Protecting sensitive engine wiring while charging 24 volt trolling bank

[southpawguide]

I recently installed a new mercruiser 5.0 engine and would like to charge my 24 volt trolling bank with the 12 volt alternator. I bought the BEP Marine voltage sensitive relay for that purpose, but my mechanic is concerned about the ignition wire on it interferring with the voltage sensitive engine electronics. How can I protect those electronics?

 

[Silvertip]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

Better think this through a little more. Your mechanic gave you good advice. A VSR uses a COMMON grounding system between batteries and battery banks. Therefore you cannot charge a 24 volts system from a device designed for common 12 volt grounds. 24 volt trolling battery banks do NOT have a common ground at the batteries -- they are in SERIES -- not PARALLEL. The only way you can accomplish this is to install a switch that switches the batteries from their series connection and reconnecting them in the parallel configuration. THEN and ACR/VSR can be used with one leg feeding the START battery and the other feeding the TROLLER bank. You then switch from series to parallel when the engine is running to charge the troller bank. You switch back to series and DISCONNECT the troller side of the VSR when using the troller Study that LAST statement VERY carefully.

 

[glenn property of pam]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

3 batteries total? one starting 12vdc and 2 in series for trolling 24vdc? maybe a second alternator running at 24vdc would be a option to read about

 

[Jlawsen]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

3 batteries total? one starting 12vdc and 2 in series for trolling 24vdc? maybe a second alternator running at 24vdc would be a option to read about

This is the correct and most commonly used solution.

 

[Silvertip]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

A 24 volt alternator is a viable solution if you have $100 - $250 to devote to the project plus the cost of the installation.

 

[southpawguide]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

Thank you all for your input. I also fired off an email to the tech rep at BEP Marine and the following is his reply.

Hello Jim,

I have to assume that the VSR you are using in this application is a 710-TBVSR? If that is the case then you have a 12V alternator on the engine and so the 710-TBVSR 'flip-flops' across its relays to alternately charge each of the 12v batteries in your 24v trolling bank?

There really is no risk to the vessels electronics from the 71-TBVSR. In the simplest sense the TBVSR is paralleling the start battery with the trolling bank batteries, each in turn, to charge them when the engine is running.

The red wire to be connected to the ignition outputs nothing but receives a voltage level signal that is used to tell the TBVSR when the alternator is running and so to begin charging. Also when the engine is shut down and the alternator is not charging the boats voltage will drop to the batteries rest voltage and the TBVSR will cease charging the trolling bank.

I hope this allays any concerns you might have.

Regards
Marcus

The wiring diagram supplied with the switch shows the input leads connected to the start batteries and the output leads to each of the trolling bank batteries through 70 amp fuses. The final wire is a small red wire that is connected to the ignition switch. That wire is the one my mechanic is so concerned about. Could any of you take a look at the diagram (posted on the BEP site) and tell me if you agree or disagree with the tech rep assessment?

Thank you

 

[Scott Danforth]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

they make an on-board charger that is 12 volts / 40 amps in, 24 volts / 20 amps out. Promariner makes it.

http://www.iboats.com/ProMariner-Di...8105852--session_id.902359930--view_id.522326

here is the manufacturers page for the specs: http://www.pmariner.com/productFeature.php?ProductNum=05505&page=2

 

[Silvertip]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

they make an on-board charger that is 12 volts / 40 amps in, 24 volts / 20 amps out. Promariner makes it.

http://www.iboats.com/ProMariner-Di...8105852--session_id.902359930--view_id.522326



here is the manufacturers page for the specs: http://www.pmariner.com/productFeature.php?ProductNum=05505&page=2

An on -board charger does nothing for you when underway. The OP wants to charge the troller batteries from the engine.

 

[Scott Danforth]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

Silvertip, its a DC to DC converter. it takes alternator current, in this case 12 volts / 40 amps, to charge the 24 volt battery bank at 20 amps. and it will only work when underway.

 

[southpawguide]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

Silvertip,
I just reread your original post. The 12 and 24 volt grounds are not common in this instance. The 24 volt ground is confined to the trolling circuit. The two 12 volt batteries are connected in series to the trolling motor controller with both positive and negative leads and there is no ground connection with the engine circuit. Do you think it is still risky if the grounds are kept seperate?
The 12 to 24 volt onboard charger is an expensive alternative. My mechanic has also suggested an inverter to supply 110AC current to the three bank charger already installed on the boat. I just thought the BEP relay was a more direct solution.

 

[Silvertip]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

That is correct. And because they are separate is the reason you cannot charge the troller system from the alternator. Current needs to have a ground path back to the alternator. Each battery also needs a positive connection to the alternator to charge that battery. The very moment you create a ground path between the battery on the right and the engine ground you create a huge electrical problem. Can you say "ARC WELDER". You CANNOT charge a 24 volt system from a 12 volt engine alternator. The reason you can charge two, three or four batteries with a two, three, or four bank on-board charger is that each of the grounds is isolated from the others so there is no shorting involved. You have four totally separate chargers in one housing. Your engine alternator requires a ground -- period. To charge anything from it also requires a ground path back to the alternator. I try to educate in my responses so if this sounds a little terse it is for your education, not that I'm trying to belittle you. Here is a diagram of your troller and engine electrical systems. You can draw the lines on how you THINK this could work. Tell us how you intend to do it, or mark the diagram and I will show you how it will cause smoke and fire.

 

[southpawguide]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

Silvertip,
The attachment is the wiring diagram supplied with the BEP relay.

 

[Silvertip]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

Your original intent was to NOT use any switching devices or on-board chargers which ARE necessry to do what you want to do. I missed your change in direction so have it with the device you show. My point then to others is that you cannot simply connect wires from the start charging circuit to the 24 volt system without some sort of switching system to break the 24 volt series connection on the troller bank.

 

[glenn property of pam]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

thats a intresting relay can i ask what it cost?

 

[southpawguide]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

My original intent was to ask if the sensitive wiring on the new engine was properly protected using the BEP trolling relay.
Glenn,
I just did a google search for the switch. It is available through some marine suppliers for $308.

 

[glenn property of pam]

Re: Protecting sensitive engine wiring while charging 24 volt trolling bank

i dont see any problems with the wiring or sensors on the engine. you might get a hummm on the radio as the relay is opening and closing rapidly but most people are now using cd or usb so thats proberly a mute point. i think its a neat idea but the cost of 350 installed (fuses etc) puts a dampner on it. i like stupied simple things so i have to wonder do you troll enoght to need charging while motoring (silver has the numbers based on alternator amps over motoring time and thats if the engine is running at rpm not at low rpm no wake speed). if you had a outboard then the relay looks like a great solution with a inboard it looks like the second best idea with the additional 24v alt being a better idea as it can charge faster and its simple once installed