catamaran battery banks house vs engines

[farmer.leo]

Layout currently is four "dual purpose deep cycle" 110ah batteries: two for house, and one as starting battery for each 3YM30 Yanmar.

Would a 3 battery house bank, and shared starting battery with separate 1,2,both,none switches for each engine be better?

The engines are never started at exactly the same time. The starter batteries have never run out. The house bank is always worked hard on trips greater than a weekend, and they have worn out twice already. We're adding solar and upgrading from a diode based combiner to voltage controlled relay for better charging. But now I'm thinking a dedicated larger house bank would make for more efficient charging and capacity without a lot of fuss. Yes, some redundancy would be lost as far as the starting battery.

 

[jac]

The only issue would be with the length of cable run from battery to starter / alternator but if that is adequately sized it should be fine.

If domestic battery bank is struggling though, you really need to look at the charge / discharge side as a priority as it may be that you are barely putting in enough to cope with demand. If that is the case, look for power saving and additional generator capacity. A cat should be a good candidate for lots of solar which may give you a useful boost.

 

[Tranona]

Change the engine start batteries to dedicated AGMs such as Red Flash which can be mounted close to the engines and this will probably free up space for a larger house bank. Not a good idea to have one battery for both engines as one of the benefits of two engines is that they can potentially be used independently.

 

[jac]

Change the engine start batteries to dedicated AGMs such as Red Flash which can be mounted close to the engines and this will probably free up space for a larger house bank. Not a good idea to have one battery for both engines as one of the benefits of two engines is that they can potentially be used independently.

Whilst that is true, if he has dual purpose (presumably leisure ) batteries then they should be ok for starting the engine if the engine start battery is flat.

 

[Tranona]

Whilst that is true, if he has dual purpose (presumably leisure ) batteries then they should be ok for starting the engine if the engine start battery is flat.

But that will need a means of paralleling the house bank to both the engines if he wants to start both in an emergency.

Much better to keep engine starts independent and replace (once they are knackered) the house batteries with true deep cycle.

 

[vyv_cox]

I have exactly what Tranona suggests, but only x1, not x2. Three domestic batteries in a bank replacing two. In practice I rarely bother to change to the starter battery, just use the domestics. The power of 3 x 110 Ah batteries is considerably more than a little engine needs, even first thing in the morning when their charge is lower. I start on the Red Flash about once per week to boost its charge and check that it is working OK.

 

[RichardS]

I like the simplicity of my cat which has an starter battery for each engine and 3 200Ah house batteries. Each alternator then charges it's own starter battery independently and jointly charges the house batteries via a simple solenoid.

No 1-2-Both switches, no VSRs, simple wiring and it's failsafe as both engines are entirely independent and either or both can charge the house batteries.

Might be a set up worth considering if you intend to make changes.

Richard

 

[William_H]

As said it may be more convenient and certainly shorter cable runs to have an engine battery for each engine. However one engine battery should suffice. Buy typical car battery for engine start. (cheapest) Then connect the deep cycle batteries to increase your house capacity. You need to check actual charge voltage on the batteries after a decent run to confirm that the diode set up is indeed limiting charge voltage. You should get 14.1 or so volts at all batteries for a good charging set up.
You should not need bigger alternators with 2 working for you. Dual VSR from each engine battery to the house battery should work well.
You will need to connect all negatives together with heavy cable then by switching or even a jumper cable arrange that you can emergency start each engine from the house batteries. olewill