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Battery Wiring

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alaska_av8r

Contributing Member
"1986 29 ft Cruisers with twin

"1986 29 ft Cruisers with twin Crusader 270's

After weeks of reading books and researching forums I have determined that the previous owner has the isolater wired incorrectly.

I am planning on rewiring the batteries and trying to design a more efficient system without costing an arm and a leg.

Here are my goals...
1. Simplify operation to one switch
2. Get the most out of the alternators
3. Get rid of the isolator.

From what I have gathered you cannot parallel the alternator outputs, not sure if would gain anything by doing this or not...from what I was told if I paralled them to charge a battery bank, one would see the others voltage and then reduce its own output thereby defeating the purpose.

Does this sound reasonable? If so how do dual alternator battery isolators get around this? With the diodes?

I have also read that it is better to set up the alternator to charge similar batteries (i.e start to start or deep cycle to deep cycle).

The alternators that I have are 8MR Motorola's with built in voltage regulation, they also do not have a separate "Sense" wire. Therefore this has lead me to do away with the isolator due to the voltage drop and no easy way around it.

The system I am planning will have one battery selector (which will determine which start battery will be used to crank either engine). Normally kept in position 1 unless that battery goes bad (minimal switching).

The port engine alternator will charge start battery 1 and thru an ACR charge start battery 2.

The starboard engine alternator will charge the house bank of deep cycles that are wired in parallel.

This keeps battery types to separate alternators and since the alternators are not wired thru switches no chance of open circuiting them.

The battery charger will feed start battery 1 with one lead and thru ACR feed start battery 2. The remaining two leads will go on the house bank.

you can see the diagram here http://www.hellzhoundz.net/crusadernewelect.pdf

Please feel free to make any suggestions keeping in mind I want to try to stay with one battery switch and make the system as versatile as I can in that situation. If it would be of any benefit I would still like to find a way to utilize both alternators to charge the house batts but don't even know if there is a benefit in that."
 
"Are you considering pulling o

"Are you considering pulling out your alternator lead from the harness and routing it to a battery which is not even connected to that engine?

It looks as though you are making things more complicated, not less. Your quest for simplicity is too complex.

If you are insistent on four separate battery banks, you will want an isolator (or two) in the system. There is nothing wrong with isolators, providing you use the right type.

I would eliminate the 1-2-B switch and make them On-Off, one per bank. Run one engine directly from it's bank. I would also leave the alternators connected to their respective banks. I would consider permanently paralleling the two house banks. You can't have that complex a system in a 29' boat to require two house banks.

I don't know where you got your information from, but any time you run a 1-2-B switch in the BOTH position, you are paralleling alternators. NASA may not do it, but trust me, you will be fine. Millions of boats are out there wired that way. I personally do not like that type switch. I prefer a momentary solenoid to temporarily parallel banks, for starting purposes, then let the charging system take over.

If you absolutely won't use isolators, ACRs are useful, you might want to consider incorporating several in the system.

I hope this has been helpful."
 
"Thanks for the response Rick,

"Thanks for the response Rick, my drawing may be misleading but I only have 1 bank which consist of my two deep cycle batteries that are permanently wired in parallel. The other two batteries will remain isolated and are start batteries. So in essence, I have one bank and two single start batteries.

The alternator leads are already wired down to the battery area to an isolator (the isolator is a single alternator, two bank model that they have wired in reverse, two alternator inputs with one output)...

I actually have an ACR in the diagram, that parallels my start batteries while charging.

The reason I am directing my port alternator to my start batteries and my starboard alternator to my house bank deep cycles is in reading from several sources, it cautions about different types of batteries being charged with one alternator. One battery type ends up over-charged while the other ends up under-charged depending on which battery the alternator is sensing.

Since paralleling the alternators isn't a big deal, do I have anything to gain by doing that, I know batteries will only accept so much charge depending on temperature etc, will the second alternator feeding into a common charging system be worthwhile...via a Both position as you mentioned?

thanks once again
every response gets the mind thinking...

tim"
 
"Yes Tim, the drawing is confu

"Yes Tim, the drawing is confusing as you have two charge leads from the charger charging the same battery bank (house).

Isolators do not work backwards. It sounds like he has combiners installed (the opposite of isolators and they can look the same). It is easy to test these. When connected to an ohm meter you will only have continuity in the direction the current is to flow.

I don't know why he would want to use both alternators to charge one source.

Regarding mixing batteries. Yes, what you are saying is correct, but it pertains more to mixing types such as flooded lead and gel or AGM batteries, rather than simply different capacities of flooded lead batteries.

Regarding paralleling alternators, no there is no advantage to it. That's the reason I would remove the combiner he has installed and replace it with an isolator. Use the second leg of the isolator to charge the house bank while under power. I would not be concerned about doing this on both engines, one should be fine. Or, after returning the alternator wiring to it's original configuration, you could move your ACR from it's current location to allow it to combine one of the engine banks and the house bank. That would give you charge voltage regardless of what source you are running.

Good luck
Rick"
 
"Hate to disagree with Richie,

"Hate to disagree with Richie, but the isolator is not required. I have two alternators charging 5 batteries through a simple Perko battery switch; and it works just fine.

A 'low' battery will be filled up by the alternators and the charged batteries until they are all charged. No sweat and, as you stated, Tim, it's nice and simple.

Jeff"
 
isolators drop 1.0/1.5v so you

isolators drop 1.0/1.5v so your batteries never see 14 v which is needed to fully charge batteries
 
"Thanks for the input guys, it

"Thanks for the input guys, it sounds like I am finally heading in the right direction.

Sorry about the battery charger confusing the diagram. I will take it out of the diagram to make it easier to read.

House batteries (3 + 4) are deep cycle and paralleled into one bank. Batteries 1 and 2 are normal high CCA Start batteries and are isolated from each other unless receiving a charge thru the ACR.

So from what I gather there is nothing wrong with:

starboard alternator charging house deep cycle bank (3+4) and that bank only to avoid mixing battery types.

port alternator charging start battery 1 and thru ACR to start battery 2

Under normal operations I should never have to move the Battery Selector switch from position 1 unless that battery dies, and with this wiring I never have to worry about frying an alternator because of a switch position.

I won't be paralleling the alternators since nothing gained, I won't have the voltage drop caused by an isolator....

Rick it is an isolator (it says guest battery isolator mod # 2530 on the side of it) with 3 connections on it, i received a wiring diagram from guest and as best i can tell he wired it backwards. He has the orange leads coming from both alternators going to two posts on the isolator, these leads then continue on to the start solenoid post on starter(same place battery connects) **in my mind he just bypassed the isolator and provided a direct feed to the batteries from the alternator** Now on these same two posts he has a lead from the battery charger. Now all of these are inputs...

On the single remaining lead from the isolator he attached the third input from the battery charger, and there is a wire from this to the house batteries. It appears to me he wired a one alternator input, two battery output battery isolator totally in reverse."
 
"Okay guys I have the finished

"Okay guys I have the finished product based on all the research and input I have received. For me this seems to be the simplest, cheapest most efficient system I can come up with to do the job I want. Maybe the information will be useful to others as well.

Thanks once again for all your help and input, here is the link again.
http://www.hellzhoundz.net/crusadernewelect.pdf"
 
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