Series Combiner or ACR ?

[SV Demeter]

First stages of what will likely be a full rewire and Im focusing on the primary wiring. Namely batteries, circuit protection, battery switches, charging circuits. Basically everything up to the panel. I will have (6) group 31s for a house bank and (1) 4D for engine starting and windlass operation. I intend to charge the house bank directly from the alternator and am deciding how I want to charge the engine/windlass battery.

I am considering either a Digital Duo (Series combiner) or a decent sized Automatic Charging Relay. I like the simplicity of the relay but I also like the advantages of the digital duo.

Suggestions?

Also in the mix are a 2500watt inverter charger and a small Entec Generator.

Another possibility is a separate alternator for the engine/windlass battery. There are currently 2 alternators installed on the perkins 4-154. A 100amp balmar and an older motorola I believe 55amp that is not presently in service. I have considered the option of an entirely separate charging system for the engine start battery and the advantages of a second alternator but am still planning at this stage.

[Target9000]

We're also in what is the start of the complete rewire and just like you, my starting point is on the primary wiring. And also just like you, I've been wondering about ACR vs a digital duo type device ( I was looking at the Xantrex Echo Charge).

Some things I've read have said the echo charge specifically is a solid state DC charger which is more reliable than the ACR relay. Some people said that the ACR can fail, either locking open or in some cases welding shut! The advantage however seems to be that charge sources can be connected to either bank in the system.

I did read some worry about ACRs opening when one battery is shot and it causing a depletion of both banks, but I believe I've read that the ACR Blueseas makes has a low voltage lockout which will prevent operation if the batteries go under a certain voltage.

I'm interested in what other cruisers have picked and why. I'm leaning towards a newer style battery isolator switch (OFF/ON/COMBINE) vs what is in the boat now (1/2/ALL/OFF). Wiring all charging sources to the house bank and putting an echo charger off the house bank onto the starter battery. That seems to me to be one of the simplest systems.

And lord knows with me on board it better be dumb proof and reliable.

[djmarchand]

If you have a Freedom modified sinewave inverter/charger then using the built in Echo Charger is the easiest way to charge your starting/windlass battery. It is current limited to 15 amps so you only need to fuse protect the circuit on the receiving battery end and can use smaller guage wire.

But this only applies to Xantrex's MSW inverters. Their sine wave inverters, even though they say they have an echo charger, do not work the same way. Too much dumb software engineering got in the way of simplicity.

David

[SV Demeter]

I used an Echo charge on my last boat and was very happy with the set up but I only had 2 group 31s for a house bank and one group 27 for engine start. I was a little concerned about the 15amp limit on the Echo charge for a 4D that will likely see some usage when the windlass is run.

I have a Freedom Inverter Charger but it is a Freedom 25 and an older unit that I do not believe has a built in Echo Charge.

The boat is currently set up with a battery isolator to charge the 4D start battery but I do not like that set up at all.

[duncan_ellison]

SV Escape Plan,

Your Freedom 25 should have an echo charger - mine does. Look for a small plastic terminal block on the right hand side at the front.

Duncan
S/Y TALISA

[SV Demeter]

Thanks I'll take a look tonight! Still wondering about the 15amp limit though. Im thinking since this battery will see duty running the windlass that I probably want a series combiner with a higher amp rating? Digital Duo apparently can deliver up to 30amps or be used to control a solenoid type charging relay. I do not intend to mix battery chemistries and will be using AGMs but the Duo apparently would tolerate differing battery types when used as a standalone series combiner.

[CharlieJ]

Escape-You have hit the nail on the head re: charging limitation of the Digital Duo. I have designed and installed systems using both the Digital Duo and all the different models of the Blue Sea stable.
There are applications for both technologies. In your case, the starting battery may see an extended load when weighing anchor so the ACR is the better choice. I am especially partial to the new Blue Sea magnetic latching ACRs with a manual remote over-ride. See ML-Series Heavy Duty Automatic Charging Relay - PN 7622 - Blue Sea Systems

Charlie

[SV Demeter]

Charlie I like this a lot. Ive been spending a lot of time lately at the Blue Seas site and here, not getting much work done these days but thats what desk jobs are all about right?

One of the things I like about the Digital Duo and Echo Charge is their intelligence with respect to charging. The old on/off/all switches as you know are not the way to charge separate battery systems. I guess I could use a Digital Duo to control one of these ACRs but that would pretty much double the cost. Thinking I will probably go with the 7622 and not mix battery chemistries. Right now the 4D I have is a gel and its it very good shape. (Tested out at 90% of original) but I was planning on using AGMs in the house bank. I guess I could mix the two chemistries and shorten the life span of the gel, replacing it with a new AGM when its time or maybe just bit the bullet and get all the AGMS now.

[CharlieJ]

Escape-
Mixing battery chemistries is not a great idea but, with judicious choice of charging sources, you can adjust the charging algorithms to meet a happy, if not ideal, medium for different chemistries. Remember; life is a compromise.

Charlie

[btrayfors]

The combiner will work OK, as Charlie suggests.

A couple of other options:

1. Run the windlass from the house batteries. When you use it, you'll likely have the engine running anyway (with 100A alternator), but if not it's no big deal. Any healthy-sized house bank should be able to deal with the windlass draw. While the draw may be sizeable, it's for a relatively short time. Say, 75A average for 5 minutes total. That's only 6AH, so easy to replace.

The potential downside to this strategy is the possibility of introducing voltage spikes into sensitive electronics. This could be a problem without a proper protection device in-line, or without a separate power source for the electronics.

2. Use a separate battery up forward for the windlass. I've done this for 15 years, with two T-105's under my V-berth. These are charged with an Iota DLS-55/IQ4 when dockside or when the generator is running. Sometimes with a solar panel as well. Makes for very short cable runs. Also, makes for fairly quiet getaways under sail, as you don't need an engine running :-)

Bill

[goboatingnow]

In reality voltage spikes from dc motors cause no problems with modern electronics your electric fridge is just as likely to be the worst culprit

[btrayfors]

Originally Posted by goboatingnow

In reality voltage spikes from dc motors cause no problems with modern electronics your electric fridge is just as likely to be the worst culprit

Hmmm....that's twice now you've made that (very incorrect) claim. Could you please cite some credible evidence -- not anecdotes or declarations -- to support your claims that:

(a) spikes from DC motors and the like do not harm electronics; and
(b) spikes from DC motors do not cause cumulative damage to sensitive electronics?

Meanwhile, you might review this link re: safe wiring practices, as well as other credible sources dealing with voltage transients, their origins and effects.

Transients and Voltage Drops - Good and Bad Wiring Techniques for Electronics

Bill

[hellosailor]

EP-
"mix the two chemistries" Actually...if they are rated very similarly, onyl a few tenth's of a volt apart, sometimes you can cheat a bit. Bear in mind that by carefully using different cable diameters and lengths, you can intentionally create a voltage drop of .1-.4 volts in the charging circuit to one battery rather than the other. And that MAY be all it takes to balance the charging voltages, assuming you are only using one voltage sensor and it will be blind to the second battery anyway.

Cable is cheap enough so it may be worth running your numbers.

[djmarchand]

SV:

Don't worry about the 15 amp charging limit. If you use your windlass for 5 minutes at 60 amps you are consuming 10 amp hours. The Echo Charger will quickly replace that at a charging rate of 15 amps.

David

[SV Demeter]

Good point about the Echo Charge. Im leaning more towards the Digital Duo I think though as it is rated for 30 amps which should handle the demands on this battery. I cant imagine running the windlass for more than 5 minutes but even if it was 10 minutes, what am I looking at 15 amp hours? And the digital Duo will tolerate my gel starting battery AGM house bank mix. Thanks all.