Dual battery charging
Printed From: The Fishing Website
Category: General Forums
Forum Name: The Boat Shed
Forum Description: Discuss all things boating.
URL: https://www.fishing.net.nz/forum/forum_posts.asp?TID=102884
Printed Date: 01 Jun 2026 at 6:23am
Topic: Dual battery charging
Posted By: 3rnzir
Subject: Dual battery charging
Date Posted: 04 Aug 2014 at 5:51pm
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I have a blue seas battery isolator/switch that is linked to an ACR. What position should the battery switch be in/on(OFF,1 starter batt,2 combined batts)for charging both batts at once/together? ACR always makes sure stater batt is at full charge then surplus charge is feed to the house batt then switches back and forth between the two batts whilst motor is running. Have just hooked up a easy connect plug in that fits both sets of batt posts. Once I have this nutted out,I hope to just leave batt charger in/on for a maintenance/float condition. Cheerz ------------- Peace.Via superior firepower.. |
Replies:
Posted By: Reel Deal
Date Posted: 04 Aug 2014 at 7:12pm
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I have similar - I start on first battery then turn to both battery for the trip out which charges both. Then turn back onto one when parked up so I always have a full charge battery if the first starts to get low. Don't know if that's how I'm supposed to work it so also keen to hear what others do. Only run UHF fishfinder GPS and live bait tank. First battery hasn't gone flat yet..... ------------- The gods do not subtract from the allotted span of men's lives the hours spent on fishing - Assyrian Proverb |
Posted By: T-Time
Date Posted: 04 Aug 2014 at 8:18pm
| I have this same system and run 3 batteries. I only have it on "1" and the ACR charges all three. When I bought the boat I queried the same from owner and seems to be fine this way. I'm no expert but starter battery always get first charge and then other batteries follow afterwards. |
Posted By: 3rnzir
Date Posted: 04 Aug 2014 at 8:34pm
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Will try "1" setting then TTime. Thanx cobber. ------------- Peace.Via superior firepower.. |
Posted By: Steps
Date Posted: 05 Aug 2014 at 9:23am
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Little different.. smaller scale. We have 1 main battery...like any ave day boat. But always carry a spare jump battery unit. When staying out over night I turn off the battery isolating switch to the main battery. Plug the cig lighter accessory off the portable jumper unit into the cig lighter on the dash. This then runs the lights, gps/ sounder, radio, and rear deck lights for fishing, overnight. The cabin internal lights are dual fluorescence, the rest are led. Next morning, I turn on the main battery, then disconnect the cig accessory plug, fire up the engine , then plug the cig connection back in.....the engine now recharges both batteries. Do not start the engine with just the cig plugged in and main not turned on... the starter is a huge current draw and blows the cig circuit fuse. I have not tried with main battery and jumper connected thru cig to see what happens....Dont need any future hassle of a weakened fuse blowing , as per murphys law at the worst time. The switching of a duel battery setup I would imagine to be similar... If u have a duel setup and 1 battery is getting low from over night... and would most properly have to be too low to run a gps/ sounder (???) if turning both on to fire up, dont mess around before firing up.... when flat and charged battery are hooked together they will balance out their charge.. but one the engine alternator is running it will recharge both... And a side note on charging batteries.. many types of chargers will not chargea battey below as set voltage, arounf 9/10v.. they are programed to assume the battery is a dud. To get around this , start charging a good battery, and while that charging, them put jumper leads to the dud battery... the charging voltage stays high, wait for a couple minutes and disconnect the good battery if charged....will carry on charging the low battery nps. |
Posted By: Reel Deal
Date Posted: 05 Aug 2014 at 9:24am
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Why does it give you the other battery options? Why not just give 1st battery as turning to the 1st charges all batterys and draws from all. Why would you turn to 2nd or 3rd battery for? Does that only use the 2nd or 3rd battery and isolates the 1st? ------------- The gods do not subtract from the allotted span of men's lives the hours spent on fishing - Assyrian Proverb |
Posted By: 3rnzir
Date Posted: 05 Aug 2014 at 11:26am
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Reel Deal. With my batt isolator/switch it goes something like this with the twin batt setup. OFF= islolated both batts. 1 = power from starter or #1 batt. 2 = combine power from both batts to feed #1 batt to turn over motor(emergency backup) ACR senses current from alternator,tops up Batt 1 first the feeds excess current to Batt 2. At rest using electronics, ACR draws down power on Batt 2(house batt) first. ACR starts flashing when voltage gets low on Batt 2 at rest so skipper knows to power up boat. This should still have a full charge in Batt 1. Still need to be able to see the small led flashing to warn you though. Make sense? Cheerz ------------- Peace.Via superior firepower.. |
Posted By: Reel Deal
Date Posted: 05 Aug 2014 at 1:19pm
Cheers 3rnzir. Sounds a good system. How different it is from mine I'm not sure. I don't have a light to flash. Not too big a issue as its been working fine for past 5 years but good to know I am doing it right or not  ------------- The gods do not subtract from the allotted span of men's lives the hours spent on fishing - Assyrian Proverb |
Posted By: widerange
Date Posted: 05 Aug 2014 at 1:31pm
| what is an ACR? |
Posted By: MikeAqua
Date Posted: 05 Aug 2014 at 2:01pm
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As I understand OP the intention is to use a single battery charger to keep two batteries topped up? I would only consider this if the batteries are set up as bank i.e. identical batteries connected, charged and used together. If you have separate batteries that can be connected in parallel by a switch then I think you will have difficulty getting them both to charge correctly with any sort of 'smart' charger. It will see them as a single battery and manage the charge accordingly and you may get uneven charging. If it was me I would get a charger for each battery, or a two battery charger (if such a thing exists) and charge them separately. |
Posted By: Tonto2
Date Posted: 05 Aug 2014 at 3:06pm
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BEP do a VSR (VOLTAGE SENSITIVE RELAY), the idea is that when the start battery has reached charge the current from the alternator is then sent to top up the second battery, it is a good system provided you have a big enough alternator. Some outboards like mine only have a 7 amp alternator and it is a struggle. Just hook the smart charger to the start battery. ------------- slowly going where everyone else has already been |
Posted By: Steps
Date Posted: 05 Aug 2014 at 5:30pm
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If you have 2 different batteries in parallel of the same voltage and type (eg lead acid) it doesnt matter and also doesnt matter if at different charge levels.. (See my post above) The charger will supply each battery as required according to the internal resistance of each until each match the cut off requirement of the charger ie if 1 is fully charged it will no longer draw current and the other will draw till it also is charged Now if those batteries where say 6V on a 12v charger in series , very different kettle of fish as all current has to be drawn thu both batterys...so if one is still not charge it will stil draw the current thru the charged one to get charged (not strictly correct , u get the concept?) |
Posted By: Kandrew
Date Posted: 05 Aug 2014 at 8:26pm
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A VSR works like this, you have 2 batteries, With your 3 way switch you select 1 battery to run from while sitting at anchor so the other battery stays charged if you need it to start. When the engine starts and the voltage gets to a level the VSR joins both batteries together so both are charged. When the engine is turned off the voltage drops down under the level the VSR drops and disconnects the 2 batteries from each other. You are left drawing from the battery you have switched on. In larger boats you can run a deep cycle house battery for running off at anchor and a high discharge starting battery for starting. In my boat I run 2 normal marine starting batteries, I run out fishing on one battery and leave that one switched on to run lights and electronics while I'm anchored then I switch over to the other battery when I head home. If needed I can join both batteries together with my battery switch if I need the extra crank. Have never needed to because I use a ctek charger at home. This is a pretty standard setup. |
Posted By: 3rnzir
Date Posted: 06 Aug 2014 at 8:06am
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AquaMike. Yes,2 x 1000 CCA 130AHs LiFePo4 batts. Had to buy a CTek Lithium XS charger (different algorithms to a lead acid charger) Will try setting the Iso/switch to the #1 setting(same setting as regular OB running). Then will place charger on #1 batt,and record volts/charge on batt #2 with multimeter to see if batt # 2 is being topped up. Works fine on that setting for both batts via the OB alternator (Opti 65 amp output) After a float charge when boat is in the shed for those weeks I cant get out during winter. Will keep Y`all posted on outcome. Cheerz ------------- Peace.Via superior firepower.. |
Posted By: Kandrew
Date Posted: 06 Aug 2014 at 6:58pm
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As long as the voltage meets the right voltage level the VSR will kick in and charge both batteries. I don't do this on my tinny, don't like the battery being left on. I turn the battery switch to off and just change the battery charger over to the other battery every couple of weeks. Use the Ctek battery indicators the ones with the three LEDs on both batteries. They are really good and let you know where the charge of your battery is at a glance. Also a quick way to plug the charger. Interesting comment about the different algorithm, never had that problem with the batteries you use. |
Posted By: Taking Time
Date Posted: 07 Aug 2014 at 4:57pm
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I've got a similar question, I want to set up a solar panel to keep my batteries topped up while not in use. I was thinking of using a 10W solar panel and a solar regulator to keep from over charging/draining etc and like Kandrew I don't want to leave the battery switches left on. I have two questions, 1. Sould I use 1 regulator with connections to each battery to keep them seperated, or use 2. 2. If using two regulators, is it fine to run them off the 1 solar panel. If anyone knows the answers that would be great. cheers
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Posted By: Tagit
Date Posted: 07 Aug 2014 at 5:11pm
| There are proper dual battery solar regulators. That is what you need. Connecting a single output regulator to both batteries is like wiring the two batteries together. |
Posted By: 3rnzir
Date Posted: 07 Aug 2014 at 5:18pm
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LBG Matt. Looked at this option myself before my batts went flat,hence the CTek purchase. With the solar option I found a NZ kayak website that explained this option. The regulator or MTTP was a Genasun GV5 model the solar panel was a flexible unit from some ChCh outfit. The flexi solar panel can tie/fix onto your boat somewhere if venturing away from a mains power supply on say a long weekend fishing mission. Then place the panel on the side of your shed that gets some sunshine time at home. Keeps boat batts on a float setting/charge. Looked like a good set up. Costs around $350 all up. Not too bad for a portable unit I guess. Cheerz ------------- Peace.Via superior firepower.. |
Posted By: Kandrew
Date Posted: 07 Aug 2014 at 7:36pm
| Im not a big fan of sola panels, you need to have a very high quality unit to have something that will be trouble free for a long period. Good ones don't come cheap and add the cost of the regulator and your up for some real money. You cant beat the Ctek units to keep your battey in good condition. |
Posted By: 3rnzir
Date Posted: 07 Aug 2014 at 7:38pm
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Both batts seem to be at full charge @ 14.4v. batt iso/switch is set to the OFF position. Multimeter have both batts equalised. Charging via a CTek comfort connector on batt 1. Will check again tomorrow at some stage. Cheerz ------------- Peace.Via superior firepower.. |