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jav wrote:BUT MOST- also have a seperate DC charging circuit dedicated only to making sure the generators starting battery is recharged after you use power from it to start the gennie. This output normally happens automatically as soon as you start the genie. SO- if you use the house bank as the gennie starting battery (which is how you showed it) as soon as you start the gennie, THIS output will attempt to charge the house back.
I believe his Onan is like that as mine is. The genny charges it's own battery thru the battery leads (the fact it does this is not visually obvious unless you read the manual ). Which is why way back when in his initial sketch I said he should disconnect the house from the genny battery.
Hmmm, So disconnect the Genny battery from the house, attach the ebay charger to it and add another 2 batteries just to the house?
Hmmm, sounds like a plan.
79' Carver 28' Mariner
I want another Trojan, preferably a Tri Cabin
So when i wire the 8 amp charger into the panel, what size breaker should I use? 5,15,10, 20 or 30 amp breaker? I think if I remember correctly my current charger is on a 15amp breaker
79' Carver 28' Mariner
I want another Trojan, preferably a Tri Cabin
The AC draw of the charger is very low, probably less then 1 amp. You really don't need to have a fuse or circuit breaker designated for the charger. You can tap an existing circuit for the outlets in your boat and run the charger off of that circuit. It will probably be a 15 amp circuit.
jwrape wrote:Hmmm, So disconnect the Genny battery from the house, attach the ebay charger to it and add another 2 batteries just to the house?
Hmmm, sounds like a plan.
Exactly... that will work for you.
As has been said earlier the bank of batteries may not perform very well due to variance among them.
When/If you reach that stage then you can buy one big battery and enjoy the comfort of a trouble free service!
Michael
Rum is the reason Pirate's have never ruled the world
Done Dreamin'
1987 President 43' Twin Lehman 225SP Turbo
Highfield 310 Ally 15 HP Yamaha 2cycle
1978 F32 Sedan twin 318 Chry SOLD
Safe Cove Marina, Port Charlotte, FL
There is a safety concern with wiring batteries in parrallel. When wired in parrallel, regarless of the charged state of either battery, the voltage will stay the same. If one battery starts to get weak, or worse fails, the other battery will try to "charge" the dieing one. When this happens, it can cause a fire or go boom!
To prevent this, you can install a "fuselink" or fuse block between to the to + leads. The fuse needs to be just slightly bigger than your max load or just larger than your max charging current, what ever is greater. With any luck, when one battery fails, the fuse will go long before the batteries self distruct. If you want a good plan on the right way to put this together, look at the wiring of most electric golf carts. Most are a combination of serial and parrallel wired 6V batteries with fuse links everywhere.
The manual method, and safer method, is to have a multi bank charger for the house battiers and a selector switch. You simply run the first deep cycle down and then flip to the 2nd or 3rd with a switch.
Is this really a concern. The batteries could explode?
79' Carver 28' Mariner
I want another Trojan, preferably a Tri Cabin
I was goggling parallel battery wiring and of course there is a ton of stuff about wiring batteries in a off grid home for inverters.
There was a couple different ways they suggested wiring the batteries for optimum performance.
The first way is the normal way everyone would think, just running positive to negative and then pulling off the top battery.
Then there is wiring them positve to positve and Negative to Negative but taking the positive from the top battery and the negative from the bottom battery to balance the draw off the batteries so that the top battery in the above picture doesn't do most of the work and the bottom battery doesn't do the least work
Then there is the best suggested way and that is to bring all the postives and all the negatives to a common bus and pull directly from the bus. That way all the capacity is used equally. Also charges equally.
From what I can tell, options 2 and 3 are almost the same principal but by far the 3rd option would be ideal.
What do you guys think
79' Carver 28' Mariner
I want another Trojan, preferably a Tri Cabin
jwrape wrote:I just read this on the "Battery Bank" post
......
Is this really a concern. The batteries could explode?
To frame this, the question relates to fires and explosion WITHIN A BANK OF BATTERIES- as opposed to things that happen outside or upstream of the bank.
Getting back into the nitty gritty of bank design- that is an unlikely occurance in a true house bank. It may be more likely if a house bank is made up of starting or dual purpose batteries but I would bet it's still a "very remote" possibility.
I've not heard of a bad bank battery causing an explosion or fire within the bank. I suppose if a battery in a parrallel bank were to fail internally such that the positive and negative posts were shorted ( versus having "some" resistance), then the current available from the other batteries could produce enough heat to start a fire if the parrallel wiring were insufficient to carry the current but, I don't believe this is a common failure mode.
I think it's more common for 1 battery to go bad by getting over charged and losing a cell and then that battery sucks current from the other good ones at some slower rate where the temperature rise in the wiring is negligable.
But here's where the details that seem minor can come into play. Another benefit to using "true deep cycle batteries" in a bank is that, unlike starting batteries that are desinged to release upwards of 500 amps on demand, deep cycle batteries "resist the rapid release of current". This is why they aren't great starting batteries... the current drops off rather quickly under heavy loads. Deep cycles are desinged to deliver "low current" for long periods. Starting batteries are desinged to release large currents for short periods so there is some inherent additional safety in a properly configured house (deep cycyle) bank.
jwrape wrote:Found out that my Onan does not have an altenator. It's starter battery is only charged off the on boar charger.
I understand - no alternator - but when you refer to "on board charger", this can mean two things-
1) The Onan has NO charge circuit at all for the starting battery and the term "on board charger" refers to a seperate external charger running off shore power or the gennies AC output.
or
2) The Onan has an "on board charger" that is NOT alternator based. This is very common and many gennies have "on board or built in chargers " that are "rectifier" and not alternator based.
If condition 1 (which I think is unlikely)- no problem using house bank to crank genie.
If condition 2 (which I think is more plausable)- then using house bank to start gennie may be problematic.
I've been told by the expert Onan guy on the SmokStak Forum that it only has a small internal charge circuit to keep the coil energized like a stator on a motorcycle engine but the starter battery is only charged by the on board charger that is seperate, that runs on 110v- option 1
79' Carver 28' Mariner
I want another Trojan, preferably a Tri Cabin
jav wrote:2) The Onan has an "on board charger" that is NOT alternator based. This is very common and many gennies have "on board or built in chargers " that are "rectifier" and not alternator based.
If condition 2 (which I think is more plausable)- then using house bank to start gennie may be problematic.
This is what my 3.5Kw Onan has.
jwrape do you have a manual for your genny?
If not send me the model no my buddys 78 Trojan has a 6.5Kw Onan with manual and I can check with him.
Michael
Rum is the reason Pirate's have never ruled the world
Done Dreamin'
1987 President 43' Twin Lehman 225SP Turbo
Highfield 310 Ally 15 HP Yamaha 2cycle
1978 F32 Sedan twin 318 Chry SOLD
Safe Cove Marina, Port Charlotte, FL
jwrape wrote:I've been told by the expert Onan guy on the SmokStak Forum that it only has a small internal charge circuit to keep the coil energized like a stator on a motorcycle engine but the starter battery is only charged by the on board charger that is seperate, that runs on 110v- option 1
J,
I hate to rain on your parade and I'll sign off after this as it seems your intent in doing it a certian way so by all means- do what makes sense to you.
The reply you received from Billy at SmokStak did not suggest condition 1.. it suggested condition 2. Here is his verbatim response:
" Your unit does not have an alternator. It has a small charging system built in. But most boats I worked on had an outside charger for the boat. Ran from shore power or generator power. "
His response appears accurate and is consistent with the Onan/Cummins manuals I have- although I don't have the manual for yours specifically. Unless you had another more in depth discussion, it seem your interpreting his response differently than I would and differrently than other on here have advised.
It's your boat and your call so all I can say is- best of luck with whatever you decide.
jav wrote:2) The Onan has an "on board charger" that is NOT alternator based. This is very common and many gennies have "on board or built in chargers " that are "rectifier" and not alternator based.
If condition 2 (which I think is more plausable)- then using house bank to start gennie may be problematic.
This is what my 3.5Kw Onan has.
jwrape do you have a manual for your genny?
If not send me the model no my buddys 78 Trojan has a 6.5Kw Onan with manual and I can check with him.
I do have one but it's not always helpful.
But thanks for the offer.
79' Carver 28' Mariner
I want another Trojan, preferably a Tri Cabin
). Which is why way back when in his initial sketch I said he should disconnect the house from the genny battery.
