Powering Electronics Through Starting Voltage Drop

[CaptTom]

Just wondering what others do about maintaining voltage to various electronic devices during engine start, when the voltage can drop below whatever minimum sustains the device, causing it to fail and restart.

I've seen this with chartplotters, radios and other helm electronics. I currently have this problem with my inverter/charger control panel. Looking ahead, I'd like to add more "smart" devices such as a Raspberry Pi and no doubt these will have the same problem.

I can think of a few workarounds, but wanted to hear what others are doing before I go down an unnecessarily complicated path.

The simplest option, running all electronic systems off the house bank and having a dedicated starting bank, isn't ideal for me because I have two engines, one set to start off (and charge) each bank. It's not convenient to go down into the engine room and manipulate the switches before and after each engine start.

[rslifkin]

Personally, I went with the everything runs off the house bank approach. In my case, I have 3 banks. Start 1, start 2, house. 2 engines and a generator, each with the ability to select either start bank. So normally the port engine uses start 1, stbd and gen use start 2. In my case, start 1 and 2 are each a single group 27, house is a pair of L16 6 volts in series.

Charging in my setup is handled with 2 ACRs, 1 for each engine. Alternators feed to the start banks, ACRs send that power to the house bank once voltage comes up. I've got the ACRs interlocked to the engine ignitions so they only operate with engines running, charging stays independent on shore power or generator (house bank is charged by the inverter and there's a separate charger for the start banks).

To avoid adding another battery bank, you could start everything off a single start bank, but include the ability to switch and start from the house bank if something happens to the start bank.

Realistically, it's simpler to just power the electronics from a battery that doesn't start an engine than to try to keep power to them through the voltage dip.

[Joh.Ghurt]

That seems only a problem for small boats without separated house batteries.
If it annoys you, look at this solution:
https://forum.allaboutcircuits.com/t...e-drop.174073/

[ranger58sb]

I just (mostly) momentarily turned off all the electronics while starting the engine.

When I remembered... but which was most of the time...

Electronics restart only took a minute or a bit more...

Part of this was dictated by our boat's basic DC architecture: two battery banks, each started an engine but also each serviced approx half of the house loads. So one of those also serviced our bridge electronics. Very common set-up in powerboats like ours. Easy enough to work around.

-Chris

[rslifkin]

Originally Posted by ranger42c

I just (mostly) momentarily turned off all the electronics while starting the engine.

When I remembered... but which was most of the time...

Electronics restart only took a minute or a bit more...

Part of this was dictated by our boat's basic DC architecture: two battery banks, each started an engine but also each serviced approx half of the house loads. So one of those also serviced our bridge electronics. Very common set-up in powerboats like ours. Easy enough to work around.

-Chris

That was the original setup on my boat before some re-wiring. Personally, I hated it. Too easy to accidentally drain starting power, everything would power cycle on engine start, etc. Much nicer to just down-size the start batteries a bit, add a house bank and move the panel feeds (plus a few other adjustments). IIRC, my father and I got the whole project done in a weekend a few years ago.

[Lake-Effect]

Originally Posted by CaptTom

The simplest option, running all electronic systems off the house bank and having a dedicated starting bank, isn't ideal for me because I have two engines, one set to start off (and charge) each bank. It's not convenient to go down into the engine room and manipulate the switches before and after each engine start.

The answer is isolation in some form: if not separate start batteries, then maybe a separate battery to power the electronics you want to hold up. It could be a single battery connected to the selected house bank by an ACR or some other form of relay that disconnects from the house bank when the starter(s) are used.

I haven't yet seen or done this myself, just exploring ideas.

[Rucksta]

Remove the rotary switch and replace with three isolation switches.
Wire you house feed to switch #1
Wire engine to switch #3
Switch #2 is the interlink between the banks.

Normal operation is #1 & #3 on #2 off

Alternator feed to the starting bank.

Add complexity with one way ACR from engine bank to house.

[valhalla360]

You could rig up a remote switch so they can be disconnected/connected at the helm.

But really, it's not a big issue. It's not like a car where you hit the ignition and have the car in gear within 5 sec. Either at anchor or dock, you start the engine and then either start pulling the anchor or unhooking the lines. By the time that's done and you are ready to pull away, electronics are back online.

If you wanted to keep it simple, a cheap ridding mower battery mounted at the helm with a switch should be able to cover a few minutes on startup.

[lorenzoj]

I have a dedicated power bus for the electronics. This bus is fed through diodes from all three sources. (both starting banks and the house bank) Power is automatically taken from the source with the higher voltage. Been this way for over 20 years with no issues.

[Sailor George]

I just installed a n ew Statndard Horizon VHF radio with the Ram4 mic at the helm. Old boat with two new batteries running through a three way switch. So there is no dedicated house or start battery. When I start the engine the Ram4 mic shuts off but the main vhf unit in the cabin does not. It stays off until I turn it on at the helm station.

My concern is I will forget to turn it on before I need it for an emergency! I start the boat at the dock on both batteries, run it on both batteries, then shut the engine down and set the switch to number one or two depending on if it’s an even or odd day on the calendar day we are on sailing on. We are generally day sailing, so the battery that is being drain has enough power to start the engine but the helm mic drops out. I have also tried and switched to the reserve battery to start the engine with the same results. Called Standard Horizon and they have no idea what’s causing it other than low voltage. The battery voltage before I started the engine was 12.5 volts.

Any ideas would be appreciated. Thanks George

[bcboomer]

Check out the Blue Sea ACR wiring diagrams. I'm pretty sure there is a solution using them as they have a built in isolation circuit and can be manually controlled.

[oleman]

The simplest solution is a buck-boast DC-DC Inverter for a few hundred watts of isolated power to run the emergency systems. With a wide range on input voltages the Buck-Boast inverter gives a constant output voltage. In Boast mode it will increase the input voltage producing a higher output than input. The magic of a properly designed DC-DC inverter!

[waterman46]

Originally Posted by lorenzoj

I have a dedicated power bus for the electronics. This bus is fed through diodes from all three sources. (both starting banks and the house bank) Power is automatically taken from the source with the higher voltage. Been this way for over 20 years with no issues.

Right! Absolutely the best solution I see in all these posts, for the OP's situation, and as long as he will start only one engine at a time. The OP will have only two batteries, no house, but the principle is the same.

So many of others recommended solutions which would momentarily shut down all electronics. This would be exceedingly dumb IMHO. What if you are sailing along and suddenly see the need to do an emergency engine start - like ship heading at you, or about to run aground or anything else God Forbid MOB! You want your electronics to be available right now, you don't have time for reboots.

[Squanderbucks]

I have a Newmar StartGuard. A small rechargeable battery like for a home security system that acts as a surge preventer when you crank your engine.
I've had mine for years and it does very well. Hooked inline between the power cable and the sub-panel that feeds all the electronics to the bridge.
Available in places such as Defender. Easy setup and costs less than $200.00.

[smac999]

why are you starting the boat from the same battery as the electronics?...