 volt batteries back in November. I installed them and they worked perfectly until about a month ago. I had my mechanic come over, he is also an electrical contractor for boats, and he tested everything from the starters to the cables to the batteries and charger. The motors will not turn over unless I hit the par switch. After checking everything and indicating there is nothing wrong he said the only thing it could be is that these batteries are deep cycle. He says deep cycle batteries are not starting batteries and they don’t have enough cranking power after they’ve been in for a while to start these big motors. My question is, has anybody else put in deep cycle? Also, if I’m switching over to the smaller golf cart batteries, do you know of a company that makes 8 V that is not deep cycle?

[Boatsb]

I purchased all new 8 volt batteries back in November. I installed them and they worked perfectly until about a month ago. I had my mechanic come over, he is also an electrical contractor for boats, and he tested everything from the starters to the cables to the batteries and charger. The motors will not turn over unless I hit the par switch. After checking everything and indicating there is nothing wrong he said the only thing it could be is that these batteries are deep cycle. He says deep cycle batteries are not starting batteries and they don’t have enough cranking power after they’ve been in for a while to start these big motors. My question is, has anybody else put in deep cycle? Also, if I’m switching over to the smaller golf cart batteries, do you know of a company that makes 8 V that is not deep cycle?

First off they are not big motors. They just have inefficient starters.

Second the wiring must be done right. Bad ground cables are often the problem.

Third they make an 819 for starting its what most 32 volt hats came with.

Fourth there's also rolls who makes a great battery for this use.

Price/quality matters

[carolinacoast]

I use GC's. and dont need to parallel them.. Trojan T875's. I suggest calling DC battery in Miami since they have their own CCA calculations on those batteries. They export to a lot of boats with Detroits. Confirm cable size or charger settings. 6V92's.
Yes....I know that they are not starting batteries, but they work for me. Available anywhere.

[Pascal]

Deep cycle batteries are not ideal but they should crank fine as long as they are big enough.

Back when I had 8V71Ns they cranked fine using 4 8 volt golf cart batteries (Exide E4800 now discontinued) . I would usually get 4 to 5 years out of them.

And someone corrects me if I wrong but I believe the naturals have higher compression than turbos

I would start by checking all connections for corrosion especially the negatives and the battery switches. And of course load test the batteries.

[SEVEN]

All tests have been completed. This is a text message. My Mechanic just sent me.
Deep cycle batteries do not deliver the high current large Diesels need the may work for a Chevy Engine but nothing else.
The do two things ruin battery’s and burn up starters!

Low voltage drives up the current it also as you can see causes slow cranking which causes hard starting.

The high starter current and low voltage destroys Starters.
The starting batteries on a 32 Volt system should not drop below 28 volts these deep cycle batteries are dropping below 14 volts.

As they say they are not made for high current starting!

[Pascal]

Voltage dropping to 14 v is definitely a BIG problem. What kind of batteries are they?

Are all the cables including the jumpers between batteries big enough? They should be 4/0.

As i said I used deep cycle golf cart batteries for over 10 years without issue. Never had to parallel the banks. And I know many others have done the same

[Briankinley2004]

I would load test the batteries. Also, especially with 8 volt, just because you purchased "new" batteries doesn't mean they are new. One of my "new" ones began to boil about a week after I installed it. It was hot to the touch and the others were cool. Good thing I found it. The tag revealed it was 2 years old. Went to exchange it and the guy at NAPA said all on shelf were old so they got a new one from the warehouse. It was the end of June of the year we were in and the tag said July of same year??

[ian w]

I have used golf cart batteries for about 7 years now .They work fine on my 8 71 turbos
If they are using a lot of water there is a problem with the battery charger
They should easily turn over 8 71 engines

[brettportzer]

I purchased all new 8 volt batteries back in November. I installed them and they worked perfectly until about a month ago. I had my mechanic come over, he is also an electrical contractor for boats, and he tested everything from the starters to the cables to the batteries and charger. The motors will not turn over unless I hit the par switch. After checking everything and indicating there is nothing wrong he said the only thing it could be is that these batteries are deep cycle. He says deep cycle batteries are not starting batteries and they don’t have enough cranking power after they’ve been in for a while to start these big motors. My question is, has anybody else put in deep cycle? Also, if I’m switching over to the smaller golf cart batteries, do you know of a company that makes 8 V that is not deep cycle?

What batteries are you using, btw?

[Steve Mannshardt]

Replaced my 32 VDC batteries in 21 with simple 8 VDC wet cells. No issue. Took what I could get from Battery Bill in Sac town. Supply chain. Korean product. They’ve been great so far.