Installing a second battery - Maxum Boat Owners Club

Danny · 05-01-2010, 01:41 AM

If I install a second battery on my 2001 1800 sr, can I just wire them in parallel? Will this affect the battery charging system?

ed & inge · 05-01-2010, 10:00 AM

the question is;

do you want more power, or do you want a spare battery.

the best is to install a battery clock with the positions; off - battery 1 - battery 2 - both... connect batterys with enough power/amps on the clock....when you leave your boat alone in the harbor put the clock on the off position (then you have no power loss, the boat is complete unpowered) when your going for a trip put the clock on battery one.....all the power you use at the boat (radio, portable fridge or what ever) is taken from battery one....if the boat wo'nt start at the end off the day, you put the clock to position battery 2, and then you have the power to start the boat and get home.....with a battery clock it does'nt matter if the clock is in position 1 - 2 - both......both batterys will be charched wile engine is running

if you just connect the batterys to each other, you have a lot of power, but........ empty is empty (below a voltage of 11.5/12.0 your boat will not start anymore) and then you wont come home at the end of the day (could be fun too of course)

succes from a rainy and very wet netherlands at the moment, ed

ss3964spd · 05-02-2010, 06:56 PM

What Ed said.

Best option is to install an off/1/2/both type battery switch (clock) so that you can select the battery you wish to use. For instance - and assuming both are fully charged; select battery 1 for starting the engine and running to where ever you are going. Then, if you'll be there a while and want to use stereo, etc, shut down the engine and then select battery 2. You can then run everything off batt 2 for as long as it lasts. Time to leave? Switch back to batt 1 and start the engine.

Slight correction though, If the batt switch you install does not have a built in charging circuit, and if you don't have a combiner, the alternator will not charge both batts at the same time unless the switch is set to "both". In other words, if the switch is set to "1", batt #2 will not get charged, if set to "2" batt 1 won't get charged. So, with the scenario above, once you re-start on batt 1 then simply switch to "both" so both get charged.

Companies make switches that will charge which ever batt needs to be charged regardless of the switch position, but that requires that you wire the alternator's charging output feed to the battery switch. On my '04 2400 SC3 the alt charging lead goes into the wire harness and terminates at the starter - and it's NOT easy to get to the starter to disconnect that lead and re-route it to the switch. I could have just cut the lead before it went into the harness but I hate cut/dangling/un-terminate wires so I didn't.

One other thing. If you leave your boat in the water DO NOT leave the switch in the off position. The bilge pump won't work (unless you wire it directly to the battery).

Dan

ed & inge · 05-02-2010, 07:18 PM

Quote:

Originally Posted by ss3964spd

What Ed said.

Slight correction though, If the batt switch you install does not have a built in charging circuit, and if you don't have a combiner, the alternator will not charge both batts at the same time unless the switch is set to "both". In other words, if the switch is set to "1", batt #2 will not get charged, if set to "2" batt 1 won't get charged. So, with the scenario above, once you re-start on batt 1 then simply switch to "both" so both get charged.

One other thing. If you leave your boat in the water DO NOT leave the switch in the off position. The bilge pump won't work (unless you wire it directly to the battery).

Dan

yes dan, your correction is right, i had a combiner on my 2855, but on the 2400sc3 we own now i have to select............

about the other thing.......the water in our harbour is only about 3 feet deep so i still can see her lying when she has sunk........(whouaaaaaaah)

tex'npepper · 05-03-2010, 06:44 PM

I always start and run my boat on both. I then switch to the house battery if I shut down away from my dock. By the way, the bilge pump should always be hooked directly to one of the batteries with it's own fuse just in case someone turns both batteries off.