Got Questions? Ask Them Here.
- Thread starter Maine Sail
- Start date
I think so. I have two house banks of 2 batteries each on a 1 both 2 switch, and separate bank of 1 for the engine. My emergency parallel adds the house to the engine and has bailed me out a couple of times.
so in order to have the EP one must have a 3rd bat bank (start bat) and use it like a jump start when needed
Not unless you use it as a charge directing switch..
With a dead bank your best option is to simply switch to the good bank and not to combine them, before starting the motor..
When you combine a bad battery with a good one all it does is make the good battery work harder trying to both start the motor and to charge the bad battery. It is kind of like saying I can easily run a 100 yard dash and you are then asked to give someone a piggy back for the 100 yards. Think you'll perform the same...?
What if the dead bank has suffered an internal short, this happened just two days ago to member Capta on his generator starting battery. Your bad bank could now be a 10V battery as opposed to a 12V battery. Ouch!!
This is NOT a good time to be using BOTH as the battery voltages will never equalize and the shorted bank will continue to heat up and suck the good bank dead too..
Best practice with a 1/2/BOTH is to simply switch entirely to the good bank until you have a charge source on-line.
The BOTH portion was really intended for charge directing but is most often misunderstood because boat builders used to supply very small batteries and grossly undersize the wiring. With two batteries the boat started better so the myth that you need to use BOTH to start got a foot hold. If you need to use BOTH to start a motor there is something DRASTICALLY wrong with the batteries, system or wiring.
this is what i have been thinking ...i have a 3 bat setup in parallel about 290 amps (switch position #1) for the house and a single bat for the start bank (switch position #2) about 85 amps..... not sure i will ever need more than this....i guess time will tell
Maine Sail, I'm confused. As I said, I have two house banks on a 1/2/both, normally on both. The engine battery is on its own on/off switch. I have a third switch to parallel the house to the engine battery, normally off.Not unless you use it as a charge directing switch..
With a dead bank your best option is to simply switch to the good bank and not to combine them, before starting the motor..
When you combine a bad battery with a good one all it does is make the good battery work harder trying to both start the motor and to charge the bad battery. It is kind of like saying I can easily run a 100 yard dash and you are then asked to give someone a piggy back for the 100 yards. Think you'll perform the same...?
What if the dead bank has suffered an internal short, this happened just two days ago to member Capta on his generator starting battery. Your bad bank could now be a 10V battery as opposed to a 12V battery. Ouch!!
This is NOT a good time to be using BOTH as the battery voltages will never equalize and the shorted bank will continue to heat up and suck the good bank dead too..
Best practice with a 1/2/BOTH is to simply switch entirely to the good bank until you have a charge source on-line.
The BOTH portion was really intended for charge directing but is most often misunderstood because boat builders used to supply very small batteries and grossly undersize the wiring. With two batteries the boat started better so the myth that you need to use BOTH to start got a foot hold. If you need to use BOTH to start a motor there is something DRASTICALLY wrong with the batteries, system or wiring.
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You are correct they are both the same (parallel thread, not tapered.)
Let me clarify my poor wording. I meant that sea cocks and thru hulls are a different thread..... THAN normal plumbing. (Same for "tailpipes" [sic Forespar] (straight and 90 barbed hose adapters) made for sea cocks. But caution - Forespar also makes a few tapered thread hose adapters (for use in connecting to strainers and whatnot that might have NPT threads.
Ken
Kappy,
Any reason you have two separate house banks? It's generally better to have a single larger house bank than two smaller ones so the depth of discharge is reduced and your batteries last longer.
Any reason you have two separate house banks? It's generally better to have a single larger house bank than two smaller ones so the depth of discharge is reduced and your batteries last longer.
Sorry for the confusion. I took Woody's question to be about using the "BOTH" position if you only have a 1/2/BOTH switch. If all you have is a 1/2/BOTH, the BOTH would be your "Emergency Parallel"...
If you have a system like yours I would make sure the emergency switch is wired to the load sideof each battery switch. This allows you to isolate either bank and start or run house loads of either bank while isolating the other bank....
IStream, I'm sure the forward house bank was installed for the anchor windlass. I keep the house switch in the both position to give me a "virtual" larger house bank of 4 batteries. Plus, it's the way the boat was set up when I purchased it in 2008.
My house bank has two Trojan 6v T-105s in series and I was wondering if a charge balancer was necessary to ensure both batteries are brought to the correct and same level of charge. Some suggest the battery connected to the charge source is overcharged while the second battery is undercharged. Does anyone rotate their series batteries, or is periodic equalization the best answer?
See the data sheet at this link.
http://www.okwelectronics.com/iqs/dbmatchid.10840/sfa.view/battery_balancers_search_page.html
See the data sheet at this link.
http://www.okwelectronics.com/iqs/dbmatchid.10840/sfa.view/battery_balancers_search_page.html
Wired properly it isn't an issue. With only 2 batteries in series you cannot wire it incorrectly. The positive is on one battery and the negative is on the other - therefore you are drawing or charging evenly through the bank.
If you had 4 or more batteries in series/parallel it could be wired wrong, with batteries at one end of the bank getting more use than those farthest away.
If you had 4 or more batteries in series/parallel it could be wired wrong, with batteries at one end of the bank getting more use than those farthest away.
Not sure if I understand the situation but, I have 6 12 volt batteries in one house bank. My charge sources are positive at one end of the bank and negative at the other end of the bank; instead of using a pos and neg on one battery at one end of the bank.
I have multiple sources so I have pos at both ends and neg at the other end of the coresponding source.
All specific gravity readings are the same on all 6 cells of all 6 batteries.
I have multiple sources so I have pos at both ends and neg at the other end of the coresponding source.
All specific gravity readings are the same on all 6 cells of all 6 batteries.
that is what Nigel Calder recommends for this application...... hook up + at one end of the bank and - at the other end of the bank
The question is of series batteries remaining in SOC balance. If properly charged and equalized, both at proper voltages, and the batteries actually get "full" this is a non issue. If chronically under charged, or series wired at a differing SOC, they can become imbalanced. This is reall no different than the six 2V cells in a 12V battery getting out of balance.
When I commission 6V batteries they are first wired in parallel and charged to 7.75V. I then let them sit in parallel for a few more days before installing as a series pack.. You can achieve a similar result by charging to 14.7V - 14.8V in series and allowing current to taper to approx 0.5% of the 20 hour capacity...
The problems with series balance and lead acid is due to wiring batts at different SOC's and then chronically under charging them....