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Old 18-04-2019, 15:39   #1
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Care and feeding of battery banks

This is how Sea Biscuit came to me:

2 x 12V paralleled start bank 12V sealed lead acid batteries, Century NS70M MF, CCA: 680 (call this “Start" or "bank 1").

4 x 6V 240aH gel batteries, NPG240-6, 240 AH, two pairs in series paralleled to produce 12V; call these “House" or "bank 2".

2 x 200W solar panels, wired to a Manson SBC-7130 charge controller. The Manson presently charges the house bank.

Perkins 6.2544 engine; its alternator (Motorola Marine, 70 amp.) charges the start bank.

Four position 1-2-BOTH-OFF switch fitted.

My question: what is the best way to satisfy the differing charging requirements of these batteries? The manufacturer of the gel batteries today told me that their bulk charge is 14.1V, and their float charge is 13.6V.

The start batteries require 14.7V for their bulk charge, and 13.5 for float.

I am happy to buy a second charge controller for either battery bank and set bulk and float levels to suit the bank it's connected to.

What are the gurus' suggestions for the optimum charging regimes for these battery banks? And I am open to rewiring suggestions, too, if the current setup is not optimal.

At present, I have been using the BOTH position to charge both banks via the solar panels while I am on board and can monitor. I have been doing this once a week, and turning OFF once the shared voltage of both banks reaches 14.3V (the highest the connected volt meter shows). I am sure this approach is under-charging the start bank, so all suggestions gratefully received.
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Old 18-04-2019, 15:53   #2
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Re: Care and feeding of battery banks

You can do it with a Blue seas ARC but if you want more control over the charge profile a Balmar Duo is fully adjustable (other makes as well , Victron, Sterling do similar I think). You really should wire the alternator to the house bank and eliminate having to use your battery switch for charge direction.
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Old 18-04-2019, 15:55   #3
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Re: Care and feeding of battery banks

Have a read on the below link. This is generally accepted (more or less) as the optimal set up.

https://marinehowto.com/
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Old 18-04-2019, 17:57   #4
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Re: Care and feeding of battery banks

Thanks rbk; that is a most comprehensive site. Can you name a few of the most important articles there, or are you suggesting I read the entire site? And thanks for the tip re. wiring the alternator to the House bank, too.
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Old 18-04-2019, 18:49   #5
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Re: Care and feeding of battery banks

Not really (on my phone, broken hand) you really need to read up on the alternator, electrical and solar sections. Some are long but shouldn’t take more than an hour. You need to get the whole picture really, and if you’re considering or requiring some rewiring learn how to do proper crimps with proper tools and materials. I would recommend starting with the ARC article then the programming balmar external voltage regulator even if you don’t have one. It will help you understand charging profiles and why they are required.
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Old 18-04-2019, 19:51   #6
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Re: Care and feeding of battery banks

Thanks rbk.

On reading the "Making Sense of Automatic Charging Relays" article, I can see an ACR will not be the right choice for me, as the required bulk charging voltages are greater than the 0.3V he mentions:

Quote:
Once we get beyond about a 0.3V difference, it starts to make more sense to move to a DC to DC charger such as a Sterling Power Battery to Battery Charger where we can get a true fully independent smart charge profile.
I will read up on the Balcar Duo in the meantime, and explore DC to DC chargers.
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Old 18-04-2019, 21:33   #7
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Re: Care and feeding of battery banks

Quote:
Originally Posted by Kit_L View Post
Thanks rbk.

On reading the "Making Sense of Automatic Charging Relays" article, I can see an ACR will not be the right choice for me, as the required bulk charging voltages are greater than the 0.3V he mentions:



I will read up on the Balcar Duo in the meantime, and explore DC to DC chargers.
Hi, I would suggest that the DC to DC charger would be the easier solution, with alt going to the bank requiring the higher charge voltage.
Some on here would have you rewiring the entire system in order to meet their beliefs.
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Old 18-04-2019, 22:00   #8
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Re: Care and feeding of battery banks

Quote:
Originally Posted by Kit_L View Post
This is how Sea Biscuit came to me:

2 x 12V paralleled start bank 12V sealed lead acid batteries, Century NS70M MF, CCA: 680 (call this “Start" or "bank 1").

4 x 6V 240aH gel batteries, NPG240-6, 240 AH, two pairs in series paralleled to produce 12V; call these “House" or "bank 2".

2 x 200W solar panels, wired to a Manson SBC-7130 charge controller. The Manson presently charges the house bank.

Perkins 6.2544 engine; its alternator (Motorola Marine, 70 amp.) charges the start bank.

Four position 1-2-BOTH-OFF switch fitted.

My question: what is the best way to satisfy the differing charging requirements of these batteries? The manufacturer of the gel batteries today told me that their bulk charge is 14.1V, and their float charge is 13.6V.

The start batteries require 14.7V for their bulk charge, and 13.5 for float.

I am happy to buy a second charge controller for either battery bank and set bulk and float levels to suit the bank it's connected to.

What are the gurus' suggestions for the optimum charging regimes for these battery banks? And I am open to rewiring suggestions, too, if the current setup is not optimal.

At present, I have been using the BOTH position to charge both banks via the solar panels while I am on board and can monitor. I have been doing this once a week, and turning OFF once the shared voltage of both banks reaches 14.3V (the highest the connected volt meter shows). I am sure this approach is under-charging the start bank, so all suggestions gratefully received.
My set up is two 110 a/h 12 volt start batteries in parallel and six 235 a/h 6 volt batteries series/parallel house bank. Each bank is wired to two rotary 4 position switches as you have, the destination of one switch is the engine and the other switch is the house distribution bus bar. This enables connection of either load to either supply or both if needed.
190 watts of solar keeps everything topped up and working well.(a little more would be better ) Controller is a morningstar duocharge pwm (yes, I have been advised here that it is a POS ) but it just works well without any further input from me.
The boat lives on a swing mooring in Sydney and, for what it's worth, I have never had to use the both position on a switch. I also never switch off the solar, just let it do it's thing.
My suggestion would be to investigate the DC to DC charger options that can likewise be left to do it's thing with the existing charge controller, without having to resort to manual switching.
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Old 19-04-2019, 03:01   #9
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Re: Care and feeding of battery banks

Thanks Rob: very helpful. More to come as I make some measurements.
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Old 19-04-2019, 04:53   #10
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Re: Care and feeding of battery banks

Quote:
Originally Posted by Kit_L View Post
My question: what is the best way to satisfy the differing charging requirements of these batteries? The manufacturer of the gel batteries today told me that their bulk charge is 14.1V, and their float charge is 13.6V.

The start batteries require 14.7V for their bulk charge, and 13.5 for float.

I am happy to buy a second charge controller for either battery bank and set bulk and float levels to suit the bank it's connected to.

What are the gurus' suggestions for the optimum charging regimes for these battery banks? And I am open to rewiring suggestions, too, if the current setup is not optimal.

Long term, one option might be to migrate both banks toward the same battery manufacturer, same charging profiles, and then insert a programmable charger into the system (where the user selects specific voltages).

Not a recommendation, just an observation.

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Old 19-04-2019, 12:17   #11
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Re: Care and feeding of battery banks

Kit, while you're investigating Maine Sail's website, you may be interested in this one, too


Electrical Systems 101


Unless you know how your boat is wired, assuming B on the 1-2-B switch does what you think it "should" may not be correct.


First thing to do on a new to you boat is trace the wiring.


Good luck.
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Old 19-04-2019, 12:31   #12
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Re: Care and feeding of battery banks

Quote:
Originally Posted by rbk View Post
You really should wire the alternator to the house bank and eliminate having to use your battery switch for charge direction.
Some of us see value in running the alternator output through the battery selector switch. This allows me to direct all of the alt output to whichever bank I see fit. If the engine is running and I want the fastest possible charge to go to the starting battery, in the event that it is really low, I can do so.

Yes, there are automatic balancers, etc to share the output and protect the starting battery from getting low, but I really like to be in charge, pun intended.
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Old 19-04-2019, 13:22   #13
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Re: Care and feeding of battery banks

Quote:
Originally Posted by wingssail View Post
Some of us see value in running the alternator output through the battery selector switch. This allows me to direct all of the alt output to whichever bank I see fit. If the engine is running and I want the fastest possible charge to go to the starting battery, in the event that it is really low, I can do so.

Yes, there are automatic balancers, etc to share the output and protect the starting battery from getting low, but I really like to be in charge, pun intended.
Until someone switches it to off and you fry your alt diodes, or forget to switch back to your house bank and you’ve been running the refer all day. Lots of reasons for both. I monitor my banks religiously and am capable of making the same switch just as easy if required.
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Old 20-04-2019, 13:51   #14
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Re: Care and feeding of battery banks

Stu J. wrote:

Quote:
First thing to do on a new to you boat is trace the wiring.
Is there a recognised, "start here then go there" method to doing this? I would very much like to pursue this. All the wiring in Sea Biscuit is accessible; I have a multimeter and a clamp meter, but little experience in using them. Very willing to learn, however!
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Old 20-04-2019, 14:59   #15
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Re: Care and feeding of battery banks

Quote:
Originally Posted by Kit_L View Post
Stu J. wrote:



Is there a recognised, "start here then go there" method to doing this? I would very much like to pursue this. All the wiring in Sea Biscuit is accessible; I have a multimeter and a clamp meter, but little experience in using them. Very willing to learn, however!



Get a copy of Nigel Calder's Boatowner’s Mechanical and Electrical Manual.
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