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Old 08-16-2017, 07:18 PM   #1
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Mix type House Bank Charging

Gidday

Question. I have start and house banks. I want to charge my house bank from my engine when its running. Obvious answer is a VSR but this allows current in two directions which may mean the house bank on solar or 240v charger will charge the start bank.

I should mention start bank is normal lead house bank is agm.

I have been looking at DC-DC chargers. This allow current in only one direction. But i am struggling to fine one that will charge an AGM to its specifications.

Does anyone have any experience in this area?

Or maybe a solenoid that joins start to house only when ignition is on? But this would mean start current would come out of the house batteries...

A bit fat diode?

https://www.redarc.com.au/smart-start-bcdc
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Old 08-16-2017, 07:23 PM   #2
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Where you perceive a problem there is none.

Set all charge sources to the AGM mfg specs.

That will be fine for the starter.

Or a $50 ignition-based solenoid.
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Old 08-16-2017, 08:43 PM   #3
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John knows more about batteries than I ever will, so take anything I say with lots of salt.

I would suggest you set al, your charging sources for your house bank profile and then use a Balmar Duo-Charger to charge your start battery. You can set the Charge profile independent of how the house bank is being charged. It will only charge the start battery when the house bank voltage is above 13v, i.e. When it is being charged by some source.

I hav two that I use and they work great. Caveat, don't use the Balmar Duo-Charger for f you have an electronic Cummins engine.

I also use an Echo Charger that works great. However, it will send the same charge voltage to your starta s the house bank is getting.

Please forgive the bad typing. I am sitting in a recliner on my boat deck in the sun having a couple of rum and cokes. Hard to see the screen with the glare.
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Old 08-17-2017, 12:13 AM   #4
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john61ct

so what your saying is the AGM charge cycle for the house AGM will be no issue for the Start Batteries
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Old 08-17-2017, 02:01 AM   #5
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yes

no need to strive for perfection with the FLA starter, they're robust, very tolerant

dhay's way is fine too, as is a full B2B DC-DC charger to avoid voltage following, just no need

if you want to spend money on simple and robust rather than unneeded complexity
https://www.bluesea.com/products/762..._-_12V_DC_500A

Or go cheap and carry spares

http://forum.expeditionportal.com/th...y-setup-for-50
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Old 08-17-2017, 02:21 AM   #6
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You could put in an ACR.
https://www.bluesea.com/resources/1366
https://www.bluesea.com/products/761...12_24V_DC_120A

Use the AGM profile for your charger, the start batteries wont be impacted much at all.

Edit:
Just saw John's post. He directed you to a higher capacity unit that I did, not sure what size alternator you are using.
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Old 08-17-2017, 11:15 AM   #7
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If you want simple and relatively inexpensive, seriously consider the xantrex Echo-charger. Extremely easy to install, just three small gauge wires (unlike the ACR where you need battery cable). It will charge your start battery at 15 amps while there is a charge source on your house bank. Can't get any simpler and very reliable.

It is also very inexpensive. You can buy one from CMS on his howtomarine.com website. This is what I replaced my Duo-Charger with and it works great.

https://shop.marinehowto.com/product...l-echo-charger
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Old 08-17-2017, 11:52 AM   #8
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Yes Echo Charger is great. Just note if you want Alt to charge House, need to rewire that direct, then the low-amps from House to Starter is fine.

If leaving Alt output on Starter batt then hi-amp wiring, combiner / B2B needed to feed House, both dhays devices are too low.

Note self jumpstarting from house is Big Amps.
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Old 08-17-2017, 12:06 PM   #9
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Quote:
Originally Posted by john61ct View Post
Yes Echo Charger is great. Just note if you want Alt to charge House, need to rewire that direct, then the low-amps from House to Starter is fine.

If leaving Alt output on Starter batt then hi-amp wiring, combiner / B2B needed to feed House, both dhays devices are too low.

Note self jumpstarting from house is Big Amps.


Thanks for those reminders John. I have all charging sources go the house bank and forget that some have their Alts charge their start batteries direct.
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Old 08-18-2017, 12:12 AM   #10
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Most people use somewhat the reverse of what you say you have. You say your setup is AGM for house and wet cell for starter? Often house bank is many wet cell batteries.

ANother simplification would be change the starter set to AGM so all the batteries use the same charge profile and use an ACR/VSR or the Echo Charger.

Feed that alternator direct to the house bank. Then when the house bank has come up to the setpoint voltage the relay will close and charge the starter set.
YOu could also use what Dhays suggested in this case so either way the battery set is simplified.

Shouldn't matter if the solar charges the starter set as it will only get charged when the house set is almost charged.
Something to think about.
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Old 08-18-2017, 06:51 AM   #11
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"Or maybe a solenoid that joins start to house only when ignition is on?"

An RV merge solenoid is fired from the ACC position on the engine key switch.

It does not join the batts during cranking.

Cole Hersey sells marine start switches with this feature.

KISS
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Old 08-18-2017, 07:28 AM   #12
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Those that use solenoids or VSRs, do you have fuses or CBs to protect the wire run between the house bank and the start battery?

If I forget to shut off the combine switch, I blow that fuse when starting the engine.

What's everyones solution for that? I am guessing the VSRs arent connecting the batteries yet or connected long enough during the start phase to blow the fuse?
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Old 08-18-2017, 10:10 AM   #13
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Any large bank should be well fused very close to the post.

An ACR doesn't close until after V rises, good ones after a delay to prevent chatter.

Good VRs let the engine ramp up before Alt output does.
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Old 08-18-2017, 10:21 AM   #14
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I have an ACR from COle Hersey. It does not close untill the house battery reaches about 13.5 volts, from memory. That never happens untill the alternator has been operating a while.
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Old 08-18-2017, 01:34 PM   #15
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I assumed VSRs might be OK, but an ignition activated solenoid migh not be for battery terminal fused that protect house to staryer battery runs.
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Old 08-21-2017, 07:01 AM   #16
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"If I forget to shut off the combine switch, I blow that fuse when starting the engine."

By using a solenoid powered by the ACC position on the key switch , the merge solenoid is not powered during start .

No combine switch needed , its automatic.

https://miamialternatorsandstarters....duty-52-307-1/

Or Cole Hersey has a version ,
also under $20.00
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Old 08-21-2017, 09:49 AM   #17
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http://forum.expeditionportal.com/sh...ad.php?t=77503
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