PSA: Check your battery paralleling solenoid

[P-Dogg]

For 8 years I have been using deep cycle batteries as starting batteries on my Crusader 270s. I put in new batteries last year (in year 7 -- calling that a win, but maybe they would have lasted even longer -- read on), and again this year. WTH?

I had previously checked that the battery paralleling solenoid was activating during either engine start -- its audible clunk is hard to miss. However, after getting 1 year out of my batteries I decided to put a meter across the switched terminals to double check -- nothing! Thus, only one deep cycle battery was supplying starting current for the engine start. I have proven that two deep cycle batteries will work to start my small blocks (don't try this on a diesel....), but that one deep cycle battery will not (group 31s).

All types of batteries will last longer if the current draw is reduced, so I advise everyone to put a meter on their OEM battery paralleling solenoid to ensure that it is actually working.

[prowlersfish]

Good info ,Volts or Ohm? What reading were you looking for? I have a quick test of the solenoid, With the bat charger off both engines switches on not running. Watch the voltmeters on the dash to see if both drop. Next with the one engine running (the other switch still on) hit the emergency switch and see if the voltage goes up on the non-running engine. This only works if the alternator is good and charging of course.

[P-Dogg]

New relay reads 0.2 Ohm across switched contacts when closed. Old one was mega ohms when closed.

[mrrudely]

this is a very timely post for me
having just solved an intermittent starting problem (corroded terminal connection)
while troubleshooting the problem I suspected the paralleling solenoid
still not understanding this 100% I have some questions

1) when at rest there is continuity between the battery cables why?
2) there are two small terminals with only one having a wire connected what is the second terminal for?
3) is this supposed to connect the two batteries together everytime either engine is started? if so how do I check this?
also I understand the button at the dash, but if it does connect both automatically how does it do that? (I have very limited electrical knowledge)
4) I assume the power to operate the solenoid comes from the batteries, how dead does one battery have to be before requiring
the emergency start button?
5) I don't think it is the original, if it needs replacement does anyone have a part number?

[mrrudely]

I may have found the answer to number 3 in a previous post titled
Trojan's unique starting parallel system
by RWS 1/31/21

[P-Dogg]

1) when at rest there is continuity between the battery cables why?
2) there are two small terminals with only one having a wire connected what is the second terminal for?
3) is this supposed to connect the two batteries together everytime either engine is started? if so how do I check this?
also I understand the button at the dash, but if it does connect both automatically how does it do that? (I have very limited electrical knowledge)
4) I assume the power to operate the solenoid comes from the batteries, how dead does one battery have to be before requiring
the emergency start button?
5) I don't think it is the original, if it needs replacement does anyone have a part number?

1). No
2). Same here. Mine was grounded through the mounting flange. Only 1 wire connected to the little terminals.
3a). Yes, plus whenever you operate the "emergency start" switch (more useful for getting maximum voltage if the need to use the radio while in distress).
3b). Remove one of the wires from the big terminal. Have a helper crank each engine while you measure the resistance across the big terminals. Alternatively, remove one big wire, then measure the voltage from the now-empty stud to ground while helper cranks. It should be very near battery voltage. Replace the big wire, then do the same for the other big terminal. The point is, verify that the contact is closing, and that power is getting from one big terminal to the other when each engine is cranked.
3c). Mine is two-position. IIRC, one way powers the contactor from one starting battery, the other way from the other starting battery.
4). Dead enough? If the contactor is working, no user intervention is required. If one engine won't start, start the other one. Move throttle above idle so that the alternator is putting out juice, wait a few minutes for the charge consumed during that engine start to be replenished (so that the one alternator in use is not trying to charge two batteries when the second engine is cranked), then use the emergency switch while starting the second engine -- try both positions. You can also charge the dead battery by holding down the emergency start switch while one alternator is working. Holding the switch down allows current to flow across the contactor to the dead battery. You'll need to find out in advance which switch position supplies power to the contactor from which engine.
5). I bought but have not yet tried this: https://smile.amazon.com/gp/product/B07 ... UTF8&psc=1

If you do not have a manual, Beacon Marine can sell you one. I also recommend Nigel Calder's Boatowners Mechanical and Electrical Handbook if it is not already on your nightstand.

[prowlersfish]

this is a very timely post for me
having just solved an intermittent starting problem (corroded terminal connection)
while troubleshooting the problem I suspected the paralleling solenoid
still not understanding this 100% I have some questions

1) when at rest there is continuity between the battery cables why?
2) there are two small terminals with only one having a wire connected what is the second terminal for?
3) is this supposed to connect the two batteries together everytime either engine is started? if so how do I check this?
also I understand the button at the dash, but if it does connect both automatically how does it do that? (I have very limited electrical knowledge)
4) I assume the power to operate the solenoid comes from the batteries, how dead does one battery have to be before requiring the emergency start button?
5) I don't think it is the original, if it needs replacement does anyone have a part number?

# 1) should not be unless your battery switch is on all. How are you checking this?
#2) The solenoids are used in different applications Also while looking at them they can look the same but internal wiring is different. Some are wired so the extra terminal is 12 volts when the solenoid is on, they are normally used as starter relays. Some are wired so that is the ground instead of the bracket.
#4) when its too low to start the voltage is too low to turn the solenoid on through the diode.

[mrrudely]

can't thank you guys enough for all your help

I checked everything today and it seems everything is in working order

I have two starting batteries and one deep cycle battery
there are two breakers in the battery box powered by the starting batteries sharing terminals with the solenoid
I was thinking I could set up the deep cycle battery as the house battery and leave the starting batteries dedicated to just that
Anyone see that as a bad idea? if not can I just have the one deep cycle energize the two breakers
Also can I have the alternators charge the deep cycle? or is that already happening?
there is an inverter connected to the deep cycle as well as the anchor windlass
the generator is started by one of the starting batteries