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Old 12-06-2018, 09:31   #1
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Lead acid for house AGM for start

Planning my electrical refit. Was thinking of going 4 trojan 6 volt batteries for the house. Then getting a small odyssey AGM for starting. my charging system is a 150 amp balmar 6 series alternator with an external and a trace charger inverter. The house and start batteries would be combined using an Blue Sea ACR. If i set my regulator and battery charger to lead acid mode will my AGM start battery be compromised?

I haven't found any information on this particular setup. any insight would be appreciated. cheers
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Old 12-06-2018, 09:47   #2
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Re: Lead acid for house AGM for start

The Balmar Duo Charge allows for different battery chemistries between banks. It would replace the ACR. Basically it is a regulated charger for the starting bank in place of a simple relay.
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Old 12-06-2018, 10:45   #3
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Re: Lead acid for house AGM for start

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Originally Posted by 561blake View Post
Planning my electrical refit. Was thinking of going 4 trojan 6 volt batteries for the house. Then getting a small odyssey AGM for starting. my charging system is a 150 amp balmar 6 series alternator with an external and a trace charger inverter. The house and start batteries would be combined using an Blue Sea ACR. If i set my regulator and battery charger to lead acid mode will my AGM start battery be compromised?

I haven't found any information on this particular setup. any insight would be appreciated. cheers
Yes I believe it will be compromised, lead acid to match your main bank is better.
Or just charge it separately occassionally with a good 120v charger
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Old 12-06-2018, 11:16   #4
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Re: Lead acid for house AGM for start

Do you need an AGM battery for starting the engine? How about an ordinary car battery and then you don't have to worry. If the engine starts quickly like a car engine the amount of power used is actually tiny.

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Old 12-06-2018, 12:12   #5
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Re: Lead acid for house AGM for start

My start battery is located in an tight space that makes proper ventilation difficult. This is why I find the sealed battery appealing for starting. I was also considering going with gel or AGM for the whole system (start and house), but it seems that despite being considerably more expensive I will not be able to make the same amp hours as the 6 volt golf cart series parallel arrangement.

Thanks for the quick responses
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Old 12-06-2018, 12:18   #6
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Re: Lead acid for house AGM for start

Most AGMs don't self-discharge very much. Is it a diesel or gas boat? If diesel, maybe just let the engine alternator do the charging when you're running... and carry a set of jumper cables just in case. Or if it's gas, add a parallel switch just in case. Or do both in a diesel boat, for belt-and-suspenders just in case.

??

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Old 12-06-2018, 12:47   #7
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Re: Lead acid for house AGM for start

My alternator regulator charges my flooded lead acid house bank with a 14.8V absorption. My Eco-Charge charges my AGM starter battery from the house bank with a voltage limit of 14.4V. I do not parallel the house and engine batteries. The start battery is located in a place that would make it difficult to service a flooded lead acid battery.

You may also be interested in Optima spiral batteries that have charging requirements similar to flooded lead acid.

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Old 12-06-2018, 12:52   #8
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Re: Lead acid for house AGM for start

AGM is lead-acid too. When you guys write "lead acid", I believe you mean flooded lead-acid. /pedant mode off

I would speak up for WSMurdoch's solution -- use an echo charger. Combining start and house batts are a bad idea even with the same chemistry. Echo charger was made for this problem and work great -- giving the starter batt its own charging profile.

If you leave the boat for a long time and on shore power, you might consider adding a small AC battery charger.
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Old 13-06-2018, 08:23   #9
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Re: Lead acid for house AGM for start

Here is a really good add-on to the already great responses you receive to your question. Pull up the battering manufacturer specifications and see the recommendations for your next charge voltage and float. If they are the same for both battery types you are in good shape. If they are different then the balmar duo would be a good solution. Good luck
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Old 13-06-2018, 08:23   #10
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Re: Lead acid for house AGM for start

Over a 50 year period, I have only lost batteries when I forget to remember to top them up. Therefore I now only have batteries like the AGM which do not require me to look after them in terms of distilled water. I do have digital voltmeters connected to each bank which I can monitor from my armchair.
This makes just one less problem that I need to worry about!
For engine starting just worry about the CCA (current) that the starter motor takes. This will be part of the engine spec and battery spec.
For service make sure that the batteries are deep discharge.
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Old 13-06-2018, 08:34   #11
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Re: Lead acid for house AGM for start

Star,
What you are proposing is exactly the configuration in my boat. No issues.
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Old 13-06-2018, 08:52   #12
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Re: Lead acid for house AGM for start

My next boat starting battery is going to be an OPTIMA battery. I just replaced one in a car that was 11 years old and still starting the car. Over that time I did absolutely nothing to it. They work fine with standard LA charging profiles, as long as they aren't discharged under 10.5V and that isn't happening on a starting battery.
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Old 13-06-2018, 09:16   #13
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Re: Lead acid for house AGM for start

Look at any Balmar regulator installation manual. Balmar | Marine Charging Systems | Battery Monitors | Multi-Stage Voltage Regulators | High Power Alternators | Serpentine Pulley Conversions Every single one of them shows the factory settings for different battery types. What you will find is that the voltages for wet cells and AGMs are remarkably similar. For using an AGM as a start bank with Trojans for the house it will NOT make any difference. Set the charger and alternator output for the Trojans, and use any type of VSR to charge the start bank and you'll be just fine. Start banks, as proven over & over again by Maine Sail, hardly ever need much charging because starting, even with glow plugs, uses only a few Ah. Voltage is pressure and the battery acceptance for the start bank is SO LOW that almost no amperage is gonna flow anyway.


This is NOT an issue.
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Old 13-06-2018, 09:44   #14
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Re: Lead acid for house AGM for start

Quote:
Originally Posted by 561blake View Post
Planning my electrical refit. Was thinking of going 4 trojan 6 volt batteries for the house. Then getting a small odyssey AGM for starting. my charging system is a 150 amp balmar 6 series alternator with an external and a trace charger inverter. The house and start batteries would be combined using an Blue Sea ACR. If i set my regulator and battery charger to lead acid mode will my AGM start battery be compromised?

I haven't found any information on this particular setup. any insight would be appreciated. cheers

Yes, and if you set the charger to AGM the house bank will fail! Forget the combiner and get a second charger just for the start batt.
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Old 13-06-2018, 10:16   #15
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Re: Lead acid for house AGM for start

My system is exactly what you propose. Four 6v. flooded lead acid batteries for the house bank divided into two 12v parcels giving a total of about 440 ah and a group 31 AGM for the starter battery. The flooded batteries are connected to the "1-2- both" switch and usually live in the " both" position for all functions...house and start.

The AGM is separate but can be paralleled in with a manual on/off switch.
The house bank is normally maintained with a 140 watt solar panel and the engine alternator is a 115a with internal regulator. If motoring for a few hours somewhere or if I'm on the boat for a day or so I parallel the start battery to the house bank to bring it up to full charge, but normally the start battery is out of the system and just waiting in reserve. This works fine as the AGM holds a charge for a good while and only occasionally needs a boost. No need for a fancy splitter or voltage sensing relay.

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