Battery bank charging

[glenn.225]

Looking for a little advice redoing my battery bank. My current bank is composed of one starting and one deep cycle battery, a off, 1, 2, both switch, 10 Amp Guest charger and a 60 amp alt on the diesel motor. The charger has two 5 Amp legs with one of each connected to either battery and the motor could be started from and will charge either depending on switch position. The starter battery is OK, but the Motormaster deep cycle is toast. Both batteries are located in a space below the sole in the upper portion of the keel. I have just bought two new Trojan T105's for my house bank. Since the existing battery box will only accommodate two batteries I will have to relocate the starting battery most likely behind the engine in under the cockpit, there is lots of space there. My next problem is how to charge the banks. My thought is to use position 1 for the start battery and it will charge off the engine alt and supply all power when motoring. Position 2 will be the house bank it will provide power when sailing or on the hook and it would be charged primarily by both legs of the Guest charger by shore power. Since my loads are fairly light, all LED lights, VHF, small stereo, sail instruments and tiller pilot the house bank should be good for a couple of days, usually the most I am out. If required I could charge either bank by either method by placing the switch in the “both” position. An amp meter may be in my future, but I want to keep costs down for now. Anyone see any issue with this?

[btrayfors]

Glenn.125,

The setup you describe will work OK, though it would be good to get some charge into the T-105's from that 60A alternator.

One way to do that would be to start the engine from the house batteries (position 2 on your switch) and let the alternator charge those batteries when the engine is running. You wouldn't have to do this every time you start the engine, and could still use the #1 position for starting/charging sometimes.

When you get a few bucks ahead, think about a simple device like the EchoCharge which would sit between your house and start batteries and automatically keep the start battery charged! Here's how you could wire it:



Bill

[djmarchand]

Bill is correct. And an Echo Charger is a nice addition although it does take some rewiring of the house loads to take advantage of it.

David

[glenn.225]

Yes had thought about Echo Charger or similar, have used various isolation controls on 12/24 volt systems. But I would like to keep it simple, a sort of less is more thing. I always have power at my slip so I just plug it in when I get back. If was out for awhile and needed to motor I could charge them then. I do have to reconfigure the cabling so I will be adding a fuse to the house side. Just wanted to see if I had over looked something.

Also they will get a good charge at home before I take them down to the boat. At the rate I'm going it might take me a week to get them installed, lots of little projects going on.

[Hotel L]

How many days between sails?

[Bash]

Originally Posted by glenn.225

Yes had thought about Echo Charger or similar, have used various isolation controls on 12/24 volt systems. But I would like to keep it simple, a sort of less is more thing.

There's nothing more simple than echo charging. Nor more idiot proof.

[Stu Jackson]

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com

[glenn.225]

Hotel L
Most weeks I get out 3 or 4 times. Although I'm a little slow this year we lifted in almost two ago and I have got out yet, maybe by Sunday.

Bash
I usually don't have much problem with switches but mistakes do happen and I use to call it making it "grunt-proof".

Stu Jackson
Lots to digest here and I have found Mainesail posts and site a fount of knowledge.

Compared to marine, automotive electrical is so simple. But I'm learning more all the time.

[onestepcsy37]

if you're day sailing or just overnighting, why not keep it real simple.

one battery bank with two golf cart batteries. no 1/2/both/off switches, no echo chargers, no double cabling.

[daddle]

I run all the charge devices to the house bank. The start battery is used only for starting. There is a 1-2-All-Off switch that is 'never' used for anything. A simple West Marine Battery Combiner relay box tops up the start battery.

Super simple. Reliable. However make sure the alternator sense wire, if any, is sensing the battery being charged.

[Andina Marie]

Originally Posted by djmarchand

Bill is correct. And an Echo Charger is a nice addition although it does take some rewiring of the house loads to take advantage of it.

David

Echo chargers have a 15 amp maximum. A Combiner100 or equivalent between the two batteries would make switching unnecessary and handle the full output of the alternator. Since it is bi-directional, when using a charger on the house bank it will top off the starting battery as needed.

[CharlieJ]

The Balmar Digital DuoCharge is limited to 30A and is intended to be placed between the house bank and the starting bank with uni-directional current flow.

The Xantrex Digital echo charge is limited to 15A and it is also intended to be placed between the house bank and the starting bank with uni-directional current flow.

Since the charging current is low, relatively small conductors, taking into account ampacity and voltage drop, can be used rather than the relatively large conductors required for battery combiners. Please note and understand the use of the word "relatively". :-)

These relatively low charging currents are well suited for re-charging a starting battery since, as has been repeatedly shown, a battery starting a reasonably maintained diesel engine will use just a very few amp-hrs per starting evolution.

Example: A large diesel engine requiring 700A for 5 seconds to start.
700A x 5 sec x 1/3600 hr/sec = 0.97Ahr.

[sailinglegend]

Originally Posted by Andina Marie

...A Combiner100 or equivalent between the two batteries would make switching unnecessary and handle the full output of the alternator.....

This is commercial advertising and shouldn't be allowed on this forum.

The Combiner can't follower the full output of the alternator because of the 6 gauge wire used which deliberately reduces the current to protect the relay contacts. Introducing resistance to a product just to protect the badly designed contacts is very bad engineering.

I quote from Yandina's website:

"The length and size of the leads supplied provide a resistance to high currents which protects the relay from welding its contacts together when it closes."

END QUOTE

The reduction in current means the batteries are really getting a trickle charge. They may eventually reach full charge, but after a much longer time.

If you want to trickle charger your starter battery from your service them the EchoCharge or Balmar are fine. The Balmar is smarter with the outputs adjustable to suit the slave unit. For example when there is 14.6 volts going in the output could be set to 14.1v. When the input is on float at 13.8 volts the output can be set to say 13.2 volts. It isn't a multi-stage regulator but a voltage follower - just like the much cheaper EchoCharge.

[Andina Marie]

Originally Posted by sailinglegend

This is commercial advertising and shouldn't be allowed on this forum.

The Combiner can't follower the full output of the alternator because of the 6 gauge wire used which deliberately reduces the current to protect the relay contacts. Introducing resistance to a product just to protect the badly designed contacts is very bad engineering.

I quote from Yandina's website:

"The length and size of the leads supplied provide a resistance to high currents which protects the relay from welding its contacts together when it closes."

END QUOTE

The reduction in current means the batteries are really getting a trickle charge. They may eventually reach full charge, but after a much longer time.

If you want to trickle charger your starter battery from your service them the EchoCharge or Balmar are fine. The Balmar is smarter with the outputs adjustable to suit the slave unit. For example when there is 14.6 volts going in the output could be set to 14.1v. When the input is on float at 13.8 volts the output can be set to say 13.2 volts. It isn't a multi-stage regulator but a voltage follower - just like the much cheaper EchoCharge.

Since others on this board frequently name competition products from other manufacturers the moderator(s) here said it is OK for me to have equal time. I don't give URL addresses or prices.

The Combiner with that specification can withstand inrush currents up to around 1,000 amps. The contacts tend to weld when you get to around 1250 amps. The 6 feet of 6 gauge cable adds 0.0024 ohms of resistance which equates to 0.24 volt drop at peak charging at 100 amps and ends up at a drop of 2.4 thousandths of a volt when you approach end of charge. That 0.0024 ohms, however, limits the current to less than the welding current when a battery at 12.0 volts is connected to one at 13 volts.

So yes, you are correct, I limits the 1000+ amp potential current to about 250 amps. It is not intended for charging at 1000 amps.

[colemj]

Originally Posted by Andina Marie

A Combiner100 or equivalent between the two batteries would make switching unnecessary and handle the full output of the alternator. Since it is bi-directional, when using a charger on the house bank it will top off the starting battery as needed.

Note that Andina was discussing VSR's in general and not pushing or discussing her product. I had to go back and reread her post to notice that she actually named her product - I had read it the first time in a general sense.

Doesn't seem commercial in any way to me.

Mark