battery question

85 silverton with twin 270 crusaders. currently the boat has 2 marine deep cycle batteries only with a 2 bank charger. i would like to seperate the engines from the house power. can i run just regular batteries for starting the engines and 2 deep cycles for the house? i would just like to avoid using the same batteries for everything.

You needn't worry if the batteries are all wet cell. Mixing wet cell and gel cell or gel cell and AGM is not recommended. So if they are all AGM or all gel or all wet cell, you're good.
Deep cycle vs start battery no big deal.

I think you are on the right path.

As noted above, don't mix the 'chemistry' if at all possible; makes things easier and cheaper in the long run. The easiest way to make use of what you have would be to get the new batteries and then install ACR's - automatic charging relays. they will automatically connect the house bats to the alternators.

If you are fluent with 12 VDC circuits, you could use a couple slave solenoids to do the same thing with the charger, too. A lot will depend upon how much you consume from the house bats and the recharge time available & the charger's capacity.

So, I run "mixed chemistry" batteries, but I don't put them directly in parallel. What is most important is that you don't overcharge a gell cell. Keep the max charging voltage below 14.0. Wet cells are far more forgiving. I also don't like long term paralleling batteries. If one battery develops a weak or shorted cell, it will drain from the good battery. That is my biggest beef with the Off-1-2-ON, in addition to the fact that most installs let you blow your alternator with a simple twist of the wrist.
With smart battery management, I don't see a problem getting one chemistry for the deep cycle and another for starting.

There are a couple of ways to do this now.

One traditional way, they way it is on my boat, is to use an isolator. This allows me to have a house battery bank and a separate engine battery bank but charge them from the same source. Likewise, there are chargers are multi-battery and thus isolated.

There are also automatic switch systems now that do not incur the slight voltage drop from the diodes in the traiditional isolators.

Others have commented about not mixing types. You want to assure that you have an appropiate charging curve for whatever type of battery you are charging.

Also, another made a good comment about not paralleling batteries for the long term. By the way, having my isolator setup avoids needing the 1/2/both switch. Instead, I have a momentary parallel relay.

Bruce Clarkson

Correct! Best if you do not try to use a single Deep Cycle for a cranking bank. These are not designed for this type of load...... not unless you have multiples in same bank.

Ditto the unlike batteries in the same bank, and will go so far as to suggest that for best results, these should be "like" in age, type, group #, previous number of cycles (if this were to apply) and even brand for the purists... of which I am! This can and will affect the over-all condition and health of a battery bank.


Trying to separate your house side from a Stbd engine, for example, can complicate your system.
Isolators are old school technology by today's standards, and they offer a voltage drop.
Consider an ACR by Bluesea, and you'll have a much better system, IMO.

Why not use an MBSS (main battery selector switch) of your choice, and make your two Stbd banks selectable?
Stbd may have a cranking battery on # 1, and your Deep Cycle House Bank may be on # 2, for example.
Switch accordingly!
Bluesea also offers some very good Combining and ACR systems for what you initially wanted to achieve.

Port engine need only have a good single cranking battery... most commonly on # 1.... # 2 is not used.
(the # 2 on port MBSS can be used for combining a source from Stbd bank)

Myself, I have a large bank of 6 volt D/C for my Stbd engine, and I do crank this engine on them.
No issues to date with either house loads, and/or cranking on this large bank.

My port engine has an over-sized cranking battery that the generator shares with it.


I also have a "combining" solenoid switch, that with the flick of a momentary helm switch, joins Port bank with Stbd bank!
It does this right at the "Common" terminals of my side-by-side MBSS's.
It's very clean and simple!
The PO had installed this, and I like having it there for an emergency low Stbd bank scenario.
Flick switch... I have instant Port side power to Stbd.
Knock on wood, haven't had to use it.

On board power management can get confusing real quick. Fortunately modern science has gotten it pretty well sorted out.
What it boils down to is safety. You do not want to be stranded away from the dock unable to start your engine due to a dead battery. Unless you are in a very small boat, always near shore and within cell phone range of Bubba's 24 hour Marine Towing, you will need two batteries. One should be a START ONLY battery and the other will be HOUSE, or everything else.
You want to keep both of these battery "banks" (think of using them like drawing upon an account) as full as possible at all times in case of one side going bad.
The single best way to do this is with a Voltage Sensing Relay. There are several out there for sale and are known as VSRs, ASRs, ACRs, and other alphabet soup. They all do the same thing; charge one bank until it is full, then "bleed" off extra voltage to the second bank. They do this automatically, you just wire it up and the whole system takes care of itself. These eliminate the dreaded 1,2,BOTH,OFF switch so you never have to fool with one ever again. In addition, they do not require any voltage of their own to speak of.
In the old days the tasks that a VSR can do automatically were done in a variety of ways. The aforementioned selector switch which you never knew whether the battery you switched away from was fully charged or not. Battery Isolators, which are big Zener diodes potted in epoxy and mounted on a heat sink. These don't work because they steal at least a whole volt of charge, so even under the best circumstances you can't get a good full charge very fast. Lastly there were all kinds of solenoids hooked up to oil pressure switches and stuff so the batteries would only charge when the engine ran and would disconnect when it was off. All obsolete, over and out.
The venerable ABYC has written electrical standards that include automatic battery management. Yet to this day you still see manufacturers selling boats with big red 1,2,BOTH,OFF switches as if we were our own voltage sensing relays and knew when to switch. Some day they will get on board with modern technology. The arguments against it are insensible.
Plenty more to read at amplepower.net. An excellent book is called the 12 Volt Bible and covers much in a way that is easily understood.

I changed my battery setup and would appreciate any advice because I am not sure it is the best way to set up my 4 group 27's. All four a wet acid, 2 came with the boat, and two I purchased a few months ago. I have four on-off Perko's: Starboard, Port engines, House and Generator. For the house, I have the two older batteries in parallel. The generator is connected to the Port Battery.

Charged by a Promariner 50 Amp - 3 bank charger. I also have 2 Yardina isolators wired between the Starboard and House battery. I then have the other Yardina wired between the Port and 2nd house (in parallel with the other house battery).

Hope I explained this well enough. So far, everything seems to be working well, but as I mentioned, I am not sure this is the best set up.

From your description it sounds like you have the installation correct. Check Yandina.com for the correct wiring diagram.
I'd connect the genny output to your house bank, and let the Yandina do its thing from there. You will be drawing from those when the engines are off and you are on the genny or nothing.

Yes, I did follow Yardina's suggestions for wiring the isolators. But thought it would be prudent to check with you guys here. I have received so many good suggestions from this web site, it is my favorite.

Following the MFG's instructions is the prudent path. yandina's been making stuff for a while and has established a good reputation.

Just for the record, you won't find any Zener diodes in the 'old fashioned' isolators but good ol silicon diodes, very similar to those used in the alternators. The ACRs work a bit differently than described above; they 'turn on', connecting the batteries it 'controls' when they sense a charging source and they 'turn off' when that source stops producing. There's no 'extra voltage' to 'bleed off'. They don't replace battery switches but, as noted, eliminate the need to move the switch to maintain charge of a pair of batteries.

It's prudent to have a method of 'bridging' your starting batteries and using solenoids is the 'modern' approach. They beat modern electronics, everyday, from a cost effectiveness perspective.

Just for the record, you won't find any Zener diodes in the 'old fashioned' isolators but good ol silicon diodes, very similar to those used in the alternators.

My mistake, I meant Schottky diode. I'm not a Double E. For a dual channel that will do the isolation job, it will set you back about $26 from Digi-Key. Marinco will do you the favor of potting them in epoxy and selling them to you for about a hundred bucks. Even so, the Yandina or Blue Sea or Ample Power or other VSR is the way to go.

I hope nobody has gotten lost in all this jargon.

This is interesting, my Trojan International doesn't (and never had) a battery selector switch like it seems every other boat has. I do have the factory "emergency" solenoid switch at the helm.

With my two start batteries, the port battery runs the port side 12v "house" and the starboard does the same. The drain on my port side is minimal, just lights. Worst case is I kill my stb start battery and I have to use the switch to get started.

I have a dedicated battery bank for my wet bar fridge (two "Trojan" 6v batteries) and carry a set of jumper cables which is my back up for the back up. I'm usually not more than two nights on the hook and haven't had to do any of the above yet.


Bob

I have a 'normal' starting battery on ther port side, and 4 deep cycles on the other side. A dual bank charger keeps the "house" batteries up, where a simple trickle charger easily maintains the port starting battery--all it needs. This has been a successful setup for some time, and there are NO electronic gizmos involved--just a simple Perko battery switch.

Jeff

I have two group 27 starting batteries in paralllel whose sole responsiblitiy is to start the port motor. (Actually they also start the genset too, which drives the battery charger). Four group 27 deep cycle batteries in parallel start the starboard motor and supply the house. There is a paralleling switch up at the helm. I had to use it once when the house batteries ran down to the point where the starboard motor wouldn't start. Worked great. Started the Port motor, let the port battery bank charge for 10 minutes, hit the parallel switch and the starboard motor fired instantly.

And I thought that I had lots of batteries!

Jeff