I have been looking at adding a battery combiner for my one engine, two batteries with switch installed at the factory.

Thanks Al for the informative write-up and diagrams on the subject.

The two brand of combiners that regularly comes up for being reliable at a decent price are from Yandina and Blue Sea. I'm leaning towards the Yandina C100. Compared to Blue Sea's CL-Series BatteryLink (7600), it can handle 10 more continuous amps and uses less current closed or open. Comes with wires and can be had for 50$ compared to 67$. Anything else I should take into consideration?


This quote was made over a year ago. Was it in reference to West Marine (Yandina's) C50 combiner now discontinued?

I think your alternator outs 65 amps. Do you plan on upgrading to a more powerful alternator?

IMHO, max specs don't matter if you're not going to use them. If I were making the purchase, I would buy the part that I thought had the highest build quality and used the higher tolerance components. I do not know if tha tis the Yandina or Blue Sea in this case. But my point is to look at quality. IMHO, it doesn't matter by how much it exceeds your spec demands.

Also...is it possible to hook this up through a battery switch? I think I would want the ability to charge a single battery if the situation arose.

I emailed Yandina today to see if their C100 had the same extra features the more expensive Blue Sea 120Amp SI ACR (7610) had.
I received an answer within one hour:

Q1. Does it allows temporary isolation of house and starting batteries during engine cranking ?

A1. Under normal starting conditions yes, they are isolated. If the engine is started immediately after it has been running and the Combiner is still on, they are only partially isolated. In the case of a re-start you should wait about 25 seconds for the Combiner100 to release for full isolation. If you specifically need isolation on re-starts, the new model available later this year will have re-start isolation.

Q2. Does it provide an under voltage lockout something like will not close when the lower voltage battery is below about 10.8V?

A2. Yes, in the case of the secondary battery having a very low voltage, the Combiner will not just put the batteries in parallel when the one on charge gets up to voltage. It is designed to deliver about 1 Amp-hour every 20 to 30 seconds in an attempt to get the low battery up to a high enough voltage to be put in parallel. Depending on the size and charge level of the discharged battery, this process can go on for many minutes. If the battery is OK, that trickle of charge will get it up to a satisfactory level to be put in parallel without discharging the primary battery. If the second battery is faulty and won't accept a charge, then the Combiner100 will never put them in parallel and just let the primary battery continue to charge.

Now the Blue Sea 7610 can handle more power, 120 amp continuous. In return it takes more juice, 175ma closed and 15ma open.

Side note; Aldo Blue Sea calls them Automatic Voltage Relay's I think the electrical term is voltage sensitive relays.

New gas model Volvo's all come with 75 amps alternator. So all 3 of them would be in adequate for me.

Build quality vs value is what I'm trying to find out. Since you can't tell from pictures I'm relying on users experience. So far from searching the net, no one had a bad experience with either. Which comes down to price... why pay more?

I can't think of any reason why I would want to charge only one battery while boating? But if it happens I would just disconnect the combiner lead from one of the batteries.

I'm the idiot!

The normal way to connect a combiner is to hook one side of each to each side of the 1-Both-2 swich. When the engine runs, the voltage increases and closes the switch - effectively the same as putting the battery switch in the both position - albeit at a normally lower current capacity.

When this happens, the engine alternator charges both batteries regardless of whether the switch is in the 1 or 2 position. In fact, with a combiner, it is not necessary to put the switch in the both position (unless perhaps both batteries are needed to start the engine in an abnormal situation).

Then when the engine stops, the voltage lowers, and the combiner opens, effectively changing the switch back from the both position.

In other words, the effect of a combiner is to mimic moving the switch to the both position while the engine is running and back to the original position when it stops. This alleviates the need to remember to manually move the switch to both to charge both batteries, and manually move the switch back to keep one battery from discharging into the other.

Although I think the Yandina model may also have a remote capability (its been awhile since I have looked at them), some models of the Blue Sea combiner can turn the combiner manually on or off - for override purposes.

I prefer Blue Sea because I think they make good stuff, but there is no reason you would not have good luck with Yandina.

Young D-Rod is showing signs of growing up boys....

Shop around, I got the Blue Sea Systems 'Add a Battery' package - ACR and Switch for about $90 shipped. Although I hope to not have much use for the switch. Having said that I did not comparison shop Yadina. One thing about Blue Sea Systems, they have fantastic product support - I've called in several times to get techs opinions of this setup or that and they were always easy to reach, knowledgeable, and happy to help.

I have the Yandina and have had no problems with it in the last 1 1/2 years. I do not have a battery switch though, I have it wired directly to the starting and house batteries.

You cannot believe how small it is; smaller than a business card.

Yes, the Yandina can allow for a remote override switch to be connected to the remote wire id needed. Also has a feature to limit voltage to safe level for sealed AGM type batteries if your using an old charger or alternator that could charge higher than 14.2 volts.

Looks like both stand up company's with good product. Sounds like I can't go wrong with either one.

I'll get the Yandina simply for the very small advantages. Smaller, has built in wires, uses less amp when in use (150mA) and draws no current when close. Oh and shipping cross the border is cheaper.

Interesting company too. Check this out.


The boat even survived hurricane Hugo in 1989. Story and pics here.

Talk about living the dream. Running your own company from your 71' boat!

I had the Yandina C50 for three years for my second battery and hever had an issue with it. I recently upgraded to the C100 because I added a third battery and my alternator puts out 74amps max, so I wanted to make sure that everything was up to the task. I will probalby give the C50 to one of my friends when they put a second battery in their boat.

The point I guess is that I like the Yandina products, and they carry a lifetime waranty. I also like the fact that it already has wires hanging out and is very simple to install.

Hey PhatboyC, don't forget to post with plenty of pics when you get it installed!!

This will be one of my off season projects.

I installed a second battery using the Blue Sea Systems 'Add a Battery" package that includes the 7610 ACR. Fairly simple install.

Here's the switch and ACR wired together.


I mounted the 7610 facing inward to the engine compartment for a cleaner look.


I also obtained a ACR switch panel, that I haven't installed yet. It will go in with the dual battery charger. Apparently combiners and dual battery chargers don't play nice together. The ACR switch panel has a switch to disable the ACR, and is ignition protected.

Thanks for sharing the pics Jim_R. I installed the Yandina last week. There's not much to see but I'll take some pics too.