Two banks, three batteries and new charger capable of charging three battery banks

[captcoho]

Old subject with many posts and threads. But the manufacturer does not provide any information. The #1 start battery is not a concern, the #2 house bank is two parallel group 31 with 210 Ah RC each for a total of 420 Ah. The manufacturer does spec a 120 - 300 Ah RC max per bank.
The question is, can a lead go to each battery even though the two batteries in the house bank connected in parallel?
Back in the day some older units actually showed this as a viable configuration. A larger unit with more Amperage would allow for a larger recommended Ah battery capacity, however the real-estate to mount a larger unit is a complete non-starter.

 

[Don S/V ILLusion]

No reason to connect to both batteries which are already connected in parallel. It serves no purpose.

Think of a battery as a combination of 6 individual cells housed in a common box, each cell produces +/- 2 volts (in series) to which you connect a charger. When you connect another battery (consisting of 6 cells) in parallel making a total of 12.
For the same reason we don’t need 12 separate charger connection, we don’t need more than 1 in your application. Your 2 battery bank is essentially one big battery.

 

[sail sfbay]

Is this what you are looking for? Victron Multi Plus 120A 3000 watt charger/inverter with Digital Multi Control (DMC) GX for Multi-Plus and Quattro 200/200A GX charger controller and BMV-602S digital battery monitor connected to 1-12V group 24 starting battery and 2-12v 201amp-hr house batteries. The multiplus inverter/charger does take up some space (under the navigation station seat in my case).

 

[Ron20324]

No reason to connect to both batteries which are already connected in parallel. It serves no purpose. Think of a battery as a combination of 6 individual cells housed in a common box, each cell produces +/- 2 volts (in series) to which you connect a charger. When you connect another battery (consisting of 6 cells) in parallel making a total of 12. For the same reason we don’t need 12 separate charger connection, we don’t need more than 1 in your application. Your 2 battery bank is essentially one big battery.

Agree with Don, but also agree with the OP if the question is CAN YOU / MAY YOU do it his way. I read that as he needs another battery post to connect other wires to. ???

 

[Benny17441]

Don't see why not. You could also join two sets of leads and connect them to the bank terminals or just connect one set of leads and leave the others off. What is the size of that battery charger? Usually a charger will divide their output among the connected leads according to the needs of each connected bank. Just one set of leads should be able to deliver the full output of the charger to a single bank. The question is the size of the charger adequate for your 420 Ah battery bank and when the starting battery may be also demanding charge.

 

[Davidasailor26]

What is the make and model of the charger? Like Benny said the individual charger outputs are usually each capable of providing the full output (it’ll just reduce the output to the others) so there should be no need to connect both outputs to one bank.

 

[Maine Sail]

What model charger? Reserve and Ah are not the same. There is no such thing as a 220Ah G-31 battery. The largest G-31 is about 130Ah, most are about 100 - 110Ah....

 

[captcoho]

What model charger? Reserve and Ah are not the same. There is no such thing as a 220Ah G-31 battery. The largest G-31 is about 130Ah, most are about 100 - 110Ah....

The charger is a Victron Centaur 12/30 which according to the spec sheet, Recommended Battery Capacity(Ah) is 120 - 300 which I would assume to mean per each bank.
These are Interstate SRM - 31 which the web-site indicates

SRM-31

31DC

CCA 675

CA 845

RC 210 min @ 25a

 

[Bob S]

Looks to me they are 98 ah batteries giving you 196ah house. That's about what I had in my C30. My frig never worked well so it was more of an icebox. Never had issues with the set up.

 

[captcoho]

Is this what you are looking for? Victron Multi Plus 120A 3000 watt charger/inverter with Digital Multi Control (DMC) GX for Multi-Plus and Quattro 200/200A GX charger controller and BMV-602S digital battery monitor connected to 1-12V group 24 starting battery and 2-12v 201amp-hr house batteries. The multiplus inverter/charger does take up some space (under the navigation station seat in my case).
View attachment 183885

That is absolutely the ideal set up. However, there is little room to install and the owner wants a Cadillac for the price of a Yugo, and had already ordered the unit. Only asking the question of if the size would fit before asking any other questions.

 

[Davidasailor26]

The charger is a Victron Centaur 12/30 which according to the spec sheet, Recommended Battery Capacity(Ah) is 120 - 300 which I would assume to mean per each bank.
These are Interstate SRM - 31 which the web-site indicates

SRM-31

31DC

CCA 675

CA 845

RC 210 min @ 25a

You should be fine. Like Bob S said, that’s 196 amp hours being charged by a 30 amp charger, which isn’t bad. The charger manual states “The full charging current of this Charger is divided in three main outputs but any one output can supply 100% of power if that is the only battery connected.” So You can just use one output to charge the house bank, and the other for the starter bank.

 

[sail sfbay]

..........Only asking the question of if the size would fit before asking any other questions.

Dimensions are: 14.3x10.2x8.6 inch............datasheet attached.

 

[Bobalong]

Connect charger output to each battery or just to one?

Read an interesting paper about connecting batteries so each is satisfying the load equally. They tested 3 parallel configurations, measuring amps flowing between batteries. The configs were how load(+) and ground(-) attached to the bank. A) Load and ground on first bat, B)Load on 1st bat, ground on last, C) Load to a block connecting all pos, ground to a block connecting all negs.
Config C drew power equally. Config A beat the heck out of first bat, the others supplied as little as 25% of 1st bat in string. Presumably results due to internal resistances. Obviously, once load off, the bank equalizes with some energy wasted as heat.

It could be the same situation with charging. Paper ignored charging. However with a 2 bat bank connected as config B or C its probably moot.

Other than that consideration, either way works.

 

[captcoho]

Thanks to everyone who responded. Thanks Bobalong... that was some of the immediate thinking if each output needed to supply part of the current required, and if the charger indeed had the ability to supply the added demand.
Understanding that electrically positive is positive in the parallel situation, but if each output is capable to supply all the demand, or if two outputs would need to be paralleled as well.

 

[Benny17441]

845 cranking amps? Are those starter batteries? Deep Cycle batteries for House use are usually rated in Ah (Ampere hours).