Dissimilar battery types in different battery banks❓

[nortada]

With a split output mains charger is it feasible to have 2 different battery banks? One deep cycle or leisure battery bank for domestic loads and the other cranking battles for engine start.

 

[Refueler]

Risking being shot at dawn ... if all batts are Lead Acid - then the charging regime of each is not significantly different .... so there should be no reason to be concerned.

The main factor to be aware of - and TBH rarely - is that Deep Cycle do not like high charge / discharge rates due to the soft plates ... its why a TRUE deep cycle should never be used to start an engine other than in emergency - the high demand current can risk buckling plates ... NOTE - I said TRUE deep cycle - as many Leisure batts sold are 'compromise' batts developed for RV market and not full deep cycle.

 

[Tranona]

Check the charging profiles for each. Many modern mains chargers allow you to set the profiles for each individual output.

 

[B27]

The two banks will be at different states of charge? So one might want a float charge while the other is still bulk charging.

You'd have to RTFM for the units you have in mind.
A small 'maintenance charger' for the engine battery as a separate unit might be cheaper and better?

 

[PaulRainbow]

Check the charging profiles for each. Many modern mains chargers allow you to set the profiles for each individual output.

This is not correct. Whilst they do exist, charger that offer different profiles for each bank are very rare and relatively expensive.

 

[Supertramp]

I put separate isolation switches on the charge lines for engine and domestic batteries so that the engine battery is isolated from the mains charger. If I ever top the engine battery, I isolate the domestic, switch on the engine battery and the smart charger charges the engine. In practice, the engine battery doesn't need charging - the engine does it after starting. Both banks are sealed lead acid.

 

[PaulRainbow]

With a split output mains charger is it feasible to have 2 different battery banks? One deep cycle or leisure battery bank for domestic loads and the other cranking battles for engine start.

It's possible to have two different banks, but only if they can both be suitably charged on the same voltage settings. You don't provide enough information to say whether that's possible for you, you need to say exactly what batteries you propose to use.

As mentioned in post #2, many batteries advertised as "deep cycle" are not deep cycle.

 

[ChromeDome]

This is not correct. Whilst they do exist, charger that offer different profiles for each bank are very rare and relatively expensive.

Been there, done that. Had one 3-channel charger (channels separated inside the charger but supplying the same staged charge-program).

Replaced by 3 individual chargers, each maintaining its own bank (1: Starter 2: Starter 3: Domestic, true AGM deep-cycle).
Monitored by an app, clearly showing the differences in the charge regimes.

From a separate thread on the process:

Just wanted to report back, after running the setup for some time:

Removed old charger from the cabinet by the helm (took some acrobatics, but eventually got it out).
Decided that the new setup should live in the lazarette, close to the batteries, and have their own fitment. Hence connected a certified installation 3x2,5 mm² cable approved for wet, submerged, underground and what not use from the shore power fuse box to the lazarette and fitted a 3-pin IP68 female connector.
Then fitted the three Victrons to a waterproof, phenolic plywood plate, and routed main cables to an IP68 connection box which had a male connector to the mains feed.
Each Victron's fused charge leads had a 2-pin 60A waterproof connector fitted behind the fitting plate, connected to each battery by 2x6 mm² heavy-duty rubber cables. All wires are labelled. The use of connectors facilitates easy removal of the panel with chargers if need be.
View attachment 162838
Must say it works beyond expectation. Each Victron connects to the app on the phone and onboard tablet, clearly monitoring each and providing data - of which the History displays with charging cycles and charged amounts is very useful.

 

[geem]

Risking being shot at dawn ... if all batts are Lead Acid - then the charging regime of each is not significantly different .... so there should be no reason to be concerned.

The main factor to be aware of - and TBH rarely - is that Deep Cycle do not like high charge / discharge rates due to the soft plates ... its why a TRUE deep cycle should never be used to start an engine other than in emergency - the high demand current can risk buckling plates ... NOTE - I said TRUE deep cycle - as many Leisure batts sold are 'compromise' batts developed for RV market and not full deep cycle.

That's not correct for Trojan deep cycle. They can start engines. Not all deep cycle are the same. You are correct that some, like the old 2v cells used in battery back up systems are not designed for such loads but that's isn't the case with my batteries. Lots of Trojan batteries are used for motive power applications and they are deep cycle.

 

[Refueler]

That's not correct for Trojan deep cycle. They can start engines. Not all deep cycle are the same. You are correct that some, like the old 2v cells used in battery back up systems are not designed for such loads but that's isn't the case with my batteries. Lots of Trojan batteries are used for motive power applications and they are deep cycle.

I'm sorry that I did not write a novel length list of those that can and those that should not .... the GENERAL situation is that common Deep Cycle (True) should not be used for engine starting ...

A good check when buying so called Deep Cycle - is to look at label / ask seller ... what is CCA of this battery ... if he quotes a number - its NOT true Deep Cycle ... its most likely a compromise battery. If label has no CCA stated and seller says no CCA value - then maybe its a true DC battery - but even then no g'tee as it could be still a compromise battery.
True Deep Cycle batterys are not so easy to find since the caravan / RV world got into compromise batterys ... shops sell what they call "Deep Cycle" but in truth they are only marginally better than a straight cranker ...

 

[geem]

I'm sorry that I did not write a novel length list of those that can and those that should not .... the GENERAL situation is that common Deep Cycle (True) should not be used for engine starting ...

A good check when buying so called Deep Cycle - is to look at label / ask seller ... what is CCA of this battery ... if he quotes a number - its NOT true Deep Cycle ... its most likely a compromise battery. If label has no CCA stated and seller says no CCA value - then maybe its a true DC battery - but even then no g'tee as it could be still a compromise battery.
True Deep Cycle batterys are not so easy to find since the caravan / RV world got into compromise batterys ... shops sell what they call "Deep Cycle" but in truth they are only marginally better than a straight cranker ...

Here we go again. Your words. TRUE DEEP CYCLE. are you never wrong?

 

[Refueler]

Here we go again. Your words. TRUE DEEP CYCLE. are you never wrong?

Do you not read fully ....

So are you saying that they do not exist ? If you are - then sorry old bean - you need to go back and check again ...

 

[geem]

Do you not read fully ....

So are you saying that they do not exist ? If you are - then sorry old bean - you need to go back and check again ...

No, I am saying that I have true Deep Cycle batteries that can start an engine. It's very common

 

[Refueler]

 

[Buck Turgidson]

my house battery has 1800 amps cranking rating. It could start a train!

 

[nortada]

Thanks for all of the inputs

Both of my Sabre 300hp engines start at the turn of the key - no real cranking at all. To prove the system I frequently start the second engine of cross feed so the first engine alternator/battery bank provide the power.

My original thoughts were to provide the best sources of power for a given situation - domestic/engine start.

 

[MAURICE]

I have a sealed battery for starting the engine and 3 very very heavy deep cycle batteries for the house. I have a Sterling? regulator on the alternator which i have set to charge both at 14.4v this will charge the starter battery and also the house batteries without damaging the sealed battery. When on shore power the batteries are managed by a inverter charger. All have operated perfectly for the last 3 years like this. (I also have 180w solar panels)