Battery to Battery charging

Considering the price a Volta sensitive relay looks better and cheaper. Not sure where this might be an advantage, except a trolling motor. I saw a Mini Kota device similar to this at West Marine (12 to 12 volt)--on sale for $30--had been considerably more--was rated at 10 amps.
 
Seems to me that you have a limited amount of charging capability from the charging source, in our case our outboards. This unit takes or uses amperage that the motor was designed to provide to a single starting battery. I think this would work if you cruised for extended times and did not draw any power for other systems.

I think I would like to change the battery switch and have a good battery charger on board.

Looks like someone is trying to sell a perpetual motion device to me.
 
You guys missed the point a bit.

This unit is not a simple one or two-way relay passing amperage from your outboard to a second bank. That is fine and accomplishes the task of sharing running charge capability with a second bank of batteries without requiring a user to do the switching to manage where they want the power and when. But it helps you much less at the dock normally requiring you to have another AC charge distribution system of sorts (multi-bank charger) ready for your shore charging needs.

This unit is an actual smart multi-stage charger that intelligently uses a starting battery or bank as a power source to charge another bank for other uses down the line. It has the ability to charge that second bank at a different voltage which has an advantage for trolling motor setups as Bob noted but also can be set for a different chemistry than the starting battery as well as charge a second bank of a different size more effectively than can be done with a simple relay.

Another point to consider is charging from shore power. All of the same principles apply to this device allowing both banks to charge effectively from one simple single bank charger attached to the starting battery allowing the unit to manage transfer and multistage charging of the second bank down the line.

The cost of the unit would be significantly mitigated by the fact that you no longer need a two or three bank charger or multiple chargers wired up to handle your shore charging needs.

Two wires to the starting battery and two wires to the other bank is all this unit requires. Compare that to wiring a single or dual sense VSR unit plus a multibank/multistage charger to two banks and you get the picture.

How much shear amperage could you draw from a starting battery to pass on through this device to your second bank? How much do you need and how much does your motor put out or your shore charger put out? I would be hesitant to hook up a 100amp charger to a garden tractor battery to try and charge a connected bank of golf cart batteries but that isn't really how most of us are set up anyway.

Using a unit like this with twins would also require an installer to interconnect the two starting batteries but hey twins are always more work so you should be used to that.

300 bucks for the unit plus a simple single bank charger in a size to meet your needs and very little to wire them up. The price would be a wash compared to buying a VSR unit plus a quality multibank AC charger but the wiring for the latter is more complex.

You say you like simple and this is an option to stay simple.

Too late for Aurelia but I am positive I would have saved serious bucks in electrical components and plenty of time if I had known it existed.
 
Nope didn't miss the point at all--go back and read all of the literature. You have to have different units to charge different voltages.(BBW 1212, BBW1224, BBW 1226 etc. The primary battery has to be at least a potential of 13.3 volts, before this unit works. The other 12 v to 12 v charger I mentioned does most of the things which this one does, but is limited to 10 amps--which makes a lot of sense. You cannot draw unlimited power from a battery, nor put unlimited power into a battery.

You have to have the battery charger anyway--and this does not necessarily eliminate a 3 bank charger etc. Generally not a good idea to mix battery types etc. Cots of an ACR or VSR are not that much--and are very easy to wire in.

You could use it when charging one boat battery thru the vehicle charging circuit--as many of us are doing--some with a diode, some without already--for the cost of just a few dollars.

I just don't see it as being worth the money, especially in a C Dory. Now in my Caracal I have a 12 volt system for the engine/electronics and a 24 volt system for the trolling motor. There are several systems which change the 24 volt circuit from two 12 volt batteries in series to in parallel--and charge each battery at 12 volts and then combine them when the charging source is removed. I have also used such systems in boats where I had a 24 volt windlass.

This also ignores that many of the modern outboards now have dual charging circuits. As for twins--you hook up each starting battery to that engine. There are several different ways to easily handle the house bank/banks.
 
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