Radar Antenna Stops when Starting Engine - Normal?

[Northeaster]

My newly installed Raymarine 18" Rayome antenna (with C80 display) seems to be working fine, except for 2 scenarios:

1. When I start the engine, the radar antenna stops working. I assume this is because of the large current draw starting the engine. I thne have to wait a coupleof minutes, until it comes back into standby mode, then press TX.
Is this normal??

2. When I run my pressur water pump, the same thing happens. I assume this is again because of the large current draw. However, I am thinking this may be correctable, with a larger, or separate cable from the battery switch to the DC panel, as the original looks undersized.
Thoughts?

[Strygaldwir]

Raymarine gear (Radar and autopilot at least) does reset when a low voltage condition occurs. This is at something like 10 volts for the 12 volt gear. I wrestled with this problem for many months until I finally found a cooroded connection to the drive unit of the autopilot. I replaced the lead to the drive with a a slightly larger AWG cable and I have not had an issue since. That is to say, except for today when I run my windlass with the radar on. I reset again. (But, this is a known issue with my batteries needing to be replaced. When are those Surrette AGM's going to be released?)

[David M]

Lots of electronics go offline when the voltage reaches a specific minimum. This saves both the electrical device and helps preserve the battery charge level.

There are a number of possible reasons for a large voltage drop when starting an engine. Your battery may be getting old. Your battery cable may be under gauged. You may have a loose or corroded electrical connection somewhere. Your battery may not be getting fully charged. You may need a larger battery. There are other less likely possibilities but I would check those first.

[Northeaster]

David - Thanks for running by some of the options. a few notes:

- It does it both when running on batt 1 (one group 24, 2 years old) or batt 2 (two group 27s new last year)
- Both banks were charged at the time.
- battery 1 cable is new, connections are new / good.
- battery 2 bank has new cables between batteries, main cable to selector switch is older, but connections are good.
- all battery cables are large cables (don't know guage off hand, but are very thick)


I guess part of my questions is: Is there necessarily something wrong?? Or is it normal for the amount of current drawn by the engine to interupt the radar, and cause a reset.

re: the pressure water pump; I monitored the voltage to my radar, before starting the water pump, and it was over 13 volts (as I was plugged into AC/ shore charger). When I ran the water pump, the voltage to the radar dropped to about 10 volts. As mentioned earlier, both the water pump and the radar are fed from the DC panel (which seems to have a rather small feed from the DC panel - looks like about 14 ga, where most of the individual circuits are 16 ga, for example).

[btrayfors]

Engine starting should have NO impact whatsoever on voltage to the radar, unless you are powering the radar from the starting battery.

If the pressure water pump is causing a problem, it's likely because of undersized wire to the panel and the radar and/or poor or corroded connections.

Bill

[Northeaster]

Bill - thanks for the reply!

I agree with you, about the undersized DC feed to the panel, for the water pump, and radar, etc.

In regards to the radar / engine starting, correct me if I am wrong, but..

Let's say I am sailing along, with my battery switch on battert 2 (house bank), powering all DC circuits, including radar.

Now, I want to start the engine. I can leave the battery switch on batt 2 (house bank), as I often do. This will start the engine from battery 2 bank- the same bank which is feeding the DC panel / radar.

Or, I could switch the battery switch to battery 1 (start battery), but this would switch my DC feed, including radar to battery 1 as well, and therefore the engine would still be started with the same battery, as is feeding the DC panel / radar.

Any further input would be appreciated!

PS. I don't always use the start battery (batt 1) for starting, but have them separated so that it does not get drawn down too low, if I run too many things off of my house bank at anchor, etc.

[scotte]

I had a similar problem due to a corroded ground cable to one engine. When I'd start that engine (but not the other one), my chartplotter would shut down, even though they are on different battery banks. After replacing the cable, it hasn't done it since.

[Beausoleil]

You could rid of the 1-2-Both-Off switch. Dedicate the house battery to the house panel, the starting battery to the engine starter, wire the alternator to the house bank, and use something like a Echo-Charge to charge the starting battery once the house bank is full. You'd be surprised how little you draw from the starting battery versus the house bank over the course of a typical day on the water. West Marine's website has a nice diagram, as do many other sites.

And you could install an emergency on-off battery switch between the house and start banks just in case the starting battery dies.

I agree with Bill - it's probably undersized wiring to your main panel, or corrosion somewhere...

[Northeaster]

Scotte - I will check the engine gound cable, to make sure it's tight / not corroded. I had it off last year, when i removed the engine to clean and paint it, and the engine compartment.

Beau - I agree that the eco-charge type arrangement may be the best way to go, but I don't want to reinvent the wheel. It has worked fine the way it is, with the off, 1, all, 2 battery switch, except for this current problem.

I charge the starting battery with the alternator (65 amp) while motoring ( it maye never be really topped off, but has never failed to start / been drained low)
I charge the house bank (batt 2) with the alternator as well, if I will be away from the dock for a couple of days. Otherwise, I have an Iota 45amp 3 stage smart charger connected directly to the house bank when plugged into AC, at the dock. I don't leave it plugged in 24/7, as I don't have a fridge, and do not have a Galvanic isolator (yet). I just connect to the shore power for a few hours, to charge the house bank and heat some hot water.

Thanks for the replies so far!

[btrayfors]

Beausoleil's right. Think about rearranging your system to take advantage of having your house and start battery banks truly separated.

He's also right about the start battery....it takes VERY LITTLE AH to start an engine (lots of amps, but only for a few seconds...total AH draw is miniscule). Usually this energy is replaced in MINUTES after starting the engine. The alternator is then idle for the rest of your trip unless it's connected to the house bank or a substantial load.

Why should you care? Because with a proper setup:
(1) your batteries will last longer;
(2) you won't have to worry about which position the switch is in; and
(3) you won't have to worry about low voltage cutouts when you start the engine.

Meanwhile, larger wiring to the panel could help a bit...it ought to be done, anyway.

Good luck,

Bill

[CharlieJ]

Northeaster-A fairly straightforward solution for your problem, is to install an automatic charge relay (ACR) in place of the 1-2-Both-Off switch. The Blue Sea 7610 and their new latching ML both have the ability to open and isolate the house from the start when the starting circuit is energized. Thus the starting battery absorbs the voltage droop and the house battery remains solid. Your electronics won't even blink. The actuation is nearly instantaneous, and operates with no operator intervention.

SI Series: SI-Series Automatic Charging Relay - Blue Sea Systems
ML Series: ML-Series Heavy Duty Automatic Charging Relays (Magnetic Latch) - Blue Sea Systems

[Northeaster]

Bill (or anyone). I realize that having separation would be better, but I am at a dock 90% time, where my Iota charger is wired to the house bank, and can be well charged.

In my case I am not sure if the cost, and work in rewiring, would be worth it to properly charge my start battery. I could likely replace it a coupleof times in the next few years, at a lesser cost, not that I plan to do that.

Before I go any further, could someone clear up my question above:

"In regards to the radar / engine starting, correct me if I am wrong, but..

Let's say I am sailing along, with my battery switch on battert 2 (house bank), powering all DC circuits, including radar.

Now, I want to start the engine. I can leave the battery switch on batt 2 (house bank), as I often do. This will start the engine from battery 2 bank- the same bank which is feeding the DC panel / radar.

Or, I could switch the battery switch to battery 1 (start battery), but this would switch my DC feed, including radar to battery 1 as well, and therefore the engine would still be started with the same battery, as is feeding the DC panel / radar."




Bill, you mentioned that my alternator is not being used, as you believed it to be wired to the start battery. I believe this is incorrect. I believe that my alternator is wired to the common post of th battery selector switch, so would it not charge whatever bank it is on, while the engine is running?

I would appreciate if someone could make this clearer for me!!

[Northeaster]

Charlie- thanks. Will look at the links you provided!!

[btrayfors]

Yes, if the alternator is wired to the common post on your 1-2-Both-Off switch, then it will charge whichever battery (or batteries) are selected by the switch.

[Northeaster]

Charlie (or anyone) - I read the link about the ACR. Sounds interesting. I am wondering though - As it senses a charge to the house bank ( I presume from the shore / AC charger, or alternator) it then closes the realy and alows the start battery to be charged as well.
How efficiently owuld this charge the house bank, when instead of charging two group 27 batteries (house bank) you are now charging two group 27s and the group 24 start battery (smaller capacity).

Could this not somehow reduce the amps able to be delivered to the house bank?