House and start battery jumping...

[Osprey69]

So I discovered my house bank (2 8Ds, #1 and #2) are not being charged by the CAT 3208s while underway

Starboard engine is not charging its start battery (single 8D, #4).

Port engine is charging its starting battery (again single 8D, #3).

To me having only 2 house 8D house batteries, and not tapping into another 8D makes no sense given all that battery capacity sitting idle 98% of the time.

Conveniently #3 start battery (the one being charged) is on a 1/2/all/off switch next to the house battery 1/2/all/off switch.

There is no jumper from that start #2 battery switch pole to the house #2 batt switch pole.

I intend to jump that start battery to join the house bank when both switches are on "all". I get house charging underway and increased capacity all for the cost of a single chunk of hefty wire.

I think.

Understanding I need to be careful to not drain a start battery. If I do - 1) the generator can charge it, 2) use a jump pack, 3) come home on one engine or 4) replace the starboard switch from a 1/off to a 1/2/all/off and jump the 2 starting batteries together also (this seems to make the most sense).

Am I missing anything here?

And as a related question, need I put a smart regulator on the alternator out put (standard alternator) to assure I get the most out of it? Given battery bank size, I am thinking I do not.

Thanks in advance.

 

[ranger58sb]

What is the alternator on your starboard engine doing, then? Nothing?

-Chris

 

[Osprey69]

Apparently...have not dove into that yet.

 

[Portage_Bay]

A question and a few comments. With the caveat that there are far more knowledgeable persons here on the subject of batteries and charging.

I've got a pair of 3208s with OEM alternators. Both engines started from one 8D. One alt charges house bank, the other start battery.

Question. Are your 3208s set up with the OEM alternators? If so they have a max output of about 50 AMPs. Real output is far less. The highest output I've measured is 27 AMPs. After the normal running load that doesn't leave much to charge the house bank. If we're using the inverter we will usually be going backwards. The start bank is easily topped up by it's alternator.

Comments. You have far more start battery power than a pair of 3208s need. A single 8D is more than enough. That's what I have and it works great. 3208s start very easily. I do have the ability to tie in the house bank if the start battery is low. I also have an oversized battery on the gen that could be used to start the mains.

Simply jumping house and start bank may work. It may not. This is where the TF experts should chime in. Most of the time I think two internally regulated alternators will not play well together. One will end up doing almost all of the work. There is at least one TF member who says otherwise.

I understand your desire to improve the setup at minimal cost. If you are reluctant to spend big $$$ for a major upgrade maybe consider reconfiguring you system to have 3 house batts and 1 start batt. One alternator to charge the house bank, the other to charge the start battery. You're still in the cost range of some cabling. You've got all 8Ds so if they are same age and same capacity it should work. If not than maybe not such a good idea.

Next step up would be to replace one alternator with something bigger. If your 3208s are like mine then without significant modifications you'll still be running a single belt alternator. But rather than the OEM internally regulated 55 AMP it could be a 95 - 105 externally regulated alternator. You could expect to see 2X or even 3X the charge into the house bank.

For the gold plated upgrade the bigger alternators on both engines, both charging the house bank, the house bank charges the start battery. There are lots of ways to skin that cat depending upon how much $$$ you want to spend.

My final comment. On a day where I know the DC demand will be high, or the house bank is depleted I run the gen while underway. Not a great choice but until I can implement a significant upgrade it works.

 

[Osprey69]

Portage...thank you for your thoughtful reply. The alts are OEM. As only one alternator is seemingly outputting, no conflicts there. And even at low amp charging, some is better than none.

I thought one 8D would be enough for starting both. It seems if I change the one battery switch to 1/2/all/off I can interconnect at will as a plan B in case of a low start battery.

A conflict might be if underway and the generator is started and the chargers kick in. But as you mentioned greater minds than I might have a thought on that one.

I configured my sailboat with upgraded everything to "Gold Plated" and may do so here at some point, but not a priority yet.

 

[Hookmeup]

Cat 3208 alternator upgrade

I upgraded to 100A alternator on my Cats as we are not marina dwellers along with a Promariner charge manager for the two engines. Once the engine batteries are topped up all.charge from both engines is diverted to the house ban it also has an output for the generator Batt .I added smart regulators in the upgrade. You need to upgrade using small frame alternators as clearance to the manifold is minimal. The Cat original alternators maxed at 27A as mentioned by others and engine room blowers and navionics probably use all of that underway.
As others have said many options. I think one dedicated start battery is ok as long as you can jump in an emergency somehow. Good luck !

 

[Portage_Bay]

I have not had any problems with running battery charger from generator and engine alternators at the same time.

A conflict might be if underway and the generator is started and the chargers kick in. But as you mentioned greater minds than I might have a thought on that one.

 

[jgwinks]

Apparently...have not dove into that yet.

Are your tachs alternator driven and do they both work? If so that alt is doing "something". If it was completely dead the tach would be too.

 

[ranger58sb]

My final comment. On a day where I know the DC demand will be high, or the house bank is depleted I run the gen while underway. Not a great choice but until I can implement a significant upgrade it works.

I have not had any problems with running battery charger from generator and engine alternators at the same time.

FWIW, I don't see using the generator+battery charger as a bad choice.

Seems to me easier and possibly no more expensive in the near- to mid-term than leaping through hoops to configure an alternator to apply what is often a "relatively" minimal charge to batteries while underway.

A couple gallons of diesel. Occasionally.

-Chris

 

[O C Diver]

My recommendation would be to map the wiring out thoroughly before making changes. Also determining whether the starting alternator is working. Finally determine whether the 8D batteries are deep cycle or not.

Wiring two engines off of one start battery is not unheard of. Just start the engine with alternator charging the battery first. Not sure if there is any issue with the tach signal.

As already mentioned, an alternator isn't a battery charger. To convert it, generally requires an external multi stage regulator. If your cruising style benefits from the upgrade, a new higher amperage alternator with an external multi stage regulator, could save you a lot of generator time.

Routinely draining non deep cycle batteries is a guarantee for a back pain (when you have to swap out those 8Ds). I would check the manufacturer's website to see the level of tolerable discharge. The vast majority of 8Ds aren't deep cycle.

I have a paralleling switch between my start battery and house battery. Used it when the start battery finally aged out, and another time when the house alternator's multi stage regulator died. Having a plan B with a simple battery switch is a good thing!

Ted

 

[Simi 60]

We have a small victron smart charger permanently connected to the starts.
Ran the boat full time for about 2 years without any alternator at all
Now have an alt again, but charger still connected.

 

[High Wire]

With all chargers shut down, start the starboard engine only and advance the RPMs to about 1000. Does ANY battery voltage rise above 12.8 volts?

 

[Osprey69]

HW....thanks but just did it again. No joy. Once I get the new config settled in, will start to chase that alternator down.

 

[JDCAVE]

…Also determining whether the starting alternator is working…

Ted

You should be able to determine this with DC clamp meter.

Jim

 

[CharlieJ]

As others have noted in previous threads, stock alternators are fitted to replace the Ahr removed from a starting battery during engine start and to produce enough power for the engine related electrical/electronic equipment. That's it. There really is no allowance for a stock alternator to efficiently charge a house bank. If it does, it is just luck. But...

Many suffer from SBA; Starting Battery Anxiety! Here is a simple exercise to show how little starting an engine draws from the battery:
>> Assume that an engine takes 1,000A to start
>> Assume that this engine must crank for 3.6 seconds to start
>> The Ahr used is therefore: 3.6sec x 1,000A = 3,600Asec
>> There are 3,600 seconds in an hour so converting to Ahr:
3,600Asec/3,600sec/hr = 1Ahr

So, with a stock alternator we do get lucky, my mythical engine starts using 1 Ahr which is restored very quickly by the stock alternator which then can then start replenishing the house bank. This is why most pros will recommend all charging sources charge the house bank and then use a device (ACR, DC/DC converter, FET isolator, etc.) to charge the starting batteries.

 

[pjtemplin]

As others have said, map it all out. I'd also add that you need to confirm if ALL batteries are the same chemistry (flooded lead acid, AGM, Firefly, LFP, other lithium). If they're the same, you can tie them together and let one alternator charge the unified grouping safely. If they aren't, one chemistry is apt to "lose" and end up not only discharged, but quite possibly dead and unchargeable even if you rectify the mistakes made. {Note that you need to keep this in mind not only today, but forever into the future.}


My suggestion would be either dedicated alternators for start group and house group. If you have multiple start groups, leverage a FET isolator to allow that start alternator to charge each of the independent start groups simultaneously while not actually tying them together, then leverage an ACR in manual mode to combine the start groups only if you end up with a weak/failed start group (so you can get the other engines started a few times until you can resolve the issue). OR use a DC-DC charging converter to tie from one chemistry group to another. It won't be enough current flow to jump-start anything, but will ensure that the "source" group (charged by the alternator) can then charge the "destination" group (fed by the output of the DC-DC converter).

 

[Osprey69]

Thanks all. Already mapped. Rather simple actually. Batteries all the same type, age etc.. Happy that at least one alternator is replacing some juice in house/start batteries while underway. With my switches and jumps, I can isolate or combine house with one start battery and can combine both starts just in case.

 

[Pete Meisinger]

Here is how "non-technical" I am:

In my humble opinion, 8Ds do not belong on a boat. You will eventually have to replace them and that is where the problems start.

pete

 

[SteveK]

Conveniently #3 start battery (the one being charged) is on a 1/2/all/off switch next to the house battery 1/2/all/off switch.

Why does the house bank need a 1/2/all/off switch? Maybe just an on/off but 1 could be house, 2 could be crossover to the starboard start, 'all' could share charge.

You mentioned starboard alt not charging anything, hope the alt is not switched.

 

[Steve DAntonio]

If both alternators are charging the same bank, unless heavily depleted, one alternator will often stop producing power, as it senses the higher voltage from the other alternator. If you haven't already, you should test alternator output from each engine individually, with only that engine running, and all chargers turned off or shore power disconnected, as a battery charger connected to the same battery as an alternator will also cause the alternator to cease producing power.

It's possible the non-charging alternator is dedicated to the house bank, that's not unusual.

And, today, pretty every engine manufacturer requires that propulsion engines have dedicated, and not shared start batteries. As others have said, your house batteries should remain segregated from house loads except in emergency parallel situations.

 

[SteveK]

..............................
And, today, pretty every engine manufacturer requires that propulsion engines have dedicated, and not shared start batteries. As others have said, your house batteries should remain segregated from house loads except in emergency parallel situations.

After doing some internet searches I come up empty.

You made the statement, back it up with engine manufacturers of the common twin boat engines that proclaim this. Will we see this as an ABYC mandate?

Where outside of boats would twin engines exist along with a second bank for house needs.
One or two separate start batteries should be a personal choice.

 

[Portage_Bay]

OP is running Cat 3208s. Which is what I have. Those old skool engines are perfectly happy sharing a single 8D. I recently had some fuel system work done. Both engines required multiple start attempts of longer cranking than usual. The 5 year old 8D handled the work load just fine.

Some redundancy or backup is important but it doesn't have to be a 2nd 8D.

 

[Osprey69]

Why does the house bank need a 1/2/all/off switch? Maybe just an on/off but 1 could be house, 2 could be crossover to the starboard start, 'all' could share charge.

You mentioned starboard alt not charging anything, hope the alt is not switched.

Boat came with house 1/2/all/off switch. And I am not seeing a switch yet.

 

[Osprey69]

If both alternators are charging the same bank, unless heavily depleted, one alternator will often stop producing power, as it senses the higher voltage from the other alternator. If you haven't already, you should test alternator output from each engine individually, with only that engine running, and all chargers turned off or shore power disconnected, as a battery charger connected to the same battery as an alternator will also cause the alternator to cease producing power.

It's possible the non-charging alternator is dedicated to the house bank, that's not unusual.

And, today, pretty every engine manufacturer requires that propulsion engines have dedicated, and not shared start batteries. As others have said, your house batteries should remain segregated from house loads except in emergency parallel situations.

Tested each start battery individually with chargers off and with engines on individually. Already knew house batts not being charged at all by alts. Hence the start of all this.

At this point I can have all connected (which should never happen), One start batt per engine dedicated or 1 start batt for both engines with the third added to the house if need be.

All for an additional 1/2/all/off batt switch and two 2/0 gauge jumps. $75 bucks and maybe 45 mins of labor. Pretty cool. I

 

[LarryM]

After doing some internet searches I come up empty.

You made the statement, back it up with engine manufacturers of the common twin boat engines that proclaim this. Will we see this as an ABYC mandate?

Where outside of boats would twin engines exist along with a second bank for house needs.
One or two separate start batteries should be a personal choice.

Here are a couple of excerpts from the "Cummins Marine Recreational High Output Propulsion Units B and C Series Installation Directions" and Fig. 59, Typical Dual Engine Positive Side Battery Setup from the same manual.

"To crank the engine fast enough to insure reliable start, correctly sized batteries and cables must be installed."

"Cummins recommends that each engine have a dedicated battery or batteries. Accessories should run off of a separate battery that is not used for cranking the engine."

"The ECM must be wired directly to the corresponding engine battery."

There may be other references in this 114-page manual, but these were some I easily found in the Starting/Electrical section.

 

[Steve DAntonio]

I'm not sure I have seen a modern, electronically controlled propulsion diesel installation guide that didn't call for a dedicated starting battery, the aforementioned Cummins excerpt is typical.

Here's another for Northern Lights, a dedicated battery is recommended in the IM1000 Installation Manual. See page 15, paragraph 3, second sentence. “Dedicated generator batteries should be used.” So, for gensets too. Attached.

And, from the Volvo D9 installation manual..."Separate starting battery group for each engine (driveline)." see attached screen shot.

I could keep digging these up, but with electronic engine manufacturer's sensitivity to voltage transients and voltage stability for ECM's (it's why many want a separate cable run from the ECM to the battery) it's virtually a given that they do not want excessive voltage drop (like that which occurs when starting) on a start battery, and ECM, for an engine that is already running.

I do encounter new and newish vessels, with electronic propulsion engines, that share a single start battery bank for two engines, I usually cite it as a violation of the engine manufacturer's installation guidelines. And why run that risk, propulsion is critical, how hard is it to provide a dedicated bank for each engine? And they need not necessarily be 8Ds, they only need to have the requisite CCA and reserve capacity.

If the engine manufacturer doesn't prohibit it, then it's not a violation of the installation guidelines, but I still see it as false economy.

Having said all that, for non-primary propulsion engines, I have set up shared start banks, one bank for two gensets (a technical violation of at least the NL guideline), or one bank for a genset and a wing engine for instance.

For mechanical engines, agreed, it's probably not an issue, but still false economy IMO.

 

[SteveK]

ECM's. SDA good explanation. Can see the sensitive electronics need for a steady voltage after start being interrupted by a 2nd cranking. Put into that context only non ECM engines should use the same battery.

 

[Inbreaker]

A lot of good advice here.
I have twin 3208TAs with a single 8D to start them both. There is an ACR between the start and house bank circuits.
I added a switch to combine the banks in case of fiasco.
Starting has never been an issue.
The issue has been that the OEM alternators would never bring the house bank to 100% charge and it is foolish to try to achieve that with a generator.
I have replaced the OEM alternators with 90amp Leece-Nevilles that fit in with a minor modification to a terminal post. We're waiting on the delivery of Wakespeed regulators, which I settled on after some excellent advice from a member here.
Those, I believe, should do the trick.

 

[Bacchus]

ECM's. SDA good explanation. Can see the sensitive electronics need for a steady voltage after start being interrupted by a 2nd cranking. Put into that context only non ECM engines should use the same battery.

Yes I agree. I have seen many arrangements with separate starting battys for twin engines and never saw the need or benefit. SDAs explanation is the first argument for that arrangement with a solid explanation of why.
Thanks to Steve DA.

 

[dhays]

FWIW.....

I have a Cummins QSB engine. From painful experience, I can attest that electronic engines don't like having anything else connected to their engines batteries. Sometimes things work out great, other times they don't. When they don't work out well, it can be very, very bad.