36 Volt In Place Of 32V?

[Brian Degulis]

Many years ago we did some work on a 70' steel comercial trawler this boat had only a 32V DC system with very few electrical acessories. The entire system was shot batteries charger etc all bad. What we did was replace the 8V batteries with three 12V 8D batteries and three 12V battery chargers one for each battery. So we created a 36V system to replace the 32V the chargers were always on so I'm not sure how it would work with alternator charging only it might not bring the batteries all the way up? All of the lights and motors seemed to tolerate the aditional voltage with no problem. One of the advantages I see to this is that you would no longer need a seperate 12V system for electronics etc. With the individual chargers you could tap the 12v off the grounded 12V battery. Also you no longer expensive and hard to find 8V batteries and a 32V charger. I did this about 20 years ago and can't speak for the longevity of it the boat left for Shrilanka shortly after we were done. My 61' MY is 32V and I'm facing some of the problems you guys are talking about and I would be real curious as to your thoughts on this aproach.

Brian

[MikeP]

I haven't found any of the 32V stuff to be particularly hard to find. I don't think it would be worth the trouble to try to convert. Hatts came oem with voltage reducers (32-12) for the electronics so there is no advantage to going to 36V for that purpose. The 32v charging system would not charge the 36v batts properly so you'd have to revise that. Also the 36v system would be too much voltage for any retained 32v items.

IMHO there is nothing to be gained by this and a LOT of money to be spent.

[SKYCHENEY]

IF you were going to convert a 32v system to another voltage, 36v would be the cheapest way to go, but it would still not be cheap. At least with 36v (vs 24v or 12v), you would not have to change wire sizes, but you would still have to get all new starters and alternators and chargers. Also, new bulbs and converters and volt gauges.

Why spend that kind of money when you can still buy all of the 32v stuff? It is not as readily available and you will pay a little more, but that price is substancially less than the cost to convert the whole system.

You cannot just throw 3-12v batts in there to replace the 4-8v ones. They will not get charged completely and they will not last. If you do charge them completely, you could have as much as 48v and that will not run a 32v blower for long without burning it up.

[Brian Degulis]

OK First I'm not sugesting the posability of doing this unless your looking at tired batteries and an old charger. To the best of my knowledge the 32V chargers available today are very expensive and even the new ones are out dated and the 8V batteries are more difcult to find and more expensive. I'm also not sugesting changing all the 32V loads I'm sugesting running them on 36V That's about 1.5 percent higher. The starters and larger motors will definetly handle that. Smaller motors and lights I think would but I'm not sure. And the alternators would proubably need to have the regulators turned up or replaced to get a higher output voltage. Like I said we did this to a simple boat and it apeared to work great.

[SKYCHENEY]

A fully charged 32v system is about 34-36volts. A fully charged 36volt system is 40-42v. Thats 20% more voltage. And if your charger periodically de-sulfates by overcharging, you could have as much as 46-48v for a short period of time. This would mean replacing all of the 32v loads with equipment rated for the higher voltage. If you didn't do it right away, you would be doing it incrementally as each piece failed.

I'm not saying that it wouldn't work. But it would be costly. Then I still would not tap 12v off of a 36v bank. You will cause one battery to need more charge than the others and may "cook" the other 2 upon charging. The only way to do this is with a converter or an equalizer. Read Calders chapter on this. He even writes about driving a nail through the case on a 32v system to obtain 12v (which has been done, but he recommends against it just as he does with any other tap of lesser voltage than the whole).

Instead of spending that much money on a complete change, buy some 8v Rolls batteries and a good charger. That should last another 15 years and by then you can reevaluate the situtation.

[Spellbound]

Brian -- check your PM's

[krush]

You will cause one battery to need more charge than the others and may "cook" the other 2 upon charging. The only way to do this is with a converter or an equalizer. Read Calders chapter on this.

who is calders? Are you talking about a book?

[captwoodyb]

Hi Brian, I have a 1972 Hatt, certified for carrying passengers and have owned it for some 20 years. About the same time I bought her I had to replace the 8Volt batteries, total of 8 in two banks of 4. Instead of replacing the large surette batteries I opted for two regular size 12 volt and one 8 volt for each bank or 32volts by two 12's and one eight. I have been using that configuration for 20 years now without problems. .....Capt Woody

[REBrueckner]

36 volts instead of 32 volts is an increase of 12.5%. For comparison, a 12 volt system when being charged to 14 volts (before float) is running almost 17% higher than "normal". At 13 volts charging, the system is about 8% above "normal" . But many loads applied at this time would draw down the voltage and the heaver the load, like a starter motor, the more the voltage drops back to 12 and likely below that. In addition, many circuits are designed for a 3% voltage drop and this would also offset such a source voltage increase to some extent.

In theory, with a higher voltage source, motors would draw less current, but in practice they'll likely spin faster and draw more current than at 32 volts. So wiring would have to be at least as large as original because loads will operate above nominal design power levels and draw a bit more current.

I would think two 12 volt plus an 8 volt battery in series ( for 32 volts) would work if you don't want all 8 volt batteries. Place the pair of 12 volt batteries closest to ground, the 8 volt near the 32 volt end of the string. Pick your 12 volt supply from the battery directly connected to ground. You can also e-mail or telephone a battery manufacturer for information...but the few times I have done that I have NOT gotten "engineering" knowledgeable people.

My GUESS is that everything will work ok, but there could be problems. 32 volt light bulbs that die prematurely could be replaced with 36 volt bulbs. One thing for sure: in a 32 volt system, active components (like motors, starters) operating at 36 volts cannot last longer than the original design. How much faster they die is anybody's guess. If there are any 32 volt HALOGEN bulbs aboard, they will almost certainly die faster as they are quite sensitive to voltage.

If you separately charge a 12 volt battery in a series string, I'm unsure how effectively a 32 volt charger would handle the others. Again, in theory it should be ok, but the 32 volt charger now sees a parallel load at the 12volt battery charger level. Ferroresonant chargers taper down as battery resistance increases due to batteries becoming charged; three stage smart chargers use more sophistictaed regulation and might be "fooled" by the presence of another charging source. Correspondence with a battery charger manufacturer might provide authoratative feedback.

[Brian Degulis]

OK you folks have convinced me this is not a good idea to many problems and un knowns.

Thanks for your input it was all logical thought from people that understand the problem including two replies with first hand experience.

Where else could you possably get this kind of information at the push of button?

I'm going to stay with 32V I may use 2 12V and one 8V to build the banks but I'm still looking into that. I think I will go with one of the Outback charger/inverter combinations. It would be nice to not have to run the generator when I just need a little AC power.

Thanks Again
Brian